BD-4 NEWSLETTER #17
Roger D. Mellema
17605 SE 288 PI.
Kent, We 98042
Well, the flying summer is about over - for those of you who have been, flying. The only flying I have done is a one hour ride over Seattle at night and that wasn't even in a BD-4. The V-6 is still sitting in the corner as I am waiting for the Blanton reduction drive (I am getting the extended propeller shaft model).
After all the company we have had this summer, I swear to never have a 25th wedding anniversary again!
The really good news is that we finally moved from the "music room" in the hangar to the new house which is 15 feet away. We now have trouble finding each other!
It had to happen sooner or later and here
it is! I haven't asked for money for a long
time as there have been so many people wanting
back issues of all the newsletters that money
has been flowing in at a rate that has kept
us in the black. In the past, I have made
a good number of extra copies of each newsletter
just for this purpose. Now I am all out of
back issues (they are still available, I
just have to go down and make copies) and
the money is down to where this issue will
wipe out most of it. If you have any symbol before your name on
the malting label except for a " + ".
you owe $5.00. You see some people send money even if I
don't ask for it and they already have credit,
thus the + .
MEMORIAL DAY FLY-IN
The regular Memorial Day (May 28, 1990) fly-in will occur at the Mellema house. We will eat at about 3 PM and as usual it will be pot-luck. We will have the grill hot in case you want to cook your own meat. Be ready for some serious volleyball!
We really need some flying BD's there this year. I believe we once had 4 airplanes there but the last couple of years only Steve Mahoney has been available to give rides.
If anyone needs to arrive the night before or needs to stay Monday night, just call and we will work something out.
I have had several requests for windshields. I will wait until May 5, 1990 for more orders. The cost is about $230 + $30 crate + shipping (COD).
I recently visited ATACS Products, 1120 SW 16 th ST, Renton, WA 98055 PH 206-226-8340, to buy some Pro Seal and found a great new product. The material Bede supplied to seal the windshield was a putty that never got hard and never lost it's stickiness. After all the trouble I have had with using other products, I think a substance like that is what is needed. The new product I saw demonstrated is called Seal-Once. It is made by INRI, Inc. (International New Roofing Industries). This polycarbonate material can seal through water or oil film and can be used to seal lead, asphalt, stone, ceramic, concrete, plaster, and all solid surfaces. It stays sealed from -30 to +220 degrees F and will stretch 350 % without breaking seal. Very good for high vibration and expansion areas. After 10 years it will still be flexible. In playing with the test samples, I found out that if the bonded surfaces are pulled apart and then pressed back together, the tear is healed back to the original strength. The cost of the material is about $6.00 per 10 ounce caulking tube, and comes in a variety of colors.
Fulvio Manetti, 3421 E Tropicana # E, Las Vegas, NV 90121 has lost his partner and wishes to sell his BD. It is 80 percent completed with both gear options available. All the parts needed for completion are included. The wings only need to be fitted to the fuselage, it has basic instruments, an O320-B2B Lycoming engine with 350 hours since major (with logs and compression of 79/80 for all except one cylinder) Asking price is $10,500. Phone 702-458-6911 office and 702-383-8141 residence.
John Dornos, phone 206-941-1597, has the following items for sale: Wing spars, original fiberglass cowling, stabilator tips, rudder horn, control sticks and linkage, large plans, new main gear box and cover, landing gear weldments. John also has a complete airframe (was flying) for sale. It is a tri-gear with large vertical fin, never painted deluxe interior (not installed), no instruments, wings with the good Panel-Ribs (TM) installed and covered with a layer of fiberglass.
Gary Kvaltine, 8167A Alpine Ave, Sacramento, CA, 95826, PH 916-452-9612 has his project for sale. $6200
Jim Huber (PH 206-772-4013) bought American Yankee ribs for his metal wing the then had a local company spin the flanges needed to connect the ribs to the spar. They are beautifully made and heat treated. Call Jim if you are interested in getting some made.
Charles Oliver, 2664 Country Club Dr., Glendora, CA 91740 PH 714-593-7665 has his BD for sale. This airplane was set up for the Olds 215 Cu In V-8 and has an 18 inch fuselage extension. It has a Jim Murphy wing, is a taildragger and is set up with no flaps or, ailerons or flaps (roll by spoilers). It can be seen at Brackett Airport, hangar D-8 PH 714-593-7665.
Robert Scott, 711 South St., Yreka, CA 96097 PH 916-842-3054 has his BD for sale. It has the following: O360 with 635 hours, Hartzell constant speed prop, tri-gear, 8" nosewheel, fiberglass wings, 42 gallons, 135 hours airframe, gyros, KX 170B, AT150, EGT. $15,000 firm.
John Spears, 299 Logan Hill Rd., Chehalis, WA 98532 (748-6828) has his BD for sale. Basically done but no engine. He lost one of the doors in a recent flood.
Robert Bollinger (5000 14th St NW, Washington, DC, 20011) has a set of BD main landing gear for sale. They have had a positive arch put in them to keep them from sagging. $200.00
Dave Blanton of Javelin Aircraft called to talk about BD-4's and Ford V6 engines. He is interested in making the electronic throttle body injection work for airplanes and also trying the Ellison Throttle Body Injector. There are about 35 people that have said they plan to use the V6 for the BD-4.
Fred Hinsch now has his hours flown off of his BD-4 (1-19-89). He has had some hard luck getting his BD flying. First he had a lot of trouble getting the carburetor to work right and had to have it rebuilt. He said it still runs rich enough that he has to lean for take-off at sea level. He has a 150 Lyc and a Marvel-Scheibler carb. Once he got it flying, he had a fiberglass spinner come off in flight and take off some of his prop. He did a little damage in the emergency landing. After all this a run-away plane chewed up his tail and wing! Fred has been having trouble with weak brakes. He finally put Cessna master cylinders (instead of Gerdes) on with his Cleveland wheel system (relined with metal linings) and now enjoys fantastic brakes! Fred says that a good source of rivets is the Zenair Company, Midland, Ontario. 705-526-2871. They have the original type Avex rivets supplied by Bede. L4R4K8 (1/8 " CS) go for $88 per 1000.
Bud Stearns has flown his BD-4 for the first time on Oct 20, 1987 and wrote to let us know how it went. He thought the rudder was very sensitive after man-handling a C-130 Herc. It sounds like he had more bad luck than usual as he had to overhaul the mags, the harness, the prop governor, the starter, the battery relay, the brakes, and the voltage regulator. During the 25th hour of flight he had to replace the battery relay again, a push to test switch and a blown oil cooler. He landed with only 3 quarts of oil left. 'Since then he only had to replace the prop shaft seal, beef up the tailwheel structure, shim the axles to get the wheels vertical again, and redo the front seat backrest stops. He now is lubricating the fuel selector with never-seize and replacing the 'O' ring. He has 110 hours on it at this time.
The performance figures are as follows: stall with full flaps is 65 mph, stall clean is 70 mph, 165 mph at 75% (lots of antennas, and 800 x 6 tires), 1205 lbs empty (1/4 inch cork lining the entire inside back aft of the baggage compartment and full interior), empty CG is at' 83 inches (38 lb battery on the firewall). With 72 gallons of gas he is limited to 200 lbs in the rear seat.
Bud plans for 150 kts cross country and that seems to come out about right. He plans some IFR work as he just got it certified for that.
I just received word that Bud died in the crash of his BD-4 along the California coast. He took off on a non-stop flight from San Luis Obispo; CA to Corvallis OR and was reported missing when his flight plan time ran out. The wreckage was not found for several days. The BD had flown in a level path at full speed right into a 1000 ft high ridge along the shoreline. The NTSB indicated that the airplane was not at fault. There was some cloudiness along the shore at the time of the accident but should not have been a factor. It was almost as if he had the auto-pilot on and fell asleep. Steve Mahoney, Colin Powers and other pilots performed a fly-over during the memorial services.
We offer our sincere condolences to family and friends
Bill Bunting sent an idea for getting roll trim. He saw this done on Bill Bullock's airplane (Scottsdale, AZ). The general method is to split the flap bar on the left side of where the flap handle connects to it so that the left flap can be adjusted up or down a little by turning a knob.
John Bracher is working some on the BD-10 project. Maybe he will share some of the inside information? John would like a copy of one of the video's taken during the BD-4 banquet at Oshkosh 88. He will even pay you for a copy.
If you will remember, I recently covered the header tank system that John installed in, his BD before the FAA would let him fly. On the way home from Oshkosh he had a sudden , engine stoppage at altitude and found that with the selector in the both' position, only the right tank was feeding. He backtracked to Debukue, IA and filled the totally dry right tank. He then flew on just the left and it fed alright. When he switched to 'both' again only the right one fed. After getting home he found that the left fuel vent was plugged. He is thankful for having a cross vent between the two tanks.
Stan Wilkins wrote to say that he has not had trouble with his per plans fuel system but is very careful to not take-off with less than 10 gallons of fuel in a tank. After totally draining the fuel system, he has to blow on the fuel filler hole to get the lines running good again. Stan has a desire to try putting the Ford SHO engine in a BD. It is supposed to put out 250 HP.
Martin Steele from Blenheim, New Zealand is fitting the controls into the fuselage and has the wing ribs made but badly needs a set of spars. Martin says that Trevor Ancell's BD-4 has not been worked on in a while but maybe will get dusted off soon again. Martin may be interested in a built-up spar such as a box or 'I' beam but would rather have the round type.
One of the most venerable BD-4's (14 years and 820 hours) still has trouble with leaky wing tanks. Colin Powers has many years on his BD but has been struggling with the wing , tanks all the time. He has cut 6 x 12 inch holes in the top and bottom, cleaned everything from around the spar, resealed, and resloshed. In six months the leaks started again. He said that the original 3M 2216 wing bonding epoxy had softened substantially from contact with fuel. He is now doing a major rebuild on the left fuel tank (he says it really hurts to take a saw to the wing!).
The area directly under the spar of the fuel cell is generally resin rich in all the cells he has had. This makes it prone to cracking during flexation which occurs when you fill the tank with gas. His tanks bow from cell seam to cell seam by as couch as 3/16 inch when completely full. He would like to buy some of the better Panel Ribs so he could remake the tank area.
Colin plans to reinforce the lower side of the panel so that it does not flex as much and then to put everything together with ProSeal.
Barry Smith, 15 Cooba Way, West Lakes, South Australia, Australia 5021, is a new addition to the BD family by way of that great article in Kitplanes. He had the misfortune of hitting a wind shear in 1985 and ripping off his nosegear. He made a go around, was waved off, and then flew to another airport to make an emergency landing. No one was hurt and the BD ended up with it's nose (and bent prop) right on the centerline of the runway. Barry is now looking for a replacement prop. The engine is the Lycoming O-360, and the prop is a Hartzell HC-C2YK-1BF with the F7666A-2 blades. Barry is looking for a serviceable used prop.
I received a phone call from Scott DeGaynor the other day and he has yet another solution to the gas flow "problem" that some people have experienced with their BD's. He is installing a 5 gallon tank in the baggage area that is totally isolated from the all other fuel sources. This tank will have it's own gascolator and an electric pump. When he opens the valve to use this gas, a micro-switch will turn on the pump. The gas will be routed to a "T" fitting right at the carburetor. There will be a check valve in the line that comes from the regular gascolator so that this fuel will not be pumped back into the wing tanks. The reason for not connecting to the main tanks so that the aux tank can be refilled from them is the problem of fuel contamination. Scott will be extremely careful to make sure the fuel in the aux tank is clean.
Scott has been having some trouble with the braking system on his BD-4. When returning from the BD-4 fly-out during Oshkosh '88, the airplane pulled hard to one side during landing. Scott thought the crosswind was worse than it should have been but sort of ignored it. A bystander signaled to him that he should shut down and pointed to the wheel. The brake had been dragging and had gotten so hot that the brake line melted and a small fire started. Scott kicked through the wheel pants and used' his fire extinguisher to put the fire out. It turned out that one of the Gerdes "parking brake" levers had accidentally latched and kept the brake dragging. I had the same problem one time when I kicked hard right rudder to break the tailwheel loose into full swivel. I almost ended up on my nose and did sustain some prop damage. As the plane started to go over, I hit the throttle hard to get some air over my stabilator. I got the tail back down but did have to file and balance the prop. Personally, I would recommend that everyone take off this parking brake lever and use some other method of getting parking brakes. One of the best ways is to use the "hydraulic lock" type of parking brake as used by Piper aircraft and others. These can be obtained quite cheaply at the Fly-market at Oshkosh.
Scott has also recently had the top break off of the plunger shaft on one of his Gerdes master cylinders. The threaded yoke on the top of the shaft was apparently hitting part of the actuating belcrank on the rudder pedal. This caused the plunger shaft to bend some when the brakes were put on hard. The shaft broke just below the yoke. It would be a good idea to check your airplanes to make sure this can't happen. If the yoke is close to hitting, take a round file and file away some of the aluminum on the rudder pedal brake belcrank.
Henry Imhof visited here recently to pick up a curved windshield. He has a novel way of installing individually adjustable seats in his BD. He used extruded, square aluminum tube and bolted one piece horizontally along each side channel and two more bolted just onto the gear box (nose dragger). The tubes along the side channels take up most of the stress and also allow the use of Cessna 150 seats. One difficulty with the BD seats is that the mounting feet of the seats reach outward to attach to the side channels. This makes it difficult to make the seat adjustable up and down. I built up a seat rail truss out of 4130 steel that allowed the seat legs to be perfectly vertical and therefore adjustable in height. The square tube would do the same thing and be some lighter I believe.
Ken Lysek, 4099 Woodglen Blvd, Thorton, CO 80233, PH 303-457-9769, bought a partial BD-4 and needs wing spars, landing gear, and control mechanization. Ken says that Bob Warfield, 8721 E Kettle Cir, Englewood, CO 80112 PH 303-796-8607, just about has his Ford V6 installed in his BD.
Robert Bollinger called to say that the Ford V6 will not fit a nose-dragger BD-4 without a good bit of modification to the shimmy dampner mechanization. He has decided to go with the tail-dragger. He reports that those of you who need the bearings for the aileron/flap torque tube assembly can get them for $ 13.91. The company is W. S. Wilson Corp in New York, 800-645-3714. Jeff Daugher is the person to talk to and the part number is B541DD. ' This company is generally wholesale but if you send an order and money, they will sell to you.
Dale Dunsmore (403-289-2513) purchased a BD-4 that has had all evidence of the builder obliterated. In order to get it licensed in Canada, he has to know more about the background. He determined that the number on the BD was N163BD. This is probably the serial number. He would appreciate any help.
Noel Dunlap wrote say that he now has 63 hours on his BD but he is taking it home for major re-work. He purchased it from Bob Holly in 1984 arid first flew it in 1987. His first problem was the weight -'it weighed 1170 lbs without interior. I guess most of us have forgotten that Bede's target weight was around 840 lbs. I guess we know why the gear legs bend a little! I assured Noel that the weight of his BD is lighter than average.
Noel found the BD very unstable in yaw but otherwise easy to fly. He had wing fences at the wing fuselage junction (they look to be about to half cord and 2 inches high) and a very large broad band antenna on the back of the fuselage. Removal of these items helped the yaw situation considerably. Another problem might have been the full length rudder Noel designed that incorporated a beacon light as part of the dynamic balance. The large rudder does really help the tail-dragging operations.
The wing airfoil is a NLF-1-0215 "Eagle" airfoil made up out of foam and fiberglass. The pronounced cusp at the lower trailing edge was a definite problem because the axle for the aileron/flap tube was at the beginning of the cusp and didn't leave a lot of material on either side of the tube/flap bushing which incidentally is 3/16 inch PVC plumbing plastic. The inner diameter of 1 inch allowed the torque tube for the aileron to fill quite nicely. The built-up aluminum spar was the key to making a wing that large maintain the original strength and was located on the hot wire forms to make contact with the upper fiberglass as a direct spar cap. This allowed almost 1 /2 inch under the spar to enable fuel passage between front and rear sections of the fuel tank. By necessity the front and roar of the tank had to have it's separate vent. The foam was purchased in the large blocks and hot wired on his forms by the numbers. There were four sections per airfoil, including the flap/aileron section. This in hindsight was needless trouble and expense. If he had known that there was a BD-4 newsletter/club and Jim Murphy aluminum wing in existence He would have opted for that wing instead.
The wing isn't very fast. Abut 140 mph indicated with 2 people on board at 23" and 2300 rpm. The wing may be heavier than normal however as two people can mount each side. Stall is very mild and actually ends up in full back stick sink power off at 50 kts indicated. Power on you can slow fly at that speed with 2 notches of flaps. Due to the reduced angle of incidence, the plane takes off 3 point and the tail wheel is on the ground before the wing is stalled on landing. It is an unusual experience to feel the tail wheel rolling with the mains still in the air. Noel expects to try to increase the incidence some way to correct this trait. The bird has been aileron and barrel rolled without any adverse characteristics but he has been to chicken to try any high G manuvers like loops or split S's. Maybe Jim Bede's figures for an 840 lb airplane don't apply to 1200 lb airplanes?
The only wing problem he has had are stiff ailerons and wing fuel leaks. Sloshing a number of times hasn't helped so he will open them up and try to find the problem. The stiff ailerons only occur when the wing torque tube is bolted to the actuator so there is a geometry loading there somewhere.
Allen Sandstrom has a Ford V-6 hung on the front of his BD and was playing with it on his grass field (it is not ready to fly yet). He hit a soft spot and the nose wheel sunk in and the prop was broken. He is now going to make it a tail-dragger. He gets 3700 rpm static with a 68" X 72" propeller which compares quite favorably with Ken Mitchell's 3600 rpm. He has the "dished top" pistons which are only 8 to 1 compression. It was discovered recently that not all 3.8 liter V6 engines were 8.8 to 1 as Blanton earlier stated. The low compression pistons have a 0.2" deep dish in the center.
Steve Mahoney now has the rounded windshield on and is quite satisfied with the performance. He has a taildragger with an O-360 and a fixed pitch propeller. He has not done any accurate cruise speed checks yet but he can do close to 200 mph. He did a pass at the Arlington air show that indicated over 220 mph (he was after a Wheeler Express).
Ray Ward is having fun again trying to improve his CAFE 400 Tri-aviathon scores. Aircraft engines are out and the newest thing is a 383 cu inch Chevy that puts out 430 hp at 5500 rpm. This is an aluminum block engine specially built up for racing. Ray is working with Dave Blanton to get a belt reduction unit made for him. They are now flying to work out a way to put the three blade Hartzell prop on that is now on the IO-540. By the next letter we should have a lot more information.
Richard Hedge, 1317 Camp Gifford Rd, Bellevue,
NE 68005 402-731-4374
Ian Park, 6 Mohonk Ave, New Paltz NY 12561 914-255-0056
Marvin Hays. 6707 Hwy 287, Arlington, Texas 76017 PH 572-4413
Noel Dunlap, 100 Dower Draw, Kila, MT 59920 PH 406-257-1869
Gerald Applefeld, 3437 Marble Arch Dr., Pasadena, MD 21122 301-437-7424
George Wittet, 766 W Lake Dr, Canandaigua, NY 14424 PH 716-394-5732
William David, 8372 Bellingham Ct., Huntersville, NC 28078 PH 704-892-0084
Jack Hays, PO Box 531610, Grand Prarie, TX 75053
Theodore B. Jones, 72 N Bailey Ave., South Haven MI 49090 PH 676-637-2419
Fritz Holsclaw, 72387 Incline Dr., Auburn, CA 95603 PH 916-823-1188
Bruce Labes, 434 N. Bums, Valley Center, KS 67147
Paul Roy, 2727 W Minton Dr., Tempe, AZ 85282 PH 602-438-1788
Dennis Love, 27510 NE 45th St.,Redmond, WA 98053 PH 206-682-0195
Joseph Peers, 14448 S Kolmar Ave., Midlothian, IL 60445
Ronald Hodges, PO Box 232, Miamisburg, OH 45342
BD-4B Homebuilts, 13524 Railway Dr. Oklahoma City. OK ' 73114, PH 405-749-0870
Robert Scott, 711 South St., Yreka, CA 96097 PH 976-842-3054
George DeVault, 12100 Wilshire Blvd, Ste 550, Los Angeles, CA 90025 PH 213-456-6029
Chuck Ingalls, 1403 Chestnut Dr., Port Townsend, WA 98368
Mike Lacey, 112 Ida St, Hot Springs, AR 77901 PH 501-623-1518
Walter Beecher, 29 San Jacinto, Galveston, TX 77550 PH 409-762-8124
Charles Oliver, 2664 Country Club Dr., Glendora, CA 91740 PH 7f 4-593-7665
VISIT TO JR METALS
On a recent Boeing trip I visited John Raffensparger in Baltimore, MD. We toured his business and had a great time talking BD-4's. I saw some materials such as large tail kits and fuselage angles that were getting ready to send to builders. John is also working hard on finding the right way to get metal ribs produced. He is also thinking about the 7075-T6 landing gear. I have a prototype header tank that he has developed. It looks very good and has a fuel level warning light system that will come or if the wing tanks are not feeding or if you are about to run out of fuel.
I also got a chance to meet some of John's family and to see his other hobbies - some people just never have enough to do.
As far as new airplanes, John has been wanting to build a very light BD type airplane for two people. He is leaning toward to Magnum Hapi engine for the power plant.
I looked over John's new elevator trim system which is made to be retrofit into the BD. It uses a Cessna type knobbed trim wheel and is geared down so that setting up for flat and level at high altitude will be much easier. We all have stories of how we let someone fly our BD's and they almost put us through the floor or roof when they tried to trim the elevator. This mechanism will really solve the problem.
We drove out to look at John's BD and I finally found the best way to make individually adjustable front seats. I must be slow but I never thought of building the frame about as normal but putting the slides just under the bottom of the seats. Most people try to, reinforce the floor but this ends up being very heavy and I'm not sure it meets the 6 or 9 g's requirements for hard landings. I like John's solution much better although of course there is some weight penalty over the standard BD seat.
To keep his battery fresh without burning it up with constant charging, John uses a cheap 'light timer' from the local hardware store to limit the charging time to a couple of hours per day.
If you have had trouble marking on aluminum and 4130 steel and worried about ' corrosion caused by it, John has some pencils that are specially made for this purpose. Contact him for price and availability.
If you are having trouble finding affordable 4130 steel tube, John recommends The Dillsburg Aeroplane Works, Charles T. Vogelsong, 114 Sawmill Rd., Dillsburg, PA 17019, PH 717-432-4589.
John is trying to get an order together for 7075 T6 main' landing gear legs. As you know most of the Bede supplied legs tend to splay out after a short time. Many of us now have the 7075 alloy legs and have experienced no trouble at alt (I even ripped my gear out sideways at 80 mph and didn't hurt the legs at all). You will have to call John to get the price (last I heard it was very reasonable).
COWLING PRESSURE SURVEY
Jim Huber and I conspired to do a pressure survey on the outside of my cowling last fall just before I sold the Lycoming 0-360 engine. This survey was done to determine the pressure with respect to true static pressure on all the surfaces of the cowling. This should help us to determine where inlets and outlets should be.
I drilled holes (.040 ") all over the cowling in a 6 inch grid. Rick Graf supplied the hollow wire that is used in the Boeing wind tunnel. The hollow wires are bent 90 ° and hot glued into the inside of the cowling with one end of the wire flush with the outside surface of the cowling and the other connected to a plastic tube that is routed to the cabin. Jim built a manifold to which we can hook up 12 tubes at a time. We used the water manometer principle to measure the pressure in each tube with respect to a reference. The reference was developed from a 100 toot long towed nyla-flow tube. A small funnel was tied to the end of the tube and the end was plugged. About 2 foot from the funnel several small holes were drilled in the tube to give an accurate static pressure. The airplane was flown in climb, cruise, and powered descent configurations. So far it looks like the side of the cowling is the lowest pressure area and would be best for exiting cooling air. The pressure at the sides of the cowl is very close to static. The pressure just forward of the bottom of the firewall was 3 to 4 inches of water and of course the pressure in the cowl was the same.
We really did have a good reason to do this test - I think. But beside that we had a lot of fun. It drives the people at the airport nuts trying to figure out what you are up to. The first day we flew the winds were cross to the runway and very turbulent due to the trees. As we were about to make our first low pass so my wife could give us some data on how stable the towed static line was, we saw my neighbor in an RV-3 just about ground-loop and then just about run off the end of the runway. We couldn't get any good data that day but it sure was a challenging landing.
ELECTRIC PROPELLER DEVELOPMENT
As I said in the last newsletter, I have a desire and a need to modify a Hartzell or a McCauley constant speed prop to an electric prop so that we all can use them on the auto engine conversions. If you take the front hub off either of these props you will find a piston that is about 5 inches in diameter that moves toward the hub when high pressure oil from the governor is fed through the propeller piston rod. If the piston is removed (very simple), all that is required is a geared down electric motor to push on the piston rod. The hub does not have to be opened or anything so the integrity(??) of the prop is not compromised.
In order to design an actuation system, you have to know what kind of forces are necessary to adjust the pitch of the blades for various flight conditions. On the last flight before I took the engine out, I hooked a 200 lb pressure gage to the oil line coming out of the prop governor. I fed the 2000 lb hydraulic line up and out of the oil door in the cowling and attached the gage so that I could read it through the windshield.
During the ground runs to verify the safety of the system, I found out why they don't want you to pull the rpm below 1500 rpm during the prop pitch check during run-ups. The pressure comes up when you haul back on the pitch (40 lbs or so) and then if you continue to hold it, at about 1100 or 1200 rpm the pressure shoots up drastically. I don't know how high it goes, but it did bend my gage and I had to recalibrate it!
In flying many different configurations, the highest pressure I saw was during a high speed pass at about 200 mph. The pressure was about 120 lbs. This doesn't sound like much but if you take it times the area of the piston in the prop, you and having to design for at least 2000 lbs of force.
My next problem is to come up with a configuration that is naturally balanced. It would be nice if we didn't have to rebalance the propeller.
I really don't care how fast the pitch change is or if it is constant speed. The only sensitive issue is what the failure modes are. If the motor were to fail when you had the prop set to a very heavy pitch (low rpm), it would be hard to do a go-around. It could cause detonation in the engine. I do not see this as much of a problem as most people use 2400 rpm for cruise and that should not stress the system too much.
I just got a call from Hans Mayer of Huronia Aero Marine, 110 Everton Rd, Box 18, Site 6, Sunnyside, Midland, Ontario, Canada, L4R4L9, PH 705-526-6863. He is developing a belt gear down system that could be used on the BD-4. It is much like the Blanton system except that the frame is made from castings and looks very nice. He uses two smaller HTD belts as it reduces the belt noise (by 20 dB to 90 dB) to less than the exhaust. The only reduction ratio that would be usable on the BD-4 is the 2 : 1. This will give you a better power on take-off but might cause you to run the rpm too high at 200 mph cruise. The solution of course is to have a variable pitch propeller. He also has that covered as the reduction system is strong enough to mount a constant speed prop and he believes he has away to supply hydraulic pressure though the prop shaft to vary the pitch. A propeller governor could be mounted ,and belt driven off of the engine like Jim Huber has done on his Mazda conversion or -a small hydraulic jack hand pump could be used (variable pitch only).
Maybe it would be better to consider the Electro-Prop which is now coming out. It think it will be quite a bit lighter and their initial guess at price is with in reason (Hartzell reason anyway).
In the last Blanton newsletter, Mr Blanton has chosen to take a :few swipes at the BD-4. that in all my experience with the airplane have not proven to be true. I have all the accident data available from the EAA and the FAA and the issues brought up by Mr Blanton do not appear. I also have talked to a great number of builders and most of the objections he brought up are just not true. I hope Mr Blanton will see fit to admit that there are a lot of us cut here with BD-4 building and flying experience that find it an excellent all-around airplane.
If you have questions about any accident specifies, you can contact me for more information.
HUBER MAZDA BD-4
The picture of the Jim Huber's BD-4 on the back of the last newsletter brought quite a few requests for more information.
Jim has been working on his conversion for quite awhile now and has done a lot of research as to which way to go. His engine has been upgraded to the 1988 RX-7 status. At this time the carburetion is pretty standard and does work but seems to generate a lot of carburetor ice in certain climatic conditions. He has an Ellison Throttle Body Injector that will be fit soon.
He chose to use a 3 : 1 Hurst gear reduction unit built in Germany. It is an industrial unit that normally has a clutch and reverse gear built in. He removed all the unnecessary features and connected up a lubricant cooling system. The whole gear box is bolted to the front (rear in car) of the engine.
The prop shaft connected to the gearbox is long enough so that the high pressure oil from the output of a prop governor can be injected into the hollow shaft much like a Lycoming engine does. The propeller being used is a McCawley C/S such as used on later Mooneys.
The whole system is installed on a homebuilt dynamometer. This is of the type described a long time ago, in Sport Aviation, When the engine turns the prop one way, it tries to turn the other way (for every action, there is an equal and opposite reaction). It is quite easy to measure the turning force of the engine if it is mounted on a pivot such as a car axle. Jim is using a hydraulic cylinder connected to a large pressure gauge to measure the engine torque.
There will be a lot of ground running done before the engine is installed in the airframe. Jim is keeping accurate records of the run-in for later use in certifying just what has been done in developing the engine. The hope is to get the engine to put out 220 hp maximum and a cruise power value that will be reasonable for gas consumption. He has done most of the 5500 rpm run, but was interrupted by a visit from the Police. It seems his neighbors don't appreciate the sound of his Mazda. He is now looking forward to doing the rest of the run-in on a nearby airport.
There are some great advantages to using a rotary in an airplane. The weight advantage is not great but the smoothness of operation and almost non-existent failure modes are fantastic. The engine is supposed to be capable of pretty well trashing itself and still put out 50% power. The smoothness should be great for reducing propeller fatigue problems and making flying more comfortable.
New Ideas On The Fuel System
William O Singer
If anyone had a hole cut in their car's fuel line as big as the line itself, I'm sure they wouldn't want to drive it! Yet, we let Jim Bede cut a hole in our BD-4's fuel line.
With no fuel flow, the fuel stands in each "stand pipe (A & B)" the same height with ' reference to the earth. Now empty down to approximately 1/4 tank and give it a high angle of attack. After "A" becomes unported, the fuel will still stand level until the valve is opened and the pump is pumping. Then Mr. Bernoulli takes over at the wye at "standpipe" A. In effect, the height of fuel can be used in a computation to show what the pressure is in the fuel line. What is important is that the fuel flow must be equal to full power and the angle of attack must be as high as anyone would ever reach. If you try this and the system still seems OK, then try this. Put on finger strainers and you should see the fuel drop slightly in "A" as the air should pass through easier than the fuel will in B at high flow rates. Now let's really get dirty and put some crud on the "B" strainer and depending on how much you put on, you will see the pump will pump air into the system. (Instead of real dirt just squeeze "B" with your fingers if it is clear plastic tubing)
At any rate, I am not going to use Mr. Bede's hole in my fuel system. Now to get on with the proposed fuel system for a BD-4. Everyone, of course, will decide when enough is enough, so feel free to stop, wherever your (KISS) tells you to (Keep It Simple Stupid).
Years ago when I had completed my runway, my flight instructor brought his Cessna 140 down to try it out. Well, you know, the whole family had to try it out with him, and much to his dismay he demonstrated how to have an engine quit on take-off, about 50 feet high. He did switch from the empty tank and therefore, the story has a happy ending.
I learned to fly with a Piper 140, but not alone, as I know there was a gremlin who switched the electric gas pump switch for me.
I owned a Cessna 150 for several years and never touched the fuel selector of a fuel pump switch so the gremlin had a vacation.
After you read the following, I'm sure the gremlin will be coming home. But I hope we can find enough positive to outweigh the negative. By the way, I wanted the Cessna 150 on the ground when the fuel tank gages read 1/4. I hear that's a good idea for a BD-4. What does that cost us? Use your own figures but my estimate for two, four bay tanks would be around 50 gallons, divide by 4 and we must be carrying around 12 gallons or about 72 pounds just to feel safe. If we need about half of that for safety (FAA) then anything I do that weighs less than 30 pounds should be OK.
First (1) let's seal off the bottom of the inboard bays. This gives us four tanks. (2) Let's put very high octane gas in one for take-offs and we'll never have detonation. Let's use the other for our 30 minute surplus to (3) keep the FAA happy. This leaves us with two tanks and we will connect them like our gremlin-free Cessna 150. (4) This means adding a crossover vent between the tanks. Let's use Bede's new little sumps on the inboard tanks (make sure the door and your head clears this - ed.). (5) Put our Cessna 150 style vent behind it to keep the rain out. (6) If we are clever with our gas tank caps, we can place a (7) filler neck so we can fill four different tanks with the two original caps.
Use two, four-way fuel selectors. The same as in the BD-4 kit (3 tanks plus an off position).
Hook the two selectors in parallel. Hook Bede's rear fuel tank ports into his new design sump (with quick drains) leave one inch at the bottom (8) and (9). Hook front ports to a line going over (10) and (11) into the main tanks. It would be OK to take them over the top of the first tank baffle. Tee them together and hook to top ports of fuel selectors. Notice, we are using the same number of lines that Bede has already installed. Hook the other two lines (8) and (9) separately to the remaining ports of the fuel selector.
Notice that when the selector points up they should be on the main tanks and if they point left they should be on the left small tank, and if pointed right to the small right wing tank. Sorry about this, but two gascolators (13) and (14), one to the electric pump the other to the engine driven pump. Hook the engine pump to the carburetor (15) with a tee. The electric's pump goes to the fuel sender for your gallons per hour meter (17). Hell, we still have a lot of gray matter not being used so tee in at the electric pump at (18) and hook it up to the right tank's fuel line at (19) through another fuel selector (20) mounted in the center of your dash. Two position, plus an off. Notice that the "pole" (in electrician language) goes to the right fuel tank line) the other position tees in as close as possible at the carburetor.
I don't know, but maybe I can employ two gremlins. But let's see what we get for our money's worth. We could add two check valves at (21) and (22). I forgot the tee at (23) for our fuel pressure gauge. We will leave the electric pump on at all times.
So we get in the plane and turn on the master switch and we notice we have fuel pressure from the electric pump. If we don't, check and see that the three position fuel selector is not set to the electric pump position. If it was, notice that we would be pumping fuel into tank (3) and the fuel would be coming from whichever tanks the electric fuel selector was set on. My drawing shows it coming from the mains, so we would run fuel out the vent. No, it just overflows through the filling hole (7) back into the right main tank.
Now that we have fuel pressure, start the engine and if the engine pump is working, notice in increase on the fuel pressure gauge. Note: we set the regulator (16) of the electric pump below the output pressure of the engine pump. We also notice that if the electric pump was mounted so we could hear it, that it stopped running when the engine pump took over. If it's mounted so we cannot hear it, better put a device on so we know when it is pumping.
Before we lake-off, let's put the engine pump fuel selector on the high test tank and the electric pump on reserve tank. That's where it should have been when we tumed the master switch on to have proof we had at least a little reserve fuel. After taking off and reducing power, put the engine pump on main tanks. In ordinary flight, we have nothing else to do. In fact, we had only one tank switch to do other than just looking at the fuel pressure gauge at start up. Or nothing to do if we know we had high quality gasoline in all the tanks.
So what happens if the engine pump no longer delivers fuel -- no flow of adrenaline at all. We notice that the electric pump comes on automatically and we should have time to calmly figure out why the engine pump is not pumping.
What! The weather man didn't forecast the strong headwinds you are now encountering and we want to get all of our gas out of the main tanks, maintaining a low pucker factor. Simple, switch electric pump to main tanks, position selector to electric pump after having burned the fuel out of the right reserve tank. Just be sure you are not running engine pumps on main tanks. You can sip every drop out of the main tanks as it isn't going to hurt anything to let the electric pump pump air. If you can hear it, it will speed up when the mains are empty. If those headwinds are really causing you to push it, you can understand how to empty the third (2) tank into the (3) fourth and with Bede's new sump you can rest assured you have burned every drop of fuel and I know that we will never have to try it to see if it works (burning all the fuel I mean). Believe me, this is simple compared to some of the schemes I started with.
For the tip tank guys, just put two-way selector valves up at each wing root and use the same idea to fill the tip tanks (except they are not at the tips: and you are not as liable to get into an unrecoverable spin.
In case of engine pump failure the electric pump comes on automatically. What happens it we lose our battery? Remember Dave Blanton has a small back up battery for the ignition modules and we can select the center three position switch to engine pump position and get gravity flow to the carburetor bypassing everything including the fuel filters. You do fill your tanks through a final filter, don't you: Some fuel pumps may let fuel free flow anyway.
From a Ford Diesel two liter car fuel filter we add sensors (24) to detect water so by being able to drain gascolators from inside the cabin, we don't need quick drains on the other tanks.
To be able to fill the main and tip tanks easily from a gas container it will be necessary to place a temporary filter neck into (7) the inside filler neck. The inside filler neck must be lower than the vent. It would be nice to install a knock detector from a turbo-charged car. The fuel pickups in main and tip tanks would be mounted in the center of a bay with a protective flat plate to protect the bottom of the wing and with a beveled end so they won't suck shut.
A BD-4 Fan's Oshkosh 89 Observations
The BD-4 is back!!
Jim Bede's BD-4 forum gathered a half tent attendance (at 8 PM) to announce the resumption of kit production. JB has re-acquired the rights to the original construction manual and plans rights (my inside informant said he never lost the copyright) and will over time make the entire materials kit available. Here is the summary of the forthcoming kit's (to be known as the BD-4B) differences from the original airplane.
The front windshield corner post radius will be increased to 1 inch.
The main landing gear will be a tapered (steel?) rod similar to the newer Cessnas. The tie in will remain the same using the Lord mount in the existing carry through box.
The fuel system will be modified (see sketch) and possibly will include an option for a left-right-both-off fuel selection.
NOTE: The fuel system discussion led me to conclude that JB assumes that as long as one of the two feed ports are covered, fuel will flow.
The gross weight, using the standard wing, will be Increased to 2400 lbs at 4-2 g's. This change is accomplished by "re-writing the spec. sheet". JB stated that a Beech constructed BD-4 wing was tested back in the G.O.D.'s (good old days) to allow a 2500 lb gross weight at normal category (3.2 g's).
The wings will be constructed from RIM (reaction injection molded) "urethane" plastic wing cells, or optionally hydro-pressed metal ribs and metal skins.
All wing bonding, rib cell to rib cell and cell to spar is now completely PRO-SEAL (includes metal wing option).
The flap chord is extended 2" using a trailing edge insert.
All this for an approximately miserly sum of $23,000 American (minus engine, prop and instruments). Wing spars will be the first to be stocked and are on order (check or money order for $1,100 each spar- 2 per airplane), wing center sections are in stock (14 to 15 on hand, call for price quote).
So much for the sales pitch (oops I mean the BD-4 forum). The following BD-4's were in attendance: John Manius, Gene Selchow, Deane Ogden, Bill Dorfman, Darryl Wright and Jack Hartmann with newly finished N442EE, Cecil Hopkins, Ray Ward, Ann Ward, John Holland, Joe Lineau. ? Duggan.
Remember! This is the first time there have been His and Hers BD-4's at Oshkosh. Congratulations Ray and Ann!! Ray said that Ann set her BD for 2500 rpm, 23", at 8500 ft and Ray had to set the Super BD at 1800 rpm and 21" (200 mph TAS). Ann got 16.42 mpg while Ray got 18.38 mpg.
The CAFE 400 has been run again and BD-4's are still turning in some fantastic results. When I talked to Ray Ward after the race, he was down because he came in second in the Tri-Aviathon. But when you look at the numbers, he was edged out by just a little by an airplane (Venture) that must have only about 1/3 the wetted area of the Super BD-4. It also weighs less and can only hold 2 people. I talked to the Venture people at the Arlington fly-in and had fun asking them how much horsepower they put out at 3400 rpm. They insisted they never go over 2500!!
They said that they were sure that Ray (who had to fly first) knew something they did not know because when he took-off he held the airplane low low to build up a lot of speed arid then did a zoom. I assured them that he was just guessing at what might be best - that's right isn't it Ray?
You will notice that the third place finisher had about 1/2 of Ray's score and the Venture (just back from breaking 7 worlds records) only beat him by 6%! Ray also beat a GIassAir III and a $235,000 Siai Marchetti. The gentleman who owns the Marchetti was going for speed this year in the Tri Aviathon but was beat by Ray. He has been trying for several years to win something at the '400. He started with a Mooney and after putting many thousands of dollars into it, he gave up and spent more money on the Marcetti. He still hasn't won anything.
As Ray was getting ready for the race, he considered a change of airfoil or at least adding a cuff on the leading edge (if he can get his slow speed down some it will really help his Tri-Aviathon score). Ray asked around and found out that Harry Riblett does a lot of airfoil work. He called Harry and and asked whether a cuff would work or what type of airfoil would work best. Harry unleashed his computer on the BD-4 airfoil and come to the conclusion that it should not be changed In any way!! His best suggestion for getting a little slower stall would be to extend the flaps by 2" or so (just like recommended for the BD-4B).
Ray is getting tired of all the garbage about the BD being old technology and that the price asked for a new kit is too much. Consider the following: Glasairs for sale at $65,000. Ray's BD outruns the $230,000 Saia Marchetti - it will out climb it and it has more useful load. A regular clean BD will outrun a $100,000 + Mooney. 'Ray thinks that anyone who sells a BD-4 for under $25,000 to $30,000 is stupid.
Ray decided that he would run the actual CAFE 400 part of the race as fast as he could and set a speed record for fixed gear airplanes. He flew the course at 214.1 mph and 10.64 mpg.
There are many different ways to find load carrying capacity of aircraft structural members. One such method was used by Bill VanNoy to calculate wing spar strength (see Issue 11, August 1984). Bill used an analytical approach to determine the load carrying capacity of the spar. I felt this was a good analysis as it seemed to agree with reported test results of a static load test performed some years earlier.
As I wish to extend my wings I am looking for ways I can increase the load carrying capacity of the spar. I approached the problem a different way....I made scale models of the wing spar / cabin spar assembly and used a calibrated tensile tester to load them to failure. I also placed strain gauges so I could measure the stress during loading. Here is a summary of the results.
To model the wing spar I used a section of 2024-T3, 1.20 O.D. by 0.035 wall tube. This was chosen for the following reasons: It fell the closest to the Diameter / Thickness ratio of the real spar and I didn't want to exceed the 1000 lb limit of the tester.
The solid center spar in Test #2 did improve the results some (480 lbs went to 512 lbs). Test #1 shows the center of the failure as 3.10" from the side of the cabin or 1.39 diameters from the end of the center spar. Note that in Test #2 the failure moved out from 3.10" to 3.40".
I have a friend that has a BD-4 wing spar that was bent in an accident. It bent at 20.00" from the cabin side or 1.33 diameters from the end of the cabin spar. This is very close to the numbers I got in test #1.
In this test I wanted to see what would happen if I extended the center spar by just inserting a floating section. Note that the buckle popped "out" instead of "in" as before. This shows we may never be able to get back quite all of the 14 % theoretically possible.
The main problem in using purely analytical methods in calculating the load carrying capacity is that the failure mode is buckling of the tube. Buckling is rather difficult to deal with but I found some data on bending of aluminum tubing in the text Bill referred to (Analysis and Design of Flight Vehicle Structures). I have no idea how the data was obtained (empirically or analytically) if empirically then how did they obtain the data for Fb/Ftu of very close to 1? The text gives no explanation. Here's what we can get out of the graph. On the wing spar we should be able to increase the load carrying capacity of the spar by a maximum possible of about 14 % by preventing buckling in the spar tube. The cabin spar has a Fb/Ftu of very close to 1 so forget about doing anything to restrict the buckling of it. I would guess it would most likely fail where we drill all the holes in it to mount it to the fuselage.
In the text referenced by Bill (Analysis and Design of Flight Vehicle Structures) I found a graph which I found quite useful. Since the O.D. of the BD-4 wing spar = 6.680" and the wall thickness = 0.135", the D/T is = 49.5.
Center Cabin Spar
Test Wing Spar
30 (32 ed.)
D = Outside diameter of tube
T = Wall thicknesses
Fb = The stress at which buckling occurs
Ftu = The ultimate tensile stress of the material
In Bill's analysis it appears that we need a 18 % improvement to equal the short wing in moment carrying capacity for the long wing (24" extensions). It looks like we can get most of this (14 %) from just preventing the wing spar from buckling as indicated by the tests. Some people may feel comfortable flying around with just this simple of a modification (simple is beautiful I think). There is no point in preventing wing spar failure much beyond this as the cabin spar becomes the mode of failure. Below is a design which may improve both.
This design adds 11 inches to each end of the cabin spar. The cap at the end provides added strength by preventing the extension from distorting into an oval shape. The tie rod should increase the bending moment the cabin spar can take by moving the neutral axis to a lower point. Steel is used as it has a modulus 3 times that of aluminum. It must be heat treated to 3 times the tensile of 2024-T3. Using this design un-symmetrifies the load carrying capacity of the wing. It's never been tried, analyzed or tested. Use at your own risk!!!!
It is nice from the standpoint that you don't have to put any additional holes into your existing structure.
It's amazing how long it takes me to build a test section and only a few short minutes to break it. So I only build one test per design. This is hardly a statistically meaningful sample size. But I feel that in looking at the mode of the failures we can learn a great deal about the nature of the full scale failure. I did not feel it appropriate to extrapolate the data to full size. I will offer to load anyone's design if they build it (breaking it is the fun part!). I will also make the broken models available to anyone who may wish to see them.
New Solid Link Aileron controls
I have had several people ask for a drawing of the new aileron push-pull control system 1 used when I rebuilt my BD-4. Below is the approximate design. I really can't give actual drawings of each piece as I made them as I went and certainly didn't take the time to trace them. Besides some things will be different for some airplanes. One of these items is the bracket on the far right which holds the 90° belcrank to the side channel. I actually used one bracket to the side channel and another to the angle (CS-35) which holds the control stick assembly, which is also braced to the landing gear box (forward because I have a taildragger). Be sure the thicknesses of metal are correct and that the belcranks are rigidly fixed as there is a good bit of compressive force in this system.
Be sure to buy 2 extra belcrank bearings to put on the CS-15's. Most of the slop in aileron systems is caused by wear in CS-14 and CS-13.
I'm sure you have all been aware of the great horsepower debate. It seems to be Dave Blanton against the world. Aviation Consumer has carried letters by all involved and Glasair News has carried Point / Counter-Point letters and it seems most of the world agrees that the 3.8 Liter Ford V-6 engine (modified as per Blanton but with 8.8 : 1 pistons) should put out some less than 200 hp. A friend of mine has looked at all the arguments (which are by no means clear) and believes that Dave has made a math error.
He called the Lycoming engineering group and they claim that the idea of airplane engines being rated at 5,000 ft is not true. It seems that no-one knows where that bit of confusion came in.
I guess what really matters to me right now is that there are several claims that the V-6 will turn up the same prop to a higher rpm than a Lycoming O-360 will. It looks to me that there will be only a small weight penalty with the V-6 and there sure is a price advantage. I think the jury will be out until we get a bunch of these engines flying. As in speed claims between airplanes, you have to "fly them side by side" to really know. I have no doubt that Dave's claim of not everyone using the same size horses is true whether it be due to marketeers claims, competition claims, or inaccurate measurements.
You might be interested in a letter to Glasair News from Neil Bingham:
I've been digging deeper into the engineering problems of converting auto engines to aircraft and I would like to share an item with you relative to the Ford V-6.
It seems that a 230V6 Ford engine was modified
per Blanton's handbook and tested on an independent
dynamometer. I have the test data from that
The dynamometer reads out torque in lbs-ft vs. RPM. The horsepower was calculated from these curves using the normally accepted formula:
HP= 2 "PI" T N / 33,000
Where: T=Torque in lbs -ft
N = rpm
I then took the Lycoming manual for the O-320 series engines and used the HP vs. RPM curve and plotted it. Since Lycoming does not give torque values (this makes it difficult to really know what their "horsepower" calibration really is, ed.), I calculated them from the HP curve using the above relationship.
It suddenly became obvious why the data I have from three builders say their Ford equipped aircraft (Glassair TD, RV-4, and BD-5) are getting performance similar to that obtained when equipped with the O-320 B or D series. The curves show the engines to be almost identical in horsepower output at their respective operating RPM's.
The conclusion is that Blanton seems to be grossly inflating his horsepower figures. What is even more distressing, the builders don't know that until they fly their airplanes. Even then they probably don't know why the performance isn't there and they go in another direction out of sheer frustration.
The jury is still out on whether the Blanton cam regrind is the correct profile or even if a standard cam can be reground, or if a totally new cam blank must be used. Maybe the Ford won't get there with any cam and/or piston combination unless it's turbos or supercharged.
Another interesting point is that we have
all been wondering why Davy Blanton, Jr.
got only 168 mph out of his new "Racer"
featured on the front cover of Sport Aviation
for March '89. A simple calculation may be
a clue as to why. Using the relationship:
V = K ( HP / Aw)^.33
V = velocity (mph)
HP = brake horsepower
Aw=wing area (sq. h.)
K = constant for a given aircraft
V = 168 mph
Aw =140 sq. ft. (estimated)
K = 160 (est.) Glasair FIG =194
Cherokee 180 = 145
Solve the above equation and you will get 162 HP.
I'm not ready yet to say the 3.8 Liter V-6, either GM or Ford is not the answer, but it's beginning to look more like a possibility, the deeper I dig.
Another thing to be considered is that Dave Blanton does not recommend putting the 10.5 : 1 compression pistons in right now. It seems that some people have bent their rods to some extent. It is also important to inspect the pistons that are installed in your V-6 to see if they have a flat top or are dished. It seems there were some models that had the dished pistons which only have 8 : 1 rather than the desired 8.8 : 1. The low compression pistons have a 0.2" deep dish in the center.
I have been collecting data on all types of engines lately to get a feeling for the number of horsepower you can expect from one cubic Inch of displacement. The average of engines that I thought were comparable was 0.85 hp/cubic inch. This says that the V-6 will give 197 hp. I also saw the same type of chart from Design News. It shows that a two valve engine of 232 cubic inch displacement can have horse power ratings from 130 hp to 225 hp. It looks that with high compression pistons we can expect about 200 hp.
Cabin Noise Reduction
Steve Mahoney has been working on getting
his BD-4 faster but he also has been interested
in getting it quiter. He has added very little
interior because "a light airplane is
a good airplane". Steve used a'sound
meter from HP used for measuring factory
noise for OSHA. It does not check for frequency
content which makes it hard to determine
the souce of the noise. When I used it in
Dave Wesley's BD, it read the same whether
it was held in the center of the cabin or
near the doors where air leaks occur.
You will notice that the "cuffs" on the window do help in reducing noise but the curved window helps more (Steve also doubled the front quarter windows).
Propeller Pitch Revisited
The following graph was generated with the same program as those in the last newsletter. I made this one to give you a general chart so you can pick the amount of twist for your particular application.
by R D Mellema and Jim Huber
I have been promising for some time that we would do a real BD-4 fuel flow test. We finally got it done (I have been delaying the newsletter for it). Jim had an old style end rib from a BD Panel Rib wing so we used it to build a small quantity fuel cell with the outlets all in the right places. We hooked everything up with just the right size of clear plastic tubing. All the tubes were run in the same pattern as the BD-4. We hooked an electric fuel pump up just about where the engine driven pump would be.
We first set the wing fuel cell at 0° , closed off the fuel line at the carburetor, filled the tank with gas, and watched the lines. We found that the diameter of the lines will allow the air to bleed out and the lines to fill with fuel. This is a very slow process and any reverse slope of any line will cause an air bubble to stay in the line. We had to really work at getting all the air out. You cannot build the airplane so that all the air will automatically bleed out. Without clear plastic tubes, you cannot guarantee that there will be no air. If fuel is flowing in the lines at a 10 gal per hour rate, the bubbles will not migrate upward.
If the fuel is higher than the highest point of the gas lines, and the fuel line is opened at the carburetor, the lines will fill fully with fuel (it helps to blow on the fuel filler hole, especially if you only open the gascolator which doesn't let the fuel run as fast).
If you now start to tilt up the front of the wing tank (no pump but the carburetor running at 10 gal per hour), the gas runs (siphons) in a good fashion until the angle of attack is such that the top surface of the gas is level with the "T" by your left knee where the two lines from the tank are tied together. At this time the siphon is broken in the rear feed line and the flow stops. The angle of attack that this takes is really extreme and cannot be reached in any type of normal climb-out unless you have 345 hp or so. When pilots tell you that the angle of attack causes the fuel to quit flowing, it usually really is a skid or slip condition (pushes the fuel to the outboard side of the tank) that does them in. This force is much more important than the angle of attack. If the "T" were lowered to the floor as suggested by some, the angle of attack would have to be greater to break siphon.
Now for those of you who believe that the fuel pump (it was off in the above test) will suck air rather than gas - it just ain't so. We put the wing tank in a very high angle of attack where the front fuel port was not covered with gas - in fact the gas was two feet down the line but absolutely level with the top of the fuel in the tank. Then we energized the fuel, pump to see if it would suck the fuel in the front port line down to the "T". It did not, It only lowered the fuel in the half filled line by about 1/2 inch. So you see the fuel pump did have some effect but a very small one.
If either (not both) outlet port was uncovered for a short time and then recovered, fuel flow continued without a problem.
A header tank is a good idea but there are some problems that should be considered. Unless the header has a "fuel low" warning light that grabs your attention, it really doesn't really do what it should. If a "both" position is used on the fuel selector, one side or the other should feed even if the rudder is misused. However, fuel can be accidently cross-fed and sometimes one side will not feed as quickly as the other due to venting differences. If you get really low on fuel and the low fuel light comes on you will not know which tank still has some gas in it.
If you expect the fuel pump to pull gas from the wing tanks when a header tank is used, it will not, it will only pull air from the header tank air vent: If the siphon flow stops, it will have to be restarted by blowing on the tanks or slipping to push the fuel inboard (it may start just by filling the tanks and then opening the gascolator to, let the system purge Itself.
Jim is considering a single point feed system. The following figure shows what happens with the standard system for different angles of attack and what the unuseable fuel levels are. If the 0° line is followed to its lowest point (this is the position of the forward port), you will see that about 5% of the fuel will be unuseable. The lowest dashed line indicates that there will be 14% fuel remaining if the attitude of of the wing is such that gas is 1/2 inch higher than both ports.
If you are low on fuel, it would be best to fly slow (high angle of attack) so that all the fuel goes to the rear of the wing. This is shown by the lowest point of the 12° line (this is the three-point angle of the tail-dragger).
The upper dashed line shows the 1 /4 tank mark that the BD-4 is placarded for.
1. ASSUMES WING LEVEL, BALL CENTERED
2. FOR TWO FEEDS, ALL LINES WERE ORIGINALLYFILLED.
I just talked with Jim today at lunch and he has another plan for how to build his fuel system. He seems quite sure that this is the right way as he has already started building the wing. The new method is to put a sealed bulkhead a short distance behind the spar that goes from the top to the bottom of the wing. He now has two tanks in each wing, one foreward and one aft. There are two outlet lines, one for each tank. The outlets are close together about where the forward one normally is located. The front tank will be used for take-off and the rear is for cruise or auxilliary. By having only one outlet in each tank, Jim has gotten around any problems with one outlet breaking the siphon of the other. He will run the two outlet lines (from one side) to a selector, for: main, auxilliary, or off. Now when the airplane is flown in a skid the outlet line can still suck air but when the skid is stopped, the fuel pump will quickly purge the line and suck gas. There is a separate electric pump for each side. To get rid of the 'skid' problem both of the gas valves could be set to main (left and right) and one of the tanks will always be feeding (check valves will be needed to keep from pumping fuel from one tank to another). Each front tank will hold 22 gallons and each rear tank will hold 27.5 gallons. There will be a total of 7 bays on each side that can hold t fuel. Jim has some plans to fly from the US to Australia in the future. Of course now there are a couple of stops in the Soviet Union planned. This fuel arrangement has not been tried yet so use your discretion!
Fixed pitch propeller selection is a difficult task. The amount of blade twist is usually set for a particular speed and of course a BD-4 must be able to got good thrust from 0 mph to 200 mph. The twist of the blade changes from the hub to the tip because the tip moves through the air at a much higher speed than the hub area (the blade needs twist so that each part of the foil has the proper angle of attack for lift). The airfoil near the hub almost points forward and the airfoil near the tip is almost 90° to it. The amount of twist is usually given in the number of inches the blade will 'screw' through the air in one revolution. This assumes no 'slippage' of the propeller. The propeller always does slip (during run-up the slippage is 100%) so there is error in calculating which prop is the right one. If that isn't bad enough, the prop makers measure the angle of the flat bottom of the airfoil with respect to the flat front of the hub. The flat back of the prop is not the chord line of the airfoil - so the 'pitch' is not tied directly to the angle of attack (of the chord line) needed for efficient power transfer. For instance, in the figure below, a 72 inch prop turning 2600 rpm should push an airplane 177 mph. This is the 'no slip' calculation of an airscrew. If you fly this prop at the above rpm you may well get 190 mph. This is due to the fact that the true chord line has a pitch of 77 inches (more or less). The most efficient angle of attack of a propeller is also dependent on the type of airfoil used.
The twist of a propeller along the length of the blade may not be all set for a particular speed. Quite often the twist is adjusted to make the propeller lighter, stronger, or easier to manufacture.
The best way to buy a prop is to get one that is said to work on an airplane of the same horsepower and speed. In other works talk to the manufacturer and rely on his recommendation.
So far I have seen the following props on the V-6 engine:
Ken Mitchell was using a 68" long, by 74" pitch prop (flying).
Boyd Francisco is using a 68" long, by 72" pitch prop (flying).
Rick Graf is using a 64" long, by 72" pitch prop on his 351 Ford V-8 and turning 2550 static (direct drive). This aircraft is not flying yet but I have had it over 70 mph on the runway.
proofed and corrected 10/21/01 rlw
added thumbnails for quicker loading 10/22/01 rlw