BD-4 NEWSLETTER #23, July, 1995
Roger D. Mellema
17605 SE 288 PI.
Kent, WA 98042
Ph: 206-631-5324

The editor of this newsletter cannot verify that the information contained herein is accurate. This newsletter is only a clearing house for the ideas and opinions sent in by various BD-4 builders/owners. Treat this information as if you overheard it during a "hangar flying" session at your local airport. rdm


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I am really starting to believe that time accelerates as you grow older! The pressures of my job at Boeing have really slowed me down in working on my first love which of course is experimental aviation.

Just got back from a day at the Arlington, WA airshow. I can't believe that I missed the last two years and it is only 20 minutes away by BD-41 There were lots of BD-4 people there and I had a lot of fun talking about BD-4s and auto engines. The first BD-4 I saw there was Fred Hinsch from Richmond, BC, Canada. His airplane looks better each year and he is very happy with his "Barnhardt" nosegear. His new door hinges and attachments really work nice (see Newsletter 21, page 8). Steve Mahoney was there early and said that he was very tired of telling people that "no, my airplane does not have a V-6 in it - Roger will be here on Saturday". There really is a lot of interest in the auto engine conversions - there was a vendor in the commercial exhibits area that had several beautifully built-up 5 liter Chevys ready for sale. There is a lot more action in the 130 hp and smaller engines and PSRUs. NSI and Stratus really look like first-rate companies but only time will tell.

NSI has also developed an electrically adjustable prop hub that uses Warp Drive blades. The price for the unit is $2100 to $2800 and they will use your existing blades. I plan to check into whether their hub will work for my - 190 hp Ford. I remember how exciting it was when I set my prop for maximum climb performance and took off with my engine putting out full power! A goodly amount of fuel can also be saved by lugging your engine a little during cruise. One gallon of Av-Gas per hour for 1000 hours will pay off your new hub. You can tell that I really miss my constant speed prop!

Steve Mahoney and I flew the fly-by pattern and did a 200 mph pass. The air show announcer gave a brief but accurate commentary. We also gave rides - I do feel comfortable now offering rides in my V-6 powered BD. It is always bad giving rides at a busy event as it is hot, crowded, and there is some increased danger that I hate to be subjected to - but add to that a very experimental engine and the result is that I haven't given many rides.

Steve has an O-360 engine and a fixed pitch metal propeller. When we did our air work it was obvious that we were very closely matched. He does have an empty weight advantage and clearly out climbs me on the "zooms". He has short wings and I have an extra 36" on mine. On the high speed pass my engine was turning 4600 rpm (redline is 4800) and the propeller was turning 2700 rpm.

Better Differential Ailerons:
After the discussion in the last newsletter an aeronautical friend suggested that I try to put in more differential aileron movement by changing the configuration at the bottom of the control stick. This is the result of my study - it has not been tried yet.

It will be necessary to modify some of the existing parts and you will have to extend or buy a longer CS-8.

This modification will greatly help the differential aileron movement that your BD-4 can attain. If this is a retro-fit, it may be possible that you have to re-drill the bolt hole in your aileron torque tube where it fits into CS-20,21. The differential ratio at the limit of travel will be 2.2 rather than the 1.2 you get when built per plans. the ratio at 0.5" of stick travel is 1.06 rather than 1.01. The most important aspect of getting the ailerons set right is the "up" aileron starting position. The aileron should be at the 27+° position and the aileron bellcrank (CS-20) must be as low as possible (CS-17 hitting the bottom of the slot in angle 5) before the hole is drilled in the torque tube.

You will notice in above chart that the differential ratio changes depending on how much the stick is moved. I do not know how much better this system will be when control input is small.

Swirl Tank:
The coolant flow in automobile engines is not always fast enough or "up-hill" enough to ensure that all air will be purged from the system. Some automobiles have a bleed valve to release trapped air when filling the cooling system. Engines also generate "air" when they are running at high power settings. The "air" is steam caused by small areas in the block or head where boiling occurs. A lot of builders (different engines) have found that they do need to run coolant/air bleed lines.

Experience with the Ford 3.8 Liter V-6 indicates the need for bleed lines in some installations. The cooling system flow and pressures must be understood to know where to connect the bleed lines.

The size of the bleed lines is important as any coolant that flows through them is really shunting around the heads. A good size for the line is 1/4 inch inner diameter.

When steam is generated within the engine it is important to keep the steam from getting to the radiator. It is better to bleed the steam off to the atmosphere if necessary to avoid having it go through the radiator. Generally, steam is not produced for very long periods and only a small amount of coolant will be steamed away.

A swirl tank may be needed if coolant is being blown overboard but the average coolant temperature is well below the boiling point (including the effects of a pressure cap).

The swirl tank acts as a centrifuge, keeping the heavier material (coolant) to the outside of the tank and the lighter material (air and steam) to the center and top of the tank. There is a 0.10 inch diameter hole drilled in the top center of the tank for the air/steam/coolant to bleed off. A 1/4 inch diameter hose takes the air/steam/coolant to the header tank. A typical swirl tank is show below. This method is also used to "de-foam" oil.

New Fiberglass Doors (Steve Mahoney):
Finally got to inspect Steve Mahoney's new fiberglass door at Arlington. The door was made by laying up 2 layers of glass on a flat piece of Plexiglas, a 1 inch thick piece of "builders foam" (blue is OK if you use epoxy) with the window area cut out, a couple of layers of glass over everything, and then everything vacuum bagged. There is a map and pencil pocket along the lower part of the door that also doubles as an arm rest. The door is hinged along the top and has a two point latch on the bottom (details in next NL).

The stiffness of the door is fantastic with the sandwich construction, the long piano hinge, and the two point latch on the bottom. Steve says that there is a large decrease in wind noise (and he has only done one door yet). He is using an automobile "lift gate" strut to hold it open.

He has flown down the runway with the door in the open position and has not noticed altered flight characteristics. Just envision a 200 mph Cub! He doesn't know yet what would happen if you unlatched the door in flight. It probably is the only BD-4 that you could actually bail out of in full speed flight! There are others who are hinging their doors at the top but I don't know of any that have flown yet.

New "Angle & Gusset" Type Airplane (Elwyn Johnson):
Elwyn is the owner of Northwest Aero Products (206-735-5022), the manufacturer of HTD belt PSRUs, and has developed 3.8 liter Ford and 4.3 liter Chevrolet engines. He has been testing his Chevy engine in a Cessna 172 airframe and being a reasonable man, thought that the FAA would be reasonable too. Of course you know how that turned out! He is now firmly in the homebuilt arena and is designing an airplane that uses the simple construction methods of the BD4 but that is optimized for auto engines and floatplane operations. The airplane will have a bit larger cabin, a strut braced wing spar, will have a new wing, and a much improved flap system.
This wing could be good for fitting on a regular BD-4 for those of you who want slower landing speeds.
The new airplane is just being designed at this time and there are no details available yet from Elwyn, however he is in full production of the engines and PSRUs.

A Death in the BD-4 Family:
Steve Takes passed away on October 23, 1994. Steve and his wife Lou have been a visible and active part of the BD-4 family for many years. Steve completed his airplane and flew it to Oshkosh a few years ago. The airplane was really beautiful with leather seats and wood trim around the windows. Steve was a veteran of WW II, Korea, and two tours in Vietnam. He served as a Command Pilot and a Fighter Pilot.

Steve was a kind, thoughtful, articulate man who will be sorely missed at our gatherings. Lou passed away a few months after Steve.

Steve's airplane was purchased by Scott DeGaynor who already is a BD-4 owner. He expects to use the airplane as a demonstrator for starting a BD-4 kit business.

Cowl / Cooling Tests:
Some problems that we experimenters run into can really be tun to solve and it really impresses the "spam can crowd". The new cowling for the V-6 powered BD-4 was designed (guessed) so that the cooling drag was minimal and the cooling just sufficient for cruise conditions. 75% power cruise is now possible if the OAT is below 50° F. Temperature rise at higher power is slow and can be controlled somewhat by running extra rich (it works for the air-cooled engines!).

A larger radiator would probably be most experimenters first guess but this radiator was well proven with my previous "ugly" test cowling. A 6 mile taxi at Oshkosh with 90° F temperatures proved sufficient taxi capability.

A water manometer was used to determine just where to begin work to get better cooling for the hotter temperatures. This method is also good for determining if you have enough pressure head to cool your Lycoming. The following figure shows the method used (the manometer has to be a maximum of about 12" long).

The small plastic tubes from Boeing's wind tunnel were routed through the cabin heat box and into the engine compartment. The plastic tubes were taped:

  1. in the ram air plenum above the radiator
  2. bottom of the cowling, outside of the air exit ramp
  3. below the radiator, inside the air exit ramp

The tubes are taped so they lay 90° to the flow of the airstream so that no ram pressure is measured. It would be better to connect them to a tiny hole in the surfaces but that is harder to do.

Test data was collected in 100 mph (ind) climb and at 160 mph (ind) cruise at 4000' mat. A ruler was simply held against each pair of tubes to measure the difference in water height.

As show in the figure, a moderate pressure was measured above the radiator. This indicates that either there is not enough air coming in the inlets or the radiator (or leaks in the baffles) flows air easily. The pressure under the radiator is somewhat lower than above the radiator but is much higher than static (right tube lower than the left). The pressure just behind the exit ramp is lower than static (right tube higher than the left). These last two measurements indicate that the outlet area of the exit ramp (3.25" x 20", total = 65 square inches) is probably too small. The air inlet holes have a total of about 50 square inches of area. The rule of 1.4 to 1.5 times more exit area is not being followed.

The modifications that resulted from the testing are shown below:

Vertical Card Compass
The last trip to Oshkosh was quite without a magnetic compass. For some reason, the compass on my BD-4 always seems to have a resonant mode at about cruise rpm (mounted at the top of the windshield). It would vibrate so badly that it had to be stabilized by hand for several seconds so that it could be read. There was up to a 45° error when it was vibrating.

It could be stated here that "those air-cooled flat fours" really run rough but the truth is that the compass also vibrated with the V-6. The propeller "beat" against the airframe probably was the culprit. It finally vibrated so bad that metal shavings clouded the kerosene and it could not be read until a half hour after landing.

It would not do to buy a new compass until the "problem" was solved. "Top of Panel" mounts are not attractive as the compass is more affected by the variable electrical load being consumed by the avionics. It would be possible (but not pretty) to brace the top of the windshield to the spar - but first do a flight test with a new compass.

The vertical card compass seemed like a better mouse trap (I now have more money) as it is easier to set the DG from something that has the same format face. The installation was easy and the flight test went perfectly - no vibration and accurate readings maybe its that new 3 blade Warp Drive prop?

Rocky Mountain Instruments Engine Monitor:
The installation of an auto engine leads you into a lot of related problems. The pressure and temperature sensors on an auto engine are not necessarily the same as those on the ancient airplane engines we have gotten used to. Not that airplane engines are easy either. You cannot go down and ask for an EGT probe without knowing just what type of bi-metal sensing element your meter is calibrated for.

The use of the engine instruments already in the BD-4 seemed like the right solution. This involved trying to find sensors that were mechanically correct (size, insulation, threads per inch) that also had the correct electrical characteristics. It is really fun to walk into an auto parts store and ask to look through their coolant temperature sensors. They usually demand lots of information about the "car" the part is needed for. At times I have tried to hide that fact that I am dumb enough to put a car engine in an airplane but in the long run it is best to confess up front. I have been allowed behind many counters and allowed to roam freely in many auto salvage yards once I confess. Most people are very interested in auto engines in airplanes (what do they normally use?) and when they know you build and fly, you almost attain the status of super-hero (especially when you mention the hairy flight tests you are in for).

After striking out in trying to use the instruments already in the BD-4 there was nothing to do but to buy auto instruments. There were many choices (digital and analog) and the prices were not too bad. Almost always the instruments have a chromy-auto-teenage-hot rod look that bothers me. After all we engineers do have our code to live by!

I ended up with several digital instruments (that were hard to read in sunlight) that really filled up the panel. A diesel tachometer was found that had the right look and the right range (it is irritating to have a tachometer that goes up to 12 grand when the engine will never see 5).

The first many hours of test were flown using the auto instruments but they were scattered all over and they really looked bad. The search for something better was started. The Vision Micro system instruments are nice but all my cars together are worth less than one of those! I went back and re-read articles on the Rocky Mountain Instruments (RMI) products. The RMI engine monitor is a small micro-processor that measures time, rpm, MP, volts, amps, all temperatures, all pressures, fuel flow, fuel left, and a few other things. It also has alarms that flash the reading that is out of tolerance and will send a "beep" to your intercom.

The $850 to $1000 (kit or built) price seems high at first but when you consider what instruments it replaces, it is really reasonable. The kit turned out to be really first class, the instructions easy to follow, and the factory support was excellent. The only question that remains: do you keep all the mechanical instruments as back-ups for this RMI "computer"? Think about it - if the RMI were to fail, could you get back down to earth? Well, all the old instruments went on the shelf and after two years I couldn't be happier.

The day-time and night-time viewing is excellent, the alarms are a must, and everything is in one small package that can be mounted right in front of you in the lower panel of the BD-4.

Mike D'Amico has found a good place to buy Pro-Seal. Seal Pak, Wichita, KS, Ph: 316-9426211. The brand name is Chem Seal and the product designation is CS3204. The class A sealant (30 minute and 2 hour set-up time) sells for $145.59 per gallon for 1 to 3 gallon quantities and 136.46 per gallon for 5 or more. The class B sealant (30 minute, 2 hour, and 4 hour set-up time) sells for $155.26 per gallon for 1 to 3 gallon quantities and $132.00 per gallon for 5 or more.


Tim Grizzle (3640 Bills Rd, Blairsville, GA 30512 (707) 745-7581) Would like to buy a BD-4 kit.
Jerry Bradshaw (208 Lisbon St., PO Box 820, Clinton, N.C. 28328 (910) 592-8166 days, or (910) 592-4480 nights) has two fuselages, one set of metal wings (flush riveted), all plans and DI's, newsletters, and parts to complete minus engine and instruments.

Errol Severe (Rt. 4, Box 416, Eureka Springs, AR 72632 ???-253-9471) has his 160 hp BD-4 for sale. New comfortable seats, full of radios and instruments, constant speed prop, extremely nice. $29,500

M. Lee Wachs (PO Box 280, Talmage, CA 95481 (707)-463-0467) has a set of BD-4 landing gear legs.

Glen Dickenson (707-839-3593) has two Murphy type nose-wheels, two engine mounts (1O-360, O-360), and a spar center section.

Mike D'Amico (2401 S. Apple St., #A 103, Boise, ID, 83706, 208-389-1204) wants to buy a taildragger

Kenney Houseman (5404 Wedgefield, Granbury, TX 76049) would like to buy spars.

Cory Lange (713 - 131 st Ave. N.E., Blaine, MN 55434, Ph: 612-757-8871) would like to by a BD4. He would also like a ride.

Mark Johnson (4542 W. Ave. M-4, Quartz Hill, CA 93536, Ph: 805-722-8141) would like to buy a BD-4.

Bill Wallace (4376 Northgate Lane, Carson City, NV 89706, Ph: 702-882-5505) is interested in buying a BD-4. He would prefer building the wings himself but is open to options.

Jerry Grove (233 W. Buchanan Rd, Apt 195, Pittsburg, CA 94565 Ph: 510-689-8469 or 510-4329059) would like to buy a "How to Build Your Own Airplane" book.

Source for aluminum wing ribs:
Long Aviation (912 Summey, Wichita, KS 67217 316-522-1697) is selling wing ribs. The ribs are $24.95 each, the spun collar to fit to the spar are $13.95 each. I have been told that the quality is excellent.

Robert Bollinger (2000 N 4 th St., 12-i, Fairfield, IA 52556, 515-472-0598 evenings, 515472-7000 (extension 4563) days) has a Javelin PSRU, 1.6 to 1 ratio for a 3.8 Liter Ford V6. Run only 10 hours. $2100.00 + shipping. Aymar-Demuth wood propeller 70 X 68 for the engine above. New with free re-pitch, $595.00 + shipping.

Ray Ward (8607 Southwest Freeway, Houston, TX 77074, Ph: 713-777-0133) is interested in a metal wing kit. He will buy all or just the rear spar.

Jerry Grove (233 W. Buchanan Rd., #195, Pittsburg, CA 94565, Ph: W 510-689-8469, W 800-5580040, H 510-432-9059) builds aircraft and components for a living. Prices are reasonable, the work is top-notch, and he offers a lifetime guarantee on anything he builds.

Jerry would like to buy a "How to Build Your Own Airplane" book.

Doyle Thibert (PO Box 464, Glide, OR 97443 (503-496-0128) would like to sell: Spezio Tuholer 90% complete, in silver for $6000 with midtime )-290 D2 engine or $4000 with disassembled O-290 G. Also miscellaneous Continental and Lycoming engines and parts. Call for more info and prices, will consider trades.

Wing Spar Strength: by Steve Mahoney
Enclosed are three color photo copies from the finite element program Rasna (HP's version). The version we have does not contain buckling analysis (costs an extra $11,000) so I'm not sure how much of a difference that would make. The program only operates in the linear world so what this means is the results are only valid in stress levels below yield. We ran this on the most powerful, fastest computer we had in our lab, a HP 735 and it brought it down to it's knees so we had to compromise and reduce the mesh size to get it down to something that would run overnight. In order to simplify the problem we assumed the cabin spar to be rigid as well as the extension. The program was set t look only at the compressive side of the wing spar.

The results are not all that amazing. The standard wing the way Bede designed it loaded to 5454 lbs results in a maximum stress of 50.1 ksi. This exceeds the yield point of the material by about 8 ksi approximately one diameter from the end of the cabin spar ..... not bad.

The long wing without cabin spar extension however exceeds this by quite a lot (76.4 ksi). I don' know how comfortable I would feel about flying around in along wing BD at 2200 lbs.

Extending the cabin spar 11 inches yields almost the same maximum stress level (56.0 ksi) as the standard wing without the extension. Not too surprising as the center of lift moves out 10.8 inches so the bending moment would be about the same.

In conclusion: I didn't really learn anything new, but these color plots look real cool and are impressive.

PS: I had a great trip back from Oshkosh. I added up all my fuel receipts and found that the BD got 20.8 MPG including the speed race with Scott DeGaynor. Dad got about 18 MPG in his Mooney. I think my electronic spark advance really helped. sm

Assume: 2200 Lbs Gross Weight
Fuel: empty
Fuselage lift: 12% of load
Safety margin: 1.5
Loading: 3.8 G                (3.8)(1.5) {(2200/2)-(0.13 x 2200/2))= 5,455 lbs

Another "Angles & Gusset" Airplane Project (Scott DeGaynor):

Scott has been negotiating to buy the BD-4 business from Jeff Bede. I am not sure just where things are going but he is very serious about the BD-4. He is contemplating buying a large number of spars and supplying fuselage angle kits so people can get started (buy the plans from Bede). He expects to add other items as time goes on.

He is also thinking about designing a new airplane that will greatly surpass the BD4 in looks and comfort but will still retain the ease of building. Scott has a large facility that may become a "builders center" where the entire fuselage can be constructed with-in a very short, enjoyable summer vacation.

The A & G type of airplane may be a bit dated but there are so many people out there that like the simplicity, strength, and frugality of this type of construction.

A Really New Type of Aircraft

I am now working on an unmanned, autonomous, high altitude reconnaissance airplane called Dark Star. It will be flying in a couple of months and I will be integrating a radar onto it before the end of the year. It has greater than 8 hours on-station, an airspeed of greater than 250 knots, can loiter above 45,000 feet, is very low observable and carries a Synthetic Aperture Radar or an Electro-Optical Sensor. The plan view is: