BD-4 BUILDERS NORTHWEST
NEWSLETTER
Issue 7, March 1989


Dear BD-4 Builders and Owners,

Summer is getting very close - - do YOU have YOUR BD-4 ready for all of the fun fly-ins? I always seem to plan to do a lot of fix-up and also neat new things to my BD during the winter months. However in these dreary dark days I find it very hard to rush out to the garage or to the airport right after dinner and get to work. I usually find myself sitting on the couch alternately dozing and feeling guilty about not getting anything done. I hope to make it easier to work on the airplane in the future - we just bought a lot on Crest Airpark and will be starting to build soon. I dream about flying to work but the dark, rainy, foggy weather and high priced and unavailable tie downs will no doubt stop me. It is a real shame as Boeing Field is about three blocks from work. Maybe a BD-4 Aero-car?
Nah, it might slow it down a little . . . . . . .
                                                                                 rdm

NORTHWEST NEWSLETTER DUES

This newsletter started out to be just for those of us who live in the Northwest but as you know it is now sent all over the US and several foreign countries. I think it is time to change the name of the newsletter as most of the members are not Northwesterners. If you have a suggestion for a new name please let me know. We will be having a meeting here in Kent, WA soon and will discuss it at that time.

In the last newsletter I told you that the money for postage was about gone. Many people have sent money since that time and all but one of these have sent $500. All dues in the past have gone for postage only but as the list of people gets longer, my free printing privileges might disappear and I may have to pay to have some done. Most of the postage was used to send newsletters but some was used for the many letters I write to answer specific questions that builders write or call about. Sometimes it feels like I must be in the business of selling BD-4s!!!

When you send in your dues for the newsletter, please update me on all the facts about your project. I am putting the mailing list and all pertinent facts on a computer to make it easier to keep track of everyone. I would like to know the following items: N number, BD serial number, engine type, propeller type, wing material, wing length, gallons of fuel, tricycle or conventional gear, completion date, total hours flown, empty weight, etc.

WHEN TO CALL ???

I've had many people call my home during the day wanting to talk to me. My wife doesn't mind the calls but it costs you money to call twice. I work for the Boeing Military Airplane Company and I can take short calls during the day. I work from 8:00 to 3:30 Pacific time and the number is xxx-xxx-xxxx. I can be reached at home from 6:00 to 10:30 most nights except Thursday and Sunday (xxx-xxx-xxxx ).

ARLINGTON, WA FLY-IN


The Arlington fly-in has been moved to the Bayview airport at Burlington, WA (northwest of Arlington about 25 miles because of crowd control and political problems at Arlington. The fly-in is now set for Aug 26-28. The fly-in is now by and for flying people only and as such should be more fun. Facilities will not be quite as nice but a lot of things will be better. Meals can be purchased at the fly-in. We usually have quite a few BD-4s there - lets see if we can get more.

AUTO GAS EXPERIMENTS

We have now used auto gas in my BD-4. I can't tell any differences so far except that the "o" ring in the gas cap did some swelling. To make it easy to fuel my airplane I am now using air pressure to pump gas from a 55 gal barrel. I don't have room in my van to use a hand pump. I pressure tested the barrel to about 10 lbs/sq in to be sure it could take the pressure. To pump gas from the barrel in the back of my van to the airplane wing tanks takes 2 to 3 lbs/sq in. I drilled a 5/8 hole in the small screw cap and brazed in an 8" piece of 4130 tube left over from my BD. I put a hose on the bottom that goes almost to the bottom of the barrel, and a 10 ft hose on the top. I drilled a hole close to the larte screw cap and popped in a valve stem for a tubeless tire. A small 12 volt aircompressor (JC Witney) has the exact air volume needed to pump out the gas at a 3 to 5 gallons/min rate while running:continuously. The hose of the compressor holds itself on the valve stem. Remove the valve core so that when you want to stop pumping, you just take the compressor hose off and let the air bleed off.

Be VERY CAREFUL and pressure check the drum as even 3 lbs/sq in of pressure exerts a tremendous force on the top bottom and side seems. A 30 inch diameter top will have (30/2)2 * PI = 2120 lbs of force on it. It is easy to get hurt if one blows up, not to speak of the fire hazard. If there is room to use one, a push pull hand pump works fine and is less dangerous.

Monroe McDonald wrote to say that he has been using auto gas in his O-360-AIA (certified for 91/96 oct) for two years. He uses a mixture of 75% super unleaded and 25% regular leaded as is recommended as a BMW motorcycle substitute for premium fuel. He has had no trouble except for replacing the plastic carburetor float with an old style brass float. On 100 degree days he has what appears to be some vapor lock problems. There is no problem as long as the engine is running but if it is shut down in the sun for 20 minutes or so it won't start without generous use of primer. He has also had the same problem with 100 low lead.

Monroe uses a two wheel trailer with a drum and rotary hand pump to fuel his airplane. He saves $28 on 40 gallons.

Jerome Borden wrote with these comments on fuel requirements:
  1. I asked the Lycoming representative at Oshkosh about derating curves for engines and he wouldn't give me the time of day.
  2. If somebody is sharp on engines and thermodynamics, they should be able to draw RPM/MAP limit curves for the various octaves from the data at hand. There would only be three charts for us since the engines we're interested in are certified for either 80/87, 91 or 100/130 fuel. I'd be willing to pay for them myself.
  3. Dave Blanton has a neat trick for detecting pre-ignition/knocking in engines. Attcah a phonograph pickup ceramic cartridge to the engine. The "new" sound will come through quite well. This idea also suggests an automatic knock-detector as well.
  4. Finally, I wouldn't assume that Avgas doesn't contain aromatic - sparticularly so in the case of 100 low lead. If you know of anyone with access to an infrared spectroscope detecting toluene, bsnzene and co. is fairly easy to do the test.

REDUCING DRAG

My comments about tuft testing and high drag areas got a big rise out of you readers. It seems many people are interested in getting more speed and making the BD-4 look better.

Jerome Borden (Colorado) wrote to suggent a "fence" arrangement (Figure 1) to stop the flow of high pressure air from the base of the windshield and over the sharp corner. This will-channel some air up rather than over but an airplane pushing through the air affects the air up to 4 or more feet in front of the surfaces. This means there will still be spillage over the "fence". The turbulence caused by this is worse than that caused by the small radius of the original angle as the"fence" has no radius.

Ray Ward (Texas) also wrote to suggest a "fence" arrangement (Figure 2). I told him the theory as described above but that you can't hurt anything by doing a test. He wrote back to say that the fence didn't work and that the cabin noise was worse. (A lot of cabin noise in a BD-4 at high speed is due to this turbulence) He also sent pictures to show his tuft tests. Ray then bent the "fences" in toward the center of the fuselage (Figure 3) so that the air that spilled had a large radius to flow over as it went around the edge. This restricted visibility some but it worked!! His tuft tests show a marked improvement and he said the cockpit was quieter. He also reports an 8-10 mph speed increase.

The mockup windshield I tried worked very well (Figure 4)., It gave an 8 mph speed increase and the turbulence on the side windows was some better than Ray's. The mockup wasn't as good as the windshield I now have made but have not fit yet. The windshield is 3/16" thick and has its greatest curvature at the bottom where the greatest pressure is and is flat where it ties to the top of the fuselage. The mockup lifted away from the fuselage at the top due to body lift. This probably caused a good bit of drag. The amount the top lifted away was very dependent on the Angle of attack as it causes the lift vector to move forward and back. A very interesting flight test - until some of the tape let go at 190 mph - just noisy but sure causes the pucker factor to go up!

A high power run (with the top of the windshield sticking up 1/2" or better) at 7,000 feet and 69% power gave a corrected airspeed of 198 mph. I still have not calibrated my airspeed but it is pretty close - even if it's 5 mph off I'm still going fast. No matter what the exact airspeed, I've been.getting faster with each new fairing and it really feels good.

I will be selling the windshields once they have been proven. I am going to try a 1/8" thick windshield also to see if it is strong enough. I don't like the weight increase of the 3/16" window. My supplier says the 3/16" window
will cost about $225.00 (packed and shipped and can be either clear or FAA approved smoke color.

ENGINE COOLING

In Figure 1 from Jerome Borden the idea for a cooling air inlet in front of the windshield might work but you would have to first find out what the pressure is inside the cowling. It could be high enough to force engine cooling air up and out at that point. A friend here at Boeing who is a cooling expert has been helping me understand engine cooling and a couple of interesting things came up.

  1. Engine air inlets can be larger than necessary and still not cause much drag as long as the edges of the holes have a large radius.
  2. As long as you have an air inlet for engine cooling - you might as well use this source for all your air, like: carburetor, cabin fresh air, (insulate the ducts), radio cooling, heater, defrosters, etc. He says this is even better than NASA air inlets.
  3. Carburetor ram air is a good thing as you can get more manifold pressure. The problem is the drag caused by the ram inlet. Quite often you end up burning more gas at the same speed. The overall advantages are quite small.
  4. If you want to use updraft cooling - exit air at the top of the cowling in an area of air stagnation such as in front of the windshield. The best place for an on-top-exit is about 6" back from the spinner.
  5. The air out let should be about the size on the BD plans. Very few people use the cowl flaps as they don't seem to do much. Bede later said to just leave the opening there. I've found that by putting a large radius edge on the fire wall (Figure 4), the cooling air flows smoothly along the bottom of the fuselage (more speed yet).

BD-4 GET TOGETHER MARCH 26 & 27, 1983

Fred Hinsch (Vancouver, B.C.) called the other day to say that he was having his Murphy wing kit sent to me (this makes it easier to get through customs) and that he would like a cowling ready by then too. I thought that as long as he was coming down anyway, we might as well have our sometimes annual get together. Everyone is invited - families and all. We can house quite a few people if you don't mind sleeping on the floor - please bring sleeping bags. We have a couple of available beds for those of us who are older!?! Please call if you will attend and if you need a place to stay. If you prefer we can make motel reservations for you. My wife has the menus all planned. Try to get here as early as possible on Saturday as most of the looking around will occur then. Bring along any aircraft items to sell or trade. Dress casual.

ENGINE STARTING PARTY

We attended an engine starting party at Steve Mahoney's place in McMinville, Oregon on February 26, 1983. We had an excellent attendance of several BD-4 people who had never met before. Two BD-4 s flew in - Mellemas and Del Kendrick (Lyle, Wa.)

Steve's engine was a vertical mounted helicopter O-360 engine that has been converted to a horizontal mounted aircraft engine. The only thing not standard now is that it uses a O-320 oil sump and induction system. The engine started easily and ran very smoothly but the alternator and some gauges didn't work. Don't get discouraged, Steve, I burned out 2 regulators before I got mine to work. Steve is using a fixed pitch prop on his O-360.

Steve's airplane is coming along nicely and he hopes to fly in about a year.

Those present (BD-4 builders) were: Steve Mahoney, Del Kendrick, Dick Cushman, Jim Parker and Colin Powers, and the Mellemas.

I had the pleasure of giving Dick and Jim a ride in my BD-4. They were surprised to see 180 mph (indicated) at 65% power.

Del Kendrick's airplane really looks good. It is very complete with all the fairings, radios, etc. The weather was pretty bad arid we didn't try any side by-side speed checks - maybe at our Bayview fly-in!

Colin Powers (who now lives at Independence Airpark, OR) drove up as he is repairing seeps in his fuel tanks. Maybe he will write an article later to let us know how it is done and how successful it is.

SAVE YOUR EARS

The BD-4 is not really more noisy inside than most airplanes. At 100 mph mine is very pleasant but at 180 there is a lot of noise. When I built this BD-4, I decided to save the weight involved in making it quiet - I'm not sure its ever possible with the flat metal and flat windows. I bought cheap headsets and built microphones for them. I built a simple intercomm and got everything working beautifully in the shop. When I put it in the airplane it was horrible. When we talked and broke squelch, there was this loud roar that almost totally blocked the voice signal. I then bought a David-Clark H 10-30 and found it to be better but still not nearly good enough. After some tests and study, I found that the H 10-30 has a noise cancelling microphone but it only cancels the lower frequencies. The high frequency wind noise was causing the problem. I then redesigned the intercomm so that it passed only the voice frequency and not the higher wind noise frequencies. This helped a lot and made the system useable. We now fly with each of us wearing an H 10-30 with boom microphone. My redesigned intercom has a very sensitive squelch and works well. I am making up 30 intercomms and will be selling them for $55. The intercomm will be a 2" x 4" printed circuit board completely wired up and will have a 12 pin connector. These are made to be built into an avionics system there is no box and no mic/HP connectors supplied. The unit requires a 12V supply at a very low current and is filtered for alternator noise.

Last week a friend talked me into doing a microphone/intercomm test (my gas, of course - all pilots are rich). We found the David Clark H 10-40 has a much better noise cancellation microphone than-the H 10-30. The Plantronics with the spoon was much worse than either. We checked my intercomm against 2 others and found that the 2 others apparently have no filtering in them. If your cabin is not too noisy and you use a H 10-40, they might work.

NEW MEMBERS/ADDRESSES

(deleted for privacy)


FOR SALE


Peter Hardine, Holland, Mich 616-392-3766 Has his airplane for sale. Murphy wing, tri gear, some instrumentation.
David Mansfield is selling his BD-4. There are no wings or Horizontal stabilizer. He is asking $2000.

Jim Londo, 9606 18th Ave W, Everett, WA 98204 (206-353-6156) has 3 Bede type wheel pants for sale for $175.

Scott Zimmerman (see address above) is selling his BD-4. This is an exceptional . airplane that had a lot of work finished on it. It has: countersunk rivets, extensive instrumentation, 0 SMOH engine, Hartzell C/S prop. Over 12,000 invested, make offer.

LETTERS

John Brecher would like some vickers donuts. John said he got some inertial reels for about $55 from WILCO.

Vat Slater wrote to say that a good lubricant for spars is MolyKote 2 powder from Dow Corning, Corp. Midland, Mich. 48640. Val is about 95% finished with his 150 hp BD-4.

SETTING THE AILERONS

  1. Position the aileron torque tube bl crank (CS-2C) no the forward end is 1/8 inch from hitting the top of the fuselage.
  2. Position the aileron to 17 degrees down.
  3. Drill the belcrank (CS-21) / aileron (W-3) torque tube so that the bolt can be easily inserted and so that it doesn't hit anything as it rotates.
  4. Center the "stick" (CS-1) and tie it so it stays centered.
  5. Adjust the side and the "back" turn-buckles so that the forward edge of the down pointing part of the aileron belcrank (below the rear of the door) is at 90 degrees to the floor. This is not the tapered part by the bottom
    bolt, but the flat spot above it. At this time the part of the belcrank that points to the rear x111 not be horizontal (the bolt that ties it to the push rod will be above the pivot bolt of the belcrank).
  6. With the sticks held centered, the vertical rods (CS-17) are adjusted so that the aileron deflection is zero.
  7. The ailerons should nor move upward about 24 degrees and downward about 17 degrees. These numbers were obtained from the HD-4 newsletters. They superceed the numbers given in the plans. Your airplane x111 not read exactly right but do the best you can. The ratio of down to up should be about (17/25) 0.68 . If it is a long ray off (closer to 1.00), it rill be hard to fly with the stick only. More rudder x111 be required for the adverse yaw due to the down aileron.
    The side turnbuckles can be loosened or tightened a little (both the same ray) to minimize the ratio. Perch time you try a different setting make sure the "back" turnbuckle is tightened or loosened so that the cable tension is the same.
  8. The aileron assembly has a pretty high friction and can cause difficulty during the first few flights (until you get used to it). Some of the methods used to reduce the friction are as follows:
    • Keep the cables loose (loosen the "back" turn-buckle). This might allow the ailerons to reflex upwards a little. Tighten each side turn-buckle a little to correct this.
    • Ream out the bronze bushing that fits in the torque tube/belcrank assembly. Some of us have taken it out all together. I found that most of my friction was caused by it.
    • Use ball bearing pulleys,
    • Use larger diameter pulleys.

LANDING GEAR LEGS

After the last newsletter several people wrote to ask about buying main gear legs like I made for my BD. I am not in the business of supplying this sort of thing but could organize &,group buy. The legs would be rough cut (with in 1/16") and bent but you would have to do the rest. You would have to cut the notch at the top (unless you use the solid link as shown in figure 5), file the edges smooth, polish the gear (7075-T6 is a little more brittle than 2024T3), and drill the holes. The gear can be made 2 inches longer for those with tail draggers. Many people are now using this type of gear and there have been no breakage or sagging. Many people are also using the solid link in the gear box (figure 5) instead of the donut and find it much better. The gear legs have plenty of flex and the donut is not needed. We probably could make the gear legs straight or with a positive arch as I have. I haven't checked on all of the costs yet but would expect it to be about $300 for a pair. If you are interested at all pleaselet me know and I will get a firm price.

Figure 1
Click on Image for larger view


Click on image for larger view


Click on image for larger view