BD 4 BUILDERS NORTHWEST
Issue 5, October 1982Dear BD--4 Builders and Owners,
Another busy summer of building and flying is over and it is time to get out all the information that I collected and that people sent me.
The only disappointing thing I have to report is that the spars are not selling very well. So far, the following have agreed to buy a set:
||M P Frisen|
||H Wood wants 11' 8" wing spars|
||H Crawford cabin spar|
We need 20 sets of wing spars and 38 sets of cabin spars before we order. The basic cost (not figuring tax, crating, shipping, etc.) is $663.00 for a pair of wing spars (6.810" OD by 6.410" ID by 10') and $188.90 for each cabin spar (6.400" OD by 6.000" ID by 5.5'). The two wing spars weigh 100 lbs total, the cabin spar weighs 26 lbs. The spars are made of 2024-T3 extruded, seamless, round tube. If you know of anyone who might need a set please let me know.
David Dotson (Renton, WA) flew his new BD-4 just before Oshkosh but couldn't get ready in time for such a long cross country. He has an O-360, C/S prop, conventional gear, and glass wings. He has the same paint scheme as I have and I of course copied Lloyd Brekke who adapted a Bellanca paint scheme to his BD-4 way back when. After some minor trim adjustments, Dave's IFR equipped airplane flies beautifully. We both have our airplanes at Crest Airpark near Seattle and find it fun to work together (they always seem to need something done) for a couple of hours (8 or 10) and then take our long suffering families to a nearby airport for lunch or dessert.
Dave started his airplane in a strange way. His wife Diane wanted him to go along to visit a shirt tail relative of hers (my wife) and he did not want to go until she told him about my airplane. I was about seventy-five percent done at the time and it didn't really look that good but he decided right then to get his license and build a BD-4. He bought a partially completed airframe in Montana about four years ago and completed it in July.
CANADA MEETINGAt the end of May the Canadian builders in the northwest invited everyone up for a weekend of hangar flying and an airshow at Delta airpark. Unfortunately because of some people trying to finish their airplanes and prior commitments, I and my family were the only ones able to attend. I waited too long to send for permission to enter Canada with an experimental aircraft (they need at least two weeks) and so had to land at Blaine, WA. Blaine is right next to the border and very close to where Eric Munzer lives, We had a great time looking at Eric and Fred Hinch's airplanes, attending an airshow, taking a tour of Vancouver, BC, and eating. Eric and Fred are both building Tri-gears with 150 - 160 HP engines and of course the long wings required in Canada.
Their workmenship is beautiful, and they make sure everything is just right. They are both close to finishing their airplanes and Eric said I could fly chase plane during his first flight.
We stayed at Eric and Susan Munzer's house during our visit and really enjoyed their Swiss/Canadian hospitality - especially the almond cake and breakfast buns. We had a delicious dinner at Fred and Elaine Hinch's house on Sunday evening and then we all headed for Blaine and our airplane. The customs official who passed us back into the US even found a replacement for a few minutes so he could come and see the airplane before we left - homebuilts sure are fun. After a 220 MPH low pass and a pull-up that made my wife get a bit over excited and my girls squeal, we headed home.
The next BD-4 meeting will be held in the Seattle area sometime next year.
I was really impressed by some of the new BD-4s at the convention this year. Next year I will do a better study of unique features and report them to you. The new airplanes seem to be better equipped and look better than ever and really attract a lot of people.
ARLINGTON 1982The Arlington, WA fly-in was the last weekend of August. All the BD-4 owners and builders in the northwest try to make it. as we have designated it as our fall BD-4 meeting. We had a good turn out with the following BD-4s in attendance: Glen Dickenson (McKinleyville, CA), Dave Dotson (Renton, WA), Roger Mellema (Kent, WA), Colin Powers (Corvallis, OR), and Duane Roberts (Buckley, WA). Builders who attended were: Fred Hinsch (Richmond, BC), Eric Munzer (Langley, DC), and Lyle Shelton (Fall City, WA).
We did not have any official BD-4 meetings but we did a lot of hangar flying. We also did a couple of formation fly-bys (we need a lot of work on our formation) and a lot of single plane fly-bys and pullups.
Colin Powers recieved an Honorable Mention for his beautiful tri-gear BD-4. This is really an honor for an airplane that has been flying for several years. Colin has a beautiful interior and a very neat panel layout with everything perfectly labeled. Congratulations, Colin!!
TUFT TESTSI have had the desire to do a complete tuft test on my BD-4 for quite some time. The BD-4s box like shape is not the most efficient as far a drag is concerned and I wanted to know just how good the flow is. I also wanted to know how good a job I did of designing the landing gear and wheel fairings. I arranged to do a tuft test with Geoff Sayers who desighed the Barracuda. We tufted both airplanes, loaded up camera crew and went flying.
The BD-4 has only two turbulent flow areas. One is very insignificant and occurs on the bottom of the fuselage, at the sides where the tail starts to slope upwards. There is probably no easy fix for this and not much is to be gained anyway. The worst turbulent flow is at the forward side window and extends to the rear across the pilot/copilot side windows. I guess I always knew there was a lot of turbulence there as that window vibrates a lot and I blew a couple out on my first BD-4. The reason for the turbulence is the high pressure area at the base of the windshield, some of which tries to flow to the side of the airplane. The sharp corner on the windshield causes this flow to be turbulent. At first I held the attitude that this is the price you pay for an easy to build airplane and we get a lot of speed and efficiency as it is anyway. After talking to a friend who has expertise in this area, we decided that a new windshield could be made that would:
- wrap around to or over the forward side windows,
- have enough lower bend radius (against the cowling) to eliminate the turbulence (front of windshield will be about flat,
- have only straight line (no complex. curves) bends of changing radius (small at the top and large at the cowling),
- have a flatter angle and so reduce pressure (drag) at the lower end,
- fit on the existing frame. except for extending the top of the firewall/instrument panel forward 6 to 10 inches and cutting the cowling to fit the new windshield,
- increase the cruise speed close to 10 mph.
HIGH COST OF FLYING?Most of us find it hard to justify an airplane that is owned by just one family. Usually the cost of fuel keeps us from really using it as much as we would like. One way to make it cheaper is to use auto fuel, but most BD-4's have an O-360 engine which calls for 100/130 octane aviation gas. The O-360 really requires only 91 octane and certain car fuels are useable. We are preparing to do some testing with super unleaded gas of 92 octane and will let you know the results. We will fill only one wing tank with auto fuel during these tests and will insulate all fuel lines in the engine compartment to help avoid vapor lock.
Another way to get more miles for your money is to properly fair-in your landing gear. A properly faired, fixed landing gear can get back 80 plus percent of the drag reduction advantage of a retractable gear. I just finished some very close fitting landing gear leg and wheelpant fairings and got a big advantange. Cruise is now at 186 mph, maximum speed at sea level is 191 mph. Dave Dotson and I have identical airplanes except for these fairings. We did some long distance flying recently and found that he always used 30 gallons to my 20 gallons. Dave is now busy using my molds to build fairings for himself. We will let you know how much his performance improves.
WINGS THAT DON'T LEAK?I heard a rumor that a new fiberglass wing is in development and will be ready soon. It is made so that a complete bottom skin can be bonded over pre-installed ribs, carefully fuel sealed, and then the top skin installed. Sounds like this will give the super flat surface that is necessary for laminar flow. The skins should be easy to finish too as a female mold will give a super surface that is free of pin holes. I think the Murphy wing is a good alternative to the BD wing panels but many people say they would rather have a glass wing so this should be good news to them. I will withhold names yet to keep you from bothering him and delaying progress.
COPIES OF OLD NEWSLETTERS
LETTERSStan Wilkin (Islington, Ont.) wrote to say that he put his landing gear on backward to unload the nose: gear a little. He also moved the engine forward by one inch so that the prop governor will clear the firewall.
Bernard Thalman (Wilmette, IL) wrote that he and his 4 partners just finished their BD-4. This is the first one I've heard of that is using a 165 Franklin six cylinder engine. They made everything easily removeable for easy maintenance. They have a lot of radio gear and the whole project was built for under $4000.
Joe Gauthier says the instrument cluster (cylinder head temp etc.) came from an early Cessna Cardinal. Joe also says he has the drawings of his tail dragger conversion if anyone is interested.
Some people have asked about wing extension plans. These plans are shown in the may 1981 Sport Aviation. The Bede wing extension plans used a 0.032 thickness wing spar extension. The Sport Aviation article was by Ron Smith, 6209 W Camelback Td., Phoenix, AZ 85033.
SPAR STRENGTHThe figure below is made up from the g limits as given by Bede. By using an elliptical lift distribution for the. wing, the center of lift for the standard wing is at 37% (49 inches from the side of the cabin) and 38% (59.8 inches from the side of the cabin) for the long wing (24 inch extensions). By using the elliptical distribution, the cabin lifts about. 13 % of the load. All of the various numbers given by Bede at various times, fit on this figure except for a 1400 lb static test that indicated a catastrophic failure at 12 g's. Bede claims that. the cabin spar is over-strength and that the wing spar fails by buckling just outboard of the cabin spar. The spar can be strengthened substantially by putting something on the outside or inside of the wing spar at this location that will prevent the buckling. Bede claims that in the 1400 lb test, the spar had no permanent deformation at 11 g's. Because the spar fails in the buckling mode, the figure on the next page is the best I can do with the information at hand and as such should not be relied upon as absolute fact. It does serve to show what happens when long wings are used with very high gross weights. At 2500 Ibs, yield begins at 2.7 g's, normal category requires 3.8 g's. When the BD-4 was first built, there was a problem with the spar to cabin strength. There was an analysis done on the strength of the modified cabin - if anyone has a copy of this, please send it to me and I will publish it.
After working through all of this, I personally would feel safe about flying with long wings as long as the gross weight stayed below 2200 lbs. I would sure be careful to avoid areas of extreme turbulence when heavily loaded. However, the heavier the wings are, the better the g loading becomes. It really helps to put your fuel in the wing tips (don't worry about landing wing loads as our circular spar gives us as much strength negative as it does positive).
BD-4 AIRPARKI received a letter from Ray Ward (Houston, TX) and he would like to establish a trophy for the "most, expensive" BD-4. He tallies up the cost of his recently finished BD-4 like this:
|Materials kit, new engine and prop||15,000|
|Hangar and shop space||35,000|
|3145 ft runway (Ward Airpark)||225,000|
It seems that when Ray got his BD-4 ready to fly, he was notified that
"homebuilt airplane:" were not welcome at Hull field where he keeps his Cherokee.
Homebuilders are used to being hit upon - so Ray didn't let it bother him,
he just went out and made his own airpark. Ward Airpark is located near Beasley,
TX. The layout is shown below. Every one-acre lot owner will be a member
of the civic club and will have non-exclusive use of the runway. One acre
lots were being sold for $20,000 a couple of months ago - contact Ray for
current prices. The terms are 20% down, balance 10% per year for 10 years.
Ever wonder what happened to the BD-7 project? During the Arlington fly-in
I was approached by Don Goetz (Portland, OR) who now owns the prototype BD-7.
He expects to fly in a year or so. When he bought the airplane at the bankruptcy
sale, a lot of internal items had been torn out for modification. His phone
number is 503654-2147.
David Hoisington called recently to let me know about his project. He
is going to use a converted Oldsmobile engine for a power plant. The engine
normally puts out 135 hp @ 4500 rpm. After changing the compression. ratio
and turbo-charging, he expects about 230 hp @ 3500 rpm. He expects the total
weight to come in at about what an 0-360 weighs. I intend to fly over to
see his set-up and will give you a report later. David lives near Newport,
During Oshkosh I was questioned as to why my gear has a positive arch and also how I changed my main gear box. The arch is to give a little more strength and the box details are shown below. The gear is now 7075-T6 aluminum.