Issue 3, January 1982

Dear BD-4 Builders,

Another Oshkosh is over and it was fantastic! There were a lot of BD-4s there and too many new mods and ideas to remember. I wish we could all get together more often and get to know each other better as I really enjoyed meeting everyone.

I've been delaying this newsletter as Don Hastings (Arizona) and Scott DeGaynor (Michigan) have been trying to get a source for spars. Don was told that Reynolds Aluminum can't produce the wall thickness we need and Scott is still trying. A lot of people need spars to finish their airplanes and several people said they would build a BD-4 if they could get them.

Some local people are having trouble getting the original style BD-4 wing tip. The wing tip that Ratray sells is a simple symmetrical T-18 style tip and just does not look the same. We decided it would be a good idea to make a set of molds from a set of original tips. Bob Sutton volunteered to send his unused tips but I found a perfect pair right here in the Northwest from Steve Mahoney who purchased his partially finished BD-4 from Phil Rabb. Thanks for offering Bob but this way we will save the postage.

We have a lot of BD-4 activity here in the Northwest. The story they tell here is that it rains so much you can't fly anyway! Rick Hatcher, Fred Hinsch, and Eric Munzer have a lot done but haven't set a final date. Dave Dotson and Steve Mahoney should be flying in early summer and I should have my new 7075 gear and fiberglass fairings on soon. Darrel Brown sold his flying BD-4 to Duane Roberts who is rebuilding the metal wings, converting to conventional gear, repainting, and putting in an IO-360 engine. We had to make a new extended motor mount to take the long intake manifold, which is mounted on the rear of the engine. We did an estimated CG and because of an originally heavy tail, the empty CG comes out OK with the engine four inches forward of normal. Has anybody else had to do this?

We all get together regularly to help each other and to brainstorm. We hope to have a Northwest BD-4 get together at the Eric Munzer residence in Langley, B.C. sometime this spring. It will be a bring your own bedroll and goodies type of a one nighter. I will get the date to you later.

We are planning to do tuft testing and a very careful flight test on my airplane later this year to try to determine how to make the BD-4 faster yet. We will keep the videotapes in case anyone wants to see them. I have access to a Boeing flight test, data reduction program so we should be able to get some good numbers for BD-4s

The Northwest EAA fly-in and campout was fantastic this year as usual we only had a little rain. This fly-in is the largest homebuilt classic, and antique get together up here. We had four BD-4 there: Armstrong, Mellema, Powers, and Roberts. We also had three current builders there: Dotson, Hinsch, and Munzer. We gave rides and also did formation fly-bys including some at over 200 mph. As usual there was a lot of interest in the BD-4 design and we had a lot of fun talking to interested people. By the way, this fly-in occurs every year at the end of August and is held in Arlington, Washington.

I received word that Richard Hewitt took his wings apart and found the 2216 was in very bad shape. There have been other reports of this but I have never seen it personally, It is so hard to judge whether or not the 2216 or the builders are at fault. It is very important for the epoxy to be fresh, the mixture to be correct, and the surfaces to be clean. It is also important which type of fuel (additives) is being used in the tank. The only trouble I have had is with the peel strength. I put two inch fiberglass strips over each wing joint so my trouble didn't occur there. I epoxied the skin on the doors with 2216 and the constant vibration against the frame caused the skins to come loose in a couple of places.

A lot of builders seem to be extending their wing to bring down the wing loading and it has been bothering me some. In Canada this is necessary and the BD-4 is limited to a two place so I don't see too much of a problem there. Here in the States, I know that some BD-4s have been flying at high gross weights with the long wing option. Bede put out a wing loading chart with a Welles line for cabin/fuel load, which is included in the newsletter in case some of you haven't seen it. The standard high wing loading bothers me some too but with the long wings the bending moment on the spar is increased quite a bit and I'm not sure I want to fly at 2200 lbs in moderate turbulence. If Bede came out with some later information on this please let me know.

The difference (distance) between the Load Factor Lines and the Welles Line is the advantage, in terms of fuselage loading, of starting with less fuel. In the example shown, 35 lbs more can be loaded in the fuselage with 20 gallons as can be loaded in the fuselage with 57.6 gallons. If the Welles Line was drawn in for the 3.8 g loading starting at 57.6 gallons, you would see that 100 lbs more could be loaded in the fuselage with 20 gallons than with 57.6 gallons.

Russ Huffington who crashed his BD-4 at Dekalb, Ill airport shortly after Oshkosh 1980, died recently. He suffered some head injuries and them later had a stroke. We here in Seattle will miss his friendship and advice. The crash was apparently due to carb ice. His wife Ann is at home and adjusting nicely.

MURPHY METAL WING

Here are some tips on making a wet wing.

Make all joints fit as close as you can without distorting the outside skins.
Most joints such as leading edge of ribs and trailing edge can be caulked with 1422 B2 PRC Tank Sealant. There is little reason to worry about gaps as large as 0.030 in., as long as you can reach them after the tank is ready for pressure testing.

Do not skin the outer panel of wing until the tank has been tested by air pressure as follows.

Make a loop of polyflow or equivalent with a gage in the center of the loop that will read in 1/4 lb increments or less (example 1 division = 1/4 lb). An old fuel pressure gage will work fine. Most of them have a range of 0 to 5 psi.
Make an air pressure line to fit the fuel tank vent fitting with a valve between the air pressure source and the wing tank.
After all obvious leaks have been caulked, pressurize the fuel tank with a maximum of 2.5 psi, and watch for an indefinite time, varying only with outside air temperature. If this process cannot be held use soapy water to find any leaks and repair as required.

DO NOT SKIN the outer panel of the wing until the fuel tank has been tested and found to be free of leaks. This has been the number one problem with builders of the Murphy wing for the BD-4.

N486JM is going on 8 years as of Oct. 1980 and has never had a leak. Based on tach time that means we have carried 8,000 gallons of fuel and never spilled a drop. Not too bad for pop rivets and PRC We are sure you can do the same if you really try.

NOTE: Use inch rivet spacing on all outer edges of fuel tank including, trailing edge channel. Dip each rivet in freon or chlorthane before dipping in tank sealant. After rivets are cleaned pick up rivets with a magnet by the stem and dip them, thus avoiding any contamination prior to applying tank sealant. Ribs, spar and skin should be cleaned with detergent and rinsed with distilled water. Apply a wash of alodine chemical film and rinse with distilled water. Do not zinc chromate fuel tank, ribs or skins inside of fuel tank. Do not use slosh of any kind to plug leaks in the tank area, find the leak and repair with 1422 B2 as required.

RUDDER CONTROL by Jim Murphy

The control horn is too low and has a binding action. It should be set as high as you can get it so as to be closer to 90 degrees to the hinge line. Add some pulleys to align the rudder cables. This eliminates that awful sawing sound when the cables run through the micarta blocks.

1) Tailweel installation by Hewes.

2) This is the strongest method but also the heaviest. It is nice because it doesn't get in the way.

3) This is the lightest and has been good for 300 hours so far with some very heavy tail loads. Good for retro-fit.