Advice on two-piece door construction

[szicree]

I've got a Super Sport, but I opted to do a two-piece door with a plexi top and fiberglass lower skin. Unfortunately the manual only describes the one-piece type. My main question regards the joint between fiberglass and plastic. The 'glass has a joggle to accept the plexi and even has what appears to be marks for holes. If I line the fiberglass up with the door frame it looks like this line of holes will end up slightly above the horizontal crosspiece in the door frame. Is this correct? Should the glass or plexi attach in some way to the cross piece? Any advice or pics would be much appreciated.

[Dave S]

Hi Steve,

I am not real sure the indentations on the fiberglass mean anything.

The line of rivets is centered on the crossbar; and, the joggle between the fiberglass lower panel and the window have to overlap on the crossbar. The rivets go through the window - through the fiberglass and into the crossbar.

I have attached several photos - may help some. Remember that all of the fiberglass parts are oversized and require some trimming. After the trimming is done on the fiberglass there is only 1/2 inch of overlap - right over the 1/2 inch crossbar. On one of the photos you should be able to see the cutout of the lower panel to bring the fiberglass edge even with the upper part of the crossbar which leaves 1/2 inch of joggle on the fiberglass lower panel for the window to overlap the fiberglass lower panel so the rivets can go through all three parts (window,fiberglass, into the crossbar).

Sincerely,

Dave S

[War Eagle]

I used the bubble doors on my bird but I helped build many others that used the same door covering you have chosen.

You will need to trim the fiberglass panels so that the joint between the two panels can be riveted to the cross member on the door frame.

We used countersunk rivets so we could make the outside surface finish smooth. Many people used alum rivets and then filled/covered the rivet with bondo. However, with the flex of the surface many of the rivets started to show through the outside finished paint after a year or so worth of flying.

Probably would be a better choice to used an epoxy fill (something that bonds to the rivet and the fiberglass etc.). This will take a lot more work but would not pop off over time and begin to show the rivets.

Here are a few pictures that may help visualize the process.

[szicree]

Great info and pics! Thanks a bunch guys. So here's a follow up question: The welds on the door structure prevent the skin or plexi from lying flat. Do folks grind the welds down? Also, any advice on hole spacing for the rivets? Thanks in advance.

[Dave S]

Steve,

While it is entirely possible to weaken the welds by grinding too much - I did grind off the high spots on the door frame welds which held the skin off. Easy does it if you decide to go this way - The aluminum welds are beaded up quite a bit and I don't think taking off a little on the high spots will reduce the strength of the welds. A little light grinding made things fit together well. I considered the possibility of grinding too much and figured the only thing I would have to do was get it welded again - but it never happened and worked out well.

I spaced the rivets approximately 2 inches apart on the door frame. A person can measure across the frame and figure out if it needs to be changed + or - a bit make the spacing even over the length of the tube frame so it looks nice.

Another thing to keep in mind - the polycarbonate expands and contracts a bit with temp change - it is a good idea to re-drill the POLYCARBONATE ONLY to 5/32" after everything has been drilled with the 30 gauge drill - JUST THE POLYCARBONATE - NOT THE FIBERGLASS and NOT THE ALUMINUM DOOR FRAME. The little extra relief on the PC will help prevent cracking out of the rivet holes over time.

Sincerely,

Dave S

[szicree]

Dave and W. Eagle,

Excellent info so far. John McBean sent me copies from the -6 manual today so I think I've got a clear picture of the whole deal now. One remaining question: The manual and your photos seem to show an aluminum strip sandwiched between door structure and skin/poly. I'm assuming this is not needed on the thicker one piece doors, but is on the two-piece type. The manual says to make it out of some supplied material. However, I don't think my kit came with this. I live close to Aircraft Spruce so it would be no big deal to get it if I knew the material and dimensions. Anybody have this info??

[jdmcbean]

Steve,
We should be able to get some to you.. otherwise I can get the dimensions you need. It is not with the SS kit.

[Dave S]

Steve,

What you are looking for is part number 12915.000 - door frame reinforcing strip - should be part of the kit for the two piece door skin. The strip is aluminum 1 inch wide, 0.048" (or close to 0.048") thick. Don't have the measurements for the length; but the kit called for 7 pieces all the same length (whatever the same length was).

Sincerely,

Dave S
KF 7