Originally published January 1992
This is probably a familiar title for most of us who build airplanes, but I actually thought I was going to make progress. Well, it turns out I did make a lot of progress the first week and had to undo it the second week.
If you don't recall, I'm building a highly modified Corby Starlet called Excalibur. It's an all wood low wing monoplane with fabric covering on the wings and control surfaces. Right now, I'm building up the fuselage which requires making two spruce trusses and covering them with 3/32 inch birch plywood. These become the fuselage sides. Oh yes, I did make a left and a right side instead of two lefts. Finally these sides get fitted to the fuselage bulkheads and presto I get a wooden fuselage.
I made up the spruce trusses a few weeks earlier and all I had to do was cover them with plywood. The only trouble is that the fuselage sides are thirteen feet long by about two feet wide and the cold, dry winter months are about the worst time to work with the plywood. So I proceeded...
I covered the left side while the truss was still in the jig and built a heat tent over the assembly to keep it above 70 degrees all night long so the epoxy would cure. Then I reset the jig and did the same for the right side.
Then Norm Howell and I decided that it was time to build a loft in the hangar at Fox Field so we had a place to store our treasures of airplane parts and junk and stuff. One spin off of the loft was that it allowed us to drop a plastic curtain in the back third of the hangar and warm it up with Norm's Jet-A burning, 50000 BTU, after-burning, blowtorch of a heater. It took the chill off the work area and allowed Norm to progress with his Long-EZ rhino-plasty (more on that later).
A few days later while I was setting up the bulkheads on my jigging table we had the most evil rainstorm I've seen in months. When I looked at my beautifully skinned fuselage sides, I noticed the plywood had buckled. There was no failure in the wood and in fact it was still airworthy but I was convinced that these ugly, distorted skins had no place on my airplane.
It was time to consult Tony Bingelis. Right there on page 116 of his book The Sportplane Builder, Tony says, "Humidity, or rather the lack of it, can be troublesome. ...Plywood panels, if glued to a fuselage frame or wing panels, will expand at some future date when the humidity gets back to normal levels." So it turns out, my plywood got too dry while in the heat tent and I was going to have to recover my fuselage trusses.
This time I took a different approach. With Mike Pelletier's help we coated the spruce with a thick layer of epoxy before laying the new birch plywood in place and then we sprayed some water on the plywood to help raise its humidity. Then we put both sides in a vacuum bag to apply the clamping pressure (about 300 lb per square foot). And finally, we built the heat tent over the entire assembly to keep it warm overnight. (There's about 8 hours of work in this paragraph alone.)
The next morning when I opened it all up I found the epoxy glue line was even and nearly perfect due to the vacuum bag but we added a little too much water to the plywood. So I took the fuselage sides out of the vacuum bag and put them back into the heat tent at a little above ambient temperature to help dry them out.
The plywood ended up being drum tight and is now quite satisfactory. So in my two weeks of work I had accomplished a two day job and advanced to the next level on that infinite learning curve of aircraft building.
Now, about that rhino-plasty. Norm had decided a long while ago that the original Rutan style nose on his Long-EZ was really ugly. It had all the sex appeal of an eroded pyramid so it just had to go. A while back he converted the original nose to fiberglass and foam dust and started gluing new foam in place. With Mike Pelletier's help, Norm managed to finish attaching new foam blocks and carving the whole thing to a pleasing shape. Then they fiberglassed the entire thing. It really looks good and aerodynamic now although it doesn't match the illustration in the plans anymore. Since the Long-EZ plans set has the illustration below in the section on how to carve the nose on one's Long-EZ, I think Norm should've stuck to the plans--it'd give his plane some character don't you think?