Taking the T-pins out, I made an interesting discovery this morning. It may explain why the Perigee has the reputation of falling out of the sky on landings. Of course, I had the wing weighted down so the rib tabs were all well seated. Once the top sheeting is on, you would think the wing would be rigid and maintain its shape, right? WRONG!

When I took the tip weights off, the LE at the tip rose up about 1/8 inch off the board. If I didn't notice that, and sheeted the bottom, then the wing would have wash-in at the tips. This surely would cause bad low-speed behavior.

When I stacked up the ribs, I very carefully measured them to make sure there was no wash-in or out, and that the wing would build true.

But now, the question is "why?" Why would the LE tip rise up? The answer lies in the lay of the grain of the sheeting. Conventional sheeting puts the grain parallel to the LE of the wing. That way, it curls to the airfoil with the least resistance. Tom Brett chose to move the grain diagonally, for increased rigidity. However, now with the wing only sheeted on the top, the tendency of the grain (long direction) is to straighten out. If built like normal, the long grain is already straight, so there is no bending moment. If you think about it, it's like having your fingers slightly bent, then straightening them out. If course, once the bottom sheeting is on, that will provide a counter-acting force.. IF it is applied with the wing jigged to be true, that is.

I believe this is what caused the Perigee to have a reputation as a hot plane, and why some people swear it handles just fine.

The more I get into building this plane, the more interesting it becomes.......