October, 2007

We plan to host a builder's workshop in Tucson between Christmas and New Years Day, 2007.

Some "Daffy-nishuns"

Dave Christensen's conventional gear Marathon--great design innovations and workmanship

In our last newsletter we covered Gary Rene's fixed-gear taildragger, and here's another fine example of the same type. Builder Dave Christensen sent email updates and photos of his Marathon project that we were unable to squeeze into our last newsletter, so here goes:

Dave Melby and others innovate as they build. And here are some pictures we promised last month!

Last month we promised to show you more photos of Dave Melby's design innovations. Here are a few of his breakthroughs.
Yes, you can replace control sticks
with yokes. Just ask Dave Melby! One of the big changes Dave Melby has made is to install a pair of very attractive control yokes rather than stick controls in his first Cavalier. Looking back at the picture that I took last June, his yoke controls just look like they belong. While both types of controls have their friends (and their enemies), let's suffice it to say that you can go with whichever one suits your fancy. Hey, it's your airplane, right? Made for you, and not for someone else?!
Melby's simple yet elegant method of hinging his gullwing type entry door on the Cavalier.
Some time ago I was working on a design for a gullwing type door. But I got bogged down as I struggled in my mind with a good way to hinge it on top. It never occurred to me to do it the simple, effective way that Dave Melby handled this, as shown in the above photo. Why of course! "We don't need no stinkin' hinges!" Just a couple of pins collared into those solid cockpit bows and you're all set! (Now why couldn't I think of that?) But there I was, stuck in my paradigm of having to fabricate some type of external hinge. It would have to be sturdy, maybe machined aluminum? And then of course since it would stick up in the airstream, I should devise a means of recessing it into the fiberglass, no? I would guess that, by the time I had "engineered" all of this in my mind, my assembly would be about ten times as difficult to fabricate, and maybe four times heavier, than Dave Melby's simple door pivots. Maybe Tony Bingelis had covered this in one of his wonderful sportplane builder books, I don't know, but it just makes so much sense! One of those things where you hit your forehead and say, "I should have thought of that!"
Cable-to-control-arm translator for rudder (gray piece just below the large tubing)
Another cool idea is Melby's rod control to the rudder. His rudder cables end at the bellcrank shown above, onto which a control rod end is bolted. The rod then extends back through the fin spar to a single rudder horn.
Rudder control rod comes through a hole in the back of the fin spar.
This last idea (see next column) is a little harder to visualize because the part that I photographed is sitting up on a shelf behind Dave's airplane. What we're trying to convey here is a way to secure your horizontal stabilizer to the fuselage frames that allows for adjusting, if necessary. The stabilizer is mounted at a slight negative angle of attack, a degree or two. But if it's glued in place you're stuck with it, whether it's a bit of nose up or nose down trim, as a result. By allowing for fasteners to be put into the stabilizer spars, you can change your setting up or down as you wish, to trim your airplane perfectly.
Horizontal stabilizer has receivers for screw mounting rather than gluing it onto the fuselage bulkheads.

More right rudder? Or more right thrust? What'll it be?

In our lead article about Dave Christensen, he mentioned that he is going to install his engine canted to the right a bit, to account for the left-turning tendency (p-factor and all that stuff). Some of you may wish to handle it that way. Others will want to effectively build in a couple of degrees right rudder by moving the leading edge of their vertical stabilizer to the LEFT. (You could do the same thing by canting the rear part to the right but that's a little harder to do.) The good news is, you can do it either way. It doesn't make any difference at all. Just don't forget to do it, one way or the other, or you'll always have to hold right rudder for the rest of the years you fly your airplane, even when straight and level!