Another Door Mystery

[Larry Lyons]

Re: Another Door Mystery

OK my "41" ser. # 2540 is steel tube, covered inside and out with aluminum sheet, tilt out windows, and no wood anywhere. I believe it was built in Feb.
Larry

[flyguy]

Re: Another Door Mystery

The 45 I mention above had what I believe was a home-made plywood trim tab on it up until my third flight after I bought it. My friend was flying formation with me and said "You better get back on the ground your tail feathers are vibrating like crazy."

I replaced it with one from the factory and we always figured it was all the mass of the thick trailing edge that made it go into oscillation.

I must have about 20 similar stories about that airplane. What a disaster it was when I got it. Turned out to be a good flier finally after much fixin'.
DC

[VictorBravo]

Re: Another Door Mystery

The 45 I mention above had what I believe was a home-made plywood trim tab on it up until my third flight after I bought it. My friend was flying formation with me and said "You better get back on the ground your tail feathers are vibrating like crazy."

Sounds like a job for some balsa wood, one piece of spruce, and some very thin birch aircraft plywood to me

[Ragwing nut]

Re: Another Door Mystery

There was factory plywood tabs. I have some. They were developed and used on the L-2 and i believe they were adapted and used on the "B" until the metal tab cam out.

[Hank Jarrett]

Re: Another Door Mystery

The wood tabs are factory, BUT, you have to make sure the linkages, hinges and all parts have NO slop and the wood has to be solid and not flex AT ALL! (That means tight, but NOT stiff) The wood ones were multi ply, not your typical "Lowe's" lumber yard stuff. I didn't count the plys in mine, but thought it could be a lamination of three or four layers of aircraft grade. The wood has large lightening holes and works great, but like the tabs on ANY Taylorcraft, if you let it get loose and it is set close to the unloaded position, it will vibrate like mad. That vibration, if it hits the natural frequency of the elevator, horizontal tail, or pretty much any structural part can tear an airplane apart in a worst case. I'm not trying to spread panic. You just need to be VERY AFRAID of flutter, and it is easy to get with loose surfaces, wood or metal. Our planes are pretty slow, so we don't need to worry much about flutter, BUT, you CAN INDUCE it with things like loose controls or (scared me half to death when I heard about it) someone deciding to try a flight with loose or missing jury struts. The struts were vibrating up and down and visible from the cockpit buzzing like a guitar string! The jury strut doesn't just stiffen the strut to keep it from bending, it also significantly reduces the effective length and drives the natural frequency way up.
ANY time you feel buzzing or vibration in the controls or someone sees flutter SLOW DOWN AND LAND! NOW!
Hank

[Doc]

Re: Another Door Mystery

NC43306 was mfg in Feb, '46 as SN 6965 with the frame stamped 6962. The door frames are formed with square tubing, and the windows swing out. The door sills are wood. The door handles are bullet shaped and latch with a flat bar engaging a clip on the rear frame. This model is a Deluxe with the "D" windows and both wing tanks. The cabin ceiling had steel stringers mounted that looked like it was planned to install a skylight. The wing ribs were all hydroformed. Doc

[Larry Lyons]

Re: Another Door Mystery

NC43306 was mfg in Feb, '46 as SN 6965 with the frame stamped 6962. The door frames are formed with square tubing, and the windows swing out. The door sills are wood. The door handles are bullet shaped and latch with a flat bar engaging a clip on the rear frame. This model is a Deluxe with the "D" windows and both wing tanks. The cabin ceiling had steel stringers mounted that looked like it was planned to install a skylight. The wing ribs were all hydroformed. Doc

Joel and Hank: readem and weep!!!! It seems every plane is different
My "41" has the bullet shaped door latches, one wing tank (right wing), no rear windows. As the fuselage is still in the hanger I can not attest to the ceiling stringers or sky light potential.
Larry

[VictorBravo]

Re: Another Door Mystery

You just need to be VERY AFRAID of flutter, and it is easy to get with loose surfaces, wood or metal.

That is exactly the reason I mentioned Balsa instead of all plywood.

Flutter is very very dangerous and can strike at any speed. I yield to Hank's three orders of magnitude higher education than mine, however it is a fair statement to say that a trim tab that's hinged at the front, with no aerodynamic or mass balance, has to be as light and stiff as possible. In addition to having no slop.

A tapered balsa wood core, glued to a spruce leading edge/hinge attach/spar member, with 1/32" birch airplane plywood veneers on the top and the bottom meeting each other and laminated together for about half an inch at the trailing edge, would be the lightest of the all-wood options and perhaps the lightest of all. Composite over foam could possibly lighter with a lot of effort, but likely not worth it.

[Larry Lyons]

Re: Another Door Mystery

That is exactly the reason I mentioned Balsa instead of all plywood.

Composite over foam could possibly lighter with a lot of effort, but likely not worth it.

I would guess that the balsa would be the lightest of all. The composite might be a tad bit stronger, but epoxy is heavy. The only reason they do not use balsa more in aircraft construction is it is not available in big enough pieces and gets extraordinarily expensive as the boards get larger.
Larry

[Hank Jarrett]

Re: Another Door Mystery

Sounds like Bill and Larry's concepts for a trim tab would be superior to the factory design, BUT, they wouldn't be legal! Changing the design materials, shape, CG, weight or hinge moment of a tab would probably bring the FAA down on you to do a full analysis and flight test to allow it (if they found out). The FAA is (justifiably) REALLY skittish about flutter. Some time ago Forrest described some trim tab flutter problems and the Taylorcraft really is pretty safe from this kind of thing (DON'T PANIC guys, we are NOT all going to die from tab and elevator flutter). We just need to be careful and DON'T push it!
I was involved in a trim tab fix on a Cessna 206 and it was WAY out of tolerance. Problem was it was a BRAND NEW PLANE NASA bought from Cessna for research. You think it's tough working with the FAA? Try working with NASA QA on a "Public Owned" category airplane! You should have seen the analysis on THAT repair!
Hank