Design > Stunt design

Stab Thickness

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Motorman:
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Ken Culbertson:

--- Quote from: Motorman on March 09, 2021, 04:01:35 PM ---Are there guide lines for how thick you can make a stab/elev? I'm building a 550 sq in plane and not happy with the flex I'm seeing with 1/4"stab. I laminated 1/32 top and bottom, inlayed spruce two places and even glassed it with 1.6 and it's still too bendy. I want to make a built up stab that's thick enough to be stiff.

Motorman 8)

--- End quote ---
Assuming a PA not a profile I make mine 1/2" framed and airfoiled with a 1/4" diameter 14" arrorw shaft imbeded in the Stab TE then planked with 1/32.  Stiff and light.  On small profiles like a Twister I cut a slot in the stab, imbed the arrow shaft then plank it again with 1/32.

The same result can be had with a carbon fiber strip on the stab TE. 

Ken

Air Ministry .:
Thickness is more aerodynamics .

If you get a good sheet of 12 Lb/Ft quater grain from the jungle , and bend ? twist it over your knee , youll find its pretty stiff . None of this namby pamby girly stuff for Stab.s , or flaps .



The plantation needs the right kudos, for good wood ,



It makes these guys so strong, they can carry a whole tree . You need it from a hidden shaded one , so it took a long time to grow so the grains really close , with 18 month min. seasoning .

Air Ministry .:

Serge_Krauss:
Here's a stiff horizontal tail section for my 503 square inch plane. The stab consists of a 3/16" trussed balsa core and 1/16" balsa sheeting for a thickness of about 5/16". Carbon veil is used between these laminations, which are epoxied together under the weights shown. The elevator is solid medium-weight (probably 7-8 lb) balsa. The entire surface is covered with .56-oz glass and just enough epoxy to attach and fill the glass. The cross section is shown in one of the photos below. The blue tape was used to keep epoxy out of the cloth hinges during construction - extremely important. The assembly flexes very little under hand loads and would be even stiffer, if I had applied the glass with a 45-degree bias. Much of the stiffness comes from the diagonals themselves. This horizontal tail assembly weighs a bit less than a like one I built earlier with carbon veil on the elevator and silkspan on the stab, but no veil under the 1/16" sheeting.

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