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ss aileron questions

JimW

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Okay you Pitts guys, I have just a couple of questions for now.

1)- What is the up/dn deflection for Pitts S-1SS ailerons?

2)- Is there any type of mass balancing used in the SS Pitts ailerons? If there is, how is it done?

Okay, that was three questions. We are planning on SS ailerons for our Skybolt. Stuart has graciously been fielding questions for me by PM. I thought it was time to ask a wider audience. Maybe someone else will think of something I haven't thought to ask Stuart. There is at least one Skybolt flying (possibly a second) with SS ailerons so we aren't exactly breaking new ground here. David Stone from Steen Aero put me in touch with the builder of the one many of us have seen at Oshkosh or Sun n' Fun. I had a long conversation with him and learned a great deal.

So far we have learned the following:

1) The Pitts S-1 and the Skybolt use the same airfoil.
2) The thickness of the ss ailerons should be about 16-18% thicker than the adjacent full ribs. This was later verified checking the Pitts drawings.
3) The hinge point for the ss ailerons should be around 29% aft of the tip of the aileron. This was also verified checking the Pitts drawings.
4) The up/dn aileron deflection is 23 degrees for Skybolt Friese ailerons. This really looks correct for our SS mockup but we want to see what the Pitts is for comparison.

So far we have drawn our Skybolt ss ailerons full scale and they really look just like a blown up version of the Pitts. We will call that a success.

The aileron hinge mount at the rear spar for a Pitts uses two bolts. The Skybolt Friese hinges at the rear spar use four. We will use four.

The Friese hinge parts at the spar of a Skybolt aileron is similar but slightly heavier than a Pitts. We will use the Skybolt version (.071 plate with bushings on the bolts) by just changing the hinge point. Simple enough.

We will be able to keep the bellcranks, slave struts, pushrods, and attaching hardware that is used on the Skybolt Friese ailerons. We will also keep the locations. The only change is we will be adding one more hinge inboard since we are adding one bay (11") of aileron width. We don't want to mess around centering things and get the slave struts any closer to the I-struts. Aligning with the I-struts can have issues if it doesn't go right.

The construction of our SS ailerons will be very similar to the Skybolt Friese ailerons. We will have a 1/4" ply nose rib, a 3/4" spar almost exactly the same size as the Friese, The same spruce nose piece, same gussets, etc. The only change is we may make the leading edge in carbon composite instead of plywood. This is really because it will be easier to make the composite part full length instead of splicing plywood. I'll have to vacuum-bag it either way.

Okay, so what haven't we thought of?

cheers,
Jim

Stuart,
Thanks for your help to date. It is always appreciated.






 

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