What software are you guy's using?

[esc]

Or with the half-round and 3mm x 0.5 strips fitted to the leading and trailing edges:

[Wojcigitty]

The Addiction has carbon in the TE of the wing, I believe, and tape hinges. The tape hinges come off after a while and it's kind of annoying.

How thick are the ailerons? How fast is the airplane going to go? Before you invest your time in using carbon to increase the torsional rigidity, ask yourself if it's worth it. It will probably be fine without it.

Good call on realizing that the triangulation does not increase torsional rigidity, also. Most people don't realize that.

[esc]

Hi Wojcigitty,

Carbon fibre strips are relatively inexpensive and I am not talking about using much in this design. I suspect that no matter how fast the plane is moving designs like the Addiction and E-Shock experience far more twisting of the control surfaces than the human eye can resolve. I should think that captured on a slow motion camera we would all be surprised by how much flex there is.

The ailerons and tail surfaces are only 1/8" thick on my design and so creating a structure that does not flex is very problematical.

Before you congratulate me I must say that I cannot agree with you about triangulation not reducing torsion - I am afraid that I believe it does, but it won't eliminate it altogether and requires applying correctly and with the correct cross-sectional shapes, i.e. at least a 2:1 aspect ratio running in the correct dirctions.

The conclusions that rcpilot82 and I reached were based on using 1/8" sq. balsa strips to form the triangles - this is next to useless on an aileron so large and so thin and just adds weight. We cannot eliminate the flex totally but hopefully we might reduce it without too much effort. In truth to get the most rigidity we should have another set of cross members working in the opposite corners to the ones shown so we would have 4 triangles in each section - but that is getting a bit complicated. Perhaps you are right that the complication is uncessary. Do you still think that it is not worth the experimentation?

Please see the attached pictures of Sir Barnes Wallace's Wellington bomber. He was a master of the art.

[esc]

Don't you just love the engineering delight of these fuselages. Pitty I haven't found any really good pictures of the wing structure.

Dave

[Spooky]

	Quote: Originally Posted by esc
	Hi Spooky, I am sorry I did not intend you guys to appear to be shut out - that's not the case at all. Regards, Dave

No problem esc, I was just interested to see your design get built , and to see rcpilot82's building techniques , I'm always looking for tips and tricks from others builds.
I tend to agree with Wojcigitty on over-thinking the design, if your worried about flex, you could make both of your aileron designs and make them removable by pinning the hinges, then try both, a little extra work, but then scratch builds are pretty much experiments anyway.
Another thought, you could also use an X pattern of CF across the aileron, just a thought, it would be a little more involved though... like you need more to think about .

looking forward to more,
Dean

[rcpilot82]

I have the plans from esc. I am now in the process of making cnc files and gathering wood. As for the ailerons, we will see how they go together and go from there, I don't like tape hinges on this size model. If I were to do something like that I would make hinges from covering for a better bond. I hope to have all the wood ( gotta order some 1/4") and cnc files done this week so I can get this thing on the building board.

[Spooky]

Cool, keep us posted and good luck on the build rcpilot82, looking forward to it.

Dean

[Wojcigitty]

There's a lot of good discussion in this thread, I like it.

Triangulation and torsional rigidity:

Build a rectangular box out of sticks and twist it. You see lots of movement; the sides of the box act as parallelograms, and the ends of the box shear relative to each other. You can see it in this rubber thingy:



See how the squares form diamonds when twisted?

Now add a cross brace at the corners of the squares. Your parallelograms have now become triangles, and your box is much more torsionally rigid. This is because as you try to twist the box, the cross braces prevent the ends of the box from shearing relative to each other, and the parallelograms are "locked" in place by the cross brace. This is how the torsional rigidity of those Wellingtion fuselages was attained.

However, your aileron is on a single plane. When you twist it, there are no two members that shear relative to each each other like in a box. Triangulation really only works for torsional rigidity when the part is three dimensional.

I've been kind of brief in this explanation and I probably didn't make much sense. I'll try to rephrase it tomorrow when I have some CAD software to draw what I mean.

[Mithrandir]

the problem is the thickness of the ailerons is very low (And thus the enclosed cross sectional area is small)....... hard to get torsional rigidity with any material when the enclosed area is small...

For a torsionally stiff structure, one wants to maximise the enclosed volume and minimize the perimeter.... (Of the cross section.... sorta like the prop shaft for an automobile... a purely torsional structure).... and have elements (Like stringers or longrons) in a truss type pattern.... you still need some cordwise elements as well....

for example....a composite aileron should should be an approximately triangular cross section with the fiber orientation at a plus'n'minus 45 degree angle (WRT the leading edge) and the cloth should wrap all the way around to close the structure... (Like NOT an open taco shell)

[esc]

I don't think I will make any more comments on this subject for now.

I think rcpilot82 is quite right in his decision to try the model as is - a good pragmatic approach - "if it ain't broke don't fix it." I can change the design later if necessary.

I have in mind a new model one that I have been thinking about for a while and have begun to gather the information I need. I can share the idea with you here or start a new thread?

BTW has anyone used "CompuFoil 3D," if so what do you think of it?

Dave

[rcpilot82]

I have used compufoil, and like it. I have not tried copmpufoil 3d. is it still shareware?

[Spooky]

	Quote: Originally Posted by esc
	I think rcpilot82 is quite right in his decision to try the model as is - a good pragmatic approach - "if it ain't broke don't fix it." I can change the design later if necessary. I have in mind a new model one that I have been thinking about for a while and have begun to gather the information I need. I can share the idea with you here or start a new thread? Dave

Good call on building it the way it was designed rcpilot82, like esc said, "if it ain't broke don't fix it", and like most everything else built in this world, they make prototypes and change/redesign what needs to be, same goes for this, you could drive yourself crazy trying to think of every little detail that would work the best, but we all know the real world does not always jive with the CAD world, I'm sure every designer has been there, me for one.

esc, let us know if you make a new thread for the next design, I'll definitely be checking it out.

rcpilot82, if you don't mind sharing some info on compufoil, I too would be interested, I've never used it before and it sounds interesting.

Thanks guys and good luck,
Dean