Discussion in 'Skybolt Miscellaneous' started by gmatejcek, Sep 4, 2018.
Do the Firebolt plans show symmetrical ailerons?
My copy does.
Just goes to show how little I know about Skybolt/Firebolt airplanes........
Could you just take some packing tape and build some gap seals as has been discussed on this forum before and stick them in the cove for a test to see if the forces are lighter? On my first Pitts S1 I added rudimentary gap seals on the ailerons in this manner and it greatly improved feel and roll rate. Albeit those were frieze ailerons but still, I would assume would make a difference here too?
Might also look on the plans and see if they call out a specific gap between the LE of the aileron and the cove and make sure your ailerons are in spec. I know that on some aileron installations this gap is extremely critical to get optimum performance and feel.
We've tried a seal on one aileron with neutral to negative results. Debating the next step. As I believe was previously mentioned, the metallic upper and lower trailing edge extensions / gap seals are not present and can't be added (to my knowledge) without recovering the wings. The gap is supposed to be 1/16th, and ours is much larger, although I've not quantified it.
External coves are used on some of the Model 12 Pitts airplanes, specifically the ones produced by Kevin Kimball. I have seen external gap seals on Frise ailerons. The problem will be that once you go down this path the screw holes will always be there even if the seals are not retained. I do not believe the feel of the aileron will change much with the addition of seals because the nose of the aileron is (I think) a simple radius with the hinge point at the center. There may be some increased stick forces if you increase the roll rate because you're creating more of a pressure delta on the aileron to realize that gain. In any case I'm very interested in what you learn.
I’m not sure that taping just one aileron is going to net the results you are looking for if noticeable at all. I don’t think it could hurt to tape all 4 and go for a test flight.
If possible however, I’d get the gap set correctly between the LE of the aileron and the cove on all 4 ailerons and give that a shot before attaching aluminum gap seals with screws.
Either way I’m interested to see what you find out as well!
what im seeing on these ailerons is being confused with SS ailerons. these look like plain old symmetrical ailerons. which will have heavy stick force with their forward hinge line. but it appears they are trying to use some of the SS tech, like them being thicker than the wing. prolly just needs a set of spades as the leading edge cove doesn't need to be as critical as it does with SS ailerons. if it was changed, I wonder if it would even matter on these. with the hinge line so far forward, youre just pushing the aileron around and not getting much aerodynamic help as you would with SS ailerons. also, the gaps around the hinges are huge. you would see a pretty good increase in roll rate if some fairings with slots just big enough for the hinge were made to cover these up.
These ailerons are virtually the same as the original Aviat style symmetrical ailerons. That particular design's heaviness could only be remedied by the addition of spades. I would put any work into spades rather than wasting time on gap seals or cove adjustments.
I'm thinking anything you can do to keep the high and low pressure sides of the aileron separate is a good thing for roll authority. It's true for a Frise aileron that gets taped and it's true for the SS ailerons that have had the clearances around the hinges minimized. I'd expect the old style symmetrical design to respond in a similar way. I do agree that aerodynamic balances must be added to lower the stick forces and that these are separate subjects to be addressed.
From what I remember, Herb tried some foam seals and also used the tape seals available on the Eagle back then with little to no effect. When it was all over, the factory used the spades and did nothing about sealing the gap on the ailerons. The fact that this is also probably a 24 foot wing 'Bolt won't help much no matter what is done. Spades will reduce the control pressures and that sometimes seems to feel like the airplane is rolling slightly faster due to less effort.
I seem to remember the gaps not being too bad on the S-2B, maybe they already got most of the sealing from the way they did the build. I don't think that's the case with the Firebolt but as I have already demonstrated my knowledge is very limited.
My S2E with symmetrical ailerons has pretty big gaps. Yet, with spades, it rolls around that 240 degrees/second. I would tend to agree with Mr. Morphew.
Good to know S2e.
We had symmetrical ailerons on Polecat which we later sealed but I don't remember any great improvement in roll rate. That airplane didn't have aileron coves so it could be an apples/oranges thing.
Indeed. And if the results were spectacularly bad, with only one gap taped up they should only be 1/4 as bad. Hence the incremental testing. The first increment was not good, so plan B will be sorted out and applied as time permits.
And, again, redoing the TE of the cove requires recovering of the wings. That is not going to happen any time soon.
Aerocruz- when was your airplane built?
Here are some photos of Model 12 coves done externally for your consideration;
In general I've thought seals would be positive and find negative result odd? But I'm not a wiss.... The barn door ailerons(apples and oranges for sure) on the Spezio MUST be sealed. I'm told it's close to unflyable w/o them. I haven't tried it w/o.
Yeah, there are soooo many possible contributors to our situation it just isn't funny.
The model 12 pix do give me an idea, though. It will have to percolate and bounce off a couple others before I would move ahead. Safety and all that. The execution of this wing pretty well precludes using the exact technique used on the 12, though.
All the anecdotal evidence leads to simple spades and calling it good, but there is one strident voice against that I need to respect.
The seeming decrement to handling might be due to details of the test set up, and a better , more labor intensive method awaits.
Given the relatively minor change to perceived handling, I also want to address a minor rigging issue prior to much more experimentation.
Suddenly I sense about a foot of yarn dangling from my sweater...
Thanks, everybody, for your time, thoughts, and consideration. I'm about to head out on a trip so I won't be able to hands-on tinker for a couple weeks. Please feel free to keep the juices flowing though, I'll just be an electron away!
BTW, WRT Aerocruz's build date, I have to wonder if the design might have started with the symmetrical ailerons, they were found to be suboptimal, and then Frise types were adopted to address the issue. Things that make you go hmmm...
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