|Chris Walby||04/10/2019 17:43:42|
994 forum posts
Looking at a set of plans and it got me thinking..
For warbirds and generally other models is there any specific reason for the ailerons not to extend to wing tip e.g. the aileron forms part of the wing tip?
How does a wing tip aileron type wing perform close to stall or is there no difference?
All views welcomed
|Tim Flyer||04/10/2019 18:15:04|
1073 forum posts
Maybe its due to disruption of airflow . Wind speed at the tip is often faster than the rest of the wing when manoeuvring so disrupting it creates more drag there and a smooth tip manoeuvres better at high speed.
Edited By Tim Flyer on 04/10/2019 18:15:34
|Chris Walby||04/10/2019 18:34:19|
994 forum posts
Thanks Tim, I was wondering more what happens as it approaches stall.
The ones I was looking at are only the last 1/3 of the wing although quite wide and as a warbird I would not expect to have much deflection. I was looking through other warbird models and can't see any with this configuration (standing ready to be corrected!).
Cheers for the reply.
|Frank Skilbeck||04/10/2019 18:42:58|
4488 forum posts
It was quite common in WW1 planes but as aerodynamics became more understood then ailerons weren't extended to the wings tips. I suspect part of the reason is that designers take great care to avoid/reduce the vortex that comes off the wing tip, caused by higher pressure from underneath the wing "leaking" round the wing tip. This causes drag so anything that reduces this will increase the speed of the aircraft.
If you look at slow flying aerobatic models then it's quite common to extend the ailerons to the wing tip, but drag isn't an issue for these models as they aren't chasing speed.
|J D 8||04/10/2019 18:49:08|
1307 forum posts
The Polikarpov I16 has long narrow ailerons that extend almost to the tip, a feature I recon did not help with the touchy lateral handling of the model I had. In the end I extended the tips some keeping them solid. Red bit of aileron is fixed.
Edited By J D 8 on 04/10/2019 18:50:55
Edited By J D 8 on 04/10/2019 18:52:42
583 forum posts
You could consider the aerodynamics of full size aircraft, but from a model design point of view, if you run the aileron all the way out there is a greater chance of it's leading edge catching in the grass and getting damaged or even torn off. The wing tip protects that from happening with an aileron that stops short.
|Nigel R||04/10/2019 21:03:28|
3099 forum posts
Close to the stall I would imagine the airflow is already very turbulent especially at wing tip trailing edge. Hence aileron or not probably makes little difference.
Avoiding damage seems most likely. Construction considerations also important. Maybe it is easier or quicker to make an accurate tip in one piece on a full size airframe.
I can't say I've ever noticed any difference in model behaviour between strip ailerons right to the tip and those that stop a couple of inches shy.
Flutter might have something to do with it. Perhaps it is less likely if the aileron stops shy of the tip.
Edited By Nigel R on 04/10/2019 21:05:36
964 forum posts
Regardless of what the plan says I never take the aileron to the tip. From an early bad experience with flutter which was. Cured by stopping short and gluing an inch or two of trailing edge in place
|Chris Walby||04/10/2019 21:58:15|
994 forum posts
Should I stick as is or make the tip a complete block (LE to TE)?
|Don Fry||04/10/2019 22:54:09|
4043 forum posts
A complete block. It's easier. And if the tip scrapes the ground, the ailerons don't get ripped off.
Scale considerations also apply. Your shout.
|Simon Chaddock||04/10/2019 23:00:05|
5465 forum posts
I would be more worried about the position of the hinges than the aerodynamic effects.
Any control surface that 'over hangs' a hinge is much more likely to contribute to odd characteristics including flutter.
In many WWII types the wing tip was not part of the main wing structure and in some cases (the Spitfire) a completely separate structural component so it was easier and more rigid for the aileron to only go as far out as the "aileron spar".
Is that a Bf 108 wing?
On the full size the aileron did not go out to the tip!
|Martin Harris||04/10/2019 23:06:46|
8870 forum posts
Looks more like an FW190...
|Chris Walby||05/10/2019 07:52:04|
994 forum posts
Come on chaps no guessing and lets stick to the OP
Thanks for all the advice its been very helpful and on that basis plus there seems to be very few models with this configuration I will opt for solid wing tips. Its not so much avoiding damage as if I touch the wing tip on the ground I think the result will be very messy if not terminal.
A solid wingtip might just help a little bit with air flow over the tip and I though the aileron length was short compared to the adjacent flap. I'll move the aileron up to rib 26 which should compensate for the loss of aileron area. I don't think Kurt Tank would be too upset (have I let slip) as the mark went through a few variations in its development.
I'll do a build log in due course, but for the time being I have more questions than answers at the planning stage.
Thanks for everyone's input.
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