Wing Tip Shapes

Wed Nov 24 11:02:35 AKST 2004

Here is my $.02 worth.........not that I am an accomplished flyer, nor am I
a bad flyer.
I have designed and built several airplanes capable of pattern schedules.
They have used ailerons tip to tip and rounded wing tips. Approximately 8
years ago, I started using ailerons that were several inches short of the
tip and continued 3"-4" shy of the fuselage. This kept them out of any
disturbed air stream. The difference is noticeable. I also use a vertical
piece at the end of the aileron at the wing tip side that is as tall as the
maximum deflection of the aileron, this acts sort of like a fence. It is
only the width of the aileron and not the wing. Seems to be effective as
low deflection is required. This could be a combination of things. The wing
tips are rounded on the top and bottom only, for ease of construction and
covering. 
About the hinge line, instead of using a triangular shape on the leading
edge surface, I round them off. I find that as the surface moves, the gap
is maintained as a tight seal. No sealing of gap required. This applies to
rudder and elevators.
The above is what works for me.

ORLANDO FRETS
Project Manager
United Space Alliance
ojfrets at earthlink.net

> [Original Message]
> From: Scott Smith <js.smith at verizon.net>
> To: <discussion at nsrca.org>
> Date: 11/24/2004 7:41:53 AM
> Subject: RE: Wing Tip Shapes
>
> Good info Troy and timely as I was about to run the same experiment.  Now
I
> think I'll just cap the ailerons and elevators and be done.  How does your
> theory hold up on the rudder?  (I imagine since it's not a lifting
surface,
> it's not as critical)
>
> I'm building Patriots which has a balance tab forward of the hinge line. I
> found on my previous planes that the rudder is extremely sensitive around
> neutral.  Even with lots of expo, small corrections were very visible
(which
> was probably a good thing as a fledgling pattern pilot!)  Anyway, I was
> going to reduce the rudder area by cutting the hinge line "through the
tip."
> Capping the rudder is also a possibility, but that's a pretty big piece
> hanging out there susceptible to hanger rash.  Any thoughts?
>
> Also, could we get some opinions on trailing edge thickness?
>
> Thanks,
>
> Scott
>
> -----Original Message-----
> From: discussion-request at nsrca.org
> [mailto:discussion-request at nsrca.org]On Behalf Of Troy A. Newman
> Sent: Wednesday, November 24, 2004 4:01 AM
> To: discussion at nsrca.org
> Subject: Re: Wing Tip Shapes
>
>
> No, not drag
>
> the reason that the tips are usually blunt is its easier to make them the
> same.
>
> My personal opinion is that it does matter. Can you fly 2 different models
> and tell the difference...maybe not. I think that there are reasons to
round
> out the tip and that's why I round them. I also think as a side note
reason
> its a sign of craftsmanship in how your model looks. I take pride in my
> models and my building. Part of that is making it look right in my eyes. I
> want to be proud of the way it looks on the ground and the way it flies in
> the air. That is why I do things the way I do them.
>
> Just like I believe there is a really good reason to not run the ailerons
> and elevators thru the tips....But everybody is doing it and showing it on
> their kits...I don't do mine that way. Mine will be capped in. I feel it
> helps in the arena of servo pot wear. Putting the aileron out in a known
> area of turbulence is not going to help your servo pots. Plus I think the
> models with ailerons thru the tips don't fly as well in crosswinds. Maybe
> its because this turbulence causes lots of little tip stalls all the time
in
> as the air hits the hinge line. If the aileron is covered by a wing tip
then
> this is prevented.
>
> I proved it to myself a couple years ago building identical models one
with
> tips and one thru the tip on the ailerons and consistently the one with
tips
> flew better in turbulent air. I also had a model this summer that had
> ailerons thru the tips and it was hell on servo pots, and I never felt the
> model would lock in like I think it should.
>
> Another reason for having wing tips and stab tips is to have a reference
for
> the control surfaces neutral position. I think this is very important in
> maintaining the model.
>
> Same can be said for top hinge vs. standard bevel and middle hinge
setups. I
> don't like the idea of the center of rotation of the surface not being in
> the middle of the surface. Lots of manufacturers are doing this now and
> recommend it in their kits. I don't like it.
>
> Does it really matter nope.....I think you can live with any of it. I
> personally think the choices you make in your models construction like
wing
> tips and so on are much less critical than making the left and right sides
> match. However I do think that certain choices will produce a better model
> from a aerodynamic point of view.
>
>
> Just my thoughts
>
> Troy Newman
>
> ----- Original Message -----
> From: "Dieter Rozek" <rozekd at earthlink.net>
> To: <discussion at nsrca.org>
> Sent: Tuesday, November 23, 2004 11:36 PM
> Subject: Wing Tip Shapes
>
>
> > After looking at many different Pattern and IMAC models and even full
> > scale for that matter, I noticed that the wing planform
> > for most aerobatic aircraft ends in a blunt tip.  I may be wrong about
> > this but the information which I've read regarding aerodynamics
> > would suggest that this kind of wing tip generates drag as opposed to a
> > highly tapered or fusiform shape such at a spitfire.
> > My question is does this type of tip help at slower speed and therefore
> > that's why it's being used or why the blunt ends on
> > all the aerobatic planes?
> >
> > Dieter
> >
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