Effect of thicker wing tips.

[David Hall 9]

I'm planning on scratch building some Depron/foam sheet models.

I'll use the easy wing building method of folding a sheet to form the LE, then back over a spar to the TE.

The easy way to do this is to use a constant thickness of spar. If I chose a tapered wing plan (say 75% of the root chord at the tips), then the tips will be relatively thicker.

Will this lessen the possibility of tip stalling?

[Nigel R]

Leading edge shape is the most important factor, I think. Making the tip blunter than the root is the key to what you want.

You can always add some triangular stall strips to the root if you find a problem with tip stall.

[Jon H]

if you go too mad with the thickness to chord ratio nasty things happen. If you can draw up the two profiles and slap them on here.

As Nigel says there are plenty of ways to deal with tip stall with washout being the norm. Stall strips are used extensively on full size

[ron evans]

About 40 years ago I made a Hawk for PSS. Quite a taper on the wings, I made the tips E374, but the root with the same section was much too thick.

A mate who was clever with computers printed out the section at 80% of the original and that looked a lot better.

In pecentage terms the tip was thicker than the root, and I'm not sure if this was the reason, but the low speed handling was very good.

I was able to hold in full up all mover. and the model would just sink with enough aileron authority to keep the wings level.

the model is still in the attic...must refurb one day.

Ron

[Jesus Cardin]

Thicker wing tips hs has the same effect than wash-out: it makes the wing tips to stall after the centre wing section.

Anyway if you are going to go with a tapered wing, you should do some drawings so a to keep with a difference of 2-5% between central wing section and tip one. Above those figures you may even find problems to turn as there is the risk of an adverse yaw effect due to wing tips large drag.

[Sonofpincher]

I generally do small, light, electric "own designs" and often come up against "tip-stalling". "Wash-out" is the usual cure, but I'm confused by some experts who suggest that a high lift section at the tip - the opposite of washout - is needed. I also see that the US site Flite Test offer a Spitfire with a folded wing section, but having the outer section of the underside sheet cut before the tip, which seems to result in a heavily undercambered tip, their reason given " to stop tip-stalls" So would a undercambered tip be more efficient than washout - which doesn't offer much lift during normal level flight?

[Denis Watkins]

14 minutes ago, Sonofpincher said:

I generally do small, light, electric "own designs" and often come up against "tip-stalling". "Wash-out" is the usual cure, but I'm confused by some experts who suggest that a high lift section at the tip - the opposite of washout - is needed. I also see that the US site Flite Test offer a Spitfire with a folded wing section, but having the outer section of the underside sheet cut before the tip, which seems to result in a heavily undercambered tip, their reason given " to stop tip-stalls" So would a undercambered tip be more efficient than washout - which doesn't offer much lift during normal level flight?

My observations on homebuilder indoor flyers of 16"  - 2 0" has proved a positive improvement in slow fly ability with thicker wing tips

 2 types worked well

4" of drinking straw UHU glued to the outer lower wing leading edges and the best slow fly has

 4" of straw that was 1 st split along its length with steel rule and scalpel

And lengths of these droops on the leading edges at the tips

[Maurice Dyer]

Wouldn't these added to the tips make the tip stall problem worse ??

 

Ive got a Black horse 60 inch Chipmonk that tip stalls like a maniac at the first chance it gets; ive reflexed the tips up  (washout) by about a mill or so.

Not had chance to try it out yet. Like your idea of straws at the root though......

Maurice

[Denis Watkins]

Keeping some power on with wing add ons, is important Maurice, so yes, extra thickness is more drag

But with power on, lift is maintained and improved at low speed, but try not to glide as the brakes come on !

A 5 foot wing span Chippy can be challenging at low speed like others in its class

But 1mm reflex always helped me, together with spot on lateral balance and C of G on its spot.

Keep the Chippy moving and have a plan, don't ad-lib during he flight before you get to know it.

When I see lads maybe struggling a bit with a too slow arrival

I advise that they don't struggle the landing in a forced touch down at the end of the approach,

But to arrive at good speed, and control level flight above the ground further out and settle down to the runway from a few feet up at flying speed

cutting and motor as the wheels are in contact with the runway

[Sonofpincher]

Must try to follow that landing technique, Denis, as an infrequent flyer, I'm "rusty"every time! Any thoughts about my initial post on building in a high lift tip to the wing to combat tip stalling? I'd love to know if that Flite Test idea of the undercambered wingtip works. I'll have to build one to find out.