Winglet size does it matter

[wag67]

Ok I was just wondering does the size of the winglets really matter. I have a fatboy combat wing and it had really long winglets and I modified them and made them shorter. I flew it for the first time yesterday and it was very sensitive which i believe was CG but was just curious on the winglet size and performance

[zipper]

Corflute winglets will slow down a combat wing significantly, shorter winglets work fin but to short and the wing will side slip when flying slow.
If it became sensitive your winglets must have been heaver than the original.

[sean]

The fin size does matter. My opinion is if you're going to change the fin size, make them bigger.

Say you reduce the fin size by 50%, the reduction in yaw stability will be very noticable (it will be harder to fly and won't track in a straight line) but the reduction in drag will be tiny. Let's say the fins contribute 10% of the aircraft's drag (in reality probably less). If you halve the fin size you might reduce this figure by 30%, meaning a reduction of something like 3% of total aircraft drag.

If you start going really fast (eg dive from speck height) the fins will probably produce a lot more drag than that, thanks to fluttering, bending etc. If that happens it would be worth making them from another stiffer material (eg balsa covered in film... stronger than it sounds). Shorncliffe has a fairly small lift band so it's hard to get a wing really moving there, so at a site like that you might never go fast enough for that to be a concern. Handling is the priority at Shorncliffe I reckon.

A year or two back I built a Bee and made new coreflute fins that were at least double the size of the standard fins. In light to medium lift it was fast and tracked like an arrow, and it even got DSed a bit. It mightn't have been as fast in a dive from speck height as it could have been thanks to the big fins but I reckon handling is more important in a combat wing, and this Bee handled really well.

[nick]

i agree with sean
i put smaller coreflute wing tips on my duck and when you fly slow it yaws and lets you know just before a stall, i will be putting the stock size tips on soon

regards nick

[mrbonk]

Yep, I'll chime in here with my .02 worth as well. My standard BEE now has larger winglets, which have made it track even better than the supplied ones. My BeEvolution also needs larger winglets for the areas I'm flying in. With the supplied ones, it wobbles around noticeably and tracks badly in turns compared to my original one. It's only when it gets going quick that the small fins work properly, but more often than not I'm flying slowly here as my slope spots are tiny.

[drcuzo]

I asked this question on RCG. The consensus from the clever guys was that a wing will fly much better with bigger tiplets. The drag created by corflute end-on is minimal. Their recommendation was think of a size and double it. Nick has done the experiment. In this case big is better.

[wag67]

Well it looks like I will be making some bigger winglets and see how that makes it handle. thanks guys for the advice and quick response.

[zipper]

I beg to differ with respect to speed. I have done a fair bit of testing with winglets (on a new covered wing) and found they reduce the speed noticeably. Using carbon fibre winglets less than 1mm thick would increase the speed to the point were I was overtaking all other wings. Change them to 3mm corflute and I was the same speed.
Drag is a big speed killer on combat wings look at the speed of a brand new covered wing and the speed of one that has some tape bubbles, it may not be much surface area but it kills the speed. Even the difference in speed between a taped wing, a filmed covered wing and a laminating film covered wing is different, the laminating film covering is that little bit smother and will give you about 15mph more top speed, yet the surface doesn’t look that different (more dimples).

[zipper]

Oct 7, 2009 13:33:46 GMT 10 zipper said:

I beg to differ with respect to speed. I have done a fair bit of testing with winglets (on a new covered wing) and found they reduce the speed noticeably. Using carbon fibre winglets less than 1mm thick would increase the speed to the point were I was overtaking all other wings. Change them to 3mm corflute and I was the same speed.
Drag is a big speed killer on combat wings look at the speed of a brand new covered wing and the speed of one that has some tape bubbles, it may not be much surface area but it kills the speed. Even the difference in speed between a taped wing, a filmed covered wing and a laminating film covered wing is different, the laminating film covering is that little bit smother and will give you about 15mph more top speed, yet the surface doesn’t look that different (more dimples on a taped wing).

[sean]

Oct 7, 2009 13:33:46 GMT 10 zipper said:

I beg to differ with respect to speed. I have done a fair bit of testing with winglets (on a new covered wing) and found they reduce the speed noticeably. Using carbon fibre winglets less than 1mm thick would increase the speed to the point were I was overtaking all other wings. Change them to 3mm corflute and I was the same speed.
Drag is a big speed killer on combat wings look at the speed of a brand new covered wing and the speed of one that has some tape bubbles, it may not be much surface area but it kills the speed. Even the difference in speed between a taped wing, a filmed covered wing and a laminating film covered wing is different, the laminating film covering is that little bit smother and will give you about 15mph more top speed, yet the surface doesn’t look that different (more dimples).

I agree about surface finish. Foamies with laminating film seem to fly like mouldies.