Occasionally I've seen suggestions to taper wings by using identical ribs but with trailing edge angled progressively more and more away from the fuselage centreline as you move towards the wingtip. The ribs stay vertical as viewed from the front, so although chord is less at the tip, thickness stays constant, root to tip.

What do you think about this? I realise that it would not be suitable for those looking for the ultimate in performance, but is it an ok layout for sport use? I may be wrong, but would the higher thickness ratio at the tip (because of the shorter chord) prevent tipstall? If this is the case, it would be effective washout both upright and inverted when used with a symmetrical section.

From : Don Stackhouse

Nick, on larger models this will probably work, but there are some possible pitfalls.

This method not only increases thickness, but on airfoils with nonzero camber it increases camber by the same proportion. This obviously is not an issue for symmetrical airfoils. The problem with increasing camber is that it also lowers the zero-lift angle of attack, so if the geometric washout is not increased enough to compensate, the tip could possibly still stall first.

Assuming the Reynolds numbers are sufficiently high (such as with larger and faster models), increasing thickness will generally improve the stall angle of attack and the max lift coefficient, and also tend to make the stall break more gentle. There are exceptions, so before you invest a lot of time and money in this, I'd recommend looking into the behavior of your particular airfoil sections when thickness is increased.

At low Reynolds numbers, it's very possible that extra thickness could reduce max lift and stall angle. All bets are off here, so don't make any conclusions on small models unless you first do your airfoil analysis homework very thoroughly!

Don Stackhouse
DJ Aerotech