Reinforced tips: Speed increase?

[McFly]

For those of you who have added wing tip reinforcement to your flying RV: Did you get any additional speed? Looking for real numbers.

I am flying a RV-7 with bat the wingtips. Thanks.

[jjconstant]

Just wondering why you would expect additional speed out of an internal change to the tips????

Jeremy

[gereed75]

[quote=McFly;522223]For those of you who have added wing tip reinforcement to your flying RV: Did you get any additional speed? Looking for real numbers.

No, but it did stop dimpling in the top part of the tip near the leading edge. Mine dimpled in so far that it cracked my paint. Stiffened with a foam insert.

[rvmills]

Ya know McFly, it's an interesting question as you peel the onion...(perhaps...or perhaps I'm just thinking too much).

My initial reaction was "huh...that's on the inside" as well. And having talked to lots of racers that have said chasing speed with tip changes has been mostly unfulfilling, I didn't think innards would make a difference.

Then seeing Gary's post about dimpling hit a note. The past year (with lots of racing), my tip lenses have cracked quite a bit (changing them now). Was it the number of hours at race speeds putting loads on them via tip dimpling, or did taping the edges of the lenses put stress on them, or is it just them being 13 years old...hmmmm.

That leads me to wondering if dimpling or deforming would cause more drag/less speed (slight though it may be), or would the deformation be the tips' attempt to fair a bit more and become less of a drag producer.

If anything, its likely the former, but with aerodynamics, you just never know...and its best to look at all sides.

So, for the aero engineers...would stiffening the tips with inserts to maintain shape be a drag reducer, or would losing the natural flex (if any) be a drag producer?

I've never noted any visible flex or deformation, but Randy's foam stiffeners caught my eye in this thread.

Cool Q McFly! See ya at the WCFC!

Cheers,
Bob

[McFly]

Once again I am out in left field, which would be fine if only I knew I was in left field

Bring me back to center guys. I thought the only reason for the reinforcement was to prevent inflight deformation, which might increase drag.

So what I gather from gereed75's post is that it is done to prevent cracks from the flexing? Any other reasons?

My flexing is in the back third of the tip where it is relatively flat when unloaded, concave when loaded. This is not intuitive to me since I would think it would be a low pressure area.

Looking forward to seeing you at WCFC Bob! Blue Skies

McFly