HP Aircraft wing tip

[emsvitil]

Are the flaps and ailerons reflexed a little (with tip matching) to get the fastest speed?

[Little Al]

Curious has anyone tried these on a Rocket that already has shorter wings. At what point having to little wing aspect ratio starts to hurt performance? Also wondering the gain compared to a good sharp sheared wingtip. It just says 3mph gain over a flat cut off tip.

[Laird]

Originally Posted by emsvitil

Are the flaps and ailerons reflexed a little (with tip matching) to get the fastest speed?

If I've got my facts straight (not guaranteed) the NACA 23012 airfoil that the RV-3/4/6/7/8 uses has less of a pitching moment than the Roncz airfoil of the RV-9/10/14 so reflexing the flaps (or ailerons) doesn't have the same effect.

You'll notice that the Roncz airfoil airplanes have a larger horizontal stab to balance the higher pitching moment. Reflexing the flaps reduces the pitching moment of the wing and unloads (reduces the (-) lift of) the stab in cruise which causes the increase in speed.

That's my story and I'm sticking to it....

Laird

[Mike S]

Originally Posted by Little Al

Curious has anyone tried these on a Rocket that already has shorter wings. At what point having to little wing aspect ratio starts to hurt performance?

Bob Mills did at the Reno Air Races this year.

He, Steve or Bob K. should be the ones to comment as to the speed change.

[Bob Kuykendall]

Originally Posted by Laird

...the Roncz airfoil of the RV-9/10/14...

The RV-9 does indeed have a Roncz airfoil. But the RV-10 and RV-14 have an airfoil that Steve Smith (scsmith) designed especially for Vans.

Originally Posted by Little Al

Curious has anyone tried these on a Rocket that already has shorter wings. At what point having to little wing aspect ratio starts to hurt performance? Also wondering the gain compared to a good sharp sheared wingtip. It just says 3mph gain over a flat cut off tip.

Bob Mills writes a bit about that in this earlier VAF thread.

[PhatRV]

Originally Posted by scsmith

We periodically post updates on the tapered composite wing project in a separate thread, but we are probably overdue. We have closed the wings, and chased all but one fuel tank leak. Should have that one fixed next weekend. Bob Mills has match-drilled the aluminum stub spars to fit his Rocket-6.

Next up will be a static load test, end of January. In the mean time, I am starting to work on the ailerons and flaps.

I can't wait for the next update.

[scsmith]

Ah-hem.....yes John Roncz did design the RV-9 airfoil. But as Bob K mentioned the RV10/14 airfoil is mine. Reducing pitching moment is a benefit, as you describe, except that all these airfoils have very low section pitching moment. The large tail was added to the -9 because of the large slotted flaps which do add quite a lot of pitching moment.

Reflex (negative flap) primarily helps by keeping the nose of the airfoil at the best angle to promote laminar flow. Both the -9 airfoil and the -10/14 airfoil do maintain a modest amount of laminar flow. The NACA 23013.5 on the earlier designs does not. If you have a -9 or -10/14, keep the bugs cleaned off the wing and don’t paint trim stripes on the leading edge.

Originally Posted by Laird

If I've got my facts straight (not guaranteed) the NACA 23012 airfoil that the RV-3/4/6/7/8 uses has less of a pitching moment than the Roncz airfoil of the RV-9/10/14 so reflexing the flaps (or ailerons) doesn't have the same effect.

You'll notice that the Roncz airfoil airplanes have a larger horizontal stab to balance the higher pitching moment. Reflexing the flaps reduces the pitching moment of the wing and unloads (reduces the (-) lift of) the stab in cruise which causes the increase in speed.

That's my story and I'm sticking to it....

Laird

[Laird]

Originally Posted by scsmith

Ah-hem.....yes John Roncz did design the RV-9 airfoil. But as Bob K mentioned the RV10/14 airfoil is mine. Reducing pitching moment is a benefit, as you describe, except that all these airfoils have very low section pitching moment. The large tail was added to the -9 because of the large slotted flaps which do add quite a lot of pitching moment.

Reflex (negative flap) primarily helps by keeping the nose of the airfoil at the best angle to promote laminar flow. Both the -9 airfoil and the -10/14 airfoil do maintain a modest amount of laminar flow. The NACA 23013.5 on the earlier designs does not. If you have a -9 or -10/14, keep the bugs cleaned off the wing and don’t paint trim stripes on the leading edge.

Thanks for clearing up my mis-information Steve. I stand corrected and more informed!

Laird
PS. Wingtips look Awesome. Hope you sell a ton.

[bjdecker]

For grins/giggles -- https://www.nasa.gov/sites/default/f..._wing_k-12.pdf

Kinda looks like Steve...or his dad (or Richard Whitcomb)

Seriously impressive work sir.

I was hoping to get these tips installed before years end - but the Tax Man and Santa Claus conspired against my bank account. Next year....Next year....