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  #11  
Old 12-21-2021, 02:53 AM
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emsvitil emsvitil is offline
 
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Are the flaps and ailerons reflexed a little (with tip matching) to get the fastest speed?
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  #12  
Old 12-21-2021, 09:09 AM
Little Al Little Al is offline
 
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Location: Osage, Iowa
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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.
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  #13  
Old 12-21-2021, 10:14 AM
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Laird Laird is offline
 
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Default Reflexing flaps

Quote:
Originally Posted by emsvitil View Post
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
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  #14  
Old 12-21-2021, 10:39 AM
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Mike S Mike S is offline
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Quote:
Originally Posted by Little Al View Post
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.
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  #15  
Old 12-21-2021, 10:47 AM
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Bob Kuykendall Bob Kuykendall is offline
 
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Quote:
Originally Posted by Laird View Post
...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.

Quote:
Originally Posted by Little Al View Post
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.
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Last edited by Bob Kuykendall : 12-21-2021 at 11:02 AM.
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  #16  
Old 12-21-2021, 11:22 AM
PhatRV PhatRV is offline
 
Join Date: Mar 2018
Location: Buena Park, California
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Quote:
Originally Posted by scsmith View Post
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.
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  #17  
Old 12-21-2021, 11:25 AM
scsmith scsmith is offline
 
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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.


Quote:
Originally Posted by Laird View Post
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
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  #18  
Old 12-21-2021, 03:16 PM
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Laird Laird is offline
 
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Quote:
Originally Posted by scsmith View Post
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 donít 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.
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  #19  
Old 12-21-2021, 04:27 PM
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bjdecker bjdecker is offline
 
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Default My .02

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....
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