Smaller Wing Tips for Speed

Bob Axsom · #1 10-16-2009, 09:18 AM

I have experimentally modified many things on our RV-6A and participated in over two years in SARL sanctioned cross country air races. My experience and observation of others is the easiest way to increase the speed of an RV is to replace the wing tips with homebuilt shorter ones on the order of 3" span each.

Bob Axsom

frankh · #2 10-16-2009, 09:29 AM

So the bat wing tips don't make a difference in speed as far as you know Bob??

Frank

RVnoob · #3 10-16-2009, 09:51 AM

can you post some pix ? Please?

you obtain additional speed, at the expense of lift. Is that the correct assumption?

rv72004 · #4 10-16-2009, 10:36 AM

Quote:

Originally Posted by Bob Axsom

I have experimentally modified many things on our RV-6A and participated in over two years in SARL sanctioned cross country air races. My experience and observation of others is the easiest way to increase the speed of an RV is to replace the wing tips with homebuilt shorter ones on the order of 3" span each.

Bob Axsom

What kind of speed increases expected ? What kind of stall increases?
I was thinking of modifying my ones , ie cutting them down some.

rvmills · #5 10-16-2009, 10:59 AM

Bob,

Seems that many racers at Reno have clipped wings...some radically so (take a look at Rare Bare's wings...very short span!):

My wings are clipped 3.5 inches, much the way I'm told many Rocket wings are. I'm considering making a pair of racing wingtips, but am not sure what might be the best shape. Wondering what your thoughts are on best (fastest) shape...symmetrical, more curved on top/flat on bottom, flat plate, etc.

I took a few pics at the Pagosa 100, and will post them here:

Here are my current tips (slightly curved on top, slightly increasing span towards the trailing edge:

Wayne Hadath's F1 tips look somewhat similar to mine:

John Huft's appear to be a little more symmetrical (top to bottom shape) with the tip edge more towards chord center, versus a bit lower on mine and Wayne's (I think):

Mike Thompson has some flat racing tips, seen here:

And Tom Martin's very fast F1 EVO has flat tips (and I think that may be standard on the EVO wing...not positive though, but it's a very different wing altogether):

So what does your research and experience say with respect to tip shape? With an already shorter wing, I don't want to overdo this, but I'm very interested in your thoughts on size and shape. Thanks much!

Cheers,
Bob

Bob Axsom · #6 10-16-2009, 11:05 AM

The plane is faster in top speed by 3 kts and the plane is different in other ways - slower climb, higher stall speed, faster roll rate, etc. - that you would expect from a smaller wing. The word I get is Van's found no measurable speed increase by going to the bat wing tip. Mike Thompson cut off a set of tips and added plexiglass wing tips (eyeball data) and claims a similar speed increase. The shape of mine in plan view are an exact copy of the lower surface of the wing airfoil with a maximum span of 3".

Bob Axsom

Bob Axsom · #7 10-16-2009, 12:25 PM

Here is a photo of mine on the ramp at Taylor. Question for Bob Mills - Has Mike removed the plexiglass tip plates from his wing tips? Mike and I both race in the RV Blue class and we are most competitive.

Bob Axsom

Bruce · #8 10-16-2009, 05:34 PM

Bob,

First thing how is the wife doing.
Mike did take the plexi off. Don't know if his speed changed
or not.
Can't take my tips off so I guess I will be behind you when I get
racing, Anteneas in the wingtips.
Where is John Huft getting all the speed in that 8. Looked at his web
site and he put on the speed.
Incedence in the Horizontal Stab ????????????

Hope it works and hope to be with you guys next year.

Missed ya at Grace flight.

Bob Axsom · #9 10-17-2009, 09:09 AM

Jeanine after 3 surgeries and 5 hospital stays I think has turned the corner to improvement. She starts radiation therapy Monday and Chemotherapy sometime a little later due to waiting for the broken leg to heal.

John Huft has done a magnificent job with his RV-8 modifications with a lot of focus on the firewall forward. He is a teriffic guy and engineer but I still have him in my sights. It is a carrot on the stick situation but I'm dumb enough to keep pursuing it and happy with the challenge.

Bob Axsom

rvmills · #10 10-18-2009, 09:51 AM

Bob,

Glad to hear that Jeanine is showing steady improvement. I'm certain that your all-out, being-there-for-her support has been a key factor. She's in my thoughts and prayers as she continues treatment.

On Mike's airplane, I saw no plexi on the tips in Pagosa, just the small, flat tips.

I looked at John Huft's website, and he's sure done a lot of tweaking...it certainly has paid off! I'm trying to develop a plan for incremental mods, starting withe basic clean-up of external draggy items and gaps seals. Trying to determine the best tape to use on hinge seals to be effective, yet be removable with no paint damage (and which gaps to seal...top and bottom of H-stab? Rudder? gear leg and tail fairings? left-to-right seams? longitudinal seams? etc.). I also want to look at my aileron and flap rigging to see if I can clean that up a bit. Also looking at FWF areas, as I can probably clean up my cooling air inlets and maybe reduce my exit area, as I run pretty cool. Tom Martin mentioned smoothing out exit air flow with a ramp back by the firewall, to keep the air exiting the cylinders from slamming into the flat firewall, but that will take some thought, since the firewall is clobbered with hoses, gascolator, and various penetrations. Lots of things to ponder and play with this winter.

As others have said, I read all of your posts on drag clean-up with much interest, and thanks for keeping the racing scene alive for all of us!!

Cheers,
Bob