Wing Tips (no, not the shoes!)

captainron · #1 12-22-2006, 05:45 AM

This must have come up at one time or another, but has anyone ever tried wing and elevator tips a la Mooney style on a Vans?
Or, going another route, has anyone tried winglets?

RV8N · #2 12-22-2006, 06:29 AM

I've seen winglets on a Glasair IIFT that used to be local. It looked pretty silly. My concern would be what kind of loads are the winglet imparting to the wingtip and will the pop-rivets or #6 screws be strong enough. I kind of think it would be ok but who knows.

captainron · #3 12-22-2006, 07:37 AM

I have to think that a simple flat aluminum tip would weigh much less and have less drag than the fiberglass tips.

pierre smith · #4 12-22-2006, 08:13 AM

Hi Ron,
The Air Tractor factory deducts 40 % spar life when owners install winglets, or just multiply your 8000 hour wing (on my AT502) by .60 for 4800 hour spar life due to the twisting loads imposed by the winglets. They're supposed to reduce vortices and allow for less chemical drift. Leland Snow (owner of Air Tractor) has been fussing with the FAA for years now regarding spar life. BTW, my airplane is now at Southeastern Aircraft, just west of Ft. Pierce, getting new (used ) wings since mine have 7820 TTSNEW on them. FWIW, the PT6 on the front also has 7820 TT with no overhaul yet!!

I'm sure that at 200 MPH speeds, there'd be even more twisting loads even tho' our little stubbies are stiffer than my Air Tractor's 50 foot wings. As you well know, wingtip design is still somewhat of a black art and I'd doubt you'd see any difference with or without (square ala Mooney) wingtips. I recall a guy out west with no tips....well, square ones and a reported faster cruise. Less span maybe?

Regards,

aadamson · #5 12-22-2006, 09:37 AM

Here, let me help you solve this question, once and for all.

Here's a Lancair Legacy with tiplets.

Now, let me get this out of your head. Those tips, unless you can fly in the FL's are a *speed penalty*. Test have been made on Lancair 4's, and they cost you about 3kts down low and really only gain you maybe 2kts when *way up high - like above 20K*.

The Commercial guys use em to reduce the drag from the wing tip vorticies, but we'll never be able to go fast enough to make that happen for us, unless you want to test VNE.

They look cool, but are useless and a penalty.

captainron · #6 12-22-2006, 09:59 AM

Quote:

Originally Posted by pierre smith

(square ala Mooney) wingtips. I recall a guy out west with no tips....well, square ones and a reported faster cruise. Less span maybe?

Regards,

This is more what I was pondering than the winglets. Each bare wingtip weighs 6 pounds before any additional glass, filler or paint. I don't think I'm nuts-this idea worked for Mooney! I was just questioning if it's been tried on a Vans! If someone has tried it and indeed shown a faster cruise, I believe it's in the realm of plausible ideas. What are we building experimentals for anyway?

N674P · #7 12-22-2006, 10:47 AM

Quote:

Originally Posted by captainron

This is more what I was pondering than the winglets. Each bare wingtip weighs 6 pounds before any additional glass, filler or paint. I don't think I'm nuts-this idea worked for Mooney! I was just questioning if it's been tried on a Vans! If someone has tried it and indeed shown a faster cruise, I believe it's in the realm of plausible ideas. What are we building experimentals for anyway?

Good point, Ron - Outside of maybe looking funny, a flat aluminum plate on the end of the wing would save a lot of weight. I can't imagine the glass tips add anything to structural integrity.
I'm looking forward to hearing how this turns out! When I get to that point, the flat plate option would sure save a lot of time and weight!

captainron · #8 12-22-2006, 11:03 AM

Quote:

Originally Posted by N674P

Good point, Ron - Outside of maybe looking funny, a flat aluminum plate on the end of the wing would save a lot of weight. I can't imagine the glass tips add anything to structural integrity.
I'm looking forward to hearing how this turns out! When I get to that point, the flat plate option would sure save a lot of time and weight!

Thanks Johnny, This seemed like a normal inquiry, and after seeing endless discussions on induction, plasma, 90K Garmin panels, car engines running at 5000 rpm, I get blasted for questioning a simple, proven, easy concept that does work on some fast "spam cans". It might look funny, but when you're in the driver's seat and going fast, can you see it?

RV8RIVETER · #9 12-22-2006, 11:08 AM

Search winglets on you will find posts by a few aero engineers on the subject. Basically, a performance penalty on most a/c ours included.

I have been thinking about something like the tips on the Nemesis. Have not seen them in person, so it may be "unfeasable pipedreaming" as well, but the theory of impersonating an elliptical planform seems sound. Seems like mother nature got it right a long time ago (shark fins, tuna, ect.)

captainron · #10 12-22-2006, 11:28 AM

My reasoning for the Mooney comparison is only that it is an airplane of comparable speed and power to what we are building, but they have always had a speed edge over similar competition in the "spam" world. Think about the older models: Lycoming 180 hp, no fancy engine stuff, simple as a rock! I have heard stories that the wingtips were done this way for speed, and also heard that they were done this way simply for economics of build. If the truth is that this design is faster, as well as being way simpler and faster to build and finish, who wouldn't be interested?