BobCollins(AA)
Well Known Member
Has anyone ever consider fabricating winglets for the RV-7A ?
Van's Air Force
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Winglet
- Thread starter BobCollins(AA)
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BobCollins(AA)
Well Known Member
Winglets
Would the winglets increase lift and glide distance?
Would the winglets increase lift and glide distance?
If sufficient vortices were present, and the winglets could alleviate them, yes. The wingloading on our planes is simply too low to create the kind of heavy vortex that would sap that much energy though - so the winglet is going to be cosmetic only. Build it if you like the way it looks, but don't expect a performance improvement.
Bill, that's a different Bob Collins you are referring to
Erich
Erich
gbrasch
Well Known Member
Just my 2 cents
Bob, there is another Bob Collins on this site that has been here for years. People are getting you confused with him. It is admirable that you use your real name here as some others don't, but you might consider modifying it a little, for example, "The other Bob Collins", just a suggestion and my 2 cents. Fly safe, Glenn
Bob, there is another Bob Collins on this site that has been here for years. People are getting you confused with him. It is admirable that you use your real name here as some others don't, but you might consider modifying it a little, for example, "The other Bob Collins", just a suggestion and my 2 cents. Fly safe, Glenn
Flying again!
Well Known Member
There are a lot of opinions on winglets but they really are a "fix' for either poorly designed wings (e.g. KC-135), or design constraints such as max wingspan, desire not to change the bulk of the wing design when increasing size of the a/c, etc.
In addition, they are most effective with higher performance a/c and need to be fairly large, not some of the mini winglets you saw showing up on aircraft in the 80's. It appears the RV wings are a decent design and other than cosmetics, there is no need to add winglets to them them.
Remember the optimum wing design has an elliptical spanwise loading which is why the Brits built the Spitfire with an elliptical wing (you can approximate that with wing twist, chord changes, changes in airfoil sections spanwise taper, or many other combinations/techniques). Not sure what the lift distribution looks like on the RVs.
Be aware that if you do put on winglets there will be additional loads (especially in sideslips) that the structure was not designed to cope with. I also suspect that you may end up with worse performance than if you left it alone.
That is my 2 cents based on wind tunnel testing when I worked at the Air Force Wright Aeronautics laboratory (AFWAL) that modified the first a/c (a KC-135) with winglets and also when I was doing wind tunnel testing at NASA when Dr Whitcomb (inventor of the winglet) worked there. You see a lot of winglets on some business a/c that are too small to be effective and are there just for sex appeal (remember the move to t-tails by Piper......)
In addition, they are most effective with higher performance a/c and need to be fairly large, not some of the mini winglets you saw showing up on aircraft in the 80's. It appears the RV wings are a decent design and other than cosmetics, there is no need to add winglets to them them.
Remember the optimum wing design has an elliptical spanwise loading which is why the Brits built the Spitfire with an elliptical wing (you can approximate that with wing twist, chord changes, changes in airfoil sections spanwise taper, or many other combinations/techniques). Not sure what the lift distribution looks like on the RVs.
Be aware that if you do put on winglets there will be additional loads (especially in sideslips) that the structure was not designed to cope with. I also suspect that you may end up with worse performance than if you left it alone.
That is my 2 cents based on wind tunnel testing when I worked at the Air Force Wright Aeronautics laboratory (AFWAL) that modified the first a/c (a KC-135) with winglets and also when I was doing wind tunnel testing at NASA when Dr Whitcomb (inventor of the winglet) worked there. You see a lot of winglets on some business a/c that are too small to be effective and are there just for sex appeal (remember the move to t-tails by Piper......)
Agreed with the above. The wing is to small, loading too light, and speeds to slow for tip drag to be of any concern. It also makes more sense on a swept wing where span wise flow can be of more concern and loss of lift is suffered. FA! is exactly right, winglets are a bandaid for a poor design (or better yet, a modern efficiency upgrade to an old design). Check out the 787 and 747-8 wingtips. You'll see they're washed out towards the tips and tapered off. Brilliant design.
Even if you meet all those metrics (high wing loading, fast, etc)... the economics of it still don't make a lot of sense on a small scale. The fuel burns realized by the introduction on say the 757 were in the 1-2% ball park. When your fuel burn is $4B a year though, a few percentage points is a lot. For an RV... not so much. Plus I doubt the efficiency gains would over come the parasitic drag loss.
If you want to do it purely for looks, I think it would look kind of goofy on the big hershey bar wing of an RV but to each their own!
Even if you meet all those metrics (high wing loading, fast, etc)... the economics of it still don't make a lot of sense on a small scale. The fuel burns realized by the introduction on say the 757 were in the 1-2% ball park. When your fuel burn is $4B a year though, a few percentage points is a lot. For an RV... not so much. Plus I doubt the efficiency gains would over come the parasitic drag loss.
If you want to do it purely for looks, I think it would look kind of goofy on the big hershey bar wing of an RV but to each their own!
rv7boy
Forum Peruser
Another Bob Collins
I thought the same thing the other night when I read one of his earlier posts. I also thought "Why is he asking that question when he's almost ready to fly his RV-7A?"
I thought the same thing the other night when I read one of his earlier posts. I also thought "Why is he asking that question when he's almost ready to fly his RV-7A?"
Well, instead of a true winglet, you could "curl up" the outer edge to get some of the look like what it done on Lancairs.
I believe I have seen pics here some custom wingtips for an RV made to that design.
Never saw anything written about performance but they sure looked good.
Glenn
I believe I have seen pics here some custom wingtips for an RV made to that design.
Never saw anything written about performance but they sure looked good.
Glenn
n5lp
fugio ergo sum
I've seen two interesting RV wing tips at Oshkosh last year. Here they are
I didn't have a chance to talk to the owners.
This one looks like the late Paul Lipps' design.
N941WR
Legacy Member
The original Bob Colllins has changed his login to "Letters from Flyover Country".
Or something close to that
Well, that's confusing! Shouldn't the no-space BC change his name rather than the original BC?
Nothing personal no-space BC.
RV10inOz
Well Known Member
Too slow? Too low wing load?
When Jabiru were doing stall testing for certification in either the
UK,Canada or maybe Oz, they were chasing a knot r two for the model UL.
Winglets, albeit crude, did the trick.
So I dispute the claims.
Ant extra drag may not be worth it on a RV wing..... But how the heck would you know??
When Jabiru were doing stall testing for certification in either the
UK,Canada or maybe Oz, they were chasing a knot r two for the model UL.
Winglets, albeit crude, did the trick.
So I dispute the claims.
Ant extra drag may not be worth it on a RV wing..... But how the heck would you know??
High_Flyer
Well Known Member
I believe that if doing aerobatics, winglets will have some major effect on the handling in negative G and the aerodynamic loads on the winglet can be significant in some manoeuvers and can lead to winglet failure if the design isn't appropriate.
I'm not a specialist on the subject, but that's what I've read a few times here and there.
But it sure would look nice...
I'm not a specialist on the subject, but that's what I've read a few times here and there.
But it sure would look nice...
They were trying to attain certification. How much time, and more importantly money did that 1 know cost them?
RV10inOz
Well Known Member
Probably heaps, but if you needed to do it and repeat it 400 times....it had to be for real. No fudging it.
It worked.
Later the owner of Jabiru who I know quite well told me, the really only made bugger all difference....but they look sexy! And it was a good spot to stick their company logo.
My recollection from my aeronautical engineering classes at university is that the effect of the winglet is approximately the same as adding an equal area to the wing.
For the most part, they make airliners fit through narrower doorways. Beyond that, they're a marketing exercise. They look good on the airliners, but a tiny fin at the back of a hershey-bar wing looks ridiculous.
For the most part, they make airliners fit through narrower doorways. Beyond that, they're a marketing exercise. They look good on the airliners, but a tiny fin at the back of a hershey-bar wing looks ridiculous.
rv9av8tr
Well Known Member
Demmer style droop tips??
So has anyone experimented with a wing tip similar in design to the Demmer droop tips? I had put Demmer tips in my Cherokee 140 and gained 5-7 mph in cruise! They significantly lowered the nose in cruise and lowered the stall speed by about 5 mph. The results were dramatic. My Dad put them on his C-175 and saw similar results.
I have my doubts that winglets would make much difference on the RVs, and by design they induce a vertical rotational force at the tip, so that kind of application would need some real engineering. But I suspect there could be noticeable performance advantage to something like the Demmer tips.
Thoughts out there?
So has anyone experimented with a wing tip similar in design to the Demmer droop tips? I had put Demmer tips in my Cherokee 140 and gained 5-7 mph in cruise! They significantly lowered the nose in cruise and lowered the stall speed by about 5 mph. The results were dramatic. My Dad put them on his C-175 and saw similar results.
I have my doubts that winglets would make much difference on the RVs, and by design they induce a vertical rotational force at the tip, so that kind of application would need some real engineering. But I suspect there could be noticeable performance advantage to something like the Demmer tips.
Thoughts out there?
Plenty of text here about that - just do a search on it. They help a bit for dropping stall speed by a couple knots, and rob those same couple knots off the top end. Pick your poison.
Winglets have many different effects and they will change from aircraft types and operating speeds. On the 737/757 and the 767 they actually increase fuel burn on short flights because of the additional weight. They come into their own on flights over 500 miles and are best on flights over 1000. The winglet on the 737 is the exact same one used on the 757. Installation is a complex procedure requiring almost a complete wing rebuild on the 757/767 from the engine outboard to withstand the twisting forces a winglet imparts to the wing structure. They also lower the VNE from the non wingleted aircraft. They are most effective in fuel burn reduction at the lower end of the cruise speed range and lose effectiveness as you go faster. The aircraft without winglets have a flatter cruise burn curve as they go faster.
I don't really know how the above would translate to a RV but I really can't see them being worth the weight and drag penalty and you would need some engineering to check on the effects on the wing structure.
George
I don't really know how the above would translate to a RV but I really can't see them being worth the weight and drag penalty and you would need some engineering to check on the effects on the wing structure.
George
pierre smith
Well Known Member
Yep
We have them (winglets) available for our Ag aircraft as well. Not only do they block our visibility but Air Tractor sent out a bulletin, advising owners that they would forfeit 40% of their wing life. A 5,000 spar/wing would then only be good for 3,000 hours.
Best,
We have them (winglets) available for our Ag aircraft as well. Not only do they block our visibility but Air Tractor sent out a bulletin, advising owners that they would forfeit 40% of their wing life. A 5,000 spar/wing would then only be good for 3,000 hours.
Best,
