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RV Winglets

calpilot

Well Known Member
My collaboration with Zip Tips from Aveo Engineering resulted in the first set of winglet tips produced, which are on my RV-7. They do four things well:
1. Look snazzy!
2. Reduce drag!!
3. Great lighting!!!
4. Leave incredible bruises when your thigh comes in contact with them on walk around!!!!

Took 20 months to produce, but worth the wait! Send me your e mail address and I will send photos,
Gary Brown
DAR - NW USA
 
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More to the point, did you redo the wing's stress analysis to account for the increased bending moment?

Did you reduce the allowed g rating?

Dave
 
Not at all.

Winglets change the span loading of a wing and therefore change the wing's bending load. In nearly every case this increases the bending load on a wing, which if the wing isn't strengthened to account for that, decreases its strength.

There are only two reasons to install winglets, to improve performance and add storage volume. Since increased volume isn't mentioned, it's certainly reasonable to want any potential performance improvement to be quantified. Typically the top speed might be reduced, due to the increase in parasitic drag, but maximum range and climb rates can be increased. These vary plane to plane, of course.

Dave
 
Zip Tips (RV Winglets)

The first rendition of the winglet created by Aveo Engineering (Zip Tips) resulted in good cosmetics, but poor drag reduction and aft bending moment. The final rendition ( I apologise for not having photos, can't upload directly, and don't use other social media) resulted in a very small upsweep, and a redirect of flow over the aileron with less spill. This reduced overall drag, and reduced the wing tip bending moment. It did add a very slight bit of heavier stick forces, but not enough to complain about. Aveo Engineering does a lot of testing in their wind tunnels, they make winglets for a large variety of small and large aircraft. The LED lighting is the best, and other then a bit pricey, the cosmetic result added to the "snazziness" of the aircraft. I am a DAR in Oregon, I see a lot of "cool" stuff that is well engineered, and a lot of construction I wouldn't taxi in. Please do not beat up on me for merely bringing to the subscribers attention this product that has recently entered the after market. If you want more information, please give Aveo Engineering a call!

Gary Brown
ATP A&P IA CFI DAR
34,000 HOURS
The most fun were in my 4 RV's!
 
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Aveo appears to have updated their homepage with a tiny picture of these tips if anyone wants to see them.
 
More than tiny...click "gallery", then the photos.

Not what I expected for a winglet. More like a shapely wing tip with just a fuzz of extension. They are pretty.
 
Correct me if I'm wrong, but Zip Tips have been out for a while now. I've at least been eyeing them for a year and deleted the stock wing tips from Vans. Unless there's a new version that they're not advertising, these aren't winglets, they're wing tips.
 
Correct me if I'm wrong, but Zip Tips have been out for a while now. I've at least been eyeing them for a year and deleted the stock wing tips from Vans. Unless there's a new version that they're not advertising, these aren't winglets, they're wing tips.

They appear to be different.

Regular:

ZipTips-real-1.jpg


Winglet:

ZipTips-Conforma-02.jpg


I think everyone was expecting something closer to their Mooney offering:

Conforma-Mooney-03-1024x600.jpg
 
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Hopefully Aveo Engineering assessed all that.
I'll second that. Carl knows his stuff on aero-elasticity (flutter). Besides weight (affecting payload), increased wing bending (affecting ability to do aerobatics) and reduced flutter margins, I'll add there is no free lunch to reducing drag.

DRAG reduction is complicated, in that a winglet may increase drag for some flight conditions and altitudes. You are putting more wetted area out there. In theory you are reducing induced drag. However poorly sized or designed it may hurt or do nothing.

Van's wing is a constant chord and thickness NACA 230 series (23012.5). They're just general good all-around airfoils for low speed and cruise. This airfoil has been used on a long list of famous classic very successful airplanes. None have winglets. Don't mess with success.

If you want to reduce drag you would have a tapered wing, in both chord and thickness and make it longer (higher aspect ratio). Look at new airliners. Many have no winglets and longer. Many winglets are very small ones and really a tip fence.... Again complicated and winglets are NOT an automatic goodness thing. On my sheared wing tips I have a razor sharp edge 1/8" wide, from about 2/3 rds chord to TE. This is suppose to help. The standard hoerner wing tip (van's original older style) were also an attempt to reduce drag. They lost favor for the more symmetrical wing tips (it goes in cycles because no one design is perfect).

The one's Carl posted look sexy, but do they work? To be sure "blended" winglets are in fashion. Even when things work to the good, it is hard to measure the small changes.
 
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Buyer beware

Years ago, winglets were made available for our Air Tractor ag airplanes, by an aftermarket supplier, claiming all sorts of benefits including reduced drag, reduced drift, etc.

It wasn't long before Air Tractor issued a statement reducing wing spar life by 50% because of the twisting loads on the spars.

Best,
 
I made some printed winglets for my RV9 and flew them for awhile. Stall speed was reduced by a couple knots. I could not detect any adverse effect on cruise speed. I noticed I developed a bowed shaped on my upper wingtip surfaces. I took the winglets off. The slight bow is still visible.

DSCN0013_zpshfg9fkuq.jpg
 
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Knots 2u wingtips

Just curious has anyone installed the knots 2u wing tips??? If so what do u think?
Any speed gains ? Difference in aircraft handling ?? Any info would be much appreciated.

Thanks
 
One has to ask, why! Why bother the RV's look amaing as per the plans, fly really well handle well have known characteristics and we don't have to fly along thinking I wonder what that fancy bit of wank factor is doing to the structual integrity of my wing?
 
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