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  #31  
Old 06-17-2011, 03:55 PM
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REHughes REHughes is offline
 
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Default X-47B Tip Shape

I ran across some drawings that I believe reflect the latest tip planform for the X-47B Carrier Suitability test vehicle.

The shape could be easily adapted to the RV wing, and might enjoy some advantages by limiting any imposed twisting loads on the wing.

http://www.richardcyoung.com/terrori...r-system-ucas/
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  #32  
Old 06-17-2011, 04:24 PM
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Originally Posted by REHughes View Post
I ran across some drawings that I believe reflect the latest tip planform for the X-47B Carrier Suitability test vehicle. The shape could be easily adapted to the RV wing, and might enjoy some advantages by limiting any imposed twisting loads on the wing. http://www.richardcyoung.com/terrori...r-system-ucas/
I think you just wanted to post this for the fun of it. There is no info on wing tips... I sat through the video and read the article. The wing is highly swept and it's a tailless design, so not sure the applicability to a low speed RV, verses transonic swept flying wing UAV. I suspect the wing tip shape and the two sharp angles is for stealth.

BTW auto-land on carriers is not new... The carrier pilots don't go around saying they have autopilot that can get them on deck, so a UAV is not going to be a big deal. It is pretty clear pilots in fighters will be a thing of the past in the near future... well the future is here.
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  #33  
Old 08-20-2011, 02:35 PM
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RV8RIVETER RV8RIVETER is offline
 
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Default Easy tip mod

Continuing the subject of wingtip mod, I just wanted to report an easy way to mod the std Hoerner tips to be sharp, for anyone who may be interested.

I found some 3/32 pieces of balsa wood at the local hobby shop. I cut an about 1/2" deep groove (went deeper in about 4 spots for more hold) in the tip with a cut-off wheel. Then soaked the wood in epoxy, filled the groove with flox and set the blasa strip in to set, and backfilled the edges with micro. It has turned out to hold a nice sharp edge and the balsa fibers resist chipping. The balsa is also light and more importantly holds the nice straight line of the wingtip.

I am sure Prof Hoerner would be happy now, as the stock edge was very rounded indeed.
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  #34  
Old 08-20-2011, 03:37 PM
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Quote:
Originally Posted by RV8RIVETER View Post
Continuing the subject of wingtip mod, I just wanted to report an easy way to mod the std Hoerner tips to be sharp, for anyone who may be interested.

I found some 3/32 pieces of balsa wood at the local hobby shop. I cut an about 1/2" deep groove (went deeper in about 4 spots for more hold) in the tip with a cut-off wheel.
I assume the balas was 3/32 thick. You used a cutoff while and just by hand to put a grove in the wing tip? Is it even 1/2" thick any place? I was thinking going in 1/32" not 1/2"?

Quote:
Then soaked the wood in epoxy, filled the groove with flox and set the blasa strip in to set, and backfilled the edges with micro. It has turned out to hold a nice sharp edge and the balsa fibers resist chipping. The balsa is also light and more importantly holds the nice straight line of the wingtip.
Any pictures you care to post?

Quote:
I am sure Prof Hoerner would be happy now, as the stock edge was very rounded indeed.
I am sure he would be. Have you done any A/B flight test comparison before after?

That is a great idea. How is a sharp edge critical on the Hoerner tips? I thought it was uber critical for the symmetrical / sheared tips. Sorry if the question is old news.

I had the Hoerner tips on my old RV4 but the RV7 has the symmetric and I do plan on sharping up the edge. I was going to use a thin strip of brass like the insert in old fashion school rulers and using it like you did with balsa I image. I like your idea better, lighter and easier to bond to. I was thinking metal to hold a very sharp edge.... but it would be a pain to work with and get to fit. Balsa is a nice former.
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  #35  
Old 08-21-2011, 09:39 AM
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Quote:
Originally Posted by gmcjetpilot View Post
I assume the balas was 3/32 thick. You used a cutoff while and just by hand to put a grove in the wing tip? Is it even 1/2" thick any place? I was thinking going in 1/32" not 1/2"?


Any pictures you care to post?


I am sure he would be. Have you done any A/B flight test comparison before after?

That is a great idea. How is a sharp edge critical on the Hoerner tips? I thought it was uber critical for the symmetrical / sheared tips. Sorry if the question is old news.

I had the Hoerner tips on my old RV4 but the RV7 has the symmetric and I do plan on sharping up the edge. I was going to use a thin strip of brass like the insert in old fashion school rulers and using it like you did with balsa I image. I like your idea better, lighter and easier to bond to. I was thinking metal to hold a very sharp edge.... but it would be a pain to work with and get to fit. Balsa is a nice former.
Hey George

Yes the sheets, about 6" wide I think, are 3/32 thick.

I started the groove with a body saw as it was easiest to make a straight cut along the edge. Then made a pass along the line with the cut-off wheel.

As for thick, can only speak about the old style Hoerners I have. They are over 1/2 thick at least 80% of the length. I had to go over 3/4 in a few places to get all the way thru. I went that deep because most of it is gel coat and I didn't feel comfortable bonding only to the gel coat. I probably could have gone more shallow since the 4 cuts thrus are bonded to the inside fiberglass, but deeper made me feel better.

No data as I am still building. I think as long as I am still working a part I might as well make sure it is the best it can be. The original edge was pretty rounded, at least a 1/4" radius. Searching for Heorner data found that the sharp edge is one of the critical design components, along with the flat top surface, straight thin trailing edge, and convex lower surface, IMIC.

ADDED: Sure, I can post a picture, but will have to wait until Wednesday, as I will not be able to get to the hanger until then.
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Last edited by RV8RIVETER : 08-21-2011 at 10:21 AM.
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  #36  
Old 08-21-2011, 02:41 PM
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Quote:
Originally Posted by RV8RIVETER View Post
. They are over 1/2 thick at least 80% of the length. I had to go over 3/4 in a few places to get all the way thru. I went that deep because most of it is gel coat

ADDED: Sure, I can post a picture, but will have to wait until Wednesday, as I will not be able to get to the hanger until then.
Gelcoat.... ha ha! I forgot about the Vans Gelcoat... it can be thick.

Yes thanks, I'd appreciate it. I am interested, a picture would be nice!

I think that's the right way to go, get'er done right, be done with it.

Later you could swap tips out with stock ones for flight test comparison (which you probably won't). It's just the engineer in me that likes data. I'm pretty sure it's a very good worth while mod, even if you can't measure the difference by it self. You'd need smooth air and subsequent flights in identical conditions. Trying to resolve stall speed or top speed to a MPH for a small single Mod is almost impossible. I'm sure it will be an improvement. Top speed might increase, stall decrease? It might be more than a MPH or two? Who knows; I don't. I'm guessing. Hard to predict the effect. There is no math for it.

However when you get her all flying and the overall performance is above par, as I suspect it will be, it will be due to attention to detail like this. Cheers
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Last edited by gmcjetpilot : 08-21-2011 at 02:49 PM.
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  #37  
Old 08-21-2011, 03:37 PM
Bob Axsom Bob Axsom is offline
 
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Default Just comments

This is the fastest of 5 configurations I have made for my plane so far:



I look at the tips people put on their airplanes looking for some kind of performance gain I assume, then they stick on the nav lights and strobes naked in the breeze - That can't be a good thing.

Bob Axsom

Last edited by Bob Axsom : 08-21-2011 at 03:39 PM.
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  #38  
Old 08-21-2011, 07:19 PM
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Quote:
Originally Posted by Bob Axsom View Post
This is the fastest of 5 configurations I have made for my plane so far:

I look at the tips people put on their airplanes looking for some kind of performance gain I assume, then they stick on the nav lights and strobes naked in the breeze - That can't be a good thing. Bob Axsom
I think part of the gain is you clipped the wing a tad, reduced wing area... good fore a little higher speed but (if noticable) higher stall?

Can I ask how much faster and what else did you try, may be you have a thread... sorry if it's old news. I know people have used end plates with some degree of sucess.

I gather van has done all kind of test. I suppose the stock ones are pretty good, but the edge mod (sharp) seems to be the hot ticket. I see yours are rounded.

I agree nav lights in breeze on wing tip (or any where) can't be good.
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  #39  
Old 08-24-2011, 10:06 AM
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Here you go George. Took some pictures as I did the trailing edge of the last tip today. Still work in progress.

Yes, I do intend to experiment, by the way. I have my wingtips attached with hinges so that I plan to try other tips later on when valid speed data can be gathered. Wanted to make it easy to change for racing tips when it is time to race.





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  #40  
Old 08-24-2011, 10:14 AM
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Quote:
Originally Posted by RV8RIVETER View Post
Here you go George. Took some pictures as I did the trailing edge of the last tip today. Still work in progress.
Awesome pics Wade... Thanks a million... That looks sharp (pun intended). You will have to put a sign up at air show, to keep a passersby clear, so they don't cut their self .... Ha ha! That baby will cut through the air~!

That is great news you have them removable and might do some testing... love the data!

Unrelated curious question, what is the small tab at the trailing edge with a screw?
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Last edited by gmcjetpilot : 08-24-2011 at 10:18 AM.
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