jenatepilot
Member
I love what Harmon did for the RV4 giving it a shorter and stiffer wing and coincidentally a higher G tolerance. Is there ANYONE who has done the same favor for the RV8???
Van's Air Force
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Clipped wing RV-8
- Thread starter jenatepilot
- Start date
jenatepilot
Member
Even someone that has removed the fiberglass tips. Any improvement in top end speed?
WillyEyeBall
Well Known Member
wing tips
Don't know if you're asking about cosmetics or performance, but 3 of us RV-4s that I know have gone to flat wind tips with fences to improve roll rate and retain stall speed for IAC competition without changing the rib spacing:
Same thing could apply to RV-8s.
Bill McLean
RV-4 Slider
Alabama
Don't know if you're asking about cosmetics or performance, but 3 of us RV-4s that I know have gone to flat wind tips with fences to improve roll rate and retain stall speed for IAC competition without changing the rib spacing:
Same thing could apply to RV-8s.
Bill McLean
RV-4 Slider
Alabama
Roo747
Member
bonehead composites
Not sure what you'll get with these but looks interesting.
http://www.boneheadcomposites.com/m8/717--RV Wing Tips.html
made of carbon fibre
Cheers
Not sure what you'll get with these but looks interesting.
http://www.boneheadcomposites.com/m8/717--RV Wing Tips.html
made of carbon fibre
Cheers
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rocketbob
Well Known Member
I have a friend who did this on a Super 8, not yet flying. Cut the last outboard bay off and built shortened ailerons.
I have seriously considered this as well
In my case I have a fall back, with the tip tanks I can put back 1.5'. However at 180 HP with 21.5' span I get the feeling that going down two rib bays would be a mistake. If I get beat too bad at Texoma on march 31, 2012 I'll have to look at it again.
Bob Axsom
In my case I have a fall back, with the tip tanks I can put back 1.5'. However at 180 HP with 21.5' span I get the feeling that going down two rib bays would be a mistake. If I get beat too bad at Texoma on march 31, 2012 I'll have to look at it again.
Bob Axsom
jenatepilot
Member
great
great info guys. If my measurements are right, then leaving the wing tips off and making a flush end will take a full 2 feet off the span leaving it at 22'. The harmon II is only 2" less than that so it sounds like a quick fix for faster roll rate and less drag.
ANYone have templates for the flush tip and fences?
great info guys. If my measurements are right, then leaving the wing tips off and making a flush end will take a full 2 feet off the span leaving it at 22'. The harmon II is only 2" less than that so it sounds like a quick fix for faster roll rate and less drag.
ANYone have templates for the flush tip and fences?
DRBuilder
Well Known Member
JM Out of Indy?
longranger
Well Known Member
But... The HRII still has a full compliment of ribs (closer spacing), thus a stiffer wing.
N941WR
Legacy Member
On the HR, the same number of ribs are retained but the wing is shorter.
To do this with the -8 you will want to order a custom spar and wing skins, parts without the pre-punched holes.
Then your options are less flaps or less aileron. Either way it will land faster and roll quicker than a stock -8 due to the shorter wing. Pick the compromise you want.
To do this with the -8 you will want to order a custom spar and wing skins, parts without the pre-punched holes.
Then your options are less flaps or less aileron. Either way it will land faster and roll quicker than a stock -8 due to the shorter wing. Pick the compromise you want.
Several years ago I spoke to a gentleman who was designing different wing for RV8. Great engineering brainpower was behind it. Since then I've never heard of any progress.
F1Boss
Well Known Member
Look at the whole equation
The Rocket can get away with a shorter wing (which REQUIRES a higher IAS, all else being equal) because the ship has a larger engine. If you do not add a serious upgrade in HP to a clipped 8, the ship is gonna be significantly slower at higher altitudes, as in above 5000MSL, which is not very high.
Remember, every design is a compromise. To get something, you are likely to give up something, unless a wing redesign is also in your plans.
Carry on!
Mark
The Rocket can get away with a shorter wing (which REQUIRES a higher IAS, all else being equal) because the ship has a larger engine. If you do not add a serious upgrade in HP to a clipped 8, the ship is gonna be significantly slower at higher altitudes, as in above 5000MSL, which is not very high.
Remember, every design is a compromise. To get something, you are likely to give up something, unless a wing redesign is also in your plans.
Carry on!
Mark
smokyray
Well Known Member
The long and short of it...
Well said Mark! Furthermore and in conclusion, the RV7 and 8 have longer and significantly different constructed wings than the RV4. As you mentioned the HR2 is built from the RV4 wing kit with all the original RV4 ribs moved closer together. Big difference? The 6 and 4 have a laminated spar vs a billeted single chunk of aluminum for the 7/8. (laminated is stronger in my humble opinion) There has never been an HR2, RV4 or 6 in-flight wing failure that I know of. There has however been an RV8 in-flight wing failure, a Van's demonstrator RV8 several years ago. Shortening the billeted spar in the 8 would require stress testing since the billeting changes thickness from fuse to tip.
V/R
Smokey
PS:My RVX wingspan is identical to the RV6 but with RV4 ailerons. (51" vs 48") Essentially the span and aileron length of a HR2 on a 6 fuselage. I trimmed the RV4 flaps to match the remaining room left on the wing! The span from fuse to tip on the X is within 1/4" of my Harmon Rocket wing span and identical to any stock RV6. Result, best aerobatic RV I have flown yet!
Well said Mark! Furthermore and in conclusion, the RV7 and 8 have longer and significantly different constructed wings than the RV4. As you mentioned the HR2 is built from the RV4 wing kit with all the original RV4 ribs moved closer together. Big difference? The 6 and 4 have a laminated spar vs a billeted single chunk of aluminum for the 7/8. (laminated is stronger in my humble opinion) There has never been an HR2, RV4 or 6 in-flight wing failure that I know of. There has however been an RV8 in-flight wing failure, a Van's demonstrator RV8 several years ago. Shortening the billeted spar in the 8 would require stress testing since the billeting changes thickness from fuse to tip.
V/R
Smokey
PS:My RVX wingspan is identical to the RV6 but with RV4 ailerons. (51" vs 48") Essentially the span and aileron length of a HR2 on a 6 fuselage. I trimmed the RV4 flaps to match the remaining room left on the wing! The span from fuse to tip on the X is within 1/4" of my Harmon Rocket wing span and identical to any stock RV6. Result, best aerobatic RV I have flown yet!
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rocketbob
Well Known Member
Yep that's correct!
Thanks F1 Boss
That adds weight to the conclusion I came to with our airplane in flight recently. Although my 21.5' wing span configuration is faster than my 24.5' cruise configuration (tip tanks remember) at 6,000 ft dalt I noticed a slight nose high hanging on the prop condition. I decided then that going shorter would risk performance everything else remaining equal. The flat metal tip configuration is 21' and if I went shorter I could use those with tip plates ... I seldom go above 3,000' in the short races and the tip tanks would get most of it back for me in cruise. Heck, If I put the old stock tips back on the wing span would go all the way back up to 22.5' which is just 0.5' below RV-6 stock span. Depends on how things go at Texoma and beyond. I don't want to do it so it will take some big motivation like finishing last to push me in that direction.
Bob Axsom
That adds weight to the conclusion I came to with our airplane in flight recently. Although my 21.5' wing span configuration is faster than my 24.5' cruise configuration (tip tanks remember) at 6,000 ft dalt I noticed a slight nose high hanging on the prop condition. I decided then that going shorter would risk performance everything else remaining equal. The flat metal tip configuration is 21' and if I went shorter I could use those with tip plates ... I seldom go above 3,000' in the short races and the tip tanks would get most of it back for me in cruise. Heck, If I put the old stock tips back on the wing span would go all the way back up to 22.5' which is just 0.5' below RV-6 stock span. Depends on how things go at Texoma and beyond. I don't want to do it so it will take some big motivation like finishing last to push me in that direction.
Bob Axsom
DRBuilder
Well Known Member
John built the engine mount for my Super-7. Did an AWESOME job. Just over 44 hours on it now and loving it! John definitely knows RV's.
rvmills
Well Known Member
Nate,
I have a Super Six with clipped wings (7" per side, same number of ribs in the shorter span...much like the HRII wings). What others have said rings very true (as you'd expect from this smart bunch!)
Concur with Smokey's recommendation to consult with Van's engineering folks before diving in. Proven concept on the 4/6 wing, not sure if its been done on an 8 wing.
My set up is slightly different than Smokey's, in that I have full size flaps and lost the span in the ailerons (guess that means Smokey would be trying to lure me into a rolling scissors, and I'd be pulling into the vertical or trying to drag him up into a flat scissors...eh Rob!
)
As far as performance goes, as was mentioned, the g limits remain the same with my higher gross weight. That was a key element of the design feature, from what I've been told. If you're not going heavy (big motor), not sure you need to go that route. If just seeking higher g limits, I'd also find out from the engineers if other parts of the plane will tolerate higher g (tail, etc). If you're just seeking more safety margin at max g...perhaps that's a valid reason...but I think there is a good safety margin there if well built and maintained.
I've found that the clipped wing g-limit-saving design feature does cost in high altitude performance. At Airventure Cup 2010, Mark, Wayne Hadath and I climbed to 15.5K, then Wayne went up to 17.5K. At 15.5K, Mark (with his EVO Wings) slowly walked away from me (at that time we were very evenly matched at SL). Wayne (with the same wing as me) lost even more top end at 17.5K and fell back, then descended. I tend to cruise at 12.5 to 13.5 for best effeciency...and that sweet spot altitude would likely be higher with stock wings. So I pay a little in specific fuel consumption there.
Flat tips will likely buy you some speed (mine added 3 kts, and upped the stall 5 knots); should add roll rate (as Bill said) but cost in highter bleed rates in a turn or vertical maneuver. I use the flat tips for SL racing with fewer turns. I'm intrigued by Bill's fences...if they preserve stall speed, that's a bonus (Bill, how are they at bleed rates under g, and did they add any top end?)
The good news on flat tips, is you can go back to stock, which I did for the turning races at Reno (still bleeds some there though).
Here's a few pics. First is Mark and I at Reno, me with stock tips:
Here's a pic of us at Macho Grande (Marks place near Taylor, TX):
Pretty stubby with clipped wings and flat tips, eh! Its a bit skewed because I'm a little closer to the camera in the first pic, and a little further away in the second, but it gives some perspective.
Just for fun, check out this tip design, by a guy here in Reno:
They are called Scimitar tips, and Eric's website is here. Eric said they are optimized for turning...very little bleed under g. Would they work at RV speeds?...not sure. Eric thinks there may be some benefit. Bet I get Bob Axsom's juices flowing with that one though!
Finally, of the Super 8's I know of, I don't believe any have been clipped. Kahuna has those long-range tanks in his, and I imagine standard-length wings keeps his maneuvering wing performance closer to that of the other Team RV aircraft as well. Kahuna, any structural mods to the wings, other than the tanks?
Interesting topic Nate!
Cheers,
Bob
I have a Super Six with clipped wings (7" per side, same number of ribs in the shorter span...much like the HRII wings). What others have said rings very true (as you'd expect from this smart bunch!)
Concur with Smokey's recommendation to consult with Van's engineering folks before diving in. Proven concept on the 4/6 wing, not sure if its been done on an 8 wing.
My set up is slightly different than Smokey's, in that I have full size flaps and lost the span in the ailerons (guess that means Smokey would be trying to lure me into a rolling scissors, and I'd be pulling into the vertical or trying to drag him up into a flat scissors...eh Rob!
)As far as performance goes, as was mentioned, the g limits remain the same with my higher gross weight. That was a key element of the design feature, from what I've been told. If you're not going heavy (big motor), not sure you need to go that route. If just seeking higher g limits, I'd also find out from the engineers if other parts of the plane will tolerate higher g (tail, etc). If you're just seeking more safety margin at max g...perhaps that's a valid reason...but I think there is a good safety margin there if well built and maintained.
I've found that the clipped wing g-limit-saving design feature does cost in high altitude performance. At Airventure Cup 2010, Mark, Wayne Hadath and I climbed to 15.5K, then Wayne went up to 17.5K. At 15.5K, Mark (with his EVO Wings) slowly walked away from me (at that time we were very evenly matched at SL). Wayne (with the same wing as me) lost even more top end at 17.5K and fell back, then descended. I tend to cruise at 12.5 to 13.5 for best effeciency...and that sweet spot altitude would likely be higher with stock wings. So I pay a little in specific fuel consumption there.
Flat tips will likely buy you some speed (mine added 3 kts, and upped the stall 5 knots); should add roll rate (as Bill said) but cost in highter bleed rates in a turn or vertical maneuver. I use the flat tips for SL racing with fewer turns. I'm intrigued by Bill's fences...if they preserve stall speed, that's a bonus (Bill, how are they at bleed rates under g, and did they add any top end?)
The good news on flat tips, is you can go back to stock, which I did for the turning races at Reno (still bleeds some there though).
Here's a few pics. First is Mark and I at Reno, me with stock tips:
Here's a pic of us at Macho Grande (Marks place near Taylor, TX):
Pretty stubby with clipped wings and flat tips, eh! Its a bit skewed because I'm a little closer to the camera in the first pic, and a little further away in the second, but it gives some perspective.
Just for fun, check out this tip design, by a guy here in Reno:
They are called Scimitar tips, and Eric's website is here. Eric said they are optimized for turning...very little bleed under g. Would they work at RV speeds?...not sure. Eric thinks there may be some benefit. Bet I get Bob Axsom's juices flowing with that one though!
Finally, of the Super 8's I know of, I don't believe any have been clipped. Kahuna has those long-range tanks in his
, and I imagine standard-length wings keeps his maneuvering wing performance closer to that of the other Team RV aircraft as well. Kahuna, any structural mods to the wings, other than the tanks?Interesting topic Nate!
Cheers,
Bob
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pierre smith
Well Known Member
Say Bob...
...are our tips on my -10 not fairly close to being of Scimitar design? Those and also the two seaters with the "batwing" type tips?
Best,
...are our tips on my -10 not fairly close to being of Scimitar design? Those and also the two seaters with the "batwing" type tips?
Best,
rvmills
Well Known Member
Pierre,
Just back from a trip, and catchin' up. I know what you're saying about the batwing tips, and the scimitar tips do have a bit of that scalloped shape at the trailing edge. However, in talking with Eric, he said the leading edge shape was computer modeled, and the changes in span vs chord are very mathematically specific. If I gathered it all correctly, the math was part of multiple experiments, and the modeling and results surprised them.
In the RV world, the tips that come to mind when I look at the scimitar tips are Jim Smith's triangular tips of Paul Lipps' design. There are differences in shape, but the increased span with minimized area increase due to the shape is something Paul talked a lot about. It almost looks like an elliptical tip in the front half, with a batwing shape in the back half.
I'll ask Eric more about the "why" of the design's success on the L-29 and -39 next time I see him. Interesting stuff tho!
I've been meaning to post this and will get more pics up at a later date (with a better view from the top).
Here's an RV-8A with RV-4 wings and was built by a craftsman from the 'Bakersfield Bunch'
Rosie,
Nice looking plane, for sure! Did you ever hear about its performance with the hybrid wing?
Neat to see all the experimenting going on!
Cheers,
Bob
PaulRomano
Member
Bob--
I just caught your post #19, and I would like to track down something you said:
"...the g limits remain the same with my higher gross weight. That was a key element of the design feature, from what I've been told. "
May I ask who told you this? I spoke to John Harmon personally--probably 15 years ago--and this is pretty much what John said about the original Rocket. But when I pressed him on how he came to those conclusions, he said the wing had been analyzed by an engineer. But I never could find out who did the analysis, the extent of the analysis, and the type of analysis.
The -4 wing and -6 wing are similar (they may be identical, I'm not that familiar with the -6), and the -4 is rated at +6/-3 g at 1375#. Most Rockets are now pushing 2000# at gross, so I think it is a question worth tracking down.
I'm flying an F1 Sport Wing, and love it. But very few Rockets or RVs are operated even close to 6 g's (as I am sure you remember, 6 g's are memorable!).
I'm really not trying to be argumentative, but this is a data point I think is important, and would like to find the seemingly elusive engineer who did the
analysis, and buy him/her a beer. And we could probably reminisce about slide rules.
I just caught your post #19, and I would like to track down something you said:
"...the g limits remain the same with my higher gross weight. That was a key element of the design feature, from what I've been told. "
May I ask who told you this? I spoke to John Harmon personally--probably 15 years ago--and this is pretty much what John said about the original Rocket. But when I pressed him on how he came to those conclusions, he said the wing had been analyzed by an engineer. But I never could find out who did the analysis, the extent of the analysis, and the type of analysis.
The -4 wing and -6 wing are similar (they may be identical, I'm not that familiar with the -6), and the -4 is rated at +6/-3 g at 1375#. Most Rockets are now pushing 2000# at gross, so I think it is a question worth tracking down.
I'm flying an F1 Sport Wing, and love it. But very few Rockets or RVs are operated even close to 6 g's (as I am sure you remember, 6 g's are memorable!).
I'm really not trying to be argumentative, but this is a data point I think is important, and would like to find the seemingly elusive engineer who did the
analysis, and buy him/her a beer. And we could probably reminisce about slide rules.
rvmills
Well Known Member
Paul,
Just saw your PM and this post. Not taken as argumentative at all. Actually, I'd like to know the details too if you can find them. I was told this by my seller, an F1 Sport Wing builder (and a smart guy and trusted friend). Still, word of mouth, and I know you seek more...which aint a bad thing!
Having the same number of ribs in the shorter span was the heart of the discussion, but it was not any more technical than that.
F1 Boss may have some more gouge on it, or perhaps Smokey, Rick G, Tom M or another of the multi-Rocket builders can add what they know on the subject.
Its a valid question, to be sure.
I would agree with your statement that few Rockets or RVs are operated regularly at 6g (I don't)...and unless one's going really fast, its doubtful that one would be able to sustain 6g for very long. However, bury the nose in a maneuver and you could be faced with needing that capability to recover (and don't forget to pull the throttle!!). Hopefully we plan ahead and don't get there...but knowing the airplane can handle its limits at full aerobatic weights is a good thing...and I figure that's the knowledge you're after.
Will shoot a PM to Mark and see if he can comment.
Cheers,
Bob
Just saw your PM and this post. Not taken as argumentative at all. Actually, I'd like to know the details too if you can find them. I was told this by my seller, an F1 Sport Wing builder (and a smart guy and trusted friend). Still, word of mouth, and I know you seek more...which aint a bad thing!
Having the same number of ribs in the shorter span was the heart of the discussion, but it was not any more technical than that.
F1 Boss may have some more gouge on it, or perhaps Smokey, Rick G, Tom M or another of the multi-Rocket builders can add what they know on the subject.
Its a valid question, to be sure.
I would agree with your statement that few Rockets or RVs are operated regularly at 6g (I don't)...and unless one's going really fast, its doubtful that one would be able to sustain 6g for very long. However, bury the nose in a maneuver and you could be faced with needing that capability to recover (and don't forget to pull the throttle!!). Hopefully we plan ahead and don't get there...but knowing the airplane can handle its limits at full aerobatic weights is a good thing...and I figure that's the knowledge you're after.
Will shoot a PM to Mark and see if he can comment.
Cheers,
Bob
