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Clipwing RV15

Chukill

Chukill

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The RV15 is almost exactly what I want to build next. I like the high wing, the sturdy rough field landing gear, the huge cargo capability, and you know, "the thing". However, the 140 kt cruise speed burning 10 gallons an hour is less than optimum. I am used to much faster speeds and efficiencies from my other RV builds. What if some compromise to the short field, runway performance could be sacrificed in exchange for another 10 or 20 kts of cruise speed?
Would a reduction in the wing span allow for such an increase? Would that reduction still allow for a reasonable stall speed and still be MOSAIC compliant?
In my 30 years of flying RVs, I have never had a need to operate off a 300 foot runway. I have wished for more robust gear many times, but never needed to land on a sandbar.
Is there a clever engineer out there can run some numbers to estimate the amount of wing area that could be removed to get the higher cruise number and what that would do to the stall speeds, and runway requirements?
If this compromise wing could yield the desired numbers, maybe Vans could offer it up as an option.
A builder could also shorten the wings and control surfaces and call it something other than an RV if Vans won't play.
Flame away.
 
If 140kts is the target cruise I'd think you could go faster by pushing in the throttle and burning more fuel. But 150- 160kts at 10gph seems like a lot to ask from a bit shorter wings on a strut braced fixed gear plane.
 
Im in the same boat. Want a high wing, but cant get used to going slower after flying a -7 for 10+ years.
Was looking at the Glassair Sportsman as the fastest high wing kit. Good thing I didnt since they closed and went to China.
Have not seen an equivalent high wing regarding speed. Ended up wimping out and starting a -14 instead.

My engineering intuition says that shortening the thick -15 wing wont get you much.
 
Chukill said:
If this compromise wing could yield the desired numbers, maybe Vans could offer it up as an option.
Click to expand...
I asked the same thing a couple years back and it didn't gain much traction. I find a shorter wing interesting not only for a cruise speed increase, but a wing loading increase as well so you're not pounded by turbulence.
 
FlyNSoCal said:
I asked the same thing a couple years back and it didn't gain much traction. I find a shorter wing interesting not only for a cruise speed increase, but a wing loading increase as well so you're not pounded by turbulence.
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Gee-Im not so crazy afterall---my RV10 retract/lite turbine was a crazy idea---but even used TBM700s are $1.5M +.
 
Mel said:
I want an airplane that goes 250 mph, burning 4 gallons per hour, gets off in 300' and seats 6 comfortably. What's the problem?
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I want an airplane with the performance of a GameBird GB1, the short field capabilities of a CubCrafter Cub UL, fuel burn of a Van's RV-12iS all with the air conditioned comfort and roominess interior and range of a King Air. Oh, and at the price of an early 1970's Citabria in average condition.
 
Chukill said:
The RV15 is almost exactly what I want to build next. I like the high wing, the sturdy rough field landing gear, the huge cargo capability, and you know, "the thing". However, the 140 kt cruise speed burning 10 gallons an hour is less than optimum. I am used to much faster speeds and efficiencies from my other RV builds. What if some compromise to the short field, runway performance could be sacrificed in exchange for another 10 or 20 kts of cruise speed?
Would a reduction in the wing span allow for such an increase? Would that reduction still allow for a reasonable stall speed and still be MOSAIC compliant?
In my 30 years of flying RVs, I have never had a need to operate off a 300 foot runway. I have wished for more robust gear many times, but never needed to land on a sandbar.
Is there a clever engineer out there can run some numbers to estimate the amount of wing area that could be removed to get the higher cruise number and what that would do to the stall speeds, and runway requirements?
If this compromise wing could yield the desired numbers, maybe Vans could offer it up as an option.
A builder could also shorten the wings and control surfaces and call it something other than an RV if Vans won't play.
Flame away.
Click to expand...
To answer your question, that would not increase the cruise speed that much.

The stall speed would increase. The runway length would increase. The rate of climb would decrease too.

If you are considering a change of this magnitude, obtain an aircraft design book and work through the numbers yourself.

Dave
 
It's an interesting thought exercise for sure, but to me it just doesn't seem feasible. For one thing, anything other than changing the wingtips would require changing the span wise length of the ailerons and/or flaps and overhauling where they attach to the wings. You're firmly into design engineer and test pilot country with that one.

Also, while I'm not an engineer, I have been around a fair bit. I find it hard to believe that on an airplane with wing struts you could gain 10-15% on the top end (basically what you're asking) just by shortening the wing unless you chop about 1/2 of it off. I'll be interested to see if someone comes up with some numbers to either validate my opinion or show that I'm way off base.

Seems like the lowest hanging fruit to achieve at least part of your goal would be to put wheel pants on it. I don't think I've ever seen pictures of the prototype with wheel pants so I assume that the flight test numbers are with those big old wheels hanging out in the breeze. If a guy could make the air behave around those, I'll bet you could see a 5-10kt increase basically for free.
 
Amadeus said:
I want an airplane with the performance of a GameBird GB1, the short field capabilities of a CubCrafter Cub UL, fuel burn of a Van's RV-12iS all with the air conditioned comfort and roominess interior and range of a King Air. Oh, and at the price of an early 1970's Citabria in average condition.
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I have simple tastes -- I just want a 4-seat tricycle version with large cargo space. Sorta an RV version of a 206.
 
Desert Rat said:
Seems like the lowest hanging fruit to achieve at least part of your goal would be to put wheel pants on it. I don't think I've ever seen pictures of the prototype with wheel pants so I assume that the flight test numbers are with those big old wheels hanging out in the breeze. If a guy could make the air behave around those, I'll bet you could see a 5-10kt increase basically for free.
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If you're putting wheel pants over the bush wheels, you'll be most of the way to a set of floats... :p
 
"The RV15 is almost exactly what I want to build next. I like the high wing, the sturdy rough field landing gear, the huge cargo capability, and you know, "the thing". However, the 140 kt cruise speed burning 10 gallons an hour is less than optimum. I am used to much faster speeds and efficiencies from my other RV builds. What if some compromise to the short field, runway performance could be sacrificed in exchange for another 10 or 20 kts of cruise speed?"

My backyard approach to judging speed potential of different designs: go to OSH & stand 10' in front of each candidate design & observe it's frontal (wetted) area.
Murphy Rebel - all the back country capabilities you want, maybe 120 Knot cruise
RV-15 - probably won't be there this year to look at, but promising the 140 Knot cruise is pretty good considering it's proposed capabilities!
Any RV - smaller frontal area, kinda a no brainer figuring out why it would be 20 Knots faster
Any Lancair - tiny frontal area, no cargo capacity, no wonder they have 20+ Knots on our planes, but you know what a Lancair owner would say if you suggested they ad a hi-lift airfoil & big tires to get into a back country strip?

Pick the aircraft DESIGNED for YOUR mission...
 
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Ralph Inkster said:
Murphy Rebel - all the back country capabilities you want, maybe 120 Knot cruise
RV-15 - probably won't be there this year to look at, but promising the 140 Knot cruise is pretty good considering it's proposed capabilities!
Any RV - smaller frontal area, kinda a no brainer figuring out why it would be 20 Knots faster
Any Lancair - tiny frontal area, no cargo capacity, no wonder they have 20+ Knots on our planes, but you know what a Lancair owner would say if you suggested they ad a hi-lift airfoil & big tires to get into a back country strip?

Pick the proper aircraft design for YOUR mission...
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My take on your list of airplane:

Murphy Rebel - Great airplane, no builder/factory support
RV-15 - $$$ Expensive kit plane, good factory support
Any Low Wing RV - Great economical airplane with flimsy landing gears
Any Lancair - Fast 2-seat airplane designed for one person
 
Ralph Inkster said:
"The RV15 is almost exactly what I want to build next. I like the high wing, the sturdy rough field landing gear, the huge cargo capability, and you know, "the thing". However, the 140 kt cruise speed burning 10 gallons an hour is less than optimum. I am used to much faster speeds and efficiencies from my other RV builds. What if some compromise to the short field, runway performance could be sacrificed in exchange for another 10 or 20 kts of cruise speed?"
My backyard approach to judging speed potential of different designs: go to OSH & stand 10' in front of each candidate design & observe it's frontal (wetted) area.
Murphy Rebel - all the back country capabilities you want, maybe 120 Knot cruise
RV-15 - probably won't be there this year to look at, but promising the 140 Knot cruise is pretty good considering it's proposed capabilities!
Any RV - smaller frontal area, kinda a no brainer figuring out why it would be 20 Knots faster
Any Lancair - tiny frontal area, no cargo capacity, no wonder they have 20+ Knots on our planes, but you know what a Lancair owner would say if you suggested they ad a hi-lift airfoil & big tires to get into a back country strip?
Pick the proper aircraft design for YOUR mission...
Click to expand...
Although frontal area IS a factor, it's not the only factor. Airfoil in a big one. Example, Compare the Piper J-3 to the Taylorcraft. The Taylorcraft has substantially more frontal area and the same hp as the J-3, yet it cruises much faster. The big secrete here is the wing airfoil.
 
Just one data point for fun. In 1931 John Livingston's Monocoupe 110, with the stock 32' wing, was running 145 mph at the air races. He retuned to the factory and they clipped the wing 9' down to 23'. Speed went up 30 mph to mid 170's.

Over the next year he kept tweaking and tuning, fairing everything possible, smaller tail feathers, smaller wheels and brakes. Eventually got his race speeds over 200 mph.


N501W-front.jpegN501W-rear.jpeg
 
Chukill said:
The RV15 is almost exactly what I want to build next. I like the high wing, the sturdy rough field landing gear, the huge cargo capability, and you know, "the thing". However, the 140 kt cruise speed burning 10 gallons an hour is less than optimum. I am used to much faster speeds and efficiencies from my other RV builds. What if some compromise to the short field, runway performance could be sacrificed in exchange for another 10 or 20 kts of cruise speed?
Would a reduction in the wing span allow for such an increase? Would that reduction still allow for a reasonable stall speed and still be MOSAIC compliant?
In my 30 years of flying RVs, I have never had a need to operate off a 300 foot runway. I have wished for more robust gear many times, but never needed to land on a sandbar.
Is there a clever engineer out there can run some numbers to estimate the amount of wing area that could be removed to get the higher cruise number and what that would do to the stall speeds, and runway requirements?
If this compromise wing could yield the desired numbers, maybe Vans could offer it up as an option.
A builder could also shorten the wings and control surfaces and call it something other than an RV if Vans won't play.
Flame away.
Click to expand...
Order a 15 without the wing kit and a 10 or 14 wing. then strengthen/ redesign the cabin area to carry without struts and you'd be there. That's my TLAR engineering assessment. Of course it may actually look a bit wrong. Dihedral in a high wing (like my old rc trainer plane). But beauty is subjective.
 
azrv6 said:
Just one data point for fun. In 1931 John Livingston's Monocoupe 110, with the stock 32' wing, was running 145 mph at the air races. He retuned to the factory and they clipped the wing 9' down to 23'. Speed went up 30 mph to mid 170's.

Over the next year he kept tweaking and tuning, fairing everything possible, smaller tail feathers, smaller wheels and brakes. Eventually got his race speeds over 200 mph.


View attachment 66712View attachment 66715
Click to expand...
200mph with struts, tail wires, and bungee gear from a fat 125hp radial. I'm pretty sure clipped wing Cubs and T-carts went faster than before the wing was shortened. Hmmmm.... Is the OP is onto something? Naw us keyboard naysayers gotta be right.
 
azrv6 said:
Just one data point for fun. In 1931 John Livingston's Monocoupe 110, with the stock 32' wing, was running 145 mph at the air races. He retuned to the factory and they clipped the wing 9' down to 23'. Speed went up 30 mph to mid 170's.

Over the next year he kept tweaking and tuning, fairing everything possible, smaller tail feathers, smaller wheels and brakes. Eventually got his race speeds over 200 mph.


View attachment 66712View attachment 66715
Click to expand...

All of those mods did indeed increase the speed; unfortunately, that increase comes with a bunch of trade offs.

Aircraft design is always a compromise. There is no perfect design that fulfills every mission.

The solution, of course, is to have multiple aircraft, each with its own specific mission. Fortunately, our RVs may not be exceptional at any one thing but they are really good at a lot of things. It is a good compromise.
 
Chukill said:
The RV15 is almost exactly what I want to build next. I like the high wing, the sturdy rough field landing gear, the huge cargo capability, and you know, "the thing". However, the 140 kt cruise speed burning 10 gallons an hour is less than optimum. I am used to much faster speeds and efficiencies from my other RV builds. What if some compromise to the short field, runway performance could be sacrificed in exchange for another 10 or 20 kts of cruise speed?
Would a reduction in the wing span allow for such an increase? Would that reduction still allow for a reasonable stall speed and still be MOSAIC compliant?
In my 30 years of flying RVs, I have never had a need to operate off a 300 foot runway. I have wished for more robust gear many times, but never needed to land on a sandbar.
Is there a clever engineer out there can run some numbers to estimate the amount of wing area that could be removed to get the higher cruise number and what that would do to the stall speeds, and runway requirements?
If this compromise wing could yield the desired numbers, maybe Vans could offer it up as an option.
A builder could also shorten the wings and control surfaces and call it something other than an RV if Vans won't play.
Flame away.
Click to expand...

If you build one, can't you clip the wings yourself?
Critiquing a plane without the real model being available is a waste of time.
It will be redesigned.
 
rocketman1988 said:
All of those mods did indeed increase the speed; unfortunately, that increase comes with a bunch of trade offs.
Aircraft design is always a compromise. There is no perfect design that fulfills every mission.
The solution, of course, is to have multiple aircraft, each with its own specific mission. Fortunately, our RVs may not be exceptional at any one thing but they are really good at a lot of things. It is a good compromise.
Click to expand...
It's called "Total Performance"! Seems like I've heard that term somewhere before. Maybe back in the '70s or '80s.
 
Mel said:
It's called "Total Performance"! Seems like I've heard that term somewhere before. Maybe back in the '70s or '80s.
Click to expand...
That may be what it is (was) called but as good as our RVs are, they are still but a compromise...
 
As a sidebar note...

Our Glasair Sportsman on trike gear gained 7 knots with the addition of wheel pants. This is over and above the speed increases associated with the gear leg fairings (yeah, some folks fly them without gear leg fairings - dunno why). Well designed wheel pants and gear fairings can make some pretty fantastic improvements in speed. Poorly designed ones, well, not so much.
 
Canadian_JOY said:
As a sidebar note...

Our Glasair Sportsman on trike gear gained 7 knots with the addition of wheel pants. This is over and above the speed increases associated with the gear leg fairings (yeah, some folks fly them without gear leg fairings - dunno why). Well designed wheel pants and gear fairings can make some pretty fantastic improvements in speed. Poorly designed ones, well, not so much.
Click to expand...
Removable wheel pants over tundra tires for X-country flight. Then removed at nearest hard surface airstrip to back country strips.
 
gasman said:
Removable wheel pants over tundra tires for X-country flight. Then removed at nearest hard surface airstrip to back country strips.
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Given the size of a tundra tire, the size of a wheelpant for it would be ridiculous.
 
PhatRV said:
Any Low Wing RV - Great economical airplane with flimsy landing gears
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I feel like I should defend at least the newer models: The RV-12, RV-14, and the certified RV-10, all went through a very thorough and hard series of landing-gear tests, as shown in this video. (The RV-12 gear was subsequently beefed up even more, originally in the RV-12iS and then in a retrofit kit for non-iS "legacy" RV-12s). I would not call their gear "flimsy".

As for the topic of the thread... Like others, I feel like clipped wings would not increase your speed much, because you would only remove a small fraction of your wetted area: It's a fairly big airplane with a fairly tall and wide and boxy fuselage, and lots of stabilizer area. As others have pointed out; Good fairings for the wheels and the legs and the intersections (where the strut meets the wing, where the wings and legs and stabilizers meet the fuselage...) would make the biggest difference. Using flush rivets would probably also help a little.
 
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AirShowFan said:
I feel like I should defend at least the newer models: The RV-12, RV-14, and the certified RV-10, all went through a very thorough and hard series of landing-gear tests, as shown in this video. (The RV-12 gear was subsequently beefed up even more, originally in the RV-12iS and then in a retrofit kit for non-iS "legacy" RV-12s). I would not call their gear "flimsy".

As for the topic of the thread... Like others, I feel like clipped wings would not increase your speed much, because you would only remove a small fraction of your wetted area: It's a fairly big airplane with a fairly tall and wide and boxy fuselage, and lots of stabilizer area. As others have pointed out; Good fairings for the wheels and the legs and the intersections (where the strut meets the wing, where the wings and legs and stabilizers meet the fuselage...) would make the biggest difference. Using flush rivets would probably also help a little.
Click to expand...

I think the speed of the RV15 is perfectly fine for me if I build it for the mission it was designed for. Everything is a compromise. I like to do sight seeing while flying and the highwing RV15 fits perfectly. Ingress and egress in the RV15 is easier. Unfortunately, given the anticipated very high price-to-build, it is mostly likely not the airplane for me. Maybe I can pick up a neglected project down the road and work on it while in retirement.
 
There is a data point in the RV world. The sport winged Rocket is a clipped RV4 wing. The fuselage is actually wider than the RV4 yet the aircraft in its 4 cylinder configuration is still faster than a RV4. The tradeoff is of course a higher stall speed. It’s probably about 6 knots but in an off field Landing that’s a lot more kinetic energy. On the plus side roll response is better and the feel is excellent. Pattern work on a bumpy day is improved as well. You are however as mentioned going faster and need more runway plus more frequent tire and brake changes. I also suspect the aircraft would perform better at higher altitudes with the full length wing if you don’t mind dealing with Oxygen.
 
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