Putting a tapered wing on an RV

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davefried

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I came across a post the other day from a member who is finishing up a tapered wing for an RV-4. I did one for an RV-6 some time ago and it turned out quite well. Here is a thread for those who would like to know more and share their ideas.

I had intended an original design until I became aware of the RV-6, it ticked all of my boxes but one. With the fair lines from nose to tail, somehow the rectangular wing stood out as wanting attention.

By the numbers the differences were not revolutionary, a little here and a little there. It was supposed to wind up flying like an RV and it did. What a great little airplane.

Just a taste, more to come...

RV-6 DF-6

Span (ft) 23.0 25.0
Area (ft^2) 111.2 104.2
Taper Ratio 1.0 0.63
AR 4.76 6.00
Twist (deg) 0.0 0.0
OB end Flap (in) 78.0 90.0
OB end Aileron (in) 126.3 140.0
Root Chord (in) 58.0 58.0
Tip Chord (in) 58.0 38.6

DF6 sketch.jpg
 

Toobuilder

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There is at least one major retrofit carbon tapered wing project for RV's in the works. I believe they are tooling up to sell a bunch of them. Will be interesting to see how the performance difference stacks up.
 

scramjetter

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Mar 2, 2020
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Sorry, I couldn't resist, but wouldn't that just be a Mustang II? I prefer the fastback modded Mustang II but the wing's the thing!

I wish they would come out with a nicer looking wing. I would put a few more hours of work into having a nicer looking airplane.
 

Fenix

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I am nearing the completion of changing my standard RV4 to a tapered wing. The wing is complete except for paint. Soon I will swap the rectangular wing for the tapered wing and give some reports on any changes in the "numbers".

The data:

Span increased from 23' to 25'
64% taper
I did incorporate some washout (1.5 degrees)

The construction method, airfoil, etc. is virtually identical to the standard RV4 wing, except that the skin is .032 from root to tip and does not have the seam at mid span where the .032 skin is reduced to .025 for the outer panel.

It appears the planform of Dave's (above) has a straight leading edge and a tapered trailing edge.
Mine is not quite the same. I reduced dimensions from the point of the spar so the airfoil became smaller both fore and aft of the spar but the aft portion gave up more length. Thus my leading edge tapers back but my trailing edge tapers forward even more.

The most notable change (except of course for the planform) is the fuel capacity. I extended the primary fuel tanks outboard to about the same location as is done on the F1 Rockets. This gave me a bit less fuel than the Rockets though because of the reduced dimensions due to taper (I think the fuel reduction would have been less using the straight leading edge planform like Dave's above). The main tanks calculate (I've not yet put fuel in them) to hold 24 gallons each (48 total). I also incorporated Aux tanks that run from the main tanks out to the wingtips. These calculate to hold 12 gallons each (24 total).
The aux tanks have "trap doors" in each rib to slow the outboard movement of fuel that could create a lateral imbalance problem and a couple other modifications to prevent this problem. I expect that with significant fuel in the aux tanks the wings will become quite "heavy" (like a Cessna 310 with the tip tanks full).

It is engineered for 4.4 G's at max takeoff weight, so an aerobatic weight limit could be calculated (obviously no fuel in the outboard tanks), but my intentions are a longer range cross country plane, not an aerobatic plane. Also I expect the roll rate will be slower (even with the aux tanks empty) which is actually a goal to make for a better IFR airplane. If the true airspeed remains the same as the current wing on my plane, using my current fuel consumption rate I will have a range of about 1470 NM with IFR reserve.

If the wing is well behaved I may next build an F4 Raider with the same tapered wing - since I now have all the forming blocks anyway......
 

Fenix

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I stand corrected. Upon closer examination it appears Dave's RV6 planform does also sweep back on the leading edge, contrary to what I previously thought and described. It appears very similar to what I have done.
 

n45bm

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Feb 20, 2019
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Seguin
Oh
I came across a post the other day from a member who is finishing up a tapered wing for an RV-4. I did one for an RV-6 some time ago and it turned out quite well. Here is a thread for those who would like to know more and share their ideas.

I had intended an original design until I became aware of the RV-6, it ticked all of my boxes but one. With the fair lines from nose to tail, somehow the rectangular wing stood out as wanting attention.

By the numbers the differences were not revolutionary, a little here and a little there. It was supposed to wind up flying like an RV and it did. What a great little airplane.

Just a taste, more to come...

RV-6 DF-6

Span (ft) 23.0 25.0
Area (ft^2) 111.2 104.2
Taper Ratio 1.0 0.63
AR 4.76 6.00
Twist (deg) 0.0 0.0
OB end Flap (in) 78.0 90.0
OB end Aileron (in) 126.3 140.0
Root Chord (in) 58.0 58.0
Tip Chord (in) 58.0 38.6

View attachment 108082
wow
I came across a post the other day from a member who is finishing up a tapered wing for an RV-4. I did one for an RV-6 some time ago and it turned out quite well. Here is a thread for those who would like to know more and share their ideas.

I had intended an original design until I became aware of the RV-6, it ticked all of my boxes but one. With the fair lines from nose to tail, somehow the rectangular wing stood out as wanting attention.

By the numbers the differences were not revolutionary, a little here and a little there. It was supposed to wind up flying like an RV and it did. What a great little airplane.

Just a taste, more to come...

RV-6 DF-6

Span (ft) 23.0 25.0
Area (ft^2) 111.2 104.2
Taper Ratio 1.0 0.63
AR 4.76 6.00
Twist (deg) 0.0 0.0
OB end Flap (in) 78.0 90.0
OB end Aileron (in) 126.3 140.0
Root Chord (in) 58.0 58.0
Tip Chord (in) 58.0 38.6

View attachment 108082
Oh wow! This is very similar to an original design of mine that I built. There were differences though, big differences. In my design, the construction was of all wood and both the wings and horizontal tail were tapered also, but they were tapered only on the trailing edge. The wings incorporated a 1 1/2 degrees of washout. The airfoil shapes were 23015 at the root and 23012 at the tip. The vertical tail was quite different too, with the hinge line slanted forward 11 degrees and shaped like my Corby Starlet. What I did was use the RV-6 with the fuselage basically the same shape (so that I could use the -6 canopy and cowling) but with the wings, vertical and horizontal tail shapes and the landing gear very similar to my Corby. My friends called it a wooden RV-6, but it isn't. More like a two place Starlet.
Unfortunately, due to health issues, I had to give it up because I was only eligible for LSA aircraft and its weight and speed did not qualify. Then came Basic Med... The plane is now in Australia. Had I known Basic Med would be a reality. Sigh.... Yes, I have plans drawn, but they won't be available. Sorry.
 

davefried

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Aug 24, 2010
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Location
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Planform details

The original airfoil section is a 13.5% t/c version of the 5 digit NACA 23012. The tip and root airfoil use the same section.

I did not twist the wing reasoning that the taper ratio was modest and any tip stalling misbehavior might be adjusted with a stall strip. Testing has proven that the stall is very gentle with a mild left wing drop.

The front spar is located at .3 Chord and is unswept. The leading and trailing edges are swept back and forward respectively.

My intention was to have a 300-inch span with a geometric chord of 50 inches for an aspect ratio of 6. This gave a slightly reduced wing area of 104.2 ft^2.

To maintain the original chord of 58 inches at the fuselage side, the taper ratio was set at 0.63. Centreline chord is 61.4 inches and 38.6 at the tip.

On the original wing the Mean Aerodynamic Chord is 58 inches and located 69 inches from the centreline, the MAC/4 point is located 2.9 inches ahead of the spar. On this planform the Mean Aerodynamic Chord is 50.8 inches and located 69.3 inches from the centreline, the MAC/4 point is located 2.5 inches ahead of the spar.
 
Last edited:

Victor Bravo

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Pardon my lack of education, but I thought the whole idea of a tapered wing (versus a Hershey bar) was so the maximum G loading could be increased without additional spar weight? If people are building tapered wings and the result is 4.4G (from a post above)..... what did you get for the extra work?

Also, perhaps the engineers here can have pity on a poor uneducated simpleton like me. Wouldn't the fuel in the inboard tanks be what you had to get rid of to allow aerobatic loads on the spars?
 

bifft

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Utah
Also, perhaps the engineers here can have pity on a poor uneducated simpleton like me. Wouldn't the fuel in the inboard tanks be what you had to get rid of to allow aerobatic loads on the spars?
I believe the concern is the outboard weight making it harder to recover from a spin, especially after the fuel moves out to the tips during the spin.
 

davefried

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Pardon my lack of education, but I thought the whole idea of a tapered wing (versus a Hershey bar) was so the maximum G loading could be increased without additional spar weight?
The juggling of performance, weight, strength, manufacturability, cost and marketing makes design fun.

Design groups.jpeg
 
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Victor Bravo

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I agree completely. So then, please explain how juggling all of those factors (and all the fun it created) of putting a taper wing on the airplane could improve the G-loads, or reduce the weight, or improve the performance?
 

davefried

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Aug 24, 2010
Messages
33
Location
Toronto
I agree completely. So then, please explain how juggling all of those factors (and all the fun it created) of putting a taper wing on the airplane could improve the G-loads, or reduce the weight, or improve the performance?
No easy answer there.

I opened by saying that the appearance of the rectangular wing left me wanting something different. That and the satisfaction of turning that something into a flying airplane are entirely subjective. There are other objective benefits and I will try to explain my thinking, stay tuned.
 
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