L

Larry DeCamp

Well Known Member
Friend
Before you start to burn me for a stupid question, my objective would be to use RV9 wings for a light weight single seat LSA with 100 HP engine ( 0200 I have surplus). I already have an RV-3B and originally planned to use a -3 wing kit for the LSA project.
The Vans data proclaiming the efficiency and 44 MPH stall caused me to wonder why not use -9 wings? The question is, how complex will it be to reduce the span to something less than 28' ( 125 SF) without creating an engineering nightmare ?? Any feed back is appreciated.
 
Not possible...

Good luck in your endeavor, but in my experience, it's not possible to prevent engineers from having nightmares... ;)
 
Not quite sure what your point would be.
Shortening the wing would increase stall speed and increase cruise speed. Sounds counter intuitive for LSA.
 
Answer for Mel

Thanks Mel. My logic is assuming the aircraft weight would be significantly less than a -9 and the wing /flap design has some superior feature for generating lift. Therefore, a 750 lb aircraft should achieve the 44 MPH stall and other performance efficiencies with less wing area. The whole idea is to use a smarter wing than the -3 (assuming it is the first and dated ). Again, the trade offs may not be worth the trouble, I just thought I would run the concept past the -9 group who should be most familiar with any real benefits from the -9 wing.
 
It's always good to see folks thinking outside the box Larry! In this case, however, I think the problem is that a portion of the efficiency gain from the -9 wing is in it's aspect ration - and clipping the span down will reduce the AR, losing a large portion of that gain. Someone smart would have to do the math to see if you'd gain anything in the trade.

Besides, you have a -3 to finish - get to it! :)

Paul
 
Larry DeCamp said:
Thanks Mel. My logic is assuming the aircraft weight would be significantly less than a -9 and the wing /flap design has some superior feature for generating lift. Therefore, a 750 lb aircraft should achieve the 44 MPH stall and other performance efficiencies with less wing area. The whole idea is to use a smarter wing than the -3 (assuming it is the first and dated ). Again, the trade offs may not be worth the trouble, I just thought I would run the concept past the -9 group who should be most familiar with any real benefits from the -9 wing.
Click to expand...
I am no aeronautical engineer so any of my comments should be evaluated with that taken into consideration. Weight is not going to be the sole factor, in fact really not even the most important factor, to contributing to stall speed. The shape of the wing, the chord and the length of the wing are integral parts of the equation when looking at what the stall characteristics of a particular wing will be. The aspect ratio of the 9 wing (which relies just as much on the length as anything else) is a huge factor in the stall characteristics of this airplane. The length of that wing in relation to the chord and the shape of the airfoil is a huge factor in what the stall speed will be. Cutting down the length of the wing without addressing other factors will most likely increase the stall speed of that wing (Again, keep in mind this opinion is from a layman's perspective, not one of engineering expertise).

I think Mel is telling it like it is.

If you are thinking down these lines why not look into mounting the 9 wing in its unaltered form to the 3 fuse. the light weight 3 fuse combined with the high aspect ratio 9 wing will most assuredly create some interesting performance characteristics. No idea what those would be but interesting none the less.

Dang it Paul, you beat me to the punchline. I just couldn't type fast enough.
 
RVbySDI said:
If you are thinking down these lines why not look into mounting the 9 wing in its unaltered form to the 3 fuse. the light weight 3 fuse combined with the high aspect ratio 9 wing will most assuredly create some interesting performance characteristics. No idea what those would be but interesting none the less.
[/I]
Click to expand...

I think that would be called a "kite".:D
 
Difficult to mate the wings to an RV-3 fuselage

Hi,

The idea of using a higher aspect ratio wing for a single-seat LSA is a good one.

The basic RV-9 wing is not a bad choice, and you might be OK to just clip one or two rib bays off the tip, with some loss in aileron span, although, you could have the aileron continue out past the last rib and into the tip area -- even all the way to the tip.
Also the wing is heavier than it would need to be (and stronger) because it was designed for a heavier airplane. But the weight penalty is small - its just the extra beefiness in the spars that would not be there if the spars were optimized for a single-place LSA.

The real challenge would be mounting this wing into an RV-3 fuselage. The RV-9 has a very different spar root connection, and so you would have to build a new fuselage bulkhead that connected to the RV-9 spars. This could probably be done by modifying a normal RV-9 center bulkhead (F-904). The carrythrough bars would get cut shorter and new spar bolt holes drilled and reamed in them. The rest of the F-904 components would get split in the middle and re-joined with the proper width with some doubler plates to rivet them together. Then the whole thing would get riveted into the RV-3 fuselage in place of the normal F-304 bulkhead.
 
Last edited:
Larry DeCamp said:
Thanks Mel. My logic is assuming the aircraft weight would be significantly less than a -9 and the wing /flap design has some superior feature for generating lift. Therefore, a 750 lb aircraft should achieve the 44 MPH stall and other performance efficiencies with less wing area. The whole idea is to use a smarter wing than the -3 (assuming it is the first and dated ). Again, the trade offs may not be worth the trouble, I just thought I would run the concept past the -9 group who should be most familiar with any real benefits from the -9 wing.
Click to expand...

Also remember that the "flaps" don't count for LSA stall speed.
LSA stall speed is to be achieved "without the use of lift enhancing devices".
 
Seems that the general idea is to make an LSA that weighs the same as an RV-12, has the same power, and has slightly less wingspan and less area. I think the RV-12 has a similar airfoil to the RV-9, but I'm not sure. The -12 certainly flies nicely.

Why not use RV-12 wings as-is? The performance is excellent.

For the same weight and power, if your new wingspan is less than the 26' 9" span of the RV-12, you'll lose climb. The areas of the RV-9 and the RV-12 are similar, at 124 and 127 square feet.

I'd bet that the RV-12 wings are lighter, but of course they don't have generous wing tanks.

Dave
 
Larry, Just build stock wings and add 18" extensions. That will make the wing 1" shorter that the 4 and 6 but still not the same profile. The wing load will then be 10.14 # per sqft. at 1050 gross wt. The 12 is at 10.4#psqft. Now just figure out how to keep the tail from stalling first. And how far fwd you will need to make the O200 balance out.

My plan is to use an O320 for proper w+b and work with it till I get the max 138 mph. All of my plans are on hold..... waiting for the FAA to honor the drivers license in place of a medical.

The main thing for me is to have a stock 3 by removing parts if I ever wanted it.
 
Single place LSA

Thanks for all the high quality input, it was educational for me since I am a 'gear head' not an 'aero'. I will follow up with GSAMAN since he seems to be on the same page...Larry
 
You must log in or register to reply here.