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Wittman Tailwind modified to meet E-LSA?

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arp67

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I know the Wittman Buttercup design can meet the ELSA specs, but was wondering if anyone has ever installed longer wings on a W8 or W-10 Tailwind using a thicker, flat bottomed airfoil (like a J-3Cub)? This wing change would probably require wing struts like a Cub as well. I'm not talking about trying to install or adapt J-3 Cub wings onto an existing Tailwind, but rather to redesign a Tailwind wing to be longer and use a Cub-like airfoil.

I know some Tailwind enthusiasts are probably thinking, "Why would you do that? The Tailwind was designed for speed!" I just think it is one of the best looking high wing monoplanes you can build, but would prefer to fly something a little slower and in the LSA range.
 

mcrae0104

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There may be better choices available than the Cub's USA-35b foil. Unless you want a really large wing, you'd probably end up selecting something with a healthy amount of camber (which, by virtue of the drag that comes with it, will also help you not outrun the LSA Vh limit). If you could get an unlapped Cl=1.6 (3D, not just the book value for the 2D foil) then you would need something in the neighborhood of 120 ft2 of wing area--that doesn't seem too far from being reasonable. The area required is proportional to your Cl. Of course you would need to redesign the spar and check the wing design, but you would also need to take into account the larger pitching moment that comes with more camber, so you may be enlarging the tail as well.
 

Marc W

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There was a Tailwind project on Barnstormers that was advertised as an LSA designed by Calbie Woods. You may know Woods designed the metal wing for the Tailwind.

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Tailwind LSA Project 90% Compl
TAILWIND LSA PROJECT 90% COMPL • $8,999 • ESTATE SALE • Started, designed by Tailwind designer Callbie Woods metal wings 90% complete. email for more, pics • Contact Thomas Gregorski , Friend of Owner - located Kenly, NC United States • Telephone: 252-205-7017 • Posted September 14, 2020 • Show all Ads posted by this AdvertiserRecommend This Ad to a FriendEmail AdvertiserSave to WatchlistReport This Ad
 

Mcmark

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Been discussed a bunch on the Tailwind group. Consensus is can’t be done in any original configuration and after that won’t be a Tailwind.
Build a ButterCup or bug Jim Clements, who has built what he calls a ButterBurger, which is a bigger airplane with 2 struts per side to draw a set of plans.
 

cluttonfred

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Just to be clear, unless you are setting up a production facility, you are not actually talking about E-LSA. E-LSA is a quick-built kit (does not need to meet 51% rule) that allows a builder to assemble an approved LSA normally built in a factory. What you are really talking about is an experimental amateur-built (E-AB) airplane that meets the definition of an LSA. That said, even the Buttercup is right at the edge of meeting the definition of an LSA because the LSA definition requires a *clean* stall speed of under 45 knots. From the FAA Sport Pilot brochure:

(4) A maximum stalling speed or minimum steady flight speed without the use of lift-enhancing devices (VS1) of not more than 45 knots CAS at the aircraft's maximum certificated takeoff weight and most critical center of gravity.
 
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TFF

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The elusive LSA Tailwind. On the Tailwind group, one claimed to have built one with a O-200 and at Oshkosh someone gave out revised wingtip airfoil info that was supposed to drop the stall. There is a thing called a Daphne that was a not quite TW and pre plans built Buttercup like plane. Every once in a while a set of plans show up or a plane shows up on barnstormers.

The tailwind wing spar is too thin to extend the wing as built. If you want a different wing, you will need to do homework. A W8 with a small Continental, no electrical, starter, radio is a much more docile plane than the RV upseter W10. You have to make it light, like 600 lb empty like it was designed to be. I believe the W8 airfoil is flat bottomed. It’s different than the W10.
 

cluttonfred

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I ran the numbers quickly on the original W-8 Tailwind with the 4309 airfoil (CLmax 1.4), AR 5.21, 20.92 ft span, 84 sq ft area, at the stated gross of 1235 lb. I got a clean stall speed of about 64 mph, which means even with flaps I wonder if the claimed stall of 55 mph might be a little optimistic. You can make an LSA that looks like a Tailwind, and there might be a market for that, but no amount of tweaking is going to make a Tailwind into an LSA.
 

cluttonfred

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As TFF said, the Tailwind wing is quite thin and optimized by a talented designed. You can’t make a big increase in the area without a major redesign of the whole wing structure, much more than a tweak.

I agree with your analysis on the numbers, but why would a big increase in wing area not do the trick?
 

mcrae0104

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As TFF said... You can’t make a big increase in the area without a major redesign of the whole wing structure...
Yeah, that's actually what I suggested in post #3: a redesign of the wing, with a new foil and a new spar and an area increase of > 40%. I didn't call it a "tweak," but it would get the stall speed down, would it not?
 
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stanislavz

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Try to get plans of original W8 Tailwind, its was lighter. Change engine to any of rotax family 912s or 914.. And put smaller fuel tank. Add wing tips too. According to my math - it is was close to ok on stall speed. LSA stall is on clean airframe or with flaps ?
 
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BJC

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I ran the numbers quickly on the original W-8 Tailwind with the 4309 airfoil (CLmax 1.4), AR 5.21, 20.92 ft span, 84 sq ft area, at the stated gross of 1235 lb. I got a clean stall speed of about 64 mph, which means even with flaps I wonder if the claimed stall of 55 mph might be a little optimistic.
I don’t know if any actual testing has been done to verify it, but Witt claimed that the fuselage produced a significant amount of lift. Did you allow for that in your analysis?
You can make an LSA that looks like a Tailwind, .... but no amount of tweaking is going to make a Tailwind into an LSA.
Agree with that.


BJC
 

stanislavz

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And plus remember, that tailwind puts pilots behind cg to balance engine in front. If you put engine which will be lighter than 0-200 and derivatives - you will have to put pilots to the front, and maybe move fuel tank to the wing..

CG is in ankle area ?

1600162283238.png
 
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Doran Jaffas

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I think overall my suggestion would be that if you want an LSA type aircraft just find something that you can live with design wise. The Tailwind has a history that is part of its appeal and to redesign it even though that is what the experimental aircraft association is all about in a lot of ways, it just seems that it would take more than it is worth to do it and also take away from a lot of the original history of this aircraft design.
One would also be risking damaging the reputation of the Tailwind because the uninitiated would see an airplane that looks similar to it and if that design was not stable and had other flaws would Mar the reputation by the uninformed.
 

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stanislavz

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One would also be risking damaging the reputation of the Tailwind because the uninitiated would see an airplane that looks similar to it and if that design was not stable and had other flaws would Mar the reputation by the uninformed.
We had this discussion on Tailwing group with you before, and i do agree on some point, and disagree on another.

There is a CAFE report on Tailwind an Pipistrel virus. And both have similar / close drag area. But are totally different technology. Can you merge TW wings to Virus ? Or vice verse ang get a nice and safe plane - no..

But you could take Buttercup wing and merge it to TW. Was done, and more than one time.

My interest on TW was only to rear part of the fuselage. Due to:
1. It have low drag, due to laminar flow as shown in same CAFE report
2. it provides some lift.

But if you wish redesign it - it will be something totally different.

But - in today flow simulation technology - one could alter shape of rectangular fuse to achieve minimum drag at cruise and maximum lift at landing
 

TFF

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W8s span a lot of years. The original W8 tested by the Mississippi State University grossed 1075. No nothing, as it was 1953. No radio, starter, generator, battery, or chewing gum. The same design has had O-300s bolted on, even back then, and no one is satisfied building a homebuilt unless it’s heavier than book. 1235 or some other quote is a 60’s number after years of selling plans and bumping numbers up. The original was light. Way lighter than any other.
 

Turd Ferguson

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I don’t know if any actual testing has been done to verify it, but Witt claimed that the fuselage produced a significant amount of lift.
Steve took the first Tailwind (magic / flying carpet) to Dr. August Raspet in MS for some aerodynamic measurements in 1956. A subsequent article was published here: http://acversailles.free.fr/documentation/08~Documentation_Generale_M_Suire/Aerodynamique/Couche_limite/Flight_Measured_Aerodynamics_of_Wittman_s_Tailwind.pdf

Some of the tests were very interesting, for example removing the propeller, sealing the cowl opening and towing the plane to altitude to measure gliding performance at various speeds. Good stuff !
 
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