Substituting wing fabric with plywood

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Dan Thomas

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BTW, the KR1 and 2 did not have foam/glass wings. As originally designed they had a wood structure consisting of main and rear spars and widely spaced ribs. The volume between the ribs was filled with low density foam to give the wing shape. The foam was sanded to shape using the ribs and spars as templates. The wing was then skinned with Dynel fabric (a form of dacron) and polyester resin.

Later builders did switch to fiberglass for the skins because the Dynel/polyester method, while cheap, produced a poor quality structure. I cannot speak to later changes that may have been made. I have not paid much attention to this design for many years.
I wondered about the rigidity of the Dynel/epoxy skin as opposed to fiberglass and polyester. The skin of those wings is the thing that forms a torsion-resistant tube so that the wing can't twist in flight, which could be disastrous. The Taylor's wing used the skinned leading edge back to the spar, which formed the classic D-tube that kept the thing pointed the right direction.

There were other guys that came up with some fixes for the KR's shortcomings. More ribs, for instance, to keep the spars in the right place relative to each other. I think Rand only had root and tip ribs. They might also have added drag bracing, but it's been a long time ago since I read anything about them. I also often wondered about such a fast little aircraft without mass-balanced control surfaces; rule of thumb used to be 150 MPH Vne or higher usually getting balanced surfaces. The Taylor was never that fast.

Such fixes often negate any weight savings due to the foam. Fiberglass cloth and poly resin are especially heavy.

Dan
 

Smutny

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A real world example of what your asking can be found in the Pitts S-1. As Curtis designed it, the wings had built up ribs and fabric covering. There was one company that sold plans for a plywood covered wing called Falcon. I know of two Falcon winged Pitts' that have been going strong in upper level competition for over 20 years. Unfortunately, Falcon no longer exists to sell plans, but you may want to do a little investigating to see if a Falcon winged Pitts is in Europe for you to look at and then compare to standard Pitts wings.
 

djschwartz

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A real world example of what your asking can be found in the Pitts S-1. As Curtis designed it, the wings had built up ribs and fabric covering. There was one company that sold plans for a plywood covered wing called Falcon. I know of two Falcon winged Pitts' that have been going strong in upper level competition for over 20 years. Unfortunately, Falcon no longer exists to sell plans, but you may want to do a little investigating to see if a Falcon winged Pitts is in Europe for you to look at and then compare to standard Pitts wings.
Actually it isn't. The Falcon wing is not just a Pitts wing covered in plywood. It is a fully sheeted wing designed to fit a Pitts. That's a significant difference. And even at that it was not a big success for aerobatic flying because the airframe was not modified to take advantage of the sheeted wing. Air racers like the sheeted wing because of its lower drag. But thay also make other mods if they want to be competitive. A sheeted wing by itself isn't enough of a difference to be worth the effot on this type of aircraft.
 

Smutny

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Actually it isn't. The Falcon wing is not just a Pitts wing covered in plywood. It is a fully sheeted wing designed to fit a Pitts.
I disagree, it is a real world example. I never said it's a standard Pitts wing covered plywood, my point is that it is an airframe that has flown with both fabric covered and plywood covered wings. Hence the part where he should compare the differences.
 

djschwartz

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I disagree, it is a real world example. I never said it's a standard Pitts wing covered plywood, my point is that it is an airframe that has flown with both fabric covered and plywood covered wings. Hence the part where he should compare the differences.
John, this thread started out with a question about simply substituting plywood for fabric. Our point has been that you can't simply "substitute" in that way. You can design a sheeted wing to fit in some cases as has been done with the Falcon wing; but, it's not a simple case of throwing plywood on a Pitts wing. And such a change will have ripple effects through other parts of the aircraft if one wants to get the full advantages of the new wing. Once again the Falcon wing shows that without such corresponding changes the benefits are minimal, if any. The Falcon is certainly a good airplane; but, it is no better than a fabric winged Pitts that also has the other more significant mods it makes as evidenced by the very small number of Falcon's that have been built and the success of people like Sean Tucker with the fabric winged aircraft.
 

Smutny

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Seriously? As far as this thread has wandered from post #1, you're going to hold my comments to that post?

I stand by my example, and never once indicated it was better or worse. Just an example of one airframe with two different wing constructions for the OP to look at if he found one in Europe.

Good day.
 

djschwartz

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Seriously? As far as this thread has wandered from post #1, you're going to hold my comments to that post?

I stand by my example, and never once indicated it was better or worse. Just an example of one airframe with two different wing constructions for the OP to look at if he found one in Europe.

Good day.
Sorry, John. Wasn't trying to be rude or anything. Sorry it came across wrong.

Good day to you, too.

Dave
 

DangerZone

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Seriously? As far as this thread has wandered from post #1, you're going to hold my comments to that post?

I stand by my example, and never once indicated it was better or worse. Just an example of one airframe with two different wing constructions for the OP to look at if he found one in Europe.

Good day.
A friend of ours has built such a Pitts with plywood many years ago and some people were persistent to buy it from him, it had great performance. Yet I forgot the details, next time that I see him I'll ask him about the wings and all the changes made.
 
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