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Old May 22, 2012, 07:55 PM
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College Station, TX
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Here is Sig's reply. I did check out the links Bob Nelson kindly provided. So the wing is on hold for now untill I can document the shape & size for the 2nd link i.e Flying foam .com. they look like they can do the core, though I want the new cores to be exactly the same as the origional(s). Heck I may send them the whole wing just so they'll have in their hands. Alternativatly at this point these foam cores need to be carefully evaulated. You know if they have to come off and they are still holding their shape (which now they look ok w/ the sheeting still mostly on) fiberglassing and vacuum bagging may be a nice option. Retracts will have to be decided on, and I was considering making my own. Well here's the communication from good 'old SIG

Hi Doug,

The way the skin is delaminating from the core make me question how well the rest of the skin is bonded. I would try to slip a thin metal strip like a steel ruler under the skins and see if they come up easily and if so see if the skin can be stripped and the wing recovered. Recovering this wing without the shucks the cores came out of would be a real challenge to keep straight due to the unusual airfoils used. If the core is destroyed in the process and you need a new core there are several places that can cut them. The Core House ( and are a couple that I know of and there are others if you do some research.

Good luck,

Bob Nelson
Technical Customer Service/Design Engineer

SIG Mfg. Co., Inc.
401 South Front St.
PO Box 520
Montezuma, IA 50171-0520

Tel.: (641) 623-5154 Ext.: 120
Fax: (641) 623-3922

-----Original Message-----
From: Doug Christensen []
Sent: Monday, May 21, 2012 8:23 PM
Subject: 1970 Zlin Akrobat Kit

Dear SIG Manufacturing,

It is no secret that everyone in this hobby is very glad to have SIG back and going strong. I have a BIG favor to ask you folks.

You know these days of laser cut & self jigged parts, kit building has never been so easy. Seems to wonder it' s not more popular than ever.

Anyway I am the proud recipient of one of Maxey Hester's 70 inch wingspan Zlin Akrobat kits, partially assembled circa 1970 ?. It's still all there in the box, what has not already been assembled.

There is one problem however, when SIG stopped supplying the 6" wide 1/16" balsa sheeting for the 3" sheeting, and especially over the years the wing's sheeting has split / separated and delaminated. Perhaps more intact then others!

So I have a couple of questions; 1) how can I re-attach the sheeting to the old foam wing? -or- what would be your best recommendation on what should be done to repair this issue. My idea was to somehow find a glue that could not react with the foam and when applied how to hold it to the wings surface. The condition of the foam itself is unknown except at the wing tips where it was never covered seems to be in not bad condition. What's your opinion on the aging process and should it be flown with the original foam core? Should the sheeting be removed and re-installed with new sheeting? I hate to ask this next question, there anyway some new cores could be produced? Note; the wing never saw any covering, this is far as the origional builder got.

Here is a link to RC Groups forum where I have started a thread where you can see some pictures of this kit as I received it. The fuselage is somewhat dried out, but with care I hope to resurrect it also. My whole outlook for this 1969 National Champ is to fly it as a mild sport class plane electrically powered of course.

A battery hatch is planned currently but still reading everything, guide book by Mr. Hester and the prints, still intact.

Thanks again for your expert style and technique in model airplanes.


College Station, TX.
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