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Old Jun 09, 2014, 08:12 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
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F ormer thickness?

With all the great many kits that have been built here, thought you guys would be the best to ask. I recently aquired a KMP F-18 kit. Originally designed as a pusher, and Yes--it's a foamy!

My plan it to build it just as Y/A builds there F-18 single. Removable wings, (spars from Y/A) JF90/Het 1200Kv, and retracts (see pic ) All of these are tied into formers 3 and 4. [below]

So what would you suggest for former thickness.??

It will also be glassed , and some on the inside where needed.
Just in the planning stage now, and working out materials needed.
TIA
Cooler
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Old Jun 09, 2014, 09:18 PM
Registered User
St. Mary, Maryland, United States
Joined Dec 1996
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1/4" birch, get rid of the hole at the bottom of the spar where the 90 degree direction change is and back up all 3 thin spots front and back with carbon tow / thin ca
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Old Jun 09, 2014, 11:49 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
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Thanks Chris, that had been my first thought. I only asked, because in TGoodwin's thread-- Yellow Aircraft F/A-18 build/conversion thread

http://www.rcgroups.com/forums/showt...ft+F+18&page=3 post #34, he made the comment--

Quote:
The original former is 3/16" birch ply and is part of the wing structure and also holds the main retract mounting plate. I decided to use a 1/4" lite ply and will very likey reenforce the load bearing areas to be sure it can handle the flight and landing loads.
Regarding your other comments, will do.

Thanks again.
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Old Jun 10, 2014, 12:09 AM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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i think 1/8" to 3/16 5ply would be good ...maybe a doubler in the "arm pit" area of the former. some of those hole should be deleted as was mentioned. light ply is junk ...you'd be better off using balsa wood with a layer of 1/64 ply lamanated to each side.
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Old Jun 10, 2014, 12:28 AM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
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Rodger, I had also thought of the Bud Nosen ply that you and Gary used on your F-20 , as I have used it to. 1/8" 6-ply. Wasn't sure it was thick enough to hold the screws for the wing spars, although I believe that once they are drilled and right position is found, they also use Hysol??

Only wish BN had 5-ply 3/16", all he shows is 4-ply

Thanks for your input, most appreciated.
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Old Jun 10, 2014, 11:35 AM
turbonut's Avatar
upland CA
Joined Dec 2004
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I am with Roger. Use 1/8th 5 ply with a 1/8th 5 ply doubler in the high load areas.I rellay need to see how much room you have around the fan top and bottom. If you build exact to the pics any thing beyond the narrow area is not doing much work so no need to double it there. And loose the three holes on each side as they will not work for sure
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Old Jun 10, 2014, 12:45 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
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Thanks turbonut. That 1/8" 6-ply is some beautiful stuff to work with. Direct from Finland. As you and Rodger said, doublers are in orderin high stress areas. Wasn't so much worried about the formers supporting the fan and wing spars, but more in supporting the retract on landings (you know there will be a few hard ones)
I'll do as I have done with my Scorpion build, and glass those inside portions of the fuse where the formers will be glued.


Quote:
I rellay need to see how much room you have around the fan top and bottom.
Just did a quick measure, regarding clearance on fan. Early on I had marked approx location of where I thought the formers should be, based on wing spars, and gear. Seems I should have between 4.75" to 5" to work with. So that should give me at least 1/2 or more ea. top/bottom.
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Old Jun 10, 2014, 06:18 PM
efflux RC's Avatar
United States, CA, Santa Clarita
Joined Aug 2009
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Our Finnish, 6 ply (pictured below) was supplied by my laser cutter (RMS Laser - San Diego, CA)
Not sure where he sourced it.
You might try here, and call them to be sure. The Google listing reads "Finnish Plywood"
http://www.nationalbalsa.com/birch_p...p/181212bp.htm
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Old Jun 10, 2014, 07:07 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
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My LHS here in Hermantown, just on the outskirts of Duluth, carries all the wood from Bud Nosen. (or in my case, special orders my ply for me)
Makes it easy, Buds buisness is located in Two Habors, just up the north shore, about 30 mi from Duluth.

If I remember, I'll give them call in the AM, and see who they get theres from..
Ok took me a bit to dig this up, but the ply comes from here:
http://www.koskisen.com/
http://www.koskisen.com/contact

This is what is printed on the sheets I have used.
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