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Old Apr 16, 2014, 10:52 AM
Hobby King Hater
Kimber's Avatar
USA
Joined Mar 2005
4,558 Posts
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Balsa to foam build???

I don't want to read over a thousand pages to find something and a search didn't
give me any thing useful. so......

I have plans for a 48" Jenny. Done in balsa. Since it is a simple design, I was thinking
of doing it in foam. Cut out all the parts, lighten the internals. leave a section of
paper on the edges for gluing. Doing a one piece folded wing section with
a foam spar reinforced with light ply. Use poster board for the sheeted parts.

Remove the paper on the inside parts. And on the inside of the fuselage sides
and wing.

Thinking maybe a three to three and a half pound plane? 10 size motor on 3s.
9g servos.

http://www.headsuphobby.com/Firepowe...otor-E-675.htm
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Old Apr 16, 2014, 11:00 AM
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IAFoamie's Avatar
Joined May 2012
152 Posts
Here's a bit smaller made out of foam might help you.
http://www.wattflyer.com/forums/showthread.php?t=50906
IAFoamie
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Old Apr 16, 2014, 11:54 AM
Hobby King Hater
Kimber's Avatar
USA
Joined Mar 2005
4,558 Posts
Quote:
Originally Posted by IAFoamie View Post
Here's a bit smaller made out of foam might help you.
http://www.wattflyer.com/forums/showthread.php?t=50906
IAFoamie
Thanks, that is just what we want to do, but larger. Maybe a bit of added chord
to the wing. Even want yellow...

Going to get an ink cartridge for the old printer and go for it.
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Old Apr 17, 2014, 05:14 AM
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United States, OH, Westlake
Joined Mar 2002
4,528 Posts
That was a nice build on Wattflyer. I missed a Jenny foamie on the classifieds a few weeks ago and regret it a bit.
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Old Apr 17, 2014, 06:27 PM
Marty Petri Sr.
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Thailand, Uttaradit, Bo Thong
Joined Jun 2007
766 Posts
Nice Project.
Here are 2 threads that may be of help to you, a different plane, but his build techniques are worth the read.
Sprung Undercarriage for Tail Dragger
Tiger Moth

Marty
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Old Apr 17, 2014, 09:39 PM
Hobby King Hater
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USA
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Thanks
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Old Apr 17, 2014, 09:55 PM
treefinder
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SE MI
Joined Oct 2004
9,747 Posts
Just as you recently discovered with your ft plane, when using foam, you don't really need all the structure as with traditional balsa builds. The thick skin carries a lot more loads better than monocote. So you could do a decent Jenny just by using a 3 view.(boxy fuse, simple wing airfoils). Cutting out all the bits from a balsa plan can certainly be done, but will make a heavy, complicated tougher to repair plane. A typical build 48" foamie should weigh a lot less than 3.5 lbs and fly well (lighter fly's better!) My 30" span OneSheetBipe comes in at less than 10 oz ready to fly, and the 56" span superTwin is probably only 20 oz or so (have to measure it)

It is a different paradigm and opens up a whole new arena to play in.
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Old Apr 18, 2014, 12:57 AM
Hobby King Hater
Kimber's Avatar
USA
Joined Mar 2005
4,558 Posts
The plan is to lighten the inter structure as much as possible. Just there to give it the right
shape.

This is a bit crude, but you get the idea. Of course there won't be any strings, that part will
be covered with poster board.

This may be a learning model, and never flown, we will see as we go. Haven't printed
the plans and patterns yet.

Thanks for the info.
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Old Apr 18, 2014, 08:39 AM
treefinder
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Joined Oct 2004
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Good plan! My comments were coming from your mention of "cutting out all the parts", which made me think about all the myriad of parts that are typically in a balsa build attempting to get a strong structure. Combining many of them and eliminating others is the way. I generally use a full former only where something is happening in the structure, like nose/firewall, wing LE and TE, and at a fuse section change. The typical early bipes with box fuse had a straight cross section from nose to aft of cockpit, then plan view (and side view) taper, so I put a former at that transition point, and skipped any formers aft of that, relying on the foam thickness to provide the section strength.
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