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I need help on building a Full elmers foam board 50in wingspan airplane.

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I need help on building a Full elmers foam board 50in wingspan airplane.

Old 11-25-2007, 10:27 PM
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GreenAce92
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Question I need help on building a Full elmers foam board 50in wingspan airplane.

Alright well i have been experimenting with 3 different planes my SDM, Parkzone j3 cub and a Spruce Goose i built. The SDM is having problems with not producing enough lift(part of the problem was the battery.) the J3 just couldnot keep the stuff up in the air plus my J3 body wings tail and rudder was pretty much destroyed anyways so i got that to fly then it crahsed into the woods at about 30mph which it didnt even get stuck into the trees it just ripped through the branches, and then my Spruce Goose was not doing to hot either it just kept having wingtip stalls i think so it did not fly well either. I got a PDF plans for a J3 cub from Rc Groups and you are suppose to use foam like 6mm foam so usually you would use fan fold because its bendable and durable but for 50bucks its not an option for me right now im kinda broke. But i can get 2 black elmers foam boards and build some plane out of that the problem now is is that the planes electronics weigh around 16oz so the plane and electronics will probably weigh around 18oz. I need help to build a 5ft wingspan probably to suport my electronics heavy weight and mostly the underpowered motor. I cant buy any new electronics till christmas so i have to work with this stuff. I need tips on strengthening the body and wings so that if i crash the foam doesnt disenegrate on the ground plus i have to make it roomy while beeing strong plus i have to have it have an airfoil probably an undercambered airfoil. The thrust off the motor is descent it produces like 1/3 of the weight of the plane maybe more i just am trying to build a floater.

Thanks.

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Old 11-25-2007, 10:42 PM
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FlyingMonkey
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Check the dollar stores near you.

I have been able to buy foam board there for a buck a sheet.

Why 5'? I made a 4' profile plane that runs off a small 400XT brushless, and is able to carry a 5 oz camera aloft.

The largest problem with such a large wing, is the spar.

My plane has a KF airfoil, which is just a folded piece of foam. It has a spruce stick, (square, like you would use for a motor mount). That's a little over kill, but it works.

The next big problem you'll likely encounter is the wing's length will make it difficult to transport. You can make it so that it will separate. I have had luck with this by using aluminum tubes. One with a OD the same size as the ID of another tube.
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Old 11-25-2007, 10:44 PM
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GreenAce92
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well maybe not 5ft but i need the wingloading to be at least 8oz/sqin so that it can float around. I guess 50in will work.
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Old 11-25-2007, 10:55 PM
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Take a look at this.

It floats, it's cheap, it's easy to build, easy to fly, and it's fun.

http://www.wattflyer.com/forums/showthread.php?t=26819
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Old 11-25-2007, 10:58 PM
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"the planes electronics weigh around 16oz so the plane and electronics will probably weigh around 18oz."

I think a plane with a 5' wingspan is going to weigh more than 2oz.

Just the spars and glue for the wing alone will weigh much more than 2oz.
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Old 11-25-2007, 11:06 PM
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I think your right when i measured the weight of the original stock electronics it weighed around 10oz and all together the body was 15oz so i guess a body will be at least 6oz. It will be around 50in sorry i forgot how big a 5ft wingspan airplane would be.
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Old 11-25-2007, 11:26 PM
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Ok ive decided not to go with the 50in wingspan and instead i will just increase the "hump" of the undercambered airfoil. the plans i got is from rc groups ill post it here. The wingspan of the plans are 38.4in so maybe that will be enough to suport the weight. The rootchord is descent so i will have to see also how can i bend the foam board? I dont want to snap it.

Thanks
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Old 11-25-2007, 11:29 PM
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Well i guess i cant upload the file because its 1.25mb PDF.
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