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Building a Fiberglass Frame

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edwardw

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I am attaching a Rocksim file of a rocket I am currently designing/construction. Pay no attention to the internals.

I am trying to construct a fiberglass shell that would be the rocket 'body tube'. I don't know exactly how to go about it. Here is the current scheme. As for dimensions, it is 48" tall, 7" at the widest and a 2" motor mount.

Make two cardboard centering rings for the 7" part. Then every 2" or so make another ring the diameter of the parabolic curve. Then take 1/16 x 1/4 or 1/2 balsa strips and run them perpendicular to the centering rings. This would make a 'form' for the fiberglass. (Kind of like the shapes you see in an old diridgible (blimp)) Then run gummed kraft paper lengthwise on the 1/16 x 1/2 strips. This would for a paper skin. Next you glass the entire thing with probably 9 oz glass and then some 2oz glass. You let it set up and then take the cardboard and the 1/16 balsa strips out. The paper will probably be stuck to the glass so good it ain't coming out. Do this for both sections and integrate the fins into the process so you have a one piece fin can and one piece payload.

Any suggestions ideas?


Edward
 

sandman

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I'd scrap that idea and make the whole thing out of pink foam and turn it on a lathe...but that's me.

sandman
 

edwardw

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I never though of that :) That's why I love you all's advice! So just pink foam covered in fiberglass then? And pink foam as in foundation foam for construction? Why don't you all use the blue type? ( I build houses and usually use blue board on foundations) Is there a difference for rockets?

Edward
 

sandman

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edwardw,

Blue pink??? I guess it's just what my local contractors supply carries.

If you get the blue for free...use it...free is a good price for any hobby material!

The pink stuff comes 2" thick and is nice and tight (no little balls of foam to deal with).

sandman
 

edwardw

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The blue board is I bet the same stuff - it isn't styrofoam, I think they call it closed cell foam. I do know that some adhesives melt it. I will try it. I looked at the links - do you leave the foam on the inside permanently and just cut out what you need? We were thinking of just a fiberglass shell...

Edward
 

DPatell

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I imagine the blue board will work. Turn up your design, put a few layers of glass on it. Acetone will melt the foam, so buy a can of acetone and start pouring it on the foam from an exposed end. Do this outside, I imagine the gasses created can't be too good for you...

Be careful when you start to melt near the fiberglass, as the acetone will actually return to epoxy to it's liquid state to a certain degree, weakening the structure. I suggest pouring down the middle, leaving an inch or so of material around the outside, then just cutting it out.
 

n3tjm

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One thing I would be concerned abot is fin shear... those are very big fins, and aerodynamic forces will try, and most likely will, rip them off...
 

edwardw

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The fin design is still up in the air - but we are going to make them 1/4" G10 and then glass them into the frame also. I will have to look at my epoxy guide (I use West System) and see if SLX Denatured Alcohol will thin it. I know that it will eat away the foam I use really nicely :)
 
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