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View Full Version : Fibreglassing a spar made easier


WX
06-29-2009, 11:53 PM
http://giantleaprocketry.com/products_airframe_standard.asp#easyglas

The EASYGLAS SOCK is a stretchy sleeve that fits over your airframe to make fiberglassing a breeze. Traditional fiberglassing methods are tricky, and involve wrapping cloth around a tube. The downside of this old approach is that it's time consuming, really messy, frustrating and, worst of all, leaves an overlap ridge that has to be sanded down. In short, it's a royal pain! Finally there's an easy way to glass your tube - - with the EASYGLAS SOCK.
The EASYGLAS SOCK is not fiberglass, but is made of a material that readily absorbs resin and adds structural strength. We've tried it and it works beautifully. Best of all, it finishes easily. The EASYGLAS SOCK is about as thick as 3 or 4 oz fiberglass cloth. Here's the simple procedure:



Slide EASYGLAS SOCK over dry airframe and tie the loose ends with twist-ties.
Mix your resin, and apply thoroughly over the EASYGLAS SOCK. Squeegy excess material and rotate tube occasionally while resin cures.
Once cured, lightly cut down high spots with sandpaper, then prime with several coats of extra thick filler primer (available at department stores). Be sure to sand between coats of primer.

That's it!! Trim the ends and you're ready to paint!

andrewe
06-30-2009, 03:11 AM
Gosh! I always wondered how rockets were built. Can't understand how NASA spends so much money:D
A

mizzenman
06-30-2009, 04:07 AM
But would one want fibreglass on a spar? IIRC it has higher modulus of elasticy than wood.

WX
06-30-2009, 07:06 AM
Mizzenman, from what I have read it actually creates a stiffer spar as it takes the loading...I'm quoting someone that has done it, I'm not speaking from experience.

StevenBauer
06-30-2009, 07:54 AM
A stiffer spar subject to catastrophic failure and rot. Bad idea. Don't do it!


Steven

WX
06-30-2009, 07:59 AM
Hmm, well there's a well put argument in the negative.

JimConlin
06-30-2009, 08:32 AM
In a braided sleeve like that, the orientation of the fibers will end up considerably off-axis, maybe 45 degrees versus the length of the spar. In that orientation, they'd be effective at preventing the spar from twisting, but quite ineffective at stiffening the spar against bending.

kc8pql
06-30-2009, 10:11 AM
A stiffer spar subject to catastrophic failure and rot. Bad idea. Don't do it!

In a braided sleeve like that, the orientation of the fibers will end up considerably off-axis, maybe 45 degrees versus the length of the spar. In that orientation, they'd be effective at preventing the spar from twisting, but quite ineffective at stiffening the spar against bending. Agreed. Glassing a wooden spar is a bad idea.

paladin
06-30-2009, 10:56 AM
I have seen dozens of homemade fiberglass spars.....all of them so much heavier than a nice wooden one....and more prone to damage....In the early days of Piver/Norm Cross and other multihull designers I have also seen fiberglassed wood spars, with both polyester and epoxy, and none of them held up very long. A nice, well glued fir or spruce spar with good varnish and periodic resurfacing outlasts them all.

JimConlin
06-30-2009, 11:28 AM
I hesitate to make universal statements, but I haven't seen many good reasons to glass a conventional wood spar.

Spars that are designed as composite spars can work nicely, but that's a different topic.