"finishing" fibreglass tubes

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Gillard

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Linking from my previous post on fibreglass weight.

Now that i have a tube that has been glassed with and overlap on the cloth. I want to have the tube to be smooth. What do you guys do to do this.

I am thinking about using a polystyrene filler to fill in the weave and then sand it down smooth, keeping the glass cloth intact. The filler will be the car body filler type that i have used before, easy to work with, easy to sand, relatively cheap. The only downside that i can see apart from time, is that the filler will be quite heavy but no heavier than say quantum tubing.

The other option is to apply a top layer of epoxy with micro balloons mixed in, i am not overly keen on this idea, as it will be harder to finish to a smooth coat.

What's everyone opinions, what do you do, and please feel free to chip in with the same idea as someone who has posted before so i can judge what is most common etc.

thanks in advance.

Gillard
 

kandsrockets

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I use a 2 part high build primer. This requires a paint gun to be sprayed and a good resperator. I spray it on and sand it smooth and I am done.
 

troj

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It depends on the weight of the top layer of cloth. If you do a "finish layer" of a fine weave cloth, then a high-build primer works well. Otherwise, you want to use a filler.

Polyester-based body fillers work, but aren't the ideal (though they're what I use, most of the time). A better choice would be Aeropoxy's lightweight filler or Poly-Fil. In the case of either one, be sure you get it from someone who moves a fair amount of product -- like a LOT of epoxy products, it has a shelf life, and you don't want something that's been sitting on the shelf for a long time.

I learned that one of the hard way -- my first Poly-Fil was past its shelf life and unusable when I got it.

-Kevin
 

kandsrockets

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It depends on the weight of the top layer of cloth. If you do a "finish layer" of a fine weave cloth, then a high-build primer works well. Otherwise, you want to use a filler.
The Automotive 2 part hi build primer (not the rattle can junk) can be sprayed up to an 1/8" thick and will not shrink. I have used this on 10oz glass that has a large weave and the paint has not come off yet and it is over a year since it was painted. This is on a R/C 1/4 scale Miss Budwieser boat I did for my brother.
 

JimJarvis50

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One option you might consider is to use peel ply to get a smooth surface. This page ...

https://www.rocketryplanet.com/content/view/3049/38/1/3/

... shows how I use peel ply on new tubes to get a smooth surface. It would be better if you had used this approach when you initially applied the fiberglass, but I think it will still work for you now. Assuming that your fiberglass job isn't too rough, you should be able to paint the tube with epoxy and then apply the peel ply and wet it out as shown. Then, after you remove the peel ply, you should paint it twice with epoxy and then sand it down smooth. I get peel ply at AVT composites, but smooth nylon cloth from the fabric store works too.

The peel ply will give you the minimum thickness of epoxy needed to fill your weave and leave a smooth surface. I believe you will find this easier than using a filler material.

Jim
 
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Gillard

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thanks for the replys so far, i had a look at the peel ply method - that link was very informative, thanks. looks like alot of work, but does produce a good tube. probably favouring the fillers at the moment.
 

rocketsmith

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I often use West Systems 410 Fairing Filler and some Microballons. The fairing filler makes the topcoat easier to sand. Mix the fillers and epoxy until the consitency is like soft peanut butter. Use a piece of acetate sheeting to make a spreader and apply a thin layer just thick enough to fill the weave. I will then sometimes use a heat gun on the low setting to quickly heat the finish coat enough to get it to flow out. After the top coat cures, sand with a dual action sander; It should only take a few minutes to knock down any high points and get an even hazy finish. I then fill any minor imperfections with automotive spot putty. Sand and prime as usual.
 
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