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September 3rd

How To Make A Fiberglass Tube, The Hard Way

Posted by // September 3, 2013 // COMMENT (3 Comments)

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Precision Engineering

Fiberglass tubes. Wow, think of all the uses. You can hold things up, or store stuff, or brace something, or just put a fishing pole in it. The tube my father and I were trying to make has an ID the same diameter as a 2″ aluminum pipe and is about three feet long. I would like to tell you what I’m going to use it for, but I can’t do that yet.

Of course you can buy fiberglass tubes, which I suppose is what most people would do. But why buy it when you can make it. Should be easy, right? Ha.

My first attempt at this was way back in Marathon, Florida, and it was a total disaster. It was hot and I put too much hardener in the polyester resin so everything started to set when I was only halfway done and I ended up with some poorly-bundled fiberglass bonded solidly onto my aluminum pipe.

Lesson 1: Go easy on the hardener, and don’t try to do this in direct sunlight on a 95-degree day.

The second attempt was a bit more thought out. I had learned the first time that the fiberglass tube can be hard to remove from the pipe so this time we took extra precautions. We started by wrapping the pipe with thick paper, allowing a little bit of a gap to keep things loose. Then we wrapped the paper in plastic wrap.

With our pole all trussed up we started laying on fiberglass:

It helped to start by coating the pole with resin so that the cloth will stick.
I found it easiest to support the pole at both ends and spin it in place, wrapping the cloth around
I painted on resin with a brush as I went. It’s a little tricky to keep from over-saturating the cloth. The goal is transparency without getting drippy.
At first I was smoothing the cloth by hand but later found it more effective to just use the brush.
The last wrap

We put a few wraps of cloth around our tube and then let it gel up. If you get the resin at just the right gel time there is a point where the cloth will hold its shape but can still be cut with a utility knife. This is when I trimmed the imperfections and cut the ragged ends off of the tube.

This is also a good time to spin the tube around a bit on the pipe to make sure that it will still be able to come off. It spun ok so we let it harden and slid it off. Everything worked just fine, except that we had made the tube too big, and our pipe was a loose fit.

Lesson Two: You’ve got to be careful about getting just the right amount of slop in your fitting…

Back to the glass. Our next attempt was done in the same manner but this time we wrapped the paper tightly around the tube. When it came time to pull it off, it was stuck on quite solidly. I ended up having to cut it off with a utility knife:

Lesson Three: Don’t squeeze down on the cloth too hard when you roll it on the tube.

We decided to use it anyway. Our strategy all along was to start with just a few layers to make a sort of form and then to add the majority of the fiberglass around that. Even after cutting it off this bit of tube kept its shape so we put it back on the pipe and glassed over it with more layers.

We were running low on thin fiberglass so we used some heavy bi-axial cloth that I had around. I was worried about properly wetting out the cloth as we rolled it so I started by rolling resin on the whole piece.

I rolled it up and then checked that it would still rotate on the pipe. All seemed well. Then I got distracted and didn’t check again until it was cured. This was a very bad idea. Our tube was, again, totally bonded onto the pipe, and it was three times as thick as the last one.

Lesson Three: Don’t wander off when the job is half finished.

We tried twisting it. We tried banging the pipe on the ground. We tried WD-40. We even tried filling the pipe with ice in an attempt to shrink it.

Nothing worked. Eventually we got so frustrated that we gave up and went back to the drawing board. I did a little research and found out that our problem was that fiberglass actually shrinks when it cures. Ok, technically the resin shrinks and the fiberglass does not, but in this case the end result was the same. Epoxy, apparently, works better for this sort of thing because it shrinks a lot less. But it’s three times the cost.

Lesson Four: Curing fiberglass shrinks!

But knowing that didn’t solve our problem. What did was re-examining our original tube and deciding that it would actually work just fine. We went back over it with a few more layers and ended up with a very strong fiberglass tube, just right for our purposes:

All we had left to do was to remove our big mistake from the pipe. That proved to be quite a chore!

This article was syndicated from Safe At Harbour But Meant For The Sea: DIY Sailing with Paul Calder

3 Responses to “How To Make A Fiberglass Tube, The Hard Way”

  1. Ian says:

    I remember reading about the Gossamer Condor, a human powered plane build in the 1970′s. They needed carbon fiber tubes, so they wound an aluminum tube with the carbon and cured it. They then used pool chemicals to dissolve the aluminum leaving the just the carbon tube.

    another idea.

  2. Colin says:

    Use wax or mold release on mold

  3. Hank says:

    I ran across an article discussing making a carbon fiber or fiberglass mast on the UK Cherub site. I haven’t tried this – but it sounds reasonable….

    “One method that has had some sucsess is to cover the mandrel in candle wax this is melted in a pot and brushed onto the mandrel, and smmothed with a low temperature iron. When the time comes to get the mast off you can heat the mandrel by blowing steam through it a walpaper stripper is a handy tool. Once the wax is soft the mast should slip of eaisily.”

    http://www.uk-cherub.org/doku.php/tech/masts

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