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Carbon Fiber Mast Part 1

How to build a carbon fiber spar:

This file is an excerpt of our building notes. The complete building notes are much more detailed.

In this file, we will first look at the building of the profile, the tube, then we'll look at details like local reinforcements and examine how fittings are made and added. Important remark: the strength of those spars greatly depends on the quality of the lamination work. The making of a carbon fiber mast is NOT a beginners job however, after building a composite boat hull, one should have acquired sufficient skills to make a mast. The most important point is to build a laminate with the highest possible fiber content. We explain how to obtain that result with simple procedures like wrapping the wet laminate in peel ply fabric. If you doubt your skills, add some layers.

The spar profile:

There are several good methods to build a carbon fiber spar profile: around a mandrel or in a mold. A mold is not required for a one-off mast.

We will review different ways to build a spar around a mandrel.

(See building notes for complete text)

We will consider two types of mandrels: an insulation foam type suitable for small spars and a rigid foam type for larger ones. Each method uses our carbon fiber and biaxial glass sleeves laminated in epoxy.

1. Carbon fiber spar laminated on an insulation foam mandrel.

This method is suitable for spars of constant section to make masts for small-unstayed spars for boats up to 16' or booms and poles. It is possible to taper the foam mandrel if one wants a tapered mast. Some of the pictures and text are taken from a web page created by one of our builders. Lazlo Morocz:

(See building notes for complete text)

The lamination stack is made of . . .

Some reinforcements are added where local loads are expected. In the case of a mast, at the mast step, masthead, boom fitting, shrouds tangs etc. We will describe them in detail later. The foam runs on steel pipe longer than the mast and supported at both ends.

If your tube bends in the middle like this:

You can straighten the mast by using weights at the ends:

This is sufficient for small spars, for longer ones we use a different method with a rigid foam mandrel on a bench. We describe that method later.

The insulation foam tubes . . .
(See building notes for complete text)
If you want a tapered mast, cut a slit in the upper part of the foam.

Local reinforcements:

We will add extra layer of glass in some critical places. To avoid the extra thickness, compress the foam with packing tape to make room for the reinforcements. (See building notes for complete text)

Build up the thickness with glass tape until you obtain a constant diameter. You can taper the reinforcement layers if you prefer.

Install the first layer:
(See building notes for complete text)

Pull the sleeve as tight as possible:

And apply resin

Once the glass is wet, try to squeeze out as much resin as possible but without starving the fiber for resin. A pass with gloves all around the spar is sufficient.

(This picture shows a solid foam mandrel but the resin "squeezing" technique is identical) Rotate the tube a few times during the cure to avoid drips. Let cure overnight.

This is how it should look when cured.
Fully transparent glass and visible weave indicate a good inner lamination layer with no excess epoxy.

Now we have a good solid tube around which we will proceed with the carbon fiber.

If you did not find the answer to your question, please use our message board and we will respond within a few hours.
Or explore the HowTo files at our technical support web site

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