Fiberglass mast repair?

[LimeyInBr]

I just took over an unfinished 28’ plyglass sailboat project. Problem is that everything here in Brazil is really expensve and the more I can do myself the better. I already got a bunch of good tips reading through back posts of this great forum. Thanks guys!

Present problem is this:
The mast is 34’ and I have an unused 24’ aluminum mast (section 7”x5”, thickness 3mm) complete with boom and spreaders, which I really want to use. Trouble is I can’t find the same section to join so I’m thinking of constructing the missing top 10’ in fiberglass.

I thought about making a permanent internal mould, either with foam, or plastic drain pipes, laying up epoxy/glass on the outside of this (spiral wound and longitudinal), and then gluing the new section to the old with epoxy.

I've atached a photo of the existing mast and a sketch of what I imagine the join should look like. Main problems I foresee are calculating the thickness of the new section and length of the internal sleeve, and matching the internal slider tube so the plugs don’t snag - maybe I’ll just ignore it and fit a new external track to the whole mast after.

I’ve already found plenty of info about constructing freestanding and carbon fibre masts on the web but nothing on plain old glassfibre or joining mast sections.

Anybody have any experience with this or know of any sites with info?

Thanks in advance for any help.

[Eric Sponberg]

A fiberglass mast section as an extension of an aluminum mast section is not going to work very well. Fiberglass is as bendy as spaghetti when compared to aluminum, and you'll have a really hard time keeping the fiberglass part of the mast straight.

In my opinion, you would almost be better off with making the upper section out of wood-epoxy. It could fit internally to the aluminum section and shaped so that the exterior surfaces are flush. You can start with a generous wall thickness, minimum 20% of the diameters all around, and plane it down to shape in pretty quick order, so you would not need any tooling of any sort.

I hope that helps.

Eric

[LimeyInBr]

Thanks, Eric.
I've seen a few smaller sailboat projects with instructions on how to make a wood-epoxy mast. Basically epoxying strips of wood together to get the basic profile and then hand finishing. Would a final layer of glass help hold it all together or is that unecessary?
Dan

[Eric Sponberg]

A final layer of fiberglass cloth all around would be fine, yes, mostly to seal the finish layer of resin and to toughen the surface against minor impacts from the sails.

Eric