internal mast sleeve

  • 05 Mar 2018 10:08
    Reply # 5889441 on 5888698

    I think I would find it very difficult to make glass/epoxy bands fit well enough, whereas, the poured polyurethane (not polyester) method is relatively easy, and automatically ensures a good fit. The polyurethane tooling formulations such as Smooth-On (PMC 770, 780, 790) have very low viscosity, pour like water and will not leave any voids. 

    The only tricky part is in setting up and sealing the places where the compound might leak out, as the stuff is so fluid.

  • 04 Mar 2018 21:20
    Message # 5888698

    I wasn't uncomfortable with some mast flex that I see on my 19 ft Com-pac but late last summer the amount of movement while motoring with bare pole in a steep chop caught my attention. For piece of mind and mast longevity I just ordered an 8 foot section of aluminum tube to use as an internal sleeve to stiffen the mast. The mast is hybrid, 4.5in x .125in (114mm x 3.2mm), 6061 t6, 23ft above the partners, 26 ft OA. A 4.25in x .125in tube that would have given a snug fit is not available so I will work with a 4in one that will leave a .125in (3.2mm) space all around.

    I'm considering two ways to deal with the gap. I'm thinking that snug fiberglass tape and epoxy bands at heel, partners and top, with maybe one in between top and partners would give me the added stiffness and strength I'm looking for. The other way would be, as David Tyler described to Jami last September, Reply # 5090709 on 5070195, filling the gap with polyester modeling resin through a drilled hole. That would pretty well join the sleeve and mast into a single unit. However, I don't know about the viscosity of the filler or the possibility of something going wrong with the pour, trapped air spaces or spotty filling in that long thin space. It would give, I think, more strength than bands but I don't know if there would be much of an advantage in stiffness.

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