Latest News: Forums Technical Mk I Centreboard Replacement

Viewing 6 posts - 1 through 6 (of 6 total)
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  • #19843
    Viper426
    Participant

    Greetings fellow W sailors!

    I’m the proud new owner of 3948 from Abbott and have spent the entire winter bringing her back “up to snuff”. The only major task left (fingers crossed) is replacing the CB which is damaged to the point of no return.

    I’ve read dozens of articles on creating one from wood, but I’m really hoping to replace it with GRP. The wall I’m facing is that I’ve no idea if I need a 19mm or a 21mm to properly fit.

    The existing board is warped to the point that I’d never get a proper reading, and since the difference is only 2mm I can’t think of a reliable way to measure the inside of the case.

    I know that later models were all 21mm, but I’m hoping that someone out there knows the width of the boards from the good old days.

    Cheers, and thanks in advance for any help!

    #19844
    john1162
    Participant

    Wooden boats usually have a 19 mm centreboard. Is yours a GRP boat? If it is by  Abbot is it from across the big pond? I would have thought the top of your centreboard by the handle would give you sufficient wood to measure the width with a pair of callipers?

    #19847
    Viper426
    Participant

    Sorry, I should have clarified. Yes, it’s a GRP boat and yes it’s from Sudbury, Ontario just down the road. (Sadly, Abbott burned down along with their moulds – now their website points only to the abyss.)

    I’ve taken measurements of the CB handle and the top-side opening of the case, but I can’t get anything reliable. The layers of the CB have completely separated (apparently the boat had sat in the cradle for 3 some-odd years without TLC) so my readings range anywhere from 23mm-29mm, but that includes a fair bit of gap which varies from point to point.

    As for the case itself, I think I’m looking at 21mm (measuring purely the width of the gap from which the handle protrudes), but I’ve not read anywhere that this is indeed the narrowest point and thus the point at which I should be doing my measuring. Again, since the difference between the two options is so small I’m having a lot of trouble getting a “certain” answer using only callipers. All it takes is a tiny warp from the age of the GRP to take me up or down 2-3mm as I measure.

    #19855
    Dave Barker
    Keymaster

    Could you make a fairly ‘quick and dirty’ trial board, or even just a straight plank of wood to test the fit in the case? Do you have access to a thickness planer?

    #19861
    rszemeti
    Participant

    I have just made a new board for my old GRP boat, the original was wooden, and 19mm in thickness. the old one had de-laminated and could be flexed around 12″ at the tip with moderate hand pressure.

    I cut the replacement from 19mm WBP Finish Birch, which I know from experience will last well outdoors. I simply layed the old board on the sheet and drew around it (accurately) with a sharp pencil. It’s not a true “marine ply” but as it is only going to get an occasional soaking as the boat is on a trailer, not moored, I doubt it makes any difference.

    Ply is easy to work with, and Finnish Birch has around 13 laminations on a 19mm thickness. A circular saw, plane and an angle grinder with a 120 grit sanding pad will allow you to shape the board quickly. Mine was done in a less than an hour. You can easily see the contours, so profiling is easy.

    I finished it in a couple of layers of epoxy and some white ‘International TopLac’  looks perfect, and is significantly stiffer than the one that came out.

    If you are just cruising, rather than racing, it’s a quick and simple thing to do.

    #19887
    Viper426
    Participant

    Thanks for the great idea, Dave! A few minutes with a planer and I’ve confirmed that the total gap is 20mm, so I’ve ordered a 19mm CL16 (GRP) CB.

    Thanks to everyone for their input and ideas!

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