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Thread: Grumman Leaboard attachment

  1. #1

    Default Grumman Leaboard attachment

    I am down in Devon tinkering with my Grumman, I know someone in the OCSG has a Grumann with the leeboard bolted through the hull. I think they were at the Coniston meet,but I can't remember who they were. Have you got a close up of how that was achieved? I want to dispense with my S-D leeboard thwart to make the set up simpler.

  2. #2
    Join Date
    Dec 2006
    south Cumbria


    Jeremy and Pauline have a Grumman and were at Coniston. I'm not sure how you see it fixing to the canoe without a thwart - so as to share the rather significant load across the canoe.

  3. #3


    Does their Grumman have a leeboard thwart? I'm sure I've seen one with the leeboard bolted through the hull , maybe it was on a photo somewhere To be honest I didn't look at the Grumman at Coniston too closely.
    Last edited by unk tantor; 27th-November-2011 at 07:13 PM.

  4. #4
    Join Date
    Nov 2010
    grange over sands, cumbria


    I have fitted a few canoes with leeboards, but without a thwart. This is usually done by building in a very strong rib down the inside of the canoe with a block on the outside to take the pivot bolt. The rib really does have to be strong though and as long as possible, and well bonded to the skin of the canoe, from the gunwale to the bilge. As a word of warning i have also seen this method fail which resulted in the side of the canoe cracking. If i remember rightly, your Curlew has a fibreglass rib bonded down the inside of the canoe with a fitted wooden block on the outside. The trouble with aluminium is that you cannot bond well to it so a rib will have to be bolted in, and then all the strain will come on the bolt heads, which may pull through the thin skin of the hull. The leeboard thwart is a more reliable way of taking the loads, although this does take up some useful space in the canoe.

  5. #5


    Mmm, I was thinking of some sort of shaped wooden block on the outside of the canoe to give a vertical edge for the leaboard to bolt against and something similar on the inside for that to bolt onto, but with what Keith and Dave say its now obvious that would just put the shearing forces on the hull skin to the edges of the block, even if that method avoided pulling the bolts through the hull. My previous attempt at securing the thwart used a single coach bolt through the thwart onto wooden clamps the gripped the underneath of the gunnels

    but the thwart tended to slip.Mind you it had the combined forces of the downhaul the halyard and the sheet bridle put upon it. I am most likely to sail it with the bermuda rig in the future so maybe it won't be an issue.What might still be a pain though is the big rooster tail the leaboard put up which found its way over the gunnel
    Last edited by unk tantor; 28th-November-2011 at 01:51 PM.

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