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Thread: Leeboard Thwart help

  1. #1
    Join Date
    Mar 2011
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    Sarasota, Florida USA
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    Default Leeboard Thwart help

    I am assembling my sail rig. I was given two grumman leeboards. Not deep enough for single use so I'll use both. I'm in a time crunch so will need to order parts quickly or keep it local. I plan to use a 1x4 for the thwart. I can't find suitable aluminum angle locally. Can you use wood blocks to run a bolt through for attachment of the leeboards? Is 1/2" bolt customary? Can I use wingnuts for tension or should I look for the lever that's threaded for tensioning? Any self-built leeboard ideas entertained!!!

  2. #2
    Join Date
    Aug 2010
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    Exmouth, Devon, England
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    I'd really like to see and read more about your build.

  3. #3
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    Nov 2010
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    grange over sands, cumbria
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    We use 10mm bolts for our leeboards so 1/2inch will be fine. You can make a wooden block to support the leeboard but make it strong, the force on a board can be quite large especially with a large sail in strong wind. If you stack up 2 (4inch long) layers of your 4 by 1 on top of the end of your thwart and embed the bolt in the middle layer that would probably be strong enough. A wing nut will be OK.

  4. #4
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    Mar 2011
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    Sarasota, Florida USA
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    Quote Originally Posted by DaveS View Post
    We use 10mm bolts for our leeboards so 1/2inch will be fine. You can make a wooden block to support the leeboard but make it strong, the force on a board can be quite large especially with a large sail in strong wind. If you stack up 2 (4inch long) layers of your 4 by 1 on top of the end of your thwart and embed the bolt in the middle layer that would probably be strong enough. A wing nut will be OK.
    Dave, Thanks again for your help. I wish we were on the same side of the pond! I love your equipment and you so freely offer advice. Can you describe what you use for your washer and locking handle to help me locate a supplier over here? Googling locking handle is not helping!

  5. #5
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    Nov 2010
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    grange over sands, cumbria
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    We make our own washers from 1/4inch aluminum plate as we haven't sourced anything suitable, but the locking handles we buy from RS.( http://uk.rs-online.com/web/p/clampi...evers/0478208/)
    You should be able to get something similar over there

  6. #6
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    Mar 2011
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    Sarasota, Florida USA
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    Quote Originally Posted by DaveS View Post
    We make our own washers from 1/4inch aluminum plate as we haven't sourced anything suitable, but the locking handles we buy from RS.( http://uk.rs-online.com/web/p/clampi...evers/0478208/)
    You should be able to get something similar over there
    Crap! I re-read a pm you sent me a while back. I ordered aluminum angle, but ordered 3" by 3" by 1/4".
    It is 6061-T6 with a radius root, structural. If it fails, I'll go to the 3/8" 3 1/2" x 3 1/2". Can you tell me the diameter of your 1/4" plate aluminum washers? Additionally, is there anything between the angle and the rear face of the leeboard, or is it aluminum on hardwood? Last question... do you utilize through bolts in the 4 corners of the leeboard thwart to hold the aluminum angle to it or wood screws? Last last question... your 1x4 thwart...is that nominal size, meaning 3/4" x 3 1/2"? That's the way they market wood here. I can source true 1x4 lumber if need be...

  7. #7
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    Mar 2011
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    Sarasota, Florida USA
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    Quote Originally Posted by bhofmann View Post
    I'd really like to see and read more about your build.
    Sorry for the belated reply. I will post some photos and description soon... I could use all the help I can get.

  8. #8
    Join Date
    Nov 2010
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    grange over sands, cumbria
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    It is worth trying the 1/4 inch angle to start with. It is only half as strong as the 3/8 inch but we have never bent or broke one of these so there may be some redundancy. The washer that we make is 2inch diameter although it could be smaller. We machine the thwarts out of 1 and 1/4inch stock so they can be 1inch thick but probably 7/8 inch is strong enough. The bracket must be bolted to the thwart, screws will definitely pull out if you sail upwind in a strong wind with a large sail. I glue a thin pad of wood 3 1/2 inch dia onto the back of the board and then surface it flat and parallel to the centreline of the board. This is easier than trying to leave a flat on the board where the pivot goes through whilst you profile the rest of the board. Using long plane strokes the full length of the board makes it easier to control the shape of the board as you try and make it the correct profile all along the board.

  9. #9
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    Mar 2011
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    Sarasota, Florida USA
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    Quote Originally Posted by DaveS View Post
    It is worth trying the 1/4 inch angle to start with. It is only half as strong as the 3/8 inch but we have never bent or broke one of these so there may be some redundancy. The washer that we make is 2inch diameter although it could be smaller. We machine the thwarts out of 1 and 1/4inch stock so they can be 1inch thick but probably 7/8 inch is strong enough. The bracket must be bolted to the thwart, screws will definitely pull out if you sail upwind in a strong wind with a large sail. I glue a thin pad of wood 3 1/2 inch dia onto the back of the board and then surface it flat and parallel to the centreline of the board. This is easier than trying to leave a flat on the board where the pivot goes through whilst you profile the rest of the board. Using long plane strokes the full length of the board makes it easier to control the shape of the board as you try and make it the correct profile all along the board.
    First off, thanks for your time and advice. What an invaluable resource you are to paddlers on that side of the pond! I'd definitely order the bits from you if shipping to florida weren't so expensive. You've helped me tremendously in producing my own gear. The sheer amount of experience you've amassed gives me confidence in your advice. You have definitely worked the kinks out over time.

    I leave on vacation in under a week, and sadly I was not able to complete my sail rig. However, it looks as if I'll be able to take my canoe, the Spring Creek rowing rig, and a 9 foot double paddle with me: http://store.springcreek.com/Rowing-...ges-p1520.html

    I also built a reproduction of an old town designed adjustable rowing seat now sold by Shaw and Tenney: http://www.shawandtenney.com/images/...g-rig-2-lg.jpg
    I'll shoot some snapshots of that later...

    At least I'll get more of a feel for my hull in open water, rowing and double paddling, while waiting for time to complete my sail rig...By the way Dave, I have a new level of respect for you knowing you hand plane your leeboards instead of using CNC equipment!!!

  10. #10
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    Nov 2010
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    grange over sands, cumbria
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    I cheat nowadays by taking most of the wood off with my planer thicknesser. I use a tilting table to plane bevels onto the the blank so i only have to fair them in with a hand plane.

  11. #11
    Join Date
    Mar 2011
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    Sarasota, Florida USA
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    Quote Originally Posted by DaveS View Post
    I cheat nowadays by taking most of the wood off with my planer thicknesser. I use a tilting table to plane bevels onto the the blank so i only have to fair them in with a hand plane.
    Just working smarter, not harder!! I'm working on finding a similar locking/clamping handle over here. From the picture, it appears there is a finite amount of space underneath the red release button. If so, one must choose an appropriate M10 bolt/washer combination to leave just the right amount of threads exposed where the bolt exits the leeboard, to allow clamping enough? If the bolt were too long I picture the bolt bottoming within the lever prior to applying appropriate tension...

  12. #12
    Join Date
    Dec 2006
    Location
    south Cumbria
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    1,205

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    If so, one must choose an appropriate M10 bolt/washer combination to leave just the right amount of threads exposed where the bolt exits the leeboard, to allow clamping enough? If the bolt were too long I picture the bolt bottoming within the lever prior to applying appropriate tension...
    Yes, that's right. The bolt can be trimmed to suit or extra washer(s) added.

    in the case of too little bolt length, as long as the threads in use are roughly similar or greater than the diameter of the bolt it will work fine.

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