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  1. #1
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    Default Beth Canoe Sheer Clamps

    Hi All
    I'm starting to assemble the bits and pieces to build a Beth canoe. I have already spent lots of time studying a few other well documented builds on this forum, especially "Boreal," (thanks so much to all of you Beth builders who took the time to share!!!) and I'm hoping one of the other builders might help me with a little confusion I'm having as I study and compare plans, instructions, materials lists, and pictures.

    My plans materials list describes a pair of 16 foot 1" x 1/2" fir Gunwales, and a pair of 16 foot 3/4" x 3/4" Chine Logs.

    The building plans make frequent reference to Sheer Clamps. For awhile I was convinced that Sheer Clamps and Gunwales were being used interchangeably somehow, since there is no mention in the materials list of any Sheer Clamps, just Gunwales, which I always thought were like rubbing strips covering the outside seam where the deck meets the sides.

    Can anyone explain this to an amatuer? All the pictures I see and even the diagrams seem to indicate that the Sheer Clamps, which are on the inside and notched into all the bulkheads, are 3/4" square, just like the Chine Logs. How come they're not on the materials list? Am I crazy?
    Thanks All,
    Andrew

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  3. #2
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    See the piece being clamped to the frame heads? That's the clamp.



    Sometimes a shelf is also installed, in between the frame heads or outboard of the clamp, or on top of the clamp.



    Another sheer clamp, though it's really an inwale, as it backs up the planking directly. This is the way I do it in small craft, often with a continuous shelf on top of it, which can serve as a mini side deck too. I also typically screw or through bolt an outer rub rail to the shelf, making a "T" shaped edge along the sheer.


  4. #3
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    Thanks for the comment, PAR, you sort of confirmed what I thought: the piece in question is the sheer clamp, the problem is the specific dimensions of the piece don't seem to be described in the plans. I know the length should be 16' and the only pieces in the list aside from the chine pieces which are that length are termed "gunwales." The other builds I've seen documented in photos lead me to believe the sheer clamps are 3/4" square, not the 1"x1/2" given for gunwales. I'm likely going to just go ahead and follow this theory, but I'm looking for a little confirmation from other Beth builders, or the designer.

  5. #4
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    I am only a novice & never built anything, but aren't the sheer clamps the actual clamps you use to hold the gunwhales/inwales in place while you glue it all together?
    In the pictures the first one is using what I call G clamps & the second picture shows spring clamps.
    That is why they are not mentioned in the materials list, they are tools used in the construction.

  6. #5
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    Nope, a sheer clamp is an actual boat part, as shown in the drawing. Again, it can be arranged several ways, but they all serve the same purpose in the structure. You will need some wood workers clamps to attach a sheer clamp and most of use has a huge assortment to choose from in this regard. I have literally hundreds of clamps, of every shape and size, often having used most of them, to hold a sheer clamp in place, as I attach it to the hull structure. A quick Google search will reveal many different types of sheer clamp setups, employed by different designers.

  7. #6
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    Thanks PAR, for all the clarification. Obviously the terminology is confusing at times. I learned about sheer clamps from a kayak building forum at CLC, although the kayak I built was so light I only had to glue and tape the deck to the side. For the uninitiated, the "Sheer Clamp" is a structural piece running along the top edge of the boat's sides -the sheer line- providing stiffness and a fastening surface for joining the sides and the deck.

    My problem here is that, in spite of knowing Beth requires sheer clamps, and seeing them photographed in other builds, I don't see specifics on the timber list describing their dimensions. I don't think the gunwales that are listed are sheer clamps: I believe the gunwales run along the outside of the boat and cover and protect the seam between the deck and the sides.

    I've been hoping Boatmik would jump in here.

    So my tentative solution -and I'll put this to you PAR as a question from a builder to a designer/builder- will be to presume that, since Beth is a "box boat" with no flare and little to no overhangs, I should just make a set of pieces the same dimensions as my chine logs and use those as sheer clamps. Does this sound workable?

  8. #7
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    I don't want to hazard a guess at Miks scantlings for Beth, but it doesn't seem to be a very big piece, from the photos I've seen. I would think a 20x40 would be likely too large, but close. If a Beth builder or Mik doesn't drop in, have a look at a few dozen Beth builds and scale the clamp from the photos. Not the best way to do things, but you'll get close enough.

  9. #8
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    Quote Originally Posted by alrotch View Post
    .........since Beth is a "box boat" with no flare and little to no overhangs, I should just make a set of pieces the same dimensions as my chine logs and use those as sheer clamps. Does this sound workable?
    My 2c: if Mik doesn't say otherwise before you need to put them in, I'd go with that.

  10. #9
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    I'm not sure where Mik is, but he's been away for about a month. You may try shooting him an IM or email.

  11. #10
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    Begging pardon all: the sheer clamp dimensions not on the materials list, but I ran across them tonight right in the plans. While I'm glad to learn that I guessed them properly, I feel silly for wasting y'alls time. Thanks for the suport though!

  12. #11
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    Now you have me curious, what are the molded and sided dimensions for the clamps? I'll guess 16x35 mm.

    Lastly, you don't get what you don't ask for . . . even if you didn't need it after all . . .

  13. #12
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    Hi PAR,
    I'm a little unfamiliar with the terms molded and sided, but this should answer your question: the sheer clamps are 19mm square, but when fitting they are supposed to stick up 5mm above the top of the side plank so that their inboard edges are high enough to follow the deck camber. The outboard edges are to be planed down flush the side planks.
    -Andrew

  14. #13
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    I noticed the same thing building Boreal: the sheer clamps aren't in the material list. Like you, I went with 19mm square and it seemed to work out well. How's your build coming along?

    -Andrew (great name, right?)

  15. #14
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    Quote Originally Posted by alrotch View Post
    Hi PAR,
    I'm a little unfamiliar with the terms molded and sided, but this should answer your question: the sheer clamps are 19mm square, but when fitting they are supposed to stick up 5mm above the top of the side plank so that their inboard edges are high enough to follow the deck camber. The outboard edges are to be planed down flush the side planks.
    -Andrew
    That's the way! Thanks Al!

    The deck clamps are square so they are molded and sided 19mm - really more to be a convenient size of timber to pick up from a timberyard and there is plenty of bonding area for the thin plywood. Could go smaller cross section but bonding area to ply on side and also ply on deck needs to be 12mm wide minimum.

    In a way the deckclamp and sheerclamp are combined in modern construction. Beth was the first design I did so might have some mistakes lurking ... I'll have to update the timber list. So yes ... inside the hull and will be 3/4 x 3/4 (19 x 19)

    The gunwale goes outside the hull - it will be visible on the outside and is that smaller 25 x 12 (1 x 1/2") size. It also it fitted a little proud of the deck plywood and then planed down to match the angle.

    So not builders going mad... The designer being mad! Sorry about that.

    MIK

  16. #15
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    Thanks Mik! I don't know if it made any difference that I downloaded the PDF plans from duck works, except that I might not have combed through them as thoroughly as I might have if they were on paper. I sort of like the PDF in that I can print just the pages I want, which I find resource-friendly.

    If you go to make changes, I thought I should mention there's a slight discrepancy between the plywood layout diagram and the timber lists: on the diagram the bottom is specified at 6 rather than 9mm, which I figured must have been the result of momentary upsidedownism.

    Progress on my Beth build has been almost nonexistent since I had to promise no boatbuilding until some fiscal issues were solved -in order to preserve domestic tranquility. However I've had time to accumulate a couple of old routers and other handy used equipment, and I should be picking up the plywood in just a few days. Also in the meantime, I've been toying with the idea of stripping the deck in red and white cedar...because I'be never done that before and I'm a masochist. On the other hand wouldn't a Beth with a stripped deck look nice?

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