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Stonefly thwart question


tomstaplez

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Tom:

The right place for your yoke is at the center of gravity (CG). So, as Jeff suggests, pick up the boat upside down and see where it balances. If you will be stowing paddles and other gear in the boat as your portage, lash those in place when determining the CG. If the place you determine is clear of thwarts and not otherwise in the way, you can permanently attach the yoke there, as is done on many canoes. If the yoke would be in the way, rig up a removable yoke as is standard on Adirondack guide boats. Guide boats have wood cleats on both sides with U-shaped slots where the ends of the yoke fit. See the attached photo as an example.

Fair winds, Andy

guideboat yoke.jpg

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That is a good question.  I have sat here thinking this through and my best answer is yes ... possibly... I am not sure. 

 

If there was  center thwart any others would likely be in tension since the gunwales would want to spread out.  The center would be in compression.

If you just have two thwarts toward the ends as I do in mine, I think they would be in tension..... But when you start to take into consider the gunwales being  attached to the frames  and how the ends are mounted it gets really confusing as to what is going on exactly. 

 

Pretty sure two thwarts would be stronger, it would be more rigid but the gunwales are very strong one glued up.  

 

As for locations I just walked out and looked at mine and because the seat is so close to center on this boat I think that two thwarts will work better. And I think your yoke is probably going to be in the way of the seat, so you will probably want it removable.

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As far as thwarts in tension or compression, the answer is yes. A boat is subject to dynamic forces as it moves thru and over the water.  For example, as waves lift the ends of a boat with a center thwart, that thwart is in tension. As waves lift the center of a boat and try to hog it, that thwart is in compression.  You can see that effect by taking a piece of paper and folding the ends to make a little paper canoe. As you move the ends in and out, the "rails" move in and out.

 

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