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Coaming thigh bracing


bagarre

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Since I'm laminating my own coaming, I thought I'd add some thigh braces as well.

Here is a tracing of the stock coaming with the cheeks added. The lines are 2" apart for scale.

 

Since the coaming is 1 1/2 inches high, and I need to lace the fabric on, I can make the cheeks 1" thick at the coaming and taper them to 1/2" at the inside edge.

To make them more a part of the coaming, the inner most layer(s) of lamination will follow the cheeks as well. It will be a tight interior bend at the front so it will need to be thin.

 

In the middle of the drawing , you can see a sectional view of the coaming and cheek at it's widest part showing the spray skirt lip ( lower right side) and cheeks (lower left side) as they taper to the hoop in the middle.

 

Built from maple, I'm making the assumption that a 1.5"x.5" hoop is strong enough and the spray skirt woudl be .5"x.5" and the cheeks are 1"x.5" tapered.

The bottom of the cheeks will have .5" thick closed cell foam which will bring the whole thing flush to the bottom of the hoop.

 

Thoughts?

 

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My 10" band saw with the stock blade doesn't exactly resaw 1.5" maple very well.

Instead of waiting for a better blade, I decided to use the table saw. Lots of waste :(

But the boards are cut. The thick one (1/4") will be used in the cheek laminations since there are no real bends.

 

Tonight I cut the jigs and start glueing.

 

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I can't do anything by the book. These coamings are going to take as much time as the whole boat.

But, the jigs are done.

The idea is to build up the cheeks on the outer jigs and cut the curve that matches the main jig.

The cheeks will then be transferred to the main jig to continue the lamination.

 

IF this works out, I might have to do a full write up on it.

 

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I am still trying to figure out why you made such a complicated mold.  Maybe it will be more clear to me as this thread continues.  You have got me thinking though, that maybe an inside mold would clamp up better than the outside mold many of us have built and used over the years.

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I'm with you, Dave. I'm kind of confused, but I kind of get it.

However, the best part of this type of place is the perspective of everyone else. Our minds all work so differently, it's cool to see how other people work, because they sometimes do things in ways that change the game.

I was a big cheerleader from the start, so I'm extra invested, but this is a cool experiment.

Keep it up!:)

Peace,

Robert

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Not sure how to best explain my thought process on the moulds but, here goes:

 

I wanted the knee braces to follow the same lamination curve as the coaming but they are a different thickness than the coaming. The knee braces will be 1/2" on the inside edge and 1" on the outside edge. The 1" side is the part that laminates to the coaming. The coaming is 1 1/2" tall.

 

So, I needed to make moulds for the knee brace cheeks. I'll form the cheeks first and then they will fit into the main coaming mould to fill in the voids cut out.

That will make the main mould the same shape as the original coaming. Then I will laminate the coaming as normal with the cheeks attached.

 

The curve in the photo is the curve of the coaming. The other side will be cut to match the cheek cutouts on the main mould.

 

Hopefull, I will have better photos by tomorrow but I couldnt figure out how else to make the laminations match with the different thicknesses.

 

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Learning! :)

Just keep it up, you are doing a brilliant job. Of explaining, too. I'm right on board now. And, please, don't think I ever doubted you. As I said, the beauty is learning different ways of problem solving. You are innovating, and we're behind you, though it may take a while for us to catch up. :)

Peace,

Robert

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Maybe my hard time understanding was more of a question about why the cheeks even need to be molded rather than how the mold would be used.  

I thought it'd look better if it was all one uniform piece.

I might make the second coaming cheeks out of solid walnut to see the difference. That's the advantage of building two boats at once :)

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If I'm understanding the project, it is for aesthetics, as Dave says. Structurally, it is not a good application of laminating. Small "wings" of plywood, as are used on some plywood and fiberglass kayaks, are likely to be stronger and lighter. But drive on Bagarre and chase your muse.

Fair winds, Andy

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These should be plenty strong and not just aesthetic. 

Laminations are every bit as strong as a solid block of wood, if not stronger.

So once these are glued into the laminated coaming, I dont expect them to ever break free no matter how much force I put on them.

 

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Strength is a deceptive word in a technical application like we deal with in this forum all the time.  Tensile strength, compression strength, sheer strength, deflective strength...........  Laminating is used to increase deflective strength and to create strong curves.  In this case, no more deflective strength is needed beyond what a solid piece would do.  That being said, there is no harm in laminating in this application either.  This is why I concluded is was aesthetic.  I laminate for making Greenland style paddles simply because it looks cool.  Oh, and cause I can use up scraps.  

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More progress. Laminating takes time :)

Laminating the cheeks didn't buy me much other than the grain following coaming lines. To save time, the next one might just have solid walnut for the cheeks. I'm undecided.

This one has a sudo random alternating pattern while the second one will be nearly all walnut with two lines of maple .

 

Second kayak is almost ready for a frog shot too.

 

 

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