Glue laminated gunwales
Posted by Sandy
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Glue laminated gunwales January 05, 2021 11:51PM |
I'm gearing up to put glue-lam gunwales on my new boat: The Whale Rider
This will be a big decked white water dory. The side panels are 18-1/2'' feet long.
The deck will not be set down from a gunwale the way everybody else does. The deck will stretch from the top of the side panels across, at least in the middle 8' feet or so of the boat. I need a fat tall stout gunwale on the inside only, so the deck can bolt down onto that ledge. There are two ways to make a thick gunwale: steam bend one thick piece of wood or make it a glue lamination from lots of thin strips. The gluelam is stronger and easier. That's a hard combination to argue against.
It's worth noting too this is an oddly experimental boat. Traditional stitch and glue is probably the best, most long-term durable choice for beginning boat builders. Stitch and glue is a lot of work but it's a proven way that makes an incredibly strong lightweight long lasting boat.
This boat is just for me to play with. For this boat no two parts will be glued or glassed together. All major parts: the bottom sides gunwales and deck will bolt together over a either a thick foam gasket or a thick bead of "Marine Silicone" caulk. That way any part can be replaced. At any time. Which in a way--if it works--would make these boats.......eternal? :=)) We'll see.
Once this boat is done I'll make plans available, for both the new bolt-together method and traditional all-in-one-piece stitch and glue.
I made a bunch of 2" inch tall by 1/4" inch thick strips of ash. Starting with 4-quarter stock (a full 1" inch thick) you can set the table saw blade the right distance from the fence, so a freshly-sharpened ripping blade makes three equal width strips with two passes. Running those through a thickness planer makes them all a guaranteed thickness, all approximately 3/16" inch thick. Six such strips makes a gunwale a full 1-1/4" inch thick. I'll glue it all together with a zillion clamps and Tightbond III glue.
But I also needed to angle the edges of the strips, so the top of the glue lam ends up parallel to the floor when the glue-up is done.
Guiding a zillion thin strips through the table saw by hand is hard to do by hand, without gouging a few edges. So I built a jig to hold the strips firmly in place as they run through the the saw a second time, with the right angle set to the saw blade.
Tomorrow I'll do the glue up.
A glue-lamination gunwale is stronger than a single piece of wood of the same dimensions. A lot stronger. That's why they use gluelam beams for long spans when building a house or a commercial building. Glue lams are the way to go. This will be my fourth boat built with gluelam gunwales. I wouldn't do it any other way.
In a few more days I'll make a follow-up post showing how I used (waxed) blocks and lots of clamps to help put it all together.
This will be a big decked white water dory. The side panels are 18-1/2'' feet long.
The deck will not be set down from a gunwale the way everybody else does. The deck will stretch from the top of the side panels across, at least in the middle 8' feet or so of the boat. I need a fat tall stout gunwale on the inside only, so the deck can bolt down onto that ledge. There are two ways to make a thick gunwale: steam bend one thick piece of wood or make it a glue lamination from lots of thin strips. The gluelam is stronger and easier. That's a hard combination to argue against.
It's worth noting too this is an oddly experimental boat. Traditional stitch and glue is probably the best, most long-term durable choice for beginning boat builders. Stitch and glue is a lot of work but it's a proven way that makes an incredibly strong lightweight long lasting boat.
This boat is just for me to play with. For this boat no two parts will be glued or glassed together. All major parts: the bottom sides gunwales and deck will bolt together over a either a thick foam gasket or a thick bead of "Marine Silicone" caulk. That way any part can be replaced. At any time. Which in a way--if it works--would make these boats.......eternal? :=)) We'll see.
Once this boat is done I'll make plans available, for both the new bolt-together method and traditional all-in-one-piece stitch and glue.
I made a bunch of 2" inch tall by 1/4" inch thick strips of ash. Starting with 4-quarter stock (a full 1" inch thick) you can set the table saw blade the right distance from the fence, so a freshly-sharpened ripping blade makes three equal width strips with two passes. Running those through a thickness planer makes them all a guaranteed thickness, all approximately 3/16" inch thick. Six such strips makes a gunwale a full 1-1/4" inch thick. I'll glue it all together with a zillion clamps and Tightbond III glue.
But I also needed to angle the edges of the strips, so the top of the glue lam ends up parallel to the floor when the glue-up is done.
Guiding a zillion thin strips through the table saw by hand is hard to do by hand, without gouging a few edges. So I built a jig to hold the strips firmly in place as they run through the the saw a second time, with the right angle set to the saw blade.
Tomorrow I'll do the glue up.
A glue-lamination gunwale is stronger than a single piece of wood of the same dimensions. A lot stronger. That's why they use gluelam beams for long spans when building a house or a commercial building. Glue lams are the way to go. This will be my fourth boat built with gluelam gunwales. I wouldn't do it any other way.
In a few more days I'll make a follow-up post showing how I used (waxed) blocks and lots of clamps to help put it all together.
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Re: Glue laminated gunwales January 09, 2021 03:06PM |
No glue yet. This is a first pass rough-in to get the strips all cut to length with staggered semi-random joints.
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