Saturday, August 1, 2015

Musings on how to make the seats

The original Glen-L plans call for a seat riser that runs from the forward frame to the transom, passing through this cutout in Frame #1.

So, I'm in this "blocking" phase. The next step is to attach blocking on the sides of the hull to support each end of the rear seat. (Basic "bench" seats are also called "thwarts" in nautical terminology.)

The original plans call for a full-length seat riser to be attached to the sides of the hull. That's the purpose for the unique cutouts on the sides of Frame #1 that you'll see on the Glen-L Utility model. So far, there aren't a whole lot of well-documented Utility builds. However, among those I've seen, most do not use the full-length seat riser. Instead, these builders simply attached blocking to support the seats.

The original plans also call for 2 separate aft seats, on either side of the boat. I'm not going to do that. I want a simple back thwart, and front thwart.

Glen-L line drawing of the Utility
I debated on the full-length seat riser. However, I decided against it for a few reasons. One is time, as I'm now quite anxious to get this boat in the water. Another is the fact that I'd have to either cut the frame cutout more, or plane the full length of the seat risers, because my cutout is less than a "store-standard" 3/4" depth. A third reason is the fact that I'd also have to make another cutout in the seat riser itself, to accommodate the butt blocks that connect the side panels of the hull.

Nope. Simple blocking it will be.

The next question is, "How to attach it?" I realized that if I install the blocking on either side first, then I'm taking something of a gamble on them actually being on exactly the same plane. I do not want my seats to slant, obviously.

The other matter to attaching the blocking on the sides first, is the fact that I'd have to retrofit the center support. I have already planned to build a different type of center support than Glen calls for, anyway.

How my center supports will differ:
Glen calls for 2 plywood center supports for the front thwart. These supports are glued to either side of the keel, and then attached to either side of blocking that is underneath the thwart itself. Like this:

Glen-L Utility
A Glen-L Utility at the "G8" Glen-L Gathering in 2014. Thanks to the kindness of this boat's owner, I was actually able to drive this one & take one of my children out in it. Note the construction of the center support under the seats.
I'm planning to build a different type of center support, based on one I saw in a photo of a 1935 Riva. Mine will have a single plywood support, mounted on top of the keel, on the centerline. I will have 1" x 1" blocking on either side of the plywood support, both at the top and bottom.

Center seat support on a 1935 Riva
Back to the point...
I had another idea. What if I build & install the center support first, then make sure the thwart is level... then, use the thwart itself as a point from which to install the blocking on the sides? It seems to me that I'd stand a better chance of having the seat installed level, once it's all done.

So first, I marked the sides, where the top of the blocking (seat riser) should be, at right angles to the frame. Then I taped twine from measured points on these lines, stretched across to the other side. Measuring the height from the keel to the twine, I found that each point was 8 inches.

I plan to make the thwart 12 inches wide. I want the center support to be slightly narrower, so I decided it should be 10 inches. Knowing that I plan to use 1" blocking, I then had the dimensions I need to draw out the center support.

Half-breadth of the seat support, drawn out on the computer.
So, I drew the half-breadth of the seat support in Adobe Illustrator & printed the pdf full-size. I then cut out the print & traced it, full width, onto poster board. Once I cut that out, I had a template which I can now transfer to the plywood.

Poster board template for the center support. So far, so good...

The next step is to actually build it. 

Let's hope all this works.

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