2015-07-22

XXXVI - Transom Cap & Starting the Seats/Thwarts

I mentioned in the last post that the top of the transom would be covered in a cap piece. I made that in a quick session one night between baby feedings. I hauled out the steaming rig again and sawed up an MDF mold from my transom template. The hook-like indents on the sides of the mold are there so that I can get it firmly clamped down around the tight arc at the ends. -- clamps don't work on wedges!

Figure 163: Mold for the transom cap


Figure 164: Steaming the transom cap piece


Figure 165: Removed from the steambox and quickly clamped 



Ah...now the seats. The seats. The........seats. (a.k.a. thwarts....I call em seats herein)

The seats took me awhile to figure out. A lot of sittin' and starin' was needed before I came up with a method for this instance. You have a few things working against you at this point in the build:
  • You are off the molds so nothing is level anymore. 
  • Everything has self-faired so you can't trust your old molds as references 
  • Keel and sheerline are the best references you have, but the keel is hard to reach and neither one is particularly straight. 
So how the hell do mount a seat square and level with the waterline in a boat where absolutely no reference surfaces are square or level? Opinions vary -- some people reference the sheerline, others reference the keel, some people have homemade jigs specially-built for the purpose and others reference everything to a spirit level. They all work, but I didn't want to get into making more custom tools for a one-off part. Susan Van Leuven's book "Woodstrip Rowing Craft" has a good section on this and it looked fairly easy to emulate.

First thing is to span the gunwales with the rough stock you intend to use for the seat, positioned above the spot where the seat will sit. Measure on the plans how far down the seat should be (both forward and aft sides) from the sheer. Drop a perpendicular from the seat down the appropriate distance and mark the inside of the hull. You can't just measure along the hull from the sheer because the plans show only the vertical distance.  Do this for both sides of every seat board. The tilt on the seat won't be perfect but will be close enough you can adjust it later.

Figure 166: Marking seat/thwart height relative to gunwales


Before setting to work on the seats you need to measure between the marks on the inside of the hull. I use a floppy tailor's tape-measure for this because it's hard to get an accurate measurement with a regular metal tape. Lay out the measurements on the board and cut the ends -- you will have a bunch of trapezoid-shaped boards at this point. Test the fit and see that the seat fits into the hull and the bottom corners lie on the marks. If things don't lie quite on the marks, strategically trim the ends of the seat until they sit flat (no wobbles). 

Next thing is to pick up the bevel from the side of the boat. In my boat, the seats sit just above the bulge where the curvature is sharp. At this spot on the hull the bevel changes a fair bit over the thickness of the seat stock. Best spot to pick up the bevel for me was at the bottom edge of the seat because this is roughly where the seat will sit when it's properly beveled. I did this for all 4 corners of each seat and transferred the bevels to the corners. 

This method is better in a lot of ways than going from plans because it allows a custom fit for a hull that might not be exactly the same as it was when it was stapled to the molds. 

Figure 167: Estimating bevel for the seats/thwarts


The midships seat needed some adjustment to come square with the keel. I made the adjustments using a cardboard template and transferred the new shape to the board. After cutting it, everything fit perfectly. 

Figure 168: Cardboard template of the longest seat/thwart to aid with adjustments


Cutting bevels is the same as ever. Join a line between the fore and aft bevels on the underside of the seat and start planing. My bevels were all less than 45 degrees (measured form the top surface), but I was able to do most of the work with a handsaw (rough material removal) and a No. 3 Stanley plane. A little block plane is the best tool to clean things up as you near the final bevel. Procedure is the same as what I've described elsewhere. Plane to the line on both sides, add hash marks, plane away the centre.

Figure 169: Cutting the seat/thwart bevels


When the first pass on each bevel is done, you need to go back and forth a few times and adjust until the *top* of the seat sits even with the hull marks. After that plane carefully to remove a little bit on aft and forward corners of all seats. This will account for the slight curvature of the hull and close the gap in the centre of each seat. The whole thing will be hidden under a fillet eventually, but it's better for it to fit as tightly as possible. 

Figure 170: Main seat/thwart mocked-up


Figure 171: Aft seat/thwart mocked up


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