The Tongass!
Step 14) Filling & Fairing Exterior Seams

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(Click pictures for full size image)

Filling and shaping chines

The finished chine
Whew! I've got a boat hull in the garage! The next step is the filling, fairing, and shaping of everything on the outside of the boat in preparation for glassing all the seams and sheathing the boat in fiberglass. I'm using 12-oz biax on the seams. Sides get 10-oz cloth and the bottom will get 2 layers of 12-oz glass which will overlap the chines. Because of that, the chines will have the biax and the 2 layers of bottom cloth over them (36-oz total) and do not need separate glassing. If I decide not to overlap the bottom glass over the chines, then I'll put 8" wide 10-oz tape on them (already on my shop shelves.) More later (below).

Filling an outside chine corner Renn's way is a) filling it with a putty knife and the thickened epoxy (wood flour + silica in my case) and b) leaving it rounded for glassing over. I'm certain that he follows with a sander to properly shape the chine prior to glassing. Since I'm no artist, I chose to fill the chine in a more methodical fashion that is more time consuming but for me at least, results in a nicely consistent accurate chine shape. I came up with this method when building another boat and liked it, so I'm repeating it hear. It also works for shaping wood (unfilled) corners such as at the transom, and you can assume that I used this technique throughout.

As shown in the diagram (click to enlarge), I paint the plywood edges with plenty of epoxy (catch the drips inside the boat with a brush) and then fill the chine the best I can with my thickened epoxy. Not having the talent that it takes to get it right the first time, I just let it cure, sand flush, and re-fill as necessary to make a nice squared-off corner ready for shaping. To shape the chine itself, I sand a flat (split the angles as shown) on it from one end of the boat to the other. It is very easy to eyeball this bevel to make sure it is perfectly consistent. For this chine, the bevel ended up at about 3/16" wide. Then you go back and round either corner of the bevel thereby converting it to a rounded chine corner ready for glassing.

After shaping the chines to get them ready for glassing, the bow and transom joints need shaping. In my case, Renn's idea of offsetting the bottom panel assembly into the stem 1/8" to reduce fairing worked wonderfully. I could've offset slightly deeper, like somewhere between 1/16" or 1/8" more. If the point of your bottom panel assembly is not 55 degrees as specified by Renn, then do not offset too deeply into the stem. Now would be your opportunity to make a minor correction and make it all fit and look well. A bit of extra panel ahead of the stem is good for that since it is backed with the stem and can take some fairing without risk of being made too thin.

The bottom line with my bow (pardon the pun) is that the bottom panel assembly met perfectly at the side panels but in spite of my efforts, the angle formed by the fairbody of the bottom panels was a bit less than 55 degrees. I had to remove about 1/8" off the leading edge. Here's what I did:

  • Use a straight edge on the bow to estimate how much (and how far) wood needs to be removed
  • Draw a line to keep you honest and sand down to this line, checking the boat's bow profile from both sides. Use a straight edge and your eye to make sure the bow is straight and transitions nicely into the curve of the fairbody. This will leave a varying flat on the front of the bow.
  • Now that the profile of the boat is correct, you want to make the sides taper into the bow to ensure a fine entry, so mark a centerline along the flat
  • Using a low-angle block plane and sander, remove wood to transition the sides into the (fine) bow point. Check with a batten in all directions. Look at it and check it from both sides. When you are done, both sides should transition nicely into the bow point with fair curves and the boat's profile should be perfect. The picture shows my results and about how much wood I had to remove.
Next, a 3/4" wide flat must be machined into the bow from where the curve on the bottom panels start down to the tip of the bow (now shown.) I'll be putting a 1/2" layer of plywood on this flat for the purpose of screwing a 1/4" thick strip of high-density polyethylene plastic (HDPE). Renn prefers UHMW only, but a) I want the plywood to be there so I'm not screwing into the hull itself and b) HDPE can be had in a nice white to match my hull and UHMW is overkill for protecting the bow (IMHO).

Fairing the bow
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