Building A Pack Canoe - Part 6: Fairing And Fiberglassing The Interior

Now that the canoe was off the form, it was time to work on the interior. To do that, we needed a set of holding cradles...

Remember back when I told the story of my eye injury? Well, it was cutting the wood for the cradles that did me in. I eventually finished them, but I know exactly which piece (one of the bottom cross members) originally held the errant wood chuck before it came flying at me, so every time I look at it I get a grim reminder to be more careful.

Anyway, working on the interior is just about twice as hard as the exterior. Not only is the canoe no longer firmly attached to the form, you have to work inside a confined space that is all concave in cross section. That meant that the same tools we used on the outside would be of limited use or downright useless on the inside. A block plane was out of the question, there were only small sections that provided access for my 6" RO sander and long sanding blocks were only helpful for sanding along the length of the canoe. I have some tools that would be considered kind of exotic to the average canoe builder, but (sorry) you go to war with the army you have. I happen to have a pretty nice army.

First off, though, I had to make a tool that would waste away most of the wood. After looking at many books and websites, I found most everybody's solution for interior scraping to be less than desirable.

This is the tool I came up with to scrap away the glue (there will always be much more glue on the inside since you can't easily wipe off the excess while the boat is still on the form) and do the bulk of the stock removal. I wanted something that was both robust and could be pulled along with two hands without digging in too much. I rounded the edge of an old plane iron and screwed it at an angle to the end of a long hardwood handle.


Here it is in use. The end of the handle rests on the surface and the tool is dragged backwards. It made quick work of wasting away about 90% of what had to be removed.











Having a musical instrument building background, I tend to take that kind of approach for much of my other woodworking. A small canoe like this is not much smaller than an upright bass fiddle, so it was inevitable that I would use similar tools and methods as would be used in the construction of a bass.

This is a small scrub plane that I made several years ago for hollowing out archtop jazz guitar tops and backs. It is made from a piece of mountain mahogany (very hard and dense wood), a 1/4" thick slab of silicon bronze and an old file that I heat treated and ground for a blade. The bottom has a gentle arch that just happened to match the curve of the inside of the canoe nicely. It is a roughing tool and it really hogs away a lot of wood in a hurry.

This is a commercially available (through instrument making suppliers) convex bottomed plane that has both smooth and toothing blades and an adjustable throat. It is prohibitively expensive, but I already owned it so I used it. The toothing blade has grooves milled into the back face. This allows you to take cuts in any direction without tearing up the wood fibers








This close up shows what the tool marks look like when the toothing blade is used. It cuts shallow grooves in the wood that are easily sanded out. By crisscrossing back and forth, a very fair surface in easily obtainable. Its ability to cut just as well across the wood fibers as it does lengthwise makes this plane a winner for this operation.










Here's a shot of Lady BK deep in the moment while working on the end of her canoe. I'm sure she was thinking, "If I knew this $**{!#@ canoe was going to be this much work..." Still, she slogged away admirable.
















This photo shows how much wood we scraped and planed away before the final sanding. I weighed all of those shavings for future reference. They only weighed 11 ounces. A quick computation told me that we had removed about 8% of the remaining wood during the interior fairing process, so I guess my original estimate was pretty much spot on. This kind of info will be useful for future ultra lightweight projects.

Now we were down to 11 pounds for the bare hull before glassing the inside. After the final sanding and vacuuming, the inside was ready for us to apply the glass.










Because of the vee-shaped hull bottom and tumblehome/side junctions, we decided to add an extra layer of fiberglass to protect these areas. We cut 2" wide strips along the bias (45º angle) of the cloth weave. We used shorter scrap pieces and overlapped the ends by about half an inch for continuity's sake. This saved us from having to waste large amounts of good glass. I would have preferred uni-directional glass cloth for this application, but I knew the bias cut would be plenty strong enough.

We epoxied these strips into place as you can see here and let them cure overnight. We then sanded the edges to a feathered edge so that the glass laminated over them wouldn't get cut through when we sanded it out.

Next was a football shaped piece of glass to further reinforce the inside of the boat. Conventional wisdom dictates that smaller pieces be placed over larger pieces to avoid sanding through the larger piece during the finish sanding of the laminate, but we knew we weren't going to get anywhere near as fussy with the inside as we were with the outside. No matter how much you care for a canoe, the inside is always going to get abused. You can avoid bottoming out on landings and hitting rocks, etc., but you will always be on the inside, wearing away at the surface. Given that fact, and the fact that we weren't going to use a gloss varnish for the inside (so little things like seams weren't going to show), we decided to go for the easiest way to apply two layers of cloth simultaneously. We knew that the smaller football shaped piece would get dragged around by the heavy squeegeeing we were about to do, so we trapped it underneath the larger piece and made sure we didn't sand too aggressively when it came down to smoothing the interior.

Here's the cloth laid along the inside of the boat and dry brushed into shape.














The ends were slit to allow the cloth to fit around the inner stems and a little vee-shaped "dart" was cut out to allow the end of the cloth to butt up against the stems. Later on, we would put 4" wide pieces of bias-cut cloth over the stems and resin them in place.










At long last, with all of the fairing done and the glass laid in and wet out, we had a hull that would remain stable as we worked on the fit and finish work. We added another light coat of Clear Coat to fill out the weave a bit, but we made no attempt to get the surface as smooth as the outside would need to be. A slightly rough surface on the inside is actually a help in eliminating slipperiness, and since it won't be touching the passing water, it won't create excess frictional drag like it would if we left the outside this way.





After the resin was hard, I used the same 2" slick to cut away the excess glass and then bagged it up to use as clean scraps for the glassing of trim, etc.

We weighed the boat at this point and found it was a fat 14 pounds. With the extra glass on the inside, I figured there was about 15 oz, of glass and 15 oz. of resin, for a total of about two pounds. The extra pound was resin that either was absorbed by the wood (no getting around that) or the little bit of resin that we filled the weave with (one 6 oz. batch).