by Philip Jacobs
Shaping and smoothing the outside of my hull was a breeze, relatively speaking. With a sharp Surform and a random-orbital sander, I could knock down edges and blend flat strips into curves and contours almost at will. Sanding the inside, however, was another story.
I had learned a lot sanding and glassing the outside: how grain affects ease of sanding; why some builders prefer a sharp block plane over a Surform; and how epoxy resin unmercifully highlights any variations in sanding. But overall, it was quite satisfying to blend the many strips into a single hull.
The inside felt like a chore, and I approached it with trepidation. At this part of the process, the novelty of building a canoe has worn a little thin, and my focus tended to drift toward, 'get it in the water'. It's easy to rationalize that a smooth exterior is necessary for performance, but the appearance of the interior is only cosmetic. And from an aesthetics standpoint, most casual viewers see the completed canoe on the water or a roof rack and never inspect the inside very closely.
Pride and performance aside, I felt that the inside of the hull, especially the bow area, was the part that I would face each time that I paddled the canoe. Every construction defect and cosmetic flaw would taunt me with reminders of 'what could have been', if only for a few hours more of sanding.
I began by using a narrow paint scraper and a variety of cabinet scrapers to remove the big glue blobs. Removing the top knob on the paint scraper allowed me to reach further into the stems, and a curved cabinet scraper worked well in the tumblehome and sharper curves. I was relieved that I didn't need one of the home made, two-handled, long arm scrapers I have seen some builders use to remove glue drips, but became quickly reacquainted with of one of those basic rules of woodworking; glue is usually harder than wood.
Furniture makers are taught not to wipe off wet glue drips because it forces the glue deep into the pores of the wood around the joint, sealing the grain, and preventing absorption of stain and some finishes. Knowing, however, that the entire hull would be extensively Surformed, followed by thorough abrasion with several grades of sandpaper, I gleefully indulged my urge to keep a damp cloth handy during glue-up, and wiped off any 'squeeze-out'.
Big mistake. Although glue drips become brittle and snap off fairly easy when dry, glue smears form sort of an armor plate across irregular areas of the soft cedar, resisting reasonable efforts by sandpaper and scrapers. Because these smears fill low areas in the grain and between strips, they could actually be viewed as help in faring the hull, were it not for the characteristic of common woodworking glues to show up prominently as opaque, white blotches under the clear, epoxy resin.
These indicator blotches helped to clarify why sanding the inside of the hull is objectively more difficult. On the outside, high points are formed where the edges of strips join; leaving thin ridges and glue joints to be knocked down. On the interior, these joints form the low point of a concave profile, meaning that most of the faces of adjoining strips need to be hollowed out to form a smooth curve.
Even a jaded attempt to justify a multi-faceted, inside hull surface as intentional (to improve 'slip-resistance') fails when one observes the glue marks which have settled into the low points, highlighting unsanded joints. A lot of cedar was going to have to come out of that hull to make it smooth and pretty.
I had reasonable success with the old standby, a curved blade Surform, but that didn't reach into all areas of the hull. My next tool of choice consisted of scraps of floor sanding paper (left over from when we had our wood floors refinished years ago) wrapped around various blocks of foam. This extra heavy duty, 36 grit paper was stiff enough to fair ridges, but flexible enough to follow contours, and cut almost as well as the Surform (and those floor guys were going to throw it away!).
As my arms grew weary, I looked through catalogs (Klingspor's 1-800-228-0000, or www.sandingcatalog.com), hoping to expand my arsenal. I looked at discs, which sand on their faces; drums, which sand along the edges of a cylinder, 'flap wheels', which sand along the circumference of a wheel, and 'stars', which sand along the edges of stacked discs. But these all appeared to cut across, rather than with the grain of the strips.
I began to ponder how birchbark canoes or dugouts were ever built without random-orbital sanders. I was able to use mine on some of the flatter portions of the floor and ends, but the 5 inch pad bridged all but the shallowest curves, leaving swirls and gouges at the edges. I tried using 2 and 3 inch diameter sanding discs, mounted at the end of a flexible shaft, to reach into the tumblehome, but this was a limited success. I tried the trick of stuffing a pad under the paper on a vibrating sander, but this didn't remove material nearly as fast as desired. Perhaps I was expecting an easy way out for a task, which just takes time and patience.
In retrospect, there are advantages to having a variety of sanding and shaping tools, although it is possible to build an entire boat with hand sanding only. I am certain that other builders have addressed this problem in a variety of ways, and I would be very interested in hearing of their experiences and techniques for smoothing and sanding the insides of hulls, in future HUT! contributions.
As for my hull . . . , well, spring was approaching, and the words, 'good enough', became more of a mantra than any kind of question or quandary; after all, it is a 'first boat', and the outside looks pretty good. The inside is pretty smooth, and those white blotches on the inside have nothing to do with slip resistance, but I am working on a high-tech excuse that has something to do with cell phone reception or GPS navigation; suggestions are appreciated.
