Tuesday, July 22, 2008

Tech Tip Tuesday

One of the big enemies when you're building a cedar-strip canoe is the sanding. Most people do far too much sanding. There are several reasons for this:
  • failure to fair the hull with planes or spokeshaves
  • too much glue
  • poor quality strips
  • excessive use of filler
  • bad stripping technique
A good sharp plane will remove most of the waste material on the outside of the hull with ease and either a scraper or a round soled compass plane will do most of the interior.

Too much glue is a biggie. The glue is harder than the cedar, so removing the cedar with sandpaper causes "waves" adjacent to the glue. In turn, this will cause you to remove more wood to smooth out the "waves". It's fairly easy to avoid this issue. Just use a damp cloth to remove any excess glue from the interior and exterior of the hull during the stripping process.

Poor quality strips cause poor turns and excessive gaps and facets on the hull. This requires lots of material removal to get a fair hull.

Excessive use of filler (epoxy mixed with wood flour and fumed silica) results in the same problems as too much glue. Excess material should be scraped off with a squeegee when applying filler to the hull. (i.e. before it cures!)

Bad stripping technique can cause gaps and facets on the hull which will require more fairing and sanding.

It is important to remember that you're building a stress-skin composite hull - the separation of the two skins is important to the strength of the finished hull. If your hull is too thin because you removed too much material, it will not be as strong.

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