Wednesday, April 30, 2008

Tech Tip Tuesday : Staple-less (MMMmmm...)

To be quite honest, staple-less construction of a strip-built canoe isn't all that difficult, really. It is, however very time consuming. Basically, you put the strip on the boat and using various different methods, you keep the strip in place until the glue sets. After the glue sets, you can apply the nest strip.

Simple, no?


There are a few difficulties that come into play.

First : Where do you put your first strip? In the class that I teach, the fist strip we put on the forms tends to be the feature strip, which is several inches down from the shear line when you build the boat. (Actually, it's UP from the shear line because the boat is upside-down as you build it.) It would be much easier to start at the sheer line. (at the lowest point of the sheer) Personally, I like the strips on the hull to be "horizontal" and not follow the curve of the sheer. I think this makes the boat look "bent". It offends my aesthetic sense of style, so I avoid it. (Ok, so I'm finicky.)

Second: How do you keep the first strips in place so you have something to push against when clamping? Some people simply nail the first strip in place - even when doing "staple-less". What we have done is to make "L" shaped brackets that will get screwed to the plywood forms. The long leg of the bracket can be about 4-6" long (depending where on the boat it will go - brackets at the bow and stern need to be a bit shorter) and the short leg can be no wider than the first strip to go on the hull. In the case of a features strip, this is usually less than 1-1/2" or 2" wide. Looking down from the top of the bracket, they are cut so that the inside edge is parallel to the strip at the station where it will be located. Carpet tape then gets applied to the inside of the short leg of the bracket for friction. You make sure that the bracket holds the strip tightly to the form and that the strip is fair. Clamp the bracket. Then screw the bracket to the form with 2 screws. Done.

Third : How do you apply subsequent strips? This is done several ways. The most recent issue of WoodenBoat (Issue #202) has a builder who uses fishing line to hold the strips down on the forms and in contact with the adjacent strips. I haven't tried it. If you're interested, buy a copy of the magazine and have a look. Another way is to make small plywood brackets that look a little like Pac-Man. They're circular and have a wedge shaped opening. You clamp the brackets to the form (one at each form) and then use two tape-covered wedges between the bracket and the strip to force the strip against the form and the adjacent strip. Why tape-covered? To keep the glue from sticking. If you're using cove-and-beaded strips, the wedge used to hold the new strip against the adjacent strip needs to have a mating contour so as not to damage the cove or bead. (depending on if you prefer cove up or bead up) A third way I've seen is people using the "L" shaped brackets and C-clamps. I've also seen people build a bit of "scaffolding" around the outside of the hull to push against. Others have used pieces of cove-and beaded strip and blocks with line to tie them down. Still others have used inner-tube tires. There are a million ways to skin this cat. You'll need to find the way that works for you.

Fourth: How do I finish the bottom? We build the bottom of the hull in halves, referred to as the "Football" You build all of the one side past the centerline of the hull, remove it , build all of the other side, trim the both halves to the centerline and glue them in place. Note something very carefully here. I said "remove". That means that you don't glue one of the strips at the turn of the bilge. To hold this in place, we've glued blocks to the strip that isn't going to be glued to it's neighbor and then screw this to the forms. The blocks are then carefully cut off when the finished half of the football is ready to come off. I've also had a student tape the first strip of the football in place. Creativity rules.

Fifth: How do I hold the strips together between the forms? Strips will, invariably, try to separate between the forms. One of my students came up with an ingenious solution. He got some cheap plastic spring-jaw clamps. He applied a short length of inner-tube over the ends of both tips (so as to form a "U" inside the jaws) The length was short enough that he could stretch the inner tube over the strip as he installed the clamp without it bottoming out in the clamp's jaw. Clever.

Last but not least : How do I work up to the sheer line? You can either strap the boat down to the form or apply heavy weight to the now assembled bottom of the boat to keep the hull on the forms and use the methods from the third section to build to the sheer.

By no means are these the only ways to accomplish these tasks. It's only limited by your creativity. If anyone else has some other methods that have worked for them, I'd love to hear about them!

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