Tuesday, March 26, 2013

Tech Tip Tuesday

In the better interests of time and the sanity of both students' and the instructor's fragile faculties, I decided to forgo the sewing of the skins that was used to build the kayaks last year was not the best option for skinning the hulls in this class.

So, you ask - how are we doing this?


The sewing class that was going on upstairs was interested to see how we were sewing the skins on the kayak and were somewhat bewildered and disappointed to find us stapling the fabric to the hull.  This isn't that odd, really.  When canvasing a canoe, folks use either canoe tacks or staples to fasten the canvas to the hull.  We're doing pretty much the same.

Note that we're not using just any staples - we're using stainless steel staples 3/8" long.  The fabric for the skinning is 8oz polyester from Dyson Baidarka & Company in Bellingham, Washington.  I like the way this fabric works, frankly.

The procedure is pretty straightforward.  With the boat upside down (or right-side-up if you're doing a deck...) we draped the hull with fabric and get it centered and aligned before we tack it in place at the sheer with thumb tacks.  We then take the staple gun and start to make a closely spaced row of staples through the fabric about 1/8" away from the top edge of the sheer in the middle of the hull about a foot long, pulling towards bow and stern to keep fabric taut.  We then pull the fabric taut around the boat and staple at 1/8" away from the sheer at the other side.  By closely spaced, I'm talking about an inch apart - sometimes less.

When we get near the ends, we cut down the middle of the fabric from the end of the fabric toward the stem, aligned with the keel.  I then seal the cut ends with a small butane torch - a very quick pass is all that is required.  We'll give you an object lesson why later...  The fabric is then pulled around the stem, stapling from the keel towards the sheer.  Excess fabric is cut away at the far edge of the stem and sealed.  The process is repeated with the other side of the fabric at the stem and then repeated at the other end of the boat. 

When the sheer and the stems have been trimmed and sealed with the torch to prevent fraying, we put a little bit of thickened epoxy over the stems to help seal them and to smooth out any bumps and edges.  When done, the boat looks like this:

Stems look like this:

Because this boat is a kayak, we'll put the deck skin on at the next class.  We'll then steam-iron out any wrinkles in the fabric before draining the water and setting the sole temperature to 450°F (with a digital meat thermometer) to shrink it a bit.  At this point, the skinning would be done for a canoe and the boat ready for paint.  In this case, it is a kayak and will get a deck skin, too.

Oh - I mentioned that I'd talk about why a quick pass with the torch is all you need.  The torch is VERY hot and I usually just sort of wave it past the cut edge of the fabric to keep it from fraying.  The student was doing this and may have had a momentary distraction or bit of inattention.  He got a surprise:

The surprise was a pretty large hole over the sheer clamp.  As you can see, we added a few staples at the sheer and the edge of the hole and put a bit of the thickened epoxy on it.  Fortunately it is in an area that will be covered by a rub rail, so it won't be seen and is high enough so that water will not be an issue.  WHEW!

More on the deck skinning in a bit.

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