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Kamis, 12 Mei 2016

Correcting Mistakes II The Usefulness of Square Corners

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When we went to put sheets of plywood on the top, er, bottom of the boat hull, they didnt really line up.  WTF?  It seemed unlikely that four sheets of plywood were manufactured not quite square, so we had to look elsewhere.


When we assembled the stringers with the cross beams, we had squared the pieces more or less, but little errors at the quarter inch level really add up over a 20 foot boat.  We hadnt thought to square the boat up as a whole unit.

So now we measured corner-to-corner to find that there was a difference of about and inch and a half.  Not giant, but enough to make the plywood fit funny on top, er, bottom.  We hadnt made a rectangular boat hull, wed made a parallelogram.


That night I had a dream:  We were using a come-along to square up the boat.  Brilliant!  Thanks, subconscious!  So that morning, we grabbed my come-along and screwed big-ass eye bolts into the opposite (long) corners.


My come-along didnt go the distance, so we borrowed a hooked chain from the boat trailer and doubled it up.


We worked for a while to find the route for the chain and the come-along that when tightened wouldnt tear the building form apart.


We then started working my rusty come-along to square the boat.  Kai was working the come-along originally until she realized with horror that one of the two stops that keep the ratchet from violently unratcheting broke off and fell out.  She didnt want to have to explain to people for the rest of her life about that gnarly scar across her forehead so she passed on that job.


So I got to work the come-along.


After a half dozen clicks under tension the boat was approaching square.  Oh wait, too far.  Back off.  Whoops, too little.  More tension.  We played that game back and forth for a while.


Until finally the two corners were within a quarter inch of each other. Once we got the sheeting on the bottom screwed and epoxied down, the boat would stay square.


Next we sheet the bottom of the hull.

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Kamis, 31 Maret 2016

Hull Finish Work or Correcting Mistakes III

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I like to joke that I bring Old World Craftsmanship to my work.  Old World like Neanderthal, the fine kind of workmanship you get from precision woodworking tools such as heavy clubs and sharpish rocks.  One of the things I like about building is all the layers of increasingly fine-tuned craftsmanship one brings to a project.

So all of my corners, more or less, meet each other, give or take a half inch or so.  Unfortunately, to coat the whole thing with fiberglass, the tolerances had to be a little more fine than that.  I knew all along that I was going to have to make all the edges smooth and even.


With all the lumber we ripped, we had no shortage of useful shims.  I made little shims to cover all these under or over cuts.


I didnt worry about fit that much, just that the shim covered the error.  I knew I could trim and sand the results.


I had to coat everything with a first coat of thin epoxy, then followup with thickened epoxy.


It was a lot of gooey mess and didnt look any too pretty mid-process.


I held the shims in with little brads until the epoxy had set.


After the epoxy set, I pulled the brads and trimmed off the extra.


The fiberglass sheeting calls for rounded corners to make a good bond.  I pulled out my router for the job and bought a 3/8 inch rounded bit.  That was the minimum radius that Glen-L suggested.



God, that is a scary and amazing tool.


It left beautiful rounded edges.





Next, we fill all the holes with a non-oily wood filler.  For some reason, Ive always loved this process.


4 million screw holes come back to haunt me.  I filled ever one as well as various chips and dings and rough corners.


 Followed by a day with an orbital sander.


 

It slowly starts to look pretty smooth and nice.


By the time we were done, it was lovely.  Smooth and beautiful with edges that looks like magic.

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