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CS17 #260


ecgossett

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I know your looking out!  Gotta have a little fun with posts.

On a different topic, scarfing.. After marking my boards I realized doing the 1-12 for scarfing may not work as the layout given with the plans doesn't have 3 extra inches. I was just planning on scarfing the vertical joints for sides, not where they attach to bottom... Does anybody scarf with just the 9 sheets of plywood and how do they layout the sides to fit??

If I order two gallons of epoxy from B&B is that enough to get the sides put together? I don't want to order more as I go on a 90 day patrol (sub) in June.

- Edward

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A scarf of 8:1 is plenty.  As to layout: I can't help you, didn't build that boat.  You need to join sheets together to make sides and bottoms, the joint of sides to bottoms is not a scarf, but stitch and glue.  Order the epoxy as you will, but it won't go bad while you are at sea.  The stuff you order when you get back from sea Graham may have had when you left  ;)

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   I think I used 8:1 scarfs.  I remember thinking long and hard about how to cut things out.  I cut the side and bottom pieces so they were a little bit oversized then after scarfing I cut them down to size.  I spent a LOT of time making sure I wasn't rough-cutting the pieces big enough to interfere with the other parts that are cut from those sheets.

   I think I remember Graham telling me that the layout sheet showed plywood panels that are slightly smaller than actual, so you've got a little more wiggle room than it looks like on the drawing.  I think BS1088 is actually a little larger than 4' x 8' and graham drew the sheets 4' x 8'.  This is a somewhat vague memory so I hope Graham or someone else corrects me if I'm wrong...

   I also put numbers on the full, uncut ply sheets (and the drawing) so I wouldn't mistakenly cut a piece from the wrong sheet later on.  Each time I cut a piece out of a sheet I made sure there was still a number on it.  I've still got a couple of cutoffs with numbers on them ;)

  Two gallons is more than enough to get the side and bottom panels scarfed up and stitched together.

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Rather then troubling yourself with scarfs, try the Payton (Sp?) butt joint. A lot of people have been credited with inventing this joint, though who knows who really did.

I use a scalloped version of this joint, which makes perfectly flush butt joints in plywood.

I scoop out a portion of the outer veneer, getting slightly into the second one as shown. I use a 7" or 10" disk sander for this, but any tool could be used, like a belt sander or power plane.

In this shallow depression I fill with thickened goo and fabric, which is typically biax. After you do a few, you'll get good enough to make them perfectly.

I use fairly stiff Mylar sheets, but you can use plastic sheeting or scrap plywood covered with packaging tape. Place this over the joint and apply enough pressure to get ooze out. Of course you do both sides this way.

The plans show a similar way of doing this, both sides at the same time too, except they aren't hollowed out. This works fine too, but it requires more fairing to smooth out.

The resulting joint is overly strong, flush, easily to fair and doesn't need extra length for over lap, like a scarf does.[attachment=1]

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  I think BS1088 is actually a little larger than 4' x 8' and graham drew the sheets 4' x 8'. 

There is no BS 1088 made in the USA.  So the dimensions are metric.  Thicknesses are 3,4,6,9 etc. mm and the sheets are 220mm X 440mm.  Which is just under 49" X just under 98".  Many people have used but joints like PAR is mentioning.  I like the scarf much better.  Cutting the scarf joint intimidates some people, it really shouldn't, but then each has to decide their own comfort level.

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Someone who knows I sail and love boats offered me a 1968 Bristol 25' in good shape, all wood interior, boat stand, 4 year old Yamaha 9.9, all electronics GPS, 5 sets sail, one set being 1 year old...

I would only have to transport boat from Atlanta, and varnish the mahogany interior.

Some regret was felt as I turned him down and gave a phone number of a friend who is a teacher and could really use a boat.

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I have the STBD side panels cut out!! Finished up at 10:50pm tonight. We lined up all three sheets up wood to draw out the entire site per the plan.. We overlapped the ends by 3 inches to include scarfing room.. The mistake made was forgetting to add extra length into the middle section... Not sure how I'm going to fix this. The very end piece is no chopped off yet so might be able to extend it.

I'm also playing with the scroll saw trying to eliminate jagged splinters when cutting.

I'm probably going to wind up using a rasp instead of a hand plane until I find a good plane.

- Edward

post-1729-129497682591_thumb.jpg

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  I know of two good ways to reduce splinters when cutting with a jigsaw.  The first is to use a new blade.  The second is to trace your cut lines with a razor-knife before you cut the part with the jigsaw (cut just outside the line with the saw and plane back to the line).

  I would rather use a bad plane than a good rasp.  You can tune a cheap new plane or a garage sale used plane to work fairly well but if you buy a good new block plane you won't be disapointed with it.  A good plane (new or used) is an amazing thing and in my opinion worth investing in.  I would go for a medium sized low-angle block plane if I were only going to have  single plane in my shop.

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I would rather use a bad plane than a good rasp.  You can tune a cheap new plane or a garage sale used plane to work fairly well but if you buy a good new block plane you won't be disapointed with it.  A good plane (new or used) is an amazing thing and in my opinion worth investing in.  I would go for a medium sized low-angle block plane if I were only going to have  single plane in my shop.

I agree with all that Ken says here except the part where garage sale used planes can only be made to work fairly well.  That may be the case some times, but you can find some mighty fine ones at garage sales as well.  Regardless of where you get one, get one!  It will make a huge difference in how well pieces fit and look. In the grand scheme  it will be small part of the money spent and a major contributor to the work.

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I'm sure it was a lot easier for my Spindrift 9, but I cut both out simultaneously by stacking the plywood.  But then I scarfed the plywood before cutting anything.  I don't know if this is even practical for a 17 foot boat.  But if you have lofted one side and cut it already, copying it, using it as a pattern, as Ray has stated is superior to anything else.

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Going back to cutting with the jig saw - If you can adjust how aggresively the saw cuts, set it to the lightest cut that still provides a fairly easy cut.  Also notice that when you are cutting across grain or diagonally, you probably are getting more splinters on one side of the cut than the other.  Plan the directions of your cuts so that the minimal spinters are next to your cut line - cutting with the grain.  Also remember that many edges are mated to another where they will be covered by tape, a fillet, or whatever.  Its more important that the edge is fair than it is to be un-chipped.

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I agree with Ray that it is preferable to cut 18" scarfs instead of 48". It works fine if you plan your work properly. For CS17 sides I don't cut the sheer line until after I scarf the panel so that I will have an alignment reference. As long as I have been making scarfs I can't guarantee perfect alignment without referencing the straight edge. Once you have glue and release film in the way it is hard  to tell if each side of the scarf is perfectly positioned so that you don't end up with a bent panel.

If you cut the hull panels separately you need to clamp both sides together and plane them to a matched pair.

I once had a CS17 builder who marked out the side panels twice and when he cut them they were different. He called me to ask which one was wrong.

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The butt joint I mention is easy to align, just mash the two edges together, tack in position grind and tape. If the bottom and side panels are rough cut initially, then joined (scarf or butt) you don't have an alignment problem, because you'll loft the actual bottom or side panels after they're joined.

Of course this requires a fairly large work space or doing it on the floor. I used two 4'x8" layout tables clamped together, but many don't have this luxury. The floor works and things can't fall off it either.

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