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Lapwing #5 build


John Turpin

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Nice job on the rudder blade John.

If it's not going to be left out in the sun for weeks at a time you might want to finish it with epoxy with graphite added to it. I used it on my centerboard and rudder blade and sanded it down to 600 grit, then buffed it. It came out looking like carbon fiber! I thought it really looked nice and purposeful on the boat.

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Nice job on the rudder blade John.

If it's not going to be left out in the sun for weeks at a time you might want to finish it with epoxy with graphite added to it. I used it on my centerboard and rudder blade and sanded it down to 600 grit, then buffed it. It came out looking like carbon fiber! I thought it really looked nice and purposeful on the boat.

I'd originally just planned to paint it, but you're the second person to recommend that graphite treatment.  Would the graphite add any UV protection?  The boat will spend 99.99% of its time in my garage, so I'm not sure UV exposure is that critical.  If I did that, I'd do the centerboard as well.

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Richard, I think I have worked out a spiling approach and have a tiny bit of confidence.  With the photos you emailed me and a book that I picked up over the weekend, I'm ready to tackle strakes 3 through 8.  I now understand what 'gain' is all about and am pretty sure that, with some practice, I can do that.  After researching many spiling techniques (and there are dozens of them), I think I'll be making a spiling truss.  It's basically two long strips of 3/4"-wide, 1/4" thick ply that define the top and bottom of the new strake.  You clamp them where you want the new strake's edges to be, then connect them to each other using more small strips of ply and a hot glue gun.  After it sets, you take the truss to the cutting table and draw your pattern.  When you've got the pattern drawn, you can break the truss apart and do it all again for the next.  It's a little more work than some of the other methods, but I think it's the most foolproof for me.

Hopefully, I'll have the garboards and #2 planks on by the end of the week and then I can start experimenting with that daunting strake #3.

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John, Richard,

The truss method is a good one for laying out the strakes.  It also allows you to have a good look at the final shape before you cut plywood.  I would think that drywall screws would be less time and effort as well as work better than hot melt glue for this job though.  I'm sure you have already thought of it, but you need to make the stringers long enough for the sheer strake and let the extra run wild off the transom for shorter strakes.

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Thanks, Tom.  I'm not sure how long it will need to be--at least 18'.  It's a long way around that curve.  I'll start scarfing together those spiling strips this week.

I hadn't thought about using drywall screws for the truss.  I was picturing using 3/4" wide strips, to match the landing width.  That would, however, preclude the use of screws unless I was willing to put screw holes in the boat.  If I instead made those strips 1 1/2", I'd have room to screw the truss members together without getting into the strake above.  Thanks for the idea.

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John,

If you use 3/8" for the trusses and 3/4" for the stringers, the 1 1/8" drywall screws will work fine.  I often use small 1/4" ply washers under drywall screws and if you do that, you can use 1/4" for the trusses.  Another option is to just get a box of 3/4" screws.

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Richard, I don't think I can describe it very well in the forum.  I think I'll need to fly down to Queenstown and holiday with you.  That way, I can use my hands as I describe it.  :-)

Here are a couple of photos that show a spiling truss clamped onto a boat on a jig.  It's pretty simple.  Once you figure out what you want your plank to look like, you just clamp the top and bottom stringer where you want the top and bottom of the plank to fit.  Then, you hot glue/screw the stringers into that shape using a series of small truss pieces that are attached at different angles (to give stiffness and lateral support).  Heck, even I could do that.  When you're happy with it, unclamp it from the boat and carrry it over to the plywood for marking.  It will flatten out when you remove it, but that's what you want.  Your ply will bend right back into the original bend(s) that the truss had.  Sure sounds good in theory.

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I experimented with the spiling truss idea today. l made a section that was about 5 feet long. It actually held its shape pretty well when I took it off the jig. When doing the real thing, I think I'll take some measurements and glue on some long pieces to help ensure that nothing in the shape has moved.  But, my proof of concept succeeded and I'll use this method tomorrow on strake #3.

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Hi John

How did you attach the 'trusses' - hot glue or screws.  I will watch with interest how you get on.  I experimented with my spiling batten today with strake three.  Roughed it out to scarf the ply together first.  Feeling a bit nervous on No. 3.  Still has quite a bit of twist at the stem.  I am away with work all next week so will not get a chance to do anything else until next weekend.  Happy to pass the batten (so to speak) and let you move into the lead.

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I used hot glue, but when working on the real thing, I'll use hot glue backed up with staples or screws.  Also, I plan to take some measurements. I'm not too worried about the plank widths--my truss pieces should preserve that shape. But, I am worried about that long 16' curve changing on me. That's a critical shape and can't be fixed if done wrong. I will take a series of measurements from the boat's center line to the top of plank # 3.  I'll then transfer those measurements to the plywood and make sure that my truss still matches that shape.  I'll cut the plank a little oversized, so I can make some small adjustments as needed.  Whew. Whose idea was it to build a lapstrake boat?

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