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Lapwing


Tom Lathrop

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Progress is slow but moving along.  Mold is lined off for strakes.  Graham made this a little easier than normal by cutting the molds in a shape that  helps but I wanted to work it out for myself also.  It takes a lot of juggling and eying to get it to look right.  That means it looks right to my eye, of course.  I think each builder might have a somewhat differing take on just what is "right".  Graham's plans will have this all worked out.

My transom is going to be built with an outer laminate of mahogany.  The photo shows it glued up on a form matching the curve of the plan.  A curved transom is a bit harder to build than a flat one but makes a lot of difference in the overall appearance of the boat.  A lapstrake is more difficult to build in the first place so it is no big jump to add a few garnishes here and there.

Lapwingtransomr018.jpg

Lapwingmoldr021.jpg

Lapwingmoldr023.jpg

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  Hi Tom,

  Thanks for sharing the project.  It's one thing to see the line drawing of a hull and quite another to see photos of the hull coming to life.  It must feel great to walk around and sight down the centerline at different heights and run your hand down the flowing form of the mold and look forward to laying the planks down and seeing the sweetly curving results.

  I'm trying not to drool too much on my keyboard because I'd like this computer to survive long enough to show me some sailing photos :)

  I almost wish I wasn't putting finishing touches on my boat now.  On the other hand it will be a lot of fun to camp on the outer banks this weekend (or maybe next).  The eternal struggle - sailor... builder... sailor... builder... I guess I should start looking for a project come springtime.  Any suggestions for a pretty little lapstrake camper?  ;D

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Graham does intend to offer the Lapwing as a kit.  Parts will be precut, including the scarfs.

Here is today's work.  The transom has been fitted to the mold.  Since the only permanent attachment at this point is to the keelson, only that has been glued.  The little blocks on the edges    are taped ply washers to allow accurate pre-positioning of the transom to the mold.  Strakes will overlap the transom.

Lapwingtransomr001.jpg

Lapwingtransomr004.jpg

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Tom,

You mentioned the curved transom.  Will this be included in Graham's plans/kits or is this just your own personalization/modification?

Thanks,

dale

The final version will also have a curved plywood transom but the laminated mahogany over the plywood is my addition.  Of course, anyone can add that on their own for a bit more pizazz.  Graham is moving right along and the interior parts are already cut and mostly put together for his beta kit version.  At this rate, he may finish before I do.  His shop is above flood level, mostly.  There are people beating him over the head about a 65' offshore fisherman so that may slow him down.

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  • 2 weeks later...

Finally got some more work done on Lapwing.  The strakes are all rough cut and scarfed.  Here is the garboard strake dry fitted and the lap bevel planed.  The next strake (#7) will have to be fitted and router trimmed to final shape before the garboard can be permanently glued.

garboardstraker.jpg

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I'm in the process of building a Charlotte canoe designed by Tom Hill.  I only have the sheer strakes to glue and then I can attach the outwales. What method are you using to mark out the strakes?  Tom Hill's method is to use the ribbands to mark out the strakes and you must always mark out the next strake before attaching the previous one.  

Being that said, when you mark out the next strake, it is necessary to attach shims the same thickness as the planking thickness between the upper ribband (the one toward the keel being the boat is upside down) and the plywood that your are going to mark your pattern on.  This is done at each station mold with a clamp.  The shim represents the thickness of the "not yet hung strake"  If the shim is not used then the strake will not fit properly.  Is this the method you are using on the Lapwing to define the shape of the strakes.

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Lance,

I do use the ribbands/stringers to determine the shape of the strakes but I route them to final shape.  I mark and cut them out oversize before scarfing.  I attach the two sections to the ribbands and mark an alignment line with a 6' straight edge so the scarf will maintain the proper shape.  Actually, I scarfed all the rough strakes at one time before beginning any final installation. On a smaller boat like Charlotte, I might have done it differently.

I did think about using a shim as you suggest but, by making the rough strakes oversized, it seems to make little difference.  I also ran the stringers to within a couple inches of the stem although Hill stops them at the 1st mold.  I saw a Charlotte under construction where the bow was a mess because there seemed to be a discontinuity between the strake shape aft and forward of this forward mold.

I also modified a block plane as Tom Hill did for trimming the laps but found that if I used a spokeshave for most of it and modified block plane for final shaping, it goes much easier.  I must also confess to using a power plane for some of the work.  Arthritis makes inventive cowards of us all.

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Tom,

You decided to add a mahogany laminate to your plywood transom. If we leave out the complication of the curve would you ever consider a solid wood transom? If we are concerned with durablity, strenth, weight, easy of contruction, and aesthetics.

Joe

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Tom,

You decided to add a mahogany laminate to your plywood transom. If we leave out the complication of the curve would you ever consider a solid wood transom? If we are concerned with durablity, strenth, weight, easy of contruction, and aesthetics.

Joe

Of course a solid wood transom could be used on Lapwing.  Whether one is better than the other depends as much on what the builder likes as much as objective factors.  The first point is the curve.  Leaving that out greatly compromises the aesthetics in my opinion.  I discussed that with Graham after he proposed it and decided that it was worth the effort for me.

I think the only factor favoring solid transom construction with no curve is ease of building.  Of course, it does not have to be laminated with mahogany lumber.  It could just as well be all plywood and most builders will probably opt for that as we have in all the other B&B boats.

After many years dealing with both plywood and solid lumber, properly engineered quality plywood get my vote for strength, weight, durability and maintenance. 

In the end, it's mostly personal choice.  My house furniture is mostly solid wood and my boats are mostly plywood.

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Solid wood transoms just don't make sense in a modern plywood epoxy composite boat. Wood expands and contracts a lot across the grain and has almost no movement along the grain. The lapwing transom is 18" wide which will have to be made from two or more boards and if you put any vertical support to prevent cupping or reinforcing for outboards etc. you stress the glue joints.

The thickness of the transom except for reinforcing for outboards, rudder hardware or the unsupported top edge needs to be no stronger than the side planking which in the Lapwing is only 1/4" which makes the ply transom much lighter.

While epoxy sealing keeps most of the moisture out of the wood, some water vapor will will pass through the barrier coating and cause the wood to swell. You can often see on boats with chine logs where the chine has swelled and cracked the glass sheathing or swelled enough so that you can see a raised line between the bottom and the sides. The same thing on solid wood transoms where the transom has swelled enough so that it stands proud of the sides.

I know that there are some solid wood transoms that are in perfect condition, but they are usually coddled and kept under shelter while not being used.

To me it is a no-brainer, lighter, cheaper more stable and if you want the rich mahogany solid wood look do what Tom did and glue a thin layer on the back.

In the photo is my lapwing transom ready for installation.

post-186-129497664448_thumb.jpg

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  • 2 weeks later...

OK, I finally got back to work enough to finish getting all 16 strakes on.  You can see that lapwing will be able to carry her sail with the broad bottom midships and fairly sharp turn of the bilge.

The sheer and second strake were left unglued to the transom to make it possible to get the hull off the mold past the tumblehome.  They should be able to spring enough to do that.  Much sanding and finishing work before it comes off though.  I will try to break it loose to see if I left some hidden screw somewhere that binds the hull to the mold.  Yes, it does happen.  The rig is tilted to give easier access to the underneath.

aVXQnk9.jpg

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