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Cricket 11-24-2013 06:55 PM

Planked Half Model
Hi folks,
Been a while since I checked in. First off, I've made a change and closed my shop commercially. I decided that I was tired of the business stuff, and the jobsite stuff, and have gone to work for a bigger shop down the hall, doing project management, drawing mostly, learning InteriorCad which is a 3d design program plug-in for Vectorworks. It's an extremely powerful application, of which more later, maybe. I still have my shop, and I'm looking for a furniture or cabinet maker to share the shop with (Brooklyn Navy Yard). I'll start documenting some projects as the interesting ones come up, and time allow.

In the meantime, having my shop open has given me some freedom to think about various little projects that I would like to do. Boat models is one of those things, and I have started building planked, lapstrake half models. Planking a half model is an unusual approach to this tradition, but it has value in that some aspects of planking a full size boat can be worked out on the model, and also a scale record of the expanded plank shapes can be generated. Plus, it produces (hopefully) an exceptionally interesting object!

I've long been fascinated with the Swampscott type dories of Boston's North Shore, and I am considering building one out at my boat club. Years ago, I drew up a portrait of the sailplan for the Beachcomber, an exceptional boat from William Chamberlain's shop in Marblehead. I'll get bogged down if I try to describe it all here, so I will refer you to an article I wrote for my club newsletter.

The cover of this book shows a beachcomber under sail in Marblehead Harbor.

At any rate, here are some images from my model project, starting first with my sail plan.

And here are the hull lines.

These lines, and construction plans are from John Gardner's The Dory Book.

The half model is set up with half molds on a flat board (1/8" ply) that represents the hull centerline. I used 1-1/2" = 1'-0" as a convenient scale. The model is a manageable size (the 21' boat is about 32" long), and scale planking is relatively easy to come up with. 1/2" planking translates to 1/16". For this I used a sheet of 1/32" aircraft birch, which I cut in half and vacuum bagged together to make a 1/16", six ply sheet. The molds are cut from 1/8" Italian Poplar ply. The 1" thick transom is 1/8" mahogany, etc. etc.

I had the body plan drawn to scale in the computer, so I printed out the individual sections and glued them to the 1/8" ply mold stock, then cut them out and faired them on a little belt sander table.

I will continue this in the next post!

Cricket 11-24-2013 08:23 PM

Re: Planked Half Model
To continue...
The molds and transom are each glued to the profile board in their respective positions, corresponding to their position on the lines plan. I used cyanoacrylate for this, as for the whole project. I mounted the profile board to a piece of mdf with an "L" shaped block on the back to facilitate clamping in the vise in various positions.
This is the transom, expanded to its true shape.
The molds and transom are glued to the profile board, which is screwed to an mdf backer.

Dories have a narrow, flat bottom, usually about an inch thick. I used the 1/8" poplar again for that, gluing it onto the molds and then fairing the edge in a long, winding bevel to match the angle at each mold. This is just like it would be done on the full size boat.

Once the bottom is on and faired, the planking can start. I used bristol board to make plank patterns, wrapping a strip around the molds and marking off the knuckle locations from underneath. You have to be careful not edge set the pattern. It must lay flat and "normal" on all the molds. After marking the knuckles, I measured the widths to the inside bevel of the bottom at each mold, then faired the lines with my spline and ducks. The expanded shapes of boat planks can be surprising. I'll try to take a photo of the plank shapes laid flat when I'm back in the shop.

Once happy with the pattern, I traced it onto my planking stock, cut it out, faired it with a block plane, and glued it on the molds. It's a challenge working this small, trying to figure out ways of clamping things to a small, fragile setup. I ended up just starting amidship, and gluing a little bit at a time, holding it all with my hands til the glue set, then moving on. I've lost quite a bit of skin so far to the cyanoacrylate.

To be continued...

Cricket 11-25-2013 02:26 PM

Re: Planked Half Model
Planking up a model is just like planking a full size boat, but the pieces are smaller. It's interesting though, just how thick and workable 1/16" actually is. In the ends of a lapstrake boat, gains must be cut in the planks so that the plank faces end up flush right at the end of the boat. In other words, the lap merges to a smooth surface. On glued lap boats, like those I build, I cut rabbeted gains. I run a fine backsaw along the lap line tapering the depth of cut from a full plank thickness right at the end, to nothing at a point about 15 " back. The gain has a winding bevel, as well as a taper.

The photo shows a rabbeted gain. Also, the previous plank's edge has a bevel along it's entire length so that the next plank will land perfectly along the overlap's faying surface. In this case, the overlap is 1" - 1/8" at this scale. You can see how the planks merge from lap to flush at the end of the boat.

This photo shows a plank bevel, checking for a flat surface to land the next plank on.

More later. I'm off to pick out some rift white oak panels for a job.

joraft 11-25-2013 05:12 PM

Re: Planked Half Model
Cricket, I love it when you post your projects. They're always well documented, and always such great photos.

I'm really looking forward to watching the progress on this one.


Cricket 11-26-2013 12:51 AM

Re: Planked Half Model
Thank you John,
Right side up view.
This is a view of the inside of the planked model.

I put a deck cap on the model, prior to fitting the topmost plank, the sheer plank. This closes off the model so you are looking at the exterior form, not the internal structure. The profile board and molds were cut shy of the actual sheer by 1/8" to allow for this deck cap. It was fitted to fall inside the sheer plank, flush to the molds. Before putting this on, I glued solid blocks onto the profile board that allow me to fasten the final, permanent mounting board to the model. While working on the model, I just screwed through the profile board into my mdf backer from the inside. Before I closed the model up, I had to remove these, and go in from the outside.
This shows the deck plank in place. The model is now fastened from the outside to the backer board, which ultimately will be replaced by a nice plank.
In this view, the model is all closed up, and the covering board and rubrail have been installed. These are Spanish cedar, appropriately scaled for the boat.
Here's a shot of the model, set vertically in the vise to trim the rubrail at the stem. This vise is the best thing I've bought in a while. It's a Chinese knockoff of the famous Versa Vice. I tried to get the original on Ebay, but just don't have the patience for the bidding wars on rare "ish" items. This Shop Fox Parrot Vise performs pretty well, and is a good price. I don't know how I managed without one!

In the background is a 1936 Old Town HW, awaiting restoration. I may start in on that over xmas.

Meanwhile, more on the model later...

TahoeTwoBears 11-26-2013 01:54 PM

Re: Planked Half Model

Thanks for posting. Your stories and photos are awe inspiring. Makes my day. Thanks again.


Wonderwino 11-26-2013 02:53 PM

Re: Planked Half Model
Great looking model! I've always thought it would be fun to build a ship model. My Mom has a carved half-model of a clipper ship that was done by an ancestral captain in the 1800's, presumably while on a crossing. It is much more primitive than the precise model you are building.

I couldn't help but notice the canoe in the background. Canvas on frame? restoration project?


Cricket 11-27-2013 12:54 AM

Re: Planked Half Model
Hey, thanks. That's 1936 Old Town HW model that I am going to restore. It was a sailing model that originally had sponsons, and I may restore them as well. It's a wood and canvas canoe. I expect to end up with a boat much like this one, from the Adirondack museum.

Interestingly, the canoe I have, which was given to me by a friend, was originally sold in 1937 to an address just a few blocks away from my shop in Brooklyn. I don't know where all it's been since, but it has come back close to home.


Wonderwino 11-27-2013 03:05 PM

Re: Planked Half Model
How cool! So many of them were left to rot in the woods after aluminum and composite canoes came out.

JimKirkpatrick 11-28-2013 01:31 AM

Cricket, I love this thread.....I keep coming back to check on progress. You really got me wanting to make one of these! Keep em coming!

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