View Full Version : 16 ft plywood lapstrake like a seaskiff

02-04-2003, 04:21 PM
I want to build a glued lap, flat bottom boat. I was thinking of covnerting John Gardners clamming skiff using the lines he produced for plywood botttom and recreational use.

Any similar designs in the 14-16 ft range? simmons sea skiff is to big. Anythoughts on how to make the planks the right shape for lapstrake-

Since the boat was designed for plywood sides I was just going to put up the whole side Line off one plank, "cut and paste" and then lay up the the whole side and do it again. -- I was going for planks apprximately 6 inches wide with a 3 inch overlap so I had a very thick hull. Any other ideas? Might chicken out and just do plywood on frame, but at least I'll think about this.

On Vacation
02-04-2003, 04:27 PM
Many straight sided flat bottom boats can be converted to lapstrake. Three inches overlap, NO!!!!!!! A lapstrake boat can be built lighter than a straightsided hull. Each lap creates a "batten" at the joints. If you are lacking in experience, think about locating a set of plans in lapstrake.

Keith Wilson
02-04-2003, 04:43 PM
Any sheet-plywood boat can be built with lapstrake sides if you want. Normal overlap is no more than 2x the plank thickness. 3" is WAY too much. For how to line off planks, see either Tom Hill's book "Ultralight Boatbuiding" or "Clinker Plywood Boatbuilding" by Iain Oughtred. Different methods, both work. Lining off is important aesthetically, since the plank lines are very visible.

Are you looking for a planing motorboat, or a rowing/low-speed boat? Steve Redmond is back in buisness, and has a couple of nice skiffs (http://www.sredmond.com/) in this size range. Otherwise, you can't go wrong with Wm. or John Atkin's boats.

02-06-2003, 10:49 AM
This opens up a world of possibilities, for example to do good things with old Popular Mechanics plans. One question - when converting a frame/plywood design to lapstrake, what do you do about landing the planking on the transom? Do you custom fit by cutting out the plank profile out of the transom, once the planks are lined off? I assume that the stem is taken care of by cutting a gain on the forward end of the plank.

[ 02-06-2003, 11:52 AM: Message edited by: WWheeler ]

Bill Perkins
02-07-2003, 11:24 AM
WW I'm building to Pete Culler's plans for a 24 ft. launch . They clearly show gains cut in the plank to land in one plane on the transom , which is straight in section . The molds ( also straight lines in section )are padded out as you build so there are no lap bevels .

One fine point Culler includes occurs when you fit the sheer strake .Where this final plank will land he planes down the straight lofted profile of the transom in a gentle curve ; not too tight for the plank face to conform to .This twists the plank inboard slightly as it runs from the aftermost mold to the transom .The top edge of the plank will come in about 1 1/2 in. from the lofted transom profile in the case of my boat , but you do this " Good To Eye " ( Culler's spec ) as you fit the plank .

Tom you could be the one to start a Movement toward building the many ply skiffs lofted with slab sides , Lapstrake . Have you seen the clamming/work semidories in Gardner's Dory Book ?

[ 02-07-2003, 12:26 PM: Message edited by: Bill Perkins ]

02-07-2003, 11:39 AM
Tom Hill's book has wonderfully clear instructions on how to build any flat-bottomed boat in plywoood lapstrake. How about a lapstrake San Juan Dory (plans available through WoodenBoat)?

Wiley Baggins
02-07-2003, 11:41 AM
I am not familiar with the skiff that you referenced, but I built a slightly smaller flat-bottom skiff with glued, lapped ply sides and a ply bottom. My approach (not saying this is easier/better) was to develop the panel, and assemble the sides off the boat. I then put the sides on as panels, rather than as individual planks.

02-07-2003, 01:27 PM
Pete, sounds like your plans are quite detailed. I'm not sure what one would do in cases where the plans don't give this information.

02-07-2003, 03:33 PM
Thansk to all for the comments so far.

Bill-- I have seen those smile.gif I have 4 Garbner books :D :D I like the wider bottom- semi- dories are semi-round. Not enough bottom space for the fishing I want to do.

Wiley--That's what I was wondering if someone could do- How much of a lap did you use? What thickness of plywood? I am concerned that when I have lapped the pieces as one apanel, I won't be able to get the panel to bend on the frame--but itwould allow a stich and glue lap starke boat.


Wiley Baggins
02-07-2003, 04:34 PM
Originally posted by TomMcKinney:

Wiley--That's what I was wondering if someone could do- How much of a lap did you use? What thickness of plywood? I am concerned that when I have lapped the pieces as one apanel, I won't be able to get the panel to bend on the frame--but itwould allow a stich and glue lap starke boat.


I believe that I used about a 1/2" lap on quarter-inch ply, maybe a bit more (which is what AngWood mentioned above 2X plank thickness).

Since the ply was only 1/4' thick (1/2" where lapped) it was not too stiff to bend around the mold (just one) and fasten to the stem and transom respectively.

Also important to remember, is that you need to cut the gain into the planks as you assemble the panels so that they are flush, not lapped, the last several inches (at least at the bow, you can notch the transom if you like). Actually, I guess you don't have to do that. I think (not certain who/if) that Chesapeake Light Craft recommend fairing the laps at the bow and transom with thickened epoxy for some of their kits.

As to stitch and glue, the "panels" were simply glued lapstrake, but the bottom-to-side and bottom-to-transom joints were stitch-and-glue. I doubt that I would use that approach (the stitch-and-glue joint) if I did the boat again. I'd be more inclined to screw-and-glue the panel to a chine log. Just a preference though, not a criticism of the technique.

Edit: One additional note, that the boat I built was frameless, but had a short deck, and thwarts to help it hold its shape.

[ 02-07-2003, 05:36 PM: Message edited by: Wiley Baggins ]