Thwart-less rowboat possible?

[PAR]

A framed lapstrake isn't lighter then a glued lapstrake, even if the glued laps have support behind the laps, which are quite small on 1/4" plywood.

[BATAAN]

Personally I like a smooth interior for when I turn it upside down and hose the sand out. The stringers weigh a pound or two total, but clutter the inside in my view.

[PAR]

I agree about the stringers cluttering up the insides a bit, but 1/4" planking just doesn't offer enough material at the lap to make fair curves or reasonable longitudinal stiffeners. Now you can let the laps stand proud and back fill with epoxy (upside down construction), but I think this is less then a desirable solution. CLC uses a notched lap, which seems to work, but the fair curve thing rises up again and this is a damn fiddly thing to have to do to the edge of 1/4" plywood. The stringers can be cut with a trapezoidal cross section so they shed water in both upright and inverted conditions and they don't have to be especially big either, but yes, I agree they are dust catchers. If it wasn't for the weight savings of the planking thickness, because 9 mm plywood takes a fair curve in glued lap.

[BATAAN]

If you could build upside down over a mold with stringers, don't fully bevel the lap but let it stand proud a little for more gluing, remove the shell and put strips of cloth/epoxy on the inside of the laps, that would be quite strong and hopefully fair.
Pete Culler used to pad his molds as he planked straight-sided lap boats, giving more beam than the lines, but removing the need to bevel laps except for the gain at the ends.
Aeolus Boats in Davenport CA used to build many different designs, dories and prams, using ply with stringers and his boats were very strong and he could build one in a very short time with plastic resin glue. They weren't really lap, but multi-chine.
I must agree that getting a strong fair lap in 1/4" ply is much easier if the battens stay in.

[Russ Kaiser]

My original design was to use single piece, scarfed plywood sheeting.

I am wondering if I this dory proposed by BATAAN could be modified to use the three strong frames specified and then one or two laminated stringers evenly spaced between the bottom and the sheer and installed in notches in the frame, transom, and stem in lieu of lapstrake construction.

As for hosing dirt and sand out of the boat; this boat is intended for fresh water use and launched for a pier or jetty. It will probably not be used for fishing, simply for exercise. Keeping the interior clean is not much of an issue.

Russ

[BATAAN]

The one I built so long ago was 1/4" ply sides, not lapped but in a sheet, and lengthened with a ply butt block fastened with clenched boat nails. Very crude but still going strong. Scarfed sheet would be quite a bit better both in looks and maintenance.
If using sheet for the side, I don't think the stringers are necessary, as the curve of the material imparts enough stiffness to prevent "oil-canning" in this very small craft, though obviously it is stronger with stringers in place.
The seat stringer could be incorporated somehow on the outside of the frames and do double duty and save weight I suppose.

[waikikin]

Originally Posted by BATAAN

If you could build upside down over a mold with stringers, don't fully bevel the lap but let it stand proud a little for more gluing, remove the shell and put strips of cloth/epoxy on the inside of the laps, that would be quite strong and hopefully fair.
Pete Culler used to pad his molds as he planked straight-sided lap boats, giving more beam than the lines, but removing the need to bevel laps except for the gain at the ends.
Aeolus Boats in Davenport CA used to build many different designs, dories and prams, using ply with stringers and his boats were very strong and he could build one in a very short time with plastic resin glue. They weren't really lap, but multi-chine.
I must agree that getting a strong fair lap in 1/4" ply is much easier if the battens stay in.

In reference to the lands, some ski boats here built in ply have a batten installed in the land- making the plank "thicker" than the ply just in the land, forward at the stem the planks gerald out but at the transom dont, Regards from Jeff.

[BATAAN]

Jeff, I remember seeing some rough water dive boats built that way. Trapped the stringer in a good structural place and make nice spray rails.