: Looks like these are my only local options in marine plywood.

: Douglas fir A/D quality 1/2" is $55 a sheet

: Another supplier has Meranti or Okume but only 3/8" thick or 3/4".
: 3/8" Meranti is $97.50 and okume is $112 a sheet.

: I have someone asking me to build them a boat. I am trying to decide on which
: plywood to use. I am leaning toward the 3/8" Meranti because I feel
: like it will be better quality ply. Playing with some 3/8" plywood
: mockups I don't really think that is going to be an issue. If were were
: beating around the surf then maybe.

: The Douglas fir is much cheaper but it is A/D quality and I am afraid the
: core will have voids in it. I don't know this of course, just a feeling. I
: realize I could turn the A face toward the cockpit and put the ratty side
: away but I don't like having a ratty side period.

: Given these choices what would use? Shipping in 1 or 2 sheets of plywood will
: not save me anything. Shipping costs are just to high. So I need to buy
: local (for now).

As I see it, you have quite a few options.

3/4 inch wood is a bit heavy, but the weight of the frames is not great, so the boat will weigh about 24 pounds perhaps, instead of, say, 21 or 22 pounds. Not a big deal. A "D" side can be covered with a piece of veneer, and voids can be filled with epoxy and sawdust. Edges can be painted a contrasting color after filling and smoothing. This could be very decorative with a clear vinyl skin. Or. you can use the same edgebanding techniques used in cabinet making to hide the plys of the plywood, and any evidence of voids. There is plenty of choice for edgebanding materials for 3/4 inch plywood.

3/8 inch plywood is too thin to use for the frames. I used plywood this thin several years ago for a prototype frame and left it outside. It didn't take long to deform a bit. Over time they'll warp from use. Most of the pressure on the boat will be squeezing them, and they'll flex, and eventually retain a curved shape. A couple of the forms I made were too flimsy for the width of the boat, so I reinforced them by adding a piece of 1x3. These retained their shape over the years, so I'll recommend the process if you decide to go with using the 3/8-inch material. I think a 1x3 is ugly, and overkill. You could probably get the necessary reinforcement by gluing on considerably thinner pieces of wood. Thje frames are irregular hexagons. Adding 6 short pieces of 1/4 by 3/4 wood strips to just one side of your plywood will stiffen things considerably. A contrasting wood would be decorative. The edgeds of the strips can be planed to give the reinforcements a "D" shape so they blend into the plywood if you wish. Or, use a conventional 1/2 round moulding. You don't have to bring these reinforcements all the way to the corners, but if you do they'll provide a wider bearing area for your stringers, and you can cut a groove into them to provide a recess for your lashing sinew.

For an even wider bearing surface--and somewhat more work--cut your frames from the 3/8-inch plywood and use 3/4 by 3/8 or 3/4 by 1/2 inch strips for your "edgebanding". plow a groove in these which is 3/8 wide and half the thickness of the material (1/4 inch deep if you use 1/2 inch thick strips) Bend these around the edges of the forms, fitting the plywood into the groove, and glue them on. You meay need to use a heat gun or even steam to get them to bend enough. but the curves are pretty gentle, so you might get by with just using bar clamps. One advantage to this method is that the ends of the reinforcements provide nice pockets--as good as mortises--for the stringers to fit into. And the frames are as stiff as "I" beams without adding much weight.

I use a 1/2 inch birch (A-B) for my frames. The plys could be held together with wallpaper paste but I'm sure the glue they use is much stronger than that. I have confidence in the epoxy coating protecting these from ever getting enough water in them to delaminate.

Something I've considered trying is to use the 1/4 inch birch floor underlayment panels. These have a good side and a side which is stamped with a series of alignment marks. Ugly marks. But I could laminate two pieces witht he marked sides being hidden in the middle. This would give me 1/2-inch material. The stuff is usually available in the odd size of 5x5 sheets, which would certainly be enough for 2 boats. Since it is designed for floors, the glue used is very water resistant.

For that matter, you should be able to find a nice cabinet quality plywood with A-A or A-B faces and small or non-existent voids. That would work jsut fine for the frames as long as it was sealed on all surfaces with epoxy.

Tom's plans are based on measurements to the outside of the stringers. With his method of plastic frames and aluminum stringers he makes the frames large enough to surround the tubing. If you go with wood frames and lashed-on stringers, your frames will be somewhat smaller. If you lay out paper drawings of these, you should be able to arrange them jig-saw-puzzlewise so you can get the frames for 2 boats from a 4x4 sheet of plywood. If you want the wood grain to be oriented in the same direction on all the frames then you'll use more material.

If your stringers are thick enough you can cut your frames with straight edges and still have enough space between the outside of the stringer and the frame, so the skin doesn't touch the frame. It is quick work with a circular saw and a straight edge. Having straight edges makes it easier to band them, either with thick, reinforcing, pieces or with thin veneer strips.

Just some thoughts for you to ponder. Good luck with your project.

PGJ