: John,
: I kind of figured you would go your own way no matter what anyone said.
: OK, there is more.
: There are distinct engineering qualities to every material we use to build
: boats. There is no way you can get the stiffness of a plywood panel at a
: comparable weight from sa strip composite. Strips work in a kayak because
: of the tubular nature of the stucture. If you build a flat panel of strips
: and glass it will be very flexible unless you lay on a lot of layers of
: glass/epoxy and/or make the strips very thick. In the end the weight will
: be the same or greater.
: The same thing goes for foam core. Even if you use the most expensive marine
: foam panels it will take a lot of glass/epoxy to get the stiffness of a
: piece of plain old plywood. I got this straight from a naval architect who
: is constantly besieged with queries about building foam core versions of
: his plywood/glass designs. It costs twice as much and the hull will be
: every bit as heavy or heavier.
: The PDR is supposed to be a big ungainly box that flies a ton of sail. It's
: hydrodynamics are so bad making it lighter will not get you much. Because
: of the outrageous amounts of sail used, making the box lighter may take
: away necessary ballast needed to stay upright. And, finally, if you want
: to fly a maximum of sail the box has to be strong enough to support the
: mast and everything that is attached to it.
: You have a choice. You can spend the next several years trying to outwit the
: laws of Newtonian physics or you can build a plywood box like everyone
: else and be on the water in short order.

Hi Charlie,

The foam experiment does show the strips may be slightly heavier then the Luan, maybe, because I slopped the epoxy on the foam, laid the glass on, slop coated and laid on the strips, laid on the second layer of glass 8 oz, and slopped it with resin. This was just for a one day quick set up of the experiment. Normally I squeegee the excess epoxy for weight savings. Now if you add a finish to the Luan plywood that would add some weight also. So all in all they are probably close to being equal in weight. Strips for the hull bottom simple aren’t practical or strong enough. If I can find Oakum I’ll check it out. I’m leaning towards the Dave Gray type of construction and add strips on the foam glassed sandwiched like in the experiment just to add a different look. It won’t be for weight savings as you pointed out and as the experiment shows.

John