Chugach Range rising majestically behind Anchorage, AK.
The Voyage of                  INTREPID Line Picture of Intrepid, a Dorado designed by Jim Michalak
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Ok. The plywood has just arrived. Two sheets one-half inch marine fir AB plywood at $62 each and 9 sheets three-eights inch marine fir AB plywood at $65. Two sheets one-half inch CDX at $20 each for my assembly table, and one three-eights at $15 for temporary forms in the boat. This is a lot of wood. And it cost a lot of money. And it is all flat. And I'm supposed to turn it into a boat? Who the heck talked me into this anyway? Plywood Arrives

I had picked out the half inch marine plywood myself: all of the edges are clean, with only a couple of one mm voids. There are five substantially equal thickness plys to each sheet, and there are no knots or cracks on the faces. There are some plugs and putty on those faces, but otherwise, this is some good looking wood. I did not have much of a choice with the three-eights inch wood though. It seems that I emptied what was left of the lumber yard's stock. Although this wood was also good, some of the sheets had damaged edges. I should be able to work around the damage, however.

Now everything good I said about the plywood only applies to the marine plywood. The CDX, or exterior grade plywood was crap in comparison. Both sizes CDX had numerous voids all around their perimeter, with many knots on each face. The one-half inch had only four plys, and the three-eights inch had but three. That three-eighths inch CDX also tended to flex quite a bit, whereas the marine equivalent was very rigid. Mr. Michalak says that good exterior grade plywood is acceptable for the construction of the Dorado, but I wouldn't build a go-cart with the stuff I have found up here.

Marine plywood edge grain This is an edge grain picture of the marine plywood I purchased. While Marine plywood is constructed to specific (APA) standards, the only difference I was told between it and exterior-grade plywood was that the voids may be larger. They both use waterproof glue and come in the same sizes. All I can say at this point, since I have yet to actually work with the marine plywood, is that there is a definite difference in the rigidity and overall quality between the two types.






The picture at the bottom is of both sizes CDX plywood. If I used this wood for the boat, I would have to seal the end grain with epoxy filler. There is no telling what voids lie beneath the outer plys within the plywood. These voids can extend across the entire sheet, making a 4-ply sheet, effectively a three-ply sheet with the resultant loss in effective strength. Also, large voids near the surface plys could make delamination a real possibility. Not a chance that I would like to take.

CDX plywood end grain
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