Thanks for the info. It seems very simple and logical now that you explained it, I appreciate the help. When I look at the lofting for the side panels the maximum length is 18' and 1 and 11/16". If I join the two 8 footers and the 2 foot 6 inch section it gives me 18', 6" which is plenty, correct?

: It is not a matter of marine ply vs. non-marine. It is related to
: metric vs imperial/ english/ inch measurements. 3mm and 4mm
: plywood is obviously specified in metric measure. Those panels
: are likely 2500mm x 1250 mm -- again, metric sizes-- which are
: roughly 98.4" x 49.2". That is slightly larger than
: the 1/8" plywood sold in 4' x8' sheets.

: But nothing is consistent in the world of lumber where 'nominal'
: sizes rule. Measure the stuff yourself.

: To answer your question: If you are joining two panels for those
: side panels then each one will need to be stretched out by 2.5
: inches, or you can join the two 8' pieces and add a 5"
: piece.

: You have some other options, too. It may be possible to redo the
: layout of the cutting plan so you can get the extra wood you'll
: need from a 'scrap' area on another panel. To get the length you
: need out of 8' sheets you are going to need to piece together 3
: pieces--but one can be 8' and the others can be any combination
: that adds up to the final size. So, if you are using a butt
: joint with two 98 .5" parts you'll end up with a part
: 197" long. If you are trying to create that part from
: 96" plywood you use one 96" piece and add two more to
: make up the remaining 101". That might be a 48" piece
: and a 53" piece. Or it might mean using some other
: combination of lengths.

: With butt joints you probably want to avoid splicing a 5"
: piece to the end of the panel. If ther is a block behind it to
: reinforce the joint, that block might get in the way of your
: stem connections. However, if you add your 5" piece to the
: center of the boat , and reinforce that itha an additional piece
: of plywood glued to the inside of the boat, then you can
: significantly strengthen
: The cockpit area-- which can be a good thing.

: If you are using scarf joints then you'll need to refigure the size
: of your pieces to allow for the extra material lost to the 2
: joints.

: Hope this helps.

: PGJ