Installing a Plywood Sole

[LMB]

My concern has to do with face grain orientation. As a general rule I have always followed that the the grain would run perpinducular to the stringers as the plywood should be marginally stronger this way. However I have encountered situations where it would elimate a seam and reduce waste to run a short section parallel to the stringers. I have encountered that situation again on my current job. Since this is a small inboard boat, there is a narrow 2' wide section of floor that runs about 7' on each side of the engine (there is a removable panel behind the engine) In this application I can eliminate a seam by running parallel to the stringer the entire 2'x7' length or stay perpindicular and have a seam at about 4'. Will use the same amount of ply either way. Stringers are centered about 12" apart so there is plenty of support. Suggestions? Oh, btw this is a 1/2" plywood glassed with mat on both sides.

[War Whoop]

I do not think it matters with support every 12" and glass on both sides of the plywood.

[LMB]

I should clarify that there is no blocking between the stringers along the length, just that the stringers are spaced 12" apart. I think you understood that though. This is one of those I could go either way on, but I'm always open to opinions.

[War Whoop]

Panel width is the killer not length, if you are still worried then make the stringers wider at the top.

[alan white]

Marine plywood has enough extra (and solid) layers that the odd number of plies (with one more ply on the faces) has less effect on strength. Either way, in other words.
Ordinary plywood (3-5 ply) can be a real problem wrongly oriented however. Use common sense.