Clearance between bottom of plywood deck and hull.

[Daniel1947]

[FONT=&quot]I know there has to be a clearance between the stringers and the hull of approximately 1/4" (filled with 5200 or PB) to prevent hard spots.

My question is in regards to the outer section of my boat where the deck will be in contact with the hull, basically laying flat on the hull.

I can maintain clearance between the outer edges of the plywood and the outer sides of the hull. But, I am wondering if it is necessary to also maintain that clearance between the bottom of the plywood and top of the hull. My hull is completely flat for approximately 12 inches along the outer edge as I have attempted to illustrate. I do believe that the old deck was just laying flat on the hull along that 12 inches and tabbed in on the sides...I could be wrong. But I had no difficulty in removing the old deck along the outer edges after I cut through the tabbing on the outer edge. As always, I appreciate any and all reply's.[/FONT]

 

[zool]

Nah, you don't need clearance on the flat spots, just the hard edge against the hull side....but u should put some under there for glue and filler of the uneven surface gaps....so u don't get crazing.

 

[jigngrub]

I'd go for the 1/4" gap with a 1" wide bed of PB around the perimeter whether it needed it or not. I think it would be a better build.

 

[zool]

It really depends on how ur deck was pitched as designed. Some decks pitch from the center out to each side, for a gutter runoff, some pitch from the chines towards the center, for draining straight back on center. A 1/4" per foot is considered best practices for any glass deck. You may not have room for any buildup....its not needed to protect the hull tho.

 

[Daniel1947]

Thanks for the input guys. Zool, I don't know what the pitch was or if there was a pitch.:facepalm: Deck was in bad shape, etc., It is a 1989 Astro 18' fish and ski. The area along the outside of the hull, on both sides, is completely 100% flat. I can lay a straight edge from port to starboard and it lays flat along that 12". My original idea was to drop the top of the stringers a little below the sides, which would allow for a slight pitch towards center. However, we all know that would cause the outer edge of the plywood deck to be higher along the out edge and possibly "rub" along the inside. My idea now is to set that outermost strip maybe 1/8" to 1/4" above the deck and use PB along the outer edge to facilitate the leveling. This should yield a very small gap between the ply and the deck. I think the 3 of us are kind of in agreement on that. As always, thanks for the input Gig and Zool.

 

[ondarvr]

There is no need for a gap in that location. The gap is needed for plywood being placed on edge where it will have little to no flex when compared the fiberglass hull. When laying flat it flexes easily and does not create the same issue. The gap is needed at the edge of the ply and hull side, not below that in the location you asked about.

 

[Daniel1947]

Ondarvr.....so you are saying that if it flexes it can be laid flat without any spacers? In my drawing I have shown a strip of ply, not really a stringer, that is 1-1/2" wide x 1" high and runs almost the full length of the hull. This strip is very flexible and I believe was originally installed to allow for the original deck to be "stapled" to it. Since it is flexible, can I just lay it down with adhesive...either PB or 5200...without adding spacers under it?

 

[ondarvr]

Yes.

And on small boats the factories rarely space the plywood off the hull, they just drop the stringers or stringer grid in place and glass over it.