plywood deck thickness questions

[seanymph85]

Attached is a picture of decking supports for one section of my Sea Nymph 14R Big water. I am wondering if given the closeness of the supports I could get by okay with 5/8" or 1/2" thick plywood for the decking material.

 

[64osby]

1/2" will have no problem with sag or bounce with the dimensions in the pic. 5/8" would be industrial.

What are you sealing everything with?

 

[nurseman]

I agree with 64osby, 1/2 should be just fine. Question, are you going to put pour-in-foam under the deck? If so, then 1/2 will be super solid.

 

[Star]

Seanymph,
Very nice support frame for your deck. I am sure that you could even go down to 3/8" good quality exterior ply. Every pound I put in my 14'er is critical because I have a 15hp 4 stroke. It is an open StarCraft Fisher so I put a light removable deck covered with carpet. It has worked out great for me. The home depot indoor outdoor is cheap and it drains in a flash. I used screws and ferrules to secure it not glue. I get 3 to 4 seasons out of it, and it is great on the feet.

 

[seanymph85]

Honestly for now I just used some Thompsons water seal stain I had on hand. I used two coats. I know there are other better sealers but that is what I had on hand and used it since resources are limited. I chose not to use treated in part due to expense but also due to some types can apparently cause corrosion damage to aluminum.

I hadn't thought about the pour in foam, it would add buoyancy. Though I have never worked with a product like that. I am making it readily removable, so it can dry out between uses or if some water happens to get in the bottom.

I have a 25hp mercury on this but still am trying to keep the weight down and am keeping the deck/plywood as low in the boat as possible. In the middle two sections the bottom of the plywood will rest on the outside edges of the two aluminum ribs going across the bottom in each section and there will be aluminum brackets in several key spots for support where the plywood overlaps the "frame."

I too only planned on using carpet in the fashion "Star: is using it. The plywood will be screwed to frame so if it deteriorates it can be unscrewed and replaced down the line.

For now at least I won't have decking at all in the bow section in front of that seat or in the transom area in back of the rear bench seat. The section in front of the rear seat only uses two by fours as compared to the section the frame in the picture provided is in.

 

[64osby]

Great move not using treated wood.

Thompson's is not the best, but using what you have works. Bottom feeding at it's best.

You may also want to look at sheet foam under the floor.