Plywood thickness

[Christian Linder]

Hello fellow boatbuilders!

I am going to build my first boat, a Melanesia. I just got the building plans and now I am getting the materials. 

I was looking for marine plywood and I am having a hard time to find 6mm plywood sheets in my area (Barcelona, Spain). I just talked to a store where they have 5 mm or 8 mm.

Could I build the Melanesia with 5 mm or 8 mm thick plywood sheets? Better go for the thinner or for the thicker sheets? Would I have to do some adjustments during the building process?

Thanks for the help!

Christian

[Ricardo Aráoz]

I'd go with 5mm and glass it inside and out. That should compensate for the missing millimeter, and the boat will be better protected.

[paul anderson]

Interesting question. 5mm would be my choice due to weight issues with the 8mm ply .I doubt the 3mm difference in thicknesses would make a huge difference in strength overall. You could layup more glass in areas you consider would benefit from more strengthening.Some sheets i used on my build where 6.5mm as opposed to 6mm and one does notice the weight difference between these sheets.

I would go with the 5mm if the quality is good.

[Éric Bouvéron]

On the Tiki 21 plans, it is clearly mentionned that 5mm or 6mm are of no importance, and that any (5 or 6mm) of the available plywood may be used. It may well be the same for the Melanesia. And I support Paul's comment about the weight issue.

[Christian Linder]

Ricardo, Paul and Éric thanks for the quick answer!

Now a lot of places that may have 6mm are closed here due to holidays but I can't delay the construction because now is when I have time to do it... So I am going to buy the 5mm sheets and do some more glassing.

Pictures coming soon!

[boatsmith]

go easy on the glassing,, it will add a lot of weight and the boat won't sail well... 5mm is fine.

[Éric Bouvéron]

As I said, Tiki 21 can be built with 5 or 6mm.
I think Boatsmith is right about the weight. Just use 5mm as you would use 6mm.

[Christian Linder]

Ok, I also received an e-mail from JWD saying that 5mm is perfectly fine so I'll stick to that

[Pippo]

More important would be the number of plies. 5 plies would be much better than 3.

[Christian Linder]

Good thing to keep in mind for next time! I didn't know about the plies and didn't ask for that. I just got my 5mm sheets and will start tomorrow with cutting the parts.