3/4 vs 1/2 marine plywood weight?

[fishrdan]

How much more does 3/4" marine plywood weigh compared to 1/2" marine plywood? Google was no help here...

It looks like I'll need about 5 sheets of plywood for the decks and interior of my boat and I'm really considering 3/4 for the added strength. The boat weighs 2105# and has a 1280# capacity, so I don't think I'll be affecting the boat too much.

What do you thing maybe 100# of extra weight?

 

[Bondo]

Re: 3/4 vs 1/2 marine plywood weight?

Ayuh,....

It'll be 33.3% Heavier....

Are you covering everything with Glass,..??
If so,... 3/4" is Overkill....

 

[Tacklewasher]

Re: 3/4 vs 1/2 marine plywood weight?

Ayuh,....

It'll be 33.3% Heavier....

Wouldn't it be 50% heavier?

 

[Joe_the_boatman]

Re: 3/4 vs 1/2 marine plywood weight?

Yep, 50% more.

Although, using 1/2" would be a 33% weight savings over using 3/4".

 

[tashasdaddy]

Re: 3/4 vs 1/2 marine plywood weight?

most any application on a boat 1/2 is plenty, you can get away with 3/8 in many areas.

 

[fishrdan]

Re: 3/4 vs 1/2 marine plywood weight?

Yes 33% heavier, but 33% heavier than??? I don't know what 1/2 or 3/4 marine plywood weighs so not sure how much weight I'll be adding.

This is going in to a aluminum boat so no glass/resin will be used to bond it into the hull, only going to be screwed to the aluminum stringers. The edges against the hull are free floating so I want to make sure its going to be solid,,, even 10 years down the line.

(Missed TD's reply,,,) The ply is not supported the last 8-10" near the hull in places and I felt some bouncing on the edges from this. Also, the 58x34 panel over the gas tank has minimal structure to support the floor and it didn't feel solid, sure you could walk on it without concern, but since I'm replacing all the ply I want to make sure it's going to be good for at least 10 years.

I was thinking of attaching a couple pieces of PT or redwood 2x4 to the bottom of 1/2" ply for additional rigidity, but thought why not just use 3/4? The 1/2" marine ply is $49 and 3/4 $61 so not that much of a price difference.

 

[fishrdan]

Re: 3/4 vs 1/2 marine plywood weight?

Oh yeah,,, 50% more weight than 1/2...

Guess you can see I'm not a mathematician

 

[Joe_the_boatman]

Re: 3/4 vs 1/2 marine plywood weight?

Well, 5 sheets of 3/4", price wise, would be $60 more than 5 sheets of 1/2". I went w/ the 1/2" myself, in my 18' aluminum boat. It's not attached to the sides, either. 1/2" was cheaper, lighter, and thus, hopefully will get me better gas mileage (.....maybe).

To be honest, it's your boat, so go w/ what you'll be happy with. You surely don't want to take someone else's advice, and regret it later. The 1/2" isn't rock solid in my boat, it has a little give to it. Definitely not "springy", but it's not like walking on concrete, either. If I had to do over again, I'd still use the 1/2". Actually, it's technically 15/32" - got it from Home Depot - that's what they carry.

 

[BillP]

Re: 3/4 vs 1/2 marine plywood weight?

Regular 1/2" ply weighs +-50lbs a sheet and 3/4" ply weigh +-75lbs. I went from 1/2" to 3/4" on a 17'r and it let me use less framing so a little of the extra weight was offset by less structure. I'd do it again in a heartbeat.

 

[BMOLCHANY]

Re: 3/4 vs 1/2 marine plywood weight?

Its not that much of a weight difference and it gives you piece of mind so go for the gusto.

 

[lundnisswa]

Re: 3/4 vs 1/2 marine plywood weight?

I had this same question and came up with 20lb heavier per sheet of 3/4 marine ply vs 1/2", I looked it up on the net but cannot remember the website, it was one of the marine ply manufacturers though.
I can tell you this, the 3/4" marine ply is some nice stuff and Strong.
Good luck on your decision.
Lund

 

[fishrdan]

Re: 3/4 vs 1/2 marine plywood weight?

Cool, I'm going with the 3/4" marine ply.

And to think I was initially going with $25/sheet 1/2" 5 ply exterior ,,, there goes the budget...

 

[tashasdaddy]

Re: 3/4 vs 1/2 marine plywood weight?

if your stringers run bow to stern, i used 1x4's every 12 inches and ran them across the stringers, then used 1/2 ply. it also provides an air space under the ply, and excellant base to attached the deck. i ran this boat for several years, and never had a problem.