Aluminum on top of wood?

I mentioned in a previous post the thought of ACM panels being used (3 or 4mm thick) for decking, primarily for budgetary concerns. I plan to buy the acm panel this week and intend to mount the first piece directly to the ribs. I'll then be using aluminum angle to frame the decks, and am still up in the air about what to use for the decking. I'm open to using 3/4 plywood for the raised decks, and here is why.

1. Alot less money ( I need about 40 sq ft)
2. I like the sound deadening properties of wood
3. I feel like the wood deck won't need as much support underneath to prevent flex and the associated engineering that's needed with hatch lids made of aluminum.

Although I'm still unsure about what I'm going to cover the decks with, I know I'm not going to put carpet in the boat because most of the lakes I fish don't have a boat dock, and Ga red clay and carpet don't go well together, but I started thinking that I could use 3/4 ply for the raised decks with the ACM panel applied to the top.

My thinking is that I get the sturdiness of the ply on the upper decks (3/4" + the Acm Panel of 3mm = about 7/8" total) the hatch lids are now the same thickness, the Acm Panel will prevent any water absorbtion from the top, and whether or not I decide to vinyl, hydroturf, non-skid paint etc.....I'm working with an alumimum skin to adhere it to.

Thoughts?

1/2 wood, .060 skin on top. Problem is the alum is gonna trap water/moisture between the layers. I think your best bet is to use .100 alum and just add more bracing underside, I know cost is a factor.. the .100 alum is about 150 a sheet i think.. not sure how much decking you are planning to do..

Thanks for the input BP.

Do you feel like the water gets trapped coming up from the bottom of the ply? Sides? I'm trying to understand how it gets there in the first place if I glue the aluminum down to the ply, and again, I don't intend to leave the decks uncovered...meaning there will be another outer layer like marine vinyl etc..that I could potentially wrap the upper decks with then fasten it down.

I'm thinking I could run a bead of silicone or the like around the edges, and I still intend to seal the plywood. Front deck will need close to 40sq ft, and the back around 20.

The deal is, I'm wanting to put in a rod locker, and the hatch for it in addition to the others I have will likely be alot larger than my size 13 shoe, and I'm thinking the 3/4" ply will have alot less deflection standing on a lid, than a piece of aluminum. All the aluminum hatch lids I've seen are either framed with tubing and use a two tiered deck support (like bassboy's build), or they simply use a U-shaped stiffener underneath the lid (like the Trackers at BPS) and once the hatch lid is closed it overlays the surrounding aluminum, and I want everything flush if possible.

If you do use alum, I can bend it up for you no charge, But i agree, the hatches maybe need a heavier ply, My thought is metal sweats, Seal it the best possible and i believe it still will get moisture under there, Especially here in ga with the humidity... Likely it will be fine... I can bend whatever you want, dont hesitate to ask, I never did get a confirmed price on the alum sheet. I know scrap can be had for a few hatches for around 65 cents a pound if you can find the size you need..

3/4 ply with Skid no more applied.

3/4 ply with Skid no more applied.