New deck, ply or aluminum?

[snowman48047]

2000 model 20' Lund Alaskan SS. I replaced the front deck a couple years ago. Now I need to replace the aft deck. IF I decide to use sheet aluminum how thick would I need? 1/8"? 3/16"? aluminum stringer supports are maybe 16"-18" span. I need maybe 56"x12' of 5052 or 5086 (I think) for the aft deck. I am the original owner. Replacing the front deck was time consuming. I don't think I care about spending $500 if the deck will then be bullet proof. Now I'm wondering also if the transom is still ok. Had a repower (2 years ago) and nothing was mentioned by the shop that did the install. I wont even start this project untill after duck season, in December. Decisions, decisions....what are your thoughts guys?

 

[Scott Danforth]

the issue with using aluminum is its slippery, its expensive, and it will be as heavy if not heavier than the wood. it will also dent and deform under your feet if not properly supported. In most cases, on larger boats/yachts, the aluminum deck has a layer of 3/4" teak which adds stiffness, support, and traction

5083/5086 are generally hull plating. 5052 is easier to work with, however easier to dent. you will need a minimum of 3/16" assuming you have adequate support underneath. if your supports are standard boat stringers, your spacing is a bit far apart, you may need to consider jumping to 1/4"

you may have to buy a complete 60 x 144 sheet or 72 x 144 (depending on what our distributor stocks).

 

[Woodonglass]

According to what I've learned here on iBoats AND my own research, ALL the HIGH $$ Aluminum Boat MFG, use aluminum Decking.

Top 5 Aluminum Boat MFG's

 

[Scott Danforth]

Not arguing the use of aluminum, nearly every yacht I work on has an aluminum deck. All covered in 3/4 teak bonded with a special epoxy to form a composite deck surface. Without the teak, the deck is easily oil canned by walking on it.

Its actually an engineered structural member of the boat, usually tied into the harpin

 

[snowman48047]

No Title

Here is a pic of the fore deck after I tore it out. You can see at the top of the picture what the spacing is, roughly 16-18 inches. I'm thinking 3/16" and I'll cover that after primer and paint with something softer and less hot and slippery, shop pads?...weight I don't think will be much different than if I used epoxy coated stuck ply. Cost...don't really care.

 

[crkranz]

3/16 aluminum sounds perfect. Maybe cover them in Nautalex vinyl.

 

[Woodonglass]

Cut some of the pink or blue slap foam insulation boards from Lowe's or Home Depot so they'll fit in the cavity when placed on edge and you'll get a really firm deck. Also you NEED the added benefit of Flotation. You should do this for the entire boat!!:nod:

 

[snowman48047]

Woodonglass,
​Ya I didn't add any up front when I did that half. I now have an unlimited supply of blue foam so I will be adding it to the aft deck. Now I just need to find some sheet aluminum.

crkranz
I've got enough vinyl left over from the front to do the rear. Will the same adhesive work with the aluminum? I am sure I need to primer and paint it but how well will that vinyl adhesive stick to painter aluminum? I used the Henry brand stuff before and it worked great on epoxy covered Aruco plywood.

Rivets or screws for the deck? The center area holds a 27 gallon tank and is screwed down so thinking screws again. Problem is screws works loose. And I have a few broken rivets near the seat mounts.

That just lead me to another thought. How much support will the seat base need? Probably more than the 3/16" aluminum will provide? Maybe go 1/4" but now weight becomes an issue I think. You can see in the pic the center area of the seat base goes through the deck so adding anything underneath is out. Maybe just stick with 3/4" Aruco...

Should I be worried about the transom?

 

[bob johnson]

my lowe came with a .105" thick aluminum floor...as one sheet....120" x 68"....it was on supports that were about 12 " apart but also had blown in expanding foam underneath and between the supports...but it all absorbed water..and the boat gained about 600 lbs!!.... I am replacing with road signs that are tempered .125" thick....they are probably 5086.... I cut out the wet foam and added dow corning Styrofoam from home depot...cut to fit and stacked vertically... it should add some support, but I also have the extra thick and tempered aluminum!...the floor will be fine!.... there is NO WAY youd need to go to 1/4", in my view.... especially if you fit some foam under there.

I found .125" x 6' x 12' sheet aluminum in 5052 for about $373 delivered!