Floor Materials on Aluminum Hull - Need Advice

Hi all,

Starting this project by installing a floor. I don't want to go the plywood route (though if epoxied 3x, it could be OK) because it's heavy and I need to save weight because it's an 18' boat that will have a 75hp Mariner 2 stroke and a 50 gallon tank (I need a lot of range) and an enclosed wheelhouse.

I don't want to buy starboard. It would be a $800 floor using that material. Can anyone give me advice as I've seen a ZILLION different composite materials and I do not know what is good, other than Starboard. I'm going for budget friendly here, though I know it will be expensive... just not $800 expensive. Also, anything that interacts negatively with aluminum is a no-no.

Also - for voids outside of the bilge (I'll have 2 750gph pumps), what foam is best? Can I use spray foam from Home Depot or will this rot/break down?

Thanks guys and gals for any advice! I'll post pics of the hull I purchased as I begin my build. It's gonna be a cool boat.

 

It depends on what kind of support is available for your floor, really, if the support frames are closely spaced, you could use ply that is relatively light-weight, and cheap. If there are wide areas to bridge, that have no support, then it becomes a different matter.

 

Do you know what kind of plastics / polys would work that wouldn't empty my wallet in the same way that starboard would?

 

It depends as well on the aesthetic result you would like to obtain, of course. I can tell you that the shipbuilding and offshore industry uses GRP grates and planking like these or similar:
http://www.acadianindustries.com/pdf/Fiberglass Grating Brochure.pdf
http://gefinc.com/sites/default/files/Product Brochures/Duradek and Duragrid - GEF Inc .pdf
By standard they come in sheets 6.0m x 1.2m or 4.0m x 1.2m (but can be ordered in other sizes too), are very easy to cut in desired shapes, are lightweight and anti-slip. The real saving comes from the ease of cutting and installation, which saves a lots of man-hours.
But no, they are definitely not elegant-looking.

Cheers

 

What about... aluminum?
I don't get it, this seems like a no-brainer...

 

Right. Rivet gun...

Otherwise, you can use plascore honeycomb and glass it and decore to fasten, etc. Comes direct from plascore with veil to lay glass on each side, like a 21 oz triax or 1808 or some such. Tons of work.

The ally much nicer and eaiser to deal with all around.

 

Ply is probably the best mix of cheap and serviceable. Alloy checker plate is used, but that is not cheap.

 

One thing to be aware of with alloy boats, and particularly if the underfloor area in unpainted, is the need to keep certain foreign objects out, especially dissimilar metal objects like lead sinkers or brass swivels, which can go to work to burn a hole in the bottom through electrolysis. Any gaps that can see things fall down in there, are undesirable.