New way of looking at flotation

Friends:
They say life's greatest pleasures are its simple ones. They also say something along the lines of the best engineering solutions being the most obvious ones. My problem is I overthink things, resulting in less than ideal outcomes sometimes.

So here's the scenario. I have a 16' Starcraft project boat that I am wrestling with the ideal interior configuration on before I start cutting and hammering. Like everyone else, the issue of flotation is one of the gnarly issues on how best to handle. Slice it, dice it, cover with plastic, seal it in place under treated plywood, and a thousand other other permutations are out there. No shortage of ways to address.

Well yesterday, in a Home Depot parking lot I saw a gent with a modded Johnboat, so I sauntered over to see if I might learn anything.

One of his mods was elegant in its simplicity: He had taken the thick orange insulation (now flotation) material used in house construction, and cut it to size to fit over the floor area between the benches. He sat it right on top of the thwarts or stringers. No plywood or anything on top of it or below. He then carpeted it (using contact cement) and secured it into place using aluminum angle iron. He had had it on there for a while and it showed no signs of excess rubbing or wear. It was firm and had very little give. And with the carpeting on top was quiet. How practical!

It opened my eyes, for sure. Thought I'd share.

Other than not knowing if the foam is open cell or closed cell I can't say if it's a good choice. In order for the foam to float a swamped boat it must be held in the boat so it absolutely can not break free. If it were to come free the foam will float while your boat sinks.
Never use pressure treated wood on an aluminum boat.

I think I replied in another post as to what I used on my 19' Alumaweld for floation which are pool noodles from the Dollar store.
I read up on various material used and for me this is what I used.

I think expanding foam in a water tight compartment is the ticket. It is rigid and adheres to what you put it in. You need to be cognizant of what formulation you use also. Not all are non-absorbing.

Next to your hull it is the most important part of your boat.

Marine grade (blue?) foam can be purchased in thick sheets that can be used for sealing into a bunk. If you took this road, you should make sure the bunk is structurally sound and sealed well.

Seon said:

I think I replied in another post as to what I used on my 19' Alumaweld for floation which are pool noodles from the Dollar store.
I read up on various material used and for me this is what I used.

Click to expand...

Be careful. A guy on another forum did a test using pool noodles & they didn't have much floatation when it came to keeping a swamped boat floating.

Most people I've come into contact with us the blue &/or pink sheet foam from the big box stores.

SmallmouthFool said:

He had taken the thick orange insulation (now flotation) material used in house construction, and cut it to size to fit over the floor area between the benches. He sat it right on top of the thwarts or stringers. No plywood or anything on top of it or below. He then carpeted it (using contact cement) and secured it into place using aluminum angle iron. He had had it on there for a while and it showed no signs of excess rubbing or wear. It was firm and had very little give.

Click to expand...

You wouldn't by chance have taken any pictures or gotten the specs on that foam? Sounds like a good solution to me, as long as it's closed cell foam and held in place well.

As I said in another recent post, I think the trick is to keep your foam from sitting in water over a long period of time (closed cell or not, water will eventually break it down and saturate it). It sounds like this method would keep it off the bottom of the boat and allow the water to flow freely beneath it.