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Has anybody thought of or has changed the polystyrene blocks for expandable foam.
I was thinking about doing this on my M as I always find bits of styrene in the stern bilges.

I work with the expandable foam all the time. The problem with it is it sticks with tenacity and is a pain to dig it back out. So if you need access later for mods or wiring, it probably would not be a good choice. In addition the down side to packing an area with expandable foam is you lose the ability for easy inspection to that area. To increase my flotation I have collected chunks of styrene foam from shipping boxes and stuffed them into the extra voids.

Graham Carr

Two issues I see:

1 - Is there a difference in floatation by volume? If it is as good as the stock stuff, then you should be able to get a bit more floatation, as the stuff you get in a spray can from Home Depot would fill voids better than the blocks could... However, if it isn't as bouyant...

2 - Boy, talk about potential for going awry... That spray can stuff can be real messy. If it got on the exposed carpeted internal walls, you could never get it out... You'd have to just cover it up with something... Although, that's an interesting idea... You could smooth that foam stuff all over the walls and use it to "glue" some more appealing fabric or whatever. Then, you'd get added floatation, as well as thermal insulation, and a sweet custom look...

I thought the foam was expanding foam until we got the boat and noticed they were blocks..nice to know..for mods..take em out..do the mod...replace..

The one time you use expanding foam..the next day/week..you WILL need to run wires in that area...guaranteed!

Paul

This this was discussed in a thread I had about building custom coolers in my M . The thought was to use plastic bags to contain the foam . It would still fill the cavity and yet when and if you need to remove it . . .it Should . . be a lot easier to remove as it is NOT sticking to every surface every crack . I have yet to build my coolers however they are still on the list of projects for the up coming season , as is a fold-away Dive platform. Design work is done for both I just need to find "A Round To It" to get them done .

When you get that Dive Platform done, please post a mod... I'd love to see how you do it...

On the contrary the foam does not fill into voids as well as one might think? As I mentioned above I work with this stuff a lot (construction). The problem is as you inject the foam the pressure in the cans is not sufficient enough to force the foam back into the voids. Even though the foam expands, it does not enough to be assured you are getting the same volume. An example of a space that would not fill up would be under the aft berth. You would have to drill small holes to stick the fill tube in. If you do decide to try it, place the foam in small quantities allowing it to expand. Then you can see how it is filling up the back spaces. Wait about an hour or so and add some more. The only place I plan on using it is in the end of the mast after I add some conduit so I can upgrade the wire.

Graham Carr

DLT wrote:When you get that Dive Platform done, please post a mod... I'd love to see how you do it...

I shall do that . It will cost about $200 if you already have the stock boarding ladder from Mac. in place . It will not interfere with the motor and will fold up and out of the way when not needed .

Expanding foam is powerful stuff. Boston Whaler and others who inject it between inner and outer hulls leave those in their heavily reinforced metal molds strongly clamped together. Squirt a little at a time and let it expand before adding more.

There are two types of expanding foam available . One is High Volume / High exerted pressure and the other is Low Volume / Low exerted pressure. I believe we discussed using the low pressure for the reason's stated above . .

Thanks for the input. I would like to find out the comparisons between the two regarding the density and the volume required for equivalent floatation. If I do use the foam,I will place short lengths of electrical conduit pipe with pull through for future wiring.

Caution should be exerted in your selection of foam. some foams can actually absorb water. I believe the foams used in the marine industry today are referred to as 'closed cell' foams and resist ingress of moisture. I once saw an injected type foam being removed from an old wooden dingy and it was a sodden mess. The foam was being removed to repair the water-damage the foam had caused from the inside!

I once used a long tube on the foam spray nozzle to inject foam into inaccessible places (making a male mould of a statue) by injecting a small amount, withdrawing the tube a small amount, wait a minute or two for the foam to expand, inject a bit more and so on... In the end, the male mould was in pretty good shape when released so the foam did a good job.

Both the solid blocks of foam and the spray in expanding foam are "closed cell foam" and will work for flotation at least for awhile, but the quality of flotation is different long term. The solid blocks of foam are produced under more controlled conditions and the air pockets seem to be better isolated from each other. The spray in foam seems to absorb water if left saturated for extended periods of time. I believe this is the problem discribed by Dominic, and I believe it is true of most sprayed in foam.

Caution should be exerted in your selection of foam. some foams can actually absorb water. I believe the foams used in the marine industry today are referred to as 'closed cell' foams and resist ingress of moisture. I once saw an injected type foam being removed from an old wooden dingy and it was a sodden mess. The foam was being removed to repair the water-damage the foam had caused from the inside!

You can see this problem for yourself by creating a small piece of sray foam and holding it under water for a few days with a weight. Try the same experiment with the manufactured block foam.

How much the foam expands also depends on temperature, and this in turn may make some difference in how much it will absorb water. I haven't tested the floation of spray foam that has been expanded more with that has been expanded less (cooler temps).

I've found the kind of foam that pool noodles are made from to be more durable than the block foam that was put into my Mac. Maybe this same type of foam is available in block shaped pieces.