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  • Who needs foam.

    Im sure this topic has been discussed before but when I searched it I really didnt see anything. Question, is anyone putting foam back in there boats after removing it during a restoration/rebuild? Im not talking about around the fuel tank, I mean under the gunnels and everyplace else for that matter.

    Besides the obvious of helping the boat stay afloat should it capsize any other advantages? Does the risk of the new foam getting saturated like the old foam outweigh any possible advantages?
    1978 Mako 17 Standerd[br]1990 Welcraft 33 Sportfish 2000 14 Polar Craft

  • #2
    Ive considered filling one of the grid compartments on each side but havent committed. My drain paths through the bulkheads would have to be inclosed as I have the bulkheads notched for water to flow. Since removing the inner liner sides and strengthening the gunnels there is no more foam except for at the bow below and around the anchor locker. I think the foam is much better, closed cell that doesnt absorb water now but it can still trap it.

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    • #3
      Why would you leave it out? It provides extra safety and rigidity. All newly built boats under 20 must have foam floatation.

      https://www.boatingmag.com/boats/sinking-boats-safety
      [br]Captain W[br]1970 Mako 19

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      • #4
        First off the newer closed cell foams don't retain water like the early open cell or even early closed cell foams did. So that should allay those fears.

        The foam adds important rigidity to many bulkheads including the hull.

        And lastly, more recently I saw a video of a boat returning in the Jupiter inlet, looked like about a 21-23 Seacraft or similar. He stuffed the nose on a wave and wound up with green water in the boat, it got sideways, and before you knew it it rolled and sank right out from under the guy. Aside from the poor seamanship, had that boat been foam filled he might have lost some gear out over the transom but the boat wouldn't have gone under.

        I'll keep or replace the foam thanks.

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        • #5
          Guys, I only had to watch one Mako video to know that I was going to replace all of my foam. Watch this!

          https://m.youtube.com/watch?t=101s&v=WqLA5DkFe_E
          [br]Captain W[br]1970 Mako 19

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          • #6
            Last summer I removed and replaced all of the wet foam in my 1982 224 from bow to stern. The flotation foam in these hulls is without a doubt a critically important structural component of these hulls. I strongly advise anyone who removes foam from their hulls to put new foam back exactly as it was or even add a little more than it had from the factory. I'd also say that If you are looking to buy a Mako and the foam has been removed and not put back that you walk away or plan on putting it back.

            With the fuel tank coffin and foam removed it is surprising how thin and flexible the fiberglass skin of the hull bottom are. The foam acts as a rigid backer to the fiberglass skin of the running surface. The foam adheres itself to that skin and surrounding structures making everything act as a single unit rather than flexing and breathing as separate structures.

            The foam really creates an I-Beam effect. The surfboards I build out of the same polyurethane foam as used in our boats have absolutely no strength until I put a thin layer of fiberglass cloth and resin over the foam. Likewise the thin fiberglass skin I apply to the foam is as flimsy as a sheet of copier paper in and of itself. Its when you combine the foam and the fiberglass skin and create that I-Beam effect that the surfboard becomes strong enough to support a 200 pound man and endure the crashing waves. Our boats work the exact same way.

            It is also important to know that our Makos are built with no center stringer. Our boats generally are built with two stingers with one being to each side of the fuel tank coffin. The skin of the hull on the center line of the hull really isn't that thick. Do you really want the centerline of the V of your hull to have no foam backing it up if you hit something?

            Without the foam in place you also introduce the possibility of hard spots creating a fracture or hull failure where the flexible running surface skin meets the rigid stringers and strakes. Keep in mind that a day of running even in the most mild of chop means that hull skin would flex against the rigid stringers and strakes thousands and thousands of times. How many times does it take for the hull skin to flex where it meets a stringer before a crack forms? Do you want to find out?

            2-part foam is very inexpensive if you buy it from the right sources. Don't even consider West Marine for the stuff. It only cost me a few hundred dollars to put the foam back in my 224 and I used better, higher density, foam than it had in it from the factory. I forget if it was 4 or 6 gallons of mix that I used.

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            • #7
              I would not suggest removing the foam and not replacing it on an otherwise original hull. On my build with 1 1/2 stringers and bulkheads set in thickened epoxy over 3 layers of 1708 with epoxy plus an additional 2 layers of tabbing this hull is more rigid then it ever was with foam. Flex wont be an issue here however if the boat got swamped that is another story. I will use the two compartments to the sides of my tank platform or the two behind those. The two small compartments in the front corners will also get foam. With just those 4 compartments I will have 10-11 cubic feet of foam plus whats in the bow.


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              • #8
                I'd still foam everything.

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                • #9
                  Good stuff guys, I appreciate the feedback. Makes all the sense in the world. It's there for a reason and the benefits of putting it back far outweighs any potential issues with trapping water.
                  1978 Mako 17 Standerd[br]1990 Welcraft 33 Sportfish 2000 14 Polar Craft

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