Expanding floatation foam. How much do I need?

Discussion in 'Boat Repair Help' started by spoonfish, Jan 11, 2007.

  1. spoonfish

    spoonfish New Member

    Messages:
    3,780
    State:
    Warsaw, Mo.
    I'm replacing the floor in my old tri-hull boat. After useing the grinder to cut all the rusted screw heads off the plywood I finally have it all removed.
    My stringers all look good but I would like to fill between them all with floatation before I add a new floor back to it.
    I see there is 2 lb. density and also 4 lb. density foam. If I were to use the 2 lb. does anyone know aprox. how much I will need to order to cover a area aprox. 9 feet long by 6 feet wide by 12 inchs deep?
    Appreciate any ideas.
     
  2. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Put that question to the people that make/sell the foam. Chances are you'll have to shave it down after it cures.
     

  3. spoonfish

    spoonfish New Member

    Messages:
    3,780
    State:
    Warsaw, Mo.
    Thanks Bob;
    I've found a couple of places that sell it but they don't state how many cu. feet ect. the stuff will cover. Thought maybe some of you guys may have known of hand.
     
  4. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    The reasons many dont state the yield is because air temperature dictates the yield.
    It also can vary from manufacturer to manufacturer and the tests they conduct themselves in an ideal enviroment.

    One word of caution. Be very careful about pouring this stuff into compartments without an adequate blow hole. It will bust a boat completely apart!
    I pour in small batches using dixie cups. Let it expand then mix another batch.
    As Bob said it will more then likely go above your stringers and need trimming. Thats what I like it to do that way there are no voids to hold puddled water that may get under the sole.
    Pour one section at the time. Trim that section and throw the trimmings in the next section and pour that section.
    Use a handsaw or fine wire to trim.

    A cubic foot of water weighs 62 pounds. 2 pound foam weighs 2 pounds per cubic foot meaning each 2 gallon kit produces 480 pounds of bouyancy.

    A 2 gallon kit (1 gallon of part A and 1 gallon of part B) will yield up to 8 cubic feet of cured foam.
    6 gallons would make most any boat any of us use unsinkable with 1440 pounds of bouyancy.

    The best thing I like about a bilge completely full of foam is that if you hole the boat the foam will displace any water that would otherwise enter the boat through the hole. You would have to completely penetrate the foam and the sole to take on water.
    Be sure to put some PVC pipes in the bilge that you can use later for wiring or whatever. Glue them down with some 5200 so they dont float up out of the foam. Or you could spot weld them in place with small applications of foam prior to the big foaming job.
     
  5. spoonfish

    spoonfish New Member

    Messages:
    3,780
    State:
    Warsaw, Mo.
    Good post Mark, thank you I figured if anyone knew you would. Thank you for the tip on pouring it also...:0a31:
    I did get a response from one manufacture and here is what they said.

    A 2 gal. kit of foam will make 8 to 10 cubic feet of foam depending on temp. ( a cubic foot is 1728 cubic inches.). The higher the temp., the more expansion.
     
  6. AwShucks

    AwShucks New Member

    Messages:
    4,532
    State:
    Guthrie, Oklaho
    Okay, so educate me. If I were to pour a specified quantity of foam at 70 degrees and obtained 7 cu feet of foam, and poured the same amount of foam at 90 degrees and obtained 8 cu feet of foam.... which would have the greater flotation value? Or, would it be the same? Seems like the higher temperature with the greates yiedl would provide the most flotation... but does it?
     
  7. spoonfish

    spoonfish New Member

    Messages:
    3,780
    State:
    Warsaw, Mo.
    Good question Lawerance. All I know is thats it's 20 degrees out right now so its going to be a while before I do any pouring.

    Is there a minimum outside temperature I should wait for to pour it?
     
  8. cat tamer

    cat tamer New Member

    Messages:
    694
    State:
    MO
    Mark, I hope everyone appreciates the amount of knowledge and info that you add to the BOC, if I see a post by you then I know it's worth reading.
    thank you.
     
  9. brad kilpatrick

    brad kilpatrick New Member

    Messages:
    2,666
    State:
    Kansas City

    Amen....I couldn't have said it better Myself!!!
     
  10. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Good question.
    2 pound foam is 2 pounds per cubic foot whatever temperature you mix it.
    Temperature is effecting the reaction between two chemicals. This happens in number of different ways in many chemical coumpounds like Epoxies, Concrete products, polyester, or vinylester resins.


    The worst thing is that if you mix at a low temperature you are essentially throwing money out the window.

    This is why I am planning to climate control my entire shop.
    Waiting for temperature to rise or fall to work on a boat is wasting alot of time.
    I want to be able to build any time of the day in any part of the year.
    My dream is to one day retire and bang out a few boats a year from 10-20 feet in length while keeping a larger ongoing project up to 28 feet.
    And of course I'll take time to hit the Wooden boat shows up and down the east coast and maybe winning a ribbon or two.

    Maybe at some point I'll be able to attend one the premier boat building schools like those found in Maine and Conneticut and tutor under some of the best in the business.
    My boat building hero ( hero because he did what I want to do) died a few months ago. Ellis Rowe was a native of North Carolina born to a commercial fishing family that went way back in the business. He left home to join the Navy. While in the navy he picked up boat building as a hobby.
    After he left the navy he moved to Maine and worked in a yacht yard or two doing finishing work on yachts. After 2 years or so he started building boats using all types of methods but mainly traditional methods. He was a contributor to Wooden Boat magazine and often taught at the Wooden Boat School.
    Ellis was 59.
    His boat shop was in a large traditional barn.

    I was stunned to read it in Wooden Boat's section entitled "Over the bar".
    Their obituary column.
     
  11. vllyby

    vllyby New Member

    Messages:
    1
    State:
    iowa
    I also replaced my floor in my 1974 lund. I found several local sources for the foam but no instruction, at a cost of about 300.00. I was close to the lund factory in minnesota, I called them and they did the entire boat for 60.00. They also did while I waited. If the manufacturer of your boat was close enough it might be worth a call. vllyby
     
  12. jtrew

    jtrew New Member

    Messages:
    4,404
    State:
    Little Rock, AR
    Lawrence, if an area of size, say two cubic feet, remains empty, or is filled with foam, balsa wood, or lead, it will displace two cubic feet of water, which weighs about 125#. The amount of useable floatation is that minus the weight of whatever is within the two cubic feet. Obviously, lead will weigh more than water, and you get a minus floatation. The weight per cubic foot of foam has to do with the density of the foam; low density foam will weigh a little less, but is more easily 'squashed'. Since we're talking about filling in areas below or behind plywood, the density doesn't really matter; you don't need strength, and a difference of a couple of pounds of useable floatation per cubic foot doesn't really matter either. On the other hand, getting 10 cubic feet for the same price as 8 cubic feet sounds to me like you're getting 25% free.
     
  13. SkipEye

    SkipEye Well-Known Member

    Messages:
    7,525
    State:
    Winfield, MO
    Name:
    Darryl
    Put a can in one ear and see how many cans you need before it comes out the other ear Troy. That should approximate the void that you need to fill on the boat.:tounge_out:

    Dang Westies, ya gotta teach them everything!

    Well........ 'cept Troy did catch that measly little 88+ pounder this year, so maybe he got lucky on that at least.:roll_eyes: