Urethane Expanding Foam

Discussion in 'Boat Modification Journal' started by DH84, Jul 22, 2008.

  1. DH84

    DH84 New Member

    Messages:
    174
    State:
    Eastern NC
    Ive got a question about foaming an aluminum boat.. now ive used this stuff with great results in fiberglass boat building but i was toying with the idea of removing my floor in my aluminum boat and laying this stuff down between the ribs then putting the aluminum back on top of it.. this would help fill those voids that "bang" when im riding and keep the floor from flexing when i walk on it, just overall make it a tighter boat..

    My question is will there by any adverse chemical reactions with the aluminum and the foam? i wasnt sure how corrosive it might be.. im guessing it will be fine but wanted some input before i took any chances..

    for instance i didnt have a clue about the treated wood ruining aluminum until i read it on here.. makes sense.. but thats some critical information as far as im concerned!
     
  2. metalman

    metalman Well-Known Member

    Messages:
    3,447
    State:
    IN
    Name:
    Winston
    Rob,
    I believe you will be fine to use it. Many aluminum boats have foam flotation as standard from the factory...W
     

  3. Katmandeux

    Katmandeux New Member

    Messages:
    1,618
    State:
    Checotah, Oklahoma
    Rob, this has been discussed quite a bit from time to time. Try doing a search.

    I don't remember anything about chemical reactions, but the general gist of the conversations was that all foams are not suitable for marine use, either because they deteriorate over time and/or they absorb water, becoming quite heavy. You're right to procede with caution.

    For what it's worth, I don't believe I would do it, but many will disagree with that.

    Edit: See? Winston likes the stuff! :)
     
  4. metalman

    metalman Well-Known Member

    Messages:
    3,447
    State:
    IN
    Name:
    Winston
    Rob,
    I guess I took it for granted that you would be using foam that is for marine use...W
     
  5. Stubby

    Stubby New Member

    Messages:
    208
    State:
    Kansas, Ar
    Rob Try this guy at AeroMarine Products in San Diego. John Greer & Associates---John Greer (owner) 877-342-8860. also has a net. WWW.jgreer.com
     
  6. DH84

    DH84 New Member

    Messages:
    174
    State:
    Eastern NC

    well the foam im not worried about, its a closed cell foam for marine use and can actually be submerged for years with little to no absorbtion of water (floating docks etc..) i was just concerned about anything chemical issues related with the aluminum
     
  7. illinois_angler

    illinois_angler Member

    Messages:
    151
    State:
    IL
    Don't waste your money. I don't care which company you get it from the end results will eventually be the same. Water will get trapped and cause a reaction that will cause the aluminum to corrode and it will also waterlog. The end result will be a heavy boat that you'll be able to poke your finger through.
     
  8. illinois_angler

    illinois_angler Member

    Messages:
    151
    State:
    IL
    It will work if not in direct contact with aluminum and/or you aren't putting any pressure to break down the cells.
     
  9. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    I've never seen where it caused problems with aluminum but the only way I would foam below the floor of any boat is if I permanently sealed the floor to the hull.
    For the simple reason if you foam the bottom and water has a way to get around the floor its going to get below the floor and stay there. Closed cell will absorb some water over time if water is trapped around it or on it.
    However if you have a sealed system it aint happening.
    You are correct in strengthening the floor. Going with a foam and some simple egg crate framing you can can go with a thinner floor.
    I believe you can get the foam in densities of 2, 4, 6, and 8 pound.
    2 would be adequate.

    Another advantage to a sealed system. If you take a stump through the hull you aint going to sink. The foam will displace any water by preventing it from getting into the hull.

    I've actually seen a stitch and glue flats boat that took a mangrove stump THROUGH the hull and the hull jerked it out out of the bottom of the flat. He hit it running about 45 MPH.
    He drove the boat about 2 miles to the ramp with a stump sticking out of the bottom of the boat.

    The downside to pouring aluminum. If you hole the aluminum, welding a repair is going to be very difficult and time consuming. The foam will have to be removed from that area.

    Another option is simply egg crating the bottom and sealing each section into individual water tight chambers. If you hole it that one or two chambers affected will fill with water and thats it. Not enough to sink the boat. Again you would have to completely seal the floor to the hull for this to work.
    The biggest problem with a jonboat is sealing the floor into the hull so no water can get below the floor because once it does, it has nowhere to go but sit.
    If I were building a boat I would probally egg crate it and fill the outer crates to floor level with foam and leave the center of the boat open all the way to the stern. Probally a 6 inch wide trough. I would have weep holes cut into the foam filled crates at hull level.
     
  10. DH84

    DH84 New Member

    Messages:
    174
    State:
    Eastern NC
    egg crates... thats an interesting idea. So your saying to lay the crates on the hull inbetween the ribs and then foam on top so the foam doesnt come in direct contact with the aluminum?

    yea i was planning on leaving the center open from bow to stern for a drainage channel, and that giving me somewhere to run some tubing for my wires.

    as for the foam being a bad idea.. it came from the factory with all kinds of foam under the decking anyway... of coarse they just threw pieces in there, and its nothing more then styrofoam blocks like coolers are made from, so its got to be better then that route!
     
  11. illinois_angler

    illinois_angler Member

    Messages:
    151
    State:
    IL
    A fishing buddy had an Xpress that had expandable foam from the factory beneath the floor. There were several soft spots in the floor so he took it to someone to redo the floor. Upon inspection after removing the factory floor and foam, they noticed that it was severely waterlogged and the hull was white where the foam was removed. The aluminum was pitted which looked to be some sort of reaction from the foam. You could actually use a screwdriver and push through the bottom of the boat and in some places the reaction had already caused holes in the hull. This boat was 8 years old, I'm not sure if that makes a difference. It would be difficult to believe that this is the only boat with this type of foam application with this problem.
     
  12. psychomekanik

    psychomekanik New Member

    Messages:
    2,534
    State:
    Illinois
    I attached a picture of the floor of my boat before I pulled it up. I wish I had one of the foam substrate without the wood on it. It has the trough down the middle of it. the trough was made of aluminum beams. and the sides of the trough were filled. the plywood was laid over it and for each compartment there were 2 holes drilled. one for filling and one for venting. they filled them till the foam came out the other side, let it dry and cut the holes flush. It gets wet all the time. when i got it the floor was rotten and the foam was soaked. there is no corrosion, or electrolysis as there is no steel used in the production. electrolysis occurs with dissimiliar metals in contact with each other. wanna see some corrosion? add some different metals to it. attached is a few pic's. one of the original rotted floor, one of the boat stripped down to the floor, and one finished.
     

    Attached Files:

  13. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    I'm going to be bluntly honest and probally piss somebody off but I'm going to say it again.
    If you bought a manufactured boat thinking that everything is as it should be I have some acreage that promise will dry up by the year 2015 for sale cheap.

    I've been into alot of boats below the floor and been under the dash of a many a one and I have yet to see one as it should be including the big names out there. I've owned Ranger. Top of the line and it wasn't all as it should have been.
    Grady White. A name everybody knows. How much you think they pay a laminator or a chopper gun operator? You would laugh. Try 10 bucks an hour.
    They'll cut costs in labor and material and sell your butt on looks and eye candy in a heartbeat.
    Thats not saying the boats are junk, its saying there is a whole lot you dont see and cant see until it fails.
    Ask FWMUD what he found under the floor of his boat.
    It was foam all right and to somebody that dont know their foams it was marine flotation foam. To the trained eye, it was a substitute for flotation foam that had filler thrown it.
    The filler was that green foam you see in flower shops. The same green foam as a kid you had fun poking your fingers in making impressions.
    It held more water then a sham wow. Over half a ton of foam was removed from a 17 foot boat!

    You see why I say what I say about boat manufacturers? You have no clue what you are getting until you go under the dash and under the floor.

    These foams are polyurethanes, so are alot of paints that get painted on aluminum.

    Even if you use the best flotation foam available its only as good as the install.
    I'll bet the farm its not the foam that screwed with the aluminum. It was the failure to seal the sole and water getting into places it couldnt get out of.
    Then you have the aluminum factor. Aluminum isnt a half bad conductor and you've just added water to the inside of the hull.
    All it takes is one of those "mistakes" or "corner cuts" for electrolosis to eat the boat up from the inside out. Just one connection is all it takes.
    Just one skinned wire is all it takes. Just one improper ground is all it takes.
    Just one bad electrical install to the dock at the marina it's tied to.
    Just a river. Yes, moving water carries an electrical charge.

    Any number of things will rot aluminum. I dont think it was the foam, it was the foam install.
    The best rule of thumb with using foam is if water can get to the foam it has to have a way to get away from the foam as well. You cant have a leaky floor and a sealed bilge.
     
  14. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    electrolosis can occur if you have an aluminum boat tied up to a dock. dissimilar metals aren't always the culprit.
    We've had people on this site that instead of running an extra wire to something for a ground used the hull of the boat as the ground. That will eat an aluminum boat up.
    Say you keep your boat tied to a dock in a berth all the time.
    For whatever reason a wire or pipe feeding the dock power becomes broken or is compromised and comes in constant contact with the water.
    It will eat every aluminum boat tied to the dock up.

    If I had aluminum anything I wouldnt berth it a marina. No way no how. It dont take much.


    Rob, when I say eggcrating that is not in the literal sense.
    Egg crating a hull is sectioning off the hull by boxing with plywood, aluminum, or whatever. Say for argument sake you box out the bilge in 18"x18" squares.
    You fill each square with foam. Shave off the foam that rises above your boxing and throw the shavings in the next box and pour it with foam.
    You can cut the excess foam off with a hand saw or a fine wire like a piano wire.

    An aluminum boat is not an ideal candidate for what you want to do. The main reason being is its difficult to seal a wood deck to the sides of the boat.
    You could use caulking but the in mind, boats flex and caulking would be like using bailing wire to hold the alternator on your truck engine. If I did go the caulking route it would be with 20 dollar a tube 3M 5200.
    Fiberglass, composite, and wood boats are easily done with thickened epoxy and glass tape. It will handle the job.
    Aluminum boats are difficult to work with especially if you are trying to convert a bilged boat into a self draining cockpit boat. The only way to effectively attach anything to aluminum hulls is by screwing or welding.
    If it were mine I would just be content in the fact that I had an aluminum boat and if I wanted something different I would need to go with a different boat.
    If you are proficient and have the tools to fabricate aluminum it is a different story.