EPDM Roofing Material as a liner?

Discussion in 'Materials' started by Wavewacker, Oct 12, 2010.

  1. Wavewacker
    Joined: Aug 2010
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    Wavewacker Senior Member

    Hi, cleaning out the garage and found a small left over from a previouse roofing job. It's EPDM roofing a rubber type material that is very tuff stuff. You can't poke a hole in it with anything bigger than a screwdriver....

    It's to be glued down with full coverage. it weighs 1/3 pound per square foot and is .06 thinkness. It's like a rubber sheet and comes in rolls.

    OK, question, could this be used on the inside of a homebuilt boat project, like a sharpie as liner? Seems that if this were properly glued to the hull it would provide additional strength and protection from being holed or any running gash.

    It can be painted, has some insulation qualities and is plyable. Again, very tuff stuff. It's also relative inexpensive.

    Why use it? I'm wanting to cruise the Mississippi, there is no problem going down stream in most any boat. There is a real danger going up stream, all kinds of junk travels with the current, like trees, telephone poles, lumber, etc. So getting hit could be a problem in a small boat. Or, is there a better way?

    Thoughts, comments? Thanks!
     
  2. gonzo
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    gonzo Senior Member

    Do you mean an inside or outside liner? I know the product you are refering to. I don't see it being tougher than planking. I mean, if you hit something hard and sharp enough to puncture planking, the membrane will be ripped too.
     
  3. Wavewacker
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    Wavewacker Senior Member

    Inside the hull, fully glued as it is laid. You can pucture it with a razor knife, you can stab it with a sharp knife, if you tried hitting it with a hammer had enough to get through plywood, I'm sure it won't go through the rubber. What do you think gonzo? It's beginning to sound like you have a realestate construction background too...lol
     
  4. PAR
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    PAR Yacht Designer/Builder

    Rubber membranes used on roofs, such as Ethylene Propylene Diene Monomer (or Terpolymer) isn't especially tough, particularly when it comes to puncture or abrasion. These membranes are rated for light foot traffic and that's about it. In fact, the tapes used for seams and edges is rated better at everything then the actual membrane is. So, it's a novel idea, but not especially practical, sorry.
     
  5. Wavewacker
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    Wavewacker Senior Member

    Thanks PAR. I'm not familiar with the tape as it simply was lapped over and guled. It's lasted now on a very low pitch roof for just over 10 years on a second story bump-out. No one has been walking on it but considering the exposure, I'm very pleased with it as it appears to be in very good condition, no cracks, splits and it doesn't leak. I know this is unconventional thinking.

    I have a strip a couple of feet wide and about six feet long. I don't really have a facility to test it glued to plywood. Toughness is a subjective term I guess. I have experience in hitting rocks in rapids in my area, it's something that you get experience of seeing and feeling without any statistical analysis to apply. Just working with the stuff I can see that such strikes and blows wouldn't puncture or tear it, especially fully glued to plywood. At the low speeds of a small craft, damage is rather limited to a plywood hull, again subjective, but if the hull failed and leaked I see the membrane as a second line of defense. I'm sure it would stretch a bit from the kinds of bashing I have experienced and keep water from entering. I just see it as cheap insurance.

    But, I don't know if the use of this would cause any other problem. I'm not aware of any chemical reaction or negative effects in a boat. If the weight would present a problem, maybe it could be applied only to critical areas. I don't see a weight issue, but I'm not an engineer! Maybe consideration should be applied to an existing design, such as a sharpie at or over 16 feet, say up to 24 feet. Another would be a Striker catamaran, hulls of 24 to 27 feet.

    I'm not 100% sold on this, as to its value. I agree PAR that it is not a structual element, I can just see that if plywood were fully glued to it, that the plywood would crack or split, but would be held somewhat in place instead of breaking off entirely, just from it being glued to a flexible membrane.

    Also, is there a method of improving impact resistance and survivability of smaller boat hulls, considering the debris found in the Mississippi? Fiberglass production boats have been holed, but usually things just glance off or you ride over such obstructions. Is there a better way with plywood, more economical, than just building up fiberglass? Thanks!
     
  6. WickedGood

    WickedGood Guest

    They make a rubber coverd Kayack that is sold commercially.

    Dont see why you could not tack some rummer sheeting onto a wood framework to make a simple cheap hardware store boat.

    [​IMG]



    Hey How does this rep point thing work? yesterday I was Pos 16 and today I'm -16 just about like the weather outside. Its freeking freezing 30 in my yard.
     
  7. PAR
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    PAR Yacht Designer/Builder

    Toughness is certainly quantifiable, Wavewacker. Abrasion resistance, puncture resistance, modulus of rupture, elasticity, compression, etc. all can be measured, evaluated and compared to other common materials.

    In short, if you breach a plywood panel, the force necessary will likely be enough to also breach the membrane. These membranes aren't very good at abrasion. In fact, if an area receiving these materials is speced for a specific amount of foot traffic, the material thickness rises substantially, indicating it's weakness in this regard. Weight is another issue, as this stuff is heavy, considering it's strength and physical attributes.

    I wouldn't consider it on the inside of a hull. You see, in this location (on the inside of a hull) being the planking thickness away from the center of gyration in the entry of an impact, point loading or other "event", you'll want a material like Kevlar for example (or something with similar physical attributes), so you can take advantage of both it's location and puncture resistance, which results in a stiffer, more puncture resistant hull panel. This is engineering 101, using your materials to advantage, so you can save weight by using less for the same strength requirement. This saving translates into less build cost, better preformance and more value for ability per pound.

    So, Wavwacker, don't stop looking for new ideas. In this case EPDM isn't a good choice on the inside of planking just because in this location (inside of the planking) you desire materials that resist elongation and have high elasticity resistance values, which EPDM just can't offer.
     
  8. Petros
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    Petros Senior Member

    You would not want it on the inside of a hull, any tiny voids would trap moisture. Better would be put it on the outside, but it had little to no abrasion resistance. Heavy canvas (or polyester fabric) painted to the hull is used on many smaller boats like canoes and kayaks, this could be used on larger hulls too and would be less costly and hold up better than a EDPM membrane.

    The best place to use such a product would be on the roof of a cabin or even on the deck to water proof it. If you get the type used rated as a walking surface it would be a great, low cost, long lasting deck covering. I has always seemed silly to me that many cabin roofs and hatch frames are bright finished wood. Does anyone think using varnished wood on the roof of a house is a good idea? I think not, but they do it on boats. Using a rated roofing material on the roof and deck of a boat would make much more sense for low maintenance. If I ever build by pocket cruiser I would condsider such a product for the deck and cabin roof.
     

  9. PAR
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    PAR Yacht Designer/Builder

    I agree that varnished decks and cabin roofs aren't really good ideas, but I've also seen these with texture, which works for under foot traction, though looks a little odd.

    EDPM just don't make a lot of sense to me as a waterproofing membrane, when other much more practical, durable products can do so much more.
     
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