Diab H80 for flooring

Discussion in 'Materials' started by curtis73, May 7, 2011.

  1. curtis73
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    curtis73 Junior Member

    I'm re-doing the floors AGAIN on my boat. I use this boat a lot year-round; fishing, rescue support, utility, watersports, etc. I'm tired of replacing plywood. Its a 1983 Baja 19' bowrider and this will be its 5th floor. (and its third engine, third outdrive, and second gimbal housing... but that's a different thread ;))

    I've been doing a lot of research: DIY foam core laminated with glass, FRP bar grate laminated with FRP sheet, foam filling the floor and skinning with 1/8" sheet... but I read up on the Diab H80 stuff and it has me curious.

    What should I skin it with? How much support do I need to give it? How far can it span? How thick should I go? Special glue to laminate, or just some West Systems epoxy?

    Here is a super quick snapshot of the cabin floor along with some drawing that I thought might be adequate support. I would also be replacing the floor stringers with a non-rot material... suggestions for that?
     

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  2. rwatson
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    rwatson Senior Member

    If you are wearing out plywood floors, FG doesnt appear to be the answer. Maybe you need aluminium checker plate. I am assuming you had fibreglass over the plywood already ?

    H80 is just lightweight plywood, and once you break the FG skin, it will turn to talcum powder under load, where at least Plywood is fairly robust for a decent depth.
     
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  3. curtis73
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    curtis73 Junior Member

    The last floor in this boat was 1/2" ply with epoxy, then a random mat floated with another layer of epoxy, then a weave mat with another two layers of epoxy to fair it out. The bottom and edges received one layer of weave set in epoxy. It doesn't take long for it to develop fissures: dropping an anchor, flexing from a seat pedestal, etc. Then the wood starts to rot and you're left with a rotten substrate.

    Aluminum plate would not only add a LOT of weight, but it doesn't solve the substrate issue. Thin aluminum that is stretched over rotten wood doesn't do me any good.

    Put it this way... I won't be using wood of ANY kind as a substrate for my floor. Period. Never again, ever. Ain't gonna happen :)
     
  4. gonzo
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    gonzo Senior Member

    I've never seen a floor deteriorate so fast; not even on commercial fishing boats. There must be some other problem there.
     
  5. curtis73
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    curtis73 Junior Member

    Well I use my boat heavily. June July and August it is used about 6-8 hours a day and year round it gets used at least 3-4 days a week; anchors, fishing, rescue support... it gets beat.

    Is it so odd that I want a better flooring material? Everyone keeps suggesting wood. I don't want wood. I agree that its fine, but the opportunity to shed weight and get a rot-proof material is something I'd like to explore
     
  6. gonzo
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    gonzo Senior Member

    You'll be hard put to find a material that is lighter for its weight than wood. A heavier sheathing where the anchor and other gear causes chafing can solve your problems. A fiberglass over plywood deck on a commercial fishing boat will last over a decade.
     
  7. curtis73
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    curtis73 Junior Member

    That's my issue... I don't want it to last just a decade. I want it to last two decades... or more. There is so much labor involved with replacing a floor I'd rather do it with better material and have it last longer.

    The whole thing (once installed) will be topcoated with Rhino liner (or similar) so I'm not concerned about chafing as much as I am the substrate just rotting away if water intrusion happens.

    The other thing that will chap my arse is that if I spend hundreds of dollars on a textured liner and the wood rots in 5 years I'll be seriously ticked.

    Weight is one of the things that drew me to the H80 and other structural foams. Even with sheathing, epoxy, topcoats, etc, the structural foam idea (rough calculations) will save me anywhere from 20-80 lbs... especially considering the heft of what I would have to do to a sheet of 1/2" ply to make it last as long. Weight savings isn't my primary goal, but its a nice perk.

    I very much value your opinions, but putting wood back in this boat for me is just something I can't stomach. I agree that its a wonderful value and a fine choice... but I want better. Imagine you had a trim pump that kept dying on you every few years and you kept going back and buying the same brand over and over. Eventually you would look for another, better brand to replace it and be done with it, right? That's where I am with my boat.
     
  8. rwatson
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    rwatson Senior Member

    Thanks for the details, I can picture your situation a bit better now.

    The Diab is not going so solve much, except not rot when the water gets in.
    It wont help much with longevity by the sounds of it, as your problem is breakdown of the surface. You are only using one layer of woven cloth, and a lot of CSM. Maybe you need a top layer of Dynel - that is the only really tough fabric.

    My first impression for the least expensive longterm solution is to use plywood, but this time top it off with very thin checkerplate aluminium (2-3 mm)- not the heavy stuff. I would paint the plywood with one of the commercial bitumus waterproof coatings, and then apply the aluminium on it while still tacky, with as few through fastenings as possible.

    If you built a Diab sandwich, you are going to need something really tough on top anyway, like aluminium or even steel. You could even do a sandwich of aluminium (thicker on top, light gauge on the bottom) epoxied or glued to the H80, like they do in planes and warship superstructure.

    The only other option, that you would want to get some engineering analysis done first, is to use steel alone. Weight is a big issue as you said, and I have no idea what effect on your stability, but it wouldnt last 2 decades.
     
  9. Steve W
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    Steve W Senior Member

    While i agree with the others that its tough to beat plywood for strength to weight you have made it clear you wont go that route again so my suggestion is to use Coosa board with glass/epoxy on both sides and then your spray in bedliner on the top, i would use the 26lb density coosa and you will end up with a sole that is similar in weight to plywood but no possibility of water absorbsion or rot,this is the perfect application for the stuff. Do not use a lighter foam like the H80,you will destroy it.
    Steve.
     
  10. curtis73
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    curtis73 Junior Member

    Ok... thanks for the pointers.

    Would it help if I skinned it with something a bit more hefty than just glass/epoxy? Like a 1/8" sheet of FRP? Heavier, I know, but durability is important to me. How thick should the coosa be?

    Can you (or anyone) help me out with what the manufacturers specs mean so I can understand them? Things like stretch modulus, yield percentage, etc?
     
  11. rwatson
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    rwatson Senior Member

    yes - thats what I have been saying - you need tougher top surface. 1/8" FRP isnt particularly tough - as you have found out, thats about what you already had.

    Do the experiment yourself. Lay up a 1 ft x 3 ft section of FRP, 1/8", and then lay up another test piece using "Dynel" or whatever its marketed under near you.

    Glue a brick to each piece, and tow it (Dynel face down) behind a car for a kilometre.

    Buy a block of Coosa - and do the same thing.

    Thats all the testing you need to do - the time/money cost ot testing is way cheaper than making a wrong call for the whole deck.



    The manufacturers often have helpfull people on staff that would be happy to discuss your problem.

    Also, Plenty of stuff on the internet
    http://www.engineeringtoolbox.com/young-modulus-d_417.html

    "Young's modulus can be used to predict the elongation or compression of an object as long as the stress is less than the yield strength of the material."

    http://en.wikipedia.org/wiki/Young's_modulus

    "It is a measure of the stiffness of an elastic material and is a quantity used to characterize materials. It can be experimentally determined from the slope of a stress-strain curve created during tensile tests conducted on a sample of the material.

    It is also commonly, but incorrectly, called the elastic modulus or modulus of elasticity, because Young's modulus is the most common elastic modulus used, but there are other elastic moduli measured, too, such as the bulk modulus and the shear modulus."


    I always found it easier to buy a bit of "what looks/sounds right" and test the piece myself. Numbers dont always give the full story.
     
  12. curtis73
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    curtis73 Junior Member

    How thick should the coosa be?
     
  13. curtis73
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    curtis73 Junior Member

    I think my other post got lost... Thank you for the recommendations. I think I'll skip the towing behind the car part... Police frown on it :)
     
  14. Steve W
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    Steve W Senior Member

    Curtis, if 1/2" ply was stiff enough it would probably be ok for coosa also, 3/4" would of course be stiffer if required assuming the same laminate.
    Steve.
     

  15. tunnels

    tunnels Previous Member

    For a wear resistent floor use silica sand and carborundum powder mixed in with your resin or gel coat for the top coat on you floor !!
    The two combined are almost impossible to wear through Is used iindustrial aplications over concrete to stop wear and have seen floor that have been down for a long time , like years !:D
     
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