Resin only on wood or must have cloth?

Discussion in 'Fiberglass and Composite Boat Building' started by Skywoolf, Aug 29, 2008.

  1. Skywoolf
    Joined: Aug 2008
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    Location: Lantau, Hong Kong and Davao Philippines

    Skywoolf Junior Member

    I have almost finished making a T-Top with hard top for my center console.

    It has a stainless steel frame with a marine ply top.

    I need to fiberglass it to give it strength and of course to waterproof it.

    It is almost strong enough without fiberglass.

    My question is - How much difference will fiberglass cloth make to the strength? Is epoxy resin likely to crack and break if there is no cloth.

    I realize nobody can say if my particular project needs the cloth but I am looking for general advice on how much difference the cloth is likely to make. I need to keep the weight down as much as possible and adding cloth would of course mean a lot more resin. Maybe cloth on one side is enough, maybe it must be both sides, maybe none.
     
  2. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    A lot of people can say .... use cloth, even its very fine.

    Epoxy without cloth tends to crack and buckle especially on wood.

    You could glass the exterior, and varnish the interior successfully, or 'encapuslate' (Pars favourite word) the whole deal to keep moisture right out. Encapsulation also increases strength with minimum weight.

    Its actually easier to get a uniform layer of epoxy on the timber with cloth, than without.

    If you paint epoxy by itself the thickness will vary with the brushstrokes. If you lay a light cloth down, squeegee the epoxy on, the thickness will be the uniform thickness of the cloth. Then before it goes right off, lay another light coat of epoxy over and you can be sure that you get a proper uniform layer of protection.

    Adding cloth does not add weight. Cloth displaces an equivalent weight of epoxy, so there is no weight increase for a given thickness. The strength and longevity is vastly increased with cloth though.
     
  3. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    I concur with rwatson.
    Cloth is not terribly expensive and even a thin layer of it will make a substantial difference to the durability and strength of the thing.
    Fully encapsulating the plywood part in glass strikes me as a good idea. I would suggest laying the epoxy down first and allowing it to soak into the plywood for a few minutes, then squeegeeing the cloth into the epoxy- I have found it easier to work all those tiny little air bubbles out with this method than with the resin-on-top procedure (and the epoxy soaks into the ply a little before the glass is laid, thus the wood doesn't wick epoxy out of the glass), even though the cloth is a little more awkward to work with once it's wet. That's largely a matter of personal preference though.
     
  4. Skywoolf
    Joined: Aug 2008
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    Location: Lantau, Hong Kong and Davao Philippines

    Skywoolf Junior Member

    Thanks guys.

    I was more concerned about weight and just being lazy because it would be easier without cloth but now I am sure I will use thin cloth on both sides.

    I already have various cloths so I will just use the lightest.
     
  5. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    Weigh the glass in your arms----- a piece to cover your top weighs what per square yard?
    So don't use the lightest glass if, for another measly five pounds, you could go with 10 oz cloth and have real protection.
    You'll use more epoxy, yes, but not so much that the weight will be a concern.
    There is a practical comprimise, I realize, in every boat, in terms of reducing weight to achieve a certain performance level, BUT... a good bit of advice would be to consider that the outer skin of your boat protects the whole tonnage within, and therefore small weight increases ON THE SURFACE can have far more value than weight increases down below (like interior trim, parts and pieces). Even shopping around for, say spiral cell batteries at 20% less weight per amp makes better sense. Or using a high strength anchor chain one size down but equal in breaking strength to the larger size.
    Just my two cents.

    Alan
     
  6. Skywoolf
    Joined: Aug 2008
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    Location: Lantau, Hong Kong and Davao Philippines

    Skywoolf Junior Member

    I just started with a couple of coats of resin to seal the wood and realized I have extremely fine cloth and very heavy cloth so I need to find a supplier to get more anyway.

    What I have came with the boat.

    It is intended as a lightweight top deck (T-Top)with just a small area strong enough to stand or sit but of course it has to be strong enough to withstand pounding waves and the occasional idiot who will try to walk on the non re-enforced areas.

    I don't worry so much about weight low down at main deck level (water level or below) as it will mostly increase stability but a heavy top deck 6 feet above the main deck could be a real problem.
     
  7. mongo75
    Joined: Aug 2007
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    Location: Orange County California

    mongo75 Senior Member

    Hell, I'm glassing my entire boat topsides (glass hull, wood everything else) exterior in 1708- am I crazy LOL?? Then again being a Marine I think I'm just trying to build a tank.......
     
  8. Skywoolf
    Joined: Aug 2008
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    Location: Lantau, Hong Kong and Davao Philippines

    Skywoolf Junior Member

    As long as it doesn't get top heavy or just too heavy I would too.

    I can't find suitable fiberglass cloth in the Philippines for my T-Top deck. They only have 20 ounce woven roving, very thick chopped strand and finishing cloth so thin its like cobwebs.

    I will be in Hong Kong tomorrow so I will look for 10 ounce cloth there.
     
  9. the1much
    Joined: Jul 2007
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    Location: maine

    the1much hippie dreams

    i wouldnt let a seagull stand on it if it wasnt made with glass,, or built like a house,, hehe ;)
     
  10. kengrome
    Joined: Jul 2006
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    Location: Gulf Coast USA

    kengrome Senior Member

    You haven't looked very hard then, because Polymer Products has plenty of 6 ounce (200 gsm) plain weave cloth available for sale all the time. Then again if Davao is the only place you've looked and if they don't have a Polymer Products branch there maybe that's why you cannot find any.

    By the way, if you're using locally made marine plywood you don't need any cloth on it anyways because it won't check. It's the fir plywood made in the USA/Canada/Eurpoe that people worry about in terms of checking -- and you won't find any fir plywood here so you're probably worried about something that's never going to be a problem.

    In this case you should probably glass the bottom for additional strength (400gsm biaxial cloth will be best here) and then glass the top for abrasion resistance (with 200gsm plain weave). If you're going to walk up there I might also suggest adding ground rubber to your paint for a nice non-skid surface.

    :)

    What kind of boat is this anyways? Sounds like an American style charter fishing boat to me. Can you post some pictures?
     
  11. Skywoolf
    Joined: Aug 2008
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    Location: Lantau, Hong Kong and Davao Philippines

    Skywoolf Junior Member

    I should have said I can't find any in Davao. We have been to every supplier we can find and no luck. I arrived in Hong Kong today for a few weeks and it will be easy to get here.

    The locally made marine ply that I have found so far is very poor quality. I have to look through a pile of sheets in the shop to find one or two that don't have the outer layer coming off. I need to try to find better quality in future.

    The boat is a 25ft center console. The deck I am making is 8ft front to back and about 7ft wide. The 4ft by 3ft section between the supports, above the console is reinforced to be the only area people will normally stand or sit. The rest is probably strong enough to stand on in calm seas.

    The standing/sitting area will be coated with non-slip coating while the rest will be gloss finish NO STEP area.

    I am thinking to use 8 or 10 ounce on both sides.

    I don't have any good pictures but have added one below.
     

    Attached Files:

  12. naturewaterboy
    Joined: Sep 2006
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    Location: key largo, florida, usa

    naturewaterboy Steel Drum Tuner

    To keep people from walking on the un-reinforced portions of your deck, :idea: save up a lot of beer bottles. Set them onto the uncured resin after you get the cloth on. Wait until the resin cures, then smash all the bottles. You will be left with what we call (here in the USA) a Mexican barb wire fence. :D
     
  13. Skywoolf
    Joined: Aug 2008
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    Location: Lantau, Hong Kong and Davao Philippines

    Skywoolf Junior Member

    Heh heh I think that might be a bit drastic. I will just tell them it is very slippery and they are 6ft above the main deck with nothing much to hold on to.
     
  14. naturewaterboy
    Joined: Sep 2006
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    Location: key largo, florida, usa

    naturewaterboy Steel Drum Tuner

    That will work too - if you can keep everyone away from the rum... :D
     

  15. mongo75
    Joined: Aug 2007
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    Location: Orange County California

    mongo75 Senior Member

    Hey Woolf, I'm not sure how much you're willing to pay for shipping, but I get my stuff ship across the US from www.uscomposites.com chck that site out, they have EVERYTHING!!!
     
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