How many layers of material will it take?

Discussion in 'Fiberglass and Composite Boat Building' started by Bigoledude, Aug 4, 2010.

  1. Bigoledude
    Joined: Aug 2010
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    Location: Chalmette, LA mostly hot. Sometimes 14 feet unde

    Bigoledude New Member

    If we must build our pontoons for our houseboat, we will probably choose to use fiberglass. My intension is to have the pontoons designed with the basic shape of a jon-boat with a top, 30 to 40 feet long.

    They would have a bulkhead every 6-feet. The top and bottom would be 3/8-inch to 1/2-inch thick. The sides would be 1/4-inch thick.

    An online vendor told me to use two materials. He said that 1 1/2oz mat and a combo product of 1 1/2oz mat and 24oz woven roving would make a solid pontoon.

    How thick would two layers of the two products come to?

    How many layers of material would it take to achieve 1/4-inch thickness and, how many for 3/8-inch?

    Is there a better choice of materials to use? How many layers would it take to produce my desired thickneses?
     
  2. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    I am not good at imperial, but 1 1/2 oz mat equals 450 grams (correct me if I am wrong) which will give approx 1mm when hand laminated.

    24 oz woven roving is 600 grams/m2?? Then approx 0,8mm.

    1/4 inch is 6,35mm, 3/8 inch is 9.5mm, so you can do the math...

    Is there a better choice? Probably not, or the combo material could be skipped if it is expensive. CSM and Woven roving are (still) cheap.
     
  3. tunnels

    tunnels Previous Member

    24oz roving is close to 820grams in real measurements
    Im a bit like you , find it hard to think in imperial any more .
    Its easyer to find a roving with a csm P matt already stitched to the back of it and then you can lay the material much quicker and better . 2x 450csm P matt to start and the the rest rovmatt (as we call it here ) with the csm facing up not down and carry o the same till its finished all the required layers !!

    Anyone know why i always suggest P matt for the csm layer and not E matt ???:confused:
     
  4. tinhorn
    Joined: Jan 2008
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    Location: Massachusetts South Shore.

    tinhorn Senior Member

    Nope. But I want to point out that if you're facing roving to roving, you should slip some mat in between.
     
  5. tunnels

    tunnels Previous Member

    The rovematt we have has a 225 gram of csm on one side only , stitched on !!!!so you always had csm between layers , wets out nicely and saves time ! .:p

    Ok differant between p matt and e matt is the binder used to hold it all together . E matt has a emussion type binder the breaks down when the resin soaks the matt , trouble being that if the resin goes off and gells to quickly then the dinder may not have had time to dissolve 100% so the glass is not wet out properly . This can be and is bad news as the first layer of glass behind the gelcoat even if you are using Vinylester resin as a barrier and is still more likely to get osmosis !!!
    P matt has a sprinkling of powdered resin as its made and then put through a oven that melts the powder and so binds the glass together . It does not have to dissolve in the resin and there for if you have a quick brew then it is far less likely to get Osmosis .
    P matt also wets out much quicker and better than e matt and in some situations of multi layers of csm it gives a slightly strong lay up !
    In industrial glassing we always used P matt and glass tissue ,also continuous strand matt as well , terrible stuff to use but was there for a purpose when making high pressure acid pipes and tanks etc . :D


    :p :p :D :)
     
  6. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    just to add: p= powder bound, e = emulsion bound.

    Some factories like emulsion bound, as when working the dry material (cutting, tearing) there is far less material (glass fibers, binders) to be ejected into the air.

    Water resistance of powder bound is higher, indeed.
     
  7. tunnels

    tunnels Previous Member

    A friend used to have a factory and made csm and woven matt, plus all kinds of unimatts incombination with other glasses , i used to use all the differant products he made , he'd even make special runs as long as he was given a couple of days warning . The emolssion used was almost like PVA glue watered down so it would go through a spray gun . Its never to late in life to learn new things !!
    :confused: :D :p :p
     
  8. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Maybe this will help....( From Ken Hankisons book " Fiberglass Boatbuilding For Amateurs" at Glen-L Marine)
    [​IMG]
     
    1 person likes this.
  9. Wynand N
    Joined: Oct 2004
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    Location: South Africa

    Wynand N Retired Steelboatbuilder

    Still regret the day I gave my copy of this excellent book away to an "old" GRP boat builder....
     
  10. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    He dropped out of the boat thing for a number of years and now is back. With a new wife. The Dog. (I mean HIM, not her. Certainly not her.)

    [​IMG]
     

  11. GG
    Joined: Jan 2008
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    Location: MICH

    GG offshore artie

    Personally i would go with 2 layers of #1708 and bag it because bagging will give you the advantage of having two layers of glass being almost as thick as one and beside's woven roving is so old school as far as fabric or material goes .
     
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