Resin choices

Discussion in 'Boat Design' started by MarkOrge, Jan 12, 2009.

  1. MarkOrge
    Joined: Oct 2008
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    Location: Markham, ON

    MarkOrge Junior Member

    I have access to a 16' hull mould with complimenting top mold that would make a great next bass boat. My question is, without getting exotic $$ should I move up to vinylester resin and, given the three options (polyester, epoxy, vinyl) how do you know when you have to grind between layups?

    I plan to pre-fab the stringers and transom layers to fit the mold before final prep, of course adjusting for thickness after layups, then do 2 or 3 layers of 1708 for the hull (depending on whether or not I use a core material for the hull) then glass in the transom and clamp it, then glass in the stringers, then floor. If I could do all 4 of these steps without grinding that would be very cool.

    I won't get started on choice of core material.....lots of threads on that one....just have no idea on how many layups over how long a period of time before you have to grind.

    Many thanks in advice, what a great site !!

    Mark
     
  2. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Hi Mark,

    I would say that vinylester is worth the extra money over polyester, especially if the boat will be sitting in the water for extended periods. Stronger, less prone to blistering, more durable. As to the individual brands, I can't offer much help there.

    It sounds like you haven't calculated the actual strength requirements yet, and don't appear to have much guidance from the hull's designer on this matter. That's an issue, but you can work around it. Look up Dave Gerr's book "Elements of boat strength" on Amazon or your favourite local bookstore- definitely worth the $30 or so. The methods he describes for calculating hull skin properties, stringer designs, etc. are simple, but are reported to yield good, solid boats that are still reasonably lightweight.

    If you have a good airtight mould, you might be interested in looking at vacuum infusion. It's a bit tricky to get started with, but it's clean, efficient, and you don't need 20 people rushing around spilling resin everywhere to get the layup done before it all sets up. This may or may not be appealing to you, but is at least worth a look.

    I used to think you had to grind the surface away to get a good secondary bond, but that was before my introduction to peel-ply. This stuff is essentially a stiff, tight fabric that you press into the wet resin after the last layer of fibreglass. When it comes time to do the secondary bond, you just rip the peel ply off and it pulls all the contaminants, waxes, etc. with it, leaving a nicely textured, clean surface to bond to. Not expensive at all, and it pays for itself several times over in labour savings.
     
  3. MarkOrge
    Joined: Oct 2008
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    Location: Markham, ON

    MarkOrge Junior Member

    Thanks Marshmat! I am definately going to find that book and use the information from it. My preliminary schedule is based on a previous thread I had and the advice given there - 3 layers of 1708 as opposed to the chop gun and two layers of 18 oz woven roving the original manufacturer used to use. I am going to also look into the vacuum process as I understand there is very little reason why not to. All that is left is to get a decont price tro "rent" this mold.

    FYI the mold/boat is a 16 foot "Marlin" by "Kennedy Boats" here in Markham, Ontario, Canada. At the risk of slandering, I believe it is a copy of a Checkmate.

    Peter Stelter won all kinds of races with this hull, he makes the racing/ski boat version (different top mold) at about 500 pounds. Of course that is a stripped down version of the boat.

    Thanks again,

    mark
     
  4. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    Indeed use peelply to get a good secondary bond.

    Polyester and vinylester both have a good rate of cure at ambient, (especially DPCD resins) so secondary bonds are always a bit tricky, when no sanding or other prep is done.

    I have tested some methods to get a good secondary bond, and here the results:

    -no prep at all (hey, I can try it...)
    Easy to split the laminate with a chisel
    -sanding
    Gives unpredictable results. A thorough sanded piece is OK, but anything but that will give unsatisfactory results.
    -sprinkling with chopped glass
    no use at all... Almost just as easy to split as no prep at all
    -peelply
    I was not able to split the laminate, just could take of slivers.

    Seems pretty clear to me.

    Sanding vs peelply. Moneywise, peelply is just a touch more expensive. Perhaps they are on par if you take into account a cleanup with acetone, power and wear of the sanding machine.
    Timewise peelply is a winner.
     
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  5. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Good peelply fabric can be had for about $2 a square metre; think of how long it would take to sand and solvent scrub each square metre of secondary bond area, plus the cost of the sanding pads etc. ($2 buys about 12 minutes of unskilled labour in Ontario.) It sounds like Herman has compared the various surface prep methods fairly thoroughly and I'm not surprised by his conclusion.
     
  6. MarkOrge
    Joined: Oct 2008
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    Location: Markham, ON

    MarkOrge Junior Member

    Thanks Guys ! I love this forum !!
     
  7. dockdave
    Joined: May 2007
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    Location: long island

    dockdave Junior Member

    I believe you could also go poly, and use unwaxed resin if you desire to build in stages. No wax resin remains tacky for days.
     

  8. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    On this side of the pond almost all resin is waxed, has LSE additive or is a DCPD (pure or blend) which all make for less styrene output.

    About the peelply: A good sanding job is more expensive than peelply. This is true for about any country where workers are paid more then just some beating with a stick and a cup of rice a day...
     
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