Repairing Sub frames in a Polyester Boat

Discussion in 'Fiberglass and Composite Boat Building' started by farjoe, Nov 2, 2007.

  1. farjoe
    Joined: Oct 2003
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    farjoe Senior Member

    I am thinking of buying a 47 foot boat which has extensive damage to its sub frame abkter going aground. The main issue is seperation between sub frame and outer skin.

    Taking the boat to a professional is not financially worthwhile.

    Are ther any suggestions of how this can be done?

    I am told that repairing with epoxy resin is not recommended since the difference in stiffness between epoxy and polyester will cause new stress points. What is the proper way of repairing a polyester hull?

    I have experience building boats half this size but very little experience in repair.

    regards
     
  2. the1much
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    the1much hippie dreams

    how much is too much money?, and how long are you willing to pay and work on it without it being ready for even a rain shower?
     
  3. PAR
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    PAR Yacht Designer/Builder

    Stop listening to those that said epoxy isn't the choice for your boat, they're talking out their butts. Epoxy is the superior product, easily hands down the best and makes the most lasting repair.

    I'm not sure what you mean by sub frame, but I'm assuming you have a boat with a full or partial liner and you have a leak that is entering and living between the two skins.

    The first thing you need to do is get the water out, which may require some well located holes (of course she'll have to be hauled out and on stands) and dry the laminate. You can perform the exterior hull repair as any normal 'glass boat would be. Grind back to solid, undamaged laminate, dramatically taper the edges and layup a new repair with fabric and resin of choice.

    If the liner was bonded to the hull shell then you have bigger issues as it's likely this is part of a structural grid, molded into the liner. Typically you'd have to gain access (yep, probably more holes) from the inside (through the liner), rebond the liner (this is a place where epoxy should be your only consideration) and fill the access holes.

    If professional repairs on a 47' yacht are not "financially worthwhile" then I would strongly advise you not proceed with the purchase. Ownership of a 47' yacht isn't for the "average guy". Expenses for a vessel of that size will be quite surprising. Just the tab on new bottom paint may make you think twice about having her, even if you elect to paint the bottom yourself. Do yourself a favor and have some of the costs priced out. These may include, annual haul outs, winterizing, spring commissioning, bottom painting, slip or mooring fees, topside paint, varnish work, turn up and oil change costs, etc. This is a small, partial list of the many fees associated with the ownership of a fair size yacht, such as the one you're interested in.

    There's no such thing as a cheap 47' yacht. Even a free boat will costs thousands each year, just to keep in working order.
     
  4. Matt.D
    Joined: Oct 2007
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    Matt.D Junior Member

    Hi PAR. it sounds like u know a lot about f glass. could u tell me if u can glass poly over epoxy and if u can glass either to aluminum.
    Sorry farjoe for crashing ur thread.
    Matt
     
  5. the1much
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    the1much hippie dreams

    i think he meant not using epoxy with his poly fiberglass, and not wanting to mix products.every forum says dont use epoxy to patch if your boat is a vinyl ester, or poly. i think he's going by what he's read, not butt-talkers lol ;)
     
  6. the1much
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    the1much hippie dreams

    you cant glass to aluminum,, and NO your NOT suppose to mix your products.. if your boat is poly, use poly, if its epoxy use epoxy. dont take my word for it tho, call and ask your epoxy supplier, he should say whats on his directions , which is no
     
  7. Roly
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    Roly Senior Member

    I have a just built a deck in a female mold (34') and I researched this b4 laying up a polygelcoat/polycsm/epoxytriaxial/balsa/epoxytriaxial laminate.
    I consulted with the Adhesive technologys guru, ( Gougeons Bros NZ counterparts) b4 proceeding.
    It has been done many times before.
    1.No problem except its is a wholly mechanical bond.
    2.Epoxy to polyester not visa versa.
    3.Polyester MUST be 100% cured with no residual styrene,wax,mekp remaining.Preferably aged.Beware of bilge contaiminants-ie diesel
    4.Peelply polyester preferably(new work), or 40grit b4 laminating over.
    Worked for me. Although longevity of gelcoat could be affected because of
    differing physical characteristics.(Yet to be seen)
     
  8. the1much
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    the1much hippie dreams

    wow,,,,everything ive read said no,,nice research :)
    but dont let " its been done many times before" thingy fool ya hehe,, ive seen alot of things done wrong many, many, many times over, some even lasted for years,, till that 1 wave hits just right ;)
     
  9. PAR
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    PAR Yacht Designer/Builder

    Yep, epoxy on polyester, never polyester on epoxy. Yes, you can bond to aluminum (epoxy), but don't ask the parts to flex too much.
     
  10. the1much
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    the1much hippie dreams

    is it that way because poly uses more of a chemical bond instead of mechanical, or visa-versa?,,hehe this prob obvious to everyone but remember,;) i hand lay up 55 footers with no respirator and shoot awl-grip with jus a respirator hahaha :p
     
  11. Roly
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    Roly Senior Member

    Given the right preparation you can combine materials that don't appear to be
    compatible. But for me, using them in a structural application is introducing unnecessary risk. Obviously epoxy has vastly superior adhesive characteristics,
    so for a mechanical bond, ( past the window of air retarded poly to link with the the next poly coat) epoxy is the best choice. Hence all the osmotic repairs using epoxy on aged poly hulls.( *Plus its superior moisture resistance)
    That said I hark back to Prep. and the use in non-structural applications.
    Poly on special prepped epoxy.
    http://www.westsystem.com/ewmag/22/pdf/Ew22_Polyester.pdf
    It can be done.

    I had a female mold,coupled with it mading me nervous so I stuck with PAR's advice.
    Epoxy on poly, as you get the full benefit of epoxy's gluing physic's.
    Make sense?
    (I did peel ply the csm and leave the laminate 6 weeks b4 laminating with epoxy, minimising any contaminents from the fresh poly)
     
  12. Roly
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    Roly Senior Member

    Look after youself better 1much,Styrene ruined my health after 10yrs of exposure.It creeps up onya.:(
    One of my mates red blood count dropped to 1/2 of minimum from isocynates
    so demand a postive air supply.
    Long time dead.
     
  13. Roly
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    Roly Senior Member

    IMHO,correct me someone if I am wrong.....
    Both epoxy and polyester can form chemical bonds to themselves but both have "windows of time" between coats when this will happen effectively. For epoxy, the window is shorter,a matter of hours.Polyester achieves the best inside days and achieves limited chemical bonding over time to the point where epoxy achieves a better "mechanical" bond to polyester than polyester's limited chemical bond would to itself because of polyesters poor adhesive characteristics.
    Geez, clear as mud!
     
  14. the1much
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    the1much hippie dreams

    with poly time i am sure,, and i think its same on epoxy,,within 24 hours of last "layer" you can add another and it will be a chemical bond. after 24 hours you need to sand between layers, thats your mechanical bond
    and my boss wont go for air supply costs too much and i need,,i mean HE needs more money lol ;)
    and after 20 years of sucking poly, you kinda need it to get through the day heh ;)
     

  15. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    For repairing the polyester resin/glass you can repair it with polyester again. Since you cannot laminate the wet fibreglass to the dried fibreglass - it will just delaminate under stress - you have to soften the original area to do the new repairs. I know it's how they do the repairs. Cannot remember what the stuff is called that softens the fibreglass resin, you have to find out from your supplier. Expensive though.
     
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