additive to make polyester resin more flexible or less brittle?

Discussion in 'Boatbuilding' started by souljour2000, Nov 25, 2012.

  1. souljour2000
    Joined: Aug 2009
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    souljour2000 Senior Member

    Hi guys...Am wondering if there is way to make plain old boatyard polyester resin more flexible or less brittle as it were...Am curious if there is an additive say like a silicone that could help....have readabout isopthalmic resins or additives..also know vinylester resins are more flexible and heard about this additive......Silmar 628 by interplastics..... but thats the extent of my research thus far...If there's a choice I'd prefer to find an additive as I have a fair bit of plain polyester boat resin on hand...
     
  2. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    I put a lot of fiberglass cloth into mine - it improves the Polyester resin greatly :)
     
  3. pauloman
    Joined: Jun 2010
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    pauloman Epoxy Vendor

    it can an is done with epoxy resin, don't know about polyester resin. In fact, you can rank the key epoxy brands/products in terms of brittleness.

    paul oman - progressive epoxy polymers
     
  4. souljour2000
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    souljour2000 Senior Member

    yeah...talking polyster resin...i know epoxy is alot more flexible or less brittle but it cost $$$ compared to poly resin..I will try to go easy on the resin and decrease the resin to cloth ratio...as RWatson suggests..that is so simple but profound and I have been a notorious resin waster up to now..time to up my game..
     
  5. Frosty

    Frosty Previous Member

    How flexible do you want it --what are you doing.
     
  6. souljour2000
    Joined: Aug 2009
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    souljour2000 Senior Member

    thinking of repairing some soft spots in the balsa-core deck...previous guy was doing the hole-drilling thing for those areas...I'd prefer to cut out panels as needed and re-glass them back in with close cell foam and bi-axial but I need to do more research..maybe hole drilling is the way to go...
     
  7. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    There are high flex additives for polyester, all they are is a base resin that won't fully cure, resulting in more flex. These resins have poor physical properties along with poor water and UV resistance, so the more you add the weaker the resin becomes.

    I'm not sure who may sell one right now, but they are out there. Call Composites One, they should be able to help you.
     
  8. petereng
    Joined: Jan 2008
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    petereng Senior Member

    ;)Yes - Use 0.1% polyester and 99.9% epoxy. Epoxy is has great strength and flexibility. Peter S
     
  9. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    There are polyesters with more than 100% strain, so it can be done. Used for roofing.

    But I feel you are thinking too much about it. Just use what is available. 99% of the damage is bad workmanship or mishaps, not choice of materials.
     
  10. souljour2000
    Joined: Aug 2009
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    souljour2000 Senior Member

    There's alot of info on the different approaches to re-coring soft spots in a deck...much is documented online and in how-to videos...and in the archives of this fine website.
    I am looking at a major structural repair where the windlass ripped out when P/O left the boat moored with anchor chain on the windlass in late winter and went out of state...I plan to re-build the foredeck as robust as possible but with materials I have on hand and boatyard resin.
    There's alot of glasswork in the days ahead and so I am content to go the cheap route with resin...though wood re-enforcement members will be teak and marine ply or maybe some cypress if I can find some..
     
  11. tunnels

    tunnels Previous Member

    to do a repair like fixing the windlass the glass really is to just repair the dammage but to stop it pulling out like it did before it has to have strength built under the deck and well spread out over a wide area . Make a laminated beam from solid wood and ply epoxyed together so the fixing bolts to hold the unit go all the way through with ss plates as washers the repaired glass should not have to take any of the loads its basicly there to fill the hole and be water proof , but built like it was before . Remember in the back of your mind you will only get one chance to do this repair if it pulles out again you will have a major rebuild of the whole thing right out to the hull so leave nothing to chance !!:rolleyes::D.
     

  12. souljour2000
    Joined: Aug 2009
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    souljour2000 Senior Member

    Well said Tunnels...I have yet to sketch up anything...just banging around ideas in my head as I am wont to do...I am leaning towards laminating some "knees" into the shoulders or sides of the hull just below the rails...which will have tied into them the teak 1x4 curved seat slats I have.... (parts of an old teak gazebo that I salvaged from a dumpster). These slats have a weak arc section scarfed on (a crown section sort of) to make their original curves but when that is broken off leaves a solid extrusion of teak that is wide at the ends due to the scarf-break and thin in the middle...allowing tabbing into new ceiling/deck etc...the extra weight should be manageable..but epoxy is probably be "the way and the light" for this.., thus still leaving the several soft deck areas in need of re-core for my cheap side...
     
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