Adhesive choices?

Discussion in 'Fiberglass and Composite Boat Building' started by leaky, Sep 28, 2020.

  1. leaky
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    leaky Senior Member

    Below is a picture of the cockpit stringers & framing/"flange" that's not finished on a downeast boat where I want to adhere potentially some spacers and/or the actual deck of the boat. The use of spacers is just a matter of I "found" an extra 3/4 inch I can raise the deck after I got some of the flange glassed in so may take it.

    The deck or spacers (and then the deck to those if I add them) will be coosa laminated w/ a glass & VE resin. If I space it up am just going to cut 5 inch strips of coosa, laminate them with csm (really to keep them clean under there, ie not soaking up dirty moisture) then will glue them down atop the fiberglass T's.

    An additional detail is I am looking to positively seal the deck around three boxes here, basically holes in the bottom of the hull are going to be in these areas, just a feature I added. The fiberglass T's I am glassing to the tops of the stringers positively seal the areas, later I will bolt some other structures to the stringers elsewhere to support the rest of the deck. The deck will also be bedded down in such an adhesive all around.

    I don't want to use epoxy, because I don't want it involved or hiding to cause problems w/ other resins in the event later a repair or modification is needed. The whole boat is a VE & PE resin build, gelcoat etc etc, I don't want something that prevents curing of those products hiding in nooks and crannies, if at all possible anyway.

    I have a couple ideas - #1 3M 5200, generally speaking is permanent and great for creating a seal but I never look at it as 100% permanent, though it may be on a well prepared surface.

    #2 I have considered if I use spacers I could potentially lay a resin rich layer of csm both across the deck "flange" and the spacers, then set them down onto a skin of hull & deck putty.. but I wonder if that flexible bond of 5200 would beat that or if another product makes more sense.

    Thanks in advance!

    20200927_153516.jpg
     
  2. fallguy
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    fallguy Senior Member

    ...with epoxy you use resin thickened with aerosil or cabosil or fumed silica at a volumetric rate of about 2:1 silica to resin
     
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  3. Chris Rogers
    Joined: Apr 2020
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    Chris Rogers Junior Member

    Plexus (methacrylate adhesive) is great for stuff like that because it is tough and spans gaps well and is a nice viscosity for this kind of thing. Lots of production builders use it for bonding structure. Drawbacks are cost and working time - most of the products give you less than an hour of working time. Polyester bonding putty would work too but it's nowhere near as strong or tough.

    Are you planning to fully wrap the Coosa with laminate? If weight isn't a huge issue, you can get pultruded fiberglass flat bar like Strongwell for pretty reasonable price to act as a spacer. Heavy though and may not be available in the right dimensions.
     
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  4. fallguy
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    fallguy Senior Member

    Do not use 5200. It is really slow to bond in this situation and would require about two weeks of leaving weights on the cleats and then weight on the deck two more weeks no work.

    They do sell a fast cure that might work better; still not a fan of the idea.
     
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  5. leaky
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    leaky Senior Member

    Thanks!

    Whenever I think glue, epoxy is the obvious thing, just I have concerns w/ infecting areas with it.

    Have had the smallest bit of epoxy cause headaches before, for instance you decore around a bolt, later down the road the gelcoat won't cure on this one little spot and it becomes a time drain fighting w/ it.

    Actually am going to test a little w/ system III gelmagic to see how bad it messes w/ VE, ie like if a trace amount where seems are will prevent curing. That's the big concern - I have seems between these things that are getting glued down, so I have to tab on top when done and I don't want to switch to epoxy for the rest of the project.

    Thanks on the 5200 - I didn't consider that problem.
     
    Last edited: Sep 28, 2020
  6. leaky
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    leaky Senior Member

    Thanks!

    Is that plexus stuff considered good & permanent? How does it do if you get a little VE/PE resin on it, softened or not really impacted? How does it cleanup?

    An hour would be sufficient, a half hour would probably do it - everything will be ready to go when I put a panel down, just drop it in place & weight it down, really not much to do. Only thing that could suffer if it goes too fast would be cleanup (under the deck) but I will certainly put something down, tape off inside, so any drips are just contained.

    Those are my concerns with hull & deck - it's kinda weak for this sort of thing, but was thinking maybe, at least w/ the spacers, I could get a wet to wet bond if the CSM faces are recent and I set them down in the putty? Or no?

    I am planning to fully wrap the Coosa - probably would run a router around the edges, sand them for a nice smooth arc, and put something simple, like 2 layers of 3/4 CSM around it using VE, wax a final coat of resin or coat w/ PVA, then clean & run a sander on the faces to shave anything bumpy down. This is not a big deal. The Coosa I use would end up scrap, a little VE, and 3 hours of labor but in the world of building boats that is cheap for a last minute change :). In this area a little weight is not that big of a deal but I don't want to add 50 lbs of solid glass material when it will be more like 20 lbs the other way.
     
  7. leaky
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    leaky Senior Member

    I'm thinking maybe I could do something like this - say I glue my panels down w/ epoxy, I get good working time there, no issue.

    Then the seems, any places where I need a barrier between epoxy & VE/PE tabbing, I could possibly shoot some plexus in there over any epoxy that is showing. Would that work?
     
  8. fallguy
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    fallguy Senior Member

    I dunno. I would think you could thicken ve resin same way?
     
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  9. leaky
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    leaky Senior Member

    Actually reached out to this company Arjay today about their products, one is basically a VE bonding compound. Another I think is a slower cure MMA.

    I have attempted another companies VE bonding compound and found it to be malformed garbage, basically a small fiberglass supply house in that case who mixes it themselves and all their home-made products have poor QC. Arjay sells it more as a glue and seems to more likely have a real/reliable product.

    One thing with VE that prevents me from just mixing my own is they come in a zillion formulas all with different properties, really hard to know if what I got is gonna work well how I mix it etc etc. And with VE the curing can be all over the charts, can go from low viscosity to the point where the roller is stuck in the tray within 1 minute on you, I don't have faith in pulling off my own VE glue that well - not for a big area anyway.
     
  10. fallguy
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    fallguy Senior Member

    Then use a one hour epoxy. Silvertip is bulletproof.

    all of the work is subdeck

    go back to your esters for the tape seams on top; epoxy won't mind!
     
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  11. leaky
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    leaky Senior Member

    Thanks - yes I really like Silvertip, that is my go to (liked Duckworks marinepoxy too until they stopped selling it)..

    Trouble is like this diagram, with epoxy I am going to always have a bit of contaminated seam that I will be trying to lay VE over. I am concerned that stupid little edge might make the VE not cure right in spots.

    I am going to perform a test with that system III glue, just basically will lay a few beads down and let them fully cure, prep and see what impact that has on the VE resin. If the resin just cures and doesn't leave some wierd uncured line where it crosses a bead of epoxy then this is a total non issue. If it fails to cure on that spot I will need to solve my adhesive problem another way.

    20200928_181006.jpg
     
  12. fallguy
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    fallguy Senior Member

    Just make sure you have mechanical key.
     
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  13. leaky
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    leaky Senior Member

    Mechanical key? Like a tooth to the surface?
     
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  14. Chris Rogers
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    Chris Rogers Junior Member

    Epoxy would be ok as long as it is fully cured before you get near it with polyester or VE resin. You can definitely grind out the joints and tape them as you show in your sketch - that is a good idea. VE/poly for the taping would be ok with a small amount of fully cured epoxy just in the seam - once it's fully cured it becomes a mechanical-only bond so "tooth" / mechanical key is... key. It's not 100% ideal but a workable plan. Is the deck material a solid panel or cored?

    The Plexus is perfect for this and used this way all the time. It can be laminated over and ground - it's kind of rubbery compared to epoxy but super tough - as strong as epoxy in this situation probably. Only down side is cost - it is probably more expensive per gallon/tube than epoxy.
     

  15. leaky
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    leaky Senior Member

    Thanks again!

    For the small amount of material involved I am definitely not going to split hairs over cost, main concern with the MMA is if I can get one with enough working time.

    Deck will be 3/4 Coosa, laminated on both sides with some form of a 12 or 17 ounce, between 3/4 ounce csm on each side of the woven (ie maybe 1708 w/ 3/4 csm veil, maybe csm then 1700 then csm, maybe 1208 etc)..

    I will probably go at it by cutting my panels, making a rebate of 3/32 around the top edges (enough to take a layer of 1708 and a veil plus a little extra), rounding the edges off so I can glass around them.

    I always laminate panels like this via VE & straight resin until it is saturated, couple coats usually rolled on, then the 1708/equivalent with VE then the final veil with PE.

    I will pva or wax the veil resin, and later fully prep to a 40 grit - basically I want to work with non sticky fully cured and prepped panels. For the hell of it I might gelcoat the bottom where its not sitting on the supports but I won't put gelcoat where I am trying to bond.

    Then after setting the panels down I will fill any gap between panels flush (maybe with MMA if I use epoxy to glue them down, ie seal off the epoxy).. then I will go and tab into that rebate with 1708 & a csm veil, adding layers of 3/4 csm into the valley until its flush, starting with VE resin and final layers of CSM will probably switch to PE (I just like PE better for CSM ).

    A plan anyway (that folks here have helped me with no doubt!). Will see how it works in action but all seems do-able.
     
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