Permanent Structural adhesives

Discussion in 'Materials' started by Bullshipper, Apr 20, 2024.

  1. Bullshipper
    Joined: May 2008
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    Bullshipper Bullshipper

    I am looking for a permanent structural adhesive recommendations for gap sizes up to 1/4- 3/8". I am currently glassing and finishing these joints and it takes forever

    This would be used on bond the raw bottom flange faces on consoles, seat bases, sea walls to raw fiber glassed decks . These boxes all have bottom flanges around their bases that I can trim to 1-2" wide and grind flat.

    I would also like to bond fiber glassed bulkheads to the hull and perform the cap to hull bond on its2" wide outboard flanges too.

    On paper, Plexus MA550 looks good to me but three 5 gallon pails per hull is very expensive.

    I have also looked at vinyl ester based Arjay 7121 which looks more reasonable in cost

    I am very very inexperienced at this so any guidance will be greatly appreciated.
     
  2. gonzo
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    gonzo Senior Member

    How stiff does the joint need to be?
     
  3. Bullshipper
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    Bullshipper Bullshipper

    I would like some elongation to be able to also use it close to outboards where there is more vibration.

    I have been reinforcing poly resin paste with fiber but still think it is too brittle and it does not trowel well when it squeezes out.
     
  4. fallguy
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    fallguy Senior Member

    I’m an epoxy guy, so probably not help, but I use straight cabosil. It does shrink some, but it isn’t really a fairing compound, so shrink is good, imo. It takes awhile to get the measurements right, but about 2.2 to 1 cab to mixed resin by volume, vary per the resin.

    Adding fibers makes things really flow poorly. I only use [edit] bulky, non flowable [edit] fillers when I have concerns about an edge failure.

    This product looks good for esters.

    7121 Vinyl Ester Bonding Compound | For Critical Marine Bonding – Arjay Technologies https://www.arjaytechnologies.com/7121-vinyl-ester-bonding-compound-for-critical-marine-bonding/
     
    Last edited: Apr 21, 2024
  5. Bullshipper
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    Bullshipper Bullshipper

  6. TeddyDiver
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    TeddyDiver Gollywobbler

    For bonding add also talcum powder (with cabosil/fibers) where stiffnes is needed.
     
  7. gonzo
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    gonzo Senior Member

  8. Bullshipper
    Joined: May 2008
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    Bullshipper Bullshipper

    Thanks a lot Gonzo.

    I am planning to test two Vinyl putties when they arrive
    Arjay 7121 @ $725 USD 5 l pail
    IBF 904 or 925 out of Groton CT with is $235 a pail, and already prepared with milled fibers
     
  9. fallguy
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    fallguy Senior Member

    I’m surprised we did not hear from @ondarvr ~ I believe he and another poster here are sme’s.
     
  10. Bullshipper
    Joined: May 2008
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    Bullshipper Bullshipper

    He has been very very helpful on other technical material questions.

    I have already ordered and will test 2 vinylesters so I believe I found a a solution to my problem.

    Thanks again everyone
     
  11. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    This is a complicated subject.

    At one time I was in charge of our putty production for this exact product. Over a period of more than a decade we had worked with a boat builder to develop a bonding putty so they could assemble large components of the build quickly. This included stringer grids, liners, decks, etc.

    The design needed to take into account that these were all bonded surfaces and not being glassed in place as in typical construction. The gaps were rather large at times, so the viscosity was high, plus it was fiber filled and used a strong resilient base resin. The large gap part was critical to the formulation, it needed to cure thoroughly, but have a long gel time and very low exotherm. If it generates too much heat it can distort the surface profile of cosmetic parts from the shrink.

    Commercial adhesives are very expensive, but if you choose the correct one, it can work very well, but it's that cost thing that gets in the way, and a bit of a compatability problem if you need to bond to that adhesive with typical resins later in production.

    What it comes down to is you need to design the parts so bonding in place is taken into consideration, they may need a larger surface area than a glassed in part to survive long term abuse. Plus get the formula correct to achieve your goals, it takes a bit of time to dial in the correct combination of properties.
     
    Last edited: May 16, 2024

  12. Bullshipper
    Joined: May 2008
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    Bullshipper Bullshipper

    Thanks

    Gaps on the deck to the box units are trial fit and kept to 3/8" and under between the 1 3/4" wide bottom outboard flanges with perimeters lengths of 200, 200, 300 and 150 inches long going onto decks with 2 layers of 1.5 oz csm + 1 of 1708 and 1808 of the top that goes up the hull sides 3" on a filleted radius around the deck perimeter

    The side bonding areas under the 4x9' deck panels have a 3" w x 27' long surface on both star and port with a flat tunnel top between them that is 19" wide at minimum so i am hoping that the areas mentioned are more than sufficient to produce strong enough bonds as opposed to bonding and fiber glassing them together which creates a a huge amount of man hrs as its don inside and out

    Bulkheads and stringers will continue to be glassed to the ins and the layup for the lower the hull is 50% thicker that what Vectorworks called out in their material analysis so that I can sleep at night

    No coremat or cores are used in the lower or upper 3 piece hull or other pieces except for the Airex decking, and Coosa 26 cored transoms and bulked and stringers employed to bolt in the fuel tanks and reduce panel lengths

    the hull is very solid and makes no noise on the water as customers want wot speeds of 60 mph going into small head chop.
     
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