Multihull Bulkhead Refit Advice

1208 is great for tabbing

you can wet it all on a table; put it on cardboard and move it to the locations; that is not achievable with no mat tapes; they move too much and must be wetted in place, upside down, etc (pita)

1208 is, frankly, ideal, for repairs

no adhesion left in it is sort of a funny way to look at things; a thixotropic bonding material that hardens and is bonded to both sides IS bonded and requires no ability for future bonding

Thank you for the information! The 1208 has been treating me well thus far. Probably why Lagoon told me about it (all these years ago...)

I'm not sure this 'other' material is/has ever exhibited thixotropic properties. See enclosed picture of both materials. Second frame is after I struck both equally hard with a carpenter's hammer. I wager I will find more of this stuff 'rattling' around the hull during the refit.

Regards - Ogre

Some poly bonding putty or some other type that won't heat up when so thick. @ondarvr has seen it all. Gonzo probablu as well. A poly bonding material is about 25% the typ bond strength of epoxy.

Thixotropic basically means 'thickened and not runny'.

Happy Father's Day to all, from sunny Florida!

When attaching a plywood bulkhead to a balsa cored hull (and deck) what is the permissible gap between them? I've seen several sketches and drawings on this site, but never any mention of an industry standard, min or max distance to be filled with structural adhesive or epoxy...

On my girl, I have a fairly uniform 3/4" (19mm) gap between the edge of the ply and the hull structure (see photo). I was planning on mixing up some chopped fiberglass, 406 colloidal silica & epoxy to create a solid connection. However, since this is my mast bulkhead: is 3/4" to much of a gap? Should this be reduced by adding a thin strip of marine ply? And if 3/4" is to large of a distance, what is optimal for the mast bulkhead???

Of course, I will be reskinning the faces of the bulkheads after this and so the glass will partially be over the thickened epoxy joint further strengthening it.

Thanks for advise & working knowledge in advance on this question.

Coastal Ogre said:

Hello Everyone.

I am currently conducting a refit of a Lagoon 380. Many of the plywood bulkheads are attached and tabbed with a methacrylate adhesive that over time has failed in several different modes. I am looking for advice on how best to refill these gaps (see poor quality photos enclosed) between the bulkhead and the hull to facilitate required vacuum bagging for new fiberglass tabbing. The original adhesive has been found to fail (or has already failed) in chunks in some areas. As such, replacing with methacrylate again is not providing me with confidence. My question is: fill the gap with thickened epoxy, 3M 5200, or some other superior adhesive???

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I am sorry to see this subject thread discontinued.

I felt I was learning something from the intelligent submissions,...particularly about some failures of methyl-methacrylate-adhesives which i thought were some of the ultimate adhesives, ie;
https://www.gluegun.com/blogs/adhesive-reviews/an-introduction-to-methyl-methacrylate-adhesives-mmas
An Introduction to Methyl Methacrylate Adhesives (MMAs) https://www.gluegun.com/blogs/adhesive-reviews/an-introduction-to-methyl-methacrylate-adhesives-mmas

Methyl methacrylate adhesives can replace mechanical fasteners and welding joints. They also offer advantages over other adhesive technologies. Using fasteners like bolts and screws requires more time and labor, and the bolts can corrode and loosen over time. Welding two different metals together is sometimes possible, but it is expensive and labor-intensive. Epoxy adhesives do not bond different metals well because they are more brittle and do not allow for expansion and contraction, which leads to cracks and ultimately bond failure. Polyurethane adhesives need more surface preparation and often require priming of the surface, adding an additional step. MMAs are less brittle than epoxies and can fill large gaps. They have higher bond strength than urethanes and better impact and fatigue resistance. They also offer good chemical and environmental resistance, and fast cure speed

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brian eiland said:

I am sorry to see this subject thread discontinued.

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Still no continuation?