I’m currently replacing the Mylar (Dura-lar) water seals on the bottom of the hulls below the centreboard boxes . Is heavy duty contact cement the best adhesive for this job o is there something better?

I've used Goop. Don't let it skim-over before you put the tape on.

I have an article saved somewhere that gives more details; will see if I can find it. I think you'd want to use something like Sikaflex.

I'd go for what's known as a half gasket, much cleaner, but a little more work the first time you do it.

https://drive.google.com/drive/folders/0B2jHf8coA9KibTU5Q3V4VnBFd1U

I have been using HD contact cement for a decade now, as does everyone i sail with whom has a centerboard (about 10 of us). some have tried to epoxy them on ... makes removal a 1000x harder
i do sometimes epoxy the tips so they don't peel up

works fine
i use a water proof one from a local gel coat company, i would not be surprised if it is just private labeled


https://www.fgci.com/item…ear-Quart-High-Strength/