Thru Hull bedding compound recommendations

[bigwalt]

I am replacing all thru hull fittings in a 45' sailboat I am restoring. It is fiberglass with an airex core. What is the best bedding compund to use to seal up the fittings??

[k1vsk]

The West Marine web site advisor has a good summary of adhesives, bedding compounds and sealants which should answer all your questions. About the only thing you will get most folks to agree on is to not use 3M 5200

[mitiempo]

3M 4200 or Sikaflex 291 are good choices. Also best to remove the Airex around the cutout and replace it with thickened epoxy if this was not done originally as it should have been. This will prevent compression of the hull and eliminate water ingress into the core. While Airex cannot absorb moisture if present it can lead to delamination.

[roline]

Always, always, dig the soft coring out around any hole and fill with a thickened epoxy, top side or bottom side:
* To create a solid incompressible wall to prevent the loss of clamp load from the fasteners.
* To seal and protect the core from ingression that can lead to saturation and delamination.
* To unify the structure should you ever decide to replace or re-bed the hardware in the future.
* Reduces the dependency on the sealant selected to the structural soundness of the job.