Which resin sticks to which?

[zoidberg]

I need to reinforce the inside of my bow where I'll drill and fit a U-bolt externally..... with a spreader plate inside. It's very difficult of access.
It seems the original layup used 24oz. woven with polyester resin. I want to wet the scoured original surface then layup some CSM plus a layer of 400 wove - which I have - using West System 206 epoxy, again which I have.

Paul Rainbow reminded me/us of P40 Isipon polyester paste, which could be useful 'right in the crack'.

Is Isopon polyester filler compatible with West epoxy - or not?

 

[yoda]

CSM falls to bits with Epoxy, I would stick to woven rovings, Let the Isopon set before using epoxy and you should be fine.

 

[William_H]

I have a similar fitting on the bow of my trailer sailor. Used for winching the boat on to trailer but also used for primary load of swing mooring. I imagine you are doing something similar perhaps for a down guy to a bow sprit. In any case that area of the bow will be very thick with GRP. If you wish to make a flat area for the nuts to sit on you can just fill with polyester paste or put in some cloth or CSM. All the load will be trying to hold what will in essence be a a packing piece.
Now my little boat has spent 40 years on this swing mooring and I have had some experience with this fitting. It gets some sideways snatch loads so fatigue is a real problem. The orinal U bolt had a thick 3/8 inch U but the threaded portion was wasted down to 5/16 inch to allow the U bbolt to be tightened in to the GRP. It snapped off at the wasting with fatigue. In fairness it was only intended to take straight pull of a winch. I replaced with a large saddle Bolted in to the original holes. While I have replaced this a while back it seems the flat base of the saddle supports sideways loads better. On the inside I just have a piece of stainless steel plate to make a flat for the nuts. (5/16 inch bolts nylock nuts) https://www.whitworths.com.au/ronstan-stainless-steel-narrow-saddle-5-16 (in case readers do not use the name saddle) ol'will

 

[vyv_cox]

CSM for polyester resin has a binder that this resin dissolves. Epoxy does not dissolve it. I think there are CSMs specifically for epoxy but otherwise use woven rovings that has no binder.

Epoxy has better adhesion to old polyester layup than polyester does but abrasion is still needed.

 

[zoidberg]

Thanks, all. That clarifies.

But.... I still need longer arms to go with my shorter pockets.