Polyester resin to seal deck fittings?

[GTom]

I have to replace some deck fittings, and was wondering, is it OK to use polyester (styrene) resin, or should I go shopping for epoxy?

It is a balsa cored deck, thinking about 3 options, epoxy, polyester or simply sikaflex.

 

[graham]

It's vital to keep water from the balsa core.I would remove the old fittings clean up the hole and seal the edges of the hole with epoxy .once epoxy set hard replace fittings using sikaflex or other high quality sealant

.You may need to use spacer o ver the bolts to prevent deck being crushed by the bolts being tightened

.The inner layer of GRP may be quite thin so metal plates to spread the load may be needed

 

[fisherman]

Resin alone or with mat will leak almost instantly. Some people like to use Sika, or I find CT1 is maybe even better, bolt the fitting down but not tight until the sealant has gone off, so you don't squash it all out.

 

[jwilson]

Don't just use any sealant. It will almost certainly leak and you will have a soggy deck eventually. When you come to sell the boat a surveyor will find it and you will be truly horrified at how much value has been deleted by simple sloppy work.

In my foolish youth I once bought a boat with a soggy balsa core in the coachroof. Fixing it was a nightmare. Do-able, but one of the worst jobs you can think of.

As Graham has said, you need to totally guarantee water will not get into the balsa. See http://www.ybw.com/forums/showthread.php?177819-Bolting-fittings-through-a-balsa-core-deck

 

[LoneHort]

Why on earth would you use an adhesive sealant like ct1. Goosed if you ever need to get it off again. Use a butyl based sealant like arbomast instead.

 

[macd]

Why on earth would you use an adhesive sealant like ct1. Goosed if you ever need to get it off again. Use a butyl based sealant like arbomast instead.

+1 to all that, and especially the butyl.
My preference would be butyl tape, both to bed the fitting and as sealing 'cones' under countersunk bolt heads. It will not leak and will allow the fitting to be easily removed next week or a decade hence. However, with cored decks the presumption should be that any bold-hole will leak. Thus an epoxy sealed ground should be created.

 

[fisherman]

Why on earth would you use an adhesive sealant like ct1. Goosed if you ever need to get it off again. Use a butyl based sealant like arbomast instead.

Yes, I did say 'maybe', not used it for such work myself, only for seams in a rowing boat, for which it did very well.

 

[GTom]

Sorted, a west system package is already in the trunk, just need to learn how to use it sparingly The balsa already started to rot around the fittings, my predecessor made a crap job, took 2 hours to remove all the rotten material.

 

[graham]

One method is to drill the holes out oversize then completely fill the hole with epoxy.

Re drill the holes down through the center of the epoxy plug leaving the edges sealed.

 

[macd]

One method is to drill the holes out oversize then completely fill the hole with epoxy..

The usual method is to grind down the short arm of an Allen key into a blade. Then insert the long arm into the chuck of a drill. Then tease into the hole in the deck and judiciously remove the core material. The epoxy core can then bond continuously between both top and bottom deck laminates.

 

[lw395]

The usual method is to grind down the short arm of an Allen key into a blade. Then insert the long arm into the chuck of a drill. Then tease into the hole in the deck and judiciously remove the core material. The epoxy core can then bond continuously between both top and bottom deck laminates.

That's what I did. I thickened the epoxy with glass fibres chopped from a bit of cloth.
Worked well. Countersink the bolt holes slightly so there is a ring of sealant arond each bolt. Silicone sealant works well, as will polyurethane, unless the area of sealant is very big and difficulty of dismantling becomes a real issue.