Best materials and techniques for filling and fairing different hull areas

[DHV90]

Hi,

As part of the refit on the boat we'll be doing lots and lots of fillering, and was wondering if anyone could share preferred approaches and materials for all of the following tasks please? I have a rough idea but would like to hear if anyone has done anything different and what products have worked well, and which have worked less well. Especially curious which types of fibreglass mat etc. to use for the larger repairs. Bear in mind most of these repairs will be a base for gelcoat, does that rule any fillers out? No epoxy maybe?

1. Repairing small screw/bolt holes in deck
2. larger deck holes, e.g old instrument or compass holes
3. fairing the deck ready for gelcoat, after patching holes
4. fairing the hull (namely the hull/keel join area for us)
5. fairing large chips and dings in the topsides

thanks guys

 

[Tranona]

Suggest you go on the Wessex resins website where you will find good information on fibreglass repairs using epoxy and various fillers and glass reinforcements. Epoxy bonds well to polyester and is very versatile for both laminating and for filling and fairing using different additives appropriate to the job.

 

[William_H]

Yes I would go epoxy either with glass cloth or filler.
I am concerned that you want to finish with "gel coat" This is not the best "paint" for your grp despite the fact that it is the original material. Gel coat is really just ployester resin with a pigment in it. It gets its smoothness and gloss from the polished wax on the inside of the mold. The "gel coat" is applied to the inside of the mold and is allowed to partially harden. The polyester resin is then applied with glass often from a glass chopper gun or hand layed with woven rovings or glass mat. The timing is critical to applying the glass. Too soon and the glass can be pressed through the soft gel coat layer so appears on the outside of the hull. However it must be soon enough that the resin of the gel coat chemically bonds with the resin and glass so making a solid bond.
Now after some weeks the GRP is fully cured (hardened) and becomes chemically quite inert. So any additional resin (as in gel coat) will only stick by mechanical attachment. Polyester resin however due to some shrinkage on curing and its very nature is not so good at bonding to anything mechanically. Epoxy is much better at bonding.
Having said that polyester does stick to stuff like old GRP but not as well as epoxy. Paint especially 2 pack polyurethane is also very good at bonding and can give a good finish. Epoxy must be painted over due to UV deterioration.
So I suggest you consider painting the hull all over with one of the yacht paint systems.
Now the deck is a different problem. Painting it will smooth out the non skid pattern so if you do a complete repaint of the deck you will need to add non skid particles. No matter what you do a patch up job with you will need to match the deck colour. A paint merchant can help you get just the right shade to allow for fading etc. All very tricky. I would still advocate polyurethane 2 pack brushed on for patching the deck. PS don't repaint the deck as I did in white. Too bright in the sun.
good luck olewill

 

[Salty John]

Try to find a copy of West Systems booklet,
Fiberglass Boat Repair and Maintenance, catalog number 002-550
It contains a wealth of information on the subject.

 

[DHV90]

Thanks for the input, those look like 2 fantastic resources, and will have everything I need, much appreciated!

And william H, I know how the gelcoat was originally applied into a female mould, but after extensive research over the last couple of years I have decided that it will be the best solution for a comprehensive deck refit. Sprayed on and carefully long boarded and sanded, it will take time but its the best option in the long run. Non slip will then obviously be painted over the top of this. It's not going to be a quick slap on brighten up, everything is coming off the deck every hole filled, then sanded right back before applying the new gel. I will be doing a few test runs in places before fully commiting to gelcoat but so far its the strongest contender!