Finally lifted my poor girl out after several years of collecting assorted wildlife. After the guys finished the pressure clean there were hundreds of areas 15-20mm in diameter where the gelcoat is missing below the waterline as shown in the photo below. The shipwright at the yard suggested the best way to fix it was to sandblast the whole hull back to the fibreglass layer and recoat, costing around 15 boat dollars!! The other option is to sand the gelcoat and fair with epoxy and apply several layers of sealant to preserve the remaining gelcoat. This would be a less expensive option but may not solve the problem longer term and wouldn't be as smooth as a finish apparently.
Given the age of the boat and the fact that I only need to have something that will do the job for casual cruising, a performance solution isn't required. Any recommendations from the brains trust on what might work best? Are there any other alternatives for me that would still have a good result?
Cheers
Select to expand quoteWander66 said..
Finally lifted my poor girl out after several years of collecting assorted wildlife. After the guys finished the pressure clean there were hundreds of areas 15-20mm in diameter where the gelcoat is missing below the waterline as shown in the photo below. The shipwright at the yard suggested the best way to fix it was to sandblast the whole hull back to the fibreglass layer and recoat, costing around 15 boat dollars!! The other option is to sand the gelcoat and fair with epoxy and apply several layers of sealant to preserve the remaining gelcoat. This would be a less expensive option but may not solve the problem longer term and wouldn't be as smooth as a finish apparently.
Given the age of the boat and the fact that I only need to have something that will do the job for casual cruising, a performance solution isn't required. Any recommendations from the brains trust on what might work best? Are there any other alternatives for me that would still have a good result?
Cheers
Hi, my solution if it were mine would be, after pressure washing, acid wash, spot blast with a small sandblaster the divots, fill with a good epoxy filler suitable for below water use, fair the filler, sand and paint the entire hull below waterline with an epoxy barrier coat then antifoul and go sailing.
A bit time consuming but way less expensive than a full gelcoat strip.
About 7 years ago I had my below waterline shell blasted, let is dry out for 3-4 months then 3-5 coats of epoxy then 2-3 coats of Interprotect. I followed the International paint guidelines and did as much work myself as possible. Cost around $7k for a 34 ft yacht. This was mainly solving a osmosis issue, but you could follow the same process.
Alternatively skip the shell / sand blasting and instead sand the whole hull to remove the crappy gelcoat, then start applying epoxy, then Interprotect.
Ilenart
The first thing I would do is get a different shipwright. If It was mine I would fill and sand as smooth as possible. Several coats of special purpose grey primer and antifoul. The boat is basically no different to a wooden boat with the gelcoat missing and should be treated just the same. You could seal with epoxy but would have the same effect but cost more.
Thanks all, a good friend has volunteered to help me with the sanding, so we'll so how it goes! I hope he's still a good friend afterwards 
I did sections of my hull in March. Sanded back, faired, sanded, 4 coats epoxy then 3 primacon then antifoul.
I sanded the gel coat off on my boat. I then gave it a single coat of epoxy, faired the hull then followed up with another 10 consecutive coats of epoxy with a 422 additive. I finished it with a wash, light sand and a few coats of grey hempertex aluminium underwater primer.
When I sanded it I left small patches of very very thin gelcoat to be able to gauge how much surface I was removing.
Previous owner had attempted the repair by fairing the gelcoat with a high build primer but the gelcoat underneath continued to degrade and break through the new finish
Select to expand quoteWander66 said..
Thanks all, a good friend has volunteered to help me with the sanding, so we'll so how it goes! I hope he's still a good friend afterwards
I am not the friend that is going to help him.
I really hate it when these millionaire blokes complain about the cost of maintaining their luxury yachts.
Select to expand quotecisco said..Wander66 said..
Thanks all, a good friend has volunteered to help me with the sanding, so we'll so how it goes! I hope he's still a good friend afterwards
I am not the friend that is going to help him.
I really hate it when these millionaire blokes complain about the cost of maintaining their luxury yachts.
Just trying to hold onto enough of my millions that I don't have to drink water out of old fabric softener bottles 
when I retire.
Select to expand quoteWander66 said..
Thanks all, a good friend has volunteered to help me with the sanding, so we'll so how it goes! I hope he's still a good friend afterwards
Not if he has to do it manually. 
Grab some of these
www.amazon.com.au/uxcell%C2%AE-7-inch-Diameter-Sandpaper-Sanding/dp/B07174KVTQ
and use them with a car polisher on slow speed, better then using a belt sander .
You can paint laminating epoxy over any remaining gelcoat ,
trojanfibreglass.com.au/product/500-series-epoxy-laminating-resin-51-2/
after you filled the holes with epoxy & silica filler mix
trojanfibreglass.com.au/product/fumed-silica/
then use 5 coats of International Interprotect or a few coats of Norglass Shipshape and top with your favorite anti fouling.
