Keel repair

Donie · 10 January 2021, 09:58

Hi, I’m refitting my Zodiac Pro Open 550 at the moment. I got the boat indoors over the Christmas and stripped her down. The boat had a hard life in its early years and there is a decent sized fibreglass repair on the keel. It’s around 12-14 inches long and comes 4 inches up the sides of the keel. It’s at the bow end of the keel. It seems that it had some glass cloth glassed over the repair after it was filled. Then gelcoat was applied roughly over the glass.
I have sanded back the repair and I’ve ended up with some bare fibreglass. I’ve used some Plastic Padding Gelcoat filler to fill any low spots.
My plan is to give the area a few coats of white gelcoat and then add a topcoat/flowcoat. Should I just use topcoat or would it be a better job to do a few coats of gelcoat to give better thickness for final sanding.

mickter · 10 January 2021, 10:21

On outer hull would use gel coat,

Donie · 10 January 2021, 10:42

Thanks Mickter, what’s best to cover the gelcoat with to make it cure properly? Is a flowcoat a good way to seal the gelcoat to get it to harden

mickter · 11 January 2021, 10:26

Dont understand why you would put anything over gel coat.
is repair on outside of hull or inside,if outside paint gel coat over repair , wet/dry and polish.

Pikey Dave · 11 January 2021, 11:07

Quote:

Originally Posted by mickter

Dont understand why you would put anything over gel coat.
is repair on outside of hull or inside,if outside paint gel coat over repair , wet/dry and polish.

Gelcoat doesn’t cure properly in air, it stays tacky. For a repair “in air” it’s normal to use Flowcoat which has wax added to make it go off. For small repairs I’ve used gelcoat & covered it in cling film or brown parcel tape to keep the air out. Parcel tape works well on keel chips as it keeps the gelcoat in place & moulds it to the correct profile.

Donie · 11 January 2021, 11:47

Is it possible to build up layers of Flowcoat/topcoat? Should the second layer be applied while it is still tacky?

jeffstevens763@g · 11 January 2021, 13:29

full instruction video on these gel coat repair kits

https://www.ecfibreglasssupplies.co....at-repair-kits

mickter · 12 January 2021, 10:31

Quote:

Originally Posted by Pikey Dave

Gelcoat doesn’t cure properly in air, it stays tacky. For a repair “in air” it’s normal to use Flowcoat which has wax added to make it go off. For small repairs I’ve used gelcoat & covered it in cling film or brown parcel tape to keep the air out. Parcel tape works well on keel chips as it keeps the gelcoat in place & moulds it to the correct profile.

The gel coat repair kit I get when mixed with the hardener and painted over my repairs goes off hard and has to be sanded. I get it from Force 4.
is this different.

Pikey Dave · 12 January 2021, 10:45

Quote:

Originally Posted by mickter

The gel coat repair kit I get when mixed with the hardener and painted over my repairs goes off hard and has to be sanded. I get it from Force 4.

is this different.

Dunno🤷*♂️ As it’s sold as a “repair kit” it could be flowcoat or epoxy based. The fact that you’re buying a specific off the shelf repair kit, as opposed to raw gelcoat, would suggest that it’s designed to cure in air.

jeffstevens763@g · 12 January 2021, 11:49

Quote:

Originally Posted by mickter

The gel coat repair kit I get when mixed with the hardener and painted over my repairs goes off hard and has to be sanded. I get it from Force 4.
is this different.

you probably got this type which has wax in it [flowcoat in other words]link below
as Dave says gel coat needs to cue without air in the link i posted look at the kit contents which has a film to stick over the gel to form it and let it cure without air.
vacuum bagging is another way of doing it

when you click on the gel coat required there's an instruction video

https://www.sheridanmarine.com/produ...at-repair-kits

Ribtecer · 12 January 2021, 12:51

When I did the repairs on my project, I painted PVA over the gel coat, once it had gone off I cleaned off the PVA with water.

Worked a treat, not my idea, the tip came from someone on here.

GuyC · 12 January 2021, 14:11

https://www.ecfibreglasssupplies.co....gelcoat-filler

I used this stuff.

Pikey Dave · 12 January 2021, 14:56

If you can get the gelcoat on thick enough & proud of the repair, you can rub it back to profile & lose the tacky layer. You need plenty of depth though.

jwalker · 12 January 2021, 19:39

My worry is that you have a weak repair. If the previous repairer applied glass cloth over the repair it suggests to me that the under repair build up was little more than a filling job. It could be ok but you won't know unless you dig deeper. At the very least you need to go down deep enough so that your new gelcoat can be finished flush with the original hull line. Gelcoat is thixotropic so it will build up without running off and the thicker you can apply it the better it will cure. When you mix it try not to trap air within it to prevent you having small voids when you sand it back to shape.

For the final surface material you need straight forward gelcoat resin with a touch of wax additive to prevent it being sticky. It's only sticky on the surface. You can mess about with sealing it but a few mls of wax is all you need to do the job easily. If you think you may need to apply more than one layer of gelcoat resin, don't put wax into the first one. Alternatively, if the area is not large, just use the gelcoat as is, accept that the first sheet of abrasive paper will clog when you first try to sand it but it'll only cost you a few pence for the paper.

Ribtecer · 12 January 2021, 20:46

Quote:

Originally Posted by jwalker

but it'll only cost you a few pence for the paper.

Are you sure you're a Scotsman?

Great advice btw.

Donie · 13 January 2021, 12:00

Thanks for the advice folks. I’ve had a good look around the hull and there is no interior damage and no loss of strength. It seems somebody just decided to finish the repair by putting a sheet of glass over it and then some gelcoat, leaving a very rough finish.
I’m going to flatten it back, fill any low spots, sand, wipe with acetone and give it a thick coat of gelcoat followed by a coat of flowcoat to make it all harden fully. I tried re-gelcoating and piece off a sailing boat last year and it never hardened at all. I ended up having to scrape it off. Disaster! I think it may have been too thin of a coat.

jwalker · 13 January 2021, 14:59

Quote:

Originally Posted by Ribtecer

Are you sure you're a Scotsman?

Hehe...well I'm actually a taffy but my mum and her family are Scottish as was my wife and as is my partner and I've lived here for over 50 years so I claim jockness. If Nicola gets her way, I might have to officially apply for it! Or I could move to England!!