Gelcoating - Upside down??

[cjj216]

Got a couple of gelcoat chips on the chines that I will be sorting some time over next couple of weeks.
My only experience with gelcoat was 30 years ago repairing a bike fairing.
As I remember it, it's the consistency of emulsion paint.

Turning the boat upside down isn't an option.
Question is - How do I get the correct thickness in one go, with gravity working against me?

[ShinyShoe]

With difficulty!

If you are using gel rather than flow coat you need to exclude air. So get some clear plastic (acetate OHP film is good if anyone still uses such technology!) For a chine you might need to add a crease. Slap on the gelcoat, you can thicken it with some epoxy filler like glass baubles. Use the acetate to hold it in place, secure with masking tape. Remove when hard and sand to shape.

If you are using flow - the wax may float upwards? In which case you may have (non-)sticking issues to the substrate which is above it. Never used flow upside down.

Or use a plastic padding gelcoat filler which is like putty. But harder to colour match.

[ShinyShoe]

Oh and consistency is more like honey

[mdearman]

I don't think flowcoat works that way, but happy to be corrected. I think the wax moves to the surface, not the top. I've been using it on various surfaces, some of which are upside down without issues so far.

[jeffstevens763@g]

no expert but just made a console for my sib used flow coat up side down no issues plenty of hardener put acetate over it as shiny says to get finish it wont be perfect but better than a chip.
there's also vacuum bagging for gel coat.

look on east coast resin supplies the have videos of all procedures with list of stuff needed good lads to talk to for info and quantities needed

me personally i would go with flow coat you can thicken up with a powder if required finish with a dremel to get rough bits off for small chips

[cjj216]

Thanks for replies.
Looks like either way would work. (plastic to contain and set gelcoat or thickened flow coat)
I'll give east Coast a call before ordering and see what they say.
If I was shy of existing surface in one go, could the gelcoat be built up in layers?
As you'd expect, the gelcoat is quite thick at the chines.

[jeffstevens763@g]

Originally Posted by cjj216

Thanks for replies.
Looks like either way would work. (plastic to contain and set gelcoat or thickened flow coat)
I'll give east Coast a call before ordering and see what they say.
If I was shy of existing surface in one go, could the gelcoat be built up in layers?
As you'd expect, the gelcoat is quite thick at the chines.

not an expert but i would build up past and flat back with different grades of paper and polish but east coast might have a product or a method to help you.

cheers

[Tim in Yorkshire]

I managed to gelcoat my chine chips from below, using the plastic on top method followed by a little flatting down. No real issues, where I did get the odd run I just wet and dried it off.

[gtflash]

Depends on the thickness to be filled. Cabosil increases the thickness of gel and makes it run less. Other fillers don't stop gel running or falling off as good as cabosil. Cabosil can be used as a filler itself. It is very strong but sanding will be a pig. You could thicken a bit of gelcoat with it, till it will stand up on its own then lay it on the boat and cover with film. If you wanted it easier to sand add another filler like microballoons. I love mixing my own fillers. It's very satisfying but not always cost effective.

Ecs make their own gelcoat filler. It's good for gap filling but too thick to skim coat and get a pin hole free finish. It would probably be fine on a corner or filling chips up to 10mm but it can pull itself off a surface if you try to fill tiny holes. It's very strong, needs no extra wax but takes a while to go off. At least 24hrs before sanding.

Plastic padding gelcoat filler is really nice to mix up. Goes off in minutes and can be sanded in hours. But it is a funny colour white and quite brittle. Perfect for small chips

Any picture of ur issues

[jwalker]

Gel coat is thixotropic and doesn't particularly sag, it's used on vertical surfaces when moulding.

Wipe the area clean using detergent, cut back the chipped surface and the area around the chipping using 60 grit abrasive paper. Don't finger the surface. Mask up the good area around the damage. Apply successive coats of gel until it is proud of the surrounding hull. Cut it back using whatever tools you have - file, rasp etc. Level and finish it by going down the grades of abrasive paper. Remove the masking tape and finish with 800 grit wet n dry blending into the original hull. Finally polishing with Tcut or similar will shine it up.

There is no need to add wax to the gel coat to exclude the air since you're removing the surface anyway. The surface will be tacky but it will be cured properly below the tackiness.

Goid luck with it.

[cjj216]

Many thanks to everyone 👍

[ShinyShoe]

Originally Posted by jwalker

There is no need to add wax to the gel coat to exclude the air since you're removing the surface anyway. The surface will be tacky but it will be cured properly below the tackiness.

But you will clog your sandpaper as dust will stick to it...

[Pikey Dave]

Originally Posted by ShinyShoe

But you will clog your sandpaper as dust will stick to it...

Not if you use wet & dry with a hint of Fairy liquid


.....sh1t happens.......

[ShinyShoe]

But will the tackiness not stick to the sandpaper? So the extra dust tends not to stick but in my experience of trying to use gel as flow your sticky gel surface still sticks to the paper and so you stop sanding because the sticky layer clogged the 'sand'

[Pikey Dave]

Originally Posted by ShinyShoe

But will the tackiness not stick to the sandpaper? So the extra dust tends not to stick but in my experience of trying to use gel as flow your sticky gel surface still sticks to the paper and so you stop sanding because the sticky layer clogged the 'sand'

not if you sand it wet I only ever use gel coat, once you knock the initial layer back with some 400 grit wet & dry, there is no sticky. I just work down the grades to 1200 grit always keeping it wet with aforesaid hint of Fairy. Then I use the Fein with a polishing pad & cutting compound. Finish with a polish of Mer.

[gtflash]

I find sanding wet gel is always like two steps forward. One step back. Despite soap and all the other tips.

Also if the gelcoat chips are deeper than a couple of mm. I'd be careful using in filled gelcoat. Just from my hobbiest experience

[Pikey Dave]

Originally Posted by gtflash

I find sanding wet gel is always like two steps forward. One step back. Despite soap and all the other tips.

I must be doing something wrong then

[cjj216]

gtflash - the gelcoat chips I'm filling are on the chines so are quite thick/deep. They go to the fibreglass beneath but not in to it. The gelcoat is more than 2mm - more like 4mm

If the gelcoat I'm filling is more than a couple of mm, why would you not fill with the same material? Would you be filling up the chip to 2mm shy of the surface? If so, why, and with what material? Thanks

[cjj216]

The chips are about the size of a fingernail. I haven't properly investigated yet but I have seen 2. Beached on coarse sand but over the only rock on 500m of beach. 😡

[ShinyShoe]

The fingernail size is fine. The deeper they are the more likely that as it cures it shrinks leaving space between fibre and gel unseen until a little knock makes it fall out. Building up in layers will solve that. Or fill with an epoxy filler and surface with gel. Or you can mix some chopped strands (East Coast sell them. Get the smallest, finest you can get) which will give the gel some extra strength. But still finish with plain gel. I doubt 4mm is deep enough for that.