Gel Coat Repair

[DRANNIE]

Finally made it up to the boat yesterday as she had been lifted onto her trailer. It looks like she has taken a knock against the pontoon during the storm surge a couple of weeks ago a 50p sized bit of jel coat has been knocked off the bow. I am happy that a gelcoat repair should be straight forward, I've put some waterproof tape on until can do the job.

I question is that it has exposed the mat underneath which seemed quite furry almost like it hasn't got any resin in it. The knock doesn't seem deep enough to be down the balsa core. Should I apply some apoxy first or just slap in the gel coat repair paste. (The boats a 22ft, 25 year old eboat. She's been painted so I'm not worried about colour matching.)

Ps Thanks to the guy who helped me chock my trailer up yesterday.

 

[William_H]

You are right in thinking that epoxy may be a better repair medium. It will stick better than polyester (the gel coat).
Epoxy must be protected from UV radiation but the painting will take care of that. You might like to warm the epoxy or even thin it with meths for the first layer to hopefully improve the attachment to the CSM glass. I am not sure but it does seem a bit like the CSM was not well saturated in the first place.
Keep the whole job warm and some microballons will provide a filler for the final coat that is sanded smooth.

Of course polyester resin will probably be OK also. I think if you want you can use the same pigment for poly or epoxy. A pigment may help to cover up the colour change of the repair when painting.

good luck olewill

 

[gjgm]

gel is brittle.. if the grp isnt stable, your filling repair will just crack. Id say grind back an inch all round, including a layer or so of grp and build up with some circles of glass fibre, smallest first, and squeeze the excess resin out as you put the next circle of fibreglass. Needs to be quite warm, BTW. Then when you know you have a reasonably sound base, finish with some gel repair paste, or gel if you prefer.

 

[sparkie]

Hi, had exactly the same problem with mine. Two patches of gelcoat knocked off during lift-out in a heavy swell. Filled with Plastic Padding marine filler and faired off, painted with 2k acrylic to match existing, result pretty good IMHO! The Plastic Padding seems easier to sand than gelcoat filler but I'm sure is just ordinary polyester. If it was below the waterline I would use epoxy, but above it I personally wouldn't bother.

Sparkie

 

[DRANNIE]

Thanks for the advice guys. The ordinary car plastic padding is hydrostatic so could get water into the substrate. I think I'll take a middle course of chipping back a bit more gelcoat, soaking the exposed glass area with epoxy and then gelcoat on top. I'm a bit nervous of cutting back any more grp as the hull isn't that thick and there is a balsa core in there somewhere. If I'm feeling flush I might see how much the yard with charge.

 

[Avocet]

Hopefully somone else will confirm this but I DON'T think gelcoat (polyester gelcoat, that is) will stick to epoxy that well. IF you put ANY epoxy at all on the "wound" I think you may be committed to using epoxy for the rest of it! Also, I've seen loads of crashed fibreglass cars in my time and the powdery "dryness" you descibe does not necessarily signify a poor (or "dry") layup. The strongest GRP laminates have the highest volume fraction of glass in them. In fact, it's almost impossible to get too much glass into the mix, you only need enough resin to form a "matrix" round each fibre. On impact, the resin shatters creating the dust and the glass fibres spring out of it. Of course, it IS possible to get a dry layup and without looking at your boat I won't say it's impossible, but I know that impact damage is quite often mistaken for a dry layup.

A couple of other thoughts though. It's a bit odd (I think) for a well laid-up piece of GRP to be able to loose a 50p-sized chunk of gelcoat without any other signs of damage to the surrounding area. This suggests either a defective patch in the layup, where the laminate hasn't stuck properly to the back of the gelcoat OR it suggests that in the next week or so you might notice small black and very fine stress cracks radiating out from the centre of the impact point. If so, you might have to reinforce the back of the laminate (if you can get to the inside of the laminate!) and then grind out those cracks in the gelcoat and fill them as well.