Hi,

I have a smallish hole (4" x 1" by the time I have removed damaged area) to repair in a glass fibre kayak. The original layup is chop strand matt, woven cloth and polyester resin with white gel coat. The hole is inside the cockpit area and I have good access to both inside and outside to carry out the work.

I see a lot of poor quality glass fibre kayak repairs and I'm sure it is possible to do a lot better. I want to avoid any big clean up, gel coat filling & sanding etc on the outside and I definitely do not want the patched look that I see too often.

I have seen the excellent composite kayak repair video but I don't think it would work the same way after cutting out the damaged glass fibre.
However I would like a high quality, strong and invisible repair.

I was thinking that using the vacuum bagging technique to improve the strength and cosmetic appearance of the repair might work well.

Would it be possible / recommended to start with a suitable mold surface for the outside, release agent, gel coat, layup and then bagging inside and outside? Maybe it's not possible to pull the vacuum with the hull in the middle?

Would you be able to advise on process and materials?

You shouldn't really use vacuum consolidation with polyester resin.  Repairs look bad because people do bad repairs.  A well done repair should be invisible.  You will probably need so sand and polish the gelcoat repair to get a good finish mind.

Sorry - I was planning an epoxy repair even though the original layup is polyester.

Hi Tim,

Thanks for the post and sorry for the delay in getting back to you. You're right that from a structural perspective, an epoxy repair will make for a stronger repair - epoxy bonds better to fully cured polyester than polyester does and of course the area of the repair will be stronger if it uses an epoxy matrix but it will leave you with some difficult decisions regarding gelcoat, as you're looking to make an 'invisible' repair because you'd really want to use an epoxy compatible polyester gelcoat (so we're talking GC50) pigmented white as the gelcoat layer but the way the GC50 works with its epoxy bonding is that it's the epoxy that bonds to cured GC50 NOT that GC50 bonds to cured epoxy so if you're working 'inside out' like you do on a repair then there is no oppertunity where you can apply the GC50 gelcoat and then let it cure before doing the main repair with epoxy (whcih would then bond really well to the cured GC50).

I've got a few ideas but would it be possible to see a photo of the repair (inside and out if possible). The way I want to suggest depends on just where the damage is and how accessible it is. I could go on without a photo but if you could add one to this thread it would be very helpfull.

--Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Thanks Matt - I will get a photo and upload it as soon as i can.

Hi Matt - I have attached a couple of photos as requested, hope that helps.

Hi Tim,

Thanks, they're great photos, I can see exactly what's going on now.

To be honest, that damage doesn't look too serious; I think you could do this repair all in polyester if you wanted to and it would be fine. If you want to make the repair a little more robust then I would mix up a small amount of our Epoxy Rapid Repair Resin and using a small brush work the rapid repair resin well into all the broken and damaged area (from the outside of the boat) and then add it a few chopped fibres of glass, mixing them in with the resin so that the majority of the 'gap' is filled with this mix of chopped glass fibres and epoxy resin. don't fill it up completely, you want to leave it slightly recessed so that you have room for the gelcoat.

Once you've done this, from the inside of the boat I would take away any broken material you can find and then do a similar operation, again filling any actual recess (if there is one once any broken material has been removed) with epoxy and short strand glass fibres and then  over the top of that I would use patches of woven glass, wetted out with the epoxy repair resin to patch over the damaged area, ensuring the strength is restored.

There would not be any easy way to make use the vacuum bagging tecnique in a repair like this but you could use some perforated release film and breather cloth pressed hard against the repair patch from the inside whilst it cures to squeeze out any excess resin and ensure that the repair is well consoldated against the damaged area. Once the epoxy cures the release film and breather can be removed.

Finally, I would use a polyester gelcoat pigmented with a white polyester pigment paste so repair the gelcoat on the surface. You may choose to build up the gelcoat slightly proud of the surounding area and then, once cured, gently flat back and polish the repair so that is is flush with the surounding area. Finally it can be polished up to a full gloss using a polishing compound. Addition of a few drops of solution MW wax additive (we have this in stock but it's not listed on the site so contact us if you need this) added to the polyester gelcoat will allow it to cure hard on the surface and not remain tacky like gelcoat normally does when it cures in contact with air - this is not essential for this repair but does make the gelcoat more sandable, particularly at first. An alternative is to pull release film gelcoat over the gelcoat repair whilst it's uncured and then remove it afterwards and do any final flatting and polishing.

Doing the gelcoat last ensures that it won't get knocked around or damaged when you do the other bits or repair work.

I hope this helps and wish you all the best with your repair.

--Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Thanks for the great help Matt - I am just shopping on the website ready for an order but I don't see polyester gelcoat and I would also like to add the MW wax additive. Will it be easier to phone in the order?
 

Yes, give us a call and we can sort this missing two ingredients!

Matt Statham
Easy Composites / Carbon Mods - Technical Sales