Polycraft 10Kg Fibreglass Repair Kit Review: a big, no-nonsense bundle for serious repairs

I picked up the Polycraft 10Kg Fibreglass Repair Kit because I needed to sort out a few bigger jobs: some damage on an old GRP boat hull, a cracked fibreglass roof section, and a dodgy corner on a trailer. I was tired of buying tiny repair packs that barely cover a dinner plate. This one is 10kg of resin plus a full 10m x 1m roll of 450gsm mat, so it’s clearly aimed at proper repairs, not just patching a bike fairing.

To be clear, this isn’t a beginner toy. It’s a proper polyester resin kit with MEKP hardener, so you need to know the basics: mixing ratios, working time, safety gear. The listing even says you should know what you’re doing, and I agree. If you’ve never handled fibreglass before, I’d start smaller. But if you’ve done a few repairs and you’re just sick of running out of resin halfway through, this size makes sense.

I used it over a couple of weekends, on three separate jobs, in typical UK garage conditions: not heated, a bit damp, around 12–16°C. That’s not ideal for resin, so it’s a good test of how forgiving the kit is. I wasn’t gentle with it either – I mixed multiple small batches, pushed the working time, and layered up fairly thick in some spots.

Overall, it behaves like a straightforward, no-drama fibreglass kit. It doesn’t try to be fancy. No colour pigments, no fancy extras. Just resin, mat, hardener and a syringe. If you want something that just gets the job done without any marketing nonsense, this is in that lane. But it does have a couple of quirks you should know about before you go all-in on a big project.

In terms of value for money, this kit makes sense if you’ve got multiple jobs lined up or one big project. 10kg of resin plus a 10m x 1m roll of 450gsm mat is a lot of material. If you compare it to buying several small 1kg or 2kg repair kits, you usually end up paying more per kilo and constantly running out halfway through a job. Here, you pay once, and you’re basically set for a good chunk of work.

Where the value is a bit more mixed is in the accessories and hand-holding. You do get the syringe and the catalyst, which are important, but don’t expect brushes, rollers, mixing pots or a big glossy manual. It’s not that kind of kit. So if you’re new to fibreglass, you might end up spending extra on tools and spending time watching tutorials. For someone who already has the gear and experience, that’s not a problem. For a complete beginner, the overall cost (kit + tools + safety gear) can creep up.

Compared to random cheap fibreglass kits I’ve used from local car parts shops, this feels more consistent and better quality, especially the mat and the way the resin cures. The Lloyd’s approval for the resin is a nice bonus if you’re doing marine work and want at least some reassurance it’s up to the job. You’re not paying premium epoxy prices, but you’re also not scraping the absolute bottom of the barrel.

So, if you only need to fix one tiny crack, this is overkill and not great value. But if you’re planning to do a hull repair, a roof patch, and keep some in reserve for future jobs, the price per kilo and the overall reliability make it good value. It’s basically a bulk, no-frills option that pays off when you actually use most of what’s in the tubs.

The resin itself feels like a standard general-purpose polyester laminating resin. It’s not pre-waxed, so you can build multiple layers without sanding in between as long as you stay inside a reasonable time window. I noticed it wets out the 450gsm mat without needing to drown it, which is good. Some cheap resins either sit on top or you have to flood the area; here, once you work it in with a brush or roller, the fibres go transparent in a fairly predictable way.

The 450gsm chopped strand mat is decent quality. No big dry patches, no weird binder issues. When you tear it by hand to feather edges, it behaves like proper mat – messy, but controllable. I used it on vertical surfaces on the boat hull and it didn’t slump badly once resin was worked in; you still need to be sensible with how much resin you slap on, but that’s normal. For more delicate work this is overkill, but for structural or semi-structural repairs, this weight is a good compromise between strength and ease of handling.

The MEKP catalyst is standard stuff. The two 130ml bottles are more than enough for the 10kg resin if you’re mixing in normal ratios (around 1–2% depending on temperature). The included syringe helps a lot with not overdoing it, especially on small batches. I usually mixed in 200–300g resin portions in plastic tubs, and the syringe made it easy to keep mixes consistent. No odd reaction, no yellowing beyond the usual, and no weird smell beyond what you’d expect from polyester resin.

Overall, the materials feel reliable and predictable, which is what matters. This isn’t high-end epoxy, but it’s not pretending to be. It’s a solid general-purpose polyester system with a good-grade mat that’s fine for boat hulls, roofs, panels, and general GRP repairs. If you’ve used random no-name eBay resin before and had problems with curing or weak laminates, this feels like a step up in consistency without getting fancy.

On durability of the repairs, so far I’m happy. The boat hull patch has been in place for a while now, including a couple of launches and recoveries where it gets some scraping and pressure. No signs of cracking or delamination yet. When I tapped around the repair with a screwdriver handle, it sounded solid and consistent with the surrounding original laminate, which is a good sign. The roof patch has survived several heavy rains and some decent wind without flexing or showing any weird lines or micro-cracks.

The cured resin sands like you’d expect: hard but not brittle. It doesn’t crumble on the edges when you feather it into the original surface. I drilled a couple of holes through one repair to refit hardware and the edges of the holes stayed clean. If you’ve ever worked with cheap resin that chips around drill holes, you’ll know how annoying that is. This stuff behaved more like the better-grade marine resins I’ve used before, which is reassuring.

As for storing the leftover kit, that’s always a question with a 10kg bundle. I kept the unused resin tubs tightly sealed in a cool, dry spot in the garage. After a few weeks, it was still fine: no obvious thickening, no weird skin on top. The catalyst bottles are small enough that you can keep them in a safe, upright position and just make sure the caps are tight. I wouldn’t buy this size if you only need a tiny repair, because once opened, polyester resin does have a shelf life. But for a series of projects over a couple of months, it makes sense.

Long term, the real test will be years of UV and water exposure on the boat and roof, but based on how it’s cured and how it feels under load, I don’t have any immediate concerns. It behaves like a sturdy, general-purpose GRP repair. If you prepare the surface properly and don’t cut corners on layers, it should last. If you half-sand, slap some resin on and hope for the best, no kit will magically stay perfect, and this one is no exception.

In actual use, the workability is decent. At around 12–16°C in my garage, I was getting roughly 15–20 minutes of good working time per batch at around 1.5% catalyst. That gave enough time to wet out the mat and sort out air bubbles without rushing like mad. If you bump the catalyst up, it kicks faster, but I wouldn’t get greedy unless you’re working in colder conditions. The gel and cure curve felt pretty standard for polyester – nothing weird like sudden flash curing or staying soft for hours.

Mixing is straightforward: resin in a tub, catalyst measured with the syringe, then stir well. The syringe is actually more useful than it sounds. It makes it easier to do small batches accurately, which is key with a big kit like this. You really don’t want to mix a huge pot and then watch it smoke and harden in the container. I mostly stayed under 300g per mix, which kept the exotherm under control and meant I didn’t waste resin.

In terms of handling, the resin isn’t too thin or too thick. It soaks the 450gsm mat without running everywhere, but you still need to be careful on vertical surfaces. Using a laminating roller would help, but I managed with just disposable brushes and a bit of patience. Air bubbles weren’t a big issue; any that showed up were easy to chase out while the resin was still workable. Once it gels, you’re done – it doesn’t give you a second chance, so timing matters.

The only real downside in performance is the usual one with polyester: strong smell and sensitivity to temperature. You absolutely need ventilation and a mask, especially if you’re working indoors. Also, if your workspace is cold and damp, expect longer cure times and be patient before sanding. That’s not unique to this kit, but it’s worth mentioning. Overall, performance-wise, it behaves like a reliable, predictable polyester system, which is what you want when you’re halfway through glassing a hull.

The kit is pretty simple, which I like. You get 10kg of polyester resin, split into 2 x 5kg tubs in my case, two 130ml bottles of MEKP catalyst, a 10m x 1m roll of 450gsm chopped strand mat, and a small syringe for dosing the hardener. No fancy extras like rollers, brushes or mixing tubs in mine, so don’t expect a full builder’s toolkit. You’ll need to have your own basic gear ready: brushes, rollers, mixing cups, stirrers, gloves, mask, the usual.

The chopped strand mat is proper 450gsm, not flimsy stuff. Each layer builds decent thickness, and for structural patches I was stacking 3–4 layers without it turning into a soggy mess. The roll is long enough that you can be generous with overlaps and still have plenty left for other jobs. For context, I did: about 1.5m of boat hull repair, a roof patch roughly 1m x 0.5m, and a few smaller bits, and I still had mat left over.

The resin is Lloyd’s Register approved, which basically means it’s acceptable for marine work. I’m not going to pretend I did lab tests, but in practice it wets out the mat well and cures to a hard, tough finish. No weird tackiness when mixed correctly. Gel time felt pretty normal: around 15–20 minutes working time at about 15°C with a sensible catalyst ratio. If you’re used to standard polyester laminating resin, this will feel familiar.

In terms of overall package, it’s aimed at people who already know what they’re doing. The syringe is handy for getting the catalyst roughly right, but you still need to understand percentages and not just wing it. If you’re expecting a super hand-holding kit with step-by-step photos and lots of accessories, this isn’t it. If you just want a big, straightforward bundle of resin and mat that behaves as expected, it’s pretty solid.

On the boat hull repair, I ground out the damaged area, feathered the edges, and laid up 4 layers of the supplied 450gsm mat with this resin. Curing took a bit longer than ideal because the garage was cold, but after leaving it 24 hours it was rock solid. After a week, I sanded it back and there were no soft spots or weird bubbles. The laminate felt strong and took drilling and sanding without chipping. That’s exactly what I wanted: no surprises, just a solid patch.

For the fibreglass roof repair, I used larger pieces with 2–3 layers over about a 1m x 0.5m area. Again, wet-out was easy once I got the hang of the right amount of resin. The mat didn’t float or slide around too much, and once cured, the roof felt stiffer than before. It’s been through a few heavy rains now with no leaks showing up. Obviously long-term weathering will be the real test, but so far it’s behaving like any decent fibreglass repair should.

I also used some leftovers to reinforce a trailer corner that had cracked around a bolt. Just a couple of smaller patches, and it cured just as well. No hairline cracks appeared after tightening the bolts back up. What I noticed across all three jobs is that, as long as I respected the mixing ratios and temperature, the cure was consistent. No random tacky areas, no uncured patches. When I messed up a batch once by adding too little catalyst (my fault, not the kit), it just took longer to harden rather than staying gummy forever.

So in terms of effectiveness, it simply does what a general-purpose fibreglass kit should do: strong, hard repairs that can be sanded, drilled, and painted. There’s nothing fancy going on, but that’s fine. If you’re after something for structural boat work or serious body repairs and you know how to prep surfaces properly, this kit is very capable. If your prep is lazy or your ratios are random, no resin kit will save you, including this one.