Hi Mark Corke here from BoatUS Magazine. Today I'm going to show you how to repair spider cracking in gelcoat. Before I start, don't forget if you find this video useful give us a like below, add a comment, and don't forget to subscribe to our YouTube channel. Before we start doing any repairs, I've got to make sure that the boat's nice and clean. I've already washed it down but my next step is just to give it a good wipe down with some acetone just to remove any remaining contaminants.
So before I do any work to the actual gelcoat itself, I'm going to mask it off so that we don't get splashes and things on the rest of the boat. [UPBEAT MUSIC] Just painting on some gelcoat is rarely effective so what I'm going to do is I'm going to open up the cracks with my Dremel tool and that will give the gelcoat something to bite into and also give us a much better repair. [GRINDING] I've finished the grinding, and if you look carefully you can just see that I've gone down through the gelcoat and barely scraped the laminate underneath. That's because we don't want to make huge gouges we just want a very shallow ones just for the gelcoat to have something to bite into I get a lot of questions about gelcoat and you'll notice that this is Spectrum Color. This is just one manufacturer that makes gelcoat.
They come in loads and loads and loads of different colors. This is obviously Grand Banks white because I'm working on a Grand Banks, but whatever boat you have they can probably match it up to suit. Because this is a huge gallon can of gelcoat, I find the easiest way to decant it is to use a syringe, so I'm going to suck up a syringe full of gelcoat and then I'm going to squirt this into a paper cup. One thing that many people do is they mix up way more gelcoat than they actually need. You'll see how much I've got in here.
It's not a great deal and this is plenty to fix this crack and more. Follow the manufacturer's instructions when it comes to adding the catalyst. But you won't need much of this a lot of people overcatalyze.
They put way too much in there. So for the amount of gelcoat I've got in there, two drops is going to be plenty. I'll have to mix the catalyst well into the gelcoat, and remember that we don't have a lot of working time. And talking about working time, it's good to remember that you really want to do this on a fairly warm day.
You shouldn't do this when it's a frost or really cold temperatures because it won't go well. The next thing I've got to thicken the gelcoat and for that I'm going to use colloidal silica. It's very, very fine lightweight powder and it's ideal for this, but make sure you do wear a respirator when you handle this because it's not good to breathe. So with the thickened gelcoat I can now start pushing it into the cracks.
And you see because it is thickened, it doesn't run everywhere. So I'm putting a little bit on there–there's way more than I need. And what I find helpful, just to smooth it down, is to use an old credit card or, in this case, an old AARP card Well, there we go.
So now I'm going to leave that overnight to harden and we'll come back tomorrow and clean that off. Welcome back! It's day two, and you'll see that this is set up nicely.
It's cured. One of the things I want to tell you about now is waxed versus nonwaxed gelcoat. That's something you hear a lot of. I used waxed gelcoat and that's why this is not sticky.
Had I used nonwaxed, this would still have remained sticky. You can use either. If you use nonwax, you either have to cover the repair with some mylar or some sticky tape or something, or you can spray it with PVA.
Either will work. But you need to cover the surface with nonwax, so that it'll set up. It's looking pretty good, but I've got to sand this down flush with the surrounding gelcoat. But before I do that, I'm going to remove the masking so I don't pick up the blue tape and rub that into the repair. [UPBEAT MUSIC] With the masking removed, the next thing is to sand this down flush with the surrounding gelcoat, and for that I'm using 220 grit wet and dry paper used wet so it lubricates itself.
And it's going to sand down. You don't need to go mad with this, and you'll be able to feel and see when it's flush. You'll notice that I'm using a block of wood and the reason for that is that I want to keep the repair nice and flat and flush.
If I were just to use my fingers like this. I'll end up putting ridges in the gelcoat. I'm going to swap from 220 grit, which is what I was using a minute ago, to 400 grit, which is much smoother and then that way that will take out any scratches that were left with the earlier paper. So as in the previous steps I'm using the 400 grit paper wet, too. I know I'm ready to move onto the next stage, which will be using the rubbing compound, when I can feel the block actually start to suck down onto the repair because I know it's nice and flat.
If I take that off, look, it'll actually stay there. So next just wipe the repair down with a nice clean rag just to get any residue off. So the next step is for me to use some rubbing compound.Tthis is essentially paste abrasive which is even finer than the 400 grit.
What I do is I squirt some onto a rag and then I'm gonna rub it in. You don't have to go mad; I'm just gonna put it on the surface. And now I'm going to buff that out with the polisher. And I'm using that about 1,600 revs per minute just to buff out this paste. [BUFFER NOISE] So with the compounding out of the way the next thing is to use a glaze. We've had loads of questions about this, and glaze is essentially a polish.
But it's just a very, very, very fine abrasive. And this will give me a nice shine prior to applying the wax. With the glaze applied to the surface of the gelcoat, I'm going to use my buffer one more time just to polish that out. [BUFFER NOISE] The last and final stage is to apply a good wax polish. I'm putting this on here.
I'm gonna rub it on here just to cover up the glaze and protect the shine. You'll notice I'm using a different applicator pad. These are the wax polish applicators you can get from any auto store.
And the reason for that is that they actually give a far better polish and just using a terry towel. The last and final stage is just to buff it out one more time. Though you can't see this here, but I've actually reversed the buffing pad. On this side we had the compound.
This is nice and clean, so this will give me a nice smooth finish. [BUFFER NOISE] So there you have — it a nice, seamless, smooth repair. Don't forget to check out our other gelcoat repair videos on our YouTube channel. Thanks for watching and we'll see you on the water. [WAVE SOUNDS]