First time patching gelcoat, couple questions

[void7910]

So my seadoo with fibreglass hull had a quarter size chuck out of the gelcoat around the intake. Previous owner had tried to rtv the chip back into place. Anyway decided to take a crack at patching it with new gelcoat, first time, upside down, on my back, across curved surface. Anyway. It’s patched and sanded down and watertight. Just not super pretty. Had a couple questions to figure out how to improve next time.

The two different colours are because my first fill had a big depression in it and a large air bubble so I had to do a second coat. Both could have used a lot more colour. Don’t really care about looks though as it’s under the waterline.

1) my biggest question is, is this watertight, protecting the underlying glass? It’s completely smooth, no exposed cracks or chips I can catch a nail on albeit a bit thin in places.

2) I have large white flake in my new gel. Top left in pic, by finger. it’s level with the surface so I don’t think it’s a chip. Any ideas? Resin that didn’t get mixed with colour?

3) I have some porosity presumably from air bubbles. I hand mixed in a cup. How can I avoid these next time?

4) I clearly sanded too much because you can see the edges of the original chip. Any tips for sanding across a rounded surface like this? I used a tiny sanding block I cut from 1x2.

Thanks all. And yes I know it’s amateur hour.

 

[FunInDuhSun]

Looks like air bubbles inside. Did you lay on any mat, or just fill with resin?

 

[void7910]

Looks like air bubbles inside. Did you lay on any mat, or just fill with resin?

I didn’t think it was that deep, so I just filled it with resin. Maybe a mistake?

 

[FunInDuhSun]

Well without mat, the resin can chip very easy. The mat gives it strength.

 

[todhunter]

For your first chip repair, I think it's fine. I can't really tell too well from the picture, but if you're worried about it not being water tight, use a dremel with a sanding drum and dig out the area a little which has the chip, then go at it again.

Here are some of my tips:

• Use a dremel to grind out the chip a little bit deeper and grind the area a little bit past where the edges of the chip are. This helps rough the surface for a good bond, and it lets you put in more gelcoat.
• Before catalyzing or thickening, add your tint to the gelcoat. You can put a piece of tape beside the repair area and put on a little bit of uncatalyzed gelcoat and let it dry to see how the color looks. Adjust your tint until you're happy with the color.
• Add catalyst and stir for 1-2 minutes, trying to not fold in extra air.
• Add cabosil to the gelcoat to thicken it to the desired consistency. You can make it a very stiff paste that will hold in any position.
• The trick for sanding around a round surface is using a sanding block like you did and to go slow. I like to put 1 layer of painters tape around the repair area when doing my rough (dry) sanding - this way if you go outside the repair area, you're sanding the tape and not the good gelcoat. Once you have the shape correct, the repair area is too tall (by the thickness of the tape), but you now switch to higher grit papers and wet sanding. As you get the repair area down to being the correct height, you should be around 400 - 600 grit. Now you can start fairing the repair into the surrounding gelcoat. Keep working up the grits, wet sanding slightly larger and larger areas. If done right, once you buff and polish, it will all blend in together.