How do I remove this rough fiberglass patch job?


The previous owner slapped a piece of fiberglass on the keel and didn't bother to sand it at all.

Any ideas on how to remove it? I have been successful with a heat gun and razor blade but some areas are too thick to remove.


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Harbor Freight has a free $4 prize just to "show-up" today.

Pick up their $9 grinder and a mixed packet of grinding/sanding tools. $6?

Grind the center thinner, then heat and pry the patch away.

The patch appears to have covered untreated paint, so it should yield at the paint/patch boundary.
The previous owner slapped a piece of fiberglass on the keel and didn't bother to sand it at all.

Any ideas on how to remove it? I have been successful with a heat gun and razor blade but some areas are too thick to remove.
Looks to me like that pseudo patch might pop off with a fingernail? Or a putty knife?
CONGRATULATIONS! That ,ight be the longest, certainly the thickest patch we've seen. What do the rest of The Usual Visitors thin?

We'd try the methods mentioned above. We've used 40 grit on a random orbital sander. Or an oscillating multitool to remove excess patch. Possibly a foot adze or mini excavator :)

Old patch.jpeg

Patch removal heat gun.jpeg

The trick is to go slow with any method in order to avoid damaging good parts of the hull.


Move the boat outside if you can, a lot of fiberglass and resin dust/fumes will be created. Wear P95 dust mask, safety glasses, long sleeves, gloves,long pants = cover all skin and go rinse off as soon as you're finished. Stand upwind of dust and fume cloud.

If you go the heat route, have fire extinguishing method nearby, as you can set a boat on fire...ask us how we know...there could be stray bits of interior foam or old, dry wood bits inside that make excellent kindling. For our boat VIPER a wood batten from a previous repair started smoldering, we used a damp towel to cool it off.

The heat gun does not stop at heating just the patch resin, it will soften the hull resin as well...ask us how we know.

Old patch removed.jpeg

You'll be priming and fairing before you know it!

Kent Primer VIPER.jpeg

Our tradition, if we spill paint, is to make Sunfish art. We're curious if the folks who bought our Florida place left it?

Spilled Paint Floor Art.jpeg

We (I) spill a lot of paint, sometimes on purpose.

VIPER became our most spoiled restoration, his new Skipper sailed him all over Choctawhatchee Bay, with frequent lunch runs to Okaloosa Island.

Viper Okaloosa Island 2.jpg
I am humbled by the size of your resin patch compared to mine.

Yes , it started to smoke a little with the heat gun. Got a wet towel on it right away.

I removed two thirds of it but what's left is thick and very hard.

I will have to grind what's left. Yes, slow and careful.

Nice sail on your boat. I didn't know you could get a sail like that. ha
Usually not well bonded as said. Heat and whatever works best. Some place might have more bonding then others. The vibrating tool with a putty knife is a good option, but it gets tough around the bend.

I have grinders and a DA electric sander. The DA sander has been my goto lately with 80grit and 120 grit. To me 60 grit is a bit too course and for around the bend and wanting to be surgical and just getting the glass off I would tend towards the 120 grit by machine. But stop short if getting every thing off and hand sand with 80.

For a proper repair you will need to rough the surface to the proper grit and feather the edges.
No, its like concrete where its thicker. Even the heat gun doesn't work on the third of this patch still on. I'll have to start gently grinding
If the glass is well bonded then you should not be able to remove it with heat. Sand it off is the only way.

Take note of what does come off easy and why. When you go to do repairs make sure you dont repeat those mistakes. That is how I have learned and why I frequently comment on glassing. I see others making those errors that failed on boats I have seen.
Nothing like a 4-1/2” right angle grinder and flap wheel with 60 grit. (Home Depot) Keep a light hand and don’t go too deep.

Found this one in Bequai, Grenadines. It’s still there.


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