Fiberglass question

Hey, I am new to fiberglass repair and there is a crack on my bow but I can’t get at it from the inside due to the ballast. Does any one have any tips on how to fix the fiberglass from the outside only?

Thank you

I was actually just looking up product to fix spiderweb cracks earlier but I think that an idea of the extent of the damage is going to be needed for guys to give the best advice on fixing it.

Well. it is a flotation tank, not ballast, but a photograph would be helpful.

You can certainly apply any number of patches from the outside of the canoe.

Yes you are right, should have posted a photo.

I have already removed the cracked glass with my grinder.

You might want to watch some youtube basic fiberglass work videos.
That is a lot more than I was researching how to repair, but it looks like a nice clean area that you should be able to patch like new.
Fiberglass is pretty easy to work with. I don’t know but to me I would think that some spray foam that could be shaped to lay the fiberglass over would make things easier.

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First of all, are you absolutely sure that the entire area of damage is below the level of the flotation tank? Take a good look under the deck plate.

There are two different types of flotation tanks in composite canoes: open top and sealed. In a sealed tank, the top of the tank is closed and the tank is empty. The air in the tank serves as the floataion. In this type of tank, there is often a small rubber plug with a tiny hole in it to allow for equalization of pressure in and out of the tank. If that is the type of tank you have, be aware that you may no longer have an effective float tank since it is breached.

In an open top tank, the tank is not sealed but filled with some type of lightweight foam material that serves as flotation. If that is what you have you may be able to work down inside of it but you would probably need to remove your deck plate by drilling the heads off of the rivets holding it in place and then later pop riveting it back in place. You would also need to pull out some of the foam to effect the repair, but that could later be replaced.

If you have a sealed tank and the hole is below the top level of it, I would try to create a shaped form out of a block of some type of foam material that conformed to the shape of the missing portion of the stem. Minicel foam can be easily shaped and that might be an option. When you get something that is close to the shape of the missing piece of boat, you can cover it with saran wrap or polyethylene plastic and lay a couple of layers of fiberglass cloth over it. Once the epoxy cures, peal the fiberglass form off and trim the edges so that they slightly overlap the edges of the hole in the boat. This form will not provide any strength, just a back stop for your repair.

Bond that form you made to the edges of the hole with epoxy. Once the epoxy cures, sand the junction smooth and then lay around three layers of 6 ounce/square yard fiberglass cloth over it. You want these patches to be of concentrically different sizes and the largest should overlap the sound hull by at least two inches. Cut the patches so that the lines of weft and weave run at different angles to each other.

If you don’t think you can fashion a mold of the missing piece of hull, you might go to the Auto store. They sell steel mesh in flexible sheets that are used for repairing holes in auto bodies with bondo. You could try to make a convex form out of that and epoxy it to the margins of the hole in the boat. You wouldn’t get an exact shape, but perhaps close enough to start laying cloth over it.

If you have a sealed tank and alternative would be to remove the deck plate and actually cut a hole in the roof of the float tank big enough to work through. You would then need to rebuild the roof of the float tank to seal it. But most of that repari would probably be hidden by the deck plate.

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Thank you pblanc, that is very helpful. The hole is fully below the sealed tank. Those are good options and I will have to look around my small town to see which one is more viable for me.

I’m guessing the mesh steel will be the easiest to access.

Hope to have this fixed up in the next couple days.

Anything that you can use to fashion a scaffold that approximates the shape of the missing portion of the canoe could work. It only has to be strong enough to support the first layer of cloth. Depending on how much time you want to put into it, you can get the shape pretty close to the original by using additional small patches of fiberglass cloth to fill in the low spots. Wait till the epoxy cures and then sand off the high spots.

If it is hollow, and you don’t mind adding about 6 ozs. of weight to it, you could fill it with expanding foam. Then shape it to match and glass over it. Check the manufacturer’s(of the foam) to see if epoxy damages it, if it does, put a layer of saran wrap over it, packaging tape will also work. Sand and paint it when it is finished. Three layers of six ounce glass would be enough.

I knew someone would suggest the expanding foam. I would not recommend this. A sealed flotation tank needs some mechanism by which the air pressure within the tank can equalize with ambient air pressure, which is very dependent on altitude, barometric pressure, and ambient temperature. I doubt that the expanding foam would completely fill the flotation tank without trapping air pockets within it. If that were the case, trapped air pockets might have no means by which to equalize which could cause the sides of the hull and tank to expand outward or suck in. The interior walls of float tanks are not always that strong, because they don’t need to be. I would be concerned that expanding foam could damage the walls of the tank or cause separation of the joint between the hull and the tank walls.

It would be pretty hard to get enough air volume in there to cause such problems. Especially since it was a sealed flotation tank to begin with. Anything that replaces any air volume in it would reduce the chance of that happening. The types of foam sold by Jamestown dist. or fiberglass stores stores will not damage tank or cause separation. The polyurethane formula of those is capable with the polyester used to build the boat.