repairing hole in bottom of boat

[Strahm]

I just got done painting my fiberglass boat, while painting i had it sitting on 4 4x4 posts. one of the posts broke the hull some.
if you could picture the outline of a 4x4 post on a boat, half of that broke through.
my plan is to cut out the damage so it doesnt crack further, then sand the area around the hole just to rough it up. then start with small pieces of fiberglass mat, and slowly get larger and larger pieces. and make the repair area atleast 3 times the size of the damage and make sure i apply a bunch of layers, so it will be strong (and ugly, but dont care)
i dont care what it looks like as its the bottom of an old boat, i just want it to be safe, waterproof, and strong.

will this be a suitable method? i know it would be better to go from the backside but that would require me cutting a hole in the floor of the boat, then repairing that hole which is counterproductive especially when i dont care how the bottom of the boat looks.

also what is wrong with using polyester resin as compared to epoxy?
the resin says on the bottle, safe for all applications including boats, and 100% waterproof. I already have a gallon of polyester resin so i would like to use it if its possible.

 

[GT1000000]

Re: repairing hole in bottom of boat

I just got done painting my fiberglass boat, while painting i had it sitting on 4 4x4 posts. one of the posts broke the hull some.
if you could picture the outline of a 4x4 post on a boat, half of that broke through.
my plan is to cut out the damage so it doesnt crack further, then sand the area around the hole just to rough it up. then start with small pieces of fiberglass mat, and slowly get larger and larger pieces. and make the repair area atleast 3 times the size of the damage and make sure i apply a bunch of layers, so it will be strong (and ugly, but dont care)
i dont care what it looks like as its the bottom of an old boat, i just want it to be safe, waterproof, and strong.

will this be a suitable method? i know it would be better to go from the backside but that would require me cutting a hole in the floor of the boat, then repairing that hole which is counterproductive especially when i dont care how the bottom of the boat looks.

also what is wrong with using polyester resin as compared to epoxy?
the resin says on the bottle, safe for all applications including boats, and 100% waterproof. I already have a gallon of polyester resin so i would like to use it if its possible.

Best way for the iboats gang to help you is by posting some pics of the damage...get a free photobucket account and upload your pics, then click the IMG tag and post here...


From the get go, it seems like you have fairly good grasp of what needs to be done...and if you do it right, it might not end up all that ugleee!

Just make sure you use the right combination of fiberglass mats/cloths...

And there is nothing wrong with using polyester resin, as long as that is what the boat was originally constructed with...

 

[ondarvr]

Re: repairing hole in bottom of boat

Polyester is fine, there is no need for epoxy.

DO NOT cut out the broken piece, just pull it back into place.

Getting at it from the inside would be better, but it can be done from the outside. Leave the broken piece in place, sand an area about 10" or so bigger on each side of the hole. Check to see how thick the hull is and make the patch slightly thicker. Start with mat and then a layer of roving or 1708, repeat this until you at least match the thickness of the hull.

 

[Strahm]

Re: repairing hole in bottom of boat

the reason i was going to cut the damage out is so the cracks do not keep going further. I also thought about drilling a hole at the end of the damage, but i figured since it is a crack all the way through there wouldnt be much to stop it from continuing in any direction.
sounds like my general idea will work though, i just wanted to make sure there wasnt some "sin" of using polyester, and patching on the bottom.
also how would i know what the boat was built with? its a 1973 strahm bass boat. the bottom seems to only be about an 1/8"-1/4" at most thick (atleast where this break is, on the edge of the bottom)

 

[Woodonglass]

Re: repairing hole in bottom of boat

Your boat is made from poly. You must sand the area to be repaired all the way around at least 4-6" back and feather it down towards the center to almost nothing. As ondarvr suggest, do not remove the piece. Use csm and make your patches progressively 1" larger than the previous like the rings on a shooting target. If your resin has wax in it you must lay up all of your patches at the same time or you will end up with a weak bond. I suggest precutting them all and wetting them out an the patch area all at the same time. My layup schedule would be...first two layers of CSM layer of 1708 Biaxial, another csm, 1708 and final CSM. This should get you back to the level of the hull thickness. Sand and fair and if you want brush on a little gelcoat to hide it and you're good to go. Should take no more than an hour to do this repair.

 

[Strahm]

Re: repairing hole in bottom of boat

thank you very much, you made all of my uncertain thoughts more clear.
the only thing i am still worried about is if the crack will continue, if i don't make a clean cut somehow. i have always heard to either drill a hole at the end of a crack, or cut out the damage. seems that every other writeup says to do this...

 

[Woodonglass]

Re: repairing hole in bottom of boat

Post a pic. Drilling a hole prolly won't hurt anything. You can fill it with resin.