oppps theres a two holes in my fiberglass fuel tank

After the tank is fixed, you might re-locate and re-drill the holes in the fins. Maybe then you can put them where you want without problems.

 

I'm still unclear as to whether the bottom of the built-in fuel tank, and the bottom of the boat, are one and the same. If they are, I'd be looking at rather large, stainless, closed, blind rivets as a possibility, You'd need to talk to a specialist fastener supplier as to availability. Especially if you could get inside the tank to position a decent stainless washer as a backing plate.

 

Looks like the fuel is indeed contained by hull and sole.

 

This is exactly why in the USA (EU, and Canada as well) integral fuel tanks on gasoline powered boats are prohibited. Non-integral tanks are far safer and there is not the risk of a spill. I would echo the suggestion that you get rid of the integral tank and install non-integral tanks.

Also I might add that fiberglass is not a good material for gasoline tanks. There have been significant problems with fiberglass tanks leaking. Some of the components of gasoline are destructive to resins used in fiberglass. Gasoline (as I'm sure you know) is an excellent solvent.

 

It depends on the resin used, isothalic polyester seems OK.

 

Well looks like its been two years. About one year after this discussion I got the fuel tanks holes fixed up by someone who knows what they are doing. I'm yet to fill the tank.

 

Hopefully they used a resin that won't dissolve.

 

Yes hoping the same. I must admit I rang about 5 others - they all said the same thing, never came across it and said they're not sure.
The guy I went with when I first told him said the same thing and was very honest. I have seen his work before. He said he would ring a few company's up suppliers etc to find the best stuff to use.

So he went from the top of the tank cutting a rectangle to get to the holes and patched from the inside then patched his hole he cut out I think if i remember rightly he braced the top section from inside the tank not sure how he managed that but i do know where he patched from outside is stronger to stand on then before. Hopefully I shall have the boat on the water within next month.

 

OP, I hope it all works out for you.
I used to build production yachts, one of the guys on fitting out decided to start on the latest boat by cutting all the through hull fitting with a hole saw.
It was still in the mould.
**** happens.
Fine yourself a top shelf bottle of rum and carry on.
And thanks for an entertaining read, some of the replies were as good as the op.

 

Geepers thats no good makes me feel a little better. So he cut through the mould aswel?


Hahaha Rum I'm not a drinking I laugh because I'm a little man and no drinker if I had even just a nip of rum there would be holes everywhere hahah.I like your comment.As I say to people I'm silly enough without the drink.

I finally fitted the fins.I re drilled the holes in the back fin so not to re drill through the fuel tank.I re enforced the hull from the inside with more layers of fiberglass(it may have not done anything for being re enforced but it doesn't matter anyhow because it was solid anyways)but I guess I did learn a little about laying fiberglass (patching). I used flowcoat over top.Now I'm not sure if its chemically bonded or something else but looks alright to me hahah. If someone asks what did I use. Well I cant remember haha.I also used stainless bolts and nuts washers.And made A ski pole bracket.I'm not the best welder but I have a go.I asked for some advice about the ski pole bracket on a facebook welding site and one guy said what are you going to tow the rubby princess hahah I found that funny.
I shall get some photos sometime of how it all turned out.Or a video.