Pin Hole in boat

[Beekee]

Hi
Was wondering if anyone can give a bit of advice. I have had a bit of corrosion happening on the bottom of my boat for awhile now where it used to sit on the skid. The skid had carpet on it originally till I replaced it with teflon. This must have started the corrossion. I have since replaced the trailer with a multi roller which was a big improvment. Have watched this spot for about 7 years now and it finally broke through the 6 mm bottom. The boat kept getting water in it so filled it up and sure enough it came out of this spot. Has anyone used the product called Aluminox or Kneadit. It would be easy to put one of these into the hole to fix it. If I get it welded it may require a major job to remove fuel tanks etc. Have used the product Kneadit on one of the fuel tanks and it lasted for about 5 years till I got it welded when I did a refit. That was a good product but would like to hear from any other peoples experiences.
Thanks

[gofishin]

Sounds like it can be easily welded from the outside without worrying about the tank(s). Drill the hole out & light grind/sand, use a metal (steel) backing plate on the inside (prevents heat/weld penetration inside the hull, alloy welding does not penetrate it - assuming you can get behind the hole) and a quick zap with the MIG, then a quick grind/sand to tidy up (shouldn't even need a touch-up with the TIG before grind, but your welder will advise). I wouldn't bother with Kneadit etc, could present problems under water as it would have different alloy component hence galvanic corrosion.
cheers

[SNAPPERCOFFIN]

If your going to get it welded up dont put any quick fix products on as it will make it hard to weld later.

[Beekee]

Thanks Gofishin.
That was a concern that these putties amy have some dissimilar metal conponents and hence set up more electrolysis. I may finish up with a bigger hole than I already have and a bigger problem at sea.

[tunaticer]

Is this hole accessible from the inside? If is it I would get it welded up as it should be quite easy to drill out the corrosion area and weld it up esp being 6mm plate. If it is not accessible you could drill it and place a capped blind rivet in there to stop the leak but it will be a short fix until you intend on getting it welded. Alternatively you could also acquire a peen rivet that is peened tight into a drilled hole and basically you will not have to get it welded up. All boats used to be peen rivetted many years ago.

[Beekee]

Tunaticer
It is not accessable from the inside but it could be welded from outside. I am just concerned that some guys may not want to weld it with the fuel tanks in. May need to find someone that likes to live on the edge.

[Moonlighter]

Beekee

I used kneadit some years ago on an old alloy hull and you used to be ale to get an "aqua" version that was suitable for use underwater. Had the boat for 4 or 5 years after that and had no problems at all.

Although I do agree with the others it would be best to get it properly welded up.

I also agree with you that it may be "challenging" to find someone who will weld anywhere within cooee of a fuel tank!! I did have some mods done to my JBS plate boat a couple of years ago and I had to remove the fuel tank before the welders would start the job - a bit of a job but not a huge hassle, and also gave me the opp to check and replace fuel lines etc whist I was there.

[sharkymark2]

I used to refrigeration goo on my aluminum pipes in the fridges I repaired; the stuff is little short of incredible. Bullet proof ...almost. There also is an epoxy called green stick which is suited to aluminum and just needs a little heat to melt the stick onto the hole ...both fantastic.

[FNQCairns]

I am pretty sure all of those 'kneed it' type products are epoxy I used it once on a new radiator I had fitted when they over stressed the position of some attached lugs on the top tank so they soon failed, almost cooking the engine, roadside at a servo I cleaned and sanded the immediate area to obtain maximum surface area for adhesion then used a kneed it product, kept the cap unpressurised for the rest of the 750km trip then presurized it, actually I sold it like that 10 years later..... also used it on a dripping fuel tank when a tailshaft let go and gashed it, 5 years later back then and never a related problem....I think the kneed it will be all you will ever need, the hull alum is too thick for the spot to cause a point source for a stress fracture i assume, you just need to fill the hole and feather the product around a little so some rough sanding to create a chamfer like perimeter might be worth while.

cheers fnq

[Moonlighter]

A thought based on experience: there might be a reason why the hole has appeared there!

I had a similar problem in my current boat and we found that the hole/corrosion causing it was due to a weld where a floor support brace was welded to the inside of the hull - must have been a bad weld and that's where the corrosion started and eventually, as you have found, you get a pinhole and leak. When you grind/drill out the pinhole you could be surprised how big it gets - I found a hole the size of a 10c piece!

So what I found was that although we welded up the hole, we soon had a leak again because there was weight on that spot from the inside support brace which was now not welded securely, and the only solution was to cut open the floor and fix it first from the inside then from the outside.

This sounds drastic but not really that big a deal in a plate alloy boat.

ML

[bigjimg]

Gidday
Maybe a bit of electrolosis going on.I would take it that the battery/ies are
isolated?Not withstanding the other comments made here, an anode or two extra on the hull wouldn't go astray.Jim