Patch Aluminium Dinghy with Fibreglass?

[abrogard]

How about that? Anyone know? Would it work?

The dinghy is an old Aluminium De Havilland and the seats and stiffeners were rivetted to the hull. And the keel. These are the main problems, the rivets start and seep or even fall out and create a hole to let the water in.

I have been drilling out bad rivets and filling the cleaned hole with steel reinforced epoxy resin. And I've also got some 'Sikaflex', well known to the boating fraternity. It is a polyurethane sealant much used by them. Some suspect rivets I've simply wire brushed around and then bogged with it.

The steel epoxy I saw a quick mention of in one boating forum where they said don't use it because it doesn't bond well to the aluminium. And I see at least one of my fixes seeping water today when I looked. (The boat hasn't even been back in the water yet since I started fixing leaks . That water was seeping outwards, not inwards, from water I poured into the hull).

So I'm dubious about it.

The Sikaflex might be a mighty product but it is softer, more like your car windscreen sealants, and it will wear easily I feel and the hull gets dragged up the runners of the trailer every time it is in and out of the water.

So I suddenly thought of maybe fibreglassing along the whole line of rivets, right across the hull. Maybe six lines each about 70mm wide.

But I've never done any. I don't know how well it bonds to aluminium. I assume it handles water alright because there's so many fibreglass boats. How well it'll stay bonded with the flexing and movement of the substrate I don't know.

Any ideas?

[Deepsix]

It isn't a good idea. Even epoxy won't be a success, I have seen attempts to epoxy over pin-holed corroded aluminium boats, and it did not last, but the corrosion sure kept going, or accelerated, with 'poultice' corrosion. If it is below waterline, don't trust any such remedy.

[thrillseeker]

G'day abrogard, looks like that bloody boat is still giving you grief.

The rivets are there for a reason. They allow limited movement at the joint between the seat and the side panels because that area is subject to flex.
If it were a rigid joint as in welding, fatigue or constant twisting of the hull would make the weld crack and the situation would be much worse.

That is also why rigid epoxys and fibreglass are a failure.

My suggestion is to drill the rivet out and simply bolt it with galvanised bolts and oversize washers(panel washers), You are in fresh water?

Galvanic corrosion is in favour of the hull, because of the zinc coating, the Al won't corrode and as soon as you see any sign of rust, around the washer, replace the bolt and washer.
Fill the area in the hole and under the washer, before you bolt it, with Silastic and that will act as a flexible gasket and allow the hull to flex.

[nimrod]

This old deHavelland rivited punt has seen more rocks, oyster leases and sand bars than most would ever dream of in a lifetime.
About 25 years ago it had cracks around the front area, I fibreglassed the joints, ( rubbed well back and done a half decent job ) well blow me down a couple of years ago now the fibreglass started to peel off the alloy again, bamn stuff only lasted about 22 years of rough bang take it anywhere treatment that it could take, also over the years I have plugged many holes with Selleys UneadIT aqua and bamn blast it new holes and cracks keep appearing.
Guess in another 25 years or so I might have to bight the bullett and retire the old girl.

BTW with a 9.9 hp on it's rear it runs circles around my 5.3 lancer, gonna put a 15 on it's arse and see how she goes.

Frank
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Keep it wet

[Trailblaze_6.1]

Frank, if u fart in that thing while fishing, it would be close to water breaching the sides from the momentum

[chugger]

Arthur do not use anything in bolts nuts washers except 316 stainless sounds like you could have electrolis should also use a stainless wire brush as steel will promote electrolis I would also recommend to clean keel back to bare metal & install a sacrafiscal anode which will help in reducing electrolis
Chugger

[thrillseeker]

[EatMyPilchard]

Can you not drill out the old rivets and replace with new ones? Slightly larger.
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[Deepsix]

You mean pop rivets ? A temporary measure only, I think. Some old tubs get that buggered the hole could need rivets sized a la the Titanic.

[stevej]

sometimes boats are just beyond their safe working life