Removing skin fittings.

[johnphilip]

In an insurance prompted survey I was told to replace a corroded 1" brass elbow which sits on a skin fitting and before the seacock draining the sink. I have managed to remove the valve and elbow and during the operation I found the skin fitting itself was rotating slightly within its hole in the hull. The thread on the skin fitting when revealed was indeed somewhat pink suggesting de-zincification has set in and replacement is advisable. As the fitting is moving in its hole it ought to be removable without resorting to destruction but finding a spanner to turn the backnut with enough force in a restricted space has me beaten at the moment. A spanner size of 50 mm is required. A socket of this size seems to have a 3/4" drive which would involve investment in tools which probably will not fit in the space. My Stilsons fit in the locker but are too small to get adequate purchase.
Is there a tool which fits in the skin fitting from outside the hull and locates against the lugs and can be turned with reasonable force?

 

[PabloPicasso]

Is there a tool which fits in the skin fitting from outside the hull and locates against the lugs and can be turned with reasonable force?

I made one using an angle grinder to cut two slots into a socket that just fitted into the skin fitting. If I remeber rightly it was at about the ten to two position, the lugs were offset and not opposite each other.

I could then use an extension bar and grip the fitting from inside the hull. Useful as I was on my own.

On a more recent, and destructive, thru hull removal I had to drill through the backing nut to split it. I drilled at an angle so the bit missed the hull and only hit the nut and thru hull.

 

[Tranona]

Easiest way is to grind off the exterior flange. Couple of minutes work and no grovelling in confined spaces

 

[johnphilip]

Easiest way is to grind off the exterior flange. Couple of minutes work and no grovelling in confined spaces

I have never liked or trusted angle grinders I am afraid. Admittedly with bigger old machines and different blades that there used to be but I saw the results of too many building industry accidents ever to own one myself.

 

[Snowgoose-1]

I have never liked or trusted angle grinders I am afraid. Admittedly with bigger old machines and different blades that there used to be but I saw the results of too many building industry accidents ever to own one myself.

It's comforting to know that I am not the only one , despite the tool's effectiveness. In my view, only to be used by professionals.

 

[mrangry]

I have never liked or trusted angle grinders I am afraid. Admittedly with bigger old machines and different blades that there used to be but I saw the results of too many building industry accidents ever to own one myself.

A small 125mm angle grinder with a guard is a very quick and effective method of removal on the external flange allowing it to be pushed inside the boat. They are soft metal and just let the disc do the work.

If you really dont wish to use that method you can insert a suitably sized flat bar or spanner in from the outside and turn with a pair of grips, you will however need someone to hold the internal retaining nut with say a pair of pump pliers.

 

[TSB240]

If you don't like a grinder then use a carefully selected hole saws and a drill.

Get the right size and you will remove the exterior flange and some of the thread.

It is really simple especially if you plug the centre of the old fitting with a concentric bung of hardwood from another smaller suitably sized hole saw.

The bung centres the drill to allow the final cut to remove the flange and most of the thread from the exterior.

It is still easier with a grinder!

 

[lustyd]

A dremel will cut through the nut easily and quickly with considerably less mess and heat than the angle grinder on the outside. A couple of small cuts and the nut falls off then push the through hull out with your foot.
Stilsons still preferred though for least effort and mess/damage.

 

[fredrussell]

…or a reciprocating saw with a Bosch long metal blade. Cuts completely flush to the hull as blades flex. Also the best tool for cutting through and removing cutless bearings.

 

[wingcommander]

Step drill bit from outside ( cone shape taper ) , or dremel nut off inside would e my choice

 

[lustyd]

…or a reciprocating saw with a Bosch long metal blade. Cuts completely flush to the hull as blades flex. Also the best tool for cutting through and removing cutless bearings.

I'd be astonished if there was no damage at all when doing this!

 

[vyv_cox]

Bang a piece of timber into the fitting and use it for the centre bit with a hole saw that just cuts the flange close to the wall of the fitting. Probably the least likely method to cause additional damage.

 

[lustyd]

Probably the least likely method to cause additional damage.

It's messy AF though, and creates a lot of heat for the surrounding GRP which needs to be strong for the new fitting. Far better to remove properly if at all possible.

 

[Tranona]

It's messy AF though, and creates a lot of heat for the surrounding GRP which needs to be strong for the new fitting. Far better to remove properly if at all possible.

Do you have any7 scientific evidence to support this?. Neither messy not heat generating in my experience. The metal is very thin and cut through in seconds using either a grinder or a hole saw. The GRP is very thick and solid at that point and doubt the small amount of heat will have any effect at all.

Happy to be proven wrong with some valid third party data.

 

[vyv_cox]

It's messy AF though, and creates a lot of heat for the surrounding GRP which needs to be strong for the new fitting. Far better to remove properly if at all possible.

I would always unscrew if possible but it often is not.

 

[Stemar]

In my, admittedly limited, experience, if a skin fitting is in a poor enough state to warrant replacement, removal is inevitably going to involve some brutality. I tend to use a small angle grinder, mainly because I have one, with a grinding disk on the outside, simply because access is usually easier than hanging upside down in a locker, which makes a clean job a lot easier, and is a lot safer. Touching all available wood, I've never done any damage to the hull than can be fixed with a bit of filler.

PS: wear ear and eye protection. Angle grinders are loud and Metal grindings are unfriendly towards eyes

 

[ridgy]

I used an angle grinder last time and found it hard to avoid catching the hull and having to make good. I would definitely try the bung and holesaw approach next time

 

[fredrussell]

I'd be astonished if there was no damage at all when doing this!

Theres loads of damage - the skin fitting gets chopped in two! I did three metal skin fittings on my boat this way. 5 mins each. No damage to hull whatsoever.

 

[lustyd]

Do you have any7 scientific evidence to support this?. Neither messy not heat generating in my experience. The metal is very thin and cut through in seconds using either a grinder or a hole saw. The GRP is very thick and solid at that point and doubt the small amount of heat will have any effect at all.

Happy to be proven wrong with some valid third party data.

This forum blows my mind sometimes. No, I'm not going to find you scientific data that drilling metal produces heat, look it up.

The metal on mine was at least 1/4" thick and definitely didn't take seconds using either a hole saw or an angle grinder. Perhaps your boat had cheap crappy fittings.

You "doubt the small amount of heat will have any effect at all". Science please, otherwise you're just speculating. Heat from drilling is very common knowledge, whether that heat affects the GRP though, I'd want something better that "Tranona reckons"

 

[vyv_cox]

This forum blows my mind sometimes. No, I'm not going to find you scientific data that drilling metal produces heat, look it up.

The metal on mine was at least 1/4" thick and definitely didn't take seconds using either a hole saw or an angle grinder. Perhaps your boat had cheap crappy fittings.

You "doubt the small amount of heat will have any effect at all". Science please, otherwise you're just speculating. Heat from drilling is very common knowledge, whether that heat affects the GRP though, I'd want something better that "Tranona reckons"

I cannot offer any science but my experience is that cutting with an angle grinder generates considerably more heat than a hole saw. You could lubricate/cool with a saw but not an angle grinder I think.