Cutting Out Existing Skin Fittings, What Tool?

CaptainBob

CaptainBob

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Biting the bullet and replacing a bunch of skin fittings. Easiest way by far will be to cut them off inside, flush with hull - they're all glassed in on the inside.

Could I use an angle grinder for that? I have a cheap one I use for sanding - I could get a metal cutting disc for it maybe?

Other suggestion(s)?

TY!
 
Not sure I understand the glassed in bit. They should be tightened down on bedding compound and with a backing pad if I recall best practice?

I cut some off from the outside with a router and an old knackered router bit. Wear eye protection! The router bit was even more knackered when I had finished..

Once I'd routed round unil the flange fell off I knocked through the skin fitting leaving a perfect hole to put the new one into.
 
CaptainBob said:
Biting the bullet and replacing a bunch of skin fittings. Easiest way by far will be to cut them off inside, flush with hull - they're all glassed in on the inside.

Could I use an angle grinder for that? I have a cheap one I use for sanding - I could get a metal cutting disc for it maybe?

Other suggestion(s)?

TY!
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115m/m angle grinder & cut the flange.
a cruciform across the face, or more cuts as req. then a 10m/m ish cold chisel between the grp & flange with gentle tapping to break the flange away.
remove from the inside.

or if you can get good access inside cut through the fitting threaded stem & then through the back nut.

you might find the fitting glassed over on the inside :eek::eek::mad:
 
I've just removed several by drilling with a holesaw from the outside, the holesaw's outer diameter being the same as that of the skin fitting tube so that the flange is neatly removed with no damage to the hull. I sent my dad to get the saws when I found the nuts were stuck, and he came back with ones designed for ceramic tiles. I had misgivings about using these, but gave it a go and they actually worked very well on the brass fittings.

The tile-cutting saws didn't have a central pilot drill, but I knocked a wooden plug into the hole and located the saw around that to keep it in place for the first part of the cut.

Pete
 
You really need to find out exactly how they are installed. Could be that they are standard through hulls with the lock nut glassed over. The normal ways of removing skin fittings is to either remove the nuts and knock the fittings out or grind off the outer flange and knock them in. However, glassed over means you can't do either easily so you may have to grind the glass off the inside and the flange of the outside.

Having said all that, not sure why you would want to remove them at all. They are almost certainly bronze or DZR so should last indefinitely. So just remove the valves and check/replace them.
 
Tranona said:
Having said all that, not sure why you would want to remove them at all. They are almost certainly bronze or DZR so should last indefinitely.
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Do you know more about his boat than I do, then? Cos plenty of boats have brass skin fittings that need replacing, my own one (until a couple of weeks ago) included.

Pete
 
Yep. He has a Nauticat - just about the most expensive and robustly built boat you can buy.

Pretty confident the through hulls will be bronze, hence my suggestion they won't need replacing.
 
Thank you for the replies! Hole saw on the outside is a stroke of genius!

Most of them on the inside are a gate valve screwed onto the skin fitting, with figreglass from the hull, up and over the bottom half of the gate valve. I've had to hacksaw all round under the gate valve to free them for unscrewing.

Reasoning behind replacement of skin fittings was twofold...

1. After a total failure of one reducer on one of them, when someone leaned on it, I asked Nauticat OY their advice on whether I should replace just the broken bit, or also the valve and skin fitting. They said that as it's such an old boat (34 years now) with unknown history (for some of it) that for safety I should replace the lot.

2. Just had a reputable engineering firm aboard and they said they had to advise best practice and also that they would without hesitation, replace the lot. I guess they would say that, but they're good chaps - I've used them before.

Tranona - do you think even though the internal fittings have in some cases crumbled apart as I've unscrewed them - that the skin fittings are almost definitely OK to leave in place?
 
Gate valves are notoriously poor performers in marine applications. It could very well be that the skin fitting is bronze and someone has fitted brass fat valves into them. Replacing both skin fitting and valve would be the Rolls Royce solution but if you examine the skin fitting carefull and there's no sign of crumbling, dezinctifaction etc then you could save yourself a pile of work and money by just replacing the valves with Bronze or DZR ball valves.

PS I had a boat that was over 50 years old once and the bronze skin fittings were as good as new.
 
CaptainBob said:
Tranona - do you think even though the internal fittings have in some cases crumbled apart as I've unscrewed them - that the skin fittings are almost definitely OK to leave in place?
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Appreciate your reasons for wanting to replace them. The actual through hulls are almost always bronze - even today when brass fittings have become more common. It is usually tail fittings and valves that give problems.

Unfortunately there is no infallible way of checking them, although when you get the valves off you should be able to tell if there is any sign of dezincification on the threads. If you have to grind away the GRP to get the valves off then not a lot of extra work to remove the fittings. In the whole scheme of things the through hulls themselves are cheap and bronze is readily available.

Grinding the outside flange off is by far the easiest way of removing them, and with care does no other damage. The inside may be more of a problem, removing enough GRP so the fitting can be knocked in from the outside. Important not to damage the hole and you may find you have to make good the surface inside to get a good seat for the new locking nut. I use Polysulphide for bedding as it does not set like polyurethane but does make a good seal and makes subsequent removal easy.

Hope this helps.
 
Tranona said:
The actual through hulls are almost always bronze - even today when brass fittings have become more common.
Click to expand...

I would expect bronze on a 30-year-old Nauticat, but the above statement is not true in general. Maxis were built with brass skin fittings - our new 1998 model was showing visible (though not yet structural) dezincification on both the threads and the external flanges.

All replaced now with bronze fittings and DZR valves.

Pete
 
vyv_cox said:
I think that if you try it the method described by prv, originally I believe suggested by Skipper Stu, is the easiest method. It makes a lot less mess and there is little risk of damaging the hull.
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May well be OK, but I have always (well the 3 or 4 I have removed) found grinding works fine. Will try the hole saw if ever I have to do it again.
 
If you want a more difficult method then do what I did :)
Passed a hacksaw blade through the fitting, and with one person working on the inside of the boat and one on the outside, hand sawed through the wall of the skin fitting in two places, a few mm apart. This allowed a section of the wall to be tapped out of place, and then the whole fitting could be crunched and squashed so that it was small enough to drop out of the hull completely.
 
I removed the heads outlet skin fitting on my boat by using an angle grinder to gently remove the inside circumference of the hole, until the outer flange was detached and could just be lifted off and the rest of the fitting tapped through into the boat. No hull damage.
 
The easiest way to remove skin fitting is not to use an angle grinder, which is difficult to control and will easily damage the hull if you slip, but to use a cutting disc on an Dremel type tool. Cut round the inside of the external flange to remove it and the internal fitting will then simply come away. I was dreading doing the job but actually it was really easy; so easy in fact that I wound up helping a coupleof other folks do the same job on their boats.....
 
duncan99210 said:
The easiest way to remove skin fitting is not to use an angle grinder, which is difficult to control and will easily damage the hull if you slip, but to use a cutting disc on an Dremel type tool. Cut round the inside of the external flange to remove it and the internal fitting will then simply come away. I was dreading doing the job but actually it was really easy; so easy in fact that I wound up helping a coupleof other folks do the same job on their boats.....
Click to expand...
That's the same reason why I used a small router with an old router bit.

I think that the hole saw technique is the best one though.

Make sure its a proper hole saw and not one of the cheap sort...
 
Whan you replace skin fittings, what do you seal them with ?

Sorry for the minor thread drift, but does the panel have any opinions as to what is the best stuff to seal replacement skin fittings with when you fit them ?

Boo2
 
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