Mast foam - a cautionary tale

[Avocet]

Just thought I'd tell everyone about my recent experience with expanding foam.

My mast is about 30' long. I had problems with wires slapping inside it as the boat rolled. About 5 years ago, I got so fed up, I drilled 4 small holes roughly evenly spaced up the mast and injected builder's expanding foam. It worked a treat.

Last winter, with the mast lying on trestles alongside the boat, some idiot must have driven past too close and snapped the VHF antenna housing. I got a new antenna, the old one was very old anyway and then the fun started. It was completely impossible to get the wires out.

Of course, I'd considered what might happen if I ever wanted to re-wire my mast but then thought that nothing was ever likely to go wrong with a length of wire (which, I suppose might still be true!) so I steamed on anyway.

To cut a long story slightly shorter, it took me two weeks to get the foam (most of it) and the wires out. The mast foot is a removable casting but the top is welded on. Working from the bottom I made a "drain rod" out of several 2m lengths of 20mm 16swg steel tube. and progressively hammered it up through the foam (and the wires) until I'd burst through all four foam blobs (they were each very big!). I then made an attachment to put the bottom end in a drill and stuck a long bolt at 90 degrees through the top so that I could spin the rod and it would eat a much larger hole through the foam. Obviously there was plenty of contact with the inside of the mast so I don't like to think too much about what it might have done to the anodising or the ends of the rivets holding the spreaders and luff track to the mast!

I then replaced all the wires and this time, made "spiders" out of large tie-wraps to stop the wires slapping. These seem to have worked just as well but I hope I'll be able to get the wires out again if I ever need to!

Everyone else who's thinking of using foam - beware!

 

[tonyleigh]

Some yrs ago same wire slap prob. Avoided exp. foam for fear of what you experienced. My solution was to thread pieces of old foam washing-up pads at approx 2ft intervals. Worked a treat.

 

[incognito]

Using foam is OK.

What you have to do is push a plastic tube up first, and plug the ends whilst foaming. Any new wires go up the tube. Old wires staty where they are, unless you have to replace with new (and I've covered them).

 

[graham]

Re: Mast foam - A Solution

A friend of mine had the sameproblem of needing to rewire a foam filled mast.His solution was to gouge out about six inches at the bottom and lean the mast ,foot uppermost, against a wall.

Now the clever bit he poured some acetone in and rotated the mast until all was a brown sludge.Hosed out the mess and leaned it other way up to drain out.

 

[bryantee]

Just rewired a mast.made the wires up into a loom.then taped pipe split lagging foam from B&Q .you need a messenger wire or rope for the Steaming and spreader light cables which come out of the loom 2/3 of the way up.this is the only tricky bit. Works with internal haliards a treat.Good luck

 

[vyv_cox]

Re: Mast foam - A Solution

Only if the foam is polystyrene. Polyurethane is not soluble in acetone, nor most other solvents.

 

[oldharry]

Re: Mast foam - A further cautionary tale

Reported a while back i think on these forums: an electrical fault set fire to the foam in someones mast. A challenge to extinguish even for a fully equipped Fire Brigade. Unthinkable at sea!

 

[ean_p]

Re: Mast foam - A Solution

vyv
is acetone a solvent to most types of paint found in a bilge or internal on a boat ??

ian p

 

[jfkal]

What is all the foaming about?! My mast is filled with narrow (and loose) slabs of styrofoam. Not an obstacle for new wires (I did two without problems) and does the trick quite well.

 

[vyv_cox]

Acetone (methyl methyl ketone)

is an aggressive solvent that will attack most single pack paint films and varnishes. Very good for recovering old paint brushes. It would not be suitable for stripping large areas of paint because it really needs to soak in to be effective. It is good for removing final traces of paint after stripping by other methods. Its rate of attack on GRP is very slow, so not normally a risk to rub topsides, etc. It has a low boiling point and evaporates very quickly.

MEK (Methyl Ethyl Ketone) is almost as powerful a solvent but has a higher boiling temperature, so evaporates more slowly.

 

[oldharry]

Re: Acetone (methyl methyl ketone)

But Avocet's use of plastic cable ties to make spiders which hold the cable in place is cheap, totally without mess, and is easy to install and replace.

And it has worked entirely satisfactorily on my last 3 boats.