Hippo mooring buoy

[Dazedkipper]

The foam filling in my buoy is disintegrating around the top edge where the boat bumps against it. Has anyone tried filling one with builders PU foam? I'm thinking of drilling maybe four holes and filling from each in turn until excess come out from the other holes.

 

[sailorman]

So called "builders foam" is not closed cell so will absorb water

 

[Dazedkipper]

Good call.

 

[Quandary]

So called "builders foam" is not closed cell so will absorb water

Same with polystyrene but it does not stop them filling pontoon floats with it.
Our club was gifted polystyrene foam blocks for racing marks, they floated for quite a few years until the gulls ate them.
How many years extra life are you hoping for?

 

[Dazedkipper]

Another year or two would be a bonus, it's got to be 25+ years old so doesn't owe me anything but having just done standing rigging funds are a bit tight to replace it.

 

[Quandary]

Another year or two would be a bonus, it's got to be 25+ years old so doesn't owe me anything but having just done standing rigging funds are a bit tight to replace it.

I would try the foam. it is cheap, easy to work with and its main purpose is just to hold the thing together for a while longer, there will not be enough of it to affect buoyancy? You can get polyurethane expanding foam but it will not be anything like as handy, the builders foam will go brown in UV so wipe off any excess.

 

[philwebb]

Hi Sailorman, The builders foam is not water absorbent in my experience. It can actually be used to block holes in boats as a temporary repair. It needs water to cure, but after setting it is stable. It is degraded by UV though.

 

[Hadenough]

Hi Sailorman, The builders foam is not water absorbent in my experience. It can actually be used to block holes in boats as a temporary repair. It needs water to cure, but after setting it is stable. It is degraded by UV though.

It is open cell so if the outer skin gets damaged it will absorb water like a sponge. OK for protected environments, fridge, thermal, insulation in a void but forget it for anything that will get a bashing.

 

[sarabande]

Is it worth 'grafting' a really tough polyethylene foam into th ebuoy ?

https://www.efoam.co.uk/closed-cell-polyethylene-foam.php

 

[sailorman]

I would try the foam. it is cheap, easy to work with and its main purpose is just to hold the thing together for a while longer, there will not be enough of it to affect buoyancy? You can get polyurethane expanding foam but it will not be anything like as handy, the builders foam will go brown in UV so wipe off any excess.

Put the cost of the tin of foam into the purchase price of a new mooring By

 

[Quandary]

Most of my experience of using 'builders' foam is in filling gaps when fitting domestic windows, its purpose there is closing voids and resisting driven rain, it works fine for that and I have never seen any that succumbed to moisture.
Perhaps if the OP fills the voids at the top of his hippo it will do the same thing there for a year, perhaps two and allow him to defer an expensive purchase?
Important that it has an escape route when injecting or it could split the casing.

 

[Dipper]

My experience is the same. A few years ago I filled my hollow rudder with builders foam because it was always full of sea water and had a lot of momentum in a heavy sea. When I eventually rebuilt the rudder I found no evidence that the foam had absorbed any water despite being immersed in sea water for several years. Surely if it was used in house building and it absorbed lots of water, it wouldn't be any use?

 

[Dazedkipper]

So all done but maybe not my finest hour, 1st can of foam got blown over and fell onto a sharp edge which punctured it. It's amazing how much foam can escape from a 2mm long split and you can't stop it either so apologies to the hard at my club which is now somewhat foam splattered.
Four 10mm holes drilled through the skin of the buoy on the top edge and two cans hastily borrowed from a friend and it seems to have worked. I injected probably more than needed and then left it overnight to expand and cure, the excess venting through the holes. Time will tell but on first inspection the buoy is well filled and firm.