Comparison of retail marine sealants for bedding deck fittings

[demonboy]

I used a single layer that seems perfectly adequate.

:encouragement:

 

[doug748]

For the last sealing job, on a leaky stantion base, I used Screwfix Silicon.
£2.95 a tube.

Good man, I always use whatever is left over from the bathroom jobs.

I use it for most jobs but if there is a chance of an uneven, low clamping force coupled with a small flange area and possibility of wringing forces - for example with windows - I would look at the Butyl stuff. All reports I have seen are very positive.

I have never had a problem with Silicone used below water or on deck for that matter. It is primarily a wonder gasket making material but I have found its adhesion very good, whilst retaining the capacity to be removed as required. I bodged my Perspex hatch with it when I bought the boat, it is still there acting as a adhesive, 20 years later.

 

[ghostlymoron]

That's a pity because I find silicone sealant a bit messy to use. I've used PU40 under some other plastic skin fittings so am tempted to ignore NASA recommendation. Also I'll probable ignore the instruction to glass it in internally.

They do, because the one advantage of silicones over most other sealants is that they contain no solvents that might react with the plastic log fitting that NASA supply. I assume that they have had some adverse feedback about solvent based sealants but other makers who supply plastic fittings seem to have no problem with better sealants.

 

[vyv_cox]

That's a pity because I find silicone sealant a bit messy to use. I've used PU40 under some other plastic skin fittings so am tempted to ignore NASA recommendation. Also I'll probable ignore the instruction to glass it in internally.

I was tidying my documents folder this morning and found installation instructions for both Airmar and B&G through hull plastic fittings. In each case they recommend 'marine sealants'.

 

[captainboo]

Also I'll probable ignore the instruction to glass it in internally.

That recommendation is there to prevent the whole fitting becoming detached in the event of the outer flange being struck and cracking off from the threaded tube. Can also happen over time if you are a bit too enthusiastic in tightening the backing nut!

 

[vyv_cox]

. Can also happen over time if you are a bit too enthusiastic in tightening the backing nut!

I wonder if that is the source of the 'no solvent' sealant instruction. Stress corrosion cracking occurs with some solvent/plastic combinations but could well be confused with failure by over-tightening.

 

[biscuit]

+2 for Butyl tape : clean to apply and very effective.

 

[Spirit of Glenans]

Is Butyl Tape ok for use on seacock skin fittings?

 

[BruceDanforth]

I rebedded my windows, deck fittings and the woodwork around my main hatch this summer using bostik polysulphide from Jewsons and so far nothing has leaked, I'm in the process of removing the rudder skeg over the next day or so and will use sikaflex for that once I get the old stuff to release.

 

[vyv_cox]

Is Butyl Tape ok for use on seacock skin fittings?

I suspect that its resistance to seawater is perfectly adequate but for me it would not be a good choice for the application. An elastic mastic under the flange and between the threads and hull seems to me to give the ideal joint for skin fittings.

 

[ghostlymoron]

' That recommendation is there to prevent the whole fitting becoming detached in the event of the outer flange being struck and cracking off from the threaded tube. '
How likely is that!

 

[Birdseye]

That looks just the same as the stuff I used to bed one of my wheelhouse windows on Cecilia. It is what Mainbrace in Milford Haven use for all similar sealing jobs. It has worked fine in excluding water but seems to continue extruding almost indefinitely. I used a single layer that seems perfectly adequate.

Yes. Thats the stuff that was used to seal the double glazing into my hardwood windows in 1995 and believe itor not its still slowly extruding in wasrm weather.

 

[captainboo]

' That recommendation is there to prevent the whole fitting becoming detached in the event of the outer flange being struck and cracking off from the threaded tube. '
How likely is that!

Probably not very, but it is only a plastic fitting and relatively thin. I think it is more belt and braces and it is not going to do any harm.

 

[charles_reed]

Interesting thread - I think those who claim anything is "good" after less than 5 years in use are making themselves hostages to fortune.

As and example: I fitted an A-frame in Argeles in 2002, for flying a genniker - the down haul is on a dolphin striker 150mm above the waterline. This was sealed by bags of "marine silicon sealant". Two years ago I found water in the bottom of the fore-locker. At first I blamed another possible culprit, the bitter-end staple in the chain locker. The input only occurs after fast (sailing), it's about 10ml an hour. None when stationary or travelling @ less than 5 knots and in a calm sea. It's clear that the bow-wave has washed away the external sealant and when the boat is lifted next week I expect to find the Ubolt used to have been 304 stainless, to be suffering considerable wastage due to anaerobic corrosion and to have a considerable problem cleaning off the old silicone.
Apropos of butyl tape, I've found it ideal on the end of stainless stanchions, in alloy sockets - the first time I had to replace stanchions (when the original aluminium ones all fatigued at the intermediate hole) it took over a week of work, several lpg canisters and finally the discriminate use of an angle grinder. I was only saved by Boat-Barge @ Bursledon finding me 4 replacement 2nd handsockets.
When I had to replace the one stanchion bent in last Tuesday during the 40knot winds into the entrance of Thassos, it took me about 20" to remove the damaged item.

 

[charles_reed]

Without trying to knock BoatcomUS, it is revealing that 3M do not recommend the same sealants from their range - eg for external bonding of deck-fittings they recommend 755 which is a hybrid elastomer.
After struggling for 12 years trying to find and adequate sealant for my forehatch perspex, I used a hybrid sealant which has proved utterly reliable for the last 3 years (the leaks now come from other places suggesting the need to re-bed the frame). It wasn't made by 3M and took about 60 hours to fully cure in about 20-38C temperatures.

 

[PabloPicasso]

I don't know, but it is identical to the cheaper and more readily available tek7

 

[Trundlebug]

I'm about to fit a semi flexible solar panel (aluminium backed) onto my boat's sunroof (GRP).

I want to use a sealant / adhesive, which will keep the panel in place and stuck down in all weathers.
I also want it to be removable in about 10 years time without causing damage to the sunroof or being a total pig of a job when the panel eventually expires.

What do the forum experts recommend?
I'm completely confused by the information above - a case of too much and too little information I think.

 

[BERT T]

I'm about to fit a semi flexible solar panel (aluminium backed) onto my boat's sunroof (GRP).

I want to use a sealant / adhesive, which will keep the panel in place and stuck down in all weathers.
I also want it to be removable in about 10 years time without causing damage to the sunroof or being a total pig of a job when the panel eventually expires.

What do the forum experts recommend?
I'm completely confused by the information above - a case of too much and too little information I think.

Use CT1.

 

[Trundlebug]

Use CT1.

Thanks for that.

I've been using an Evo-Stik product at work recently that seems remarkably similar to CT1.

Evo-Stik Nail and Seal. £6.98 from B&Q, so cheaper than CT1 and easier to get hold of.