Is Sikaflex Still The Sealant Of Choice?

[CaptainBob]

Been out of boating for a while but now have a half share in a Leisure 23.

There are some small deck leaks under stantions and the two gib sheet travellers.

I used to use Sikaflex for re-seating things like this but I hated the stuff as rarely did I use a whole (expensive) tube and then it would go-off in the tube.

I tried CT1 with some success but sometimes it went crystalline and failed to go off properly.

Is there something else people use now?

TY!

 

[vyv_cox]

Toolstation's Puraflex appears to be just the same stuff, made by the same manufacturer, at half the price. Still the best all-round sealant.

 

[northwind]

Butyl tape, doesn't set, means the fitting can be removed in the future without destroying the GRP.

https://www.pbase.com/mainecruising/rebedding_hardware

 

[Trundlebug]

I've personally found Sikaflex to be over-rated, and have always had great results both above and below the water line with silicone sealants.
Technology has progressed and they are really effective in most applications, although I guess Sika still has its place for some applications.
But universal use for everything boaty, definitely not!

Sika is also horrible to work with

 

[Poignard]

I'm interested in CaptainBob's bad experience with CT1.

I have used it for years and never had a problem with it; even with old stock.

Was it clear CT1, I wonder?

The reason I ask is that I was told by someone from CT1 Technical Support that clear CT1 should not be exposed to sunlight.

 

[peteK]

As mentioned butyl tape lasts years without going hard .

 

[Minchsailor]

I've had considerable with bog standard bitumastic gutter sealant.. Cheap as chips.

 

[Jaguar568]

Toolstation's Puraflex appears to be just the same stuff, made by the same manufacturer, at half the price. Still the best all-round sealant.

 

[Jaguar568]

Quite agree that Toolstation purflex pu40 is the same spec as sikaflex , used it on all my boats for the last 5 years.

 

[doug748]

I've had considerable with bog standard bitumastic gutter sealant.. Cheap as chips.

Never tried it but I note this:

"BENEFITS OF EVERBUILD ROOF & GUTTER SEALANT: Can be applied in wet conditions, even under heavy rain. Semi drying - remains permanently elastic beneath surface skin. "

Which sounds good. In the old days every chandlers had tubes of black stuff called something like Sealastic, it was very messy, unsophisticated black gunge but it worked.

Meanwhile, I am not that keen on Butyl rubber on the strip as it seems too hard to me. So I have just got a tube of this stuff to investigate:

https://www.marinesuperstore.com/sealants-resins/sealants-caulking/arbomast-br-sealant

Which may well just be a yotty, dear version of your gutter seal..............

https://www.sealantsonline.co.uk/Products/Butyl-mastic-sealants

Either way I never use anything that threatens to work like a glue.

 

[lw395]

Non-setting sealant work well in some joints.
In others, they allow things to move and the sealant creeps out.

When joints leak, it's often because the joint is badly designed and the sealant hasn't go much chance.
Silicone is pretty good, within its stress limits, and when it can stick to two hard, clean surfaces.
Polyurethane sticks better.
Blackshitforgutters sticks well but has no strength and won't resist the joint being pulled apart.
Butyl tape or any other gasket approach works in many joints, can be dodgy under high stress levels as it allows too much movement sometimes.

Some of the upmarket bathroom silicones are very good.
Big + for poly...... sealants is that they can mostly be painted over.
Polyurethane will tolerate a grubby rough surface if you degrease with white spirit, it will stick where silicone won't in my experience, you can prime porous stuff with any one pot paint if needs be.

The trick with things like stanchions IMHO is to countersink the tops of the bolt holes in the deck, so you have a 2mm bead of sealant around the bolt.
Silicone will stretch up to 100% depending on the grade and what it's stuck to. So a 2mm bead should cope with a little movement. A really thin bead soon runs out of movement and breaks away.
Non-setting sealant should work here around the bolts, but where there's a layer of it under a flat fitting it make creep out.

Sometimes the real problem is that the grp around the bolts is damaged, e.g. by impact to the stanchions, so now the deck flexes more and the sealant gets strained more.
Don't blame the sealant for not working miracles...

 

[[3889]]

Another vote for PU40 from Toolstation.
An alternative is this with which I have successfully sealed winches and windows with zero mess.

 

[webcraft]

.
I'm a convert to CT1, never had an issue with it - lasts a lot longer in the tube than Sika, and is considerably cheaper.

- W

 

[coopec]

Been out of boating for a while but now have a half share in a Leisure 23.

There are some small deck leaks under stantions and the two gib sheet travellers.

I used to use Sikaflex for re-seating things like this but I hated the stuff as rarely did I use a whole (expensive) tube and then it would go-off in the tube.

I tried CT1 with some success but sometimes it went crystalline and failed to go off properly.

Is there something else people use now?

TY!

I have solved the problem of Sikaflex "going off".

I use several layers of kitchen film (the sort you use to seal last night's left overs) over the nozzle held in place with a rubber band. Then several layers between the cartridge and the nozzle. Finally (much to my wife's annoyance) I store it in the fridge.

 

[Gunfleet]

I have solved the problem of Sikaflex "going off".

I use several layers of kitchen film (the sort you use to seal last night's left overs) over the nozzle held in place with a rubber band. Then several layers between the cartridge and the nozzle. Finally (much to my wife's annoyance) I store it in the fridge.

We should form a support group. I keep the glue for waterproof tapes in the deep freeze. My wife just rolls her eyes.

 

[coopec]

We should form a support group. I keep the glue for waterproof tapes in the deep freeze. My wife just rolls her eyes.

Let's commiserate!!

 

[Ceirwan]

I have solved the problem of Sikaflex "going off".

I use several layers of kitchen film (the sort you use to seal last night's left overs) over the nozzle held in place with a rubber band. Then several layers between the cartridge and the nozzle. Finally (much to my wife's annoyance) I store it in the fridge.

I worked for a while in the tropics and they always kept the Sikaflex in the fridge. Even the new unopened stuff.

On the topic I use Puraflex below the waterline & areas where I don't like to use Butyl.

 

[CaptainBob]

Great suggestions and thoughts, really helpful, thank you.

In answer to the question above about CT1. Yes, it was the clear stuff! Perhaps that's been my issue. TY!

 

[ghostlymoron]

It's horses for courses - for applications where adhesion is not required, I use butyl tape from a caravan centre, where I need to stick an item, PU40 works well and a lot cheaper than Sikaflex. Before the advent of high performance sealants, rubber gaskets were used - clean and easy to dismantle. It's generally not necessary to stick deck fittings to your boat, they are secured mechanically by bolts.

 

[Boathook]

Never tried it but I note this:

"BENEFITS OF EVERBUILD ROOF & GUTTER SEALANT: Can be applied in wet conditions, even under heavy rain. Semi drying - remains permanently elastic beneath surface skin. "

Which sounds good. In the old days every chandlers had tubes of black stuff called something like Sealastic, it was very messy, unsophisticated black gunge but it worked.

Meanwhile, I am not that keen on Butyl rubber on the strip as it seems too hard to me. So I have just got a tube of this stuff to investigate:

https://www.marinesuperstore.com/sealants-resins/sealants-caulking/arbomast-br-sealant

Which may well just be a yotty, dear version of your gutter seal..............

https://www.sealantsonline.co.uk/Products/Butyl-mastic-sealants

Either way I never use anything that threatens to work like a glue.

I prefer and use arbomast br sealant. It does seem to allow for some movement. As mentioned elsewhere in this thread countersinking the hole for the fitting does allow create a better seal.