Skin Fitting - Which Sealant?

[PabloPicasso]

For deck fittings butyl tape is ideal
It remains flexible and never goes off, is even reusable if needs must. May not work so well in tropical heat though (Ive never been in a postion to find out for myself ).

Countersink the hole to be sealed so the sealant has somewhere to go. Probably useful to do for any sealant type though.

 

[Pye_End]

, for some reason you assume I don’t have experience simply because that wouldn’t fit your narrative.

Because of your language. You type of 'others' who have had leaks due to use of butyl, not of yourself (strange how this diverse forum doesn't seem to also come up with these tales - quite the opposite). Because of your comments over exaggerated oozing. Because of your conclusions that butyl is prone to leaking. Beacause, even now, you say you 'have experience', but you do not say 'I used it on xyz for xyz years and found it failed due to xyz, but my modern sealant lasted for decades'.

You speak of 'narrative' - but several posters here do not fall into your 'modern is better than old' mantra on this subject - and still no other posts supporting your view. Who is the one with the narrow narrative?

 

[lustyd]

You speak of 'narrative' - but several posters here do not fall into your 'modern is better than old' mantra on this subject - and still no other posts supporting your view. Who is the one with the narrow narrative?

Lots of people on this forum don’t sail their boats so are oblivious to progress. Look at threads on lithium as a great example of people saying stick to something traditional.

You’re the one having a go here, not me. I’m simply pointing out that silicone has a place on boats since a couple of people dogmatically stated it doesn’t (but couldn’t suggest something appropriate). I was also pointing that there are better solutions than mastic and butyl in 2026 (and there were in 2000!). Science has not stood still, if you’ve not tried the modern stuff give it a go it’s better in every way.

 

[fredrussell]

As I said earlier, I see no problem using silicone to seal a shower. I think what we’re all trying to say is that using it anywhere where you might want to paint or use other sealants is a bad idea, for the reasons clearly stated in post #15.

 

[fredrussell]

Lots of people on this forum don’t sail their boats…

I’m interested to know how you arrived at that somewhat dismissive viewpoint? Certainly not the impression I get.

 

[doug748]

Further to post 4.

There have been a number set piece moral panics about bedding skin fittings. During a previous one in 2008 I was fitting a new engine and put my money where my mouth was by bedding a new Blakes seacock with silicone. It was perfect up to selling the boat last year - may have sunk since but I would have heard.

It's best treated as a gasket making material, you make the joint with a light touch and nip it up after the cure.
Much of its bad rap is due to people hopefully blagging it on top of leaking deck fittings.

 

[Concerto]

My teardrop anode had slightly rusty fixing bolts, so I decided to replace them about 8 years ago whilst the boat had been out of the water for a couple of months. I used butyl rubber. Never been a drop of water come through. So I have had no problem using butyl rubber underwater.

 

[PabloPicasso]

Lots of people on this forum don’t sail their boats..

... as much as they'd like to!!

Mine is up on the hardstand in its cradle until lift-in in April. So not sailing at all at the moment

I hope to put that right over the summer though

 

[PabloPicasso]

So, butyl tape is good for deck fixings if its dry when applied.

I thought the op asked about thru hulls. May be submerged, so a range of adhesives and/or sealants mentioned:

Sicka 291/291i (what is the difference?)
Sicka 591
Saba Sealtack
SABA tack 750XL
CT1
OB1
PU40 (is that the same as Puraflex 40?)
TEK 7
Bathroom silicone.

lets have a vote based 9n previous experience only.

What did you use?

How well did it perform?

Related horror stories welcome, of course

 

[lustyd]

Sicka 291/291i (what is the difference?)

As I said in post 2, discontinued so doesn’t matter

I used Sika 291i for through hulls and loctite 5331 for seacocks as per TruDesign recommendations. All good so far, as is the dst810 sensor in Sika 291i.
I assume 591 will work the same, TruDesign recommend it as the replacement.

 

[PabloPicasso]

As I said in post 2, discontinued so doesn’t matter

With all the pointless bickering that seems a long time ago. Ill go back and have another read

 

[lustyd]

With all the pointless bickering that seems a long time ago. Ill go back and have another read

It wasn’t more in depth than that

 

[PabloPicasso]

This guy was keen

 

[STATUE]

I am replacing my log impeller with one of a larger through-hull diameter.

Which brand and type of sticky stuff would you recommend to bed the (Airmar plastic) skin fitting in with?

Thank you.

My trusted boatyard now uses CT1. Sealant and adhesive

Does not go off as fast as others in the tube.

I have used it in the last 12 months to replace a wooden strengthening plate onto a wooden hull and then a transducer hole through the thickened area.

Don't be put off by buying it from a building supplier !

 

[ghostlymoron2]

I'm with Vyv on the use of silicone sealant and not having umpteen different sealants on the boat but i did think twice when fitting a NASA log as NASA specifically recommend silicone. In the event, i used Sikaflex and as far as I know there have been no probs. (I no longer have the boat.)
How about using a rubber washer - non reactive, easy to dismantle if necessary, cheap and you don't end up with a nearly full tube of expensive sealant (which has probably gone off by the time you need it again).

 

[lustyd]

rubber washer

probably nitrile/neoprene etc. rather than actual rubber

 

[Zing]

I tried PU40 on thru hulls/deck fittings. Didn’t like it. Too soft/weak. Went for 3m 4000 instead. Much better, but expensive. Cost is irrelevant on important jobs like these.