Sealing a through-hull with CT1

Murv

Murv

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Finally removed the old through-hull fitting after I managed to move it very slightly refitting a ball valve and therefore having nagging doubts about the integrity of the seal. It's all cleaned up and ready to be refitted tomorrow.
I was advised by the good folk on here to use Silkaflex 291, to hand tighten it on to spacers and then tighten fully in a week or so.
I was convinced by the chandlery to buy CT1 instead, and told to apply it, then tighten firmly straight away.

Should I do that, or do it as per the Silkaflex method of tightening onto spacers first?
 
I think the logic is that you leave a thin "gasket" of sealant onto which you subsequently tighten the fitting whatever sealant you use.

CT1 is brilliant stuff.. according to the video on their website
 
All the thru bolts,anodes etc including P brackets bolts on my boat are sealed with CT1.
Its cheaper than the other stuff and in my experience a lot easier to remove from unwanted places. :) ie. Me.
 
CT 1 is excellent stuff and better for underwater applications than Sika.

I use it now for everything when I used to use Sika. It sticks far better to plastic type surfaces very well and can do it even when wet.

Great for repairing rib tubes.
 
Never used CT1, but whatever the goop it doesn't seem very sensible to apply it and then promptly squeeze it all out again, wipe it up with kitchen roll, and take it home. If you want to fill your toolbag with gobs of adhesive, do it directly instead of via the boat :)

Pete
 
We are about to do something similar, on Tuesday. We are seating a thru hull but will be using Fix-tech 190, this is available in Oz and I think comes from Holland. We are using it in preference to Sika because its quick setting (they make another range that sets slowly like Sika does). We want the speed of setting because we are doing this between tides. We will be liberal with the sealant and tighten up until we have sealant extruded as a continuous bead all round the fitting. We will then leave to set for a couple of days and then tighten a little bit further, so as to compress the sealant slightly. Murv, if you have sealant left, stick it in the deep freeze it will then last, almost for ever.
 
Many thanks all, it seems logical to do it the same way (tighten down when cured) but it was the shocked look on the chandler staffs faces when I asked that put me off!

I will do it that way then, although by the looks of things, I'm going to need to choose my spacers carefully otherwise they're not going to come out afterwards!
I'm going to try matches for that, theory being that if they don't pull out, they should at least crush down.

My only worry is breaking the seal when tightening down post cure but I'll just have to be careful and see how it goes.
Incidentally, a large spanner fits neatly into the fitting and buts up against the lugs. The ring spanner can then be clamped firmly in a pair of large adjustables so at least it can be held firmly in place from the other side.
I'll also (as suggested on my other thread) fit the valve and hosing today so that the final tighten will be just that, tightening down and I won't need to stress the fitting any more after that.

The CT1 certainly looks impressive on their promo video (well it would, wouldn't it) so looks to be useful stuff to have around.

Thanks for the freezer storage tip Neeves, it's annoying buying large cans of gunk for a couple of small jobs only to find then set solid when you next need them no matter how well they're sealed.
 
Murv,

Putting in the freezer works for Sika, and Fix Tech, not sure about your CT1, its worth a try!

I'm not sure about your fitting but ours has what looks to be a common plumbers fitting to tighten down. (I'm doing this from memory) but its about 2.5 inch OD and threaded, so you simply hand tighten. it has 6 lugs protruding, that you can get a less than secure grip to tighten with a monster shifter. We have made from 2.5 inch rainwater down pipe a tightener. We simply cut 6 notches, to match the lugs, or webs, at 60 degrees each and then drilled right through the pipe so as to put in a bar. The pipe slots over the fitting and we simply lever round. Not my idea, a friend's. I thought the pipe would not be man enough - but it works fine. I'd send a picture but I'm at home and the bits are on the boat - you need to use your imagination!

Good luck!
 
Thanks for that, I can imagine what you mean.
My fitting just has two internal lugs on opposing sides but an inserted spanner does give a fairly secure hold against it.

Thinking about it, the final tighten will just be a case of nipping it down I assume, rather than the eyeball popping effort I'd usually put in as the sealant should be holding it fast and the final tighten is just to give a little compression against the sealant.

Will certainly try the freezer trick, it's worth a go and if it doesn't work I haven't lost anything.
Apparently the CT1 does last quite well anyway if it's sealed well, up to 4 months according to the chandlery so if that can be extended by freezing it then even better!
 
Murv,

We seem to be getting at least 12 months from frozen Sika. I have persuaded my wife that keeping Sika and a variety of different sealants in the deep freeze is economical - this has gone down very well.

All you should need to do is give a quarter turn, but you might not, should not, need to do anything. I'd certainly not get too aggressive. We needed the pipe trick as the fitting is up in the bow (of a cat) and there is not enough room to swing a spanner (or a cat come to that!) and the vertical notched pipe works a treat.

Jonathan
 
Noted, thank you.

I shall remember to use the economy line when justifying the sealant in the freezer!
 
Pleace never tighten a through hull after the sealing has cured.
If it is not sealed when you tighten it the first time when mounted
this will no make you procedure more secure for water thightness.
The retighten can only break the seal, so do not do it pleace.
Ask yachtbuilders if they use these procedure. They don't.

Good luck, do what you want.
HermanD
 
Herman has a good point but suggesting that what boatbuilders do is correct I might question. Today's boatbuilders should know by now about Osmosis, but that does not stop some modern boats being, very, prone. Its interesting how many modern yachts advertised for sale proudly decalre they have had recent osmosis treatment - one has to ask, why? Equally one might have thought they would have worked out how to attach keels - but again they have something to learn. Modern boat builders are into economy and the idea of tightening a 'sealed' fitting would make the economists cringe.

The particular brand of Fix Tech we are using has an elasticity of 300%, though I find this difficult to believe (but even 100% is good), it is also very strong. Our tightening flange is not part of the seal and will have no sealant in contact (we have a washer in between) so when we tighten the quarter turn after the sealant has set all we will do is compress it slightly, no-where near the 300% in the spec. Provided we have good adhesion the sealant should not part from the fitting, hull etc. If we do not have good adhesion I'd like to know now, not when I'm 100nm offshore. If the tightening flange is part of the seal, so you have tightened the flange onto the sealant and then onto the hull, etc, and if CT1 is not elastic I'd agree with HermanD, do not break the seal. An example would be tightening an epoxy fitting, all you will do is crack the epoxy. I do not know the characteristics of CT1 but one reason I like Fix-Tech is, that unlike Sika it is made to a quoted specification - which is defined on the packaging. Consequently I know its elastic and strong so provided I abrade slightly, de-grease etc I should get a strong seal. It might be belt and braces, but its a yacht!
 
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Just one potential problem springs to mind when you talk about 'nipping it up' after the gloop has set. Most of these sealants stick very well to the different surfaces they are sealing so if the fitting is tightened up by twisting, as in a through hull brass fitting, then that adhesion/seal will be broken. Different if there are large washers involved.

Just a thought.

Oops! HermanD beat me to it!
 
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I used CT1 on my cockpit drain outlets about 3 years ago, they are submerged so wanted a good seal,and couldnt get them to dry out to use sika, i put a thin bead and nipped them up hand tight with an adjustable, didnt wait for it to dry and its been leak free since.
wish i would have known about the freezer trick.
 
I've made the effort and checked and CT1 seems to have properties similar to Fix Tech 190, except CT1 skins more quickly (so you need to work fast) and has an even higher elasticity at 350%! These two products are going to give Sika a real run for their money. Fix Tech produce a slower cure product which we have also used without problem.

Chrishelen, you mention using CT1 in what seems to be a damp, wet, environment. There is no mention that I saw in my quick scan of the CT1 data (they might be covering their backs) - but can you reconfirm - you have had success under water without recourse to cleaning with solvent etc? I'm not suggesting your practice is to become standard, though 3 years looks commendable - but if it works its good to know for emergency work.

Just out of interest how much is CT1 from a chandler in the UK, normal tubes. Fix tech here is around Stg11.7 (which includes our 10% GST, VAT).

We have postponed our work of Tuesday for 10 days to the next appropriate tides, weather is currently a bit iffy and we did not fancy beaching in the forecast 50 knot wind.
 
I paid around 11 GBP from the chandlers, so it's probably available a little cheaper on-line (includes tax) so gives you an idea.

The video does claim that it will cure completely underwater, I am going to keep an unopened tube on board as part of our emergency hull repair kit. Could be useful for sticking a cushion or something over a hole!

I guess with the conflicting advice about whether to tighten or not after sealing, it's all down to whether or not there's any difference between 0.5mm of sealant or 1.5mm of sealant keeping the water out.
I suspect that with modern products, it doesn't. But, happy to be corrected.


EDIT: Just read your post properly Neeves,and the CT1 is more elastic! so, maybe that post cure compression would be even more beneficial with the CT1?
 
Hi Murv,

Thanks for the info on prices. I suspect as you are in a more competitive market (and not flush with people earning squillions from shipping iron ore and coal to China) prices might be a bit keener with you.

You'll have noted we have postponed our work, which means I need keep mopping up! We are re-seating a depth sounder and I have made a 'spacer' flat on top and curved to fit the hull beneath (being a cat its quite a tight curve up in the bow). The curve will have sealant under and up through, or round, the fitting and a washer on top (to stop the sealant coming out and to make sure the sealant is compressed, or fills the voids). The screw down flange sits on top of everything and should not touch the sealant. We are to do this between tides - hence use of quickset sealant. Once its set off I'll still be giving the screw down top flange a quarter turn to further compress.

You are to do exactly what I was thinking, a tube on the boat for potential emergencies. We carry a half metre square fibre glass panel 2 x750gm double bias (sits under a berth). I'll keep our Fix Tech beside it for when we go off to places without boatyards and chandlers.

If I can find the thread in 10 days time I'll let you know how we get on!

Good luck, fair winds!

Jonathan
 
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