Caulking with Sikoflex

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calloo

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I have to replace some traditional cotton and red lead stopper caulking below the water line. I am tempted to use Sikoflexas a substitute for the cotton and stopper. Can any body advise me on the efficacy of this practice please? Is there a particular Sikoflex product which will make a permanant watertight joint particularly below the water line?

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Hi Calloo,

Sikaflex is a paying compound NOT a caulking compound, whatever the manufacturers choose to tell you. In the cotton and read lead putty scenario, the Sika is therefore somewhat analogous to the putty part of the picture. However even then I'd be reluctant. Caulk it with cotton at the very least, as for paying it maybe Sika is OK but what's wrong with putty?

Mike

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I agree with Mike. Part of the action of caulking cotton is to keep the water out when it swells up. The other, and probably more important part of its purpose is to turn a flexible "basket" into a more rigid body. Without this, [and Sikaflex will not give this effect] your boat will flex all over the place, and rigging will tighten and loosen, placing unreasonable sudden stresses on itself and the hull. Carvel construction should be considered as a whole "system" if you like, where each part has evolved to complement the rest of the structure. To remove the caulking cotton is like removing the mortar from a brick building. The bricks will still stand on each other, but the whole thing will end up down around your ears at the slightest tremor or breeze.
Peter.

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I posted to someone else asking about sikaflex! Ill just say if you have a carvel hull you must use cotton and putty then it will take up , I once tried sika to seal the soft wood around my head fitting as its was spring and i could only come out for three days. With in days the humidity had rejected the sikaflex, so i mixed my very inexpensive old fashend putty found everywhere with a drop of linseedoil dived down cleaned up the area and applied the putty (underwater) It stayed in place the whole season and that winter i could remove the fitting and cut out the soft wood fitting a graving piece.
Same goes for the waterline seams if i have damage or the seam opens i fill with putty,
If i find worm (not on my boat!!) and the boat cant come out i dived in and fitted a copper plate coated with putty then nailed it in place that boat sailed two years before changing the planks!!!

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i could only come out for three days

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The product data sheet for Sika 291 states that it should not be immersed for 7 days.

John
 
I would not use Sikaflex to replace cotton. This has, in the past, caused damage to some planking, when swelling has occurred, creating planks that pull screws with some age, or split the frames that maybe weak from the age of the boat. This will make it much worse, sometimes, in any future repairs, with any attempt of reefing out any seams. Cotton, if done properly actually strenghtens the integrity of hull.
 
Was not contesting that at all Oyster.

Was just pointing out what the cure time before immersion requirement is for Sika 291, a matter which is not known by many. It is, of course, used for many other underwater duties.

John
 
Repectively, using any rubber based caulking, no matter what the curing time is, and using it in seams of wooden planks, period, is a bad thing no matter what the cure time of the product. Sikaflex is a wonderful product for a lot of jobs, but not for replacing the traditional seam compound, and can be hazardous to you and your boat. Thats the point that I was attempting to make here. Yes, in many cases, people have used it. But the odds are not that great.

This is the data sheet,.


Sikaflex 291 Tech Data

Density: 10.3 lbs/gal
Tack Free Time:* 60 minutes
Rate of Cure: 1/4-in x 1/4-in bead 9 days @ 40F/30% R.H.
1/4-in x 1/4-in bead 4 days @ 73F/50% R.H.
1/4-in x 1/4-in bead 3 days @ 73F/70% R.H.
1/4-in x 1/4-in bead 1 day @ 100F/75% R.H.

Storage: Store in a cool dry place
Shore A hardness (ASTM D2240): 45-50
Elongation at break (ASTM D412): 600%
Tensile Strength (ASTM D412): 225 PSI
Lap Shear Strength (ASTM D1002): 165 PSI
Peel Strength : 35 lbs/in on fiberglass
25 lbs/in on gelcoat
Application Temperature:** 40 F to 110 F
Service Range: -40 F to 190 F
Colors: Black, White
 
Err - not sure what you are carrying on about there, but to repeat myself I am not suggesting and have not suggested using Sikaflex for the use asked by the original poster (nor has anyone else as best that I can see).

Despite your statement of what is in the data sheet, the complete Sika product datasheet states 7 days before immersion (it is, I assume you are aware, used for many other underwater aplications for which it is well suited).

This is a link to a copy - http://www.sikaindustry.com/tds-ipd-sikaflex291-us.pdf. The immersion requirement is stated bottom left hand side of page 2.

John
 
[ QUOTE ]
have to replace some traditional cotton and red lead stopper caulking below the water line. I am tempted to use Sikoflexas a substitute for the cotton and stopper. Can any body advise me on the efficacy of this practice please? Is there a particular Sikoflex product which will make a permanant watertight joint particularly below the water line?

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My reply was in response to the above potential use of the product to replace traditional cotton, as noted in my replies. The concern of the curing time was also stated in the respective respondents. My reply was a statement of fact of adverse conditions that can be created from this modification or upgrade, as some may feel by using a more modern material as a substitute. This surely has no bearing upon any recommended curing times and other misc applications, under water, and shown in the documents provided by the manufacturer.

I hope this clears up your confusion to my original reply, and followup.
 
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