Sikaflex

[mikenda - delete]

Advice please on which Sikaflex Sealant to use on underwater fittings ( I believe it is the polyurethane variety) but there are several versions. How long does it take to cure? How does one remove excess material from the hull and the thread of the new hull fitting?

 

[MedMan]

It depends upon whether you believe what it says on the Sika International web site (www.sika.com) or what it says on their UK web site (www.sika.co.uk) According to the latter you should use Sikaflex 291. However, according to the former you should use Sikaflex 292. If they can't agree between their own web sites, what chance do we Yachties have?

I prefer to put my faith in the International site - it is well written and well presented. The UK site is rubbish - everything a site should not be - flashy, hard to get around and difficult to read. I am assuming that as the presentation is rubbish the advice probably is as well!

If you go to:

http://www.sika.com/cmi-marine/cmi-marine-app/cmi-marine-app-4.htm

it says:

Bedding and Sealing Fittings Subject to High Mechanical Stresses
Deck fittings such as chain plates, winches and guide rollers have to absorb very high dynamic stresses. A high-performance product, such as Sikaflex-292, should be used in conjunction with additional mechanical fixation for this purpose.


Bedding and Sealing Fittings Subject to Minimal Mechanical Stresses
Deck fittings such as ventilators, cover strips, etc. need to be sealed against entry of water, but they are not subject to high tensile stresses. Such fittings can be effectively bedded and sealed with only Sikaflex-291.

Good luck.

David

 

[bryantee]

sikaflex 292. you can get it or eqivalent from marine and industrial sealants norwich .
tel 01692538263 E mail sales @marine-consumables.co.uk
good luck

 

[Guest]

Underwater use ONLY Sika 291 BLACK ... do not use 291DC BLACK as this is Deck Caulking Compound .. do not use 291 WHITE as it is a different compound ..
hope this helps .. Brian

Brian

 

[jfkal]

Better check with Sika. They would know. On a second note polycarbonate stress crazing does not get induced by Sika but by wrong installation without expansion gaps!

 

[vyv_cox]

Re: Sikaflex stress cracking

Whilst I agree that it is perfectly possible to induce cracking in Polycarbonate or Perspex by not allowing sufficient clearance for thermal growth, there is loads of evidence that certain solvents cause stress corrosion cracking in polycarbonate. Even Sika's own information states that some of their products should not be used with polycarbonate because of this problem.

 

[kingfisher]

Working sikaflex

Whatever the type of sika, there's just one thing you'll need: dish washing soap, and lots of it.

It's about the only thing Sika won't stick to. BTW, Sod's law states that Sika tends to stick to everything, except the object you're trying to fix.

So, i.e. to fit a trough-hull:
Drill hole
Apply massive quantity of Sika around hole
Apply soap (no solution, pure soap) to threads of through-hull. This prevents any Sika to stick to the threads.
Insert through hull, screw bolt on inside and tighten ALMOST completely. Massive amounts of sika should now have been squirted out on the side
Wet finger with soap, and go round fitting, removing any excess Sika.
Wait for it to cure a bit (6-12hrs), and then tighten nut completely.

Obi-Wan
http://sirocco31.tripod.com

 

[jfkal]

Re: Sikaflex stress cracking

Also agreed since they also specify which ones to use )

 

[brian_neale]

Is 291 white really different from 291 black? Is it 1st April yet?

 

[duke]

The Sikaflex Appplication guide I have advises the following :

SIKAFLEX-291
IS A ONE-COMPONENT, LOW VISCOUS, MEDIUM MODULUS, POLYURETHANE-BASED SEALING/ADHESIVE COMPOUND. THIS ALL-PURPOSE GRADE IS USED FOR GENERAL SEALING PURPOSES.

SIKAFLEX-292
IS A ONE-COMPONENT, THIXOTROPIC, HIGH MODULUS, STRUCTURE, POLYURETHANE-BASED ADHESIVE SYSTEM. THE PRODUCT IS USED FOR A WIDE RANGE OF BONDING APPLICATIONS, DECK-TO-HULL BEDDING OF CHAINPLATES, THROUGH- HULL FITTINGS AND TOE RAILS.

Hope this helps. As already suggested thge best thing would be to contact the Sika
company direct.
I have tel. numbers for various countries if you want.