Sikaflex removal

[plasticpaddy]

Hi
I’m repairing the stern gunwale and need to replace the sikaflex. What’s the best way to remove the old sikaflex?
I removed most by scraping but there is still a residue left. Can I just rub with sandpaper and lay new sikaflex over it? Or do I need to remove completely
Sean

[Peter T]

Possibly new over old sikaflex might work but if the residue is small then you could use a solvent.  The only solvent that seems to work in my experience is white spirit plus a cloth and lots of elbow grease.  Rest for 2 minutes then more white spirit and more elbow grease.  Then repeat as necessary!  Doesn't sound very appealing but it does work.

[Peter Taylor]

The solent for Sikaflex 298 bedding adhesive (sold as costly Sikaflex 205 primer) smelt very similar to cheap isopropyl alcohol. I don't know if that would work for other types of Sikaflex (which have cured) but it might be worth a try. A screen wipe or pre-injection swab would be a way of testing if you have either.
Peter

[plasticpaddy]

Thank you, I'll give them a try

[Charles Scott]

There isn't much that can't be removed with acetone.
  Charles Scott

[BobT]

The sealant, sikaflex is assume, needs replacing round my gunwales as it is just lifting out.  Which Sikaflex should I use and are there other (cheaper but as good) fillers I can consider?

Cheers,
Bob

[Andy Dingle]

Bob. I use some stuff called CT-1.

http://www.ct1ltd.com/our-products/ct1/

In my lowly opinion is far better and cheaper than Sikaflex. I swear by it. I even used it to bond/repair my fish pond liners under water and they've not leaked in years.

Readily available in all builders merchants at about £10 for a normal size tube. It's environmentally friendly, goes off underwater, comes off the shelf in a whole range of colours, from clear through to black, has shock absorbing qualities as it remains flexibly rubbery, will stick just about anything and holds and seals better than anything else I've used.
Millions of tradesmen use it everyday and it doesn't have the 'marine' price mark-up.

I may be wrong (probably am) but I seem to recall it mentioned Matt doesn't use 'sikaflex' either on our boats but it's some other industrial adhesive (and I suspect cheaper. In price, not quality I mean).

Hope this helps.

Andy

[BobT]

Andy,
Many thanks for the info I am off to buy a tube as your suggestion supports my other research.
Cheers,
Bob

[Nick Orchard]

In case it's of interest, when I had a minor leak due to a deck fitting screw not being fully sealed, Paul at Swallow sent me a partly used tube of what they use to build the boats. It's Bostik Simson MSR construction adhesive. It fixed the problem and I've used it on a couple of other sealing/sticking jobs and seems to be pretty good stuff. Whether it's any better than the ubiquitous Sikaflex, who knows? Seems to be available on lots of internet sites and about the same price as Sikaflex.

[Rock Doctor]

Interesting discussion re Sikaflex. I have a GRP BR20 and the Aussie weather seems to be getting at it after 5 years. Sikaflex seems to be shrinking and cracking (drying out?) on all seams especially around the ballast tank where I gain a little extra ballast when I sail with the gunnels under!

Comments re suitable cleanup solvent for hard Sika are welcome. This winter will see some considerable sealant removed and replaced.

[david]

Hi All, restarted this thread as I am about to embark on the removal of the sealant around my ballast tanks also. The sikaflex has dried and is ballast leaking.
I plan to use white spirits to help clean up the residue. Most I was able to takeout with a little elbow grease, knife and screwdriver!
Any suggestions to make the job easier are appreciated.  I was able to remove about two feet of the seal today. It's not an easy job.
Anyone use white spirits or another better alternative?
I am interested to hear how Rock Doctor got along as his boat and mine were made at the same time.

Regards

[TimLM]

Hi David,
I've used Sikaflex and several other silicon sealants and found Dow Cornings 791 to be just as good as any and less expensive from diy shops (screwfix my preference). Romoval of Sikaflex and it's equivalents is best done with a plastic scraper similar to the ones sold to clean pans and the small amount left with white spirit. I've tried acetone, meths, tricoetheline etc. but I have found white spirits to be the only effective one.
Good luck, Tim.

[david]

Thanks Tim. I can not find white spirits here in California, I was told it is not allowed by the state. Acetone is available.

[Sea Simon]

Thanks Tim. I can not find white spirits here in California, I was told it is not allowed by the state. Acetone is available.

I believe California can be particularly difficult wrt environmental issues?
However, hard to understand why the authorities might let you mess with Acetone, but not white spirits!
Acetone is a far more aggresive solvent, and generally much nastier to be around. Readily available hre in UK, but only from the more specialist suppliers. I used to be able to use my wifes nail polish remover, as was pure acetone in old days....but that seems to have gone "green" , with all sorts of additives rendering it useless for boat/car repairs!

As another name for what UK calls White Spirits, try looking for Mineral Spirit in the US? This used to be freely available.

https://www.shell.com/business-customers/chemicals/our-products/solvents-hydrocarbon/white-mineral-spirits-blends.html

Artists and "proper " decorators/painters also use Turpentine Spirits for similar applications, but is usually very expensive. I think Turps was the original organic product, and we still see "Turpentine substitute" on some White Spirits containers here in the UK. Can't vouch for its efficacy in removing sikaflex tho.....

[Michael Rogers]

I'm joining in this discussion having just used Sikaflex after yonks, actually not on my boat but on an ancient 4x4 which a member of the family reversed into a bollard, destroying a lamp cluster and distorting the cavity into which the replacement part had to fit, with a few gaps needing filling to prevent water ingress after I had wielded an 8lb hammer with some vehemence(on a robustly built vehicle, I have to say). I forgot to wear disposable gloves, and my task was to remove the dratted stuff from my hands. HUH!!

In the interests of 'science' I was systematic, and tried white spirit, acetone, meths, Swarfega, and something called 'plaster remover' bought from a chemist years ago (describing itself as 'a blend of hydrocarbons'). I haven't any trichloroethylene to try: I gather TimLM wasn't impressed with that either. The least useless (I have worded that carefully) was white spirit, so I sort of agree with Tim. (It occurs to me that I didn't try petrol or diesel: I wonder.....). The moral is, of course, to wear gloves. Meanwhile, the whorls and ridges of my right digit fingerprints are accurately picked out in indelible jet black until I naturally shed sufficient layers of epidermis for the effect to disappear.

(The repair of the car didn't turn out at all badly).

Michael