Sealent for skin fittings

[jonathankent]

What should I use to seal/bond skin fittings with? I have read about Sikaflex, and normal silicone sealents, but are unsure of which one to use? I have also read that normal glass fibre, same suff as for car repairs, works well for bonding on the inside of the hull. Is this also the best way of bonding?

Confirmation would be much appreciated.

Jonathan.

 

[David2452]

Hi Jonathan

Sikaflex is good stuff, are the fittings above or below the water line? If you want to bond to GRP then an epoxy based product gives far superior adhesion that the polyester based product you mention, make sure the surface is well keyed and give it a quick wipe with acetone.

Personaly I would not use a "hard" permenant bond for this job, one of the Sikaflex products is more appropriate.

If the Skin fitting is below the waterline I would bond a square of SSS ply using epoxy with a filler material as a backing plate before cutting the hole, I woul also recommend cutting the hole slightly oversise and sealing the raw edges with epoxy before itroducing the fitting.

David

 

[TigaWave]

Arbothrane 1240 is as good as the Sika and 3M products, it also seems to last much longer in the tube. Its not so widely available in chandleries though, but half the price of sika.

1240 is a sealant adhesive so it is designed to have structural strength and will bond to metals and plastics. I guess you'll have to contact them to find a local supplier
http://www.arbo.co.uk/index2.htm

 

[SlowlyButSurely]

I will second using the Arbo product. I was recommended to use it by a boatbuilder several years ago. It works well and lasts much much longer in the tube. I bought my last tube at a builders merchant.

 

[beneteau_305_553]

Sikafex, Arbothane or Purflex are all Poyurethane sealants and are suitable for sealing skin fittings.

Silicone and other sealants are not as good as they do not bond to the surface so well.

Car body filler is too rigid and is likely to crack.

 

[VicS]

Sikaflex® is often mentioed on the forums. Sika® in fact do a vast range of products for industry and a small marine product range.

According to their leaflet the marine range includes products for bonding and caulking teak decks, adhesives for plastic glazing and for glass as well as sealants for fittings and hardware. Sikaflex® 291 is the general purpose compound suitable for fittings subject to minimal stress while Sikaflex® 292 is the high performance product for fittings subject to high mechanical stresses.

The instructions for the use of Sikaflex® 291/292 include, according to the materials, abrading, cleaning with Sika® Cleaner-205 and priming, wooden decks with Sika® Primer-290 DC and metal fittings with Sika® Primer-210T.

There is also Sika® Remover-208 for the removal of uncured Sikaflex®

Interestingly nowhere in the leaflet so they mention use of these products underwater but they do on the website.

Further information on www.sika.com/cmi-marine-index.htm

Thought you all might like to know!

 

[VicS]

Re: Car body filler

I missed this part of the question.

I have found that car body filler is very useful for attaching wooded pads to the inside of fibre glass mouldings. It takes out the unevenness and sticks the wood in position fairly securely. For best results clean and abrade the fibre glass and scratch the surface of the wood. I have used both the hard type and the elastic type but I can't say that I have noticed one to be any better than the other. When I have wanted something a bit more secure I have used the gap bridging type which contains some chopped glass fibres. For something really secure I also glass over the wood.

It sets quickly enough in warm weather for it to be held in place while does so and in winter time I have found that by warming the substrate first with a hot air gun it also cures quickly enough to do that.

 

[castaway]

I tend to use Sikaflex due to its availability, but would happily decamp to another supplier if the produce was as good and cheaper.

One point about using these sealants is to never 100% tighten them down until the sealand has gone off, if you do it tends to squeeze it out of the joints.

With regard to car filler paste, just be aware that it does absorb water, so although it can have its uses, be careful where it gets used!

Regds Nick