Glueing stainless steel to GRP?

[Coaster]

I'd like to glue a thin stainless steel plate to the stem of our GRP boat hull, to protect the gelcoat. It's getting pitted by occasional contact with our bower anchor which usually lives at the stemhead.

Can this be done? If so, what glue should I use and how should the surfaces be prepared?

All knowledgeable comments will be much appreciated.

 

[JSYmartini]

Sikaflex 291 would probably do but you'd need to rough up the gelcoat to 80-100 grit, as you'd probably have to do with any type of glue.

Kind of defeats the object of trying to protect your gelcoat but...

 

[VicS]

Sikaflex 292 may be a better adhesive.

For best results you should use the appropriate primer(s)
You will find the Sikaflex Marine Handbook at www.bluemoment.com/downloads/sikaflexmarinehandbook.pdf

Often possible to find the less expensive non-marine equivalents of Sikaflex products. Sikaflex 252 in this instance I believe.

 

[daveyw]

I found a new product(new to me) Tec 7. Fantastic stuff. 'bout £9 a tube and I've only found it at B&Q.

http://www.contec7.co.uk/tec7.htm

 

[Coaster]

Thanks all. I've now looked at the Sika manual. It gives good instructions regarding preparation etc. I'm wary of using the Tec 7 product in a location which will be frquently doused with seawater, although it certainly looks to be a useful material.

 

[robertj]

Sikaflex 291 applied to well cleaned (thinners) non sanded Gelcoat.
This stuff will stick hope if you have to take it off your Gelcoat is bonded well to the glass fibre under.
Just removed teak in cockpit for renewal it took several areas of gel from the glassfibre under.
Bob

 

[William_H]

Glueing Stainless Steel

No one has mentioned that it would be a good idea to rough up the SS plate to improve glue grip. Clean the SS with meths before glueing. good luck olewill

 

[Avocet]

I agree. I think getting adhesion to the stainless will be more of a problem.

 

[savageseadog]

Some small countersunk screws or monel rivets along with the glue will hold it in place better but I would understand why you might not want to.

 

[fergie_mac66]

Sticky stuff

we have a stainless soled iron. Swmbo ironed some blouse that stuck to the sole.The blouse would act as a good adhesive !I still havent got it all off

 

[reeac]

Some small countersunk screws or monel rivets along with the glue will hold it in place better but I would understand why you might not want to.

I fixed a similar plate to our bows for the same purpose using just s/s self tappers. Worked OK but I found a s/s tang from the stem fitting just below the gelcoat.

 

[thalassa]

I found a new product(new to me) Tec 7. Fantastic stuff. 'bout £9 a tube and I've only found it at B&Q.

http://www.contec7.co.uk/tec7.htm

+1

I had success with two-component putty as well, but it is not applicable in every situation.

 

[CelebrityScandel]

I agree. I think getting adhesion to the stainless will be more of a problem.

There is no difficulty whatsoever getting sika 291 or 292 to stick to stainless steel (or to most anything else, including fingers, shirts, hair, the dog, etc). We have used ss sheet for years for protection where sheets rub over coaming edges, anchor protection, etc and never had anything come loose. Even small pieces of sheet will stick tight.

Just clean both surfaces, use sika's recommended primer if one is really keen and stick it down.

Another suggested using screws as well - they are never needed (even on small pieces of ss sheet), look bad and damage the substrate.

The only hard part is getting the ss sheet to be a nice tidy fit over the curves, tapering edges, etc for which even if just doing a strip over a coaming edge we make templates, out of cardboard for small pieces, and get the job press braked by an engineering shop.

 

[Coaster]

Thanks again for all your comments.

I now intend to use Sikaflex, without screws, and will consider having the plate pre-bent to fit. I had hoped to bend the plate in situ but CelebrityScandel's post has led me to reconsider.

 

[cliff]

I had hoped to bend the plate in situ but CelebrityScandel's post has led me to reconsider.

"bend in situ" indeed

Also, look at "plumbers gold" from toolstation - comes in clear or white and sticks almost anything to anything - did I mention it is much cheaper than Sikaflex?

 

[vyv_cox]

I am seeing more of these MS hybrid polymer sealants as time goes by. I bought a tube of caulking sealant last week to try to solve our never-ending window leaks. This was of the same type, called Merbenit DC25. I dropped a small squirt of it on the deck unnoticed when I cleaned up. It has stuck extremely well and will not pull off, needs the scraper. For the first time in years we have no window leaks, despite two torrential thunderstorms in the past few days.

 

[lw395]

You can buy self adhesive thin stainless sheet for chafe protection.
Apparently it works very well and bends to follow simple curves.

Presumably one of the limitations in a large area like an anchor guard, would be thermal expansion shearing the glue? It would probably be more resistant to this if the glue was a thicker layer rather than squeezed to nothing?

 

[Lakesailor]

I've had great success with Sabatack 750XL. Very similar to Sika 292 but half the price and much cleaner to work with.

Having said that I bonded some s/s plates to the gunwhale beneath the cleats to prevent abrasion from the mooring strops using Sikaflex 291. Still there 3 years later having being rubbed on 24/7.

 

[SAMYL]

I would suggest you try CT 1, much better than Sika products or Tec 7 and designed for a wet environment.
It will even stick underwater.

 

[Coaster]

If I may ask one further question; what thickness of stainless steel sheet should I use? The overall size of the required plate is about 250mm x 200mm.