Improper Sika Primer Being Used in RV's?

Noah · #1 02-21-2009, 09:52 PM

What am I missing... Both Sika's website, and Jamestown Distributor's website, which sells the Sika line, require the use of a primer on aluminum & steel that, as far as I can tell, nobody uses.

I don't know about you, but I would think that following the manufacturer's instructions TO THE LETTER would be highly advisable on your canopy where you really only get one shot to get it right.

The way I am reading this, Sika 209N primer is required on the plexi side, and Sika Activator and Sika 206 G&P are required on the aluminum or steel side of the bond.

Yet Mickey Coggins' site and the Matronics site regarding canopy bonding- widely considered the authority and central knowledge base for Sika canopy bonding, does not mention Sika 206 G&P, unless I missed it somehow.
http://www.rv8.ch/article.php?story=20050617213651709
http://wiki.matronics.com/wiki/index...ng_Your_Canopy

Additionally, a search of Sika 206 G&P doesn't turn anything up on VAF either.

Check my math. According to:
http://www.sikaindustry.com/primer_chart_4-21-06.pdf
our application is an "application involving large components where there is joint movement. examples: "...WINDSHIELDS, side windows". The joint movement arises from the difference in thermal expansion with temperature between the aluminum and the plexi. Thus our application is a LEVEL II sealing / bonding application, and requries scothhbrite, followed by SIKA ACTIVATOR, followed by SIKA 206 G&P on untreated aluminum and steel.

Similarly, videos on Jamestown Distributors website call for the 206 G&P:
http://www.jamestowndistributors.com...ct.do?pid=3508

Yes, this will add to the cost of a Sika installation because these primers and cleaners aren't cheap. However, this is no place to cut corners. Why then, does it seem that nobody has used the Activator and 206 G&P primer on aluminum & steel as required by the manufacturer for our application?

DakotaHawk · #2 02-21-2009, 10:05 PM

Noah,

I used Sika on my canopy, and followed the process used by two other builders - one RV-8 and another RV-7. Both sites were very specific about the necessity of using the primer.

Sika's data sheet is specific about the primer - if you don't use it, don't expect the SikaFlex to devolop full adhesion to the material that you're bonding. This means that the primer has to be applied to both the canopy AND the frame! There is also a timeframe from when the primer is applied to when the SikaFlex has to be applied. Don't think that you can scuff the primer to enhance adhesion if the time has passed. You must apply a new layer of primer prior to using the SikaFlex.

So the short answer is "You must use the Sika Primer!"

Noah · #3 02-22-2009, 06:53 AM

Quote:

Originally Posted by DakotaHawk

I used Sika on my canopy, and followed the process used by two other builders... So the short answer is "You must use the Sika Primer!"

I think you may have entirely missed my point.

Nowhere in my post did I suggest that you should not use Sika primer. What I AM suggesting is that we should be using TWO DIFFERENT primers (one for the metal and one for the plexi), and that Primer 209N is THE WRONG PRIMER to use on the aluminum / steel side of the bond. It is the RIGHT primer to use on the acryllic. According to Sika, Primer 206 G&P is the RIGHT primer for the metal side of the bond. What I AM suggesting is that using the WRONG primer would likely result in LESS THAN OPTIMAL ADHESION on the metal side of the bond.

As everybody knows, proper surface preparation and use of appropriate primers is EVERYTHING in bonding. So has this been a case of the blind leading the blind? Has nobody come across this before? As I said, there seems to be NO MENTION of Sika 206 G&P primer on ANY RV builder website. How can this be? Is it a brand new product? Has Sika recently changed their recommendation regarding primers? RV builders tend to be careful and methodical, so as I said, I must be missing something. I just don't get it.

DakotaHawk · #4 02-22-2009, 09:32 AM

Yep! Now I see what you were saying. I'll have to look at what I used when I get out to the shop this afternoon. I'm pretty sure that I only used one type of primer. I still have all of the left overs, so I'll see what I can find. Maybe I did it wrong as well.

rv9aviator · #5 02-22-2009, 09:44 AM

Do you think it might have to do with the fact that most are applying the primer over scuffed powder coat and not bare aluminum or steel. I'm curious as I am getting ready to order my Sikaflex next week.

Gunter Malich · #6 02-22-2009, 10:14 AM

I think Jim may have hit the nail on the head. Check out what the demonstrator said during the last Jamestown video in Noah's initial message.

At 1:30 into the video, he states that "209N is critical for polycarbonate bonding.... and for bonding to paint surfaces like powder coat".

As long as you're using a powder coat frame, it looks like 209N is all you need for primer.

Noah · #7 02-22-2009, 11:29 AM

Quote:

Originally Posted by Gunter Malich

As long as you're using a powder coat frame, it looks like 209N is all you need for primer.

That MIGHT be true on a slider, but you're bonding to bare aluminum EVERYWHERE on a tip-up. For those building sliders, do you REALLY trust the adhesion of the powder coat? If it were me, I'd want to take it down to bare metal and use the correct stuff, but hey, that's just me.

Ken · #8 02-22-2009, 12:43 PM

Maybe the best thing to do is paint the surface with a urethane if it is not powder coated. Jamestown says of the 209D (replaces 209N), "It is used to prime painted surfaces and plastic substrates prior to bonding with Sikaflex products. 1/2 Pint."

Also see www.sikaindustry.com/primer_chart_4-21-06.pdf note number 10 for the type of paint.

Ken

penguin · #9 02-22-2009, 02:52 PM

I think Noah is correct, the bare metal primer is required if bonding to a tip up frame. I'm also having my slider frame sand blasted back to bare metal and re-powder coated with the correct primer under the powder coat. Every time I chip any of Van's powder coat there is bare metal underneath that has not been prepared very well - I'm also having the engine mount done.

Pete

scsmith · #10 02-22-2009, 02:59 PM

Anyone that has tried to remove powder coat from steel parts will attest that you are better off bonding to the powder coat with the 209 primer than removing the powder coat and using the 206.

The powder coat is incredibly tough, durable, and BONDED. the only expeditious way to get it off is to burn it off with a propane torch.

If you remove it and bond to bare steel, you are opening the door for rust anywhere that is not completely protected/sealed. Even the possibility of a light film of rust forming between the removal and sanding and the application of primer or whatever.