Adhesives!! need some help Sikaflex vs 3M vs???

[mog]

This thread seems to be covering the composite end of adhesives, what is the opinion on adhesives for aluminum?
I am going to cut down the height of an aluminum Marathon truck cargo box (moving truck type) that is made from .040 aluminum sheet attached to galvanized strings every 16 inches.
My plan is to cut out 18 inches of the sides using metal circular saw and welding the stringers back together (after removing the galvanizing in the weld area), since they are steel. I'd like to add a double to the aluminum side with adhesives, so no aluminum welding.
I'd guess that flexibility would be lower on the list for this. Also the primers for Sikaflex seem to be crazy priced with no shelf life, so perhaps a 2 part epoxy ?
Any suggestions ?

Key
Black is side walls
Dark gray are wall butt-ends
Green is adhesive
Purple is doubler



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[bee]

Maybe I did jump the gun on ruling out these adhesives I keep see sawing back and forth.

I can tell you for 3m 5200. They don't seem to consider a primer necessary when bonding fiberglass, but it is necessary for metals. I guess even aluminum and stainless have enough corrosion to be an issue. I to was thinking to just paint the metal parts with epoxy to seal it. Seems like a much more cost effective way then buying their special primer that will go bad in the can. Anyone see a problem with this?

Also I had emailed 3m about my project and of course they said it was a good adhesive to use. They warned though that extended high temperature speeds up the degradation of the glue. This is the first time I have heard this, wonder if its true. Anyway they recommended not to use black paint on the camper cause of heat buildup.

 

[westyss]

I wouldn't get all worked up about the primer for sika, it will bond very well to the surfaces mentioned as long as the surface is very clean, I bonded aluminum to fiberglass with sika 252 and simply sanded the fiberglass surface to create a slightly rougher surface and remove any wax then cleaned all surfaces with acetone. the sika will be a very strong bond to the point that it will not pull apart and most likely will destroy the bonding surfaces before breaking the sika bond.
With the sika the surface does not need to be super smooth as you can lay on more sika to build up the indentation to create a contact surface as opposed to tape where the mating surfaces have to be fairly even. The sika can be layed on thick or thin to allow for expansion and contraction of different surfaces also, I believe that I used 3mm between the aluminum and fiberglass to allow for that.
Some of what i did is here: http://www.expeditionportal.com/forum/threads/48351-out-with-the-old-in-with-the-new/page2

I had about five minutes to get the ally where I wanted it and then it was stuck never to move again, sika cures with moisture which could be a consideration for a dry climate, I live in BC Canada and had no problems getting moisture.

 

[Clay]

Over the last few years working on old ships I can offer up some solid advice on both sikaflex and 5200. What I have experienced is that 5200 doesn't hold up to heat and being exposed to continuous sun. I put it on the roof top of the wheel house 2 years ago and had to go back through it all recently, because it started cracking and getting hard. Sikaflex is pretty good stuff, and I've used it more than 5200 over the years, on everything from sealing decking material down to both aluminum and steel, to sealing cracks of various shapes and size and on and on. It's good stuff, but not always so easy to work with.

Over the last couple years I've been using this stuff called Bostik 940fs, and it's the best thing yet. It does everything better than Sikaflex, you might want to look into it for your project as well.

Good luck!

 

[bee]

Thanks for the info. Never heard of bostik till now.

 

[Scoutman]

Did you ever make a decision on this? I'm about to bond some filon fiberglass siding to the roof of my truck camper. It will need to stick to wooden ribs and the foam that lays between them. No Aluminum and no luan. I've been reading up on the best stuff to use and I don't think I'm any closer than I was a few weeks ago. I just don't want to pay high dollar for some special product only to have it eat my foam insulation or not stick correctly.

So on the 3M 5200 product that ya'll keep referring to... it comes in caulk tubes but would you spread it out with a brush or is this mainly used for say gluing the fiberglass to the ribs only by applying a ribbon of 3M?

 

[magentawave]

Stuff like that is reeeeeally goopy with major tack so it would probabably spread better with a plastic body filler spreader or putty knife. Be sure to wear disposable gloves.

So on the 3M 5200 product that ya'll keep referring to... it comes in caulk tubes but would you spread it out with a brush or is this mainly used for say gluing the fiberglass to the ribs only by applying a ribbon of 3M?

 

[bee]

Did you ever make a decision on this? I'm about to bond some filon fiberglass siding to the roof of my truck camper. It will need to stick to wooden ribs and the foam that lays between them. No Aluminum and no luan. I've been reading up on the best stuff to use and I don't think I'm any closer than I was a few weeks ago. I just don't want to pay high dollar for some special product only to have it eat my foam insulation or not stick correctly.

So on the 3M 5200 product that ya'll keep referring to... it comes in caulk tubes but would you spread it out with a brush or is this mainly used for say gluing the fiberglass to the ribs only by applying a ribbon of 3M?

Normally with these adhesives you are supposed to use 1/8" spacers to prevent the caulk from spreading to thin. The thickness of the bead is what gives it its flexibility.
And no I never really came to a decision lol.

 

[magentawave]

Clay - Thanks for the information about how 3M 5200 doesn't like heat and sun.

I need to glue some horizontal wood "rafters" to the ceiling of a little 18' fiberglass Toyota Sunrader motorhome and also glue some vertical wood stringers or "studs" to the walls that I'll use as attachment points to screw cabinets and paneling into later. I've driven down those nasty washboard roads in Baja where anything not permanently attached will rattle to pieces so I need these "rafters" and "studs" to stay put so everything attached to them (cabinets, etc.) will stay put. I was thinking of using epoxy but it would be easier to use Bostik 940FS.

QUESTION: If I glued those horizontal and vertical wood stringers to the fiberglass surface inside my motorhome with Bostik 940FS do you think they would stay in place with a load on them - even after being rattled to death on a long washboard road...or should I use epoxy?

Thanks!

Over the last few years working on old ships I can offer up some solid advice on both sikaflex and 5200. What I have experienced is that 5200 doesn't hold up to heat and being exposed to continuous sun. I put it on the roof top of the wheel house 2 years ago and had to go back through it all recently, because it started cracking and getting hard. Sikaflex is pretty good stuff, and I've used it more than 5200 over the years, on everything from sealing decking material down to both aluminum and steel, to sealing cracks of various shapes and size and on and on. It's good stuff, but not always so easy to work with.

Over the last couple years I've been using this stuff called Bostik 940fs, and it's the best thing yet. It does everything better than Sikaflex, you might want to look into it for your project as well.

Good luck!

 

[Steve Works]

We used sikaflex 292 on the bottom of our boats at work. And it worked well enough,but I have heard good things about 3m

Same here. I've worked with Sika adhesives for years and can't complain about a single aspect.

 

[guidolyons]

FYI Jamestown Distributors has 3M 5200 on sale for 11.99 (10.99/each by case of 12) regular price $18.99-22.99.

http://www.jamestowndistributors.com/userportal/show_product.do?pid=2002&campaign=email062315

 

[java]

Well old thread here, but ill throw my input in.

Most polyurethane adhesives are not completely UV stable. Hence 3m makes 4000UV.

I have used Skia products for a long time in construction. They stick like mad, and are very flexible long term.

I have used 400 and 5200 on my boat, no issues with hardening, but 5200 does grab any dirt and dust it seems. Not that its still tacky, but its just "rubbery" enough.

IMO I would use sika for skinning a cube/rv box, their product is specifially designed for that purpose. But 3M also has their own VHB tape for doing it as well.

 

[rayra]

You'd do far better to bond to the raw material than to a paint layer on it. If painted you'd be relying on the paint bond rather than the adhesive's / sealant's. No point in pursuing a super-adhesive if you are going to put a paint under it first. Find and read the instructions / MSDS for your choice. Roughening of the surfaces to be bonded is usually recommended, a light scuffing with a low grit sandpaper is usually sufficient. Wipe your surfaces clean with an evaporative solvent like acetone or alcohol, before application of your adhesive.

 

[magentawave]

I ended up using Apex epoxy with microballoons (I don't recall now but I might have used a different powder) to glue/fiberglass my wood studs and cabinets to the sides and ceiling of my fiberglass shell RV instead of the goopy stuff like Sikaflex or the 3M. I decided that I didn't need the flex and the difference in strength between epoxy verses Sikaflex and 3M was radical. And since the dealer for the epoxy is only 15 minutes away, there was no shipping charge which made the epoxy a lot cheaper too. (I can hang my 190 pound body off the cabinets I fiberglassed to the walls and ceiling. This is a good thing to know they will stay in place when my teeth are rattling as I bump down those horrible wash-board dirt roads in deep Baja.)

 

[Ben Steiner]

Any input on what Sikaflex to use?