Sikaflex 221 for Edge Glue/Seal Primer Needed?

[Jeepnick]

Howdy Folks,

I'm a year into my TD build and finally nearing the skinning phase. I plan to use Sikaflex 221 to edge glue the aluminum (along with trim I will screw down) and let the rest float on the trailer.

Here's my question - I'm going to use The Mix and a final coat or two of pure oil based poly to seal the exterior of the trailer before skinning with aluminum. Sikaflex's instructions seem to indicate I may want to prime both the poly-treated wood AND the aluminum in order to get a good adhesion, waterproofing, elasticity, etc... Basically all of the things Sikaflex is so good for (from my reading).

Did you use a primer? I don't want to add an extra step if I don't have to (my todo list is 6 pages long), but I really want to get this right.

Thanks!
Nick

[tony.latham]

I don't think the Sikiflex is needed since your sealing under the trim. If moisture somehow makes it under the trim, where's it going to go? But that's just me. I'm quite happy that everyone doesn't build the same way I do.



But if I chose that route, I'd run my random orbital with 80 grit sandpaper along the edges. (If something doesn't stick to that, it's a poor choice of goo.) And I would wipe a rag with vinegar over the inside of the aluminum. If I felt it needed primer, I'd buy a couple of cans of self-etching spray primer from Napa auto parts (since paint doesn't like to stick to aluminum).

That should get your brain spinning.



Tony

[Jeepnick]

Tony,

Thank you for the response and information. After finding and reading Sikaflex's pre-treatment chart, it looks like they recommend light sanding the aluminum with a fine grit pad or paper. They also recommend using their "Activator" on surfaces treated with water or solvent based top coats. I'm thinking an oil-based poly coat falls into that category.

I may use the activator depending on cost (Sika is $$) but I will definitely abraid the aluminum as instructed.

Nick

[tony.latham]

Tony,

Thank you for the response and information. After finding and reading Sikaflex's pre-treatment chart, it looks like they recommend light sanding the aluminum with a fine grit pad or paper. They also recommend using their "Activator" on surfaces treated with water or solvent based top coats. I'm thinking an oil-based poly coat falls into that category.

I may use the activator depending on cost (Sika is $$) but I will definitely abraid the aluminum as instructed.

Nick

Six-bits says your building a fine camper.

Tony