Which Sikaflex?

[Parksy]

I'm planning to install my 80w solar panel to the caravan within the next couple of weeks using aluminium Z brackets permanently bonded to the caravan roof with the panel on an adjustable frame bolted to the brackets. I will also need to fix a plastic cable entry box like the one in the picture below. This obviously needs to be permanently fixed and waterproof.
I don't plan on using screws or other fixings to bond the brackets or the cable entry box, just Sikaflex.

There appears to be two versions of Sikaflex available at the same price, 300 ml for £8.99 for either one.
One is Sikaflex 221 and the other is Sikaflex 512, is there any difference in these products that I should know about.
Is one stronger or more flexible than the other or are the setting times different? Will the Sikaflex work on both plastic and alloy?
Any advice which will help me to decide which one is the best suited for the job would be much appreciated

 

[Damian]

Use the 512.
It is a bonding and sealing mastic and is suitable for bonding aluminium to plastic or any substrate such as GRP or brick, wood, metal etc.

Make sure you use it within its temperature range nd make sure the surface of the van is thorougly clean and polish/grease free.

White spirit followed by Meths is the best way of cleaning the attachments points.

Another one you could use is Soudall Fixall which is excellent as well.

 

[xtrailman]

Also i have read from forums that 252 and 221, are good for roof bonding sat dishes etc

 

[Parksy]

Thanks Gents, I'll go for the 512 then. Will 300mm be enough? The picture that I've seen doesn't give much of an idea of relative size, is 300mm similar in size to a tube of bathroom sealant?

 

[Damian]

Yes the 300ml will be more than enough, in fact it will be too much really, so if you have any areas which need resealing it would be a good time to do them as well.

 

[Parksy]

Thanks Damian, I'll have a good look before I install the panel.