Using Sikaflex 252

[westyss]

sika 252

I gotta put my 2 cents worth. I did not use any rubber or spacing at all and my gap stayed constant. What I did was use the provided nozzles that had two components to it, 1 - a vee that built up a pyramid like shape on top of the blob of sika that you lay out with the other component of the nozzle 2- the gap producing ,flat blob of sika that is very hard to squish out of place. This is an adjustable thickness by cutting the nozzle end that gives you a lay up of sika to your desired gap thickness.
the pyramid part is what grabs and holds your sheet, this is flexible to either push closer or pull further from your frame to get an even surface. With the rubber gapper you are using there may still be some waviness to the frame alignment. The flat blob , like I said is hard to squish, so that provides your gap. Clamping really wasnt required. If you want to reduce the gap, then clamp, more gap, use a new nozzle with less of the spacer cut off it. Works very well.
Yves

 

[Iain_U1250]

After discussion with the Sika technical people, I think that the "squeeze the glue into the gap" will work, with a bit of modification. I need to ensure that enough of the glue makes good contact, and that there are no voids which will weaken the stuff substantially. I will stick on the spacers, but add an extra 3mm spacer to the corners - thus raising it up a bit, after the glue is in, I can squash it down ensuring there an no voids, and I get enough surface contact area. Remember that the roof is around 3m up in the air - my ladder does not go far enough so getting the sheets up there is quite a mission.

Tomorrow night I'll measure up for the last of the off roof sheets, and get it bent up at the sheet metal shop. Then give it all a try this weekend. All going well I should have a roof over my head by Saturday evening

PS Photos added to the original post

 

[Iain_U1250]

I glad to report that everything went well this weekend -and that I have all the roof sheets on. The method of placing the sheet on spacers and then adding the glue afterward worked well - I think I got a good bond on the sheets, and everything lines up properly. After 4-5 hours, I removed all the rubber spacers, and filled in the voids with Sikaflex.

I'll download the photos tonight but I am happy with the result. I am confident the I don't have voids as when pushing down on the sheets to get them level with the adjacent sheets, the Sikaflex squeezed out of the gaps.

It was also less messy than the with the first sheet. So far I'm using one tube of Sikaflex per sheet - which is what I though I would - I have another 9 sheets to go and 9 "sausages" left. The pneumatic glue gun is great - if I had to be manually squeezing it all the time I would still be there.

 

[JRhetts]

Another editorial comment:

Sikaflex 252 seems to be a great product, but it does manifest one irregularity.

We have made literally hundreds of different 'glues' with it, and the unpredictability is in cure time.

We are in the desert (<30% humidity most of the time) and it is cured by extraction of moisture from the air. Sometimes it cures quickly in a matter of hours, and sometimes we have to give it up to a week for it to cure solid. Never can tell in advance which, but if we play it conservatively, we get great adhesion in the end.

 

[Iain_U1250]

Thanks for the heads up - I've found that the cure time in the batch I have is fairly consistent - it "skins over" in about 20 minutes, and and 3mm bead is dry in about 6 hours - well dry enough not to move. I only work on the truck on weekends mainly, so if I finish up on a Sunday, then it;'s a whole week before I touch it again.

On thing I have found, in area where I've messed up - it is much easier to wait until the Sikaflex is hard, the trim the material off with a Stanley knife blade than to try and use a cloth to clean up. The Sikaflex cleaner works well in removing the thin skin left over after shaving the rest off with the blade. It is a much cleaner and easier process than trying to clean up as you go.