Started on the roof this weekend - and it is a lot more difficult than I thought.
First thing I had to do was to strip off the blue paint on the steel - and for a paint that is supposed to be "temporary to protect the steel during storage" it was very difficult to get off. Anyway, after a full day of stripping the frame got it's epoxy etch primer sprayed on - at least the top half of the frame did - I still have a few mods on the lower part of the frame at the back I want to do so I deferred some of the stripping on the lower half of the frame.
I had to leave the etch primer for 16 hours before I could start to put the Sikaflex system on so I went to the beach on Sunday :sombrero:
Yesterday - being a public holiday here in Queensland I started with the first of the roof sheets. I had two of the sheets bent to the correct shape by the sheet metal shop last week. The test fit seemed to work good so I started the process. First I marked up the areas of the frame on the sheet using a marking pen. Then I sanded and cleaned the frame with the Sika cleaner - then applied the Sika 106 G+P primer (wear a proper carbon filter mask - that stuff will make you head spin). Then I did the same to the aluminium sheeting. Finally I cut up the rubber spacers and stuck them onto the frame.
With everything ready , I started to apply the Sikaflex - the pneumatic gun is great - pull the trigger and half a second later the glue comes out, let go and an it stops instantly - the rate of flow is constant - so all I had to do was keep the travel speed constant and I got a nice constant bead. It was all going well at that stage.
Next I had to lift the sheet on - and that's where things got difficult. Trying to lift on a 2.4x1.2 sheet, get it to line up without getting the glue all over the place was very difficult by yourself. I tried to tilt it up and lower it down but ended up slight skew - and the Sikaflex grabs tightly. I spent the next 15 minutes clamping, levering, pulling and pushing to get the panel lined up straight - then having to clamp and hold the sheet in place - to keep the gap constant. In the end - I got it in place- but the was a few areas where the glue got pushed out over the edge of the support in my efforts. Maybe I put to much on, but in the end the sheet was a lot more difficult to move once it had it's initial grab than I though it would be - added to the fact that the folded sheet was a tight fit in the first place.
I have a fair bit of clean-up to do on the inside - but the sheet is on, at least within 1-2mm of being perfectly straight and all in all I was happy with the result. After 5-6 hours I release the clamps on the rear edge and trial fitted the next sheet - and that's where I discovered that somewhere, somehow I must be 15-20mm out.
When I lined up the next sheet - things would not line up - it I line up the folds - the the edges are 15mm out, if I line up the edges, the folder are 20mm out. The only was I could get both the folds and the edges to line up was to skew the sheet slightly - I clamped the one edge so it butted up against the first sheet - the skewed it across so that the folds line up and the edges line up - and then it works - but that means I have to trim off a thin wedge. This does not make sense at all to me - I spend about an hour measuring, running string lines etc and even call in a friend to help. The bottom line is something is skew - not sure what or how, but it seems like in my welding in all the bracing has pulled the frame skew somewhere and the only way to fix it is to trim the sheet.
Late last night I transferred the marking across and with a 1mm blade on the angle grinder, trimmed the sheet. Now it lines up - but the supports on the frame don't - so I cut them off and re-welded them in the right position. After wire brushing back I re-applied the epoxy primer and that's where I left it. I'll have another look tonight and see how things are.
I took a whole load of photos - but did not down load them form the camera - I'll do that this evening and add to the post.
For the next sheet I want to try a different method. My plan is to stick the rubber spacers on like before, but then lay the sheet on, clamp it in place, and with the glue gun, squeeze the Sikaflex into the gap. What do you think about that idea?
I'll try clamping and the Cleco's - see what works best.
