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Post by karavaninkallista on Apr 12, 2021 21:08:48 GMT 10
After reading so many threads on waterproofing over plywood with calico (or canvas), I'm as unclear as ever. Opinions and advice please. Developments in adhesive and paint technology since 1950, let alone 1980, means I think I have more flexibility than the older methods. So, in a series of yes/no questions: - Pre-treat wood with undercoat before applying calico?
- Necessary to pre-shrink calico before application?
- Add adhesive to ply then apply calico, or use first coat of paint to act simultaneously as adhesive
- Five or more paint coats? Solvent or water based topcoats?
My thinking at this stage is a light coat of solvent-based undercoat, spray adhesive on surface then roll calico on (and squeeze/iron out bubbles and flaws), then paint of the same undercoat to protect calico and support adhesive. Then, a number of coats of protective paint - a flexible, water based acrylic latex paint such as Solarguard.
Barking? Or the logic purrs like a kitten?
With thanks, Richard
(Answers, in some future time, will be found here : vintagecaravans.proboards.com/thread/17996/bringing-50s-wooden-back-glory ) |
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Post by Roehm3108 on Apr 13, 2021 7:51:02 GMT 10
I've done this process on three vans now and to my knowledge none have failed. I know others have made slight variations but followed similar principles. In answer to your dot-points:
dot-point 1 - I applied a primer/sealer/undercoat (acrylic)
dot-point 2 - tried both ways and found no difference
dot-point 3 - Never used adhesive! roll on thick coat of paint and follow with calico while wet and let calico absorb paint
dot-point 4 - Yes! I used acrylic
This process is the one used in the original times and one van on which I replaced the roof the treatment lasted more than 50 years and failed only because it was stored in a low roofed confined locked garage most of its life and the heat in the garage delaminated the paint. Personally I think using a glue would be harder to do, as you really need to work fast to get air bubbles out when applying the calico.
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Post by karavaninkallista on Apr 13, 2021 8:02:54 GMT 10
Many thanks! The voice of experience on this site is a grand thing indeed.
I picked up a quality (Sika) spray adhesive to set some waterproof sheeting inside the cupboards, and thought that could be useful on the calico. If speed is the essence to ensure the calico is flat, then I'll go down that path. There was a thread I saw in which the calico was laid in foot-long segments and paint applied, so that's the go I think.
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Post by shesgotthelook on Apr 13, 2021 9:13:57 GMT 10
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Post by Koala on Apr 13, 2021 10:14:35 GMT 10
I may as well add my experiences.
I do not wash or preshrink the calico.
Don't attempt to do the job in full sun or on a very hot day as the paint will dry too quickly and form a skin before you have worked any air bubbles out.
I roll the calico on to a long tube and start one end of the van, apply a very liberal coat of paint about a roller width on a section across the van, roll on the calico and apply more paint on top of the calico and keep going like this until you get to the other end of the roof. The paint should seep through the calico as you use a roller to flatten it out. Don't try to lift the calico if the paint has dried at all or if you find any air bubbles later. Easiest with two people and if you have removed any hatches and hardware.
Koala
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Post by Mustang on Apr 15, 2021 7:55:20 GMT 10
Many thanks! The voice of experience on this site is a grand thing indeed. I picked up a quality (Sika) spray adhesive to set some waterproof sheeting inside the cupboards, and thought that could be useful on the calico. If speed is the essence to ensure the calico is flat, then I'll go down that path. There was a thread I saw in which the calico was laid in foot-long segments and paint applied, so that's the go I think. I'm a fan of Sika, so when I saw a spray product I purchased a can for a tricky job on our Walden. It didn't work, went back to the regular liquid Sika Contact Adhesive & it worked a treat. Just be wary ? |
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Post by tooleyau on Apr 15, 2021 21:43:29 GMT 10
This is an extract from the Lady Evelyn restoration.
Calico on roof.
While in Albury at the end of August we also picked up several metres of calico and chose a slightly cloudy day to roll the calico roof on. We didn’t want it drying out too quickly. We had washed the sizing out of it in a hot wash and spent 2 hrs crawling round the floor ironing the wretched thing. Calico wrinkles terribly when washed. We then rolled it up around a large cardboard roll to keep it as flat as possible. If we folded it, there would be creases. So with two tall ladders and one of us on each side we put about a metre wide layer of undercoat and sealer on the roof and proceeded to unroll and stick the calico to the roof. Once we got the first two metres done, it became easier. We ducked inside the caravan occasionally when we got to a skylight. Given the size of it, we didn’t do too bad a job wrinkle wise and no joins. Another 2 or 3 layers of undercoat and sealer and then two top coats – tight as a drum and leak-proof. When we bought the stuff we hadn’t measure the distance so made a rough guess and added some for shrinkage and a bit for luck. I think we had 10 centimetres left at the end to cut off.
After the roof was finished, and the calico was trimmed, the caravan’s edges were lined with aluminium J-mound and the sail rail was added for the awning. The roof skylights were also added and covered with tinted Perspex.
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