A Canvas Roof?

[Steve_Cox]

Ira,

I saw what you did on that text, it justs showed me my own computer, browser etc..... It wasn't really spying on you. The guys were just teasing you.

[Jiminsav]

I'll be covering my new Tear with canvas, putting some aircraft dope on it, and then painting it..wish me luck.

[Laredo]

Ira?
I'm confused, I think ...

Hey Steve -- can you provide a link to that gnome /elf / script thingy?

I know this really cool website where it would be the most delish trap...

[GPW]

Jimin , worked for the Red Baron , eh ???Super lightweight ... you might look at the newer aircraft covering materials ... dacron , etc...

[Big Dave]

What about just using Sunbrella?

http://www.sunbrella.com/usa/

Or even Haartz Stayfast?

http://www.cyber-bridge-marine.com/convertible-top-material.html

[Jiminsav]

already got canvas, and dope was $47 a gallon, so i'm all set.
and in fact, I was thinking of painting it red, with a gold roof..

[Jiminsav]

already got canvas, and dope was $47 a gallon, so i'm all set.
and in fact, I was thinking of painting it red, with a gold roof..

[Denny Unfried]

One thing to consider with canvas covering ~ Many of the camp sites classify soft tops/sides as tents and in bear country they won't let you overnight.

[GPW]

Bears !!! That changes things considerably!!!!!!! ....all the food somewhere else ...

[Jiminsav]

Denny, it won't be soft..there is wood under it.

[angib]

If paint wouldn't work, are there any other options to adhereing canvas to wood?

As this message had rung a bell when I read it, coming across the 1950 Mechanix Illustrated boat plans book (bought by my father, I hasten to add) in the chaos of my study, I've looked up what they call for. A couple of plans say:

- "6oz canvas bedded in canvas cement, turned over the edges and fastened with copper tacks" - this is a boat with a small cabin, so about teardrop-sized.

- "Cover with 10oz canvas bedded in marine glue" - from a bigger 'cabin cruiser'.

So that's not a big help, but they do all talk of fixing the canvas down with glue (and then painting it), not with paint.

And is it worth mentioning for anyone confused that this thread has been talking, simultaneously, about two entirely different ideas?

1) Using canvas (or other fabric) as a waterproofing layer over a solid (typically wood) base.

2) Using fabric* stretched over an open framework. The fabric is then stiffened and made waterprooof by coating it. Traditionally this was done by doping it (which had the major advantage that the dope shrank the material, pulling it drum-tight) and then paiting it with enamel paint. The modern equivalent is to coat/impregnate the fabric with epoxy resin to make it stiff.

*For aircraft this was always 'Egyptian Cotton' - I don't think the nationality of the cotton mattered much to how the plane flew, it was just that they produced the best in the world.

Andrew
CEO, Old Farts 'R' Us

[Steve_Cox]

2) Using fabric* stretched over an open framework. The fabric is then stiffened and made waterprooof by coating it. Traditionally this was done by doping it (which had the major advantage that the dope shrank the material, pulling it drum-tight) and then paiting it with enamel paint. The modern equivalent is to coat/impregnate the fabric with epoxy resin to make it stiff.

Andrew
CEO, Old Farts 'R' Us

Andrew,

Excellent reference and clarification that the thread had evolved into two different applications of canvas. When I was experimenting with the 10oz canvas stretched onto a frame and epoxied the other day, it didn't shrink, in fact it stretched a little as I brushed the epoxy on. Do you know what it is about "dope" that causes the shrinkage? Maybe I should have preshrunk the canvas, and also I was using a laminating epoxy and it could have used some thinning before brushing it on.

[angib]

Do you know what it is about "dope" that causes the shrinkage? Maybe I should have preshrunk the canvas, and also I was using a laminating epoxy and it could have used some thinning before brushing it on.

My understanding (I've never done any of this, mind) is that dope shrinks when it sets (and keeps shrinking a bit thereafter). One of the important qualities of decent epoxies is that they don't shrink on setting - it's one reason why they are such good adhesives. I think people who want to use epoxy to 'stiffen' a flying surface apply it to Dacron.

Here is a nice description of the use of dope that I came across, by the Australian War Memorial (museum):

While the chemical process involved in the doping of a fabric surface is complex, the physical process can be relatively simply described:
• Fabric (cotton or linen) is stretched and sewn into a tight bag covering a frame of wood or metal.
• The fabric surface is then coated with a thinned layer of tautening dope.
• Once the lower layer of dope has dried it is sanded smooth. Subsequent layers of dope with a decreasing content of thinner are then applied, the dried surface being lightly sanded before each new coat.
• The final coats applied to the surface are undiluted dope lacquer.
• The surface is then left to tension up and become tight, rather like a drum skin. At this point, the fabric surface is hand stitched to the framework of ribs below the surface to prevent it from shifting or vibrating and the stitch lines are covered with fabric tapes to seal and protect them. Again this surface is painted with full strength dope and is sanded. (Sanding greatly smooths the surface of the fabric resulting in a surface with significantly less resistance to airflow and substantially enhanced aerodynamic behaviour.)
• The final cosmetic paint coats are then applied to the fabric surface.

Andrew

[jagular7]

Denny, it won't be soft..there is wood under it.

So you plan to 'skin' the camper in canvas with an interior wall? How would you insulate the camper? How would you protect it from moisture in the air between the interior wall and the outer fabric?

[Jiminsav]

Mike,
I have a inner and outer skin, just don't feel like painting plain ol' wood, so i'm covering it with denim and then doping and painting that..just to be diffrent.
as for moisture, dope is water proof, and so is paint, so water ain't a problem.

as for how Dope tightens cloth, well, it is made with Nitrate cellulose, which, when it dries, tightens up by contracting the cellulose, kinda like wool when you wash it in hot water..it shrinks, and, as it's stuck to the fabric, it pulls it tight also.

but, also, since i'm lazy, i might just paint the wood and say the hell with it.