Smoothing Canvas

[TNWilliamson]

I re-canvassed the Old Town last September and am now getting around to finishing the hull. I applied 3 coats of filler, rubbed vigorously with the canvas mitt, and put the boat away for these few months.
The now dry canvas is pretty rough, and if I paint it as is it will never look good. I'm curious what others have done to get a decent smoothness on their hulls, is sanding in order? A filler type of primer will help when I get to that stage, but it won't work miracles. What have you guys done to get a smooth hull?
Thanks

 

[mccloud]

You've waited long enough for the filler to cure, so now it's time to begin with the sanding. Yes, extensive sanding is often done to smooth the filler, moving to 100 then 180 grit, maybe finer. Don't get into the canvas! When it's smooth enough to suit you, then primer/high fill primer, one or two coats with light sanding, that is compatible with whatever the final coat will be. There were also some recent discussions on these boards about going directly to paint without primer. Tom McCloud

 

[TNWilliamson]

Thanks, Tom, I'll start sanding.

 

[Paul Miller]

I think a good comparison would be watching a pro mud tape on sheet rock. They lay it on smooth and don't need to do much sanding.

Rubbing the filler with the mitt is fine to push the filler into the weave, but not for smoothing out the surface.

The attached is a picture of a canoe filled and finished with with a bare hand rubbing. I then wait for the surface to flash over and get dull and then rub it shinny again.

I do virtually no sanding but it does take a bit of time to regenerate the skin on my hands.

I would suggest you wet sand with a good wet sandpaper. Sanding filler is much more difficult that plaster.

Good luck,

Paul

 

[1905Gerrish]

I also must mention that filler recipes have a lot to do with how the finish comes out on the canoe. We just changed to a different filler formula after restoring about 12 canoes and the last recipe was like night and day compared to what we had worked with before. Back to the original question, yes, lots of sanding as mentioned and I use an interlux high fill primer that makes life a lot easier. Good Luck!

 

[TNWilliamson]

So Paul, if I get you right, you are sanding your canvas with your bare hands, and this is better than sandpaper. Sounds painful.
To 1905Gerrish, what was the improvement you found with your new filler recipe?

 

[BCam]

I had a terrible time with my filler (first-time re-canvassing).

Mine looked like rough sandpaper in spots, marginal in the best spots and also had some sags, streaks and orange peeling. I thought I'd have to rip off the canvas and start over again. After about six weeks, I sanded it and, on the advice of Mark Adams, used auto-body glazing compound to fill the pin holes and low spots that wouldn't sand smooth and were too large to be smoothed by the primer coat. I used a flexible, plastic Bondo-type spreader to apply the glazing compound, taking care to feather the edges of the filled spots. After spot filling the worst spots with the glazing compound and another round of sanding, I went over the entire hull with the glazing compound, using the plastic spreader to apply a very thin skim coat before final sanding. I found that criss-cross, diagonal strokes with the spreader seemed to work best and minimized streaking. I don't know that I'd even call the final coat a skim coat since the plastic spreader removed most of it. I haven't primed it yet but the hull is now very smooth and I'm pretty confident that my painting skills are the only thing standing between me and a smooth finish.

Note that there are other postings on this forum addressing the use of auto-body glazing compound and, to the best of my knowledge, no one has had any problems with it failing down the line. I used 3M's Bondo Glazing and Spot Putty (#907), which is a one-part compound since I wanted to keep it simple and not have to deal with the complexities of mixing in a hardener, plus I didn't want to put anything on the hull that might be too much like fiberglass. Only time will tell if this was the right decision. Maybe others will chime in on this. I used about 3 1/2 3.5 oz tubes on my 15' canoe, most of which was sanded off.

 

[TNWilliamson]

I'll look into that, I'd be a bit concerned that the glazing compound might not adhere to the canvas long term, but I guess it sticks pretty well upon initial application?
How did you sand, and what type of paper worked best?
Thanks

 

[Dave Wermuth]

Another thing to consider: I used to singe my canvas prior to filler up until one day when I experienced a near catastophic incendiary event. Since then I quit singeing. However, the fuzz from the canvas tends to make the surface after the first coat of filler quite rough. It has to be sanded smooth at some point. I like to sand it smooth after the first application of filler and then fill it again.

 

[BCam]

For most of my sanding, I used 120 - 180 grit "Gator Power Red Resin" sanding discs on my random orbital sander. I also used some 80 grit initially on the roughest areas but it was a little too aggressive, 100 grit would have been a better choice. I found that I had more even results with the sander than by hand when sanding large areas. If you use a light touch and keep the sander moving you should be OK. The flatter areas are easy but you need to be extra careful at the curve of the bilge to not use too much pressure or you'll sand through the filler. Again, I found that a criss-cross pattern worked best.

For hand sanding I found that 220 grit drywall screen worked well and didn't clog. I backed it up with a piece of firm foam from an old backpacking sleeping pad so it would conform to the hull with even pressure. The 220 grit drywall screen doesn't seem nearly as smooth as 220 grit sandpaper. I did all my sanding dry and it wasn't too messy plus I didn't want to have to wait for things to dry before applying the glazing compound.

After I did all this, I decided to read the instructions for my primer (Interlux Pre-Kote) which calls for 120 grit, so I did an overall, light final sanding with the sander and 120 grit to give the surface some tooth for the primer to adhere. I think this is especially important for the areas covered with the glazing compound since it tends to get pretty slick when sanded with the finer grits.

If you're concerned about the glazing compound, and don't have low spots, you might want to hold off until you've sanded at least one primer coat to see if it's necessary. I considered doing that but I had some gouges and dimples that primer I knew primer wouldn't conceal. I think my filling problems were a combination of lack of experience and our hot, California temperature (around 100 degrees the day I filled the canvas). The first coat went fine but after that, I never seemed to accurately judge when it was time to rub with the canvas mitts.

 

[Canoeal]

The process I use is this: fill the canoe rubbing filler standard type recipe with mildewcide in the filler, rubbing it in with canvas mits. Go over it a second time filling any dryish spots. Then smooth the whole thing rubbing by hand. I do singe the canvas, make for a smoother coat. Lighty go over the whole canoe with 220 grit after it is hardened. Paint I use Pettitt paints adusting the color to suit, rolling and tipping with a brush. Wet sand in between coats with 220 or 320 grit wet/dry paper. Four coats should do nicely.

 

[Greg Nolan]

As to 3M's Bondo Glazing and Spot Putty --

I have used it with no problems, albeit only over the relatively short period of three seasons. Though called "putty," the stuff has a consistency just a little thicker than heavy cream. It's usually available in 3 or 4 ounce tubes for about $4 -- but auto supply places often have a 16 ounce tube for about $8.

When I got my 1931 OT 50 pounder in early 2009, the paint needed some work:



I did some minimal sanding by hand, filled many cracks and scrapes with the spot putty, did a bit more minimal sanding, and painted (with water-based paint porch and deck paint):

and decorated with paints left over from one of my daughter's high school art projects:


Last winter, after two seasons of use, but wanting to experiment with a slightly different triangle design, and having got my hands on a cheap random orbit sander, I decided to repaint. I sanded a lot more thoroughly than before the first repaint:



spot primed with spot putty, where canvas was exposed because the filler had fallen away, over exposed filler, and over old paint, and then repainted (with the same water-based paint):



The spot putty is easy to apply, dries very rapidly, and is easily sanded. During three seasons of use, some small bits of paint chipped away, always because the original underlying paint/filler came loose. The Bondo spot putty has held tight.

Because I expect to be recanvassing in the next couple of years, I have always treated painting this canoe as an ongoing experiment, and have not tried for anything other than a functional finish (while fooling around with a bit of decoration). But I have learned a few things -- for example, that semi-gloss light-colored paint gets dirty to easily from crud in the water, although it can be cleaned without too much work. I have learned that it is very easy to touch up when slightly scratched or dinged. I have learned that it is just about impossible to sand old crackled paint smooth.

My experience with the Bondo spot putty has been good -- unless I were to hear from others who have had negative experience, I would not hesitate to use it again, even on a paint job that I would expect to be long term.

 

[TNWilliamson]

Thanks, BCam, I appreciate your ideas. I did think I'd try a high-build filler-primer before I tried any glazing compound. I have some drywall screen around here somewhere and I'll try that, too, if I can find the stuff.

 

[BCam]

I have no idea if it's a problem or not but if you prime first, the glazing compound wouldn't be bonding directly to the filler. I suppose it could be an advantage. Maybe someone knows.

 

[1905Gerrish]

I have used the glazing compound many times, probably every canoe I have canvased. I have used it directly over dry filler ( month) and I have used it over primer and paint. Have never had any issues. Jerry Stelmok recommended it to me many years ago. I used the green stuff that is supposed to be waterproof.

To TNWilliamson, the newer canvas formula that I tried was a can of probably 30 year old Old Town filler that we got with a canoe that we purchased. Talking to our canoe buddys, we all agreed nothing could go bad in it and we gave it a try. After using it and seeing how well it worked I contacted Benson to try to find out the formula. He sent me a few that I believe he got off this forum. I believe I found the one that I used and comapred to what we had previously made it had less silica and varnish and more porch and deck enamel. We still add a small amount of lead to our filler, usually a pound or two and mildicide.

 

[Benson Gray]

Those Old Town filler formulas are available at http://forums.wcha.org/attachment.php?attachmentid=12746&d=1285726273 if anyone else is looking for them.

Benson