Canvas Hull

[BlueSpruce]

On another thread recently posted Tim and I have been discussing refinishing my new 1963 E-Scow. Traditionaly a varnished hull, canvas topside. This boat will live on a trailer. Never in the water for more than 8 hours at a time. So it will not have time to soak and get tight. She is double planked, glued and screwed construction.
My first thought was to caulk minor cracks and dings with 5200 and varnish.
Varnish or recanvas topside.

So my wild thought was. What about canvassing the hull? Like a canoe. Would it produce a water tight hull? Wieght is not a major issue.
Durability?

[Wooden Boat Fittings]

Yes, you can get a perfectly watertight hull with canvas. You need to provide at least two or three good coats of paint to it to make it so. Then I'd give it another coat every year. Once painted, the canvas gets very tough and leathery.

As to durability, that of course depends on how you treat the hull. I've had my canvas kayak Kareela in ocean, river, and stream for nearly half a century without holing her, and she's remained completely watertight for the entire period (except when I've rolled her....).

Mike

[Ron Carter]

Wood canvas canoes are very common in some places. The canvas is stretched over the hull and then filled with a paint like compound rubbed into the weave and then painted multiple coats. The canvas is one piece and is seamed at the stems. I doubt you can buy canvas wide enough to reach from gunnel to gunnel and the bilge boards would present an interesting problem for sealing. Canvas, filler and paint to cover adds nearly 25% to the finished weight of a canoe. I suspect on an E scow that the canvas should be bedded in paint rather than loose on the hull or the speed on a reach is liable to peel it right off of the boat. Sounds doubtful, but it's your boat and you have the final decision.

[BlueSpruce]

Thanks for the thoughts Ron & Mike.
I think I may just sand, caulk and finish this year and see how much water she takes on. I want to find a long term solution that will preserve the boat for the future. If she takes on too much water I may need to do it now.
I should be able to find canvas wide enough. The decks on older E-Scow's are canvas and the bottom is so flat that it is not much more width than the deck. Also the rudders and bilge boards have brass plates around the through holes. The canvas could be sealed under these plates.
Weight? though not a major concern, I guess could come into play if it is above a 20% increase.
Any other thoughts or ideas would be greatly appreciated.

[Todd Bradshaw]

Canvas filler makes for a tougher, smoother hull than plain paint. It's a mixture of what looks like flat paint and powdered minerals (like flint). It is applied with a brush and rubbed into the weave with a big canvas mitten, usually in three coats with a final rub-down with a bare hand to smooth the last coat. Then it needs to dry for several weeks before priming and painting. The result is a very smooth and surprisingly tough skin. The bad news is that it is pretty heavy. I have an unopened gallon of Old Town Canoe Filler that weighs over 12 lbs. You would probably need 2-3 gallons to fill a scow. Added to probably 12 oz. to 16 oz. per sq. yard for the raw canvas, it would certainly add some fairly substantial weight to the boat.

I doubt you would need to glue it on. The big old freight canoes did not have their skins glued on and they were motored faster than you will be moving in a scow, as did some of the sport boats built by the canoe companies. The non-glued skin will also be removable and/or replacable should the boat ever need repair.

It's also possible to use heat-shrink aircraft Dacron in a similar manner and fill it with epoxy. It's thin, hard and quite a bit lighter. Due to the rather unusual tearing properties of Dacron, it won't have as much tear strength but it would probably be fine for a sailboat as long as you aren't constantly grounding out.

[JimConlin]

If you intend to race, or if you are concerned about the boat's future value for that purpose, i'd think twice about adding the weight of canvas or another fabric skin. The argument against 5200 is that while it seals well and holds like sin, it's hard to remove, so any further maintenance will be made more difficult. How about something reversible, like paint and slick-seam?

[BlueSpruce]

Point well taken about weight. I have no intention of racing and resale value is not a concern. I am more concerned with using while preserve the boat integrity for the future should somone ever want to do a complete restoration.

So if I scratch off Canvas and fiberglass. What is left. Caulk & paint?
Jim, what is "Slick-seam"?

[Tim B]

I looked into canvassing the hull of my scow too. Conclusion was it was a very heavy way to go. Putting a layer of e-glass and epoxy over the hull is a much better solution in my opinion. Here is a link to a site that details this being done to an A scow.
http://personalpages.tds.net/~flypig/cindylou/home.html

Look in the restoration section. I didn't get a chance to dig out the re-cavassing the deck instructions for you yet but have not forgotten.

tim

[BlueSpruce]

Tim, How did you e-glass your hull? Filler, epoxy, glass, epoxy, varnish? What did you do inside? Because it is trailered I suppose I would not have to worry about sealing both sides? Is your hull water tight? The link for the C-Scow project you gave me on the other thread describes them still having problems taking on water after glassing over.
Pat

[JimD]

Filler, epoxy, glass, epoxy, varnish?

The standard way is to glass first, then fair with filler. The reason is filler such as microballons is not very strong and you don't want it sandwiched between the wood and the glass incase it gets unstuck from the wood. It's been known to happen.

[MuddyFeet]

I don't think it applies to an E-Scow, but you can't canvas a hull that has a hollow, or reverse curve. When stretched, the canvas will not lay tight against the hollow area of the hull. Perhaps obvious...

[Tim B]

The process I used for glassing my M scow was very similar to the A scow web site I link. I emailed some of the people on that site for info. Here are the steps I took:
0. Start condition for hull was outside: paint over varnish, inside: varnish - good condition.
1. I stripped the outside of the hull to bare wood. There was some rot in the frame of one of the bilge boards. I was able to cut/drill out the rotten section and fit a dutchman, which was epoxied in place. No other rot (I looked very carefully). Filled a few dings and checks (splits) with epoxy/wood flour mix. Sanded hull smooth.

2. Covered hull with two sheets of 4-oz e-glass. Each sheet covered 1/2 hull and the sheets overlapped about 4-6 inches in the center. Hull prep had taken most of the summer due to busy schedule so cedar planking was very dry. The cloth ended at the transom. I did not attempt to fold the cloth onto the transom. The transom I left un-glassed.

3. After putting cloth in place I started wetting it out with unthickened epoxy. Some here suggest CPS on bare wood first. Once the cloth was wet it stuck to the hull well. I think it took me two evenings to finish wetting out the whole hull. I did one half and the other the next night. As I would come to an area like the bailers I cut the dry cloth right before I wet it. That way I didn't need to worring about how the cloth would stretch. The holes for the rudder posts and the bilge board slots I covered over with cloth, wet the cloth and went back about 30 minutes later (the cloth was still wet but stuck to the hull well) and cut the holes with a sharp scissors.

4. After the epoxy was dry (about 2 days later) I went back over it with more epoxy filling in areas of the weave that was still showing.

5. I had one section about 2x2ft square that would not cure. I think I must have mixed up a cup of epoxy wrong. I had to cut out this section of cloth (scissors) and clean it up with vinegar. Then I made a cloth patch to cover the area and tried again. Now that it is sanded and painted I don't think I can find that spot again.

6. After 2nd (3rd coat in some areas) coat of epoxy cured it was back to sanding. The fiberglass coat becomes much smoother than the wood itself can.

7. After that it was normal finishing stuff. My hull is painted because I think to much bright wood is overwelming. Filled in some low spots that I missed. Sanded some more. Primed, sanded, primed. Good primer is a must. Then finished with some Interlux.

8. The results. I have had the boat in the water 2 summers (trailered) since refinish. After the first winter I noted a hairline crack in the finish about 4 inches long down the center under the front of the cockpit. It aligned with a plank seem. Probably a high stress point near the mast step and bilge boards. Water leaked through this hair line and would result in a puddle on the cockpit floor. Hardly a leak at all. I have since found that if I run my finger over the point with a bead of flexible caulk it will not leak at all. This lasts the season.

Tim