I had this daydream that on a pleasant Saturday I could pick up my boat and rest it on one shoulder. I could carry the paddle and life jacket in the other hand and walk the ½ mile to the local canal, launch the boat and paddle the few miles into the nearest town. I would padlock the boat to the railings of a canal side pub whilst I have a look around the shops and return to the pub for suitable sustenance and when ready paddle home again.
I have a 14 foot long Poly Pippin that I could use for such a trip, but it is not ideal. It is rotomoulded in plastic to such a thickness that it is almost bomb proof. This robust construction and the home made backrest I’ve installed means it weighs nearly 40 pounds. I did carry it back from the canal on one occasion and the bruises on my shoulders and hips took two weeks to fade (call me a wimp if you like but I’ll take personal comfort over a strangers opinion every time). I did devise a small set of wheels that could be carried inside Poly Pippin’s cockpit when on the water and strapped to her stern when on land; however pulling a 14 foot long trolley along twisting footpaths, up and down kerbstones, etc. is not the pleasant stroll as envisaged in my day dream. The route from my house to the canal includes a footbridge over a railway so I have to shoulder carry any boat over that. Also the canal has a number of locks and low swing bridges at which I have to lift the boat out of the water and carry it round. No, as pleasant as Poly Pippin is to paddle on the water, she is not the boat of my daydream.
So I looked at the requirements for my daydream boat.
- Light weight. I reckon that I can shoulder carry about 20 pounds the ½ mile without much discomfort.
- Cheap. If I tried to persuade the chief domestic accountant into spending thousands of pounds on a high tech carbon fibre ultra-lightweight boat that I will only use a few times on the local canal, she would rightly explain to me the error of my ways.
- Small. The rest of my family have no interest in boats so it only needs to be big enough to take me and a small rucksack.
- Easily propelled. An old tractor inner tube would meet the above requirements of light, cheap and small, but would be an absolute pain to paddle, especially against a current. I’m not that fit so a hull form that slips through the water easily is needed.
- Home built. I probably enjoy the designing and building more than actually using the end product.
So considering the type of boat to meet my requirements:
No power boat is going to weigh less than 20 pounds, or be cheap if it did.
Trying to sail along a canal is not easy – low bridges, overhanging trees, etc. I’ve seen youtube video of someone doing it in a duckpunt, but it’s not for me.
A row boat that is easily propelled tends to be long and thin with the oarlocks out from the sides of the boat on a space frame to get the correct pivot point for the oars, difficult to home make and still meet the cheap and light requirements. Facing backwards as you row alone along a canal is very likely going to have you bumping into overhanging bushes, the bank or even the occasional narrow boat. No, I need to be facing the direction of travel.
A kayak is a forward facing easily propelled small boat, but there are some drawbacks. In my Poly Pippin kayak I use a Greenland style double blade paddle. With a double blade paddle small dribbles of water run back down whichever blade has just been raised in the air and fall with remarkable accuracy onto your lap. In my day dream, after I have locked the boat to the railings, I don’t wander around the shops with wet trousers as if I had an incontinence problem. The kayaking fix for this is to use a spray deck. (Basically a waterproof skirt, the elasticated hem of which fits tightly around the cockpit coaming.) My day dream didn’t have me walking around wearing one of these like some cross dressing rubber fetishist either.
The real fix for water dribbling off the paddle into the boat is to use a single blade paddle where the dry handle end stays above, or at least at the same height as the wet blade end, which normally stays outside the boat. When I was growing up, boats where you traditionally use single blade paddles were either Canadian Canoes (North American Indian Birch Bark Canoes being the archetype) or dugout canoes with outriggers as favoured by the ancient Polynesians. An outrigger canoe wouldn’t be practical for a canal, trying to get out on the outrigger side and up a 3 foot high bank without getting wet could be difficult.
So my new boat will be an open canoe.
A canoe less than 10 foot in length would have to have a very wide beam if it is to support my 14 stone weight so it wouldn’t meet the’ easily driven’ requirement. There is limited space in my garage so to meet the home built requirement it must be less than 15 foot long.
So knowing it is going to be a canoe between 10 and 15 foot long, I visit the Duckworks boat plan index. Straight away two designs catch my eye, Gavin Atkin’s Cinderella and Skip Johnson’s EasyB. Both look to be well sorted easily driven designs with good reports from people who have built them.
Next I spent some time surfing the internet looking for ideas and inspiration. I like the idea of using a laminated composite structure that has a thick lightweight flexible core with thin stiff skins bonded on either side, a common enough concept in the boatbuilding world. For the Cinderella I toyed with the idea of building the basic hull shape in the thinnest plywood I could obtain, 1/16” would be ideal. This thin weak hull would then be lined with ½” thick expanded polystyrene foam sheet held in intimate contact with the plywood by suitable weights and clamps until the adhesive sets. Finally, with suitable bracing to keep the hull in the correct shape, an interior skin of the same thin plywood is bonded to the foam. The end result should be a boat the same weight as if built from 1/8” ply, but considerably stiffer. Unfortunately, very thin plywood is more expensive than the thicker more common variety; also my garage experiments with trying to bond thin wood ply to polystyrene foam didn’t go well. Maybe I’ll build a Cinderella some other time.
The EasyB design is strip built. Wooden strip built canoes are often beautiful works of art to rival Chippendale furniture; if I owned one I wouldn’t scrape it over the concrete edge of a lock to drop it into a dirty canal. However, strip building in polystyrene appears be cheap and simple, there was an article in Duckworks where a couple of gents in America built a lightweight Melonseed dinghy using the technique. Most internet wisdom tells you to use specialist closed cell buoyancy foam, not expanded polystyrene foam which ‘they’ tell you isn’t up to the job. Well most responsible boat builders create craft that are robust enough for unforeseen conditions and are destined to survive long enough to be passed on to your grandkids. I’m working to the ‘just fit for purpose’ requirement so it will be expanded polystyrene foam, bought from the local builders merchant, in my boat.
The real strength in a wooden strip built canoe comes from the thick glass fibre bonded to both sides of the wood – the composite beam principle. I just need the boat to be stiff enough to hold its basic shape when I’m sat in it, so just one thin layer of glass cloth each side of the foam should be enough. Normally, glass cloth is encased in an adhesive resin matrix, either of polyester or epoxy. Polyester resin is cheap enough, but apply it to polystyrene and the resulting chemical reaction will ‘melt’ the foam. With care epoxy resin can be used with polystyrene foam, but it is far too expensive for me to consider using. To resolve the problem a series of experiments were carried out in my garage. I tried to find a coating material that could be painted onto the surface of the polystyrene to protect it from polyester resin attack. The experiments were unsuccessful in their primary goal; however they did show that simple waterproof PVA adhesive bonded the glass fibre cloth to the foam very well. A 1” thick piece of polystyrene foam with thin glass cloth bonded to both sides became a lightweight, stiff, puncture resistant sheet that took a few weeks of submersion in water before it started to break up. My canoe is only going to be in the water a few hours at a time, most of its life will be spent in a dry garage, so waterproof PVA, which can be bought by the gallon, is going to be my glass adhesive. (I was half way through my build when another Duckworks article showed someone successfully using a boat made out of flat sheets of polystyrene that was skinned with glass cloth bonded with PVA).
Just one more decision, what level of quality am I going to build too? At work I have to abide by exacting standards so to provide a pleasant contrast at home my boat will be built by eye, with the minimum use of measurements. I will use the 40 foot quality standard – From 40 foot away you shouldn’t see too many of the blemishes and errors.
If this whole process results in a nice little craft most of the credit will be going to Skip Johnson for drawing up such a lovely lined boat. If it is a total flop the blame is on me.
Now the building sequence:
Print the full size patterns and then trace each of the individual stations onto cheap wallpaper up at the patio windows.
Glue Paper patterns onto 1 inch thick polystyrene. Then cut out with jig saw. (Glue paper on the reverse side as well if you don’t want these station moulds to warp as the glue dries.)
Make a 4” square strongback beam out of scraps (most of it was originally an MDF bath side panel left over from when I remodelled the bathroom) then mount the stations along it, paying attention to alignment and correct distance between them.
Apply PVC tape over the edge of the stations where I don’t want them bonded to the hull.
Mark the shear line with wooden sticks:
Run a 2 inch wide strip along the shear line sticks and apply adhesive between it and those stations I want to remain in the finished hull; hold the strip in place with cocktail sticks until the glue sets (I found silicon bathroom sealer works well as an adhesive here.)
Trim the strips to suit the bow and stern.
I tried various techniques for cutting the polystyrene strips, hot wire, Stanley knife, etc. A fine tooth pull saw worked best for me.
I made up a couple of sand paper faced profiled blocks to shape the edge of the strips to the necessary concave and convex shapes.
Stripping up the nearly straight sides was easy enough…
But turning the corner onto the bottom required some patience.
After sanding smooth the outside of the hull I draped the glass cloth over it and worked it onto the shape with no wrinkles.
A coat of waterproof PVA adhesive was brushed on through the weave of the cloth to bond it to the polystyrene underneath.
A set of 2 by 1 inch polystyrene gunnel strips were PVA'ed along the shear line.
The hull is now strong enough the be lifted off the stations that were not bonded in place.
The bonded in stations are cut down to the correct size to match the shearline.
Access holes cut in the relevant stations to make storage compartments fore and aft.
Inside sanded smooth and glassed with PVA (same as the outside).
Fore and aft decks added (they stiffened up the boat wonderfully). A ¼ by ½ inch strip of oak (recovered from old kitchen cupboard doors) was bent using a hot air gun and glued in place to act as a backrest.
Wooden bump pads doweled and bonded at each end of the gunnels to limit the damage from ramming any locks on the canal.
A 1 inch thick 'seat' bonded in the bottom to stop me sitting in the inevitable puddles that collect in the bottom of any small boat.
Internal and external gunnels rounded off and glass PVA'ed over them.
The whole thing was painted with black masonry paint. If this paint can survive on the outside of a house for 5 years of English rain then it will be good enough for a few hours of immersion in fresh water. Also, if the hull starts to break up the white polystyrene will show up.
Add a small skeg/rub strip along the bottom to aid tracking and take some of the wear when I drag the boat out at each of the locks.
Well she floats, doesn’t leak, isn’t too tippy and is very easy to propel at a normal walking pace with a double bladed paddle. She doesn’t have enough directional stability to use a single blade paddle (or perhaps my J stroke technique needs improving). If I use the double paddle with no feathering in a Greenland style stroke, keeping the blades low there isn’t the problem with water dribbling into the boat. The backrest needs some padding but overall I’m very happy with the result. My thanks go to Skip Johnson for providing such lovely hull lines for us amateur boat builders.
Well she’s had two reasonable outings so far: on both occasions I shoulder carried her the ½ mile to where a swing bridge crosses the canal, launched and paddled into the local town, which takes between an hour and 90 minutes depending on how many detours I take and how often I have to wait for the narrow boats. I’ve had one mishap – my own silly fault – I tried to limbo under a swing bridge and put all my weight on the oak strip backrest in a way that it wasn’t designed to withstand. It snapped, and it is now consigned to the bin. I’ve got a few ideas on the design of a MK2 back rest, but I’m in no hurry, she’s a pleasure to paddle even without it. An easy slow stroke with the double paddle, at a rate I could keep up for hours, propels her at a fast walking pace. Going faster is possible, but the extra effort required, along with all the water being splashed into the boat and over me, makes it undesirable. (If I’d wanted to go fast I’d have bought a K1 and spent months learning how to keep it upright.)
|The swing bridge that saw the end of the backrest.
Weighing only 23 pounds (possibly less now the backrest has gone) makes her easy to lift out and carry round the locks. The drawback to the low weight is cross winds will take you off course. She could have been even lighter if I hadn’t been so heavy handed with the PVA.
My last visit to the waterside pub was on a beautiful Sunday late in September. After lifting her out on to a ledge I enjoyed a leisurely stroll around the shops, bought a new book to read, then returned to the pub for lunch and a pint. It was exactly like my original day dream – a perfect way to spend a warm Sunday afternoon.
|Dry berthed at the pub.
Some words of caution should anyone consider using the same construction technique as me.
Expanded Polystyrene Foam (EPS) doesn’t have a great deal of compression strength (I seem to remember a figure of 7 grams per square mm, but don’t quote me). Even with glass cloth PVA bonded to is surface it will not withstand small point loads, the cloth ‘stretches’ and the underlying EPS compresses. The resulting loose cloth and ‘broken’ EPS takes in a little water in a sponge like fashion. This does dry out and the EPS does recover slightly after a day to two of dry storage, but it is never ‘as new’ again.
Within minutes of being placed in the water the waterproof PVA reacts and goes milky white. This was very noticeable on my black painted canoe. Again after a day of dry storage back in my garage the PVA looses the white colour and appears to be none the worse for it. Obviously, I have not carried out long term scientific testing on the effects of water absorption on EPS and PVA.
For me both of these effects are not a problem. I never intended to build something capable of white water expeditions that I could pass on to my grandchildren. You make your own decisions when building your boat and nothing I’ve said above can be taken as advice or recommendations.
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