My aim is to build a canoe for camping trips. I’m a novice kayaker, 6’ 2” and 75kg. My experience of canoes is limited to very stable craft in excess of 32″beam. I decided on a Double-Paddle Canoe with a theoretical capacity of 90-110kg. Length about 13′ 6″. Beam 28″. Depth 10.5″.
Started by mocking up various length ribs, using strips of damp MDF (Cheaper than green oak !);
Brian’s basic formula for determining the longest rib, (beam x 1.35) +2 = 39.8”.
Rounded up to 40” it gives a reasonable looking profile. I tried a 41” which is far too flat bottomed. The other extreme is 38” which looks pretty unstable but would be fast and track well, if I didn’t fall out.
The 39” rib feels like a good compromise, bearing in mind that this is not the final profile as the addition of stringers will alter that.
Made a Steam Box entirely from workshop scrap. Unearthed an old, rarely used, steam cleaner which I hope will be perfect for the job.
Made quite a narrow box (11″ inside) as I will be experimenting with some variations on Brian’s plan so will only be working on a few ribs at a time. Chose plastic tubing instead of dowel for the supports. Added an ‘access flap’ just in case any small ribs disappear inside and have to be retrieved. Also like the idea of having the whole rib inside the box, instead of one end hanging outside, so both ends get an equal steaming. Used a piece of cycle inner tube as a ‘rubber gasket’ over the opening, to conserve steam.
Went to three sawmills today. Got all the timber for a 66 Canoe;
For anyone in my area, here’s were I went;
Local Green Bending Oak from John Moody in Sheepwash, near Modbury, South Devon. He specialises in marine timber so understands rib bending requirements.
Local Ash for the Portage Yoke from John Bradford at Wiggaton, near Ottery-St.-Mary, East Devon. A very small sawmill only dealing with local timber, mostly oak, ash and douglas fir.
Western Red Cedar from Devon Hardwoods at Newton Poppleford, East Devon. Importers of speciality timber. My Cedar came from Canada.
Prevaricating and more wet MDF!
Being a very newbie kayaker I’m obsessing about stability and freeboard. Decided to increase my beam to 29″, with a Depth-to-Beam Ratio of 0.375. This gives a depth of 10.875″. Adapted my rib test board and a 39.5″ rib looks about right, resulting in a Rib-to-Beam Ratio of 1.362 (I’ll call it 1.36 and shave 1/16″ off the rib length !).
Waiting for a new rip-saw blade to arrive, then I’ll fire up my steam box and confirm this with a real bit of oak.
Used every clamp I own.
Left the three lamination layers overnight, before gluing, with a weight in the centre to reduce rebound.
Reduced my centre post sheer depth from 7″ to 6 ¾”. Resulting rebound was less than ¼”
Final sheer = 6½”
When I set up a line to check the sheer I also measured a few rib locations either side of the centre and found the resulting curve was asymmetrical. May have been the weight of my clamps unevenly distributed. Not a problem as I’m building asymmetry into my design (more later). I just had to ensure the end with the most curve was aft and the end with less curve towards the bow, giving a bit more freeboard forward.
I used Titebond III glue and a roller applicator, which was perfect as the roller is the same width as the timber.
Also discovered (when I’d finished!) the thread on the applicator matches the Titebond bottle.
Depth Measuring Angst
Just realised that on my previous rib mock-ups I had been measuring canoe depth to the top of the keel, where the rib touches the keel. It should be to the bottom of the keel, ie. 7/16″ more.
Luckily I was still prevaricating over Depth:Beam ratios so I have now repositioned my ‘keel’ ;
Also gone back to a 28″ beam, to maximise elbow clearance as I want a little more freeboard.
Gunwale Layout & Asymmetry
Centre spreader 5″ aft of centre.
Front spreader 1 5/8″ narrower than rear spreader.
Check C/L with string …… only 1/64th out after gluing.
More springback but a weight on the centre spreader overnight resolved the issue
Had one fence for my router…..made a second one from leftover Velux skylight flashing.
Used a 6.3mm (¼”) bit but wanted 7mm wide mortices so left 0.7mm slack on the fences.
(N.B. Finding US measurements, especially 64ths, tricky ……converting a lot to Metric ….but trying to stick to ye olde feet and inches in this blog.)
Keel, Stems & Rocker
Set up keel stems and rocker.
Starting to look like a canoe.
Adjusting distance between trestles fine tuned rocker.
Prepping Rib Stock
Router radius cutter for rib corners
Rib Measuring Stick
The canoe asymmetry shows up on the stick.
I found it easier to do the adjustments in millimetres.
White oak rib stock looking good………steam bending tomorrow.
Traditionally the end grain on boat ribs is in the plane of the longest face, ie. ‘A’below;
This works for gentle bends on clinker built boats and is important because it avoids splitting by the copper clench nails. The guy at the sawmill persuaded me to go with the traditional orientation…..oh dear;
Always listen to Brian!
The good news is that when I cut new ribs in the ‘B’ direction, everything was fine….no probs.
The bad news is that I’m short of a few ribs now…. another trip to the sawmill.