Shades of a boat – well, almost - February 2010

Maybe I just like stark skeletal structures but I find building boat moulds very pleasing; the sweep of the ribbands or stringers over the individual moulds seems to emphasize the curves of the hull and is the best way to appreciate the structure of the boat. I can believe that some builders will feel impatient with this stage, wanting to get on with the boat proper, but the secret is to forget that the mould may have to be sacrificed at some stage and to appreciate it as something quite sensual in its own right.
Anyway, this is where we're at just now.

In retrospect, I would have done better to have used 12mm rather than 9mm for the individual moulds as I found that the ribbands needed to be glued and screwed into the notches in order to counter the marked twist needed. The ribbands suggested are 22 x 15mm and were quite resistant to twisting. The width (22mm) is usually taken as the width of the lands (plank overlap) and is where a lot of the strength of the structure comes from.
Prior to adding the ribbands the notches are clearly seen.

Oddly, the hog (laminated from two pieces of 12mm douglas fir) shows a definite concavity or reversal of curvature about 2m from the stem - only a few mm but very visible. Puzzled, I asked Paul Fisher of SF about this and he was quite positive that the traditional cobles were like this. Not quite convinced, I'm planning a trip to the Northumbrian coast soon to see for myself. However, a new design has since appeared on the SF website for a full-sized coble where the deep forefoot and concavity of the keel are very obvious. Get this:

My mould has a false transom (vd Thom Hill) with a slot cut for the knee piece which is already glued and screwed to the end of the hog.

The other end of the hog is similarly fastened to the inner stem. Rather than laminate this, I built it up from two pieces of oak - for no other reason than that it looks nice and I'd not done it this way before.

The step on the inner surface is to support the sampson post; I've also extended the aft of the stem by 100mm to below the mast and added a third lamination (shown) to the hog at this point. Once the hog and stem are shaped to receive the garboard plank, the cross-section at this point becomes quite small and, without this reinforcement, is a potential weak point. (I found this to be even more crucial on the MacGregor canoe). (Voice from the future: the completed boat did indeed turn out to be vulnerable at this point - even with my reinforcements - especially as this is the point at which the bow roller on the trailer makes contact. Reinforce even more!)

The shaping of the stem to receive the planking then follows by fastening an extension to the end of each ribband and using this to progressively saw and chisel a slot on the stem at the point of the plank marks. Do this for each ribband but be careful not to lose your plank marks on the stem as you work; I make a small hole rather than trust to pencil marks. The waste between each notch on the stem can then be chiselled and planed away. The centre line on the hog is likewise at risk of getting lost and it pays at this stage to drill holes to mark the position of the centreboard slot; just one at each end will do - routing the slot can take place later, probably once the keel is fitted.

The hog is similarly shaped by making a series of saw cuts to the centre line using the nearest ribband as a guide. This ribband also serves as a guide for planing the hog smooth. The plane used has an extension bolted on and will be familiar to many boatbuilders. The only problem with wide beam boats is being able to stretch over the mould to work on the hog; I'm tempted to use a power plane but at this stage the hog and stem still lift free of the mould so this might be a better move once the guideline sawcuts have been made.