Just a bit of fancy

Work has slowed down quite a bit now. Epoxy is slow to set in the lower temperatures and I also have to stick to a monthly expenditure of about £150. To avoid the winter condensation in the workshop/polytunnel - heavy enough sometimes to make it look as though it had rained inside - I've lined the inside walls with bubblewrap and it seems to do the trick. The cold wet weather has also prompted me to clean the place up a bit so that I'm now not tripping over loose offcuts, cables, etc. Long ago, when I was trained as an engineer, leaving the workshop spotlessly organised at the end of each day was almost like a sacred commandment - every tool in its place and not a shaving in sight. Sadly, I have to report that the lesson didn't stick.

However, the framework towards the bow has progressed a little and I'm starting to think about the centreboard casing, the base for which needed to be widened on either side of the hog. I'll use a 10mm steel centreplate - weighing about 35kg - which will require a beefed up structure to hold it, especially the pivot bolt size and the doublers but that looks increasingly as though it won't happen until after Christmas.

The most pleasing stage though has been the completion of the gunnels complete with shaped spacers. These are totally unnecessary but I just like the look of them (of course, they hark back to the early boats where frequent ribs ended at the gunnels). In theory, this type of gunnel is a bit stronger and you could tip the boat on its side to drain it - yeah right! - it's getting heavier by the moment - about 125kg now. One lesson I've learned from past experience is to make the spacers thick enough (eg min. 15mm) so you can get a) a paint brush and b) one of your fingers between the inwale and the outwale.

Another bit of progress is that I've found a mobile crane operator who was confident of being able to lift the finished boat from the back to the front of the house. Now that was a relief! I plan to sell tickets for the performance!

Fiddly templates and more brooding

Did I really say that after turning the hull, everything would be straight forward???? I mean, what planet was I on? Practically everything that is fitted inside the hull turns out to be a really weird shape, involving cardboard templates and loads of wood rasp and spokeshave work; all takes ages - but then what's the rush? - winter is on its way, and epoxy resin work is going to become limited by the low temperatures. In this connection, the resin supplied by Fynne Boats congeals in the tin below 9C whereas with the West System, it's the catalyst that seems to get a bit treacle-like at low temps. The helpful people at Fynne Boats suggested heating the resin in a jam pan - and it seems to work OK - nice and runny once more - but I'm not sure I'll risk making jam again.

Anyway, after making sure that there was no fore and aft twist in the bare hull, I fitted the breasthook and knees at the transom, followed by scarphed mahogany lengths for the outwale and the rubber spaced one plank below it. The outwale is OK to fit as it's easy to clamp but the rubber below it had a lot of twist along its length and needed to be screwed from inside the hull. The steps in the knees and breasthook are to allow spacers between outwale and inwale - looks fancy!

The frame shown seems a long way foreward of the transom but this is to allow the outboard to swing up into the boat. For this reason this frame is reinforced by a 40 x 85 oak beam at the top edge to take the inboard 'outboard'. If you don't need the engine to swing up, then a simple small outboard well would do and this frame could be moved aft a bit.

The upper edge of the transom is framed with 12mm mahogany inside and out, with a lip on top - should give a bit of character when cleaned up, etc.

At the bow end, the second frame is fitted - with opening for an inspection hatch. It get more complicated here as I'm planning to fit the mast in a tabernacle just aft of this frame, so the top of the frame is reinforced by a cross beam and the kingplank is more substantial than on the plans. The foredeck is to be extended back to Frame B position but I'm omitting this frame - leaving it open here - with the aft edge of the foredeck and kingplank supported by a laminated cross beam. The idea is to drop a vertical support from the centre of this beam to brace the foreward end of the centreboard case.

The oak samson post looks rather splendid but is not glued in position yet.

I've raised the foredeck to just 100mm below the gunnels and have introduced a camber - 'cos I think it looks nice! The refs. by John Leather and Peter Cook spell out the necessary details for this; or try: http://www.joliebrisemodels.co.uk/tenth/calculator.html

All other framing is omitted and replaced where needed by ribs - I think - maybe. There's an awful lot of time, at this stage, spent walking round the hull brooding . . . .

Turning the Hull

Purely to offer some protection to the hull while work continues, a coat or two of undercoat seemed advisable. I used Hempel's two part epoxy which certainly gave a very tough finish but, working with about a litre for each coat, I found that the pot life (in theory between 2 - 6 hrs depending on temperature) wasn't quite long enough. The mix started to drag a bit towards the end so that the finish at the end wasn't as good as at the start; need to work with 1/2 litre mixes in future.

The hull plus mould weighed about 120kg and since there wasn't room to lift the hull cleanly off the mould, I had to turn the whole thing onto its side, push it up against one wall and then let it down the right way up. (Thanks for the help John and Graham).

I had designed the mould with removable sections in the frames so that it should lift cleanly away from the hull - Ha! - in my dreams. Once the removable sections had been taken out, the mould was clearly free of the hull (thanks to all the sellotape used) but lifting it free was a bit like pushing a very fat drunkard up a spiral staircase; I gave up! In the end I had to resort to cutting the mould into three sections before the hull was at long last revealed. (Thanks to Sarah and Peter for help with the fat drunkard). At this stage the bare hull weighs 72kg.

Even without ribs or frames the bare hull is pretty solid - probably due to the rigidity of 9mm marine ply - but care will have to be taken that no slight twist from bow to stern creeps in. The order of work now is firstly to trim the upper edge of the sheer strake (with the aid of temporary pins as shown), then fit the breast hook and knees, then the outer gunnel and rubbing strip.

Glad to have finished the planking - the rest looks pretty straight forward - except for the outboard well which I reckon will be a real problem.

Finishing the hull - August 2010

With the planking complete and the outer stem in place, it remained to fit the skegs and cut the centreboard slot. I extended the stem back to the transom using 25 x 20mm oak, leaving a 25mm gap for the slot - this offered a reasonable base for a router so that the slot cutting posed no particular problem (long cutter needed though - 12 x 60mm). The hull is reassuringly sturdy at this stage, so that I can clamber about on top quite safely. Sitting astride the hull and cutting the centreboard slot was a bit like inseminating a small whale! - I imagine (not that I imagine this sort of thing much!- well, not at all actually . . . .)
The rubbing strips on either side are likewise of oak.

The skegs worried me a bit though; the positioning seems at first to be close to the centre line but if moved further apart they would need to be proportionately deeper. From the plans, the skegs already measure about 220mm at their deepest point, and at only 18mm thick, this seemed to me awfully vulnerable to sideways knocks, etc. The original cobles were recovered by dragging the boat, stern first, up the beaches, so that the skegs would be exposed to considerable wear, loads and possible twisting motions. On hard standing, the boats would have a 3 point support from the two skegs and the deep forefoot, leaving the centreboard area clear of the ground. My eventual compromise was to make them 30mm at the base tapering to 18mm, where they were capped with oak strips; I also reduced their depth and flattened the profile so that, on a hard surface, the foreward support would be just ahead of the centreboard slot. The oak strips running up the transom simply add further strengthening, similar to one or two of the cobles I'd seen on my Northumbrian visit. Later on I'll run a through bolt into a floor bearer for each skeg (I feel a bit like one of those early Victorian engineers, who over-engineered everything - just to be on the safe side!). Also at a later stage, I'll attach some keel banding but it's horribly expensive and I just can't bear to buy it just now.


With the skegs in place, the hull has a decidedly fish like appearance.

It remains to give the whole hull a protective coat of resin before the 'interesting' task of turning it over. I'm using clear epoxy for the strake at the sheerline and several layers of Hempel's (Blakes as was) epoxy undercoat for the rest.

The mahogany gunnels and rubbing strips, I've decided to fit after turning the hull. I'm interested to see the weight of the hull once the mould is removed.

Wasps show how it's done! - July 2010

My comment in June that insects are attracted to routers seems to be borne out by the appearance of a wasp nest in the shed where I use an overhead router. I find these things amazing; the colours are quite striking and the result is surprisingly strong. Perhaps appropriately, the wasps seem to favour a clinker method of construction and I'm watching with interest to see how their work proceeds.

The coble hull now has all its strakes and I'm hoping to have it ready to turn over within the next month. As can be seen, the strakes were cut easily from just 6 sheets of ply. 

The plans suggest laminating the outer stem in situ but I chose to build mine up from sections of oak, 28 x 45mm instead of the 20 x 25mm on the plans. This seems more in keeping with the sturdiness of the hull and allowed me to deepen the forefoot much as the cobles I've seen in Northumbria. 

Fixing will be with 6mm s/s studding once the mould is removed.

I'll also use oak on either side of the centreboard slot, then down the centre line to the transom.

However, first the skegs have to be fitted and I have a slight problem with these. The plan details skegs 18 x 220mm at the deepest point and, to my mind, these won't survive a sideways swipe when grounding, beaching, etc. I'm thinking 30mm at the base with through bolts - but we'll see . . . .

In Search of Inspiration - July 2010

The Scottish Traditional Boat Festival was held at the end of June and I went up to have a look - wanting to get some ideas for interior layout, rigging, etc. but leaving with other, unexpected impressions. The number of trad. wooden boats seemed to be down a bit compared with 4 years ago when I last went but some of the boats were familiar. The Reaper and her sister ship the Swan were looking as magnificent as ever and there was the inevitable glass fibre Drascombe lugger and longboat.
The St. Ayles skiff - an Iain Oughtred design with kits from Jordan Boats - http://scottishcoastalrowing.org - was new to me though and quite appealing. Among the others, there were some very nicely made craft but I was struck by how some had the unmistakable appearance of a 'kit boat' - not sure why - I think the varnished plywood construction was simply too evident. This wasn't true of the St. Ayles skiff, however.

Marine ply is a great material to work with and is very serviceable (as it should be for the price!) but I think many builders like to leave it exposed just to show that it's a wooden boat - doesn't really work for me though - perhaps reminds me of the popularity of plywood furniture in the 50's. So, it'll be a paint job for me I think - nice black hull and a bit of oiled mahogany perhaps - we'll see.

Planking the hull - June 2010

On reflection, using a polytunnel as a workshop may not have been my brightest idea. The temperature inside yesterday was 43C - too hot for me and certainly too hot for working with epoxy. West System epoxy seems best around 20 - 25C - I don't use it at temps above 30C - while that sold by Fyne Boats has a longer pot life, hardens more slowly and is better kept at around 25C. The Fyne Boats epoxy is more viscous until the 50% addition of catalyst and is good for wetting out large areas, coating, etc. I tend to swap from one to the other depending on the size of the job and the temperature. By volume, the Fyne Boats product is better value for money although East Coat Fibreglass offers good prices for the West System stuff. I try to keep costs down by measuring out the amounts I need for each job by using a digital balance instead of measuring by volume using the pumps available; a lot of jobs are quite small and may only require, say, 4 or 5 gms, and pumps are useless for this. Also, avoid buying acetone (for clean ups) at chandlery prices; search out your local industrial chemist and buy it in quart bottles at a quarter the price.

The planking starts with scarphing together the full size sheets of 9mm marine ply - space and good trestles needed! I scarphed them 2 at a time using a router with and extended base plate - as shown - where the top a bottom pieces are simply for guidance. It's not a particularly quick method but it's precise and doesn't demand the sort a stable base needed for planing. Use a new router bit (say 20mm) and think about the direction of cut when approaching the feather edge (or it'll tear). While scarphing I screw the boards together and for gluing full sheets, I fasten them together with five 5mm bolts either side of the scarph, going right through both sheets and 12mm backing pads top and bottom (don't forget the polythene separating sheets!). The holes left are easily filled if they coincide with the positions of any of the strakes.

Note: If you’re using a router outdoors, don’t be surprised if you become popular with the local insect population. It seems that the router whine has harmonics which serve as a super mating signal – called a super releaser – and it’s the actual cutter the wasps and bees home in on (not you) but I’ve not seen any get caught by the blades yet.

The patterns for the strakes are made using cheap ply (I use 6mm - any lighter proves too wobbly at 15ft long!). I work with lengths of about 1 - 1.5m perhaps 50 wider than the strake and tend to start at the mid sections. Making sure to hold it flat along the mould (clamps, screws, - whatever - see pic.) I trace along the lower ribband line, then remove it and mark the strake width at say, 150mm intervals to get the upper line. Clamp to the mould again and repeat the process on either side and connect the shaped pieces by clamping and gluing pads of scrap ply in situ on the mould.
If you take care with the pattern, you can transfer the shape to the marine ply and cut it on the line so that not much further shaping is required. However, with longer and narrower strakes, there's a fair bit of play and I prefer to cut with, say, 5mm allowance all round.The trick is to get as many strakes from your 16 x 4 ft sheet as possible – I’ll detail this later. After ensuring the garboard is a good fit on the mould, I glue and fasten it with clamps and silicon bronze ringed nails fore and aft and wipe off any excess epoxy both outside and inside where you can reach. I just use my fingers for this. I ensure that the strakes won’t stick to the mould at any point by laying ordinary sellotape along the ribbands and on the exposed edges of the frames (epoxy sticks to masking tape).

For the second and subsequent strakes, I cut a gain fore and aft using the modified rebate plane - as shown – so that the strakes lie flush. Not everyone bothers with this at the transom but I think it looks neater. I then use a similarly modified plane to cut the lands so that the strakes are flush where they overlap. When testing for fit and for final gluing, use the same clamping method as for making the patterns (if the mid section isn't clamped flat against the mould, the ends won't line up; if the ends are forced into position, the mid section will lift away from the mould); this allows you to gently knock the strake up or down to adjust positioning. The final location is aided by making one or two pencil marks and the use of a number of clamped tabs on which the strake can rest for final clamping and fastening. For temporary fastenings along the land, while the epoxy is hardening, I like Iain Oughtred’s method of self tapping screws (3.5 x 16mm for this boat) every 100 – 150mm – just remember to loosened them off half a turn after a few hours or they may snap when you finally try to remove them! Iain Oughtred suggests not allowing the heads of these screws to mark the strakes but I screw them down hard; the indentation left by the head is easily filled and when sanded down looks just like the head of a rivet – especially if you use a darker filler. Whilst the epoxy is still tacky, I run a fillet along the overlap of the strakes. For both fillets and bonding, I use an approx. 50:50 mix (by volume) of microfibres and colloidal silica - the amount added to the resin just depends on how thick you need it - I tend towards 12% by weight for bonding to about 16-20% for fillets.

Note: When sanding the marine ply, the Okoume outer layers may cause skin irritation - especially in delicate skin areas. Moral: wash your hands before going for a pee! Same goes when sanding resin, teak, rosewood - even beech can cause a reaction.

And that’s it really – a boat is appearing. At this point I’m on the 7th strake and am beginning to wonder how to turn the whole damn thing over. I think I may need friends. Hmm!

Delays - May 2010

Well – of course – there would be delays wouldn’t there!

For the first few months of this year, the workshop/polytunnel was too cold to work in – below 5C anyway, which is the minimum temperature for using epoxy resins. Now – in May – the temps. vary between 7 and 25 which is OK, but now other jobs are claiming my time – the rear steps and the front fence have both collapsed and need replacing, and my van is complaining that I take it for granted. The real problem, however, is not these distractions – I could afterall just ignore them all – it’s that I’ve reached that inevitable stage in boat building when serious money has to be spent on materials, and this requires two types of decision.

Firstly, with limited resources, I have to decide that building this boat is actually important enough to me to warrant the expenditure; is it, in short, an idle whim, a bit of fun that could easily be put on the back burner until a later date, or does the building go deeper than that? – to do with who I am and what matters to me. With loads of cash and leisure or if building for a paying customer, this question happily doesn’t arise, but for those thousands who are obsessively driven to persue some equivalent project or enterprise, the question is always there - not easily answered and often ignored.

The second decision is far more practical, concerning the quantities and sources of materials. Specifically, the coble requires 9mm marine ply at around £70 per sheet (8 x 4ft) but, in order to minimise the number of sheets, I need either the profiles or offsets of the 9 strakes – not given on the plans. With the mould completed, however, it’s possible to use lengths of relatively cheap 6mm ply to take patterns for each strake which can then be arranged on two 8 x 4ft sheets of the 9mm marine ply scarphed together. As an alternative, you can create a table of offsets from each pattern and then use a CAD programme to shuffle around the profiles in order to fit the maximum number on each pair of scarphed sheets. Alex Jordan of Jordan boats suggests that 6 sheets should do the job. 

If we accept a minimum of 6 sheets for the strakes, then we find that Fyne Boats offers good discounts on 8+ sheets whilst Robbins Timber offers even better discounts on orders of 10+. Given that I need a half sheet of 18mm for the transom, this would result in costs ranging from about £650 – 830. OK. Gulp! This probably means hitching up the trailer and visiting Fyne Boats in the next week or so.

In the meantime, I must give some thought as to how best to scarph and glue six 8 x 4 sheets – so expect more pics.

An Excursion to Northumbria - March 2010

The few days I'd set aside for a trip to the Northumbrian Coast were forecast to enjoy decent weather - huh! No rain at least but a cutting wind that obliged me to keep moving along the cliff tops. Around Flamborough Head, the cliff scenery is spectacular and I walked from the lighthouse at the Head, some 5 miles north to Bempton Cliffs, constantly impressed by the ruggedness and height of the tortured limestone cliffs, with countless coves, caves, arches and an abundance of birdlife. But, of course, what had really prompted the trip was a search for the Northumbrian Coble.

To be honest, I didn't expect to find any - but there they were - an assortment of heavily constructed working boats, many still being used for crab and lobster fishing, as well as one or two also offering tourist trips. At this time of year, most were hauled out of the water and were being maintained in readiness for a new season. Many dated back to the 1930s, typically made of 22mm larch on oak ribs and keel, and were fitted with massive twin skegs complete with hauling rings for winding the vessels stern first out of the water. As can be seen, most sat on a simple pair of wheels. The reverse curvature of the keels was clearly visible although some had levelled this out with additional timber on the keel. I was told that curvature resulted in 'slack water' beneath the centre of the boat but opinion was divided as to the function this might serve. The most plausible view was that it evolved to cope with the need to launch from steep beaches into waves. Anyone who's tried this knows how readily the typical boat gets spun by the action of the waves to end up side on to the sea and heading for shore again - done it! - got the T-shirt - embarrassing! Possibly, with a deep forefoot and even deeper skegs set well to the stern, this twisting action is less likely; I'm not sure - someone out there will know.

Not surprisingly, none were sailing vessels, having been converted mostly with inboard engines but the smaller ones with outboards set into wells (the transom being typically too high and raked to easily accommodate an outboard). This required substantial alteration to the hulls, resulting in 'tunnels' - often clinker former - centrally located between the two skegs.
As can be seen, the inboard props. were often position well forward. This has led me to wonder whether to position my outboard well or tunnel centrally rather than offset as per plans - might be more pleasing visually without loss of structural integrity . . . . may phone Paul of S.F. about it. Nearly all boats had an extra plank roved above the gunnels at the bow.

Did any of these boats ever have centre boards? - with heavy, deep skegs serving as bilge keels, probably not, especially since a centre board case wouldn't be popular on a working boat. Must check on this . . . .

Interestingly, coble design seems to have varied from one site to another on this coast. Often I would ask about a particular detail, only to be told that I must be thinking of cobles from a few miles up or down the coast . . . . 'we don't do them like that here . . . . However, tradition clearly isn't everything as repairs made generous use of Sikaflex.

In all, a lot of food for thought and a considerable admiration for the men who still work and maintain the distinctive vessels - I'd like to return to see one launched and recovered.

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.