BUILDING YOUR OWN WOODEN FOLKBOAT
FOLKBOAT FOLKBÅT FOLKEBÅD KANSANVENE FOLKEBOOT
This is the website of Ernst Enkvist describing how the nordic folkboat ALMA registered as FIN -372 was built and specifying materials and equipment. The purpose is to inform other boatbuilding amateurs and maybe presumptive customers.I am a retired naval architect aged 73 with a professional background of big ships, research, teaching and agriculture.I live in Ingå (Inkoo) some 50 km west of Helsingfors (Helsinki). Before the folkboat I occasionally built smaller wooden boats, regarding myself an amateur. For the Folkboat project I had to make visits to boatbuilding schools and other studies.
The Nordic Folkboat is a well known cruiser - racer sailing yacht class designed in 1941 as a common nordic committee work. To be registered the construction has to be in accordance with class rules and drawings and supervised by a measurer. Originally the boat had to be of wood of some limited kinds of timber. Later - to prolong the lifecycle of the class - GRP became an approved option, nothing for nostalgics of course. The original clinker construction is a 1000 year old nordic tradition. The class became very popular as a dry, safe,underrigged and easyhandled boat so many mutants were introduced, mainly to improve the accomodation, which is spartan. ALMA is a true Folkboat.
The material cost was 15000 e (excl. the outboard motor) and I used 2500 hours including the molding frames. A professional boatbuilder could have done it in half that time.I used a 10 by 14 m repair shop for agricultural machines and a 6 by 8 m woodshop. A 40 cm planer was used nearly daily, all other machines were hand held. The shops are heated and during cold winter days the relative humidity became very low, which is fine for epoxy glue but tends to make wood shrink and crack.All timber is domestic. Oak is used for the centerline hardwood, floors, knees, coamings and hatches. The shell planking is of slowly grown fir with a high proportion of red core and naturally curved growth. Frames are ash steamed in situ. Deck planking and mast are of spruce.Normal timberyards do not know boatbuilding timber. There are small enterprises taking care of that market sector. I got the planking fir and some stright oak for the keel plank from such a place and obtained a whole oak in round pieces which i sliced to curved planks for floors etc. using a motor saw rig. Thick pieces of oak need months to dry enough in a boiler room. The T&G spruce deck planks were custom made by a small timberyard.
Class drawings and rules were ordered from the national Yachting Association. Among these there is an 1:1 lofting section drawing (copied on paper shrinking unequally in different directions).The molding frames were made by laminating 3 layers of surplus boatbuilding planks and approved by the measurer. The boat was built during 3 winters. The first winter was used for molding frames, keel preparations, centerline hardwood pieces, transom, and fixing these by means of battens to the ceiling in a geometrically correct manner stiffly enough but using a minimum of battens because free access is needed during planking. The hull geometry depends on the location of all members at this stage and that has to be checked by the measurer.
Drilling and threading keel bolt holes in the raw cast iron keel.
Drilling a keel plank hole using a guide.
Aligning the keel plank drill guide according to a keel bolt in place.
The molding frames after use waiting for somebody to borrow them.
A small router vas employed to mill the groove for the planking in stems and keel plank. The planking work is directly proportional to the number of planks and the rules prescribe a minimum of 16 strakes each side. For an amateur it is hard to make a plank in less than two days. Before starting I recommend to study the distribution of planks on an existing boat. The transition from the vertical area to the underside of the transom is a challenge. Some steaming is needed in the after end of a few planks, to be able to twist them without cracking.
The routine of moulding a plank is the same as in all klinker work. A moulding plank is pressed in place and the edge positions marked from the previous plank and marks on each molding frame. Then the new plank is sawn with ample working margin and tested in place before final planing ,edge chamfer, rounding and finishing.The plank on the other side should be a mirror copy of the first one.Boatbuilders may invent gauges for the chamfer angle. Before final riveting of copper nails some cotton strings are tacked to the middle of the nail row. In my opinion polyurethane mastic may be used only in the ends and against the keel plank. Planks must not be glued to each other, it is essential that some movement is possible in the joints, the copper nails normally become slightly s-shaped. The positions of nails must be precisely marked, which may take an hour for a strake. Irregularly positioned rivet heads spoil the impression of your work. The four lowest planks are not scarfed, the next four are butt scarfed with a short scarf piece inside between frames and the 8 uppermost planks are from naturally curved timber without scarfs.
With some planks ready the floors were fitted in place .Moulding was made using hardboard. The floors must fit both planking and keel bolt, some creativity was needed to run in a method for that. The deep aft floors are in two parts , the lower vertically to prevent excessive crushing at the bolt nut and the wing piece with naturally grown curvature, a T&G joint between them.Completing one floor took at least a couple of days. The floors were fixed with screws to planking trough the single plank, not at the nail row. Thus the seam between planks remained flexible to prevent cracking. The vikings who built the Roskilde ships knew the importance of this principle.The ash timber for the frames must not be allowed to dry after sawing the log, which has been stored outdoors. If it dries it will never bend to the small radiuses of curvature needed in a Folkboat. The frames were sawn and planed to final dimensions with a shrinking margin. A helpful teacher and two boys from a school of boatbuilding came to do the framing which took one day. Temporary fixing was by nails hit trough predrilled holes in planking without drilling in frames. The steamed frames were soft enough not to be cracked by the nails. Very few frames were broken so there was material left to use for steamed coachroof beams. Afterwards it took a couple of weeks to do the final riveting properly. The second winter was ended and now a kind of hull existed causing some satisfaction to the builder.
A simple plywood drum and a wood fired boiler served the frame steaming successfully.
Next fall ,after finishing plank ends and sheer line the hull was soaked with a preservation liquid named ASPERGOL and then ten times with cold pressed linseed oil richly splashing once a day. The shelf was epoxy laminated from double planks without steaming. Deck beams were lofted parabolic and also laminated from two pieces sawn to camber. A method of fixing the beam ends in the shelf without weakening any of these too much was developed, such details are not shown on the class drawings. The hull construction with steamed frames only is clean in principle, but before fixing deck beams it is floppy and has to be forced to the correct bredth. The carlins had to be steamed and prebent on a mockup before fixing them onboard. It took some time to find two symmetric oak planks for the coamings of sufficient length and width.Knees are of curvedly grown oak, a dozen of them is needed. The coachroof beams had been steamed and prebent on a mockup with a constant camber profile. A couple of days was needed to align them nicely. The roof has a double curvature, but it was still possible to use stright even - width planks to cover it.
Deck planking started after impregnating beams,coamings etc. The spruce T&G planks were 15 by 85 mm and had been preimpregnated. Underdeck oil splashing is avoided by aged persons. Each plank was screwed with two countersunk stainless screws to each deck beam. 20 metres of 1.7m wide cotton canvas was bought for 270 €. Its weight was 400g/m2. A sailmaker sew two lengths of it together, the seam along the centerline of the deck.The corners and cockpit hole were cut off and used to cover the bunk cushions - nice looking but sensitive to dirt. After fixing the canvas to the coamings with temporary battens it was stretched manually and copper nailed along the outside of the sheer plank. Next it was wetted to shrink and while still wet boiled linseed oil was brushed on. Later it was painted four times with oil paint intended for painting the outside of wooden houses (TEHO). If painted too many times it becames slippery. All this was done according to published instructions dealing with the maintenance of folkboats. The intention was to keep the canvas free from the deck,not fixed to it by paints. To begin with it looked fine and smooth but the work was done in very dry conditions and after launching when the deck planking expanded ridges arouse along the T&G joints between planks. The canvas had still partly stuck to the deck.It is tight and nice to walk on but does not look perfectly smooth.The toe rail and rubbing strakes were made of oak starting from raw planks using a hand held planer. These battens were preimpregnated and fixed to the deck and sheer plank using screws and PU-mastic, a tedious work which is important for the appearance of the boat.
In the spring of 2005 the lack of smoothness of the deck canvas became unbearable to the ambitious builder and the deck and cabin roof were recanvassed using an expensive 700 g/m2 canvas which was fixed to the deck by a thick layer of oil paint.Needless to say such an operation includes removing and refixing of all battens and fittings on the deck. The deck planking was sanded smooth and reimpregnated. So far the result looks good. One experience was that the paint used as a deck laying compound must be really thick. Further it was concluded that if a deck canvas is intended not to be fixed to the deck, then there must be some insulating layer between the deck and the canvas, just wetting the canvas before painting is not enough.
Making the mast had started in the autumn when a dozen 2 by 6 in ordinary spruce planks were selected from a large amount at a timberyard. The planks were pressed together with air between them and allowed to dry. Still some of them twisted .After planing to 30mm pairs were epoxylaminated and then scarfed after planing 1:10 oblique glue surfaces. After contour sawing and luff and cable grooves routing the halves were glued together and then the final rounding by planing commenced. A considerable proportion of the original timber becames chips.The mast thicknesses in the drawing are minimum and the maximum thicknesses are stipulated in the rules. For the boom there are considerable differences between these which enabled making a “torpedo boom” reinforced where needed for the kickstrap.
The third winter had elapsed and in may 2003 the cockpit interior, floorboards, bunks, hatches ,varnish and paint and all fitting installations were still missing. Following some final rush and tear ALMA was launched july 7 2003 much to the relief of the builder. The sails are just a mainsail and a jib in sturdy cruising grade made by Meripurje sailmakers. There is a 26 Ah dry sealed lead battery and masthead navigation lights. Compulsory safety equipment is provided. The outboard is a 4hp 4-stroke with clutch and reverse on a console which can be raised and lowered (not the same as shown on pictures).There are storage boxes under the bunks but no pantry. A space for possible future installation of a pantry and wardrobe is arranged by making the bunk ends with cushions removable.
The tiller man is seated at a higher level for sight over passengers
and coachroof.
Most fittings are from Folkebådscentralen.
Cabin interior is spartan but there are four bunks.
ALMA was successfully tested in the summer 2003 and has since that been sailed by us – my wife and me and our guests on day cruises. Everything works and once we tacked in 11 m/s wind force (13 in gusts) without a reef and she heeled to the rubbing rail. A Folkboat is easy and safe to sail, but we are convinced we prefer less sporty occupations at our age and have been looking for some wooden boat enthusiast to buy her. Now we are happy to announce that mr Paul Forrest of Dublin, Ireland has inspected and purchased ALMA for delivery in the spring of 2006.
Ernst Enkvist
26.3.2006