Welding the hull up - outside

Welding the hull is a big job and it can makes or break a steel boat. I followed the recommended books of G.Klingel and T.Colvin. Correspondence with Nick Skeates and the TAFE night welding course also were invaluable. Prior to full hull seam weld up, the entire hull is held together by tack welds at about 6" spacings. Full weld up begins on the outside. Once outside welding is done then the hull is rolled over for internal welding.

  

Good preparation of the weld seam is important. Beveling the plate edges and leaving a 1mm gap between plates/chine bars allows for good weld penetration and also stronger weld with no hairline cracking due to shrinkage (could occur if the plates are hard-pressed together)

 

3.2mm weld rod stubs were used as spacers between frames and chine bars or stringers (These were fitted at the framing stage befoe hull plating). They were knocked out as seam welding progressed past them and the hull began shrinking. In retrospet 5mm spacers would have been better, especially near frames 1 and 2 in the bow, where hull shrinkage was greater.

I used short weld runs around 2-4" long. The short welds are needed to prevent any unsightly distortion (buckling) of the plates occuring. After doing a short weld i moved to another location to allow the first weld time to cool down. Both sides of the hull are also welded symetrically to prevent the hull pulling out of shape. Full hull welding has the effect of shrinking the hulls size by about 5-10mm.

A welding pattern needs to be followed. This is to balance out all the shrinkage forces evenly. I began near the center of the hull in the garboards (keel meets hull joins) and worked outwards towards the ends of the hull. After several meters of weld were in the garboards, i started on the lower chines..when several meters were on the lower chines , i started on the upper chines.

When a longitudinal (sub-horrizontal) weld seam reached a tranverse (up and down) plate join then i started welding down the plate join. Small plate bolts and washers were knocked out before the weld seam reached them, otherwise they would be clamped in by hull shrinkage.

 

After a weld was done the slag is chipped off with a welders hammer and wirebrushed.  Then the angle grinder was used to prepare the end of the first welds to meet the next weld. If a pinhole was noticed, it was ground out and rewelded.

Power wire brush fitted to 4" angle grinder make weld cleaning fast and easier. A face sheild is needed to protect eyes from any wires that may fly off.

The soft chines of the wylo2 are a bit unusual. They are 2" flat bar laid flat which forms the hull skin and makes a gentler corner which helps give the apperance of being a rolled plate hull instead of a hard chine hull. But the problem i noticed during weld up is this is easier to distort than usual chine methods of a solid round rod or on-edge chine bar. So i tack welded  tempoary 1" flat bars on edge, on the outside, in the center of each 2" chine bar to prevent chine distortion (photo above).

Welding seams. The rubrail was added prior to weld up. It is a 40x20mm steel channel set about 6" below  (above in this pic) the gunwale. It acts as a very strong double external hull stringer. As designed, it is also more aesthetic, reducing any slab-sided effect of the topside plates.

Some builders make the rubrail coincident with the gunwale (Klingel-Colvin method) fitting a 40-50mm preferably galvanised pipe instead of the designs 1" flat bar gunwale. This then requires an extra internal 1" flat bar stringer to be fitted to maintain hull stiffness around where the design rubrail would have been. A gunwale rubrail takes all the bumps well but it does make the hull appear to be a bit stockier aesthetically than the wylo2 design rubrail method.

I did  the hulls chines and garboards with a traditional 180 amp stick welder with 3.2mm rods and about 110-130 amps set. It takes 15 amp AC input. The 3mm hull plate joins needed 2.5mm rods with ~90 amps set. It may be better to "back-step" these joins, weld upwards starting  2" down from the previous weld.

Arond this stage i bought a 130 amp MIG (metal inert gas) welder with 10 amp AC input for thin 3mm hull plates. It  produced far less distortion than the better-penetrating 180 amp stick welder. The MIG was set at around 90-110 amps and a continuous wire feed from a spool activated by a trigger is easier to weld too. The MIG can be run gasless with flux coated wire or with an Nitrogen bottle attached by regulator and hose. The inert nitrogen gas of the MIG makes a gas sheild over the molten weld keeping out oxygen and making for a good weld without slag etc. My MIG prefered downhand welding (weld gun above weld). On overhead welds the MIGs gas sheild cowl got quickly filled up with weld spatter, never a problem with the arc welder.

The MIG has a big box, almost the same size as the arc welder, but with only 8 feet of flexible cable to the weld gun (no "traveller" as in expensive MIG welders). so moving the MIG with nitrogen bottle around was more difficult than the simpler 180amp arc welder with its long 10m cable. For me the MIGs welding advantages for 3mm plate outweighed its mobility disadvantages. (It wasn't powerfull enough for the thicker plates or chines so both welders were good for their particular uses)

Keel base plate

The keel base plate is made from a solid piece of 12mm thick steel about 6 meters long and around 40cm wide, it weighed hundreds of kilos so was moved with chain block and rollers etc.

The photos show keel base plate preparation work. Making sure the bottom of the keel is leveled off for the plate to fit on top, so the welding gap is correct all the way around.

 Moved up to large oxy-acetylene tanks for cutting steel hull plates (small ok in the frame building stage). The 12mm base plate cutting needed large cutting tips and alot of gas. It may be possible to provide a full-size template to a steel fabrication shop and they could plasma cut the keel base to shape.

This photo shows the keel profile shape. It is a NACA designed foil section. A 4" hollow pipe on a raked back angle forms a nice oval leading edge shape horrizontally. The keel has 6 compartments with 5mm plate bulkheads. These bulkheads extend to floor level inside the hull making the keel very well braced for extreme sideways forces. Moving front to rear the first 3 compartments house the ballast. The 4th and 5th are water tanks and i made the final thin compartment a sealed void (others use it as a tank, its a stove-kerosene tank in Nicks plans). The first 2 ballast bulheads have 45 degree cutouts on the corners, it should elliminate the chance of metal fatigue cracking where 2.2 tons of ballast gets thrown around by the sea. The 2 separate water tanks (25 gallons and 45 gallons) are fully sealed at the corners.

Sorry no photos of the plate making or raising. But i used a standard masonite template as the other plates were done. The keel base plate was about 10mm wider than the keel sides, sits ontop with  T joins to the keel sides. This join is probably strongest and is per design. 

(Also it allows the optional keel winglets could be attached..that a story in itself - to cut a long story short, i started building the 5" winglets, got the lower side in place on both sides but after awhile realized it was all too much time and work, and decided to "keep it simple" so oxy-cut them off and reground the ragged base plate edge smooth again. If you want to win the Ammerica's cup or something like that then build the winglets, i don't think they'll be necessary on the 4'3" draft keel version, (useful on the 3'9" draft keel version though, eg wylo35 Mahina ))

So the base plate was cut out and edges ground with the 9" grinder. (sorry cant remember peening it, if i did it would need a sledge hammer).  A strong angle steel was welded to one side of the hull and braced to take the 1/2 ton chain block, then it was raised into position and tack welded on. Shade cloths went back up. Final edge measuring, scribing and grinding followed.

Hull plating (3mm)

3mm thick,  mild steel plates were used for the hull from the lower chine to gunwales. The stock sheets were 6m long. They are not much heavier than the small 8x4 5mm sheets.

 2" diameter pipe rollers on angle iron rails was the method used to move the sheets across flat but lumpy ground into the boatyard from where the truck dropped them off. It was best with 2 guys hauling them along with a rope, (but one had to take the pic). It took an hour or so to move them about 15m. Thanks to Kim for the hard work put in that day. 

Templated Hull sheets were 6m long if possible which made only 4 vertical joins to worry about in the hull length. The 3mm was put on the topsides of the hull and between the chines. The vertical joins were also staggered to give greater strength.

Although larger, the 3mm plates were easier to bend and fit than the 5mm plates. A bit of gardening was also going on provide a foliage screen to keep the council happy.  The above photo shows a tyre pond, it was soon demolished due to mosquitos and in any case a boat yard should have vast ammounts of flat clear access space around it if possible (for work, vehicles, big trucks and even cranes etc).

The 3mm plates are faired up and tacked on. Prep work begins on the keel base.

It was well worth getting the largest sized 3mm sheets available (6 x 1.5m = 20ft x 5ft). Any handling difficulties were far outweighed by smooth and fair plating.

Hull Plating (5mm)

 The plating began with the 5mm bottom plates. The first plate was at the aft quarter . A half ton chain block was hung from some angle steel set around the keel line. A pair of well tightened 4" G-clamps in the middle of the plate substituted for a plate dog. Just made sure not to stand anywhere below it while raising.

 It's easier and faster to make a Masonite template for each plate. Masonite is a soft 6mm wood pulp sheet. Pieces of masonite were fitted to the hull frame, tek screwed together and clamped into position on the frames/chine bar. A pencil marked the outline of the sheet on the masonites painted side. Masonite is soft and it was easy to use a wood jigsaw and plane the edges to shape on the ground. The template was re-fitted to check, alter the outline, then replaned.

The template was then overlaid on an 8x4ft steel sheet and the outline scribed onto the steel. Oxy-acetylene gear was used to cut the steel sheet a few mm outside the scribe line. 9" and 5" diameter angle grinders then removed the few mm of steel to the scribed outline.

The oxy-acetylene cutting process causes some shrinkage distortion (curving) of the steel plate so the edges were peened flat. Peening involved placing a small anvil under the sheet edge then hitting the edge above the anvil with a small steel mallet. The anvil was moved and process repeated right around the edge of the plate. The edges of the plate, chine bars and adjoining plates on the hull were beveled to allow for better weld penetration later. Finally the plate laid flat on the ground ready for raising.



The third bottom plate is being raised amidships.

The plate fit exactly into the gap between lower chine, garboard and aft plate. C-clamps aligned the plate to chine and bolts with washers held adjoining plates into alignment. After everything looked fair and smooth. It was tack welded to the hull framework. A small 1mm gap was left at all joins. The templating pays off at this stage. Its far harder to move the heavy plate around than the lightweight template.

I followed the building methods and techniques recommended by the designer Nick Skeates and others of the era such as US boat-builder Gilbert Klingel and US Designer Thomas E Colvin (refer the books side bar). The building plans supplied by Nick come on 4 , A2 sized sheets, plus some building notes.

A 4" diameter pipe was fitted to form the leading edge of the keel.  The 40x10mm fore foot bar was faired into the hull.

The bottom plates were done first so that a solid surface is made to walk around on for work on the keel. It also allows access and keeps it drier below.

The keel side plates are fitted next. The aft plate has the propellor aperture cut out. Small steel steps were tack welded to the transom for easy access onto the hull.

 Note plate-plate joins have small bolts and washers, drilled through, to hold joins into alignment. Short flat bars help with hull fairing.

Framing up the hull

The frames were stood up, aligned and tacked onto the jigs angle steels. Its a great feeling to see the 3D shape of the hull for the first time. A string line down the centerline and the spirit level on centreline angle irons (plus plumb-bob) are good tools here. This stage is when you find out if your earlier lofting floor work was accurate or not.

Nicks building jig had angle irons going into cement footings. The hull must be held down onto a secure building jig to resist any plating-up and weld shrinkage forces during hull weld up later on. Initially i thought the heavy railway sleepers might do, but given the expanding clay soil i decided to play 100% safe and make 2 cement footings per sleeper as shown above. The vertical angle iron of the footing is welded to the jig frame and tek screwed into the sleeper. Mixed cement in the barrow. Station wagons shouldn't really be used for this, but it was an old beast with a rusty tailgate.

The transom is set up. This took a bit of bush-geometry and stake into the ground. The transom was pre-fabricated at the frames stage. After oxy-cutting, it wasn't edge peened (like all the other plates were to be) in order to have a natural compound curve left in it. In retrospect it should have been edge peened, to make the sheet flat. The sheet should curve in one dimension only, across the hull. The sheet should be flat to line up with the 2" flat bar end of the keel. (straight angle iron tacked on centreline). In summary I strongly suggest - peen the transom sheet flat before it goes up.

The 40x10 mm stem bar was aligned and tacked into place to form the bow shape. See photo below

Next the 2x 1/4 " flat bar chines were fitted and tacked welded on. I had saved 3.2mm weld rod leftovers for use as spacers between the chine bar and frames. This is done because later on during hull weld up, massive contraction sets in, so the spacers are knocked out as the compressive forces begin. If it were not done the frames would get hugely compressed and start buckling under the load. 

Another problem with flat chine bars is they dont bend too well edge-ways. To bend them like this run a weld bead on the side of bar edge you want the overall bend to go. Suddenly quench the hot weld with water and a curve will form.

 1" flat bar stringers fit into their slots, also with 3.2mm weld rod spacers. All longitudinal framing should have fair curves. If a stringer or chine is too far in,  a small spacer can be tacked on to hold it out to a fair curve.

As soon as the hull framework was strong enough, 4 shade cloths went up over a large bamboo ridge pole. Several angle irons tacked to the keel plates held the ridge pole up. Two more long bamboos held the outer edges.

The stringers and chines were pulled into the transom by tie wires.

The hull shape takes form. The cabin ends at frames 2 and  8 are a little over 20 ft  (6m) apart.

The 1" stringers are located where 3mm thick plates are to go. No stringers were needed to support the bottom plates, at 5mm thick the bottom plates are strong enough on their own. No bilge stringers means fewer potential internal rust traps in this area.