Continued - In the Spirit of the Humber Yawl

The larger examples of the Canoe-Yawl are very appealing, and I've fantasised about building and sailing a Rozinante for decades. However, age brings wisdom, and I have realised that even a small increase in the linear size of boats brings enormous differences in the practical utility. As an example, I would often look at the study plan for William Garden's Eel, (which is a very good example of the canoe-yawl type), and think that at 18' 6" x 6' she was a small boat.

Eel, designed by William Garden. Image scanned from Woodenboat Publications Thirty Wooden Boats

Well, one day a customer turned up at the workshop with a second-hand Eel on a trailer, and I discovered that she was far from small and was definitely not light when it came to pushing the trailer around!

Eel on arrival at the workshop

Eel on arrival at the workshop

Eel on arrival at the workshop

Eel went through a successful restoration process, but the owner never got to use her for the simple reason that she was too much boat for him to launch and retrieve without assistance.

A typical Humber Yawl in the late 1800's may have been around 14' x 4' 6", so about 75% of the overall dimensions of Eel. That doesn't sound like a huge difference, but when it comes to weight, volume, and cost the difference varies according to the cube of the linear change. Therefore, Eel is nearly two-and-a-half times (2.3 times) bigger than a typical Humber Yawl from the early days.

One of my favourite examples of the early Humber-Yawl was Ethel, designed by George Holmes, who was one of the original members of the Humber Yawl Club which I refered to in the previous post . I first saw this drawing in John Leather's book Sail and Oar back in the early eighties, and I found the little boat to be incredibly attractive and wholesome.

Ethel designed by George Holmes and built somewhere between 1888 and 1889. Her principal dimensions were 13ft x 4' 6" and with a total sail area of 106.5 sq.ft. (Sail and Oar by John Leather, Conway Maritime Press)

This is a sketch done by George Holmes, said to represent a cruise in which he participated, in Denmark 1896. These boats were transported by ships as deck cargo, or in the freight vans on trains - trailers being the modern equivalent, I guess. (Sail and Oar by John Leather, Conway Maritime Press)

Funnily enough, the size I decided upon fifteen years ago for my idea of the perfect beach-cruiser for solo and two-up sailing happens to be very close to the "average" size of these early Humber Yawls. My decision was a boat of around 15' LOA and 4' 6" BOA.

This is my Phoenix III design, which at 15' x 4' 6" (to the inside of the planking) is very close to early Humber Yawl dimensions. Also, other than having a transom stern, her character is similar, and she could easily be fitted with a yawl or ketch rig.

You might think that using a transom stern automatically disqualifies a boat from the canoe-yawl category, but I think that the type is determined by function and use rather than specific hullform. However, I am still drawn strongly towards the double-ended form, such as Ethel shown earlier. I'm working on a design for just such a hull, but lack of time has prevented me getting the hull modelling to a point where I am able to produce a hull which is as effective as my existing transom-sterned boats. I intend to continue working on the idea, though, and here is a sample.

Recently I've started on a new direction with my boatbuilding, and after I have completed my existing orders, I'm taking a break from professional building and will at last devote some time to maintaining and using my own boats. Not only that, but I've been indulging myself in the design of a new boat for my own use, with the intention that she be passed on to my sons when I'm too old to sail. I'm hoping that they will benefit in the same way that I have benefitted from the use of my own dad's boat.

Phoenix, designed and built by V.R. Lillistone. The rig shown is one of the many that I have tried on her since dad's passing, and my sons have also spent much enjoyable and educational time aboard her - right from when they were babies. 

Because I intend my next boat to last several generations, and to be used for more than just solo beach-cruising, I've decided to make her a bit larger than my "ideal" size. She will be 17' x 5' and will carry around 130 sq.ft of sail, depending on her rig (of which there will be several options - all fitting in a single set of partners and steps).

I haven't decided on the construction method yet, but the short list includes glued-lapstrake and glued strip-plank, with the latter being the likely choice. The design is in a very early stage at the moment, but the internal layout will most likely be very similar to that in my existing Perwinkle design.

Lines drawing of my intended boat for personal use. She is 17' x 5' to the inside of planking.

As with my other designs, I've tried to manipulate the distribution of area in several rigs so that the boat can be re-rigged without having to alter the location of the mainmast partner and mainmast step.

The Gaff-Cat rig with an optional jib set flying. This is an un-stayed rig, and the tiny jib's function is to smooth the flow of air past the mast. The boat will balance fine with or without the jib set. Total sail area is 132 sq.ft, or 118 sq.ft using the mainsail only.

 

Here she is with an un-stayed ketch rig, utilising the very effective sprit mainsail and flying jib from Phoenix III and First Mate. The idea is that she will balance with just the mainsail set (reefed or un-reefed), or under jib and mizzen alone. Hopefully she would self-steer under jib and mizzen.

I understand that there will be many people who disagree with my contention that very small boats are the optimum for coastal cruising, but for my own use, I am totally convinced, and I think the original members of the Humber Yawl Club got it right!

In the Spirit of a Humber Yawl

In 1883, a club was formed on the River Humber, which is on the mid north-east coast of England. The Humber Yawl Club is still operating to the best of my knowledge, and I intend to do more reading about the club's history. The reasons that I am interested in this club is because of two of its most famous members - George Holmes and Albert Strange - and because of the irrisistable tugs which the boats originally used there have on my emotions.

Cherub II designed by the artist Albert Strange. Image courtesy of The Albert Strange Association and the book, Sail and Oar by John Leather (Conway Maritime Press)
LOA 20ft 2in
LWL 17ft 7in
Beam 5ft 10in
Draft 1ft 9in/3ft 9in
Disp. 2464lbs
Sail Area 249 sq.ft

Cherub II designed by Albert Strange. Image courtesy of The Albert Strange Association and the book, Sail and Oar by John Leather (Conway Maritime Press)

Cherub II, shown in the above images, was said to be Albert Strange's favourite design, which is significant given that he was a prolific designer. My first glimpse of the design came in 1983 when I was 29 years old. I had been sailing since the age of five, and for the most part my sailing had been solo and two-up dinghy cruising. I was fortunate to have had a grounding in racing, and it pains me to see people these days who have nice boats, but don't know how to sail them properly. Racing is an unforgiving way of discovering one's faults!

Because of my dinghy cruising background, I was immediately taken by the simplicity and snugness of the canoe-yawl concept and I was hooked. The initial exposure to Cherub II came because my good friend and dinghy cruising accomplice, Ian Hamilton, showed me a copy of the beautiful little book, Sail and Oar by the John Leather. The subject matter in the book was right up my alley, but my favourite chapters were (and still are) the ones about Albert Strange and George Holmes.

The definition of a canoe-yawl is fairly loose, with some people saying that the craft simply have to be sharp at both ends, and be yawl-rigged. However, a number of canoe yawls are rigged as ketches and sloops rather than yawls, but the famous designer, L. Francis Herreshoff said that the term 'yawl' when applied to a canoe-yawl referred to the 'yawl boat' hullform rather than the rig. One of the most beautiful canoe-yawls ever designed was L. F. Herreshoff's Rozinante, which was rigged as a ketch.

Sail Plan of the original Rozinante as depicted in the book, The Compleat Cruiser by L. Francis Herreshoff (published by Sheridan)

Lines drawing of the original Rozinante as depicted in the book, The Compleat Cruiser by L. Francis Herreshoff (published by Sheridan)

Rozinante rigged as a yawl. This sail plan was drawn by the Americanboatbuilder and designer, Doug Hylan

 

...to be continued

 



A Comforting Story - Mostly True...

Eel designed by Bill Garden. We carried out significant retoration work on this boat, and she is seen here with master boatbuilder, Bill Flood at the helm.

The time was 2am, and the shallow water sweeping past Mike Rowe’s shins was transparent silver in the intense moonlight. For miles in every direction, he could see the exposed sand banks and the mangrove trees in almost full colour, such was the brightness of the moon. 

As he stood, amazed at the speed of the water flow now that the tide had turned, Mike saw dark flashes in the water as the predators commenced their next tidal duties. The predatory fish were smaller than a person’s foot, but they were only the advance guard – Mike knew well that as the water deepened, so would the size of the hunters increase. Crocodiles concerned him a bit, so he had remained well clear of the fringing mangrove thickets and frequently glanced around him as he stood on the open flats. 

Mike and his friend Ian had motored into this estuary just after the top of the tide at 8pm of the previous night – had they waited longer, their path would have been blocked by the oyster rocks further out, which formed a barrier to this isolated place. Having located their target, the pair anchored the little cat-yawl using lines from both the bow and the stern. Positioned securely, they prepared their standard late-night drink and passed a few hours in contemplative discussion. 

Normally, their talk would have wandered far and wide over a range of subjects. But tonight they found that they were concentrating solely on the slim and purposeful rowing boat that tugged at the end of the painter running from where it was belayed to a cleat on the aft quarter of the cat-yawl.

Ration designed by William Atkin

For Mike Rowe, the construction of this rowing boat had been a highlight. He had been building full-time for six years when Ian had approached him with a serious commission. What made the proposal so satisfying was that it combined the benefits of building a type of boat he believed in strongly - for a life-long friend.

The plans for the rowing boat came from the board of the late William Atkin. Mike had grown up in a house full of boat books, and the ones which delighted him most were the old “Motor Boating’s Ideal Series”. The series (which dated back to the early part of the twentieth centuary) contained the work of many designers and writers, but by far the majority of the books Mike saw were filled with the work of William Atkin, and subsequently that of his son, John.

William Atkin came across as being a gentle person, and his written word carried a mixture of salty wholesomeness that Mike had not seen equalled. In many ways, Mike preferred the design work of William’s son John – but when it came to evocative writing, nothing gave him such a feeling of security and fulfilment as the words of William Atkin. (If you haven’t done so already, get hold of a copy of, “Of Yachts and Men” by William Atkin – a wonderful book for both dreamers and realists).

Mike had built the boat in what he believed was the quickest and best way – by carrying out a proper lofting, laying down the lines full-size on sheets of white-painted plywood nailed to the floor, and then constructing the boat over a strongback and station mould.

Ration designed by William Atkin

 

The rowing boat he built for Ian had been a straightforward piece of building, without any gimmicks. A solid sheet of 12mm plywood (scarphed-up from standard length sheets on the bench) made up the bottom. The topside planking went on in three strakes per side – 6mm plywood glued up in clinker (or lapstrake) fashion.  Gunwales were laminated on while the boat was still on the mould, and then she was turned over for installation of frames, thwarts, breasthook, quarter-knees and inwales. A thoroughly wholesome boat.

For those who have never tried rowing in a suitably shaped craft, the process can be a revelation. Instead of rowing being the frustrating chore it is when using a misshapen abomination such as a planing tinnie or an inflatable, rowing a properly designed rowboat is like a magic carpet ride. Attention must be paid to such things as the placement and design of the oarlocks, position of the seats in relation to the oarlocks, and positioning of foot braces. But get those simple things correct, in a properly designed boat, and you are in for some real pleasure.

As the six-metre tide raced into the inlet, Mike made his way back to where his cat-yawl, now starting to lift and bump on the sandy bottom, lay moored. Ian was already awake and was working at lashing the treasure to an arrangement of ropes which were in turn attached to the Atkin rowing boat. The “treasure” was, in fact, a lump of cast iron which had once graced the decks of a sugar barge as a set of bollards. Many decades had passed since the old barge had been abandoned to rot in this isolated creek. All that now remained were a few worm-eaten timers standing black in the moonlight; and the old set of bollards.

Six metre (twenty foot) tides work very effectively as a lifting device, and it wasn’t long before the rowing boat was floating mid-stream with the cast iron bollards hanging below her, unseen in the tropical water. The trip home was made under power, with the treasure ship towing nicely behind the mothership; an armada in modern times. A late breakfast was prepared afloat and, of course, the crew made sure that the treasure was handed over to the relevant authorities…

Simple are the delights of messing about in small boats. How better can one enjoy the pleasures of planning, building, using and maintaining, objects of practical art? The fact that the activities are cheap, health inducing, quiet, non-polluting and pleasurable to the senses, is a fantastic bonus. 

Answers to a couple of recent comments

Here is comment received regarding Fleet:-

How much does she weigh?
What I like about flint is that the center of balance is over the center thwart making her easy to carry and light enough for this senior citizen to car top.

Well, I can't tell you how much she weighs because we haven't weighed her yet, but the material thickness is the same as on Flint and the area of plywood is only 8.4% higher, indicating an 8.4% weight increase.  The Fleet shown in the pictures has a foredeck and inwales, but the standard Flint and Fleet have tank-tops on the foreward and aft buoyancy tanks, so it probably all evens out.

Based on just the plywood in the bare hull, the weight of Flint panels is 24kg(53lbs) and in Fleet the same is 26kg(57lbs). The centre-of-gravity of the hull panels (including transom without framing) is at 1.96metres forward of the aft perpendicular i.e. at the midships thwart near the aft edge.

The weight of any boat depends tremendously on the density of the materials used, and the attitude of the builder.

________________________________________________________________

In relation to my recent post on the virtues of the sprit rig with the jib set flying, Dennis Marshall writes: -

May I ask what the line is hanging from the peak of the sail?

Dennis is asking about the light line which can be seen in a number of photos, running down from the head of the sail at the peak end of the sprit

The light line is just visible in this photo

The line is a vang. I suggested that it be used in certain conditions when hard on the wind and when running free, to control the amount of twist in the sail, and (when running) to prevent the head of the sail from moving forward of the beam i.e. forward of a a line drawn at right angles to the centreline of the boat. If a sail moves forward of the beam, it is a sure invitation to a 'Death Roll'.

The light line is run from the head of the sail near the peak of the sprit down to a thumb-cleat on the weather quarter and then to a little fairlead on the rudder head and then along the tiller to a small V-jamb cleat within easy reach of the helmsperson. When tacking or jibing, the line is flicked off the thumb-cleat and quickly moved to the one on the new weather quarter.  It only requires a light tension on the line (vang) to haul the head of the sail in to reduce twist in the sail.

Spritsail with Jib Set Flying

When I posted about the Sailing Pilot Boat-inspired design that I have started for Geoff Leedham, I was reminded about how much I like the Spritsail rig with a jib set flying.

Bertil Andersson's drawing of Lotsbat Skum

Back in about 1998, I think, I was working over what I thought would be the optimum-sized boat for solo and two-up beach-cruising ( see post here). The whole process became an obsession, and one of the things that I worked over in minute detail was the choice of rig. Over many decades I had sailed my existing boat with a range of different rigs, and had gathered a worthwhile amount of general daysailing and cruising experience using un-conventional rigs.

After much head-scratching, I settled on the spritsail with a flying jib (i.e. a headsail not hanked onto a stay), having been influenced by the writing of a number of people, of whom Phil Bolger was the most influential.

Why the spritsail? Here are my reasons: -

• I wanted the shortest practical spars, and in particular, I want to be able to store the spars inside the boat. Several reputable authorities had written that the spritsail sets the maximum sail area on the minimum length mast;
• A jib or staysail would be nice when sailing to windward - particularly a flying jib on an un-stayed mast;
• The rigging needed to be very simple, and preferably easy to make and repair by hand using wood and line;
• It was important to me that the centre-of-areas in the sail-plan be as low as possible to reduce the heeling moment;
• The possibility of using the mainsail as a boomless sail as well as being usable with aboom was desirable. In really tough conditions, a boomless sail is a safety feature, as there is no boom to trip during a knockdown - you can alway ease a boomless sail but not so a boomed one;
• A spritsail can be brailed if properly set-up.

The above list made lots of sense to me, but the overwhelming advantage seemed to be that the spritsail is one of the very few rigs which can carry a jib without any shrouds or back-stays. Any headsail needs plenty of tension in the luff or else it will sag off to leeward, drastically damaging windward performance. Usually the rig with a headsail of any sort needs shrouds with plenty of drift, and/or backstays in order to keep the luff taught.  A friend of mine who sails a Bolger Folding Schooner finds that it is necessary to drop his jib when going to windward, because the boat goes faster without it! This is because there are no stays and the jib sags badly when on the wind.

In the case of the spritsail, the sprit is placed under considerable compression by the snotter at the lower end (the heel end of the sprit). This compression is required to hold the head of the mainsail up and out and to keep the head of the mainsail taut.

Here you can see how the sprit pushes the head of the mainsail upwards and outwards

The above photo illustrates how the sprit tensions the head of the mainsail. The tension in the head of the sail is transmitted to the masthead, where it pulls aft strongly (somewhat like stays) and that, in turn, puts tension in the luff of the jib. A wonderful side effect is that as the wind gets stronger, the tension in the head of the sail gets greater, with the result that the tension in the luff of the jib increases just when it is needed - all in a rig which can be made by hand from a few bits of wood and some line!

Phoenix III getting to windward in fresh conditions with the jib standing very well, despite the lack of stays. In most other free-standing rigs the luff of the jib would be sagging badly.

Here is the same boat in even windier conditions, with a reef in the mainsail. Despite the reefed main and the blustery wind, the jib is standing very well once again. Note how the sprit snotter has been stretched by the stong wind and consequent high tension on the snotter - the crease from throat to clew highlights the problem - but the jib is fine.

In the photo above, the winds are lighter, but the boat is being sailed without the jib. Despite the lighter winds, the head of the mast is bending aft because there is no jib providing support. The mast bend has reduced head tension in the mainsail, allowing the unwanted throat to clew crease to form. Phoenix III was designed to balance well with or without the jib. Note how the tiller is pretty much centred, indicating that there is very little weatherhelm despite having only the mainsail set.

No rig is perfect, but the sprit rig offers simplicity, drive, low centre-of-area, short spars, and the ability to set a jib effectively without any stays. Perhaps the Scandinavians, Melanesians, Chinese, Dorymen, and Thames Bargemen, to name just a few, were several steps ahead of us...

Fleet - Some Initial Test Reports

Since my last post about Fleet, she has been used frequently and hard. Here is part of the text from some stuff I've posted on the Woodenboat Forum in response to questioning: -

This rig is light-weight - even with the relatively heavy 6hp 4-stroke

Firstly the missing dimensions: - LOA 15'/4572mm; breadth 4' 0-9/16"/1233mm; draft as drawn 4-3/4"/120mm; displacement 543-1/2 lbs/247kg. Hull is stitch-and-glue from 1/4"/6mm plywood panels, sheathed in 6oz/200gsm glass.

Testing so far has been with one, two, and three adults (and various combinations of children) using a 6hp Suzuki 4-stroke outboard which weighs 57lbs/26kg - the motor is brand-new and therefore tight, and no propeller development has been attempted. In relatively rough beach conditions (an open ocean exposed surf beach on the Australian east coast) with two large men aboard weighing 385lbs/175kg plus motor, and sundry equipment including water, the GPS-measured speed varied between 10 knots and 12 knots depending on trim and point-of-sail so to speak. The boat has been taken out through dumping surf, and back in again to the same beach, running straight up the beach at wave speed- this has been done repeatedly after fishing trips in the early hours of the morning.

On the day of the initial launching the boat was able to plane with three men aboard, although nobody had a GPS so the speed was not recorded. Now the speed may technically have been in the semi-displacement range, but the boat felt as though she was planing, and operated very nicely.

She has also been tried using a 2.5hp Suzuki 4-stroke and ran in a pleasant and surprisingly fast semi-displacement mode (two men and one man aboard). So far we haven't been able to record GPS speeds with the 2.5hp motor. As far as I'm concerned, the ultimate motor is a 4hp, because it is the largest motor we can use in this State without registration.

Limited rowing has been attempted, but results so far are encouraging. Here is a quote out of an email (unsolicited) from a very experienced tester: - Hi Ross, yes I went East in Will's lightweight boat, your "Fleet" (called "San Pedro" ) this am.
Bit of a dump of waves on the beach at Moffat, but patience was rewarded by a nice clear push off the beach and a responsive (she shot away) row by the "old man" took us out quickly as the first couple of pulls on the motor failed to fire.Quite a good ground swell, but lovely conditions on the surface with very light winds.

We motored around trialling the "new 6hp" for quite a while, and on two way runs found about a steady average 10 knots. (two up, (170kg plus say 15kg of gear). We did go to 12 with some wave assist. The waves go faster than the boat of course, which I believe adds to its safety as the fine entry would induce broaching at speed, a vice to be avoided in a light outfit.

Minor adjustments to trim (passenger facing forward and not back) lifted the speed by 10%.

A much nicer feel under way than a "tinny", of that there is no doubt.I must say Ross, I was impressed beyond expectations as she really moved considering the load and was soft riding and quiet. I guess one of the benefits of the low power is that you can't get airborne, but you sure cover a lot of ground at 10 Knots. The boat with its glass skin and inhales and gunwales, seemed very strong and inspired confidence. I reckon she would be a fairly wet of course if choppy and the wind is off to the quarter. She will benefit from some attention to that aspect. (I know you already have the solution in mind.)
As a bonus on four short drifts away from Bray's reef, we kept four very respectable fish. (One squire and three sweeties, the biggest being over 1.5 Kg.)Our return to the beach was fun with the good swell still running. We again just picked the time and Will. followed a good wave (with a gap behind it) and went smoothly (at 10 knots) up onto the beach. We jumped out and started pulling, one on each side and she went up the sand like she was on grease. (This is noteworthy as even a light "tinny" binds to the wet sand and is a cow to move up a sloping beach)Will put the dolly wheels under her and we ( actually Will and friend Tim) walked her back up the ramp and then the path to the unit.
Total time to the house from leaving Bray's reef was 15 minutes exactly. Some sort of record for off the beach I reckon.The boat is a winner Ross, and such an easy build, with practical, useful, outcomes. My guess on motors is 6 hp (maybe 2 stroke) for outside, and 2 to 4 for calm work would easily get hull speed with a load. The big hatches that Will put in are fantastic, and we had all sorts of stuff in them. I wouldn't have it any other way. All he needs now is a leeboard, tiller and a fan or crab claw sail, and the picture would be complete. (wink wink)Thought you'd like a report from an old seasoned observer of small powered beach boats.Good luck and kind regards John

I also had this to say on the forum: -

The owner has just been on the 'phone to me to say that he has been taking out a lot of experienced boat-fishermen up where he lives in Caloundra (north of Brisbane, Australia) and he says that they are overwhelmingly impressed with the boat in the tough beach conditions they get up there - serious surf! What Will said was that these guys have forgotten what it is like to go beach fishing with a light and (hopefully) capable boat like Fleet (San Pedro) because they have spent years using tinnies and 'glass boats with big motors, and have forgotten the joys of light wooden boats.

On the day that the Tuna you see in the boat were caught, Will picked up a friend by backing down to the shore in substantial surf using the little 2.5hp motor and keeping the bow to the waves. They then went out through the surf to the point where he had seen the fish, and both got a hook-up. He said that even though they were relatively small fish as Tuna go, the pair still pulled the boat through the water enough to make a noticable wake. He said that characteristic makes her a "soft" fishing boat. I'm no fisherman, but he says it is a very good feature. He bled and gilled the fish on the way back in, and bailed the blood before the beach.

A significant point is that his friend is a real estate agent, and had put out his signs before coming down to meet the boat at 7.30. They completed the whole fishing and cleaning operation and were at home just after nine. The real estate agent went home, showered and got to his first "open house" before the advertised time of ten o'clock! The point of that long story is that if they had been using a large boat with 300hp of outboard, that fishing trip would not have taken place. Small and wooden is beautiful!

I'll report more when we get GPS data when using the 2.5hp, and if we can get one, a 4hp.

Swedish Sailing Pilot Boat - Lotsbat Skum

Geoff Leedham is a teacher at St. Philip's College Alice Springs, here in Australia. Alice Springs is right in the centre of Australia, thousands and thousands of kilometres from any coastline, right out in the desert country. Yes, you have to have schools everywhere, but what makes Geoff unusual as a teacher is that in this arid and remote location he runs a boatbuilding program for high school students. Geoff's program involves at least four different designs (to my knowledge - there may be more) and exposes the participants to a range of differing construction methods and techniques - for this I commend him.

Geoff with some of his students. The beautiful boat they have built, and are displaying here, is an Iain Oughtred-designed John Dory

Imagine what sorts of problem-solving issues have been dealt with by the high school students who built this boat

Another view of the John Dory as she sits in the school foyer, displaying the complexity of work required from a young team - art, engineering, chemistry, arithmetic, manual arts, project management and housekeeping to name a few.

As you may have determined, Geoff Leedham is an enthusiast, and like all nautically afflicted people, he has his own dreams. Some months ago, Geoff approached me by email and 'phone, seeking help with a pet project. The design he wishes to build represents a Sailing Pilot Boat from around 1910, and Geoff has obtained basic historical drawings from Bertil Andersson in Sweden. http://www.batritningar.se/Default.aspx.

There are two problems: -

• there is no table-of-offsets;
• Geoff wants to build in glued lapstrake and therefore hopes to minimise reverse curvature in the hull to simplify construction.

With this in mind, and having spoken with the plans supplier, Geoff asked me whether I could produce a modified set of lines which avoid the use of reversed sectional curvature, supply a set of building offsets, and draw up a schedule of scantlings for the new construction method. And just to top it off he wanted a heart-shaped transom in place of the original wine-glass.

An outboard profile and plan view taken from Bertil Andersson's website. I'd like to show you the body plan so as to give some indication of the extreme reverse curvature, but I do not want to show material without permission. However, you can take it from me - this is a curvatious boat in the extreme!

Here are the principal dimensions courtesy of Bertil Andersson: -

LotsbåtSkum
20½ foot.Length 6190, width 1800 mm.From Kalmarsund. Build in 1910's by Pelle Fräsare in Kalmar, Småland. Completely in oak.

Wondering whether my friend Mr Leedham had handed me a poisoned chalice, I gave it my best shot, and here are the results: -

These are my lines incorporating many changes from the original boat (which I commend to you, with the suggestion that you purchase plans from Bertil Andersson). You can see that cross-sectional reverse curvature has been reduced greatly, particularly amidships and in the run, but that the profile and plan have remained in the spirit of the original. This will be a lighter boat, reflecting her changed construction method, but she retains the character of the original with minimal changes. 

The above renderings show the modified Skum at 6.197m x 1.836m x 0.525m draft ( 20' 4" x 6' 3" x 1' 8-1/2") at a displacedment of 1041kg (2,290 lbs)

Below is a youtube video showing a fibreglass replica of the same, or similar boat to the one in the original drawings, under sail.

In addition to the lines drawings and off-sets, I have supplied Geof Leedham with a fairly detailed scantlings schedule, which I may publish if there is interest, and if Geoff agrees. He has paid me some money, and I need to be sensible with what I publish in case he refuses to take me for a sail!

Isn't it amazing to see what comes from a scheme to build boats in the desert?