Advantages and disadvantages of the slender and long Square Metre Boat, the development of the so-called Skerry Cruiser, and how beam is measured since 1925. A brief look at the compromise between minimal water resistance in light wind and the ability to carry sail in a fresh breeze.
Rapid Skerry Cruiser development in the 1910s
The slimmer the boat, the better it performs on light-wind waters such as the Stockholm archipelago, on Berlin lakes, in southern Germany, and Switzerland. On the other hand, a boat needs a certain stability through width, in stronger winds. If it’s too slender, it will lean too much to one side in winds of 2.5 Beaufort and above, losing height and speed when sailing close-hauled.
22 sqm boat in a fesh breeze in Flensburger Förde – Photo Michael Kurtz
The Square Metre Boat was built according to a Rule agreed upon in 1908, which initially limited the sail area for various square meter classes, but otherwise allowed scope for developing the fastest possible boat. Since propulsion was limited by sail area, the lowest possible drag was sought and found after cautious beginnings in the 1910s with sleek, slim, flat-sided, and lightweight boats.
First, the bow was stretched with a V-shaped forward extension. The rear overhang remained short and wide for a while. Then the Skerry Cruiser also became longer and more delicate aft. The rapid development of length-to-beam ratios is clearly evident in the 55s. Eva, one of the first typical archipelago cruisers as we know it today, was built in 1915 according to plans by Erik Salander.
I know Sonja, last mentioned in the table, from occasional encounters with her at the Schlank & Rank Regatta off Fehmarn. Up to Force 2, the sleek, approximately 5-ton racer, Gamle Swede, is a force to be reckoned with. At Force 2.5, she starts heeling, and the tide turns in favour of the 3-meter-wide and stiffer Swede 55.
Development of the length-to-beam ratio
Boat
Launched
Length
Beam
Length : Beam
Eva
1915
12,60 m
2,35 m
5,4 : 1
Nerida
1916
13,33 m
2,30 m
5,8 : 1
Lila
1919
13,65 m
2,13 m
6,4 : 1
Sonja
1920
15 m
2 m
7,5 : 1
The Skerry Cruiser Rule, as the class regulation formulated in 1908 is called, was repeatedly revised. The planking thickness of the hull was increased. To slow the development of increasingly slender boats, minimum widths were added to the Rule in 1916 and then again in 1920. Since the width is most easily measured inside the boat, it is determined below deck. So the actual width is the inside measurement plus the prescribed planking thickness.
From suitcase width to mean beam
Initially, attempts were made to make the boats wider using an imaginary rectangle which had to fit within the main frame, the so-called suitcase width. Subsequently, some Skerry Cruisers were designed with almost square frame shapes. The class remained a controversial race boat. Since the game of rule changes and exploited loopholes could not be continued this way, Prof. Karl Ljungberg revised the Skerry Cruiser rule so comprehensively that the class was restarted in 1925.
Beam now determined as mean beam on three Levels (b0, b1, b2) at main frame – Svenska Skärgårdskryssare Förbundet (SSKF)
The 1925 Rule measures the main frame at three heights: at the deck edge as measurement b0, then at a specific height above the waterline as b1, and then slightly below the waterline as b2. According to the 1925 Skerry Cruiser Rule, these three widths together constitute the so-called mean beam. The widest beam above water is calculated with a factor of 4. The following drawing shows the geometry of all interrelated measurement planes.
Die Messebenen der Schärenkreuzer-Regel von 1925 – Svenska Skärgårdskryssare Förbundet (SSKF)
Building the Skerry Cruiser longer, lead to a wider and heavier boat for the sake of increased resistance. This is advantageous in windy conditions because it is stiffer and weight plays a less important role. In light winds, more water resistance has to be overcome compared to a shorter, slimmer, and lighter boat. Instead of choosing the next longer and slimmer boat to suit the area, a well-considered compromise was required. This is what makes the class so interesting.
The third row of the following table lists the average width as Mean Beam at Main Section for all nine archipelago cruiser classes.
Tabelle mit wesentlichen Maßen der Schärenkreuzer-Regel von 1925 – Svenska Skärgårdskryssare Förbundet (SSKF)
When Harry Wustrau designed the first German 40 m2 Skerry Cruiser in 1920, he came up with a fairly short boat, with few overhangs fore and aft for choppy North German. Wustrau explained his ideas in the 5/1922 issue of Yacht Magazine. Between 1920 and 1924, a whopping 48 40-foot skerry cruisers were built in the German Empire, all them consistently stretched. The table below shows the development. It culminated in a length-to-beam ratio of 8:1.
Boat/first located
Sail#/Launched
Length
Beam
Length to beam
Mia II/Kieler Förde
R1/1920
9,93 m
2 m
4,9 : 1
Saga/Wannsee
R9/1921
12,46 m
1,92 m
6,4 : 1
Rumtreiber/Wannsee
R44/1924
14,28 m
1,88 m
7,6 : 1
Berolina V/Wannsee
R46/1924
14,33 m
1,77 m
8 : 1
1925 relaunch of the Skerry Cruiser
Things could not go on like this. The fourth version of the Rule had serious consequences for the 40 m2 Skerry Cruiser. Agreed upon in 1915 as the last class through the merger of the 38s and 45s, over a hundred of them were built in Sweden alone within a few years. They were also popular with German sailors in Berlin, where, as shown, the development was driven to extremes with considerable ambition. Since wider and heavier boats, from 1925 onwards, had foreseeable disadvantages rather than advantages, the predominantly Berlin 40 m2 Skerry Cruiser hype came to a full stop. Today, many of these boats are sailing in southern Germany, some in fabulous condition.
Other sqm boat classes, such as the actively sailed 22s and 30s, have benefited from Ljungberg’s breakthrough since 1925. The fourth version of the Skerrycruiser Rule is available as a 47-page PDF in English on the website of the Svenska Skärgårdskryssare Förbundet (SSKF).
Photo above by Michael Kurtz: 22s at the Flensburg Robbe & Berking Sterling Cup 2016. Updated June 7, 25.→ Subscribe the free newsletter.
