Some History 

 

As the winter months are quiet, with not much to report, I asked those in the know for a history of the 2.4mR. This information has come to me via Hasse Malmesten. I hope you enjoy reading it.

 

2.4 Designer Sweden
THE WAY IT STARTED
By Peter Norlin / 2.4 Designer
Sweden


In August 1979, I was sitting on the deck. We were sailing Admirals cup in Cowes, when a very small boat was sailing around the moorings of the Cowes Week racing yachts. This was the first time anyone had seen such a little boat. The helmsman a young German guy was sitting inside the boat, and only the head was seen in the cockpit. He was the founder of this type of boat.


The boat was narrow and looked like a scale down 12-meter yacht, both the sailplane and the shape of the hull, with the approximate dimensions Loa 3.5 m and beam 0.8m.


This boat got a lot of followers like Illusion, Shadow, Millimeter, and Defender etc. All of them went under the name “Bath tub twelve’s”. They were good as long there was little wind and flat sea.


At the same time I was working in the towing tank with Americas Cup 12 meters. The trial horse, which is a boat that I designed as close in shape to the existing twelve’s as possible, to be compared with my experimental design. This experimental boat was a smaller lighter 12-meter to suite the light winds in Newport Rhode Island. The trial horse (scale 1:10) was built in series, to be sailed with a radio control. We were 5-10 sailors who had great fun sailing these boats in regattas. One of them was Odd Lindquist who sailed his own design. Odd got an inquiry, from one of the participants, to design a 1/5 scale of a 12-meter (or twice the size of the 1/10 scale radio control boat). Odd designed the Odd 1/5 that sailed for the first time in 1982.


Very soon after that Jan Törnfeldt (also participant in the group) asked me if he could build a 1/5 scale mini twelve of my design. While working with the tank testing and sailing with the radio-controlled model 12-meter I became familiar of the scale effects. I decided to scale down a six-meter hull, which is proportionally heavier and bigger than a scale down 12 m, and use the scale down 12m rig and sails, which is a little lower than the scale down 6 m rig. I decided the depth to be 1 meter, compared to a 1/5 scale down 12m that gives a depth of 56 cm and a scale down 6m that gives a depth of 66 cm.
All these choices were due to the scale effect from the wind, which is the square root of the inverted scale. This means that the same wind for a big boat is much stronger for a small (or model boat). The square root of 10/1 is 3.16, so wind strength of 3 m/s corresponds to 9.5 m/s for the model twelve compared to the full size twelve.
(The square root of 2.5/1 is 1.58. Thus the wind is 1.58 times stronger for a scale down six meter, and square root of 5/1 is 2.24 so the wind is 2.24 times stronger for a scale down 12 meter, compared to a mini 12. )


I designed the boat to float as deep in the water as a 6-meter in racing trim with all sails and crew onboard. To achieve this I had to take out approximately 35 kg from the ballast.
Jan Törnfeldt started to build the Norlin Mk I, he made an extraordinary work regarding the anatomy for the helmsman. With a lot of work and carefulness he had 2 boats ready for the spring 1983. This new “mini twelve“ proved to be a very good sailing boat that could cope with most conditions.
The first two boats had a fin keel with a bulb. The third and boats built after that had internal ballast of eight to nine retractable lead pieces. This made the boat easy to move, the hull upside down on the car roof and the lead in the rear. We sailed on different places around Stockholm and on the waters inside Stockholm. Fleets were established in Saltsjöbaden and in Waxholm where Håkan Södergren built up a fleet. The boats participating were Odd 1/5,
Södergren Mark I and II and Norlin Mk I. The Södergren boats were “ scale down 6 meters”

After some time the class started to grow, and as the Norlin Mk I was designed to the following thoughts and items, I proposed this MINI 12 RULE to the Swedish Sailing Association:
The rule is based on the existing International twelve-meter rule in scale 1/5 with the following changes.


Displacement formula (0.2xlwl + 0.06) squared (scale down from the 6-meter rule)
Freeboard, when calculating the rating max deduction F = 292 mm (from the 6-meter rule)
The boat shall float at her dwl with an extra ballast of 35kg.
Max depth 1m
Sailplane and sail measurements: (from the 12-meter rule)
Measurement deck 36mm above covering board
Mast height 5m above measurement deck
Fore triangle height 3.75m above measurement deck
Upper and lower battens 270mm
Intermediate battens 360mm
Top width main 72mm
¾ width main 41%
½ width main 68%


Scantling rule:
regarding material. Like the 12m rule
Sandwich material only in the deck
Deductible internal ballasts at least 8 parts.
Unsinkable
Min glass weight 900g/m2. Kevlar and carbon fiber not allowed

The reason for the 35kg extra measurement ballast is as follows:
My wish was to have a boat floating at the same racing trim as a 6 meter.
As the crew weight + sails etc. of a 6m is app. 500 kg.
This weight scaled down 500/15.625 = 32kg
32kg + 35kg taken out from the ballast gives a crew weight of 67kg, and the boat will float when racing at about the same trim as a 6-meter.
This rule was the unofficial rule until 1986, when Odd Lindquist, Håkan Södergren and the Swedish chef measurer Lennart Olsson and me, wrote (after a lot of meetings and work) the first official Swedish Mini 12 Rule that came in force 1988 in the Scandinavian Sailing Association. Claes Hultling a strong character of the class brought the class to ISAF who accepted the rule 1993.


In 1986 Imma Björndahl started to build the Södergren Mk III, and the exchange sailing started between Sweden and Finland.
The Norlin Mk I was changed to Mk II in 1986, and the Norlin Mk III was designed 1987.
Before the unofficial World Championship in Helsinki 1988 the mini 12 sailed with an overlapping genoa.
From a suggestion from Claes Hultling the jib was shortened to 100%. The reason was that it was very hard for all sailors including the disabled sailors to tack.
The foot of the jib was then changed to 110% after an investigation among the sailors.
The shorter jib is good because it opens the racecourse and may be more important, it avoids a lot of accidents due to bad sight behind the genoa.
The fact that the boat is very insensible to weight of the crew is due to the longer waterline with a heavy crew, without increasing the wetted surface too much. Many times you can see very different persons on the podium after a long regatta.


This little racing boat is a thrill to sail. It has a great “feel” and as it doesn’t lose much when tacking, your tactics and strategies becomes very important.
In 1984 Claes Hultling sailed the boat as the first disabled person. Claes found that the boat could be sailed on equal terms and introduced the class to the disabled sailors, since the beginning of world Championships there has been three disabled winners, this points out how wide the range of helmsmen that has the chance to win any regatta.

Types of 2.4mR

  Name country of origin
1 Angermark Sweden
2 Bent Sörensen/Moller Denmark
3 Bergendahl Sweden
4 Composite Craft 2.4mR design:Garry Crothers UK
5 Cook Mk1 UK
6 Cook Mk2 UK
7 Elo 2.4 Finland
8 Falle Mk1  Sweden
9 Falle Mk2 Sweden
10 Fauroux 2.4 France
11 Felci 2.4 Italy
12 Howlett Mk1 UK
13 Howlett Mk2 UK
14 Jofs Mk 2 Finland
15 Jofs Mk I Finland
16 Norlin Mk1 Sweden
17 Norlin Mk2 Sweden
18 "Norlin Mk3 Sweden  
19 Odds (Odd Lindquist) Mk1 Sweden
20 Odds (Odd Lindquist) Mk2 Sweden
21 Odds (Odd Lindquist) Mk3 Sweden
22 OE (Ole Eide) Mk1 Norway
23 OE (Ole Eide) Mk2 Norway
24 OE (Ole Eide) Mk3 Norway
25 Olsen Denmark
26 Ossiansson Mk1 Sweden
27 Proton . Poland
28 Ridder Mk1 Sweden
29 Rode Mk1 Denmark
30 Rode Mk2 Denmark
31 Sodergren Mk1 Sweden
32 Sodergren Mk2 Sweden
33 Sodergren Mk3 Sweden
34 Sodergren Mk4 Sweden
35 Sodergren Mk5 Sweden
36 Sodergren Mk6 Sweden
37 Stradivari Hc Sweden
38 Stradivari Mk1 Sweden
39 Stradivari Mk2 Sweden
40 Stradivari Mk3 Sweden
41 Stradivari Mk4 Sweden

 

 

My 2.4 story. By Ingmar (Imma) Björndahl  FIN

Submitted by daughter Annika.

I was on a trip to Skelleftehamn, Sweden with my wife Rauha and Kjell Slotte to collect sails for our Still 525 at Delfin Sails Holmgren. He wanted me to see a small sailing boat called a mini 12 that was designed by Håkan Södergren.

In his boat-house we found a mini 12 built by a Danish builder that Gunnar wanted to trade with my Snipe (snövit). I loved the little boat and the deal was made in a second. I remember Rauha complaining that we have lots of small boats so why keep buying more

I came with the mini 12 to Mustakari sailing pavilion in Kokkola to launch her for the first time. There was too little lead in the keel and we were forced to sail with the main-sail only. The local newspaper was present and the reporter tried the boat herself. She was happy and excited about sailing it alone because it was something she had never done before.

We contacted Håkan Södergren and he invited me and Tom (Tomppa) to come to Stockholm and collect the plug to his mini 12. Within a week we were off to Stockholm to collect the plugs. The plugs were stored behind a shed, there was no one home but we loaded the plugs on our trailer and drove to a local printing shop (as agreed) to pay for the plugs.

The first serial production of mini twelve’s was started. We had built a total of about 125 Södergren boats when we left to mini 12 World Championships in Sarasota, Florida in 1990. There the Södergren design had no chance against the new Norlin MkIII design and we where defeated in every weather condition. This is when I decided to contact Peter Norlin which I did as soon as we came home from Florida.

Peter invited me to come to Älvsjön Exhibition Center in Stockholm during the annual boat-show to meet him. It was a great pleasure to meet Peter and the start to a life long friendship. We went and visited the builder that was building some boats for Peter in a basement and he was happy to see someone take over the production and start to build the fine design in series.

We produced the moulds from a wooden Norlin MkIII built by Hasse Malmsten. These moulds are still used today by Charger Composites to build the Norlin MkIII. In 2006 after building around 400 Norlin MkIII, I retired from boat building and My daughter Annika and her husband Evert continued to build the Norlin MkIII in their company Charger Composites.

Imma