DF Racing

The Serica rating saga The saga of Serica’s rating measurements is complicated, confusing and in some cases contradictory.  It is not helped by the fact that there are three A class yachts named Serica.  However for Derek, Bill and any other A class anoraks out there I will try and explain the story as best I have been able to uncover it.  The original Serica, henceforth to be known as Serica 1, registered as K750, was designed by Bill Daniels and built by Arthur Levison for Norman Hatfield.  When we acquired our hull in 2015, we were loaned the original Serica drawing, signed and dated 1955 from the Norman Hatfield archive and it indicates the design was to be a boat with a Loaded Waterline Length of 55 inches, displacement of 59 lb (44.9 lb lead)  and, by inference, a sail area of 1600 sq inches.  However, somewhere in his calculations, Daniels made a mistake and when the boat was built and measured it was seriously over rating and could not carry the expected sail area.  The keel was apparently modified to reduce the weight and a further note on the drawing states that the measurements after the keel mod were LWL 55.8 inches, displacement 56.5 lbs and sail area 1483 sq inches.  We have another set of displacement calculations dated 6th May 1956 which give a calculated weight of 62.2 lbs and waterline length of 58.05 inches but it is not clear what stage of the boats construction they refer to.  As an addendum on these sheets there is reference to a new lead weight of 38.5 lb compared with the original design figure of 44.9 lb. After building Serica 1, Arthur Levison apparently went on to partially carve a second hull to the Serica design but it was never finished and went missing for about 45 years  Some years later in the 1970’s, Jim Belton, an associate of Norman Hatfield built a plank on frame version of the design, which was registered as Serica 2.  He designed a lighter weight keel for this hull with a lead weight of approximately 35 lb and a copy of this drawing was loaned to us.  We know nothing more about this boat except it was registered as a radio A, K1000 in 1976. Around 2009 the ‘missing’ partially carved Serica hull re-emerged.  It was progressed by John Gale and we acquired it as a bare wooden hull, without a keel in 2015.  We made a ‘light weight’ keel to the Jim Belton drawing and estimates during the build suggested our Serica 3 would weigh about 58 lb and we expected it to be able to carry about 1500 sq inches of sail, i.e. comparable to Serica 1.  When we measured it, to the best of our ability we found the displacement was 57.2 lbs but the waterline length was 58.6 inches.  Calculations showed it would only be able to carry about 1300 sq inches of sail.   This was a bit of a disappointment and I rechecked the measurements and calculations several times and had the rating calculation checked by a well respected A class measurer but the sail area for Serica 3 always came out at about 1300 sq, in.  At the time I was more concerned to make sure the Serica 3 measurements and calculations were correct, rather than knowing why the resulting sail area was so much smaller than Serica 1. A couple of months ago a friend in the VMYG sent me a cryptic email asking if we had an A class yacht called Serica.  I said we did but why was he asking.  He sent us a copy of the October 1956 Model Maker magazine report on the Gosport A class nationals which mentions Serica and its rating problems.  It quotes Serica’s measurements as LWL 55.8 inches, displacement 55.8 lb and sail area of 1472 sq inches, which are close to the original drawing figures after the keel modification.  At this point my brain clicked into gear and I realised that the key factor was our Serica 3 has a significantly longer waterline length than Serica 1.  I measured the LWL of our boat at a range of weights so it was easy to estimate that at 55,8 lbs, where Serica 1’s LWL is 55.8 inches, Serica 3’s LWL would be 58.15 inches, a difference of 2.35 inches.  I checked the weight of Serica 3 using two sets of bathroom scales and a luggage weighing scale and all tallied to within a pound.  I estimate the waterline length would not be more than +/- 0.25 inches in error so there must be another reason for the difference between Serica 1 and 3.  Either:- The early modification to Serica 1 was more than just reducing the weight of the keel The Serica 3 hull carved by Arthur Levison is not the same shape as Serica 1 and was modified in some way, although the overall length and beam tally with the original drawing dimensions. Something happened to the hull in the 45 years when it was missing in limbo When John Gale worked on the hull he changed its shape I have made a silly mistake somewhere or there is some other factor I am unaware of. In the end we fitted Serica 3 with a 1300 sq inch set of sails and it is what it is.  As Mervyn Cook said after checking our calculations, it should be really good (for its age) at Fleetwood in a blow.  The reason why I have suddenly taken an interest in this relatively academic issue is that we are currently progressing the build of another partially built A class hull to the John Lewis Phaedra 2 design and I am curious to see how closely it is going to match up to the original John Lewis drawing. Finally, if anyone knows the whereabouts of Serica 1 and 2 we would be interested to know. Gareth

Result from Friday 27th November: AlanA beat AlasdairR. The order in the ladder remains unchanged - again!

Hi Gareth,   I would like to hear the full story.