Longform articles

This is where we put any longer articles/reports/etc. about the Corbin 39 or their doings. Either the fulltext or downloads.

Voyaging information

Information for people that plan to sail oceans, by Richard & Kathy Bacon who circumnavigated on “Balmacara” over a 9-year period (download pdf here)

 

Design information

Below are some working documents setting out the results of an ongoing study into various aspects of the Corbin 39. Conceptually they are a series:

1. A study of the anecdotal evidence in respect of weather helm.
2. A theoretical analysis of weather helm and various options for owners.
3. A reproduction of the lines plans, the hull form, and analyses of displacement, trim, and static stability.
4. A study of the sailing performance, including the results from Velocity Prediction Programs (VPPs).
5. A study of the dynamic seaworthiness using the ISO stability index (STIX).

 

1. Corbin 39 – Anecdotal Weather Helm Evidence

A owners’ group effort compiled in late 2019/early 2020 by David Sharman, gathering together the anecdotal evidence. The information in this helped with the validation task of the subsequent Theoretical Analysis (see below). There were some uncertainties in the anecdotal study, and the theoretical study was not the last word on the matter either. It was not until the sailing performance analysis (with VPPs) was completed that it was possible to really fill in all of the details and so it is worth reading all these reports in turn.
(download pdf here, (rev 20 02 2020),

 

2. Corbin 39 – Theoretical Weather Helm Analysis

After the group collaborated to put together the anecdotal weather helm synopsis above, we were fortunate to obtain the support of the retired French naval architect Jean-François Masset who has supported us with more theoretically grounded analysis. This effort started in March 2020 during the COVID-19 pandemic. He writes a freeware preliminary design analysis spreadsheet/program for sailing boats. He is generously assisting us in reverse engineering the original Corbin 39 designs. His program creates spreadsheet files which are saved using the filename Proxi as being short for aPROXImate.

The operational versions of Gene-Hull are all in the Software forum of Boatdesign.net : original Gene-Hull itself (for fin keel sailing yacht) (2,3), Catamaran version (2,43), Canoe version (2,4), Dinghy version (2,42), and the pseudo in Boatdesign of Jean-François Masset being Dolfiman.

It is important to note that his PROXI spreadsheets do not follow the actual Corbin hull lines at the extreme stern. This does not matter for statics analysis purposes as those parts of the hull are not in contact with the water. So far he has just finished a first approach of the hull re-drawing including its appendages. These are extremely close to the original lines, and he has had to modify his Gene-Hull software to cater for a canoe-stern hull form with long-ish keel. The Gene-Hull software ordinarily generates many design solutions, and in this case he has had to adapt his software to match the offsets of a given one. We owe him many thanks indeed.

Corbin 39 – initial results of preliminary weather helm assessment – report are (download latest here)

Corbin 39 – hull design, preliminary analysis, working slideset for collaboration sharing (by David Sharman), with many thanks to Jean-François Masset (download latest here)

Corbin 39 – Gene-Hull PROXI 39 output, (by Jean-François Masset), (download latest here)

Corbin 39 – Gene-Hull table of offsets (which are not quite correct at the non-important stern) (by Jean-François Masset), (download latest spreadsheet here) (or pdf here)

Corbin 39 – tabulated data used as inputs in the above (by David Sharman) (download latest here)

 

3. Corbin 39 – Theoretical Analysis – Initial Results re Hull Form and Static Stability

With the most generous support of the retired naval architect Jean-François Masset and his fellow retired colleague Alain Lebeau also of the French oceanographic research institute ‘Ifremer’  we have moved on to consider the static stability issue. The prelimary task for this is to recreate the Corbin 39 hull form in a 3D computer model and the associated linesplan. Then the stability analysis is conducted.

Summary : We have made reasonable assumptions that can be summarized as: an operating displacement of 14,000 kg (30,865 lbs); neutral trim initially; and a Centre of Gravity (“Zg”) placed 3.8cm above the Design Waterline (this is just below where the saloon table top is). We have cross-checked output data from 3 numerical tools (programs) and obtained good agreement for a GZ curve as shown with an AVS of 127° and an area ratio of 6.3. The effect of trim, displacement & draught differences, and Centre of Gravity were also investigated, e.g. when assuming Zg = 0,1m (assuming the worst), the stability is still good , with an AVS at ~ 123,7° and an areas ratio of 4.94.

Corbin 39 – Hull form & static stability – report of initial results

(download pdf report here)

Appendix 1 : Comparison of digital dimensional models

(download pdf report here)

Appendix 2 : DelftShip – Lines plan and basic data

(2a. download pdf design hydro report here)

(2b. download pdf lines plan here)

Appendix 3 : MultiSurf – Lines Plan and basic data

(download pdf report here)

Appendix 4 : The mass spreadsheets

(4a. download pdf from JFM here)

(4b. download xls from DS here)

Appendix 5 : The Gene-Hull trim and draught spreadsheet

(5a. download  pdf report here)

(5b. download ods spreadsheet from JFM here)

Appendix 6 : The Gene-Hull full stability results

(download pdf report here)

Appendix 7 : The ArchimedesMB output spreadsheets for various tonnages, and various Zg

(7a. download ArchimedesMB results as xls here)

(7b. download GZ y RM cada 5 grados results as xls here)

Appendix 8 : Multisurf Results

(download ods results from AL here)

 

4. Corbin 39 – Theoretical Analysis – Sailing Performance & Velocity Prediction Programs (VPP)

Again with the most generous support of the retired naval architect Jean-François Masset and his fellow retired colleague Alain Lebeau also of the French oceanographic research institute ‘Ifremer’  we have moved on to consider the sailing performance of a Corbin 39. This builds on the previous studies of the Corbin 39 models. There are many different spar and sail arrangements for the Corbin 39 models, and they are scattered all over the world, so it is unrealistic to carry out a set of sailing experiments to directly compare sailing performance with each other. Nonetheless owners would like guidance on how they can extract the best possible sailing performance from their particular model, and purchasers would like guidance on how important it is to choose between the available models when considering sailing performance.

There are five documents in this part of our work.

  • Corbin 39 Study – Theoretical Analysis – Sailing Performance & Velocity Prediction Programs (VPP)
    (download covering report here)

Then the detailed SA-VPP and USVPP results fall into 3 documents, « VPP issue and results», « VPP with spi » and « VPP with Disp 15t » all of which are for download below:

  • « VPP issue and results » : is the core document explaining the process and the input data (assuming the 14 t displacement configuration), giving the results upwind, beam reaching and downwind (without spinnaker) for wind up to 20 Knots. (download here)
  • « VPP with spi » : an additional document giving results with a spinnaker up and comparison with spinnaker down (download here)
  • « VPP with Disp 15 t » : an additional document giving results when the displacement is 15 t, and comparison with 14 t results (download here)

Plus a simple spreadsheet:

  • « C39 miles run per day » : a Excel spreadsheet to allow comparison of Corbins on various courses, in various windspeeds, and for different durations (download here as a .xls)

 

5. Corbin 39 – Theoretical Analysis – Dynamic Seaworthiness Assessment using the ISO Stability Index (STIX)

Once again with the most generous support of the retired naval architect Jean-François Masset and his fellow retired colleague Alain Lebeau also of the French oceanographic research institute ‘Ifremer’  we have moved on to consider the study of the dynamic seaworthiness using the ISO stability index (STIX) per ISO 12217-2 : 2015 “Small craft — Stability and buoyancy assessment and categorization”.

The Corbin 39 had a 1970s design intent of “ocean” conditions. In 2020, we can both ask and answer the question, “how does Robert Dufour’s design meet seaworthiness standards set 40-years later”. For a Corbin 39 results are obtained for two loadcases for the mk2 49’ mast ‘cutter’ sailplan, corresponding firstly to an operating displacement of 14,000 kg (30,865 lbs) ; and secondly for an extra 1-tonne of mass placed low in the cabin, raising the centre of gravity, Zg marginally. In general terms this suggests the Corbin 39 design would meet ISO design category ‘A’ for ocean use with a STIX of between 40-42 depending on individual sailplan, construction, and loading. This of course reduces as displacement increases, as is set out in the reports. This outcome accords well with the practical experiences of many Corbins and their owners sailing worldwide over the years. Further analyses extend this to different centres of gravity (Zg) and to the different sailplans.

There are three documents in this part of our work.

  • Corbin 39 Study – Theoretical Analysis – Dynamic Seaworthiness Assessment using the ISO Stability Index (STIX)
    (download covering report here)

Then the detailed results are in two documents available for download below:

  • « Corbin 39 – the STIX issue – as for 22 06 2020, by Jean-Francois Masset & Alain Lebeau » : is the core document explaining the process and the input data and the detailed results. (download here)
  • « SA-STIX final_2020 06 22 » : Jean-Francois Masset has kindly set up a ‘ods’ spreadsheet which any Corbin owner could use to assess his/her own Corbin  (download here)

 

(at the moment we are just concentrating on putting accumulated stuff into the downloads section, maybe more structure will come in due time)