• Improved aerodynamic efficiency
• Easy control with minimum crew
• Safe mechanized handling
Inspired by the principles of suspension bridges, suspension sails are a step forward in technology and efficiency.
By separating the functions of horizontal profile control and vertical twist control, the enormous vertical control forces are carried by strong vertical luff and leech ropes. Consequently, suspension sails may be made of conventional woven sailcloth.
The Project was initiated in 1980 by the charismatic Indonesian Minister
for Research & Technology: Prof. Yusuf Baharuddin Habibie (=Darling).
He had studied Aviation Technology in Aachen Germany and had the Vision
to kick his country within 10 years form the 19th into the 20th century. He had founded BPPT,
the ‘Agency for the Assessment and Development of Technology’ to promote the development of all technical branches, including aviation & shipping.
Our Project was part of ‘KAPAL SURYA’ (‘Solar Ship Project’), and he suggested to the German Minister for R&T a joint (bilateral) R&D-project (not ‘foreign aid’) for sustainable inter-island shipping.
The first step should be to utilize that portion of solar energy which was already converted from radiation into mechanical wind flow to directly propel the ship without further conversion losses.
The German project management used the term INDOSAIL as a catchword or informal brand name (in capital letters), and it survived the Project. It is also a tribute to the late Prof. Habibie, who opened the chance to subsidize basic research into modern (appropriate) wind propulsion of cargo vessels. Indonesian Partners were BPPT in Jakarta and the shipyard PT PAL in Surabaya. German Partners were the ship model basin HSVA and the consultant F. Weisz FEG in Hamburg.
peter@schenzle-hamburg.de
LOA: 63 m
LPP: 50 m
Displ.: 1700 t
Dwt: 900 t
As: 1050 m2
LOA: 78 m
LPP: 65 m
Displ.: 2450 t
Dwt.: 1550 t
As: 1400 m2
LOA: 93 m
LPP: 80 m
Displ.: 3200 t
Dwt.: 2200 t
As: 1750 m2
Reasonable Sail Configurations — never without Jib!
All sails are made of soft UV-resistant cloth. They are of flat
cut with a hollow curved leech seam. The sails under wind load
are suspended by a strong, curved leech rope similar to a
'suspension bridge'.
In a multi mast sailing rig—as with an aircraft wing in the start or landing configuration—the optimum adjustment of the sail- or wing elements to the local
flow conditions is resulting in a fairly open sheeting of the jib
and a progressively closer sheeting of the following sails, with
the mizzen sheeted closest. The purpose is to force the wind flow—step by step—to turn its direction closer to the midship line, for
optimum propulsion thrust and even distribution of the
contributions of the sail elements.
A fore-and-aft mainsail attached to the mast or a luff roller
close to the mast is suffering from disturbed flow on its most
critical leading edge. The gap between mast and roller is
marginally improving the flow but a considerable improvement is
found from the slipstream of a jib sail in front. Thus the
propulsive effect of the combination is much more than the sum
of the effects of the individual sails.
Consequently, to open the gaff sails only is not an efficient
configuration. It is suggested instead, to open the jib and
mizzen sails first and to open the gaff fore and mainsails then
to a degree compatible with the course and wind conditions.
With increasing wind speeds, the gaff sails should be reefed
progressively with the jib and mizzen sails still full.
The collected experience of now four years of cargo service has proven the potential of a modern utility sailing rig:
+ easy and safe handling by a small crew,
+ efficient sailing on all headings,
+ well controlled sail trim in every sheeting,
+ easy control of pre-tension by frequency-check,
+ short-term sail opening, continuous reefing and fast furling,
+ safety by ‘sheets-off’ function,
+ flexible level of mechanisation, from hand-winches to semi-automatic operation.
Peter Schenzle
August-Krogmann-Str. 155
D-22159 Hamburg
Peter Willcox
PO Box 66
Islesboro, ME 04848-0066, USA