The theoretical maximum speed that a displacement hull can move efficiently through the water is determined by it's waterline length and displacement. It may be unable to reach this speed if the boat is underpowered or heavily loaded, though it may exceed this speed given enough power. Read more.
Classic hull speed formula:
Hull Speed = 1.34 x √LWLA more accurate formula devised by Dave Gerr in The Propeller Handbook replaces the Speed/Length ratio constant of 1.34 with a calculation based on the Displacement/Length ratio.
Max Speed/Length ratio = 8.26 ÷ Displacement/Length ratio.311
Hull Speed = Max Speed/Length ratio x √LWL
A measure of the power of the sails relative to the weight of the boat. The higher the number, the higher the performance, but the harder the boat will be to handle. This ratio is a "non-dimensional" value that facilitates comparisons between boats of different types and sizes. Read more.
SA/D = SA ÷ (D ÷ 64)2/3
A measure of the stability of a boat's hull that suggests how well a monohull will stand up to its sails. The ballast displacement ratio indicates how much of the weight of a boat is placed for maximum stability against capsizing and is an indicator of stiffness and resistance to capsize.
Ballast / Displacement * 100
A measure of the weight of the boat relative to it's length at the waterline. The higher a boat’s D/L ratio, the more easily it will carry a load and the more comfortable its motion will be. The lower a boat's ratio is, the less power it takes to drive the boat to its nominal hull speed or beyond. Read more.
D/L = (D ÷ 2240) ÷ (0.01 x LWL)³
This ratio assess how quickly and abruptly a boat’s hull reacts to waves in a significant seaway, these being the elements of a boat’s motion most likely to cause seasickness. Read more.
Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam1.33)
This formula attempts to indicate whether a given boat might be too wide and light to readily right itself after being overturned in extreme conditions. Read more.
CSV = Beam ÷ ³√(D / 64)
The TELSTAR was designed and built by Tony Smith in Britain from the early 70’s through about 1980.
The UK TELSTAR production was somewhere around 200 boats - first there was the TELSTAR 26 and around 1977 the TELSTAR 8m, which featured a fatter/roomier main hull. There was also a TELSTAR 35 and a version of the 8m which had outer hulls which pulled in close to the main hull while the boat was in the water, but few were built. Tony emigrated to the US and set up Performance Cruising in Maryland. There may have been 10 TELSTARS built in the US in late 1980 to mid-1981 (serial numbers 250 through 259 or 260). The factory burned down in mid-1981, and all molds were lost (Tony started building the GEMINI catamarans after the fire).
Type Year Hull #s LOA Sail Area Weight Comments
Prototype 1970 001 26’ 298 ? Entered Crystal Trophy
MK 1 1970-1975 002 - 080 26’ 340 3500 Std boat. In production 3 years.
MK 2 1976-1977 083 - 171 26’ 300 2800 Floats lengthened?
Version 1978-1979 009 & 187 ? ? ? Folding amas.
Mk 3 1978-1979 172 - ? 8m ? ? Enclosed c/b trunk. Wider center hull.
(Std) 1978-1980 172-216 8m ? ? Standard 8meter. Heavier than later versions.
8 meterE 1980 184 + 8m 285/320 ? Economy lightweight. Tall rig (34’)
8 meter/Std 1981 250-260 8m ? ? Standard boat produced in USA.
T 36 1978 T35 (1 - 8) 35’ 470 11000
A new TELSTAR 26 is now available from:
Performance Cruising Inc.
7364 Edgewood Road
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