The Transatlantic cat design and team effort scheduled to attempt to break the transatlantic record crossing time in Dec 04 IS FASINATING , it is a scaled down version of the 60 ft Parlier cat .
http://www.parlier.org/site02/accueil/1024x768.html The 60 ft cat is scheduled to race across the Atlantic with the Orma tris latter this year .
The 20 ft version ->
http://www.bowmansunion.com/portal/news/anmviewer.asp?a=1474&z=22 The last record set in 99 was on a modified Inter 20
basic I-20 specs
http://www.sailboatspecs.com/sailboatspecs/boatimages/I/Inter20-sailplan.jpg L 20 B 8.5 W 390 lb Sa ar 215 m 53 jib 270 spin
Read that the I-20 was modified w wings and numerous gear and safety modifications added.
Unable currently to find articles on the record breaking run. Please post if available ,--thanks .
Choosing a proven familiar design is one good way to insure getting across intact ,--some more experimental unproven designs did not sea trial or improve and modify the original design enough , all boats go through this trial process.
Painfull learning experiences as per the innovative Team Philips attempt at THE RACE ,-showed- though a beautifull innovative design with numerous good design features.
http://news.bbc.co.uk/1/hi/uk/957779.stm Its unstayed double masts proving too much moment and structural racking for its supporting area hull in seas.
Wanted to offer some insights as a catsailor and amature cat designer interested in this Transatlantic attempt.
The new planning type cat with two STAYED masts has a good chance of breaking the record . -for several reasons but not its great comparative speed potential to a conventional 20 ft beachcat design. Many existing beachcats would be faster in typical buoys racing they are designed for but not ideally suited to cross the Atlantic.
In thinking through design requirements for a 20 ft cat design to cross the Atlantic, one main difference from typical beach catamaran sailing design criteria is the amount of added water,- food,- equipement,- tools -spare parts ,-communication nav equipement , safety related gear , special reinforcing,- backup hardware, and general misc gear that is required .
Roughly estimated an additional 400 to 500 Lbs beyond normal sailing weight , plus add crew weights and related added gear. Now boat weight added into the design criteria and total weight calc..
Of course added sail area forces ,-moments ,-etc with
simulation and insight of actual ocean sailing conditions are added also.
I imagine the I-20 was overloaded with wings added plus the weighty list required ,-evan though it does have wider mid hull sections of approx. 16 inch, w per more rectangular section shape .
The I-20 hulls were not designed with this much added weight in mind however, much less with the intent of crossing the Atlantic , Its low profile hulls and large diam. rectangular crossbeams have been a problem at times in ocean racing conditions with wave slap on the back lower beam being severe at times in seas ,--now made much worse by the added weight of gear food water etc.
Water alone at a half Gal a day each at 8 Lbs per * 15 = 120 Lbs . Dehydration being a much larger potential problem in tropical sun then drinking water weight as it effects physical ability and judgement .
It must have been a rough ride at times if larger seas or crosswaves encountered ,-typical when the weather patterns go by leaving older large swell ,but then causing smaller 2 or 3 ft crosswaves at a diagonal on top of those .
Kind of a washing machine effect .
To rough scale it appears the new planning cat has substantially larger wider taller hulls ,-20 to 22 in w , though more tapered towards stern with the added volume per seaplane type bow design ,per design team required for total estimated weight ,and sailing attitudes . If your basic restiction is a 20 ft L ,the only option is to add width and height hull volume ,Added logically from this width requirement,- the potential lift and planning from wider required hull shape .
Running through a quick approx. rough hull volume calc of its wide flat bow -stern -mid-sections at a 12 in waterline draft av. of 8 or .66 in per 20 L =13.2 * 64 per cu ft = a very rough estimate of around 800 per hull *2 = 1600 at WL .
Rough est. total weight -500 & gear +400 crew +400 boat
=1300.---all very rough and approx. averages estimating hull volume to weight displacement requirements.
Actual design lines and dimensions would allow an accurate calc. If any CAD catsailors have some insight here please share it ,--thanks .
Designers generally once a WL and basic design lines are established will estimate the weight required to submerge the hull each aditional inch which increases with typical hull shapes as hull volume increases. The typical hull shape design above the waterline having wider deck lines.
Sail forces at various strengths and upwind downwind modes need to be calc.-- moments pitching -etc in comparative design , and heeling hull shape and sections estimated per comperable design models or simulated per actual sailing modes and in seas ,-such as surfing down the backs of big Atlantic swells and into up over the waves ahead at various speeds and angles of heel.
One hull up sailing mode being the biggest difference in cat design from single hull craft .
I marvel at the 60 ft round the globe mono racing craft that look much like large wide single hull skiffs . They are designed to be sailed fairly level as their wide flat sterns and planning shapes would nose down somewhat when heeled excessively without proper lead keel weight placement to offset it .
Wide catamaran hull design has only hull crew gear weight, and typ.mast placement and sail effects, so must be aware of heeling effects on hull design and bow down tendancies in designed shape ,-note how most all have balance and volume taper equally along L , the planning 20 having taper reducing hull width from mid section station aft to a fairly narrow stern ,--The 60 ft version uses a step and very small stern sections. The desired hull design effect being a slight stern down effect when heeling to offset sail forces rather than added bow down heeling effect in sailing mode, particularly in higher winds and seas.
The extreme beam of the 20 planning cat design at nearly 20 ft total craft beam width allows the larger hulls to be driven by added sail area in a proven two mast configuration , having enough distance between them to not cause backwinding or interferance from each other .
This lowers the CE -{center of effort} or center of sail area height above the deck ,making it more difficult to heel or pitch given the same taller sail area on a single mast. The possible negative effect of two masts is the independant motion and moments caused by them , its a trade off of potential positive and negative effects which will favor different types in different conditions.
The course across is approx. 5000 km or 3100 miles ,-made longer by actual sailing course , gybes etc .
If a cat could average approx 12 mph over the 3100 miles + ,--thats average 24 hours a day each day it could easily break the 15 day record by a few days potentially.
-Numerous racing teams ,- have averaged much greater speeds in a number of the W-1000 legs in large seas ,particularly the downwind spinakker runs on the N-6/0S and Inter 20S with GPS readings typically in the 16s sustained for 8 hour legs and much higher at times ,the 120 mile Tybee leg as example---also much slower times some years typically in light wind conditions along shore.
I,m unsure what the typical tradewind windspeed is on the Atlantic region proposed in Dec for the record attempt,-that is a key for design also.
The 20 ft L seems to be an agreed upon L limit .
Taking another larger existing proven cat design, modifying it, and racing it would be another approach to breaking the record ,
though estimating weight requirements.
A more conventional displacement type hull design with larger volume and built in storage capasity and crew sleeping area may be the ideal .
Would the smaller total beam single sail plan typical cat design be capable of average speeds required ,-only if a number of factors are in place , the biggest factor being crew ability to sail the craft as fast as humanly possible for two weeks straight of open Atlantic ocean sailing and sometimes survival type existance without fatigue taking over.
It would certainly add interest to the record attempt if other teams put a race challenge forward and made the attempt a race as well.
