Thanks guys ,always enjoy design and reading different perspectives on multihull design ,-
On a practical application note ,-one aspect for the update of numerous existing cat designs is the adoptation of new sq top mainsails ,--which moves the CE back ,--and conversly also adding a new spin snuffer system on cat designs not originally designed for them ,--but sail very well with the addition of them .The 20s have been an area of interest towards a Formula 20 rule for N A ,-The interest for next years Tybee/Atlantic 1000 will be as a Formula 18 and NA Formula 20 EVENT !!which will open up numerous possible boat types and combinations of sail plans and board rudder coresponding combinations ,--based largely on the CE to CLR design aspects. Also I very much like the idea of allowing adjustable stays for distance racing ,--as the 60 tris use now,--They seem to be sailing away from the Parlier cat design -http://www.thetransat.com/en/default.aspx
This of course allows adjustment by mast rake for and aft to help achieve a balanced CE TO clr -a balanced easy to control helm so important in high wind and sea conditions on the Atlantic. The adjustable stays also allowing ease of righting if capsized ,-evan possible by one if needed in an emergency .
The larger sq top mains adapted to existing designs in windward mode {no spin up} require the CE move back or rig forward {not always desirable in seas} --the design solution by Bill R on the ARC designs of shared lift ,using a larger rudder and allowing some loading on it seems ideal in getting more area aft in calc to balance the added sq top aft sail area . It allows better control also .
The recent change to the inter 20 larger rudder configuration is indicative of this thinking and allows a little more mast rake which is faster with the spin up ,mainly due to better balance and helm control .
tHE TRICK IS OF COURSE the changing CE with the 270 or 350 sq ft chute up set forward on a pole moving the CE way forward ,--while conversly in windward mode with larger sq top main and small jib moving the CE back --way back -then how to achieve some type of reasonable balance between the two .--The adjustment of stays seems an ideal add on as well along with all other design factors effecting CLR to CE ,mentioned earlier .-board placement rudder area ,hull ,sail plan -aspect ration -reef capabilities etc .
This could be applied to numerous existing designs -
H-20S N-60s -all 20s . for example -A Nacra 6/0 with the Inter rudder system or Arc rudder system would allow it the same inter 20 type sail plan and mast ,plus spin snuffer and most likely be potentially faster in numerous conditions .
An ARC 20 version -based on the ARC 21 -would be a great ocean racing Formula 20 cat design ,-though I,d like to experiment with a canted hull version and think a CF mast is needed ,---that mast weight reduction being one of its main speed features.
We may see a number of Formula 20s for NA with the larger rudder shared lift design feature to help solve the CE to CLR ,-adding a safe easy adjustable stay system may be the next innovation . I recall the 87 World 1000 ,-the Hurricane cat design entered did use adjustable stays ,-nothing new here ,-just time for it to be refined and used more in distance racing .
The design challenges and putting together a wider variety of 20s to compete always increases the development and speed potential as well as seaworthy features of design .
Hope we see this in the seasons ahead and in major race events like the 05 Tybee Atlantic 1000 ,-plan to be there on a NA fORMULA 20 !!with these features and hopefully a good CE to CLR balance for good positive steering -handling and seaworthy craft that allows us to finish well.-again
Carl
