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About Frogman56

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    Ocean stuff, wine, history, staying sane

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  1. WTF? Dan is still fighting the last war.. Gunna build a new quarantine facility! He should be excluded from public office forevermore.. Cranky Frog
  2. Just one generalisation....most keelboats are bow down as heel increases, though except your old metre yacht from that. Max aero span (at say 20 degrees heel) is then at around 3 degrees rake. The Farr office would typically optimise around 3-4 degrees leeway at +3 degrees helm for (say) 12 to 14 tws, upwind. The effective rudder aoa.... 6 or 7 degrees, improves the hydro LD. Hull leeway is not a very efficient side force generator.
  3. We are in the land of 84 (approx) tradeoffs here. Having sailed on some medium to largish keelboats where in three cases the thing only had neutral to lee helm, and another class where the thing had so much weather helm (and not say small rudder as well) that in 12 true the main had to be fully bladed and boom below centre to go upwind. In one case, the NA blamed the sail designers aero model, etc... But all the above were/are NA designed using the 'best software'. Sarcasm font required. Remember, the Farr office did the best job for a long time, with the concept of minimis
  4. BB As a colour, did not, did not realize I loved olive green...
  5. And... WTF? It is 2021 last time I looked! Ye olde chain girth rule is almost 100 years old!
  6. It cannot provide any material lift, nor, if flattened below around 4% camber, much drag. It is just hanging in the onset flow..
  7. Don't sail with so much vang on. For most configurations and situations, more twist is faster. There should always be enough twist that the head of the main inverts first.
  8. Probably GA is talking about the half height force and LD. My comment is only about the tip twist and 'special effects'
  9. Kiwi It was reported that the solid wings with the head inverted were efficient at around 15% of total RM at the top of the wind range. The twin skin would be lucky to generate 10% of that. The other benefits re ce and tip vortex are important though..
  10. Looks good, but cannot make RM like the solid wing. Good vortex suppression and lower CE though!
  11. I think that the most advanced setups in the fleet now are way more efficient than you guys believe. This is apparent from the range of both rigs extending, Tech 2 (now) and Honda last year were good to 16 tws with the big rig. Tech 2 is ok to almost 30 with the small rig. The well tuned square top is a good bit of kit.
  12. Al, The longer F40 hull will have less drag than the J32 at 7 knots...
  13. Sailor Al, Another cross check method is to estimate RM at optimum heel, which then enables a good estimate for total rig side force, sails plus spars. So, using Farr vpp, ORC data and formulations, We can have a good stab: P 16.7, BAS 1.75 Freeboard 1.0 Draft 2.60 ORC use 40% of rig height and draft as the heeling couple, which works out to 8.82m ORC tells us RM 1 degree is 172 km and crew weight is 780 kg, I.e. above 30% of the ballast package. Farr VPP gives optimum heel angle for 12 TWS upwind as 21 degrees, btw with leeway of 3.4 degrees, V = 7.05 k
  14. Remember they are upwind at around 10 degrees awa and down at around 25!
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