Heard Amac interview talking about how long it takes to trim sail in light weather conditions, i thought this might help.
Glue this device to your deck to provide 100mm throw on the middle control line with a total purchase of 24:1.
Everything is shown to scale.
Assuming vang of 16:1, 6:1 for down haul and 2:1 for outhaul so at 24:1 I am matching the current amount of purchase. With larger diameter rope with an easier pull the overall effort for skipper should be less.
Two features to make it easy to adjust:
- Series of holes in lever, move the take off up the lever to increase the throw of a particualr system
- Turnbuckle on each control line to set the zero point of each system.
To
It doesn't need to be a single module (could be split into cleat base and lever base) but this way the loads are contained within it rather than applying bending moments to the deck.
Grey is carbon, cream is 80kg foam.
Carbon is moulded from a bent sheet metal mould. Port and stbd halves moulded up, glued to foam and a bridging laminate links the two cleat bases.
Uhh not sure I was listening to the same conversation (beers roundtable 3).
ReplyDeleteI'm pretty sure though that Amac's point was that slow trimming and twist control was needed (i.e. the desired behaviour) to avoid separation of flow (i.e. stall) due to sudden sail angle of attack movements, basically in response to Bora's wing bar bounce/pump/ooch strategy. No one else seemed to get the newtonian mechanics of what bouncing does to the mainfoil flow.
Frankly, my aged opinion is that all the "old guys" had way more light air experience under their belts and really knew what to do, and more importantly, when (Simon...) in those glasshopper conditions. Whereas the young jocks were lost on the dynamics of it all.
I loved Amac's comment that when on foils in the marginal light stuff that the heavier sailor always has the advantage. He's obviously right. The bafflement of the young 'uns made me laugh.
Your device is very interesting however, but I really think will prove far more useful in 20+ knots, especially for gusty unstable conditions.
So, what does it actually do, just pull on the outhaul cunningham and vang together at different ratios?
ReplyDeleteI would have thought a rig-tensioning device (or at a stretch, a mast ram) might have provided the same effect with better rig dynamics.
I haven't listened to any of these talks yet, but the whole issue of rig settings for pumping in marginal conditions just reminds me of big rig windsurfer set-ups where you dump the outhaul and cunno and let the mast do all the work for you as you bounce the board. Similarly on my old scow (now we are talking a long time ago!) I used to basically "set and forget" the rig in marginal conditions as I bounced on the wing and let the mast do all the work.
Is the rig too locked in with the spreaders and rig tension now-a-days to provide sufficient response in these conditions?
On another mostly-off-topic note, why doesn't anyone use lever vangs anymore? Is a cascade system really lighter?