|Skilfully balancing in good foiling trim,
the instant expertly captured in a nice still image.
Remaining in this trim requires very active control.
Image copyright Jasper van Staveren
Report here: http://www.a-cat.org/?q=node/389
Full results here: http://www.roerkoning.nl/2014/klev_apr14.html
This win further supports our findings regarding the effectiveness of the concept, shape, section and construction of our rudders.
Various skippers confirm that they offer better ‘damping’ than any others on the market with consistently less drag and the ability to remain effective for longer (higher heave values) without losing grip.
However it is worth noting that the combination of even the best rudders with J foils (where both foils are used at the same time), while undoubtedly faster than non-foiling configurations, is a very compromised solution. And one that we are hoping will be greatly improved upon very soon thanks to the development and testing work we are carrying out now.
|Using two foils halves the effective beam. In reality the leeward foil contributes somewhat more than half the lift,
but you can see that the windward one is always trying to raise the windward hull.
Leeway coupling has the effect of unloading the windward foil with increasing ride height,
adding a further element of non-linearity.
Since most lift comes from the bottom of the foil, there is no inherent heave stability.
This video gives a graphic illustration of the difficulty involved in sustaining flight on J foils: https://www.youtube.com/watch?feature=youtu.be&v=-Ittw41D-Hk&app=desktop#t=50s
The ultimate solution will undoubtedly be a foil where total lift varies inversely with ride height.
So far these exist in three ‘flavours’:
– L/V type concept with that relies on heave/leeway coupling;
– Control system using surface sensors and flaps;
– Pair of Z foils that work together as a V.
Ideally all the lift should be generated on the leeward side, thus utilising the full beam of the boat to generate maximum righting moment, giving maximum sail carrying power.
We urge anyone contemplating an upgrade to contact us before committing to J foils as these may soon be proven outdated.