Ben
We are still in the early development. It will go through more iterations so detail photos are not much point.
The mast has stays but they were not well placed for that test. The revised rig has the leeward stays directly connected to the mast end of the booms so the mast is no longer curved to windward at that point. The rigid vang has now been replaced with wire and is adjustable for length. The mast end of the boom can now slide up or down the mast as does the head of the sail to adjust the angle of cant. We plan to initially set at around 50 degrees with a range between 45 and 65 degrees.
Dean has now fitted the mast to the bigger hull and it is on the windward side. The smaller hull has had some weight cut out and it is now on the lee side. The aim is to get healing moment to cause healing into wind by increasing the cant angle as well as CoE leeward while moving CoG to windward. The mast also has a slight cant to windward to reduce the overhang of the foot of the sail now that it has more cant.
We have tested the rig on land with a bungee for a boom vang and this can be set up to automatically limit sail force by letting the foot of the sail lift thereby increasing the angle of cant in gusts. In the gusts the bows were lifted so the risk is more toward becoming airborne than capsize.
We also aim to test the rig without any sheet/rotation control so rig force always stays in line with the mast, which is nominally near the CLR. This means that steering will control where the sail sits relative to the boat. In this condition it will be impossible to get the sail aback because that condition is unstable - like trying to balance a ball on top of a sphere.
If we find it necessary to have rotational control of the rig then it will be possible to get the rig aback to wind. In this condition the sail drive forces both hulls deeper rather than producing much healing moment. We are aiming to get the sail force vector to act close to the CoG so healing moment is very low irrespective of the sail force.
Slender hulls have quite poor lift to drag when planing so above planing speed there is an advantage in using an efficient sail to provide both drive and lift - sail rocket is probably the best example but same principle with kite boarders. The triangular sail with taught luffs will point higher than a kite while having ability to reef, unlike a rigid wing. I was able to tack through 90 degrees with the model indicating good windward performance.
The same rig could be used on a stabilised monohull (or trimaran) but tacking would involve forcing the rig through the eye of the wind - opposite direction to gibing a conventional rig downwind.
Rick
On 21/03/2013, at 11:20 AM, bjarthur123 wrote:
nice rick!
you have any photos? hard to see the details in the grainy video. i thought i saw stays.
also, what happens if/when caught aback?
ben
Rick Willoughby
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