What are the benefits of a self tacking jib?

Technical discussion of ARC products
Bill Roberts
Expert
Posts: 515
Joined: November 17th, 2003, 9:13 pm
Location: Stuart, Florida

Re: What are the benefits of a self tacking jib?

Post by Bill Roberts »

Mac,
The Aquarius curved jib track, curved more outboard, straight in the central area, will encourage the jib to run further outboard when tacking downwind "without spin". With spin the jib is always trimmed closer to center. It is like sailing to windward with a slight ease. Just trim the jib to the tell tales and everything will be fine on all pointa of sail. With spin, the curved jibtrack isn't necessary because the jib is never very far off center. It is not that one is better than the other. With spin you don't need the curved track. So, the whole beach cat world, newer boats with spins, don't know what in the hell they are doing with curved jib tracks. It, the curve, is useless and requires an additional jib car control line to set the position of the car along the fulley curved track. The jib car position changes with wind strength and point of sail; something else for the crew to do if the crew knows what to do. The straight track, or Aquarius curved jib track with a straight central area, does all of this for you automatically. The car even moves out slightly with puffs and back in after the puff passes. In a puff the relative wind clocks to windward slightly and the slot, jib to main, needs to be wider for the higher velocity airflow. The SC/Aquarius self tacking jib system does all of this for you automatically. Non of the other fully curved jib tracks do this. Why won't the beach cat sailing public buy boats built by Aquarius??????????
Eric2101
Professional
Posts: 205
Joined: August 16th, 2004, 5:42 am
Boat Make/Model: Supercat 15
Location: Davie, FL.

Re: What are the benefits of a self tacking jib?

Post by Eric2101 »

to me... this is the key to the straight self tacker....


With the straight jib track as the jib sheet tension changes both the jib car position changes and angle of attack of the wind on the sail changes in a perfectly coordinated way, sail shape and angle of attack. With the straight track there is a (delta sheet tension/delta angle of attack term) with a real value, real ratio, that can be both positive and negative. The 4:1 pulley system makes the jib sail shape and wind angle of attack on the jib dance together in harmony. With the curved track, Tornado style, this term is zero and a second jib system control line is required. Calculus can do nice things can't it.


math can not tell lies

Mini Me
Eric Arbogast
Supercat 15
Bill Roberts
Expert
Posts: 515
Joined: November 17th, 2003, 9:13 pm
Location: Stuart, Florida

Re: What are the benefits of a self tacking jib?

Post by Bill Roberts »

Right Eric,
Marstrom and the Tornado crowd saw the self tacking jib on a 22 that was sold in France several years ago. The boat was not rigged when they saw it in the rain and they did not see the 4:1 between the traveller car and the jib clew. They ran home and tried it on a Tornado with 1:1. When they sheeted the jib in and got the sail shape they wanted, the jib car was right in front of the mast. Uh,Oo, it doesn't work. The calculus went right by them. Their solution was the curved jib track. The radius of the jib track curve is the shortest distance from main beam center to the forestay. The jib clew swings on a parallel arc. Therefore connecting the two there is no change in jib sheeting tension as the jib car moves along this jib track arc. So, a second jib car positioning control line is required, two controlls on one jib sheeting position. That became Tornado production. The the rest of the beach cat world saw the Tornado scheme and copied it. They have the complicated scheme and ARC and RC have the simple system that works better.

Bill
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