Self tending jib sheet?

[GreenLake]

You always want to balance jib and main with the CB and rudder, and usually you speak about the boat (or the helm) being balanced. Therefore, if you call out the balanced feature of a jib, that most definitely would seem to refer to some other feature. In this case, the fact that the jib pivots around a point aft of the tack, which balances the sideways force on the jib. As Jdoorly writes, this is in perfect analogy to a balanced rudder blade.

In higher winds, this could be interesting (or if your crew is rather lightly built or very young). However, if you pick the right moment to pull the jib across and cleat in the jib sheet before the jib has filled, then you don't have to "fight it". If I sail with a young and eager crew and they don't manage that trick, then I just luff up a bit to unload the jib as needed so that they can adjust the trim.

All this, of course, is part of my general skepticism towards this feature - but, as I've never sailed a boat that had a self-tending jib, I may simply not know what I'm talking about

[PassingWind]

PassingWind, you are correct about reducing weather helm for sure, but tell me this: Why do they say a rudder is 'balanced' when its center of axis is moved (up to 1/3 the way) aft of its leading edge? And, in the same way a junk rig is 'balanced' because a portion of the mainsail is forward of the mast with the larger portion aft of it. Of course there is a balance between sails as well, and a balance between sails and hull forces. And, so it goes...

I agree with your rudder analogy and understand the theory of the balancing effect, but Hoyt claims the the load on the mainsheet is only reduced by 20%(about 20% of the main is in front of the mast) on his junk type rig, so i would assume he applied similar principles to his balanced jib product. Which also coincides with the theory of a balanced rudder 15-20% of the rudder is in front of the pivot point. Which doesnt mean you have power steering, on 30' plus sailboats there can be quite a bit of force on the helm even though its a balanced rudder.

But i would disagree with you when say you dont need much muscle to pull it in cause its balanced, you still have 80% of the load to pull in. I really dont think the "feature" of the design was to get a 20% reduction in force on jib sheets i think that was a small by product of the design.

I personal think the best part of the design is that it reduces weather helm and also increasing your sail area by allowing a larger jib(genoa). i also recognize that it creates a benefit of reducing the load on the sheets by roughly 20%.

When you sail for a week straight(or a few hours for some weekenders) the effects of weather helm become fatiguing to the captain after awhile. Sheeting in the jib can be done before the tack is complete, therefore there is practically no load at all on the sheets

[PassingWind]

since none of us have first hand knowledge of this rig setup i resorted to looking at the directions.... Here is hoyts explanation

Advantages of the Patented Balanced Hoyt Jib Boom

The principal advantage of the Patented Hoyt Jib Boom (HJB - now in use on over 1000 yachts) is that it does for the jib what the boom vang does for the main - namely maintains leech tension as the jib is eased out offwind. So instead of having the jib just twist off and lose power, the HJB keeps full power on for reaching and running. In this new refinement, the HJB extends forward, as well as aft of the pivot point, thus in effect becoming a kind of spinnaker pole as well as a jib boom, since it allows a larger jib, and enables that larger jib to project out to windward as the jib sheet is eased for offwind trim. So instead of having to go forward to set a whisker pole or spinnaker pole (which is difficult if not impossible for a single-handed skipper) the HJB allows a seated skipper to gain windward projection of a larger jib - just by easing the jib boom sheet line. This results in the fullest projection of jib area, which is necessary for downwind speed, with the further advantage of reducing the increased weather helm that normally accompanies easing the main sheet.
Evolution of the Patented Hoyt Jib Boom

The following illustration shows how the HJB delivers significant performance improvement over traditional jibs. The new, balanced HJB continues this trend by increasing downwind performance and reducing weather helm. The parallel here is the same benefit for the jib that a balanced rudder offers for steering.

[GreenLake]

If force goes like area, then "balancing" a rudder at 20% would effectively remove 2*20% of the rudder from contributing, as the forward 20% cancel out the contribution from the next 20%. (In other words 40% of the rudder are balanced). The remaining 60% have a 28% shorter lever arm, so the total effect is much more than 20%... In an actual rudder, the contributions may not be linear with area, that is, the effective force on an unbalanced rudder may not be one that's acting on the centerline, but, for example further forward. (I'm almost sure I used to know where a typical rudder profile generates its force, but can't be sure I remember it correctly. But you get my point)

Therefore, the reason the jib boom is called "balanced" is indeed for the analogy to a balanced rudder.

I had not considered the effect of having the tack to windward for a broad reach - that could indeed make a difference (for downwind, at some point, one would want to have the jib poled out entirely to windward, and that would require some additional line - same as for heaving to).

Balancing the helm is a useful thing - but I find the helm of my DS rather well balanced as it is. You do want a small amount of weather helm, that has all sorts of positive effects (and I'm sure some people here could enumerate them). The point where I see strong weather helm with my DS is where I would put in a reef in the main - especially for pure daysailing, so not the time where I would need extra area in the jib.

If you have strong weather helm with standard sails on your DS, there may be some other factor, perhaps mast rake, worth looking into.

[PassingWind]

If force goes like area, then "balancing" a rudder at 20% would effectively remove 2*20% of the rudder from contributing, as the forward 20% cancel out the contribution from the next 20%. (In other words 40% of the rudder are balanced). The remaining 60% have a 28% shorter lever arm, so the total effect is much more than 20%... In an actual rudder, the contributions may not be linear with area, that is, the effective force on an unbalanced rudder may not be one that's acting on the centerline, but, for example further forward. (I'm almost sure I used to know where a typical rudder profile generates its force, but can't be sure I remember it correctly. But you get

If you have strong weather helm with standard sails on your DS, there may be some other factor, perhaps mast rake, worth looking into.

As far as percentages you would need to take that up with garry hoyt as he states that his junk type rig which is comparable to the balanced jib design only yelds a 20% reduction in force. You can apply all the math you want but that figure is from the designer himself.

Not sure who has issues with weather helm on a ds but if you were to install a system like the balance jib(which is overkill on a ds) with a much larger sail weather helm would be a problem if the sail was not offset.

[GreenLake]

I checked out the info for the Balanced HJB but didn't see any definite percentages, but for the Hoyt Offset Rig, which is what you call the balanced junk rig, he writes:

Reduced sheeting loads due to the balance effect of carrying 20% of the sail area ahead of the mast pivot point

This doesn't say how much the reduction in force is, but gives the 20% figure for the sail area.

I couldn't find any estimate in percentages of force on his site, but I'm rather confident that the actual reduction will turn out larger than the percentage of sail area carried forward of the mast. In particular, the discussion on some other sailing sites points to a center of pressure as far forward as 25% of chord length. That would mean that 20% of area forward of the pivot would result in a nearly balanced foil.

I also need to admit that I didn't appreciate right away the self-jibing feature of the jib boom. So, once the jib wants to come over if you are going DDW, you end up projecting 80% (not 20%) of the jib. I would like to find out how difficult it would be to keep the jib in that wing-on-wing setting. With a manually attached whisker pole there's a tendency to fix the jib on one side, which might be beneficial in allowing it to stay set in wing-on-wing even in the presence of small disturbances (wakes), but might also lead to brief backwinding. Hoyt's designs are all intriguing and I would love to try some of them (without first having to alter my DS ).

Thanks for bringing these to our attention.