Boom kickers and rigid vangs effect on twist

[Bayard Gross]

In examining the fashion in which a Boom Kicker and or a ridgid vang are attached to the boom and then to the mast, I draw the impression that these devices may have noticeable effect upon the twisting of the boom and therfore the amount of twist that one may apply to a main sail.Basically, a boom kicker has a pin through a slot and a rigid vang has a pin through an eye both rigidly attached to the boom and then ridgidly to the mast. As the boom twists its turning motion would seem to be arrested by these devices, although in the case of a boom kicker with its flexible tubes less so than a ridgid vang.This seems to be true to me as when compared to a normal boom vang which is attached to the boom and mast with bails that should allow full twisting motion of the boom when the vang is loose, but arrest it when the vang it tightened.Thus, is it true that thses devices effect twist in the boom and mainsail? In the case of a ridgid vang it appears that when it is loose, the boom could not twist as much as if it were a normal vang with bails. And for the boom kicker, the normal vang with bails used with it, also would produce less twist when loose than if there were no boom kicker.

 

[Trevor - SailboatOwners.com]

Twist - boom twist vs. mainsail twist

Hi Bayard -Typically, when we discuss sail trim, we are speaking of sail twist, not boom twist. I'm not sure I understand your post, quote:"these devices may have noticeable effect upon the twisting of the boom and therfore the amount of twist that one may apply to a main sail."The twist of the actual boom as a result of a standard topping lift doesn't affect the "twist" of the mainsail, as is usually described in sail trim texts or dialogue. Rigid vangs have the advantage of controlling twist better than a standard block and tackle stup in that the controls are easier to manage (along with the additional advantage of removing the topping lift). However, it is common for the entire boom to "twist" to one side if the topping lift supports the boom from the pulley at the end of the boom center and an eye or cleat at one side of the support. Even if the boom is slightly "twisted" at the end, it has little effect on the oft-discussed "twist in the mainsail". Please correct me if I am misinterpreting your inquiry. I have little experience with a boom-kicker, but I've seen them used on all sizes of boats.Trevor

 

[Steve O.]

rotation?

Are you speaking of a boom that rotates on it's gooseneck? That's a very different thing from mainsail twist. In that case you are right, the rigid vang would inhibit the rotation of the boom. However, very few boats that are large enough to need a rigid vang have booms that rotate--at least none that I have seen. Perhaps that type of boom is specific to racing boats?

 

[Tom]

Boom Twist?

Have used a rigid vang for years. It has no effect on the ability of the boom movement from side to side.Down wind it gives much better control to keep the boom from sking in gust.Upwind in heavy air the rigid vang will allow one to vang sheet much better than its soft counter part. In light air the rigid will support the weight of the boom on all points.Have never used a boom kicker.

 

[Bayard Gross]

Thank you for your replies

I now understand I had a misconception about mainsail twist and the “twisting” or turning of the boom.This particular misconception arose from my spending time of two different boats with two different gooseneck set-ups.The first boat is my own C-22, a 1982 model constructed in 1981 onto which I installed a boom kicker, purely a convenience item for single handling. The gooseneck on this vessel barely permits any “twist” or turning in the boom.The other vessel is a 1981 thirty foot Seidlemann (?) 30T. The gooseneck fitting here allows the boom to rotate as if it were a “furling” boom although with the fixed eyestrap for the main sheet attachment it cannot fully rotate.Nevertheless, the other day while sailing on the thirty footer with a reefed main and no boom vang attached, I noticed the boom “twist” or turn very sharply. As this vessel does not have a boom kicker or a rigid vang while mine does have a boom kicker, I wrongfully assumed that it was the boom kicker on my boat that prevented its boom from turning as greatly as it did on the thirty footer. Actually, now I realize that it is the difference in the gooseneck setups.Nevertheless, I truly appreciate your responses as I also realize now that sail twist has little, if anything, to do with main sail twist, a poor understanding on my part. I apologize for not being bright enough to have figured out the difference in the goosenecks earlier, but I guess that’s what these forums are all about.