Mainsheet boom hanger(s)

My boat originally had a 5:1 mainsheet block system (with two boom block hangers) and had been setup with very little rake in the mast. Since then I have upgraded to a 6:1 and raked the mast back so the mainsheet blocks come within 2". I am using the forward mainsheet block hanger on the boom, but I wonder if I should move the block hanger even more forward.

Currently when I am going upwind and have the main traveler almost centered and the mainsheet blocks tight, the boom's block hanger is aft of the main traveler. Raking the mast has created this situation since the gooseneck is now more aft and the distance between the boom and main traveler has been considerably reduced (which has resulted in alot more forward thrust on the boom from the mainsheet). This forces the boom's gooseneck up against the mast and pushes the mast to rotate so the mast base is jambed up against the stops of the mast step. Should the mast be that much rotated when going upwind?

What should be the ideal orientation of the mast when heading upwind, fully rotated or in-line with the boom? If minimal mast rotation is optimal when heading upwind, then I will have to move the boom's block hanger more forward so that the mainsheet is only pulling the boom down and not also forward. Also, what currently is the distance that the boom's block hanger should be from the gooseneck on new boats?

_________________
Tim
84 H16
82 H16
87 H14T
Tortola Sails: 115222
Blue Prism Sails: 88863
Clearwater, FL

IIRC, the current (single) boom bail is positioned 1 3/4" aft of the forward bail location of the older booms. I measured it once on a new boat. Jim Sohn also pointed out that the bail is riveted "higher" on the boom now, to allow for even closer sheeting. I always sailed with my 6:1 on the rear bail for as much forward pressure as possible, ensuring full mast rotation.

I was going to remove one and position the other in the new location but stumbled upon a newer boat this season. If I think about it, I'll drag out the new and old booms and measure this weekend.

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sailflatlands at gmail dot com

When going up wind sail with the traveler out a few inches so the boom, and more importantly, the leech of the main is straight fore and aft and not "hooked" inward. Even with the the boom parallel with the side rails you can still hook the leech by applying too much main sheet tension, which is like throwing up a parachute, i.e. SLOW.

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Sheet In...Max Out
www.fleet297.org
sailflatlands at gmail dot com

Sorry Tim, not to hyjack this thread, but since this subject has come up, I picked up a used boom and doesn't have ANY hangers on it, I was wondering if anybody out there have 1 or 2 hangers laying around that they can sell me? Greatly appreciate it, thanks, Jim.

Block hangers are a common stock item from Ronstan and others at West Marine and go for only a couple bucks.

As for location...at least on the older boats the hanger needs to be pretty well centered over the rear beam. If there is much fore or aft tension on the older travelers they just don't travel very well. The forward hanger works better. I asked this question last year and was told the block hanger on new boats was at 81 1/2 inches on the boom as I recall. Maybe one of the Hobie experts can check that.

Thanks, I didn't even think of West Marine. Tim, you can have your thread back, thanks!

When sailing upwind, is there an advantage to having the mast fully rotated?

_________________
Tim
84 H16
82 H16
87 H14T
Tortola Sails: 115222
Blue Prism Sails: 88863
Clearwater, FL

Not sure what you mean - the mast should always be rotated against the stops going upwind - there's no intermediate setting on a Hobie 16.

When the main traveler is close to center and the mainsheet is cranked in, it forces the boom's gooseneck forward and makes the mast rotate against the stop, even in light wind. If the mainsheet only pulled the boom down instead of both down and forward, then the mast would only rotate if the wind made it do so.

_________________
Tim
84 H16
82 H16
87 H14T
Tortola Sails: 115222
Blue Prism Sails: 88863
Clearwater, FL

_________________
Raise your sail one foot, and you get ten feet of wind.
起你的一只帆，和你10英尺的。 -- Chinese Proverb
William D. Latinette @ Latrobe, PA, USA w. H14 Turbo X 2... [email protected]

The mast should be rotated against the stops all the time sailing upwind - in all wind conditions.

In lighter air, the mainsheet tension - when the mainsheet is angled aft a bit - is the only thing that will keep the mast from slamming - unrotating a bit, then slamming against the stops every time you go over a wave. Slamming will wear down the stops quickly.

On the last boat I had with double boom hangers and a low-profile system, I'd use the forward one in heavy air (more down; less forward) and the rear one (more forward; less down) in light air.

I just read an article on "Rotating Masts" by John Courter of the Washington Yacht Club in "The Telltale". He indicated the following:

"Most beach catamarans have rotating masts. Rotating masts improve performance by reducing turbulence on the mainsail. They can also be used to control how much power is available from the mainsail."

"The Hobie 16 has stops built into the mast step to limit the rotation of the mast and therefore the amount of rotation is fixed. The Hobie 21 and the sx18 have a U shaped bar sticking out behind the mast just above the boom. The end of the bar has a line that runs to a cleat on the boom. How much line is let out determines how much the mast is allowed to rotate. With both systems the mast automatically rotates to the same setting on the other tack after a tack or jibe. This assumes that when you tack you ease the mainsheet as you normally would, as it is possible hold the mast rotated the wrong way if the mainsheet is left tight. (Usually the blocks on the boom for the mainsheet are mounted slightly aft to push the boom forward to facilitate rotating the mast.)"

"Masts that do not rotate have an area of disturbed air behind them which causes the mainsail near the mast to not be effective in generating lift. A mast that can be rotated is allowed to rotate until the leeward side of the mast continues the smooth curve of the sail eliminating the disturbed air on the leeward side. There is still disturbed air on the windward side of the mainsail but this increase in disturbed air on the windward side is not nearly as much a loss in lift as the gains made by cleaning up the air flow on the leeward side."

"Typically a good starting point for setting the rotation of the mast with an adjustable rotator for upwind sailing is to point the rotator bar at the shroud when the sail is sheeted in. If you have the sail set with a deeper camber for more power you would allow the mast to rotate more, for a flatter sail a little less. Check it by lying down on the tramp face up and sight up the mast on the leeward side."

"The Hobie 16 with its fixed stops is only set correctly for one point of sail. Class rules allow you to file the stops down to alter what fixed point you believe is best."

"An additional adjustment one can make with an adjustable rotating mast is to de-power the mainsail. These masts are long in fore-aft plane and narrow side to side. With the rotation set to the minimum to look like part of the sail, the orientation of the mast is to have mostly the long dimension in line with the sail, and therefore the loads on the mast trying to bend it in the plane in which it is stiffest. This results in little bend, keeping the sail fuller and more powerful. If you allow the mast to rotate 90 degrees relative to the sail, to put the narrow dimension of the mast in line with the loads, the mast will bend and flatten the sail, de-powering it."

Based on his description, I would think you would want to keep the mast rotation in line with the mainsail when sailing upwind so the leeward side of the mast continues the smooth curve of the sail eliminating the disturbed air on the leeward side and also to reduce the bending of the mast which would flatten the sail and de-power it.

_________________
Tim
84 H16
82 H16
87 H14T
Tortola Sails: 115222
Blue Prism Sails: 88863
Clearwater, FL

Tim,

This is a good read for understanding rotation BUT, you can keep the H16 mast in only one position, fully rotated. Your only "adjustment" to this is filing the stops for more rotation, which I would recommend NOT doing.

The H16 mast rotation is not adjustable

Hobie 16's been around for 39 years. Might be one or two out there with one of these

"Mast Rotation Control Arm"
get yourself one and depower to your hearts content

FYI...when racing the H18 and H20 on upwind/downwind courses we only used the mast rotation control arm as a source of depowering as a last resort.

_________________
Sheet In...Max Out
www.fleet297.org
sailflatlands at gmail dot com