J/30 Class Association Forums J/30 Forum One Design Class Rules Mast Step Postion

Any chance that someone who has set things up correctly could post some pics - partners and step? If so, would greatly appreciate it.

thanks! - Jeff

Guys

Don't for get also to set the Stem to front of Mast to Max 11" 6" +/_ 1/2" This will give you max rake

On the back stay leave it as loose as you can but still allow you to depower the rig when the breeze is on But when you are going down wind you want to allow the top of the mast to go as far forward as possible

OK ... Am in process of setting the mast step on #505.

If I remember correctly Bill said 25mm from FRONT surface of mast to a extended vertical line at fiberglass step.

This actually puts the step even further forward than this photo from last year.

Vic - here is the class rule for reference. I added the emphasis on the applicable area. This will help you get the rig in the correct position so everything supports OD sails and tuning.

5.7.3 Position of the mast shall be fixed at the deck 3505 mm plus or minus 13 mm from stemhead tip to the front edge of the mast. And it shall be permanently fixed to an immovable mast step so that the forward edge of the mast is not less than 25 mm aft of the forward vertical face of the molded step in the sole liner.

Vic-you are 9/16" too far aft with your step. That is HUGE! If you move the step forward to the 1" mark as per class rules, the point of headstay attachment on the mast (i.e. the hounds) will move almost 5" aft. This will add rake (obviously) but will also decrease prebend, decrease headstay sag, and will generally help your light air performance. Also-all the standard rig tune settings are calibrated to having the step in the right position. So the rig tune settings you have been using up to this point probably have been way off.

That's what I'm hoping.

Brian ... skipper of J30 Hornet and my winter tactician last winter was seriously upset with the performance of the boat. He is itching to do a complete re adjust when he gets here in a couple of weeks.

But this all started back in 1985 when I decided that I would not be racing all that much and Don Kidd of Pirate Cove asked a simple question: Do you want to race or comfy cruise with roller furling, slides in main ... etc. and mostly not in sheltered Narragansett Bay but off Beavertail?

Yesterday, they managed to get the mast base off with minimal problems ... the bolts were corroded and had a slight bend. Threads in step appear clean.
The slots in the base appear to be just maxed out for the OD measurement and that's where we will lock it down tomorrow.

Reading the posts, some things I don't understand. They are:
"If you move the step forward to the 1" mark as per class rules, the point of headstay attachment on the mast (i.e. the hounds) will move almost 5" aft."-- How is this possible, if (geometrically speaking) the amount of movement of the headstay in the fore and aft direction is fixed by the headstay length, and the length of the mast from the headstay point to the bottom of the mast? I do agree that moving the butt forward will reduce prebend, and also reduce headstay sag, HOWEVER, since our boats are underpowered anyway, why is it important to reduce headstay sag? More sag = more power and higher pointing ability and speed to windward. My experience has been that the setting of the mast butt, (which sets the prebend of the mast) should be based upon the luff curve set in the mainsail, such that the chord depth is controllable in all conditions. In classes such as the Etchells 22 and J-24, the prebend is adjusted (but not universally agreed upon within each class) based upon wind strength. I am not going to re enter the discussion of standard rig settings because they are WAY too tight.

Art Ahrens

On Vee Jay our most serious concern is headstay sag.
The heavy foil for the Harken RF foil in a 3+ ft wave can wipsaw back and forth ... and while the foil segment connections on the current foil appear to be way better than the old foil using pins ... I am shy as to just how much wipsaw effect i want to have ... you have to see floppy foil action to believe it.

to gain reasonable tension I have shortened the forestay length ~3.5 inches ... which of course makes the OD jenny length too long. We still get some wipsaw action ...

but this move on the Vee Jays part is to one get two boats as close in specs as possible and to try to get to maximum OD headstay length ...

other than that ... other people need to come into this conversation to talk the theory with the idea of course that a carbon foil probably weighs a tenth of the aluminium RF foil.

If the fulcrum is at the deck, then the tip can move 5" for a small change at the base. However, if the pivot point is at the headstay, then the tip would move less than the base.

I'm with you, think the mast would be pivoting around the headstay, not the deck.

Ah ha. I understand. Concern with respect to the head foil can be an issue. Didn't have that worry on a J-24. I have roller furling (Pro Furl) on Nice Pear, and have not seen any issues. HOWEVER, it does raise some fodder for discussion with respect to the hank on jib discussion. In light air, on the J-24, (and it seems to work on the 30), the more headstay sag the better. Does this give the boat with the wire headstay an advantage?