Tuning Up: Macy on Rig and Trim Settings

reprinted from the Pre Season 1995 Tank Talk

Tuning the 505 rig has always been a mystery to me. Ten years ago or so we had great speed in the breeze with an Epsilon (stiff mast, short spreader) and a main that was three inches too short on the luff. Five or six years ago we had some speed in fifteen to eighteen knots with a Stratos (stiff sideways; bendy fore and aft; short spreader). Now we have some speed in eight to fifteen knots with a D (bendy sideways; long spreader). At almost all times in between, it seems, we didn't have any speed in any condition. Every time I begin to understand a mainsail/mast combination in one condition I learn about another variable that I either never thought about or had just forgotten. I quickly realized that, for me at least, the 505 is one large imponderable.

Why, for example, can the same North jib work equally well on a bag or a launcher boat? Why does there seem to be no appreciable difference between a long and short luff jib? Why do you depower a Stratos with just rake when it appears that you should depower a D with rake and bend? Why did Taylor/Penfield, Bixby/Lewis and Knapp/Lewis win World Championships in relatively heavy air regattas sheeting inboard and now we think you must sheet outboard in the breeze? Does a boat spin around a gybing board or does the board rotate 2.2 degrees within the hull? Does it matter that the wall thickness in some Ds vary sufficiently so you need spreaders of unequal length to make the mast stand up straight? I simply don't know. I can only think that there are more variables than most of us can see and master.

I have spent ten years trying to achieve good speed in moderate conditions on the theory that most races are sailed in those conditions. Here is our basic set up in moderate conditions for Ethan Bixby sails on a D in a launcher boat:


Rake: 25 feet, eight inches
Tension: about 400 pounds
Mast bend: about 2 inches (measured by eye from gooseneck to hounds)
Main leech tension: tell tale stalled approximately 40% of the time.
Jib leech tension: tell tale stalled approximately 40% of time.
Jib sheet position: 11.5 inches from the intersection of the tank and the floor of a Tuttle to the bearing point of the sheave; 86.5 inches from the aft edge of the transom bar to the bearing point of the sheave.
Spreader height: 3150 mm above the deck.
Spreader angle: about 4.5 inches from aft edge of mast.
Spreader length: 17 inches from wall of mast to bearing point at outboard end of the spreader.
Headstay: 4750 mm above deck.
Hounds: 4990 mm above deck.

On the water we primarily adjust rake and tension to keep the boat balanced. Some of our competitors have suggested that we should start adjusting the mast bend more often.

I started using my current rig in 1990 and by the time we sailed in Santa Cruz in 1992 had adequate, but not good, speed in the breeze. We typically depowered by raking first (and dropping the mast ram to maintain relatively constant mast bend). The following numbers approximate the settings we have used as we depowered:


Rake Tension
25'8" 400 lb.
" 25'6" 650
" 25'4" 700
" 25'2" 825
"
Unlike Howard Hamlin we usually move the jib leads aft about two inches. Although we have not raced in any velocity since the Santa Cruz Worlds, I am beginning to think that we have been sailing with a mast that is straighter than most of our competitors. Several of our knowledgeable competitors with virtually identical rigs mentioned that they could always tell our rig from a distance because we had no mast bend. That fact is interesting when one considers that we are among the quickest in the moderate air and are struggling to stay with the leaders in the breeze. Perhaps the others are too bendy in the moderate air and we're too straight in the breeze.
The author, Macy Nelson, is a three time 505 North American Champion, most recently winning in '93 and '94.