On The Water
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Last update, February 5, 2002


Just for fun...archived.




It is exciting to take a new boat to the water. There is so much anticipation and hope. Hope? Yes, there is always this fear that it will not work. Be assured it will work. It may not meet all your expectations the first day, but it will work and it will sail and function well. If the boat meets all your expectations on this outing, you will be with the less than 10% range of people in the same effort. So, lighten up and have a good attitude, you might get lucky, and the best is that you are outdoors. There is a reason this is called a "Shakedown Cruise" by shipbuilders. As remote control modelers, you have it made; you could be throttling up an airplane you spent six months building.


If you have a choice, pick a day when the winds are light. It is easier on you and the boat. Take your lakeside gear and another box of building stuff from the shop as additional this first day. Make sure the batteries are topped. Do you have your boots? If you have a friend that is into this stuff, get him to come along.


If you know nothing else, rig the boat as you did in the pre-tune. Rigging will go faster as the settings should not have changed. The main concentration today is to sail with the sails full, no luffing, then deal with balance. If you can accomplish this you will have the rest of the summer to have fun and learn more. Slip the boat in the water with the sails out hauled and study the track quickly before the wind takes effect. If the rudder is off, it will not be by much. Make a slight adjustment in the trim and go for it. Bring the sails in and watch her power up but not to tight. It is recommended, having pre-tuned with the main close to the centerline, that you sail one or two bumps out on the control stick. Tight is for other reasons. Let her breathe a bit. Control the sailing. Make it go where you want it. Cruise and get a feel. Here is what you are looking for as mental notes:

  • Note any change that is needed in the rudder for correct centering without TX trim.

  • How does she track? With your thumb off the rudder, does she round up or drift up into the wind?

  • Does the boat track the same on both tacks?

  • Control the boat with the rudder on a tack and slowly bring the boat up to the eye of the wind. Watch the jib carefully. You want to see the jib start to luff before the main; a slight waving would be great. Fall off just a bit and see if it quits.

Play with this till you have a good feel for consistency. Does the boat do the same thing each time? These are the four key things to concentrate on at first. Here is some information on these items:

  1. Rudder: Easy. Center the trim and adjust the rudder.

  2. As this is being written, there is no way to know the velocity of the wind. However, as a boat heels it will try to come up into the wind to right itself. we can counter this in two ways, rudder and balance. The use of rudder to correct this problem is not good for it produces drag. Balance can be controlled by moving the mast on the step. This is the simple explanation and we will get deeper into this later in Tuning. The rule is that as the wind increases, move forward and as it decreases, move aft. A heeling boat will come up into the wind but we would like for it to do so slowly, maybe five or six boat lengths before the sails luff. If this were the case then very light rudder pressure would be all that is needed to hold the boat on track. This is acceptable. Remember, while playing with this idea on the water, do not sheet in tight. Let her breathe.

  3. Opposite tacks, opposite reactions: This is balance also but side to side. It means that very likely the mast, or a portion of it, is off center. Thinking about item 2 above, one side will heel more than the other just by being off center. Ergo, she will head up more on one side. Roll the boat over in the cradle and...you know the drill.

  4. The jib is your beacon. It is a huge tell tale. If you learn to sail by the jib, you will sail fast and earlier than others. The jib is more loose in the rigging than the main. We have offset it to the main. The jib will point up into the wind faster. The jib generally has more twist. All these things points to the jib running on the edge of the envelope. This is delicate business and a thin line as the boat points up. You want the jib to luff first. The main is brute power but when it luffs it is a giant speed brake. You want to know that is about to happen so you can fall off a bit. A thoughtful tuner will spend more time on the jib than the main. It is your star and the path to follow.

    • If the main luffs before the jib, your dead and buried.

    • If they luff together, you might live because you can react to that but you were slow to start with.

    • If the jib fully luffs, with no hint that it is coming, trim it in a bit and see it that helps. The next time you bring it in take a good look to see if maybe it is a bit loose. The jib should run with the offset discussed before and may have more depth or twist in the sail than needed.

    • There is another kind of luff in the jib. That is the knuckling, or flutter, of the luff along the jibstay. Generally, this will not be violent like the luffing of the draft or the leech but a dip or sag in the sail causing a break in the smoothness of the camber. This is an indication that the backstay tension needs to be increased. Higher BST will bolster the jibstay and lessen the entry angle. What has happened is that the wind pressure has exceeded the sailmaker's design cut of the luff. Somewhere in this website you have heard of the Jib Luff Allowance (JLA). Well, you have just seen it on the water.

If you can get control of these things you will do well. When you have time to think, or maybe at another session on the water, monitor the mainsail. There are some things that you can see well as a beginning captain. One is the luffing of the upper part of the main at the class designating numbers. This is the area of "twist." This luffing may mean it is twisted off too much. Tighten the vang a half turn and see what happens.


Second is a knuckle just behind the mast in the center of the sail. This will be a break in the smoothness of the camber. It is just like the JLA above but is called Main Luff Allowance (MLA). However, before you jump to conclusions and you are still on the water, trim out the jib a bit and see if it goes away. If it does go away then we say the jib was back winding the mainsail. This means the jib was in far enough to send a stream of air through the slot onto the surface of the mainsail. The slot between them needs to be open enough to allow a parallel flow across the main. The size of the slot and the twist of the jib to match the leech of the main will give you the flow desired. This will change with wind velocity but is the general idea.


If this was not the reason for the knuckle in the main then put a bit more bend into the mast. This will bow the mast forward in the area of the knuckle and flatten the main a bit. If the sailmaker's cut of the main luff (MLA) matches the bend of the mast, all will be well.


It should be noted that the jib and main luff allowances are very small measurements and made on a small sail. It cannot be expected that the intentions of the sailmaker will be perfect after you start screwing around with the rig. If you do not like taking notes, make a mental note where a sail wishes to live and work as opposed to what some chart says. Tuning by the numbers is a good way to start leaning but then it is like the front end alignment of your car, you have to make adjustments at times.


In another section and at a later time, other aspects of what you see on the water and what you do will be explored. Those mentioned here are the main issues and that, when on a beat to weather. You will spend at least 80% of your sailing this way and about as much tactical thinking during that time. You cannot win a race downwind till you conquer the beat.


Anyway, work with your boat and get it to run free with an easy touch on the helm. You will learn a lot in the process. Enjoy your boat; it was a good cruise; thanks for coming along. Enjoy the people and this is a nice way to spend a sunny afternoon by the lake.


Trim Angle, Balance, Righting Moment, Inertia

Think About It