Radio-Controlled Sailboat Racing

CHAPTER TWENTY-TWO

Tuning and Trimming

How you tune and trim your boat may depend a lot on how it was built and what variations your class allows. For example, the snipe class, both full sized and R/C sized, only have a forestay and a port and starboard shroud. Each shroud has a sweptback spreader. The only modifications, to the standing rigging, that you can make to a rig this simple is to move the mast fore and aft or to rake the mast fore and aft. Other classes may be less restrictive in terms of rigging and controls.

In the Chapter 19, "Forces Acting on a Boat," the relationship between the center of effort and the center of lateral resistance were explained. Changing that relationship changes the balance of the boat. Changing the center of effort can be accomplished by moving the mast, raking the mast, or both. Both fore and aft mast movement (location) and rake accomplish the same thing. They just do it in a different way and in different amounts. Moving the mast is a major adjustment because it not only moves the smaller tops of the sails but it moves the larger (more sail area) bottom of the sail as well. Changing the rake of the mast is a finer adjustment because basically only the tops of the sails move. The two adjustments inter-relate. For example, you add rake and it is not enough for today's conditions so you move the mast aft. This combination may be too much so you need to reduce some of the previously added rake. Remember, moving sail area aft moves the center of effort aft and increases weather helm and vice versa. https://snipe.org/ (full-sized snipe) http://www.victor-model.com/products/snipe. Incidentally, the R/C Snipe is not an AMYA recognized class.

What follows is tuning and trimming steps and a discussion of the various options and considerations.

Rig Selection

Which rig you select depends mainly on the wind strength, somewhat on the pond conditions, and on your skill level. Basically, you need to select the correct size rig for today's conditions. The decision is a science and an art and it benefits greatly from a whole lot of experience. But do not let a lack of experience deter you. The wind strength is the biggest factor and you can build your experience with it by regularly recording wind strengths and how each rig performs in both the average wind strength and in the puffs. If you choose a rig for the average wind strength, typically you can tolerate the puffs without losing control. Your wind chart--assuming four rigs--could look like:

You can use MPH, K(Knots)PH, or K(Kilometers)PH.

A sample on-shore checklist is at the end of the chapter. Simply copy it or modify it to meet your needs.

If the pond has high waves, you may need more power to punch through them. This may be a rig-size selection issue. For example, you might power-up a smaller rig to drive through the waves. Your experience is also a factor. If you do not have a lot of heavy air experience you may choose a smaller rig rather than losing control in the puffs. Out of control in heavy air can cause more potential damage to your boat and your competitor's boat because of greater boat speeds and less reaction time.

Some sailors use the boat’s heel angle to determine when to downsize their rig. They may choose thirty degrees or more of heel as an indication to reduce sail. They feel that excessive heel causes the boat to slip sideways. Your experience and your log will help you make future decisions. Beginners can observe the better sailors in the fleet and emulate there rig choice. If you have a good relationship with a good to excellent skipper, ask them for their advice. Another rule of thumb is, if you lose control of your boat going downwind it is time to downsize.

Mast Placement

Some classes do not allow different rig sizes. If your class does not allow additional rigs or you do not own a different rig you can skip the checklist's "rig selection" step and go directly to "mast placement" each day.

As a general rule, you locate the mast mid-range in medium air, more forward in heavy air--to combat increased weather helm--and more aft in light air, to add a little more helm or feel in the helm. Observations of others, experimentation with your boat, your sailing log, and reading related articles all help you to learn about correct mast placement. Articles do not have to be only about your class. Much information can be gleaned from the "hot" skippers in other classes. The Soling 1M, both kit and (RTS), comes stock with a mast step with three locations. The step is placed on the deck so it is called a deck stepped mast.

If your class does allow more than one rig, select the correct rig first, and then determine the correct location for the mast used for that rig. You may have several mast locations for each rig. You may have different locations for the low end, middle, and high end of your C rig. The locations for one rig might overlap or parallel locations for another rig, depending on how the individual sets of sails were cut.

Some builders use aluminum extrusions with many holes that increase the number of mast locations and some builders incorporate a screw thread to offer fine adjustments. For those who love to build new boats or modify existing boats you may want to develop a system to move your mast in finer increments. However, never lose sight of the need to quickly change rigs between races in a regatta.