A Trim Primer for
Main and Headsail Balance

This document is prepared for trimming main + genoa/jib pairs. Except for the general principles, the specific procedures are not applicable to the trim of cat-boats such as Lasers!

The following diagram provides a step-by-step procedure for trimming the headsail and the mainsail taking into account the interaction between the two sails caused by the so called "circular flows" around each sail. In simple terms, the mainsail gives the headsail a "lift" while the headsail gives the mainsail a "header". So, when you adjust one sail, the wind on the other sail is altered. Due to this reason, before the first race starts, you should spend about fifteen minutes to first trim the genoa, then the main, then the genoa again, and then the main again, and so on, until the secondary sail controls (everything except for the controls that you will frequently adjust during the upwind leg - the sheets, the mainsail traveler and the backstay) are set for the current wind conditions.

The diagram below does not consider backstay adjustments that can be used to flatten the sail. The naive presumption is that it is adjusted for the prevailing wind conditions.

The diagram is provided courtesy of SAILING SYSTEMS, Inc.. It shows a yacht on port tack. The diagram is extremely self explanatory. Therefore, I will not provide a verbose explanation. You just need to learn how to read the diagram!

• Only the leeward telltales are shown. They are the only ones that are required to be checked for achieving proper sail trim since a stall is much harder to detect than a luff, and it is the leeward side of the sails that provides the most power and lift!
• The telltales are shown only in their approximate positions! For a full discussion of the ideal telltale locations, consult " Telling Tales", " Truer Tales of Telltales", and " One Man's Fact, Other Man's Fiction".

• Telltale States:
  Shown in green or red (depending on the tack shown) as:
  "stalled" (lifting up); or
  "flying" (straight back); or
  "backwinded" (shaking, drooping).
• Sail-shape Control Lines:
  Defined in purple letters.
  H=Jib Halyard (or jib cunningham)
  J=Jib Sheet
  L=Jib sheet lead (car)
  C=Main cunningham
  T=Mainsheet traveler car
  M=Mainsheet
  O=Main outhaul
• Trim Adjustment Directions:
  Adjustments to the controls are noted in black "action cirles".
  If an action circle involves multiple adjustments, they are undertaken in sequence, top to bottom, with the bottom adjustment light.
  Adjustment directions are shown with arrows with respect to the the control axis of each control.
  EXAMPLE: "H" goes up or down; "T" goes up (to widward) or down (to leeward); "O" goes right (in) or left (out), etc.

• Execution Sequence:
  Shown as light gray numbers ( i ), inside light gray, rounded-corner boxes.
  The action(s) noted within the box is (are) taken as the ( i )th step(s).
• Trim Adjustment Criterion:
  Shown by one or a pair of black lines originating from an action circle.
  The adjustment noted in the action circle is to be undertaken if the telltales (like those) the black lines point to are in the state depicted.

Furthermore, whenever a pair of telltales are shown as the "adjustment criterion", the criterion refers to all telltales with the location characteristics of the telltales shown as the "adjustment criterion". For instance, the adjustments required in Steps 10 & 14 ("O","C","T") refer to the case where "telltales forward on the main are flying but telltales on the main leech are stalled". They don't refer to telltales specifically at the shown locations!

Note that initial genoa adjustments involve Steps 1-4. Next, the main adjustments involve Steps 5-15. Then, you go back to the genoa with Steps 16-19. When you come back to the main again, you start with Step 20 and continue. (That is, you don't center the traveler to start the adjustments again as you did in the first round in Step 5.)

Let me do you a favor and start you on the explanation of the diagram so that you can have an idea about how precise you need to be:

• Step 1: Start sailing with your leeward-side steering telltales (the Gentry tufts) all flying. You are now at the verge of luffing.
• Step 2: While you are preserving this state in your Gentry tufts, have a crew member look up and check if the "jib-lead-check" tuft high up and right along the luff on the leeward side is stalling. If you are still steering correctly, at this time the tuft right along the luff at the level of the Gentry tufts (or the lead tuft of the gentry tuft system itself) will still be streaming straight aft. If so, then the jib lead car needs to move back a bit, and vice versa. That is, if the top leeward tuft is not stalling but the windward one is showing the signs of a luff, then the jib-sheet lead needs to come forward. (See an opposing view on how to adjust the lead in One Man's Fact, Other Man's Fiction.)
• ....