Tuning Guides and Speed

How Sails Work

On every sail angle, except for a run, a boat is being pulled forward by lift
In order to maximize lift/thrust and minimize drag- you must create an optimal balance between your air foils(sails) and your water foils(centerboard and rudder)
Flow is the stream of fluid over your foils
the more constant and faster the flow is over all foils, the faster the boat will go


The Slot


When trimmed properly, the combined effort of the main and the jib help to create more forward thrust and higher pointing angle on the upwind, this comes from slot size
over trimmed jib means smaller (closed) slot, higher pointing angle, and slower speed
under trimmed jib means larger (more open) slot, lower pointing angle, and higher speed


Points of Sail
Close Hauled
Close Reach
Beam Reach
Broad Reach
There are no rows in this table


Main Halyard

controls main sail height
main sail should always be all the way up
It is easy for the halyard to slip after other controls are put on especially in breeze, always good to pull on halyard after launching

Jib Halyard/Tension

controls jib height
controls jib draft, as tension is put on it flattens out and pulls the draft forward
controls mast position, as tension comes on the mast angles forward which lowers the wind’s Angle of Attack on the main and shrinks the slot
All wind conditions:
1 inch of dangle- to determine this, sail on a close hauled course, sails trimmed in all the way, tension should fall out of the leeward shroud, the diameter of the circle it makes should be 1 inch
Dangle will change as the wind goes up, as the wind increases the main will get more pressure which stretches the windward shroud more

Main Sheet

controls angle of the main sail
when close hauled there are two sections of trimming:
1) Pulling the boom toward center line
2) At a certain point, you begin to pull the boom down (vang like) rather than in and the main begins to stretch
0-3 knots
never want to enter section 2, pull the boom down will affect sail shape and stall the main
4-12 knots
coming out a maneuver, be in section 1 until full speed, at full speed enter section 2 and point up slightly
once speed starts to reduce, bow down and go back to section 1 to get speed back
13+ knots
in hiking conditions. as the puff hits it is important to ease the main before the boat heels to leeward so the boat does not slide sideways, as soon as the boat is balanced inside the puff (generally less than 3 seconds) trim back in
FJs like for the boat to be balanced above all else, as few main changes as possible, even if it means the boat is slightly heeled over, the stiller the boat, the faster it will go
Since 420s have more of the boat in the water there is more traction, this allows for the main to be played constantly- if fully trimmed, slightly ease every few seconds to let the leech breathe. When overpowered ease quickly and trim constantly while keeping the boat flat, think of the main as an accelerator that you are constantly pushing in and releasing to maintain constant speed

Jib Lead Block Position

Default is 3 holes (from back) showing
As soon as you have to ease the main to keep the boat flat go to 2 holes showing
this is because when you ease the main it closes the slot, by shifting the leads back the jib sheets pull in the bottom of the sail more and open the leech, opening the slot
When the main cannot be trimmed all the way without heel go to 1 hole showing

Jib Sheets

For our t420s follow FJ rules
in the other collegiate 420s with cleats on the deck, you cannot over trim the jib
In FJs it is easy to over trim the jib- when over trimmed the luff of the main will begin to backwind
it is super important for the crew to look up at the slot and see the size and where the leech of the jib is positioned on the spreader


outhaul controls the draft (depth at the deepest point in the sail)
a deep sail creates power and is best to accelerate and get through waves and chop, especially in light air
flat sails are used when acceleration is quick(heavy air conditions) to help point higher
In the lightest of conditions, the draft should be a fist width deep, as the wind increases slowly put on more outhaul to make the main flatter


as the cunningham is tightened the draft moves forward and the leech twists open
0-8 knots
only enough cunningham on where the horizontal wrinkles in the luff of the main go up to the spreader
9+ knots
enough cunningham on where all horizontal wrinkles just disappear


tightens the leech and slightly flattens the sail
In FJs upwind, trim main to section 1, make vang tight, set it and forget it
In 420s upwind, just like the main sheet, needs to be constantly adjusted. In every puff, some comes on, and in every lull it comes off
On the downwind, boom parallel with the top batten

Leech Twist

the top of the main sail twists open when strong winds up high forces the leech to open
twist increases when the sheets are eased, vang is eases and cunningham put on
twist decreases (leech tightens) when main is trimmed, vang is tightened, and cunningham is eased
tighter leech will create better point
looser leech will provide more speed and accelerations

Velocity Made Good (VMG)

The portion of your speed that is taking you directly toward the mark
*A and B are both travelling at 5 knots on opposite tacks at the same place on the course. The dotted line represents the amount of their straight line speed is being used to take them to the mark (VMG).

This diagram shows the same boat travelling at different angles going upwind. Each angle change is just a degree or two difference: the higher the angle the slower you go but the more you point at the mark. The lower you point the faster you go but you are pointing further away from the mark. Your highest VMG angle is between a high and a low mode but all are necessary.

Boat Handling Drills

Windward Leeward
Short 2 mark course in line with the wind. Sail between the 2 marks doing several tacks and gybes to practice boat handling in an enclosed area.
Diamond Drill
4 marks in the shape of a diamond. Go around the diamond clockwise, round the windward and leeward marks to port, and the side marks to starboard. Around the windward and leeward marks complete a tack and a gybe to completely circle it.
This drill works on boat handling and mark roundings, works especially well in heavy air.
Rabbit Starts
1 specified boat will be the rabbit around a certain point. They will set up to one side of that point depending if they are starting on port or starboard. The rest of the fleet will set up on the opposite side of that point on the opposite tack giving each other plenty of space. On the whistle the rabbit will round the mark to a close hauled course and the rest of the fleet will duck the rabbit so that they are close hauled as they take the rabbits stern. Rabbit tacks after the last boat ducks
The goal is to get the whole fleet full speed on the same ladder rung
Around the World
1 mark will be in the water with a coach boat circling it. All boats will circle around both the mark and the coach boat as it moves in the specified direction.
The goal is to practice boat handling at different angles and correct sail trim.

Complete 15 tacks, 15 gybes and 15 accelerations.

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