Capricorn has a few really great tuning guide, like the Capricorn F-18 Tuning Guide

In the point 3.2.2, Mast rotation:

"More mast rotation – less downhaul tension = [color:"red"] height [/color] and power."

Power, ok, it's clear for me, but hight? I will try it, but I can't see the reason, why.

Any idea, why ?
Suggestions?

Sanyi

Perhaps they mean you can sail higher into the wind?

'xactly

I also think it's mean "point higher" into the wind.

From the text:

"If you want to point higher for tactical
reasons the mast rotation must be slightly increased and the downhaul has to be eased a bit."

But, I have a feeling, if I increase the mast rotation, I will point lower. Is my feeling wrong ?

thans for the help,

Sanyi

ps: I'm sailing a Nacra F18, not a Capricorn, but I think it is independent from the boat.

No, I think that they are trying to make the point that it is different from your boat. I suspect that the mast is bendier and therefore tunes differently. Also, as they explain, the sail is cut differently from conventional.
I know that experience has shown the F16 sailors (with a wing section mast) that it is necessary to de-rotate to de-power.

bobcat has it right. Unless you're on an infusion, do not use the capricorn mast tuning guides.

still, though - it gives you something to consider and try.

As you rotate aft (decrease rotation), you bend the mast more along its major (long) axis with increasing sheet tension. This tends to do a couple of things.

1. It decreases leech twist.
2. It flattens the sail more evenly top to bottom because the mast is bending more evenly top to bottom.
3. It provides a better shape for speed especially in flat water.

Keep in mind that as you sheet tighter with the rotation more aft, you need to pull on more downhaul to keep the draft of the sail from moving too far aft and to help open up the top of sail. This will depower the top of the sail first where it should be depowered. Most crews want the top of the sail to "go away" in typically over 14 knots of wind.


As you rotate forward (increase mast rotation), you bend the mast more along its minor (short) axis with increasing sheet tension. This tends to do a couple of things.

1. It bends the mast more at the top than in the mid to lower sections.
2. It flattens the sail more at the top and keeps it fuller in the lower to mid sections.
3. It provides a better shape for power especially in chop.

Easing the downhaul will keep the draft in the right position and keep the top of the sail from getting too open. A typical scenario might have you 50-100 yards from the weather mark and just barely fetching. Try rotating forward 5-10 degrees and ease off the downhaul about 1/2". It'll feel like downshifting into a lower gear.

If you are sailing upwind and the wind shifts to where you are going more into the waves on one tack and more across the waves on the other tack, the rotator can be a powerful tool as you can rotate more aft on the tack going across the waves because there is less resistance and rotate more forward on the other tack to power the boat through the waves coming more direct on your bow.

Fun stuff.

Bob Hodges
A-Class USA 230

Thanks to everyone to thinking with me and help. I will try some setup soon.

What I can imagine, if I setup the main for the more power and lower speed (more rotation and less downhaul), than

- there will be a bigger power on the main
- there will be the same power on the jib (or less, because of lower speed)

It’s all mean; the total force on the sails will move backwards, consequently --> the boat will point higher.

Maybe.

??

I will really test it.

Sanyi

Thanks Bob for taking the time to explain this and give some examples.

It's sort of interesting, your response is very similiar to a guide written in the 1960's by Reg White.

Left out of this discussion is the effect of
draft position to pointing angle. The further forward
the draft, the less high you can point. Easing
the downhaul allows the draft to move aft.