Mast butt position

How to make the boat go faster or compete within the Class.

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Guest

Post by Guest »

Does everyone set the mast butt to the tuning guides' recommendation of 460mm aft of the fwd bulkhead? North and Quantum both recommend this.

Also, the North Sails-UK guide shows the measurement to the trim along the base of the bulkhead - is that what they all mean? I'm sorry for perhaps overthinking this a bit, but I have to know!

[Posted by: Tom Niccoli
]
chris_z
Posts: 46
Joined: Wed Dec 31, 1969 8:00 pm

Post by chris_z »

Tom,

We use Doyle Sails, and we started with the 460mm position as the baseline. However, we are usually sailing in less than 10 knots of breeze, so we found that moving the butt back another 10mm greatly improved our performance, letting us sail much higher. It was amazing how different the sail trimming was after such a small change.

Z
Guest

Post by Guest »

Thanks Chris. How easy was it to change the mast butt position, and how did you do it?

Also, what do you go with for headstay length?

We also sail in light air a lot (Pacific Northwest).

[Posted by: Tom Niccoli
]
chris_z
Posts: 46
Joined: Wed Dec 31, 1969 8:00 pm

Post by chris_z »

It was pretty easy, although the fact we have the boat in a slip made it much easier than having her on a mooring. After loosening the nuts holding the mast in place, we loosened the shrouds and the backstay, then took the spinnaker halyard and ran it out ahead of the boat. We attached the spin halyard to a piling (so it projected more forward than down) and then tensioned it using a can, grinding until there was a lot of load. At that point the spin halyard was pulling the top of the mast forward, and that has caused the shrouds to now be tensioned. So we backed them off about another 6-8 turns and trimmed on the spin halyard again. Once it was under load, I went down below, and sitting on my butt bracing myself in the doorway to the vberth I used the heel of my foot and gave the mast butt a few kicks. It very easily slid backwards, as the tension on the top of the mast pulling it forward did all the work.

This whole process took about 5 minutes. Once we had it in place, we did the reverse, loosening the halyard tension a bit, tightening the shrouds 6-8 turns, then releasing all the tension and tightening the shouds to the correct tension on the loos gauge.

Hope this helps.

Z
Guest

Post by Guest »

Cool - thx

What are you using for headstay length?

[Posted by: Tom Niccoli
]
chris_z
Posts: 46
Joined: Wed Dec 31, 1969 8:00 pm

Post by chris_z »

I am going with however long the headstay is! The people who set up the boat when she was commissioned set that, and I have not adjusted it: and I'm not sure what the measurement is. I like the way the boat works, she goes pretty fast and points very well. But I can't tell you how long it is. I know there is a class rule on the 105s about the length, but I have never seen one for the 109.
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