tuning mast rake

[jon_old]

I am still struggling a little with my nova and recently revisited the tuning guide. I was short by about 20 cm short on my mast rake measurement so I moved the shrouds up one hole and after applying quite some pressure managed to get to something like the correct rake measurement. Is this what I should have done ? On the guide it says apply 75 kgs of pressure but I do not have a guage. She did seem to move better though but it wa breezy.
I do have some marking for the mast adjuster on the bow reading around the 100 mark would this be KGs
? any comments would be appreciated
Jon
516

[Peter481_old]

Hi Jon,

Bit of a late repsonse and you might have gathered this already, but just in case you haven't...

Don't worry too much about getting exactly the right rake, I would say that it's not that critical.

If you have the "trapeze cleat" type of adjuster on the forestay, I would use 4 holes from the top on the shrouds and pull on "some" tension. 75kgs is not a lot at all...if your shrouds twang an audible note like a double bass, then you've probably got way too much You'll need to move to 5 or 6 holes down on windy days.

Those of us with rig adjusters generally use 4 or 5 holes down for our "upright" position. I have a stopper on the adjuster so that upright rig gives about 75kgs. As I let the forestay off, the rig tension dissappears and the rig falls backwards. I have sailed with with so much rake that the boom only just makes it over the tiller during tacks. You soon get a feel for how much you need and how much it is helping or hindering your sailing on windy days.

Spreaders are a bit of a mystery. In my opinion, there is not really enough rig tension available for the spreaders to produce the sort of prebend that would make a huge amount of difference upwind. Most people use the website tuning guide settings nonetheless. As most of us are sailing with NO rig tension upwind, the spreaders will only have a side-to-side effect...i.e. when the windward shroud is tight with wind pressure and the leeward shroud is loose, the windward spreader will stop the top of the mast bending away to leeward, so having shorter/backward spreaders would help the gust response by bending away like a carbon rig. Conversely a longer/forward setting would keep the mast stiffer and straighter - but again only in the side to side direction.

Peter

[jon_old]

Many thanks Peter I will give your suggestions a go
sorry it took me so long to reply I had forgotten to check
Jon

[CliffMilliner_old]

Hi,

I measured my mast rake before trying the new sail this weekend, numbers below. Taken from the Transom deck, with no controls on etc.

Upright /off wind
6.07m, Tension= 300lb's on the shrouds
Normal upwind, when hiking
5.96m
Upwind, blowing a gale
5.84m (as far off as it will go)

Cliff
684

[Chris1100_old]

cliff, 300lbs! That's massive. I doubt there is anyone else who goes much over 200 (happy to be proved wrong!).

The rake discussions depend hugely on if you have a mast ramp or not.... I.ll get the tape measure out when it's warmer!

Chris

[MikeHall_old]

I can't put 300lbs into my rig without the boat folding up!

I think that all of the older Giles boats are the same, I don't know if anyone who has one can manage it? You can with the new foam sandwich ones however, and that opens up some interesting ways to control the sail shape.

Mike

[CliffMilliner_old]

Funny you should say that, I did check my numbers before i wrote it as i thought it was a bit high, so i may have read the gauge wrong, I'll check again on sunday, and report back.

Cliff

[MikeHall_old]

Cliff,

Most gauges will over read unless to have 4-5' of wire either side of the measuring point, so measure as high up as you can.

Mike

[CliffMilliner_old]

Second try!
Taken at shoulder height on the shroud, with a slightly battered Superspars gauge, so you may want to give or take 30lbs.

It reads 25, so assuming its 2.5 dia wire (is that correct?) thats 300lbs, if its 3mm its 285lbs.

I must stress I only sail with this off wind to try and power the rig up as i sail with very loose lowers. And if I'm overpowered on a tight reach i let it off a bit. I don't subscribe to the let the tension off on a run to sail deeper idea.

Cliff

[jon_old]

many thanks for your help boys
will borrow a guage and have another go.
jon

[Steve 705_old]

The site does have some guidance on tension, although it is a little old and people are sailing it differently, however starting at 160 lbs is good, I wouldn't recommend going much above this, and only drop below (to no tension) when you have got yourself sailing it flat consistantly.