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Optimum Mast Angle for Racing

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Created by Bundeenabuoy 1 month ago, 21 May 2019
Bundeenabuoy
NSW, 510 posts
21 May 2019 6:32PM
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What do think is the best angle for speed and drift?
Does it change depending on the point of sail?
Does it change for different boats?
Does keel design effect this angle?

Donk107
TAS, 2173 posts
21 May 2019 7:10PM
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This doesn't answer your question but it is a interesting read www.sailmagazine.com/cruising/what-mast-rake-is-all-about

If Rumblefish doesn't post an answer to this It would probably be worth sending him a PM

Regards Don

Craig66
NSW, 1650 posts
21 May 2019 7:37PM
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Upright ???

Kankama
NSW, 208 posts
22 May 2019 6:58AM
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Mast rake is mostly a case of balancing the centre of effort in the rig with the centre of lateral resistance in the hull/keel/rudder combo. We can't move the mast on our large boats much so we can only rake the mast back and forth.

A small amount of rake - a few degrees - aft is usual for going upwind. If you watch the Star sailors league on Youtube, or watch a local Etchell state or national title, you will see the masts raked back at an angle of about 3-5 degrees upwind and then raked forward much more for the square run.

Masthead boats don't usually have as much rake as some fractional boats. Skiffs and sports boats often have quite a lot of rake. They do not rake forward going downwind because they run large kites and tack downwind - keeping the apparent forward anyway.

So don't worry about rake too much. Get the boat the feel nice, with a little bit of weather helm upwind. If too much weather helm, rake the mast forward some more, but don't rake it forward of vertical permanently- that is almost never done. There are probably some issues with engineering from reducing sidestay angles when raked far forward.

Rake can get extreme. I remember once see an Farr 1020 with about a metre of aft rake - it was huge. I told my then girlfriend (now wife) "Now that guy raked his mast too much - he probably doesn't know much". Then I met my old boss, a bronze medallist and Olympic coach on the shore. "Gday Ian - is that your boat?" It was.

There is no magic angle.

Galatea
VIC, 65 posts
22 May 2019 7:35AM
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Kankama is correct. Mast rake is all about helm feel.
Too much and you will have a lot of weather helm, too little and you have Lee helm.
No magic number, so variable from boat to boat.
Ideally should be set so when you release helm, boat slowly rounds up into wind. But even this is dependent on sheet tension, sail twist etc.
If the helm feels good then its usually right, if helm is heavy or unbalanced its wrong.

lydia
835 posts
22 May 2019 6:20AM
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Etchells sailor can recite mast rake measurements more quickly than their partners birthday!
And mast base measurements!
So depends on boat, conditions, sea state, etc etc etc
At the end of the day it is just feel.

lydia
835 posts
22 May 2019 6:21AM
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Select to expand quote
lydia said..
Etchells sailor can recite mast rake measurements more quickly than their partners birthday!
And mast base measurements!
Even different rakes for different series of hull builds and keel position.
So depends on boat, conditions, sea state, etc etc etc
At the end of the day it is just feel.

rumblefish
TAS, 726 posts
22 May 2019 10:28PM
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Select to expand quote
lydia said..
Etchells sailor can recite mast rake measurements more quickly than their partners birthday!
And mast base measurements!
So depends on boat, conditions, sea state, etc etc etc
At the end of the day it is just feel.


Spot on as always mate!!
Was going to say if you want to learn about mast rake (and rig tuning in general) go sail a one design class like an Etchells, Melges 24, Star etc.

On top of that there is the old dinghy (mast with no spreaders or backstay) system of leaving the rig loose in lighter breeze so that the mast comes aft upwind and falls forward downwind.
I found this quite fast in my Sabre in sub 7 knots but was a pain in the arse if the breeze picked up mid race as it was hard the flatten the main

Chris249
189 posts
23 May 2019 4:01PM
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Select to expand quote
Bundeenabuoy said..
What do think is the best angle for speed and drift?
Does it change depending on the point of sail?
Does it change for different boats?
Does keel design effect this angle?



1- Depends on the wind and the boat.
2- Yes; generally aft for upwind, forward for downwind. For a while when I was a kid we had IOR boats with approx 3ft long hydraulic rams on the backstay AND forestay, so you could move the masthead several feet forward and aft - aft upwind until it got windy then the rig would move forward to reduce weather helm; forward downwind.
3- Yes; for example J/24s tend to get lee helm in light airs so have the greatest rake allowed under the rules in such conditions. Some boats increase rake in strong winds as the stay/mast gate geometry then increases mast bend. Others reduce mast rake in strong winds at times because they wind on the forestay to increase rig tension. Some British dinghies have one string that eases back the forestay AND tightens the sidestays at the same time.
4- Yes; the J's keel is too far forward. Flying 15s have an inefficient keel so if I recall correctly, use aft rake to load the rudder (like Hobie 16s) to ensure that it develops lateral resistance efficiently.

In summary - research the class to find out what works



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"Optimum Mast Angle for Racing" started by Bundeenabuoy