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-   -   Proper mast rake (http://www.sailnet.com/forums/general-discussion-sailing-related/17620-proper-mast-rake.html)

noscreenname 06-24-2006 08:25 PM

Proper mast rake
 
I race a Columbia Sabre. She's a 7/8 rig with straight spreaders and all shrouds parallel to the base of the mast (deck stepped). I am trying to find out how much rake to induce in the mast for our conditions 5-15 most of the time. I hired a local rigger to give me advice and he said 12" or more. This seems a bit extreme to me. Does anyone have a suggestion?

pluscard 06-24-2006 10:10 PM

On my J/24, the mast clearly has more rake than the cruisers at the dock... they're all lined up in a row, and my boat may have as much as 8-12" more rake. Not sure how much rake in a cruiser, but I'm assuming there is some, so 12" total may not be as much as you think.

Mike

paulk 06-25-2006 07:55 AM

The amount of rake you want depends upon the boat. The idea is to use mast rake to balance the helm. Doing this helps keep the boat sailing faster, since (with the forces at work on the hull and keel and sails) you're not always keeping the tiller at an angle in order to get the boat to go straight. Rake also helps use the weight of the mast and the force of the backstay to keep the forestay tight, so you can head closer to the wind. This is especially important for racers -- hence the hefty rake mentioned for a J/24.
Rake is not the same thing as mast bend: curving the mast so as to flatten the sail. You shouldn't have to worry about mast bend much with a Columbia Sabre. Getting the mast to bend even just 4" would likely be an effort, and in less than 15 knots, probably not any use. Your sailmaker can tell you more about that.

In the meantime, attach your main halyard to a wrench by the hole in the end of the wrench handle and put a yardstick down on your cabintop, aft of the mast. Adjust the forestay (don't forget to loosen the backstay) until the wrench kisses the 12 when the boat stops bobbing from you moving around. Snug up the backstay and go out sailing. Feel any difference on the helm? If there's too much weather helm going upwind, take some rake out. Too little helm, add more rake. It's not Rocket Science, but it should make sailing the boat easier (less fighting the helm) and improve performance.

sanjuan2R 06-25-2006 03:44 PM

mast rake
 
paulk -
Do you mean you want more slope of the mast towards the bow of his boat? I was under the impression that rake meant toward the stern. I am re-rigging a 37 ft. cruiser and need to find the best mast angle. It has much too much weather helm to the tiller, which wears out the helmsman on an afternoon cruise. Any suggestions?

Randy

noscreenname 06-25-2006 05:09 PM

No such thing as forward rake, Meaning beyond vertical. No boat will point well with the mast forward. The question is Deg of rake relative to it's design,For instance I believe j boats use a lot of rake,105's use 20+ inches because the mast is ahead of the keel thus if the mast were left straight there would be too much lee helm.
As I understand it more rake = more helm and I'm struggling to find that balance. In our case we now have 12" of rake but the rigger accomplished this by adding 3 toggles in front and shortening the back stay.(Not good) I now have what I believe to be a little more rake than needed and the foot of the sail is 10" or more off the deck at the tack and several feet at the clew, so much for the "end plate effect". We raced the other night with this set up for the first time and finished 7th when we've never finished below top 4.
In my case the heavy rake induced some helm,enough to point better, but the lifted Jib was under powerd so we pointed without speed.
In any case it's never desirable to have the mast leaning forward.

sailingdog 06-25-2006 06:33 PM

Most boats should have just a touch of weather helm, which is good, and helps the steering be more responsive, helps the boat point a bit better, and helps generate a bit of underwater lift to windward. The worst thing to have is lee helm, where the rudder helps stall the boat.

Also, might want to look at this thread: http://www.sailnet.com/forums/racing...mast-rake.html

Faster 06-27-2006 02:02 PM

"In any case it's never desirable to have the mast leaning forward." by noscreenname...

Suggest you look more closely during the America's Cup next time around when the boats are running. Many race boats do, in fact, if they have the capability, lean their rigs dramatically forward on downwind legs.

Admittedly it's not something you see much of during the local club events.

noscreenname 06-27-2006 02:15 PM

Quote:

Originally Posted by Faster
"In any case it's never desirable to have the mast leaning forward." by noscreenname...

Suggest you look more closely during the America's Cup next time around when the boats are running. Many race boats do, in fact, if they have the capability, lean their rigs dramatically forward on downwind legs.

Admittedly it's not something you see much of during the local club events.

Agreed but I was discussing pointing ability.

Jeff_H 06-27-2006 06:19 PM

Historically, boats of that era were typically designed with a 1/4" of rake per foot, and then tuned to provide a balanced helm. 5.5 meter class boats of that era (which is what the Sabre was) typically began life without a huge amount of rake or bend in lighter going and a bit more in heavier winds which seems counter intuitive but more backstay pressure meant more headstay pressure.

For the record, a boat designed for forward mast rake will point perfectly well with foreward mast rake. Some IOR era boats were designed that way. Went up wind just fine. Its all about the design of the boat.

Jeff

infonote 06-28-2006 02:35 AM

On boats like H-Boats, having the mast lean forward is done. I agree that it improves performance.


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