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Author Topic: Mast rake  (Read 556 times)

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andre

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Mast rake
« on: February 16, 2020, 03:07:39 PM »

Hi guys is there a chart for adjusting and check the rake of our mast. C34 standart rig. I see a possible adjustment on the forestay So on my boat I don’t have a backstay adjuster and maybe I can give a better rake with the basic adjustment. Thank you
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Ron Hill

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Re: Mast rake
« Reply #1 on: February 16, 2020, 04:14:37 PM »

Andre : I was happy with 4"-6" 

A thought
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Noah

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Re: Mast rake
« Reply #2 on: February 16, 2020, 04:43:52 PM »

Ron—how did you measure the rake—with a line and plumb bob/weight hanging from the top of the mast?
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andre

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Re: Mast rake
« Reply #3 on: February 17, 2020, 10:31:22 AM »

Ok thank I will go with a big plumb with my main halyard in a bucket of water if there is a lot of wind to check if I have a couple of inchs
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Ron Hill

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Re: Mast rake
« Reply #4 on: February 17, 2020, 01:56:08 PM »

Noah : I used the main halyard.  You need to off set and list the boat (I used the starboard side) so the main halyard will not get interference from the boom.  I attached a crescent wrench to the main halyard and kept it just off the deck on a NO wind day and then adjusted the fore and back stays to get the rake of 4-6 inches.   
This measurement is good to get started, but then you need to go sailing and fine tune/check it from there.    :thumb:

A thought
« Last Edit: February 26, 2020, 01:50:24 PM by Ron Hill »
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rmbrown

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Re: Mast rake
« Reply #5 on: February 18, 2020, 03:10:02 AM »

I'm assuming, maybe incorrectly, that mast rake is measured relative to the boat, and so the boat must be trimmed properly for and aft.   Is there a spot on our boats that should be level before starting this process?
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Mike Brown
1993 C34 Tall Rig Wing Keel Mk 1.5
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Noah

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Re: Mast rake
« Reply #6 on: February 18, 2020, 11:12:01 AM »

Mike—I assume the boat sitting level to its painted waterline is the “starting point”.
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1990 hull #1014, San Diego, CA,  Fin Keel,
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rmbrown

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Re: Mast rake
« Reply #7 on: February 18, 2020, 12:25:22 PM »

Sure makes sense in theory... anyone know if there's some part of our boat that happens to be parallel with the design waterline so a level could be used instead of my eye? :)
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Mike Brown
1993 C34 Tall Rig Wing Keel Mk 1.5
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Ron Hill

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Re: Mast rake
« Reply #8 on: February 18, 2020, 03:21:25 PM »

Mike : I know my boat is "level" with the aft tank full and there is no standing water (rain or washing) on the cockpit floor as it all drains out the scuppers!!  That "level" also matches my water line.

That's the way I determine it !!  A thought
« Last Edit: February 26, 2020, 01:56:19 PM by Ron Hill »
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Roc

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Re: Mast rake
« Reply #9 on: February 19, 2020, 11:24:31 AM »

4"-6" is what I remember too, but it's not easy to really measure that accurately.  You have to get a very weighty plumb bob to stabilize the halyard, otherwise it moves with the slightest wind.  Also, having something so big hang on the end of halyard makes it difficult to measure that "4 to 6 inch" target.  What helps is to stand way back from the side of the boat and get a visual on the rake of the mast related to the horizontal hull.  It should be barely noticeable.  Then you need to go sailing and check for excessive weather helm.  Too much means you have too much rake (center of effort too far aft).  If that's so, then reduce rake and go sailing again.  It's an iterative process.  It's really the feel of the weather helm that helps you dial in the rake, since that's the outcome you are looking for (a balanced helm, meaning a little weather helm when on a close reach in light to moderate wind).
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Roc - "Sea Life" 2000 MKII #1477.  Rock Hall, MD

Jim Hardesty

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Re: Mast rake
« Reply #10 on: February 19, 2020, 04:35:45 PM »

Quote
you need to go sailing and check for excessive weather helm

IMHO Roc is correct  :thumb: The only way to fine tune a rig is by sailing.  You can ball-park it at the dock, but be warned when eyeballing, the rake/bend of other boats may sway the eye.  FWIW, when the boat is on the hard and the rudder is visible I take my best estimate of 5 degrees of rudder and mark my wheel.  That is what I shoot for weather helm. 

Jim
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Jim Hardesty
2001 MKII hull #1570 M35BC  "Shamrock"
sailing Lake Erie
from Commodore Perry Yacht Club
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Roc

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Re: Mast rake
« Reply #11 on: February 20, 2020, 06:39:57 AM »

Hey Jim
Interesting to mark the wheel at 5 degrees.  Never thought of that.  But for weather helm, I feel you don't want to fight the wheel.  If you do, then that's way too much weather helm.  I shoot for letting the wheel go, and the boat should "slowly" head up.  If it does, that's just enough weather helm. 
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Roc - "Sea Life" 2000 MKII #1477.  Rock Hall, MD

andre

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Re: Mast rake
« Reply #12 on: February 25, 2020, 04:32:32 PM »

Just an idea, if I use a nevel on the floor inside the boat when I am in the water is it good to know if the boat is really straight before checking the rake?
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Noah

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Re: Mast rake
« Reply #13 on: February 25, 2020, 05:37:21 PM »

Level on the cabin sole will not necessarily translate to level in the water. Same issue goes with the mast being 90 degrees to the deck doesn’t mean it is actually pointing straight up. This is a confusing equation (at least for me to grasp). Best, I can figure is to visually first gauge if the boat is sitting trim on its painted waterline. If it is not, adjust tankage and gear level(s)  to get as close to design trim line as possible. Then, make some adjustment in head and back stay tension to alter mast rake, test for weather helm under sail...then keep adjusting stays until the preferred weather helm (almost neutral or slight weather helm under your normal sailing conditions and full sail) is achieved. Caveat: this is all theoretical for me, as my boat sails fine, having adjusted the new rigging 4 year ago with a rigging tension gauge—without being overly concerned about mast rake. When I have to much weather helm I ease the main or reef.
« Last Edit: February 25, 2020, 08:57:16 PM by Noah »
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Roc

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Re: Mast rake
« Reply #14 on: February 26, 2020, 09:56:52 AM »

Hi Andre
Using a level on the boat is not the same as using it in your house.  Nothing on the boat is level, plumb or flush with anything else.  At least not to the degree your house would be.  You use a level to hang a picture in your house, but if you use it to hang something in the boat, most likely it would be crooked.  Even if the boat is level with the waterline boot stripe, I wouldn't say structurally, everything else inside the cabin is level.  I've found in hanging something in the boat, you need to eyeball it's "level" with everything around it so it looks reasonable.  What Noah said is pretty much what to do.  Get the boat as best you can sitting straight, adjust rake, then go sailing and see how much weather helm you get.  Too much, reduce rake.  If you have Lee helm, then you have negative rake (mast rake too far forward).
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Roc - "Sea Life" 2000 MKII #1477.  Rock Hall, MD
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