Setting rake

[Mike48]

Every year I think I under stand how to tune the rigging on my h23, after reading several post until I start actually doing it. So I just spent the last week going over hundreds of post and think I fully understand every thing and the order it is to be done except one. The first thing I need to do after getting the mast in column with the turnbuckles loose is to set the rake with the forestay. But I don't understand how by adjusting the forestay (pulling the mast towards the bow) will put rake towards the stern. What am I missing?
I have a kenyon mast with 27" spreaders.

Thank
Mike

 

[Alan]

Mike mast rake is usually measured in inches along the boom. The mast does not need to be perfectly in column and given that the shrouds need to be loose, close is good enough. Lower the main halyard with a weight suspended so that it hangs just above the boom (if you use a plumb bob so much the better). Measure back from the rear surface of the mast to where the plumb bob hangs. That is the mast rake. For your H23 it should read about 4.6" which translates to 1 1/2%. To calculate any mast rake multiply the "P" dimension in inches by 1 1/2% (0.015). That number can be tweaked to personal taste. Increasing the rake will improve pointing at the cost of weather helm. A small amount of weather helm is a good thing but too much is disadvantageous. Increasing the length of the forestay increases rake and conversely shortening the stay decreases rake.

 

[Mike48]

Alan, if I stand the mast up and there is zero inches of rake with all of the shroud loose, including the forestay, than even if I took the forestay off I would still have zero rake. Or does the mast have a built in lean-to the stern? What am I missing?
Mike

 

[Alan]

Mike, do you have an adjustable turnbuckle at the base of the forestay? If yes, then simply loosen the turnbuckle to allow the mast to slowly lean aft till you see the correct mast rake as previously described. If you have no adjustable turnbuckle then you will need to add adjustable plates that will allow you to pin the forestay with the correct setting.
Pictured is an example of the adjustable plate with multiple holes to allow various adjustments.

 

[Alan]

BTW I have neglected to say that these adjustments are to be done while the boat is in the water. Of course, none of this applies if the boat is sitting on a trailer.

 

[Mike48]

Alan, I now understand that I'm to let the whole mast lean back under is own weight when I loosen the forestay turnbuckle to get the proper rake. This was the one thing that I was not understanding. I was thinking that only the top 1/3 or 1/2 of the mast was to be leaning back at this point of tuning the rigging.

Thanks
Mike

 

[Alan]

You got it!! :dance:

 

[isaksp00]

I have an H23 (new to me) and have only done the adjustment one time, when I launched last season.

Side-to-side was not that big a deal - I hauled a long tape measure up the main halyard and used it to adjust the upper stays to the vertical, making sure the distance to each side chainplate was the same, then tightened the lowers so it looked straight when sighting up the mast track. I actually found it pretty easy to view the sideward bend.

On rake - if you adjust the forestay so rake is as spec'ed while gravity holds it back, how do you assess correct rake once you tighten the backstay? The fractional rig makes the mast bend rearward, since the backstay is pulling from the very top while the forestay is somewhat lower down (pulling the mast "center" forward). Re-measuring after it is tight will show the plumb bob further back - how do you account for that?
Peter

 

[Alan]

An excellent question ! Mast rake is the very first thing you adjust when tuning your rig. It can only be done with a straight mast and on a fractional rig that means BEFORE any tension is applied either to the backstay or shrouds. If your spreaders are swept aft the backstay can be completely eased or released and the shrouds will need to be slackened enough to just support the mast. Now the rake can be set and usually left alone. It should only need tweaking to optimize weather helm.

 

[teddy629]

Alan,
once you have slackened your backstays and shrouds to allow the mast to straighten, is there a set order on tightening the shriouds to gain the appropriate rake? Such as Caps 1st, intermediated 2nd, lowers 3rd? Additionally, do you get rake from tensioning your cap shrouds or do the intermediates create more of the rake? As you begin to tighten your shrouds to create rake can you loosen the forestay at the same time to achieve the 10" - 17' rake rather than tighten everything to just have to start over if the proper amount of rake is not acquires. Lastly, I attempted to set my mast last year and found that the on my shrouds was high but the rake was no more than 8-10". My forestay was loose. I'm confused iin my attempt to get more than a minimum of rake.

 

[Alan]

Teddy, Your mast rake is not set or adjusted by the shrouds or backstay. The only way the set and adjust rake is with the forestay. When the mast is up and all supports are slack (no tension) the rake is measured and adjusted by increasing or decreasing the length of the forestay. Using the turnbuckle at the bottom of the forestay, loosening the turnbuckle will allow the mast to pivot aft increasing the rake. Shortening the turnbuckle will pull the mast forward decreasing mast rake. You measure the amount of rake with the main halyard setup. Only after you've achieved the correct rake setting do you begin to apply any tension to the shrouds. From this point on the forestay turnbuckle is not touched or it will change the rake setting. With the correct mast rake set, the rest of the rig tuning can proceed starting with the cap shrouds to get the mast in column. Use very little tension just enough to move the masthead from side to side (completely straight mast). I suggest using a tape measure hoisted to the masthead with the main halyard to check the mast in column. Measure to the chainplates on both sides as accurately as possible. This adjustment is critical get exactly right. If adjustment is needed you must reduce the turns on one side (cap shroud) while increasing the same number of turns on the other. Check and re-check till you get it exact. Only then can the rig begin to be tensioned for proper support.

 

[BroadReach]

What Is The Proper Rake ??

The comments outlined above about mast rake just about gets you there.

One must remember that the size of the head sail determines your mast rake,
If you call Hunter and ask what mast rake to use. They will reply in almost all cases that Hunter uses 9 to 10 inches on the Boom.
This is because Hunter provides a 100 or 120 jib in their sail package.

As such if your most used head sail is a 135 the rake is between 10 and 12 inches on the boom.

If your most used head sail is a 155 you will need anywhere between 15 and 18 inches of rake.

These numbers apply to most medium to large Hunters.

Why is there a range of rake. Mast rake produces weather helm.
I like zero weather helm because I don't care for rudder drag and it saves batter juice because the auto pilot does not have to work as hard: my rake is set at 16 inches after several change of settings of the length of the fore stay.
Some sailors use as high as 18 inches.

In any case performance sailing is not easy.

Broad Reach

 

[Bob 04 H260]

I have a B&R rig on my Hunter with no backstay. The mast curve is adjusted and preset to match the cut of the mainsail before it goes up.

I use an Ipod with the level app to measure rake with the boat on the water loaded for use. I find it sails best with about 1.5* of rake. It seems like a very accurate way to measure and keep track of tuning this type of rig as the amount of mast bend will effect measurements using the main halyard to boom method.

Bob

 

[Alan]

Bob, 1.5 degrees is a good all round number for mast rake. Please explain in as much detail as you can just how you use your ipod ap to measure and set the rake.

 

[Bob 04 H260]

Alan, I use the app "Tilt Meter" on the iPod. Their website is here,
http://www.tiltmeterapp.com/

I set the displayed precision to show tenths of a degree and place the iPod against the forward face of the mast just below the boom and read of the rake angle directly.

I have used this app to measure the angles the boat sits in the water on reference surfaces (like the bridge deck) so I could set her up on the trailer in the same position and adjust my rigging in the driveway if I wanted to or if I add something to the boat like extra fuel I can see right away how effects the trim, not an issue usually with a bigger boat but for me it makes a difference.

I have other boating apps on the iPod too, charts of all of the east coast of USA, a boaters reference book (1800 pages), animated knots, electronic subscription to Sail magazine, and Skype that works when I have a wifi connection. I like to use the iPod to check my email when on a cruise, easier than always taking the laptop to shore.

Also to adjust mast I attach a tape measure to a large sail slug as used on the sail head, I use the main halyard to raise it and downhaul to keep it fixed in one position anyplace on the mast. I found without a downhaul the stretch in the halyard would effect the measured value by the amount of tension used on the tape, the dowhaul allows me to take the stretch out of the halyard to eliminate this. I measure from side to side to masking tape on each gunnel, beside the mast, the position of the masking tape is measured back from the bow chainplate pin for the forestay. This way I can check for any side to side bend in the mast at any height.

I you need any more detail let me know, Bob

 

[RobertV802]

Question about reference number used. Near the beginning the formula was "P" times 0.015 for rake measurement but further down in the posts people are talking 8 to 10 inches as recommended by Hunter.
for a 25.5 which measure would be right - 4.77" or 8" t5o 10".
Thanks for the clarification.

Robert

 

[Alan]

Rake is not a fixed number. The best setting varies based on a number of things, ie: average wind, headsail size etc. I use nearly 3.5% for the rake on my boat. I use a #1 headsail (155) most of the time. This yields the best pointing to weather helm ratio for my boat. In general, you want to carry as much rake as possible and still have a controllable weather helm. I suggest using the higher number and give it a trial sail.