The direction I was going in was setting a reference point for comparing mast
rake
numbers between boats, or even getting back to last years tuning for those of us
that pull the mast every year.
Yes, the rake is whatever it is with the boat as sailed. Stern high or low.
I had asked a rigger a while back if adjusting the rake right after I stepped
the
mast made any sense, since the boat was empty and the boom may not be on.
Even one person walking around would change how it sits. The answer was to
adjust the rake in real world conditions to were it should be. Then measure it
for reference for next year. It could be as sailed, but the advice was that just
getting the boat level ( only as a reference starting point ) was easily
repeatable
even fully rigged or stripped.
I guess this assumes we have the waterline painted the same way, even say
amongst 30-1.
The other consideration is whether increasing rack by adding weight to the
stern, or decreasing rake by adding weight forward has the same effect on
weather helm that changing the forestay length does. No idea.
Michael Brown
Windburn
CC 30-1
Date: Fri, 29 May 2015 10:57:59 -0400
From: Rick Brass rickbr...@earthlink.net
To: cnc-list@cnc-list.com
Subject: Re: Stus-List Mast Rake on CC 30
Message-ID: 00e601d09a1f$db178600$91469200$@earthlink.net
Content-Type: text/plain; charset=utf-8
Think about it a moment. You set mast rake with the boat in the water. By
definition she is sitting on her lines and it doesn?t really matter if she is
trimmed stern high or stern low.
Gravity points straight down, so the plumb bob (weight on the end of the main
halyard) hangs straight down and if you measure 6? of rake, you have the mast
slanted 6? aft of vertical.
In the days of square riggers, and on more modern topsail schooners, it is
common to trim the boat so it is down slightly at the stern. It is supposed to
make the boat faster; I suppose that could be because the press of canvas when
going downwind would push the bow down. I can?t think of a hydrodynamic reason
a boat down at the stern would be faster than a boat sitting with the bottom
level, but there may be one.
Among the things I acquired when I bought my 38 was some of her ratings
information from IOR racing in the 70s, and an article from a Canadian sailing
magazine about the 38-1 race boats and how to optimize them for tonnage racing.
Seems the 38-1 was designed to be slightly down at the bow ? I presume so the
weight of crew would bring her back to level in racing trim. And one of the
tips in the magazine article was to add 100 pounds of ballast forward (I don?t
recall the exact spot that was recommended) to accentuate the resting condition
? and pick up a couple of tenths of rating points.
Which is not really related to the discussion of mast rake. Just thought it
might be interesting since the discussion is drifting toward hull trim.
Rick Brass
Imzadi CC 38 mk 2
la Belle Aurore CC 25 mk1
Washington, NC
From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of William Hall
via CnC-List
Sent: Thursday, May 28, 2015 12:59 PM
To: cnc-list
Cc: William Hall
Subject: Re: Stus-List Mast Rake on CC 30
Seems to me that if the boat normally sails stern-low, it moves the center of
effort aft and has the same effect as raking the mast on a level boat...
On Thu, May 28, 2015 at 12:51 PM, Michael Brown via CnC-List
cnc-list@cnc-list.com mailto:cnc-list@cnc-list.com wrote:
I think the initial tuning of about 8 of rake, usually done by hanging
a weight on the main halyard, is a reference assuming the boat is
sitting level in the water. At least a few of the CC 30-1 I have
looked at are stern heavy, some by a couple of inches. I suspect
that will add some to the rake that would not be there if the boot
strip and water surface were parallel.
Under sail with crew on board the boat may sit properly. Given that
people have reported noticing a change in weather helm from even
a modest adjustment of rake the error in initial tuning by having the
stern 2 low might be significant.
A couple of weeks ago while out for practice starts we flew a heavy
wind #1 ( a flatter cut ) and full main. Winds were 18 - 22 kts, gusts
to 30. It was the wrong amount of sail to have up but the helm was
fine. Eased the vang a bit and left some twist in the main, kept the
#1 flat.
With the boat level I have about 6 of rake.
Michael Brown
Windburn
CC 30-1
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