Your math is better than mine!
(What was I thinking?)
Steve.
---- coltrek via CnC-List <cnc-list@cnc-list.com> wrote:
Mine called for one degree of Rake. Which at the top of the Mast, equated to
around 11 inches off of vertical
Regards,
Bill ColemanC&C 39
-------- Original message --------
From: "Matthew L. Wolford via CnC-List" <cnc-list@cnc-list.com>
Date: 3/25/17 10:08 (GMT-05:00)
To: cnc-list@cnc-list.com
Cc: "Matthew L. Wolford" <wolf...@erie.net>
Subject: Re: Stus-List Mast Step Pitch & Helm Balance
I had a similar question about rake before making a Spartite plug for the
partners. Unless you talk to Rob Ball or someone involved with
design/construction, it would be difficult to figure out what C&C’s
intentions were (assuming that’s what you want). I’m guessing that you’ve
already given the matter more consideration than the construction crew.
In my case, I eye-balled other comparable vintage C&Cs to see generally
if there was much rake. There appeared to be a little, but not much.
I then talked to a local sailmaker, and together we looked at C&C’s original
drawing for my boat to see if it showed any rake, which it did (again not
much). From this, we concluded that the drawing likely reflected what
C&C intended. Using the drawing, I calculated the amount of rake and,
because in my case the mast was standing, I adjusted it to the amount of rake
shown in the drawing (using a bucket of water hung from a halyard). Seems
to have worked – the helm feels about right to me.
Based on my experience, I’d find an old drawing and assume it’s more or
less what C&C intended.
Good luck.
From: RANDY via CnC-List
Sent: Saturday, March 25, 2017 3:11 AM
To: cnc-list
Cc: RANDY
Subject: Stus-List Mast Step Pitch & Helm
Balance
Listers-
Seeking your input here. I'm in the middle of the mast step rebuild
project a la http://cncphotoalbum.com/doityourself/maststep/maststep.htm.
Lots of pictures of the project at
https://drive.google.com/open?id=0B-NqAxQ6JxFTSzRLbFo0NDl6U1E.
I'll be cutting new supports from laminated GPO-3 slabs Saturday night or
Sunday morning. Before installing the new supports, I have to decide on
the elevation of the aft support. Of course I took careful elevation
measurements from the cabin sole before removing the original supports.
But the question is, what was the original shape of the top of the aft
support?
I believe the middle of Grenadine's aft support, under the mast step block,
was compressed down from its original elevation due to a combination of
weakness
in the support and standing rigging tension (especially backstay). Have a
look at the pictures and you can clearly see what I mean, e.g.
https://drive.google.com/open?id=0B-NqAxQ6JxFTLXZuXzd1T1pkR28. This
compression has the effect of pitching the mast step aft, thereby moving the
masthead aft, thereby increasing weather helm (which I've definitely noticed
under enough wind and sail - it was strong under full main and #2 genoa in 30
kts, not surprisingly).
However I also believe that the original elevation of the aft support may
have been carefully tuned for helm balance, prior to compression below the mast
step block due to weak wood and standing rigging tension.
The reason this elevation question matters so much is because, using
trigonometry, I can calculate the distance by which different elevations of the
aft support will move the masthead forward or aft, which in turn will affect
helm balance. Each quarter inch of aft support elevation difference could
move the masthead about three inches I believe.
The last picture
(https://drive.google.com/open?id=0B-NqAxQ6JxFTU3hRNmZoMUU1MFk) in the Google
Drive folder linked above shows the templates from which I'll cut the new
supports, traced from the original supports removed from Grenadine's
bilge. I hypothesize that the dashed line I drew at the top of the aft
support template may have been the aft support's original elevation.
I'm halfways tempted to split the difference and cut the new aft support to
have that elevation. Of course, I could be full of crap, because I tune
the mast rake using the stays after all, which probably influences helm balance
more than mast step pitch. And of course I can control the sail selection
and sail trim, which probably influence helm balance more than mast step
pitch. However, for a given sail selection close-hauled, with neither the
backstay nor forestay over-tensioned, the mast step pitch would certainly
influence the masthead position and therefore the combined center of effort of
the sail plan.
What say ye? Does anyone out there know if the top of the original
aft mast step support on a 30-1 was flat all the way across, or did it come
from
the factory with a little elevation drop to tune helm balance? I'll be
committing an assumption about that to a GPO-3 slab with my jigsaw in the next
day or two.
Thanks in advance,
Randy Stafford
S/V Grenadine
C&C 30-1 #7
Ken Caryl, CO
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