Thanks Chuck. I had measured using a old style
caliper and then reading it on the scale on my
digital caliper which came out as 75mm. But
after your caution I decided to waits for a real
micrometer to get the true(r) measurement.
I think that drilling the hole for the through
bold will be a huge PITA as the short end of the
arm is facing the transom and the vertical
support we put in to reenforce the deck. Also,
there's not much room there. Should be fun...
Tom B
At 06:46 AM 4/20/2020, you wrote:
Message: 2
Date: Mon, 20 Apr 2020 08:11:17 -0400
From: "Chuck Gilchrest" <csgilchr...@comcast.net>
To: <cnc-list@cnc-list.com>
Subject: Re: Stus-List Linear Auto Pilot install 37+/40
Message-ID: <01ec01d6170c$cc1ce360$6456aa20$@comcast.net>
Content-Type: text/plain; charset="UTF-8"
Tom,
Thought I'd weigh in as a former Edsonite.. The
most important thing to realize when installing
the autopilot is that the clamping action of the
arm and cap for the tiller arm is the primary
form of attachment to the rudder post. Edson
makes the arm with a .002" clamping tolerance to
the diameter of the rudder post. The secondary
or "failsafe" attachment is a key, through bolt,
or set screws. When you order your tiller arm,
don't assume that C&C always used the same
diameter stainless post for every boat and
model. It's important to get precise
measurement of the post where you wish to attach
the arm, preferably using a digital caliper to
achieve the proper tolerance. Measure the exact
diameter of the post, and take several
measurements as you rotate the caliper around
the post at a variety of positions where the
tiller arm will attach. When Edson bores the
arm to your specification, they'll insert a
small piece of paper between the arm and
cap. Removing it will give the arm the proper
undersized clamping tolerance needed for the arm
to grab the post without slippage. Again, the
keyway or through bolt should prevent the arm
from rotating ONLY if the clamping tolerance is
compromised, as in a hard grounding, rudder stop
failure, or other drastic event.
As you've found, if there's no accessible keyway
cut in the post, the through bolt method is
preferred if the post is hollow (typical
with SS posts) or set screws if the post is
solid (usually with a bronze rudder
post). Getting the arm positioned to drill the
post and tiller arm can be problematic, finding
a drill bit long enough to get it in place and
then drilling through the hard steel (thus the
need for a carbide bit and some lubricating oil
to prevent work hardening the bit) but avoid the
temptation to "pre drill" the arm before
installing on the post. This is because the
likelihood of you being able to match up the
holes on the post with the holes on the arm are
not great given the confined space you'll have
to work with and the difficulty of keeping the drill level while you work.
The tiller arm has a very important plus side as
it enables your autopilot to serve as an
emergency tiller in the event of a steering
system failure such as a fractured radial drive,
cable breakage or idler failure. Finally, make
sure that the autopilot isn't set up as the
rudder stop as damage to the autopilot can occur.
Good luck with the install and Edson is a good source for advice..
Chuck Gilchrest
S/V Half Magic
1983 35 Landfall
Padanaram, MA
>From: CnC-List <cnc-list-boun...@cnc-list.com>
On Behalf Of Tom Buscaglia via CnC-List
>Sent: Sunday, April 19, 2020 6:19 PM
...snip...
>... greatly appreciated. If you want to
support the list - use PayPal to send
contribution -- https://www.paypal.me/stumurray
.¤º°`°º¤,¸¸,¤º°`°º¤¤º°`°º¤,¸¸,¤º°`°º¤.
Tom & Lynn Buscaglia
SV Alera
C&C 37+/40
Vashon Island WA
(206) 463-9200
www.sv-alera.com
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