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 -----Original Message----- 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 To: cnc-list@cnc-list.com Cc: Tom Buscaglia <t...@sv-alera.com Subject: Stus-List Linear Auto Pilot install 37+/40 I am moving forward with the below deck linear drive install. We put in the structural support and then exposed the rudder post. However a few oddities. First, in spite of the build plans calling for an 80mm diameter rudder post it is, in fact, 75mm. And, although the Images that Josh posted if his install show a keyway on his post, mine does not have one. I’ll check with Edson to see what they recommend for attaching the tiller arm. Sigh... Stay safe all. Tom B Typoed from my iPhone Tom Buscaglia Alera 1990 C&C 37+/40 Vashon Island WA O 206.463.9200 C 305.409.3660 Skype - thombusc _______________________________________________ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray _______________________________________________ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
