[C320-list] steering geometry question

[Dick Walker]

I installed a B&G autopilot. It has worked great the past 16 years. I can photo the aluminum plate that was made to mount if of that would be of use



Cheers



Dick Walker
WindWalker II. C-320 #687
740 Olive Ave.
Coronado ,CA 92118
619.435.8986



> On Sep 16, 2015, at 13:37, Graeme Clark <cg at skyflyer.co.uk> wrote:
> 
> Jeff
> 
> Thats really useful, thanks. I am considering almost the same set up but using a hydraulic drive that has only 10 inch throw, but twice the thrust of Rays’s linear type 1. Its actually less pricey too!  However I take your point that the attchement point of the ram  to the hull then becomes the issue, so maybe the Type 1 is the way to go after all.
> 
> Another British 320 owbmer has had that done and sent me photos; sounds very much like your arrangement with the base of the ram fixed to the aft cabin wall just to the starboard and above the access hatch, with backing plates.
> 
> Tnaks again
> 
> Graeme
> 
>> On 16 Sep 2015, at 18:52, Jeff Hare <catalina at thehares.com> wrote:
>> 
>> Hi Graeme,
>> 
>> I just completed this project last weekend. Special thanks go to Allan Field
>> and Scott Thompson who were great resources (and Jon Vez for sending
>> pictures of the Rudder travel limiter configuration used on his C355)
>> 
>> Rudder post is 2.860" in diameter according to Edson.  The factory rudder
>> travel seems to be around or slightly over 40 degrees each direction.
>> 
>> On our hull (#809) from the wheel amidships,  I used to get exactly 1 and
>> 1/2 turns of the wheel each direction.  With the AP installed I now get
>> exactly 1 and 1/4 turns each direction with my installation.  After studying
>> it a bit and experimenting with mounting angles etc, there are several
>> aspects of the geometry here that really does prevent a linear drive unit
>> from doing the full lock to lock you get from the factory on the C320.  But
>> with the mounting/drilling dimensions/angles I used, I give up very little
>> turning radius and I suspect the final turning angle I get is a little over
>> 75 degrees total.
>> 
>> Much of this is limited by the 12" maximum travel of the Linear drive's RAM.
>> RayMarine wants the RAM connected out 10" from the center of the post which
>> results in a max angle of 70 degrees.    
>> 
>> I attached the ram at about 8" out from center to increase the turning angle
>> a little beyond the RayMarine max of 70 degrees.  If I went less than that,
>> I might get more throw, but the RayMarine said the wear rate on the RAM
>> would increase dramatically, not to mention that the average stresses on the
>> aft cabin wall where the RAM attaches would be much higher and could cause
>> the tabbing to weaken or break over time or in rough conditions.  The aft
>> cabin wall is very thin and not great structurally.  It's weakened by access
>> panel.  Hence the large backing plates to spread the load.
>> 
>> I've been documenting the process pretty carefully with lots of pictures.  I
>> made a CAD drawing file for the Linear drive backing plate that I sent to a
>> machine shop.  The backing Plates I used to sandwich the aft cabin wall
>> where the RAM is mounted are larger than those used by Scott or Allan.  I
>> didn't use a mirror polished plate like they did but would recommend it.
>> Mine is brushed finish because it was cheaper and would be ready quicker.
>> But I can have it polished later if I want.
>> 
>> The unit I installed is the RayMarine ACU-200 Sail Pack (p/n T70155) with
>> Type 1 Linear drive and Rudder Position Sensor to allow software control
>> over the Linear drive's turning limits.  
>> 
>> Edson sells a Tiller arm to attach to the rudder stock that is specially
>> milled for the C320 rudder post.  It's a nice piece but needs to be
>> shortened slightly to give enough clearance on the C320.  Also, you'll need
>> to drill the rudder post.  I used a high quality Dewalt bit dipped in ALUMET
>> 872 cutting oil before I started and with my cordless drill, I was done in 2
>> minutes with a few 6" long coils of SS cuttings.  Rather than drilling all
>> the way through the post and thru-bolting it, I drilled a 5/16 hole and
>> tapped it for a 3/8 coarse thread high strength stainless bolt.  I believe
>> this is sufficient. 
>> 
>> Edson also sells a Rudder Stop kit that (P/N: 862-WIRE) (mentioned earlier)
>> that replaces the bump stop system used by the C320 in favor of a cable stop
>> with rubber shock dampener used in newer installations and larger boats.
>> 
>> For mounting the Rudder Position Sensor, I made a simple wooden unit that
>> clamps around the rudder support tube, therefore is already angled the same
>> as the rudder post and is height adjustable for perfect alignment with the
>> tiller arm.  I'll be working up an illustrated article for the website that
>> others can also use for a reference but will be happy to discuss it with
>> anyone starting the project before the write-up is done.
>> 
>> -Jeff Hare
>> 
>> -----Original Message-----
>> From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf
>> Of Graeme Clark
>> Sent: Wednesday, September 16, 2015 11:58 AM
>> To: C320-List at Catalina320.com
>> Subject: [C320-list] steering geometry question
>> 
>> I'm 250 miles from my boat and planning a below deck autopilot installation
>> so would like to know approximately what is the angle or travel for the
>> rudder (degrees either side of central) and the approx diameter or the
>> rudder quadrant, so I can calculate the actuator throw I will need and where
>> to connect it to the quadrant (or possibly make up a new radius arm
>> 
>> Anybody have those figures to hand by any chance? Doesnt have to  be that
>> accurate at this stage
>> 
>> Thanks
>> 
>> Graeme
>> 
>> #366, Mk 1, Jaskar.=
>