[C320-list] Linear autohelm

[Jeff Hare]

You're probably all overthinking this a bit too much. The EV200 package handles the C320 beautifully and effortlessly in all the sea conditions we sailed in.  The c320 has a light responsive helm. The boat displacement is considerably under the max for the type 2.Big following, quartering, slightly off the nose, just fine. The tail gets kicked around a bit in following/quartering seas but hangs on just fine.  In huge crazy seas, we are hand-steering anyway. If you're crossing oceans it may be another conversation.  Linear drive type 2 electric is the way to go for sure. Hydraulic systems are more expensive and will provide no tangible benefit over electric.  Plus, if it fails you could replace it with a spare in minutes with just a screwdriver.Regarding the aft wall thickness, absolutely it is not strong enough to just bolt the foot to.  But the stainless and aluminum plates we sandwich the wall with completely solve that problem.  Regarding the tiller arm length and clearance to the aft cabin wall, that problem is also easily solved properly without either overloading the linear drive or reducing the C320's awesome steering radius by much.I doubt you'll find anyone with the EV200 installed this way who isn't fully satisfied with its performance.We have a full photo gallery with install pics and measurements.I've have seen one early installation with the ram off the transom back behind the fridge compressor and it looks like it makes the locker tricky to access and less suitable for storage.Jeff
-------- Original message --------From: Greg Arnold <greg-arnold at gmx.com> Date: 8/21/22  2:15 PM  (GMT-05:00) To: C320-List at Catalina320.com Subject: Re: [C320-list] Linear autohelm    On 8/21/2022 9:25 AM, Stephen Cox wrote:   On 8/20/2022 11:33 PM, Stephen Cox wrote:>From the relevant Mechanical Linear Drive manual the Type 1 LinearDrive is rated at 18-36 W and the Type 2 Linear Drive is rated at 48-72w. Note the minimum of the Type 2 is greater than the maximumof the Type 1.  What makes you think t he ACU-200 willhappily drive this without letting the magic smoke out thatpowe rs all electronics?  Even assuming it manages for awhile what happens when you get into strong sea and windconditions?  The power consumption will go up and a gain, themagic smoke will escape the ACU-200 and it will stop working.   Comment:  Would be a problem if you were on a Cat 470.But on a 320   you shouldn't be drawing much juice -- about the same asif you had an   ACU-200 and Type 1.The load might be relatively light but the build of the Type 2 motor indicated by it's ratings is such that it appears to draw morecurrent with a light load than the Type 1.  A rating of 48-72w indicates to me that it will draw a minimum of 48w when operating.That is 12w more than the Type 1 maximum or 33.3% more than the maximum rating. Does the ACU-200 have that much safety margin?What about when the Type 2 encounters conditions that make it draw it's full 72w or 100% more than the Type 1 can draw.  Does theACU-200 have the ability to handle double the expected maximum load?  Could be an expensive exercise if the ACU-200 burns out.   -   According to Jefa here:   -   [1]https://www.jefa.com/steering/products/drives/qanda.htm   -   "More modern autopilots are able to control the speed of the autopilot   drive unit from 0 to 100% without any steps via so called pulse width   modulation. To be able to vary the power sent to the drive unit, they   don't sent a continuous signal, but pulses, and by adjusting the width   (duration) of the pulse from zero to hundred percent they can   accurately control the speed of the drive unit."   -   I believe the Raymarine uses pulse width modulation.   -   Pulse width modulation sends many short pulses of electricity each   second.  A bigger motor (such as the Type 2) will draw more   electricity, but will draw shorter pulses.  Thus, the ACU will be   working harder when it is sending electricity, but will be resting more   often.  Every second, the ACU should be sending about the same amount   of electricity whether it is powering a Type 1 or a Type 2.  The   question is whether the ACU-200 can handle the bigger but shorter   pulses.References   1. https://www.jefa.com/steering/products/drives/qanda.htm