Wheel Pilot Question: Displacement worries

[Debra B]

I am in the process of specifying an autopilot for my Hunter 37 cutter - displacement listed at 17,800 pounds. I have added a lot of heavy options to this boat. (Such as six 6-volt batteries in place of the standard, a newer/larger stove, etc.) Add to that Jerry cans of diesel, 1 of gas for the outboard, a small outboard, and dinghy, jerrry cans of water, canned goods, etc....The old wheel pilot I had - which recently died - seemed to be undersized. The new Raymarine ST4000+ MKII is listed at 18,700 pounds displacement. This seems like it is undersized for my boat and equipment. http://www.raymarine.com/raymarine/ProductDetail.asp?site=1&Section=2&Page=88&Parent=5&product_id=201 Raymarine WheelpilotI would be interested in hearing what other people have experienced. Since I single-hand my boat I need something I can depend on.My current thinking - subject to getting some information on rudder size to the Lewmar autopilot folks - is to use the smallest Whitlock/Lewmar direct-drive (chain driven) below decks drive motor coupled with the small Raymarine Smart Pack System. (See my other question on gyro-stabilized steering technology.) The boat had a below-decks pilot at one point because there is a seperate gear driven quadrant already attached to the rudder post, that's why chain-drive.... The small Lewmar motor is bigger than the small Raymarine motor and smaller than the big Raymarine motor (and yes, they do interface....) http://www.lewmar.com/webcat/html/steer_prod_view/drive_rotary_view.asp?measure=imp Lewmar Rotary DriveThe below decks option is a LOT MORE Expensive than the wheelpilot.... So I thought I should ask.... What have other people found on similarly sized boats? This is a med. disp. island hopper.(Not sure if the displacement numbers include the 80 gallons of water and the 40 of fuel the tanks hold.)

 

[Rick Sylvester]

I don't think displacement is the real issue

Yes, that's what most manufacturers use to 'size' their various systems, however, I believe that it's essentially a convenient yardstick from the marketing department so the 'average' boating public can get a handle on the choices available. Convenient, but a ridiculous over-simplification.Here's the questions I think you should be asking.How powerful and quick will the actuating mechanism need to be?This will be determined by how you'll be using the AP. Will you be using it to take over while you put up the sails or to grab a quick sandwich on a daysail? Is your helm balanced? If so, a wheel pilot will work just fine even on boats far exceeding recommended displacements.Can your boat generate significant weather helm forces on the wheel?Will you be making any extended passages when the AP will be an essential 'crewmember'?Will you be asking the AP to deal with significant following seas?If so, you'll need power and speed that a wheel pilot won't be able to develop. Even on a boat with far LESS displacement than the manufacturer recommends.How important is it to be able to continue to navigate should your steering cable break? Don't discount this. It's happened to three different boats on our docks in the past three years. Two were making entrance into inlets at the time. Two had wheel pilots and one had no autopilot at all. Each had to either immediately drop anchor or go to the emergency tiller. A below deck mechanism allows push button steering while dealing with the problem.Notice that most of these considerations do not have a direct correlation with displacement.Please know I'm not advocating a particular system or manufacturer, just suggesting that a displacement only decision may be throwing away dollars, saddle you with disappointing performance, or worse, contribute to an unsafe situation.

 

[jmcclain]

Autopiots!

Debra,Rick has summed it up very nicely. Our B321 displaces A bit over 11,000# and I am looking seriously at installing below deck pilot. The current ST4000+ is great as an extra hand in normal conditions, but there are times, even on the smaller B321, when it struggles to hold coarse. He has a great point about the possibility of cable problems. It happens more often than you might imagine. If cost is major issue, get the below deck pilot first, then add the gyro unit later.Jon McClain

 

[Debra B]

Thanks for the feedback

This is basically what I had decided... the wheel pilot is good on a good day, but on bad day, I would not be able to trust it.Thanks for the info, I will post something when I get the final specs settled with the Lewmar technical support folks.