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-   -   Can someone please explain "sea state filter" (https://www.cruisersforum.com/forums/f2/can-someone-please-explain-sea-state-filter-187127.html)

gamayun 01-07-2017 23:08

Can someone please explain "sea state filter"
 
The manual says that it is used "to reduce rudder activity and Autopilot sensitivity in rough weather." This seems counter to what you'd want to do in a heavy sea state. I also don't understand the difference between AUTO (which apparently works as an adaptive process) and MANUAL (which is linked to steering response to manually find the optimum combination of course keep and low rudder activity). This is a new AP and my boat s-curves in higher winds and sea state so I was going to increase the gain but now wondering about this filter and what it does.

JPA Cate 02-07-2017 00:26

Re: Can someone please explain "sea state filter"
 
In heavy sea states, our autopilot, too, works harder than we would steering, especially off the wind. If you imagine yourself in, say 15 ft. seas, with the commensurate swell running, you are better able to keep the boat running on course by NOT turning the wheel, keep it centered--or almost so, and you feel the changes coming as the wave picks her up and as she starts to surf, then, as she slows, and quits surfing, your feet, legs, and the backs of your ears tell you what's happening. The autopilot can't do that, but, if you let it reduce the rapidity with which it introduces large changes in rudder angles, that will help reduce the radii of the "esses."

If you increase its sensitivity, the radii of the curves on the "esses" will increase. So, the sea state adjustment makes it less hyperactive.

Hope this helps.

A.

Neptune's Gear 02-07-2017 00:26

Re: Can someone please explain "sea state filter"
 
What is the AP? Sea state filter is to try to minimize rudder movement when heading is being cyclically changed by waves (no need too move the helm). Also related is "counter rudder" which is how much helm to apply to stop a turn already in progress, before returning rudder to center.
Have you run through both the dockside and the sea-trial setup procedures for your AP, as shown in the manual?

gamayun 03-07-2017 23:33

Re: Can someone please explain "sea state filter"
 
Ann, that explanation helps a lot! Thank you. I think I'll change sea state filter before upping the gain just yet.

Neptune, the AP is Simrad AC42N with the RC42N fluxgate compass. Everything is new. I ran through both the dockside and sea trial, but during the sea trial, it never finished its S-curving before I ran out of sea room. This was also after at least 7-10 minutes of waiting for it to finish. It seemed to work fine, as far as I can tell, but perhaps I should go back through that when I'm more out in the open.

gjordan 04-07-2017 07:44

Re: Can someone please explain "sea state filter"
 
gamayun, good advice on the posts, but remember that an auto pilot is much like a windvane, in that there is a learning curve to its operation that only will come with time at sea. You will get better and better with more experience. First experiences with an autopilot or vane can be discouraging, but it will get better. Good Luck. ____Grant.

gamayun 04-07-2017 09:46

Re: Can someone please explain "sea state filter"
 
Quote:

Originally Posted by gjordan (Post 2426553)
gamayun, good advice on the posts, but remember that an auto pilot is much like a windvane, in that there is a learning curve to its operation that only will come with time at sea. You will get better and better with more experience. First experiences with an autopilot or vane can be discouraging, but it will get better. Good Luck. ____Grant.

Great...I just installed a Monitor, too, and haven't trialed it at all. I guess I'll have time to play with them both now as I'm heading offshore in the morning. Back in 4-7 days.

Blue Stocking 04-07-2017 10:25

Re: Can someone please explain "sea state filter"
 
Torque from prop may require sensitivity change when going from sail to motor. Had this problem on a friend's CSY 44.

gjordan 04-07-2017 13:28

Re: Can someone please explain "sea state filter"
 
gamayon, I have not used a Monitor, but tomorrow morning I am driving up to Redding to pick up my third Aries. My first one was on a boat that I bought. I already had 8 or 9 thousand miles on a smaller boat with a different brand of windvane, but the Aries still took a fair amount of getting used to. My first few times with it I thought it was horrible but after 1000 miles I loved it. They all take some getting used to, but I consider a windvane the most valuable piece of gear on a cruising boat. Be very careful about your autopilot and transmitting with a SSB/Ham radio. I bought a bunch of charts from a fellow that had his trip of a lifetime ruined because his autopilot packed up 3 days out of Mexico and he had to turn back for repairs. After waiting 30 days for parts he took off again and 3 days out it blew again, but this time they made the connection with a ham radio net that they were checking into. Back to Mexico and another wait and they were so late that they gave up on the South Pacific. Just yesterday I was reading on another forum that SSBs can sometimes blow fuses or worse on autopilots. Probably not all brands but it is a worry. Have a great learning experience and let us know how your trip goes. _____Grant.

Stu Jackson 04-07-2017 13:48

Re: Can someone please explain "sea state filter"
 
This is old, but covers some of the basics. What's changed since it was written are the smarts of the units and their power.

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maxingout 04-07-2017 14:21

Re: Can someone please explain "sea state filter"
 
Some hulls designs have less directional stability and the sea state filter may be more important to them.

Our catamaran has relatively deep fixed keels and massive directional stability. I never had to adjust the autopilot for sea state because our cat sailed like it was on railroad tracks.

JPA Cate 04-07-2017 14:28

Re: Can someone please explain "sea state filter"
 
Quote:

Originally Posted by gjordan (Post 2426778)
gamayon, I have not used a Monitor, but tomorrow morning I am driving up to Redding to pick up my third Aries. My first one was on a boat that I bought. I already had 8 or 9 thousand miles on a smaller boat with a different brand of windvane, but the Aries still took a fair amount of getting used to. My first few times with it I thought it was horrible but after 1000 miles I loved it. They all take some getting used to, but I consider a windvane the most valuable piece of gear on a cruising boat. Be very careful about your autopilot and transmitting with a SSB/Ham radio. I bought a bunch of charts from a fellow that had his trip of a lifetime ruined because his autopilot packed up 3 days out of Mexico and he had to turn back for repairs. After waiting 30 days for parts he took off again and 3 days out it blew again, but this time they made the connection with a ham radio net that they were checking into. Back to Mexico and another wait and they were so late that they gave up on the South Pacific. Just yesterday I was reading on another forum that SSBs can sometimes blow fuses or worse on autopilots. Probably not all brands but it is a worry. Have a great learning experience and let us know how your trip goes. _____Grant.

We had that problem with an old autopilot. Jim found a way to fix the problem. It is the RF that gets into the AP's simple "mind." A PM to Jim would get you the information, if you still are interested.

Ann

Sandero 04-07-2017 14:46

Re: Can someone please explain "sea state filter"
 
If the boat is moving about the AP will try to correct to keep it on course. For one this uses more power and the AP usually cannot make the correction on the helm that a person can because AP usually has a limited range for stbd of port corrections. My heklm can do 2 full rotations... from center helm that would be one rotation to stbd and one to port. The AP can maybe turn the helm half a rotation which is fine... for holding a straight course or for a basic turn. I can tack but it's not on a dime.

The damping or filtering limits minute course corrections and saves electricity... likely limit S-ing doing downwind in quartering seas.


Playt with the settings to learn your AP's characteristics.

Cheechako 04-07-2017 15:04

Re: Can someone please explain "sea state filter"
 
An AP may steer too often, in rough seas ...by the time it feeds back how it's doing to itself it needs to correct the other direction, beginning a cycle of zig zags, overheating, etc.

gamayun 04-07-2017 20:34

Re: Can someone please explain "sea state filter"
 
Grant, good to know about the SSB issues with APs and the break in period that I might need for the windvane. I have not yet installed my SSB yet so will not have to worry about that. Just motoring over to the central SF Bay this evening, and I can already tell there's going to be a learning curve and some adjustments to make.

Sandero et al, I appreciate the extra info. I definitely going to make filter adjustments first and see how that goes. Anything to leseen power load and the potential for burn out is particularly good info. I'll post an update when I get back. My track, if you should be so interested, should be posted on sfbaysss.org.

gamayun 09-07-2017 13:33

Re: Can someone please explain "sea state filter"
 
Maybe this should go in the "Confessionals" thread, but I pulled out my handy instructions about 20 miles offshore and realized I can't make AP adjustments with the boat moving even though I had put it on standby. That was a dumb moment of realization. It turned out, however, that the AP performed phenomenally with big sea state and winds. At one point, we had sustained 26-28 knots with gusts over 30 knots and a 8-10-foot beam on swell. The AP held so well that I only steered once and decided it was doing a much better job. I'm now thinking that the s-curving I'm getting in the bay might be when I'm over-canvassed I don't reef early inside even when it's blasting above 20 knots. I was on my second reef in the above conditions and better balanced. So much yet to figure out! I still plan to play with the sea state filter to see how that changes things. As long as I remember to do it before leaving the dock :facepalm:


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