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Frank 101 · 18-12-2019, 18:46

Joshua Slocum’s book, from memory, says that once the sails were set the boat found its own way without outo pilot. I think he said the tiller was immobilised, but not sure. The boat seemed to find its way to where he was going even without the auto pilot, so can someone please explain why boats today need auto pilots?

DeepFrz · 18-12-2019, 19:13

Best way to understand why you want an autopilot is to take your boat out and set the sails and the course and see what happens.

bobnlesley · 18-12-2019, 19:29

To be fair, I don't think that Slocum's Spray sailed itself all the time, one of my recollections from the book is of JS claiming that the ghost of someone (a Pilot?) from Columbus's crew also did some steering for him too.
In certain conditions we can and have managed to get our yacht to self-steer for extended periods, so why don't we do it all the time rather than use the windvane or autopilot? Because we sail across 'real' oceans, not the pages of a book; I think the term's 'poetic licence'

chrisr · 18-12-2019, 19:57

obviously it is to do with the fin & skeg design commonly used today, versus the long keel / body shape of "Spray". this hull form tracks straight quite well, but is slower (due to more wetted surface) and does not turn as quickly

btw, I'm sure he lashed the helm too...

cheers,

**Lepke** · 18-12-2019, 20:07

Quote:

Originally Posted by DeepFrz

Best way to understand why you want an autopilot is to take your boat out and set the sails and the course and see what happens.

ditto

Frank 101 · 18-12-2019, 20:07

Thanks for the responses. Quite happy to have the Holy Ghost on board, but I’ll pass on any other type thanks Bob! I’ll reread his book again as it was quite interesting - and keep a lookout for the ghost.

**tkeithlu** · 19-12-2019, 05:52

It is possible to "balance" a boat, given the right course and a reasonable hull. You can do it with trawlers as well. But not many boats today have hulls that are sluggish (for lack of a better term, I don't know what a naval architect would call it) enough to return to course after every wave. In fact, you can feel it in the autopilot - it needs only very small rudder inputs to hold course under most conditions. I suspect that I and others actually oversteer to a degree.

The Spray's hull, not counting the long bowsprit, was very flat bottomed with a beam to LOA of 1:2.3, unheard of today in even a full displacement trawler (mine is 1:2.9). Her keel was full length, but very shallow. At least one architect has proposed that she was likely lost because of deficit ultimate stability, which I can imagine looking at the model on my bookcase. I doubt she was good upwind, and that short of a capsize she must have been very stable. Hulls just aren't like that anymore.

thomm225 · 19-12-2019, 06:52

As was said earlier, take your boat out and try letting it sail itself.

My boat which has a full keel will sail itself for a while when sailing upwind.

It will at times when there is a wind lifting gust head up a bit due to the main getting powered up but then after the gust passes it will fall off the wind again and come back on course.

It will do this usually until there is a decent change in the wind speed or direction.

Downwind is a different story and it doesn't do as well.

Robin Knox-Johnson during the 1968 Golden Globe Race said his 32' sailboat Suhaili would steer itself also for extended periods when his dual windvane autopilot failed

https://www.classicboat.co.uk/articl...suhaili-words/

chris95040 · 19-12-2019, 07:56

Quote:

Originally Posted by thomm225

My boat which has a full keel will sail itself for a while when sailing upwind.

I've spent a lot of time sailing boats like yours. I'd say this capability is often overstated by owners. Any kind of sea state is going to throw you off course in a hurry. We remember those times when conditions were awesome and the boat seemed to sail itself, but it's a fair weather friend. Not for the conditions where you are truly wishing you had a self steerer!

Your boat does not have a full keel, btw. It has a cutaway forefoot keel. According to some this cutaway does help with wave action driving the bow off course. I've never helmed a true full-keel so I'll take folks word for it on that difference, though it makes sense to me. Even so, with my cutaway-forefoot keel, I still need the auto pilot for anything more than a quick tinkle.

Caveat being, the better of a sailor you are, the more capable you'll be at getting the boat balanced. I'm a pretty mediocre sailor.

Quote:

Originally Posted by thomm225

As was said earlier, take your boat out and try letting it sail itself.

Yeah - that's the best advice. Lots of folks even add feedback to the system with hitching a sheet to the tiller, definitely fun stuff to experiment with.

thomm225 · 19-12-2019, 08:39

Quote:

Originally Posted by chris95040

Originally Posted by thomm225 View Post
My boat which has a full keel will sail itself for a while when sailing upwind.

I've spent a lot of time sailing boats like yours. I'd say this capability is often overstated by owners. Any kind of sea state is going to throw you off course in a hurry. We remember those times when conditions were awesome and the boat seemed to sail itself, but it's a fair weather friend. Not for the conditions where you are truly wishing you had a self steerer!

Your boat does not have a full keel, btw. It has a cutaway forefoot keel. According to some this cutaway does help with wave action driving the bow off course. I've never helmed a true full-keel so I'll take folks word for it on that difference, though it makes sense to me. Even so, with my cutaway-forefoot keel, I still need the auto pilot for anything more than a quick tinkle.

Caveat being, the better of a sailor you are, the more capable you'll be at getting the boat balanced. I'm a pretty mediocre sailor.

Originally Posted by thomm225 View Post
As was said earlier, take your boat out and try letting it sail itself.

Yeah - that's the best advice. Lots of folks even add feedback to the system with hitching a sheet to the tiller, definitely fun stuff to experiment with.

Well maybe so but when I did try letting my "full keel" boat sail itself it does pretty good.

Btw, I refer to it a full keel boat because it's simpler than going into the cutaway description since that's pretty much understood anyway as there are very few straight up full keel boats out there these days.

Also usually when the wind is up a bit my boat is being steering by one of my two autopilots.

Like I said before my boat does pretty well sailing itself upwind until there is a decent change in the wind speed or direction.

Winds were gusting to 29 knots and shifting around quite a bit in the video below and even with the small amount of jib I had out the autopilot was still struggling at times to keep up. (the furler was also jammed and I couldn't bring in or release more sail) I dropped the sail when I got into my creek 4 hours or so later then repaired the furler at the dock. The tough part was coming out into the bay on a reach in those winds and waves first thing

It may have been a bit easier if I was out in the ocean with more widely spaced waves, but I was in the bay

You can hear the autopilot working at the start of this video to bring the stern back into the wind.

More autopilot action in the second video. Wind came up as soon as I pulled anchor and kept on building. I was home in 3 hours from almost 20 miles away. I had the tide also. It's taken 5 hours at times in the past

https://www.youtube.com/watch?v=agtdrmAqojs

https://www.youtube.com/watch?v=Ejcp-rCYz3U

Orion Jim · 19-12-2019, 12:55

Quote:

Originally Posted by thomm225

Well maybe so but when I did try letting my "full keel" boat sail itself it does pretty good.

Btw, I refer to it a full keel boat because it's simpler than going into the cutaway description since that's pretty much understood anyway as there are very few straight up full keel boats out there these days.

I also have a full keel boat and I’ll let those with the inclination argue about the “cutaway forefoot”.
I have found that I can close reach in moderate seas for hours on end as long as the boat is balanced and isn’t tugging at the helm.
I was caught by a full gale in the Gulf Stream a few years ago when returning from Bermuda to my home port. My Monitor windvane did all the steering, I just reduced and trimmed the sails as conditions dictated. Sometime after 4AM as the storm was abating I set my alarm for 30 minutes. When it went off I looked aft and found that my air vane had departed for England and I was still close reaching comfortably. I just kept checking the rig regularly and let her sail herself until noon when the seas had dropped to the point where I was able to get the main back up. I replaced the missing air vane and resumed my normal routine.

sailorboy1 · 19-12-2019, 13:33

its kind of a silly thread question IMO

any boat will "sail itself" in the right conditions with proper trim and balance

My deep fin keel with spade rudder boat when trimmed correct only has a couple degrees of rudder. How much steering you think is needed?

Dusty Mac · 19-12-2019, 14:41

I have a 70's quarter ton sloop, that I regularly let steer herself (Upwind only). Longest has been 18 miles from Naniamo to Vancouver in 12 kts of wind and the most wind was 35kts with just the blade - no main Balanced perfectly. I do clip in when single handing.

Reefmagnet · 19-12-2019, 15:07

Last week, I was sailing hard on the breeze in 25 knot winds, against the tide, and a couple of times we got hit by larger waves that pushed the whole boat to leeward by about 15 degrees or so. I find it difficult to imagine any vessel maintaining a true course in any sort of seas for any extended length of time.

I wonder if Slocum used something like sheet to tiller steering for directional control?