Autohelm ST 4000 Tiller pilot

[Peter Foston]

I have now had two pilots develope severe vibration in the telescopic ram. This means that the whole of the longer part of the outer tube (ie not the drive unit) has to be replaced as my dealer says it can not be opened up for repair.
I have two possible causes.
1. Allowing the ram to try to push beyond it's limits due to inadequate sail trim to overcome weather helm
2. I do a lot of motor sailing and find that when motoring hard the tiller starts vibrating very rapidly .
Has anyone else come up with this problem?

If so my e mail address is on the members list
Peter Foston - Khamis

[blueprintbill]

Peter,
I have had the Autohelm 2000 (?) or 4000 (?) for maybe 10/12 years now. I'm not sure which number is correct for my unit(s). I have a complete backup unit that has never been used. I did have a control head problem 3 years ago, where the the readout head broke or was injured and nothing was visible. The unit worked just fine steering the boat but it was like operating it in the dark. I took it off and sent it in and had it fixed over one winter season while in Sweden.

My push arm units are the GP version ( Gran Prix -?) and they are supposed to be good for a boat up to 20,000 pounds (as opposed to 14,000 pounds for the straight 4000 unit). I've never had any problem with the push arm after all this time, many miles and a partial usage on a transatlantic crossing.

I did have a similar issue with vibration of the rudder/tiller assembly, and I alleviated the problem somewhat by enlarging the propeller aperture a little, I think at the upper side if I remember correctly. Check to see that you have a similar distance between the propeller tips top and bottom.
Dave Gerr in his book 'The Nature of Boats', Chapter 34 states that there should be a clear distance -a tip clearance- between the hull and the propeller blade tips of at least 10 percent of the propeller diameter. And he says that that should be a bare minimum, with 14 to 18 % the 'standard ideal'. This issue has to do with propeller vibration more than rudder vibration but there may well be some interaction/ relationship. Poor aperture fairing, especially that around the rudder should also be looked into as well.

In addition to the above I also find that some tiller vibration (and consequent noise) can be alleviated by building up the two vertical surfaces of the tiller itself with upper and lower multiple layers of a good quality plastic tape,so as to provide a more snug and somewhat cushioned fit between the tiller and the stainless 'shoe' it gets inserted into. The tape may wear out, or move around a bit over time, but I find that as I put a coat of varnish on my tiller every year, I also renew the tape job at the same time. Its by trial and error. You keep adding tape until the fit is 'right', allowing reasonable movement of the tiller in and out, and up and down, but much less 'slop' or 'rattle' side to side.

Questions? Feel free.
Cheers, Bill

[Peter Foston]

Thanks Bill
I think you have the 4000 as the 2000 had a compass as the control head whereas the 4000 a rectangular flush mount..
I spoke to Raytheon and it appears the GT mod is only in the power drive (ie the short section of the tube) the telescopic part is the same. They did however suggest that to stop the unit surging against its extension stop I reduce the factory setting for "Turn" down from 20. I have gone to 16 and this helps.
None of this relates to vibration however. I hear what you are saying about prop aperture as I did this on a Liz 29 that I had prior to my Nic for 24 years when I increased the prop size.. How come that I have a standard prop albeit repitched from 18x13 to 18x11 which completely cut out "Sooty transom syndrome" . Hence my asking if others get this vibration which ocurred before the repitching. If others don't why me?
A Yanmar dealer that I respect has suggested that changing to a three bladed prop might help as the two blade is intermittently masked by the deadwood as it turns.
As my tiller was delaminating when I bought the boat I made a new one to fit the SS socket and this is always bolted up tight.
Doea anyone else out there have "Tiller Vibes"?
Peter

[Peter Foston]

Bill
Eureka!!! I have solved the problem of damage to my autopilot rams due to tiller vibration.

I was using an 18 ins two bladed prop and on checking found that I only had 3/4 ins clearance over the top of the blades. This must have been causing severe cavitation. Add to this that with two blades, one moment they are screened by the deadwood and the next out in open water.

Solution :- I have fitted a 16ins three bladed prop. The vibration has completely gone and the sound level has dropped right away. I am getting slightly higher fuel consumption 1.6 l/hr whereas before it was 1.4 but I suspect this is because I can run the engine at slightly higher revs without shaking the boat appart!!!

[SailingCirce]

That's interesting. What is the pitch of the new prop? Is there more drag and decrease in speed while underway under sail power only with the three blade?
Harrison

[Peter Foston]

My original prop was 18x13 ins which was over pitched and giving me a sooty transom. This was repitched to 18x11 which cured the soot problem but did nothing for the vibration.
Last winter I checked with my Yanmar dealer and a local engineering firm that specialises in props and stern gear saying I wanted to go to three blades with 16 ins dia.
I considered making it 17 but could not be sure if this would have given enough clearance to get rid of the vibes.
They both came up with the same answer for a 16 ins dia. I am afraid I have mislaid the paperwork so until I haul out in October cannot give you the pitch - Sorry!

If you go to a reliable company they will ask you for details of YOUR engine’s performance data and then go into a computor program to give you the pitch.

If you are in the UK I use C&O Engineering from Newton Abbot, Devon Tel 01626367782.

The boss is Martin and they are a small company but I have used them for many years and they are reliable and reasonably priced.

All I ask is that if you only intend use them to give you the spec but do not intend to buy from them P’se dont mention my name!!!

As to drag I am not a racing man so am not really aware but after all you never can tell with a two blade if it is hidden behind the deadwood or sticking out. I may have lost a little speed under power but the lack of noise and vibration is ample compensation if I have.
My engine is the original Yanmar 2QM20.
Peter

[dubhe]

Harrison,

Last winter, we replaced our original 2QM20 and 18 by 13 prop with a new 3YM30 and Variprop feathering propeller (3-blade 16 by 11). Once the engine had been run-in, I checked full throttle performance, which gave 3,800 rpm. This confirmed my suspicion that it had been under-pitched (the dealer quotes full throttle performance as 3,200 to 3,600). According to the Variprop manual, increasing the pitch by 1 inch should decrease rpm by 200 - I'll check it out next season. Like Peter, we have found a marked reduction in tiller vibration.

Geoff

[Peter Foston]

Harrison
Further to my message of 7 August, Khamis is now out of the water and I have checked my prop and confirm that it is a 3 blade 16" x 11" and I am delighted with it!
Peter

[blueprintbill]

I got caught out, singlehanded, coastal cruising through Maine's rock garden, Muscongus Bay last fall, with only mainsail up in 25 to 30 knots, and Autohelm steering. There was very heavy weather helm under main alone, ( duh ) and the old Gran Prix pushrod motor ceased functioning. In a bit of a panic I pulled out my 10 to 12 year old unused spare and to my great relief found that it was indeed the pushrod that was broken. I've just received the repaired pushrod back from Autohelm, after 10 day turnaround with the bill for $450 for a new GP motor. This unit has seen thousands of hours of use, steering the boat maybe 95% of the time it's underway, so I can't complain. I am just thankful Autohelm was still able to repair it. Cudos to a great product.

Bill

[ianstone]

Hi Guys
I have just noticed this thread on Tiller pilots.
My AutoHelm ST4000 has been playing up all season. I have reset it three times to no avail.
In desparation coming back from Alderney in dead calm conditions I again tried resetting it, and fiddling with the buttons. I got it to work for an hour before it threw the boat 90 degrees and kept on turning. Never to work again.

Has anyone any idea what this could be down to before I spend money on a three year old system that has only worked for two seasons.
Cheers
Ian