Below Deck Autopilot C34 Mk2

[Graham]

INSTALLATION OF A 'BELOW-DECK' AUTOPILOT ON A C34 MKII

Equipment Purchased
•   1x Raymarine Evolution short shaft Autopilot system – product #T70158
•   1x Raymarine Rudder Reference Transducer – product #M81105
•   1x Raymarine Seatalk1 to Seatalk NG conversion kit – product #22158
•   1x Edson Tiller Arm – product #926-10-610MKII, bored to 2.86"
•   4x Catalina polished flush-head drive mounting bolts – product #000531

I purchased Smooth Jazz (1997 C34 MkII, hull #1376) in August 2004 as I thought it superior to many European yachts in that price range. After 16 years, I still hold that view.  However in 2004 it came with an unreliable wheel autopilot and basic electronics.  In 2005 I had all navigation electronics replaced with Raymarine equipment.  I chose Raymarine because I have used them or their forerunner (Autohelm) since 1992 and enjoyed good service and reliability.  The wheel pilot I chose was the ST4000 Mk2 model which was the strongest of Raymarine's wheel pilots; recommended for vessels up to 18,000 lbs. displacement; so should have been fine for Smooth Jazz at 12,550 lbs.   

Smooth Jazz is based at Chichester on the South Coast of England and makes an annual voyage across to France and along the North Brittany coast; the voyage being approximately 500 miles.  On many of these voyages, I encountered complete or partial failure of the ST4000 autopilot resulting in repair or replacement.  In the summer of 2014, I again encountered a failure that required the unit being replaced.  It was at this point that I decided to go for an up-grade, which meant a below-deck system.

After taking measurements in the aft lazerette, I found that I had insufficient space for the smallest below-decks Raymarine autopilot; this being their Evolution 'short-shaft' linear-drive system which was good for displacements of up to 24,000 lbs.  The drive unit needed to be mounted on the strongest part of the stern, that being the underside of the aft boarding platform.  The problem was that the aft water tank prevented full movement of a tiller arm (required for a below decks systems) when turning the boat to port.  The only solution I came-up with was to have a section of the water tank cut away so that the tiller arm could move freely.  The water tank would in any event, need to be taken-out in order to work on the rudderstock and the underside of the boarding platform.

With some trepidation, the project began and the following is my programme of installation:

a) Clear the decks: Removed all bedding and cushions from the aft cabin along with the aft wooden panel that traverses the cabin.

b) Cut the water tank: A 'cutting line' was drawn on the water tank sufficient to provide free movement of an Edson tiller arm.  The water tank was then removed and sent to a specialist polypropylene fabricator.  The re-fabricated tank was back in two weeks; I believe I have lost less than three gallons in capacity.

c) Edson tiller arm: Product #926-10-610MKII, bored by Edson to 2.86". This was positioned just below the Edson steering radial drive-wheel.  Integral clamp bolts were then tightened so that tiller arm was 90° starboard of the rudder position.  Once absolutely sure we had the correct angle, the rudderstock was drilled and the tiller arm clamped and bolted.   

d) Raymarine linear drive: The drive (product #M81130) was positioned on the starboard underside of the aft boarding platform so that the drive arm made a 90° angle to the tiller arm.  Whilst there are a number of connecting holes on the tiller-arm that can be selected for the drive arm to attach, we wanted to position it towards the outer ones in order to obtain maximum leverage.  Once a 90° angle was established, holes were then marked and drilled in the platform and the drive unit bolted with the Catalina Flush-head bolts – product  #000531.
   
e) Raymarine Actuator Control Unit: Product #E70099 was installed under the heads sink unit.  Taking-out the locker doorframe provides better working access to install the ACU.       

f) Raymarine Sensor Core: Product #E70096 was positioned in the starboard locker forward of the Holding Tank as we wanted to keep it clear of any electro-magnetic interference.  Looking back, I think we were a bit over-cautious and this could have been installed below the heads sink along with the ACU.   

g) Install the Control Head: Product #E22166 merely was a replacement for the old ST60 control head used on the ST 4000 wheel unit.  The STNG Adaptor Kit product #E22158 was installed within the instrument pod and is a simple 'plug and play' unit.

h) Rudder Reference Transducer: In addition, we used a Rudder Reference Unit Product #M81105 which while not essential, is recommended by Raymarine.  Unfortunately, I did not find anywhere suitable to mount this, so I had to screw and glue a piece of marine ply to the underside of the cockpit deck; not great to look at, but it works and is out of sight below decks.   

The Raymarine Evolution System #T70158 includes the drive, ACU, sensor core and control head.  The system has a simple to use, dockside set-up procedure and hence it was soon working.  Once we were satisfied with its operational status, we inserted and re-strapped the modified water tank along with the aft panel in the stern cabin; lastly a beer or two.

Five seasons later, I am extremely pleased with this Autopilot, as it is silent, reliable and simple to use.  In 2016 my son-in-law (who also had a C34 MKII), installed the same system.   Shortly afterwards he did a round trip of 3,000 miles from Chichester, UK to The Canary Islands off North Africa and was pleased with its performance.

Anybody interested, the original article inclusive of photos was featured in Mainsheet magazine Vol.36, No.4 Winter 2018 - I can also email article with photos.

[Stu Jackson]

Thanks for that great report.  Please consider sending that article to our Technical Editor, John Nixon  (c34hull728@gmail.com), for a Mainsheet technical article.  I think many would be very interested in the text and photos.

[Graham]

Stu,

This was in fact an abridged version (minus photos as I do not know how to upload them) of an article that I wrote for Mainsheet Vol 36, No.4 Winter 2018.

By the way whilst this might sound a big job, once you get into it, it is of course a number of small simple tasks.

Perhaps you could help me, I am replacing the engine vents + ducting + blower and at first sight looks a fiddly job (head down the lazerette working 90 degrees) that I know will result in some colourful language.  Reason for replacement is existing hoses breaking-up, blower making a screeching noise and high revs sees black smoke.  Do you know of anyone who has done it as there must be a simple way.

Graham

[Stu Jackson]

Sorry, I forgot that article, thanks.

No I haven't heard of anyone replacing the blower, or even the hoses.  Since I have been in cool waters in San Francisco, and even cooler ones here in BC, I have never used my blower.

Perhaps some of our skippers who sail in warmer climes might be of assistance.

PHOTOS:  Posting and RESIZING Photos 101  http://c34.org/bbs/index.php/topic,3701.0.html

You can go back to your original post, under modify, and add them.

[pablosgirl]

Hi Graham,

I replaced my bilge blower about 7 years ago.  I have a MK-I boat (1988) so I am not sure they use the same blower.  Mine was located just bellow and slightly forward of the engine control panel. I was able to remove the engine control panel and use that hole to gain access to replace it.  I found a replacement on defender.com. 

My blower hoses were in good shape and I did not replace them.  There is a hose that runs from the blower to the port aft vent cowl and the other hose routes under the aft water tank and around the fuel tank support structure to the bilge area at the shaft log on the MK-I boat.  Not sure how the MK-II is plumbed?  I would imagine that you would need to do some boat yoga to get into the aft locket to gain access to the cowl connection.  I think that you could do the bilge hose by connecting the new to the old in the space under the aft berth and having a helper pull the old vent hose through the engine control panel opening while you feed the new vent hose aft. I have done the boat yoga thing to get into this aft space to replace the wiring for the wheel pilot which is mounted through the cockpit wall in this area.

Hope this helps.

Pablo

[Graham]

Thanks Pablo,
Have now replaced whole system and yes I did connect new to old and pulled it through.  I also repositioned engine-end of duct at top of engine compartment, via locker below sink in heads.  I thought the original design of positioning the inboard outlet opposite the inboard inlet was not good as it merely expelled the fresh air.

Graham

[Admiral_Swellson]

I can't find the referenced (above) Mainsheet issue in the archive?  "Mainsheet magazine Vol.36, No.4 Winter 2018"

Does anyone have a PDF?

[Graham]

Please see attached pdf copy - hope this helps.

[Admiral_Swellson]

Thank you very much Graham!

[Stu Jackson]

Thanks, Graham, for posting that PDF.

I added this thread to the 101 Topics.

For all of you, here's how to access the magazine online.

Mainsheet magazine Access 101  https://c34.org/bbs/index.php/topic,10797.msg84337.html#msg84337