Tiller Pilots


I have hovered over the acquisition of a tiller pilot for several years, once having even manufactured a mounting point for one.  I didn't install it.  Misgivings about its non-traditional complexion and fear of the siren-call of creeping complexity stayed my hand.

Last summer convinced me that cruising alone without one is inconvenient, and possibly more dangerous than accommodating the additional set of failure modes of yet another electrical gadget.

I decided to get a Ray Marine, and having done so had to choose between the ST1000 and the ST2000.  The additional push-rod thrust of the beefier model is appealing, but the clincher for me was the underlying technology.  The two models look nearly identical, but the ST2000 translates circular motion to linear push-rod motion via a recirculating ball drive.  According to Wikipedia:
Low friction in ball screws yields high mechanical efficiency compared to alternatives. A typical ball screw may be 90 percent efficient, versus 50 percent efficiency of an Acme lead screw of equal size
The lower-power ST1000 uses the less efficient lead screw push rod mechanism.  I have not found field reports that bolster the benefits of one over the other, so I'm acting on the belief that one is a more compelling engineering approach than the other.  More power for about the same current draw.

Installation required some custom engineering. Ray Marine sells various adapters to assure that the geometry of the installation can be matched with any given boat.  None of them seemed workable for Ripple's deck and cockpit configuration.  Layout measurements indicated that the pivot point for the fixed end of the device needs to be uncomfortably close to the aft deck cleat, and 8-9 inches above the deck.  The solution that I engineered is a stanchion designed to look as natural as possible in it's position on the port quarterdeck.

I laminated a block of oak from which to shape the stanchion using West System epoxy, wondering at this point if I could bring it to a pleasingly aesthetic, non-clunky shape.  The picture conveys the source of my misgivings:


I roughed out the block with a bandsaw and (mostly) a stationary belt sander, shaping it to something that seemed about right:


I filled gaps, coated the stanchion with some West System epoxy to improve durability, and smoothed the whole thing with 80, 180, and 220 grit paper.  Two coats of Brightside primer followed by three coats of Brightside white polyurethane finished the stanchion for installation.  Three brass threaded inserts, epoxied into the base, receive three stainless steel bolts screwed in from below-decks through a suitable backing plate.  A dab of anhydrous lanolin in each threaded insert should prevent electrolysis between the stainless steel and brass.  The base and backing plate are bedded with Dolfinite.  I was prepared to enlarge the through-deck holes in the event of slight misalignment, but it turned out to be unnecessary.  The rated thrust of the push rod is 275 lbs, so the stanchion must be quite strong, able to resist these substantial lateral stresses.  It looks and feels to me strong enough, but the proof is in the use.


Location of the stanchion on the port quarterdeck, near the stern deck cleat, the combing, and not so far from the auxiliary anchor, places it in an already crowded area of deck real estate.  On a boat as small as Ripple, it is another thing to trip over, but the starboard quarterdeck remains relatively open.  Of course, it is important that it not interfere with aft mooring lines and the mainsheet while underway.  I think it will be fine.

The hardest part of the installation was drilling holes in a perfectly good deck and tiller (for the tiller pin).  The first-time-perfect-alignment made me feel better about it.  Its all wood, right?  Everything can be fixed.

I'll sew a cover for the tiller pilot unit to keep rain and sun at bay (field reports highlight the importance of this additional kit).  The completed setup:








Comments

  1. dbostromNovember 19, 2014 at 11:25 AM

    That's a beautifully executed project; an aesthetic addition rather than a wart.

    Autopilot means you can actually obtain useful fixes by hand bearings and do other such things while working alone or when the crew workload is high. This particular kind of complexity offers you ability to work around other kinds of failures. A perfectly sound compromise.

    ReplyDelete
  2. John MillerNovember 24, 2014 at 9:55 AM

    I love my Ray Marine Tiller Pilot! You will wonder how you ever managed without it! I Single-hand a LOT, and I agree...much safer to have one. you won't regret it! I loved the Base... almost a sculpture! well done!

    ReplyDelete

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