• Design and Equipment Selection Considerations
• Installation
• Follow-up 2006

Among the very few negatives of the 424 hull is its refusal to behave itself in close quarter maneuvering under power.  A look at the underbody is all that’s needed to understand why the boat tracks so well at sea, but maneuvers sluggishly under power in close quarters.  The smallish rudder is hung behind a large skeg; the propeller is located relatively far forward, approximately under the bridge deck; and the prop shaft is angled downward so that the prop wash mainly passes under the rudder, minimizing prop torque but also virtually eliminating the rudder “kick” that many boats can generate with a quick burst of engine power against a hard-over rudder.  When boat speed is low, the high freeboard forward and the cutaway forefoot make the bow react to currents and wind far more than to the frantic efforts of the helmsman.

After thirteen years of docking trauma, and following consultation with other owners who have installed bow thrusters (Many thanks to Don Barber of Thisisit and Bill Dwyer of Overdraft), I decided to treat Meridian to a mechanical crewman up forward. David Kimmel of Harmony and I decided to do the project on both our boats at the same time to gain whatever quantity discounts might be available, and to help each other with the parts of the project that were to be owner-accomplished.  Planning and shopping, including a trip to the Fort Lauderdale Boat Show, culminated in a decision to go with a Vetus Model 5512 electric thruster with a nominal 6” diameter tunnel.  

Design and Equipment Selection Considerations

Selection of the Vetus Model 5512 was driven by three factors:

1. The size of the tunnel (6-inch diameter) allowed the unit to fit in the narrow space aft of the forward water tank.  Harmony has aluminum tanks, and had a 12 ½” space there.  Meridian has fiberglass tanks and only 10 ½” of room.  Selection of a larger unit would have required that some of the cabinetry in the vee-berth area be dismantled to accommodate the installation of the tunnel tube, adding to the cost and complexity of the project.
2. The shape of the hull in that area meant that the 30-inch long (standard) tunnel would get the job done, albeit just barely.  A longer tunnel would not only have added significant cost to the project, but would have compromised the thruster’s performance owing to tunnel drag.
3. The Vetus units are less expensive than their competition, but offer comparable construction and design features.  The model 5512 costs about $1,000 less than the next larger Vetus unit.  We could find no competitive unit that would fit as well into the fore-and-aft space available.

Power supply options were (1) operate the unit from the existing batteries aft and run heavy cables to the thruster, and (2) provide a separate battery for the thruster and install a charging arrangement to keep it topped off.  We decided to go the latter route owing to the size, weight, and expense of no. 4/0 gauge cables and the difficulty of routing them through the boat.  Our design for the electrical system, diagrammed on the attached page, was derived from the recommendations of the Yandina Company (http://www.yandina.com/), and we bought our battery combiners and circuit protection from them.  Cabling and connectors came from Northern Arizona Wind and Sun (http://www.windsun.com/).  I installed a group 27 “dual purpose marine battery” from Sam’s Club; David went with a size 31 AGM battery to match the rest of his batteries as to charging characteristics.  Both of us secured the batteries in home-built steel brackets attached to the bulkhead aft of the water tank.

We decided to control the thrusters with foot switches mounted in the floor of the cockpit.  Vetus sells hand switch controls and joysticks, but we adapted their windlass control switches to the new task, requiring that we make a minor modification to the control wiring harness.  We reasoned that (1) the helmsman already had enough work for his hands in dealing with the steering wheel, shifter and throttle; and (2) that installation of a conveniently located hand switch or joystick would be a hassle on both our boats.  The picture shows the floor of the cockpit aft of the steering pedestal.  The switches are shown with their protective covers closed.

Installation

David arranged with John Orm of Pelican Marine in Tarpon Springs, Florida to do the fiberglass work; we had already decided to do the rest of the project ourselves.  John obtained the thrusters and tunnels, fuse blocks, fuses, and switches directly from Vetus, and David and I accumulated the remainder of the materials from the other sources noted above.  We did the electrical installations in advance, to minimize the expense of our time out of the water.

Harmony was hauled on a Tuesday, and went back into the water the following Friday after John had completed his work and repainted her bottom.  Twenty minutes after Harmony was launched, Meridian went into the haulout slip.  She was launched the following Tuesday afternoon.

         

The photos show the installation in progress on Meridian.  John cut the holes in the hull using an electric reciprocating saw, and then fitted, marked, and cut the tunnel tube.   He then cut away the gelcoat and several layers of laminate from an area around the hole on each side using a laminate plane, and prepared the inside the hull in the attachment area with a small electric grinder.  After fitting and installing the power head of the thruster to the tunnel on the workbench in his shop (a departure from Vetus’ instructions but a major time saver), he returned the tunnel to the hull, carefully aligned the centerlines, and then “glued” it into place using polyester putty.  Once the putty had set, immobilizing the tunnel, John applied several layers of new fiberglass laminate to the inside of the hull.  After the resin “kicked”, he returned to the outside of the boat and laminated, faired, smoothed, and painted the outside.  Because of the extremely close clearances on the inside of the boat, John was able to apply laminate only to the top two thirds of the circumference of the tube.  He added the required strength in the exterior laminations by grinding away most of the thickness in the bottom of the tunnel tube and building up the laminate from there.  The result maintains the tunnel’s inside diameter while still providing adequate laminate thickness for strength.   After coating the new laminate, the bare tube, and the wetted parts of the thruster with three coats of epoxy barrier, the bottom paint was applied, completing the installation.

 

The interior part of the installation was completed by painting the inside of the compartment, including the new tube and fiberglass bonding, fitting the drive motor and battery bracket, and hooking up the wiring.  We tested the operation of the unit and then prepared Meridian to be launched.  John gave the tunnel a final check while we were afloat but still in the slings.  

When we got home we gave the new equipment its first real operational test, and we were very pleased.  We can turn Meridian 180 degrees in her own length using engine reverse and thruster, then forward and thruster.  There’s no more anxiety about picking up the bow line on the first pass.  If it’s missed, we just move the bow toward it a bit, enabling another try.  Subsequent practice has confirmed the dramatic improvement in control, and it certainly seems that we will make a lot of use of this new labor (and anxiety) saving device.

Costs were $1,485 for the thruster unit, tunnel, battery, bracket, and electrical cables and equipment, and $631 for installation materials and labor, for a total of $2,116.  The costs of hauling, launching, and bottom paint are not included; Meridian was due for bottom paint anyway.

Diagrams of the electrical installation and the homebuilt battery bracket are on the following pages.

If other owners have questions about the details of this project, I’d be glad to discuss it with them.  My email address is Lee Thurner.

 

Follow up in July, 2006

Pat Noordsij: Now that it has been 4 yrs, are you still happy with the Vetus 5512?

David Kimmel: Every time I leave or enter the slip it puts a smile on my face....
It would have been nice to have gotten a larger unit. However it would have
requried a much larger amount of cash and redoing the V-berth. In this case
it just used a small space that I never used that much to begin with and the
cash outlay was a great ROI.

There are times when the wind and the current over power the thuster because
of its smaller size. I am not even sure if the bigger units would be that
much help in these case due to our windage.. These are the time we just have
to go back to our boat handling skills..

There is nothing like being dead tired and easly backing into or pulling
into a difficult berth with no worries. Oh and I love being in a slip that
is way too big and use the bowthruster to bring the bow to port or starb. to
set the lines... Way easier ...

The best part is it has worked flawlessly for the past 4 years....

So yep still happy. Just wished I had done it sooner!!

David