First, we tested our new steering design in New Zealand waters. Then we “enjoyed” some rigorous shakedown across the Tasman Sea, and from Australia to Japan via Indonesia and Palau. We are now ready to declare our Buffalo’s steering issues fully resolved, with harmonious and alarm-free relations between steering and autopilot! Here, we summarize the issues and solutions.
Our normal steering control is via a Simrad AP70 autopilot, and an Accusteer HPU100 constant run hydraulic pump driving LeComble and Schmitt VHM 60 DT C300 APD rams which turn our big rudders. We have two identical main pumps, intended for redundancy, but also offering the ability to engage the second one with a push of a helm button as a “dock pump” or “boost pump” for close quarters maneuvering, or especially challenging sea states, when quicker rudder response is desirable.
If power to the steering pumps and hydraulics are intact, but we have a failure involving the (pair of redundant) AP70 computers, we have a back-up Simrad S35 on the helm, which engages with the push of a button and uses a third Accusteer HPU100 constant run hydraulic pump. This will bypass the autopilot computers.
If we have complete loss of power to autopilot computers and/or steering pumps, but intact hydraulics, we have a manual helm pump which we can enable by turning some valves in the lazarette. This allows us to steer using a steering wheel mounted on the aft deck right next to the entry door.
Finally, if we need to bypass everything, we have emergency tillers with blocks and tackle in the lazarette which can take direct control of the rudders.
We had frequent failures during initial trials and shakedown cruises in New Zealand, either with deliberate high speeds and hard acceleration while cranking the rudders hard over, or more rarely during fairly commonly encountered conditions underway such as 1.5 to 2-meter quartering seas. The autopilot would alarm with “loss of rudder control,” we’d lose steering control and have to push a few buttons to get it back.
After quite a bit of experimentation with both autopilot and pump settings to no avail, including adding a relay to the pumps to allow them to function more efficiently, focus turned to the steering cylinders. (There was almost no suspicion that our pumps themselves were inadequate.)
As an aside, speaking of experimentation with settings… Those of you who have followed Steve Dashew’s blog over time will know what an avid collector and analyzer of data he is. During our shakedown time in New Zealand, Stan had numerous phone conversations with him while we were underway. One moment I recall: “Now, Stan, let’s turn the stabilizers off, and let the boat wallow around. No… more. More. You should be hearing a lot of noise from inside your galley lockers.” That was far from my worst day aboard, but not my best either! We, for our part, were no doubt his worst students. Horribly non-compliant and rarely able to provide the numbers he needed. I can only tip my hat to him in acknowledgment of his perseverance. He has stuck with us to help us tweak our systems and solve our issues despite our bratty behavior.
Circa replaced the VHM 60 DT C300 APD rams with the next larger size (VHM 63 DT C345 APD.) We saw substantial improvement in performance… but unfortunately still experienced failures under certain conditions.
Circa then engaged the services of LOMOcean Design as consultants to run numerous computer simulations testing slightly different rudder configurations. They concluded that just adding 85mm to the leading edge of our rudders, shaving off around that much from the trailing edge, and adding a bit of taper at the top would significantly reduce the force required on the cylinder actuating the tiller, even at large rudder angles. While this sounds simple when I summarize it this way, the process was long and painstaking. We were impatient and oh-so-ready to take off for distant shores, but of course determined that we have reliable steering control and redundancy when we did so. In any event, we learned more than we ever wanted to know about hydrodynamic stall.
Here are our rudders as Circa was in the process of modifying them:
And, presto! Issue resolved, and we are happy cruisers.
Next up: our sojourn in gorgeous Raja Ampat, Indonesia, with pics above and below the surface.