Design Safety For Your Explorer Yacht

Updated: Sep 6

I’m writing this as much to clarify personal thoughts as to verbalize a decision process.  Having a good idea is an easy initial step; a vague idea of how to progress is the fun part; a detailed, considered plan to completion is a bit of a grind.  What happens is all those “can do later” decisions come back to say hello, Hi! I’m HERE!  Explorer Yachts, by their nature, should go to very out-of-the-way places if used for their intended purpose.  In such areas, help is minimal, and that entails consideration of what happens when things break.  And they do.

A pragmatic approach

Redundancy or Critical Failure Analysis is a whole science in itself.  I guess the pinnacle would be space, nuclear, aircraft, probably in that order if considered in terms of cost per incident prevented.  We don’t have such luxury, and we have a deadline.  Given that we still have to make those decisions and are budget-constrained, we have taken a more pragmatic approach.

Firstly we will follow Commercial practices and, where feasible, purchase commercial-grade equipment.   Examples of that would be John Deere M1  (continuous running) rated engines, Wills Ridley (fishing boat) steering gear.  We will fit Time Zero Navigation software implemented through marinized touch screen MFD displays. Each capable of displaying all processes and powered independently, giving triple redundancy excluding a duplicate system on the flybridge.  They are all hardened against EMC and isolated against flashover from lightning strikes.   Some pumps, for example, Fuel Transfer, are duplicated in parallel, and each capable of drawing from all bunker tanks, discharging to either day tank.  Engine supply pumps are not in parallel as we have two engines and carry a spare pump, so there is no need.  The steering has three control stations plus a local directly wired manual override and pumps that will run series or parallel. We can hydraulically lock either rudder in the event of damage.

Construction code

We have followed the Commercial Code in the vessel construction. Using it as a minimum specification where strength is concerned.  We have a very stable design that’s weight tolerant. Like Dashew and FPB or Arksen, we have increased scantling sections in the way of the forepeak, underfoot, skegs … to two or sometimes three times Code and the remainder hull to a lesser extent.  Aluminum construction helps here as the weight penalty is less than the strength gain with increasing thickness.  Rudder stocks are another example where they are effectively double the required diameter according to the LRS or DNV Codes.

Twin engines draw fuel from independent day tanks. Independent sea suctions are installed with backflush on the run or cleaned at sea, and we have a crossover valve if one blocks irretrievably. Diesel heater can also be fed from either day tank, as can the fuel polishing system.  Bunkering protocol is such that fuel is processed and assured viable before co-mingling (if at all).

Single Points of Failure

We then started looking at the less obvious.  Those single point of failure that become the $10 component that wrecks a plan.  The high-voltage DC cabling design has been replaced with a robust DC Bus Bar, which we can tap.  Duplicate three phase, 230VAC power inverters provide 100% redundancy or run parallel at a lower stress level.  We did not replicate the shore power isolation transformer as we felt our internal generation capacity was a sufficient safeguard. We split the battery bank to defend against a DC short.  The knock-on will be reducing the maximum discharge rates creating some headaches elsewhere, but we felt it essential to develop a more robust solution.  We upgraded Telemetry from NMEA 2000 to a redundant Ethernet backbone. This resulted in a significant increase in bandwidth on the display update for Radar and Plotting. We still retain NMEA 2000 were convenient but on spur lines only.

Third Party Review

Lastly, and this was another Blog subject, we specified a third-party certification and ongoing inspection regime.  In our case, it’s UK Marine Coast Guard Agency Category 0 (unrestricted) Classification.  Like Caesar’s wife, she does not need to do good; she needs to be seen to do good.

Is all this overkill?  Well, yes is the answer. The counter is that our family will be on board; we should explore whatever reduces risks upfront.  There is, though, a law of diminishing returns where safety is concerned. At some point, enough is enough, and as I say to my children, most adventures are not so much fun when you have them.  But in hindsight, “boy, what a life we had.” 

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