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Tuesday, January 31, 2017

STABILISERS PART 1

Envoy is in Lefkas Marina for the northern hemisphere winter and we are home for the New Zealand summer returning to Lefkas during April.

This posting is based around an article I've written for Pacific MotorBoat magazine.

In pre-Envoy days boating around Auckland's Hauraki Gulf we owned several planing boats culminating in a 40 ft Oliver Royale GRP planing boat with twin Yanmar diesel shaft drives. We never then considered rolling to be an issue, however we realised very soon after buying our Nordhavn 46, Envoy, that full-displacement hulls are another matter, definitely requiring stabilisation to provide acceptable levels of comfort and safety when cruising moderate distances in beam seas higher than about one metre. I'm sure there are reasons for this that a boat designer could properly articulate. As much as I know is that in slight to moderate seas the flatter hull sections of a planing boat resist rolling to a greater extent than the rounded sections of a displacement boat. Also I have found that a fast boat on the plane seems to sit quite comfortably on beam waves without too much roll. On the negative side I understand that planing boats can roll dangerously in heavy beam seas and are more prone to capsize than ballasted displacement hulls like the Nordhavn. Additionally planing hulls pound when their flat sections hit waves, whereas the rounded sections of displacement hulls rise and fall more gracefully with greatly reduced noise and violent motion.

In our experience a planning boat like our previous 40 ft Oliver Royale doesn't roll under way to the extent that a displacement hull does

What follows isn't a technical treatise but comments based on cruising thousands of miles using Envoy's three stabilisation systems.

Stabilisers have been used for many years aboard commercial vessels but aboard pleasure craft only for about the last 40 years, considerably reducing rolling motion in beam seas, but with minimal effect on pitching caused by seas on the bow or stern.
Now some reader is bound to think “buy a catamaran and you won't have a problem” and I'd be the first to agree you've got a lesser problem, but we've met many folks who complain about their cat's motion both under way and at rest. Of course this is either better or worse depending on their design, as with monohulls.

Envoy at anchor with starboard stabiliser pole deployed with flopper-stopper to reduce roll from slight swell. The port pole can be seen in the vertical position

A web search shows many variations of stabilisers, but the mainstream systems fall into three basic types; passive, active and rotary.
We have no experience with rotary stabilisers, which are a more recent development utilising a flywheel contained in a vacuum chamber to provide a gyro effect, but they're reportedly highly effective in roll reduction both under way and at anchor with the advantages of having no protruding parts to cause speed-reducing drag or become fouled. They are able to be retrofitted either amidships or offset to one side, but have a significant investment cost. Presumably, if used for long periods such as overnight at anchor a generator would be needed to provide sufficient power – something we would not want to do.
Envoy has both passive and active stabilisers providing effective stabilisation under way and at anchor.

Envoy with both poles deployed with flopper stoppers to reduce roll at an exposed anchorage with ferry wakes



Next posting will discuss passive stabilisers in detail.




Sunday, January 08, 2017

ATHENS

Happy New Year to our readers from around the world.
Envoy is in Lefkas Marina for the northern hemisphere winter and we are home enjoying the New Zealand summer.

Back to early November and after a very scenic five hour bus trip from Lefkas we stop over one night in Athens on our way home. There are so many ancient ruins in Greece that we see many along the way that aren't even signposted. This is real treat for us coming from NZ where there are hardly any structures over 150 years old.

Our hotel is in the downtown Plaka district close to the Acropolis and next morning we go for a walk in a huge wooded park next to parliament. Historically this park was the gardens of the royal family and parliament was their palace.

On the way back to the hotel we encounter a large and very peaceful demonstration of several thousand older folks carrying placards protesting the pension cuts that have been part of Greece's austerity measures. One retired man tells us his pension was formerly 2,300 Euros (about NZ$3,540) per month and has been progressively cut to 1,200 Euros (about NZ$1,850). Although the cut is obviously huge we cannot help feeling that the pensions were too high in the first place.

A cab driver later tells us that employment is very high at about 37 per cent. Greece's family culture is very strong however and most family groups own their own home, resulting in adult offspring often leaving apartments they can no longer afford and living with their parents. He explained there is little government support available for unemployed people but family and friends assist.

Importantly for the cruising community the worsened socio-economic situation hasn't increased crime and Greece remains an extremely safe country, our driver advising that a lone female can safely walk anywhere any time (which is certainly not the case in many parts home in New Zealand).

The same driver stops at a scenic lookout half way up the steepest of the seven hills of Athens for a spectacular view of the city, the Acropolis and the ocean. Athens is a large city of nearly 4m people with few high rise buildings as since the mid 70s new buildings aren't allowed to block views of the Parthenon on the towering Acropolis.

We now plan to continue Blog postings relating to Envoy and cruising in general until we return to Greece in April. Next posting will discuss stabilisation.


Monday, January 02, 2017

FINAL DAYS IN GREECE FOR 2016

Envoy is in Lefkas Marina for the northern hemisphere winter while we're home in New Zealand enjoying summer.

Back to late October and it's always much more fun getting any boat ready to cruise for the summer than to store for the winter, but we get stuck into Envoy's winter storage process. We have this well documented and it's simply a case of spending a few days doing all the jobs and ticking them off.

On the way back to Lefkas we spotted a Diesel Duck trawler. These are a rugged no-nonsense go anywhere passagemaker that we've often admired.

Diesel Duck

At this time of the year there are frequent squally fronts passing over like the one depicted below that chased Envoy down the coast.

Squally front

Envoy in Lefkas marina with winter cover fitted


After a couple of days a cat befriends us and becomes a regular visitor, boarding Envoy in the mornings for a feed. We're very happy to see plenty of cats around any marina as it keeps the rodent population down.


TECHNICAL
Our end of season jobs include running the generator, wing engine and all sea water pumps for about 15 minutes with a mixture of fresh water and Saltoff, then introducing glycol to replace the water in order to reduce corrosion during the period of non-use. This is time consuming as we need to remove the top from each equipment item's water strainer and feed it using a fresh water hose.
We fit Envoy's storage cover, now nine years old, which has been reconditioned during the summer with patches sewn over areas of thinning fabric, plus new velcro and zips. It goes on easily and will keep Envoy dry and clean during winter.

Apart from other routine season-end procedures we:
-Get a RHIB specialist, Nikos, to visit and replace two air valves on our large Nautica RHIB. A special tool and some practice is needed to do this. These valves have been marginal for a while and Nikos says they were close to failure.
Nikos also takes away our smaller Valiant RHIB and during the winter will repair a pontoon's slow air leak and a transom sea water leak.
-Sailand's Velisaris visits to review several jobs to be done during winter.
The dual trumpet air horn has failed due to water ingress and needs repair or replacement.
One of two domestic fresh water supply filters has a leaking filter housing which needs replacement. Our “Water Fixer” U/V water purifying lamp needs a check to see if it's working.
Our Lugger's alternator and Maxwell windlass electric motor need removal and checking.
Our main Raritan Atlantes head needs investigation to determine why it won't discharge through its seacock, but only via the holding tank, which has a different outlet overboard.

-Sailand will also do several other jobs for us during winter:
Our stabiliser paravanes or “birds” as we call them (the metal plates that go under water) need maintenance as the galvanising is starting to corrode. Sailand advise the quality of galvanising in Greece is not good so recommend an epoxy primer and top coat instead which will enable easier future maintenance.
Two Plexiglas deck hatches in the guest cabin need re-sealing into their frames.
Our Lugger main engine, Yanmar wing engine and Northern Lights generator will have all cooling hoses checked and replaced where necessary, coolant drained and replaced, air filters cleaned and a complete visual check.
The generator will also have its mountings checked, fresh water circulating pump checked and sea water pump serviced.
The Yanmar will also have its sea water pump checked and impeller replaced.
Before we return to Lefkas Sailand will lift Envoy from the water to prepare the hull for anti-fouling, clean and check the running gear and remove and clean the keel cooler.

With all complete it's goodbye Envoy until we return in April … but the Blog continues.