M/V Elwha (Mount Baker in the background)
[“M/V” stands for motor vessel, by the way, and is commonly used with commercial vessel names.]
I bet some of you folks don’t know that ferry boats do not all have the same sorts of propeller configurations under their hulls. I bet some of you folks don’t really care about that … as long as the ferry gets you where you want to go, then you’re good with that.
But for those of you who do care or might be interested, here’s a little bit of information about the two types of ferry boat propeller configurations used here in the State of Washington on our very numerous double-ended ferry boats.
First off, below is a photo of a wooden model of a ferry here on Puget Sound. You’ll see right off that the two ends are identical … each end has a large steering rudder, a propeller, and a shaft that turns the propeller. The hull of the boat is shaped the same at each end as well. And there is an engine at each end of the boat inside the hull that turns the shaft and propeller. Both engines and rudders, at both ends of the boat, can be controlled from either bridge or steering station at either end of the boat. The Captain has full control of both ends of the boat whether she/he is at one end or the other.
With very few exceptions, on all ferry runs in Puget Sound, ferry boats do not turn around … they simply go back and forth between two ferry docks. The Captain and bridge crew walk to the other end of the boat when it’s time to leave the dock to go back across the water to the other ferry dock. The two ends of the boat are not called “bow” and “stern”; they are called “No. 1 End” and “No. 2 End”.
So that seems pretty simple, yes? But, what happens to the engine and the propeller at the “forward” end of the boat each time the boat reverses direction?
For instance, say we are leaving Shaw Island on the left and going to Orcas Island on the right (real islands here by the way). Obviously, the propeller at the “stern” of the boat will be turning at speed and pushing the boat along, but what is the propeller at the “front” of the boat doing? Is it stationery and not turning, but then it would create resistance and drag and so would it slow the boat down? Is it turning in reverse and so helping “pull” the boat along? Does it fold up into the hull? What?
A few years ago, those questions popped up among some friends of mine. None of us knew the answers. So I wrote to the Washington State Department of Transportation thinking I might not get any answer at all, but I got excellent answers from excellent people. Here’s how that communication transpired:
How Double-ended Ferries Work:
March 19, 2010 From: Ann Hay, PNW Fleet Commodore, Classic Yacht Association.
To: Washington State Department of Transportation (WSDOT), Washington State Ferries.
Hello, a number of us have been wondering what happens on a double-ended WSDOT ferry (some wood hull ferries in service since 1953) with the props on the forward end of the ferry. Are they held in place and don’t turn? Are they used to “pull” the boat and thereby enhance the effort of the props on the other end? Do they “feather”? Etc. Thanks much!
March 23, 2010 From: Captain George A. Capacci, Washington State Ferries
To: Linda LaCombe, Washington State Ferries staff
Not a simple answer to an apparently simple question. Let me put something together. George
April 5, 2010 From: Linda LaCombe
To: Ann Hay
Ann .. Our Regional Port Captain put this explanation together for you and included a couple photos – I think it does a great job of explaining the process! I think it is fine to use both the photographs and Captain Capacci’s name in your newsletter. Feel free to share my contact information if people have questions about WSF. Thanks for your patience.
Linda LaCombe, Customer Service and Information Manager
Washington State Ferries, 206-515-3635
From Captain George A. Capacci
All current Washington State Ferries are double ended vessels meaning there is a single propeller at either end. The condition of the “forward” propeller during transit depends on the specific propulsion plant and the type of propeller on the class of vessel.
WSF propellers come in two configurations – Fixed Pitch Propellers (FPP) or Controllable Pitch Propellers (CPP).
FPP – Jumbo Mark II, Jumbo, Super, and Evergreen State class ferries with Fixed Pitch Propellers operate in the transit mode with the forward propeller turning in the direction of the water flow to minimize resistance to the vessel’s progress. The propulsion plant (AC/AC, AC/DC or DC/DC) applies power via electric drive motors to both propellers with roughly a 90%/10% ratio meaning 90% of the propulsive power goes to the stern or pushing propeller. Roughly 10% of the propulsive power is applied to the forward propeller so the forward propeller is “pulling” very slightly, but essentially the forward propeller is not resisting the progress of the vessel by turning with the water flow.
M/V Spokane with FPP configuration with 13-foot diameter propeller. [Ann’s note: The “forward” propeller turns slowly, in order to slightly pull the vessel, or at least not to impede the vessel’s movement.]
CPP – Rhododendron and Issaquah class ferries with Controllable Pitch Propellers operate in the transit mode with the forward propeller shaft locked and the blades of the propeller “feathered” or turned to be parallel to the flow of water to minimize resistance to the progress of the vessel. The propulsion plant is geared reduction drive directly off the diesel engines. During maneuvering, both shafts turn at a constant speed and the CPP are adjusted to apply the propulsive power the Master seeks to direct the motion of the vessel.
M/V Chelan with CPP configuration with 11-foot 6-inch diameter propeller. [Ann’s note: Each separate fin/blade on the “forward” propeller is rotated so that it’s in line with the direction of the boat’s movement. When the ferry arrives at its destination, those blades are then rotated back into position so that they can provide propulsion when the ferry goes back in the opposite direction.]
I’ve attached pictures of an FPP (Spokane) and a CPP (Chelan) to point out the differences.
Hope that helps.
George
Capt George A. Capacci
North Region Port Captain
Washington State Ferries
M/V Spokane (FPP propeller configuration)
M/V Kitsap (CPP configuration the same as the M/V Chelan)
For more detailed information, check out https://www.ebdg.com/wp-ebdg-content/uploads/2016/07/JWW-50-Years-of-Double-Ended-Ferry-Design-Web.pdf. At the end of that PDF article, you can read about the author. John is a friend of mine and is one smart cookie!
More info about the Washington State ferry system is HERE. It’s the largest ferry system in the USA.
Two friends of mine are employed on board ferries. It’s an excellent system of transportation that’s so common here we sometimes take it for granted, but also a system we couldn’t easily live without since many destinations are large, populated islands with no vehicle access except these ferries.
Even we who are Washington State residents pay to use the ferries, but it’s sure worth it … especially on a beautiful summer day. Hop on the ferry with your car or just walk on board and enjoy a relaxing cruise through the islands.
Anderson Island started with a 6 car ferry, then a 9 car ferry and now has a 52 car ferry. I can’t tell you how many ferrys I have missed. On holidays, when ferry traffic was booming, especially on the 9 car ferry, everyone wanting to leave the island would get in line hours before and have tailgate picnics, play cards and generally horse around to pass the time.
Ah yes, I remember your folks had a place on Anderson [Marif and I are old friends]. Back in 2014, along with other friends of mine, I anchored my boat in Oro Bay at Anderson Island for a few days and cruised past the now relatively “large” ferry dock on Anderson Island (you readers can see today’s ferry dock at http://www.mvpiedpiper.com/2014augustsouthsound.html). That’s the downside of island living, isn’t it, with the ferry as the only way on/off the island. But I guess the upside is you meet your neighbors, as long as it isn’t raining cats and dogs. 🙂 Hmmm, ok, that got me to thinking … now I have to research possible camping places on Anderson and other small islands. Thanks Marif! 🙂
Oro Bay used to have a ramshackle, falling down, every other board missing bait dock and a “store”. The store was filthy and both the store and the bait dock were run by a couple of old guys who didn’t believe in bathing-ever. My mother bought a chocolate bar there once and declined to share it. Imagine the hysterical laughter (on our part) when she unwrapped the last part and discovered worms. We laughed; she was just in hysterics.
Oh my word! Your poor mother!
But, hey, worms are bait, right? This was evidently a handy one-stop food and bait store. 🙂 ok, sorry.
WOW, so informative. I have never wondered about this, but I wonder why I didn’t wonder about this? Who would’ve guess that this was SO interesting??? Thank you for getting this information, and the photos add so much! I will use it to impress guests that we occasionly have on BACCHUS. They will think I am so smart, but the credit will go to you. In fact, I will give you credit whenever I tell someone this information. Thank you!
Isn’t it fun to wonder and learn? I’m humbled that you would give me credit … all I did was admit I don’t know c**p, er I mean I don’t know some things, and then I asked. No one was born knowing anything, after all. Let’s just keep sharing information about interesting things. Thanks Bob.
I’ve been on a few ferries. The ones that are probably most like these, never turning around, were in Florida, traveling across bays. I never thought about there maybe being two propellers….or what those propellers were doing. But it makes sense. Thanks for the informative post!
You are welcome! So much we take for granted, eh? Like how a ferry boat works. I know I sure take lots of stuff for granted. Much of that is by necessity … how much information can one brain hold after all? Even really big brains like ours. 🙂
Excellent presentation, Ann. I especially appreciated your inclusion of the link to John Wodehouse’s paper. Very informative, and I could understand almost all of it!
And I can personally attest to his assertion that “all vessels gain weight over a lifetime.” Drat!
LOL! Had to laugh out loud at your comment about vessel weight gain, Jan. 🙂 I suspect John meant that boats would gain weight over time from added systems, more electrical and navigation equipment, more layers of paint, more safety devices and equipment, etc. But I wonder about the idea of simple aging and the weight gain that many of us humans experience. The ferry boats’ engines lose power, their lights dim, their navigational systems may go on the fritz … sounds just like us, doesn’t it!