This week Team Möbius made great progress on both on the bottom and the top of the hull of the hull. On the bottom Sezgin and Mehmet continued in what must seem to them as the unending miles of welding since all the hull plates have been tacked in place. Joining them on the floor Enver and Umit were busy completing the fin shaped skeg which houses and supports the propeller shaft. Meanwhile up on top Uğur and Enver were busy setting the first frames that make up the superstructure for the above deck Pilot House which wraps around our primary and largest of the three interior living spaces, the area we refer to as the SuperSalon.
This superstructure creates an eXtremely strong monocoque like cage that provides the framing for the 360 degrees of glass windows which wrap around the entire SuperSalon and the roof creates the floor for the SkyBridge above. The SuperSalon contains our Galley, Dining table and Lounge areas as well as the main Helm Station at the front and the stairs leading down to our Master Cabin forward and Christine’s Office/Guest Cabin aft. But enough already Wayne! Let’s get on with the pictures and video.
This foil shaped fin on the bottom aft end of the hull is what is called a Skeg and it helps a bit with keeping the boat tracking straight much like the fin on a surfboard but its primary roles are to protect and support the propeller shaft where it exits the boat and enters the water and to provide protection to the propeller and rudder aft from any debris that we might run over.
Seasoned sailors know from first hand experience that it is not IF you are going to run aground but when. The 50mm / 2” thick “shoe” you see in these two photos will be welded onto the bottom of the Skeg and add even more strength to the massively over engineered Skeg.
The bottom of the Skeg is also the lowest point of the boat so this is where the boat would first contact the bottom and we have built it to be eXtremely strong to be like the old Timex watch jingle “It can take a licking and keep on ticking”.
The center of the skeg is a continuation of the 25mm/1” thick keel bar that runs down the center of the entire length of the hull and the temporary support webs you’ve seen in previous posts have now been cut away so that the 15mm thick aluminium tube you see here can be slid in place.
Looking aft you can see how this aluminium tube has been pressed through the thick support webs and tacked in place.
Once the hull is all finished and we are fitting the engine and CPP propeller system, the CPP prop shaft log which is another tube containing the prop shaft, bearings and seals will slide inside this tube with about 12mm / 1/2” of clearance between the two tubes. Once the engine, CPP gear box and prop shaft have all been perfectly aligned the space between the two tubes will be pumped full of special “ChockFast” epoxy and form an eXtremely robust and well aligned propulsion system.
We call Sezgin away from welding the hull plates to lay down these beautiful welds to complete the prop tube installation and get ready to fit the thick plates that will form the slick foil shape of the Skeg.
Climbing up onto the aft deck to get this shot looking down into the Engine Room clearly shows a sectional view of the carefully chosen foil shape of the slippery skeg (under the yellow chain hoist).
The two 25mm thick beds for the engine and CPP mounts are running horizontally on either side of the Skeg and if you look closely (click to enlarge) you can see the end of the prop tube where it enters the Engine Room on the left.
While I’m up here, this shot looking a bit further aft into the Workshop area behind the Engine Room shows the arc of the prop tunnel from the inside.
Further forward Sezgin our Master Welder continues his non stop welding of the 15mm/ 5/8” thick hull plates.
Mehmet works both before and after Sezgin to initially prep all the areas to be welded by grinding them clean and well recessed and then follows up by cleaning the thick final welds which Sezgin has laid down. They are certainly getting a workout now that much of their work has to be done overhead but they are always smiling and enjoy seeing all their great progress.
This shot looking towards the bow shows most of the different phases of the welding. The dark rows extending forward on either side of the center keel bar are the temporary bridges tacked across the seam where the two hull plates meet to keep them perfectly aligned during welding with that ceramic backing taped in place as you’ve seen in previous posts. Coming aft of Sezgin’s left shoulder is the finished beads of welding he has laid down where the hull plate attaches to the keel bar
Back at the stern there is new action as Uğur passes some of the previously welded assemblies up to Enver on the Swim Platform. Wonder what they could be for?
Ahh yes, the truly super structure that wraps around the SuperSalon. First they carefully align the vertical I beams with the stub ends of the hull frames that were welded in as part of the first phase of building the hull when it was upside down. You can see two of these stub ends behind Ugur’s back to the left side here.
A (blue) digital readout level is used to get the angle just right as they tack each part in place.
Once the vertical I beams are all tacked in place the upper component of each frame is set in place using the CNC scribed lines to align them just right.
The frame in the foreground is the aft end of the SuperSalon with the WT door to the steps leading inside with the Galley on the Starboard/Right side.
Moving up to the foredeck looking aft through the SuperSalon, Uğur is prepping the long plates that will form the underside of the roof overhang of the SuperSalon and getting ready to tack the front window mullion posts in place.
The four vertical posts up on top of the frames are the beginnings of the framing for the coaming that runs around the SkyBridge atop the SuperSalon.
Doesn’t take him long to get the latest pieces of this giant jig saw puzzle tacked in place and the final shape of Möbius continues to emerge.
You can see how all the windows are negatively raked, bottom in further than the top which is a feature we picked up from all the Pilot Boats we visited and pretty much eliminates reflections on the inside and reduces the rain drops on the outside.
Hopping down into the SuperSalon I can now check out this view from the inside.
Can you imagine what this will look like when we are in some lovely little anchorage with nothing but tropical turquoise seas and beaches outside all these windows! We sure can!!!!
While I’m up on deck thought I would show you the progress up on the bow. The “side slinger” anchor roller assembly on the left, Samson post in the center and the big nose cone at the front.
Sezgin has finished welding up the inside area round the snubber nose cone. All the welds exposed above the waterline will eventually be carefully ground flush and smooth to create a uniform and smooth surface.
And just before we go, a few photos to give you a quick update on the equally great progress being made a few blocks away here in the Antalya Free Zone with the building of the new Naval Yachts shipyard.
The ubiquitous crane trucks are being kept busy as the framing for the shipyard building goes up.
And concrete trucks and pumpers continue to arrive with the first of the slab floors going in place here. If this progress continues the hope is to move into the new facilities next month!
As always we’ll finish up with your reward for getting all the way through yet another of Wayne’s posts with a quick time lapse video summary of this week’s progress.
Thanks for joining us and be encouraged to add your questions and comments in the “Join the Discussion” box below.
A lot of hard work!!
Quite right Elton and we could not be more delighted with the cadre of people that Naval Yachts have put together and that we can be such an integral part of this team. I often characterise Project Goldilocks and mv Möbius as “a collaborative work of art and engineering” and could not be more delighted with the way that is personified by Team Möbius. Look forward to having you aboard to see it all for yourself some day soon.
She is taking shape my friend. I love watching your posts. 🙂 Cheers to you both.
Hey Tim! Great to know that you are joining us on this adventure and enjoying it almost as much as we are. Look forward to having you onboard to see for yourself after we launch.
Great progress and very fast for such a complex build job!
Regarding the CPP system, I would be interested in hearing some specifics on that. Sure you will post photos once installed, but some questions before that… How is this particular system controlled exactly? I mean is all the mechanics integrated in the gearbox and you just control a lever or something similar outside the box to control the pitch, or is it controlled outside the box? Can you feather the pitch fully or if not then how much? Can you use different gear box or do you “have” to use the same brand?
Hi Andy, sorry for this delayed response while I am out traveling internationally for a month.
I think most of your questions on CPP props can be answered very well by a paper which Michael Kasten wrote years ago and does a very good job of summarizing these props and comparing them to fixed props. It was written in 1998 but not much has changed with CPP since and I think you will find it a very good use of your time to read. You can find the paper on Michael’s site at http://www.kastenmarine.com/CPprops.htm and if you have the time you may want to look at some of his other equally well written articles.
There is also this YouTube video that shows an actual CPP rotating its blades https://www.youtube.com/watch?v=qgSfrqAYopg and this animation https://www.youtube.com/watch?v=U8AfsG2x0qk that does a nice job of showing what goes on inside the hub of a CPP prop and how the CPP push rod inside the prop shaft rotates the blades.
As to your specific questions there are two arrangements of the hydraulic servo which controls the pitch adjustments and you guessed both of them quite correctly. The servo pitch controller is a hydraulic cylinder which uses hydraulic pressure to move a piston back and forth and this motion is transferred via solid push rod that slides precisely forward and aft inside the center of the prop shaft. Within the hub of the CPP prop this motion is transferred to a mechanical system that rotates the blades and thus adjusts the pitch. Very simple and pretty bulletproof as verified by the very reliable use in many thousands of mostly commercial boats.
The first type and the one we are using in Möbius has the servo cylinder integral with the CPP gearbox that bolts to the aft of the engine replacing what would have been a traditional transmission. The end of the engine’s crankshaft is bolted to the input shaft of the CPP servo gearbox then usually goes through a set of reduction gears driving the output shaft which is bolted to the flange on the CPP prop shaft. The second type has the servo pitch control cylinder integral within the prop shaft assembly and would then use a traditional transmission on the engine to do the gear reduction and provide a reversing gear.
In addition to the different location of the servo pitch control cylinders these two types are quite different in that the first one with the dedicated CPP servo gearbox usually has no reverse gearing as the prop shaft and prop only turn one direction and reverse thrust is provided by rotating the prop blades through the neutral zero pitch position. This arrangement suits power boats very well especially for slow speed close quarters maneuvering as you can feather the prop very easily between foreword and reverse thrust very smoothly with no “clunking” between a forward gear and reverse and this also enables you to easily hold the boat in a steady position when there is wind or current trying to move you.
For sailboats however you want to be able to have prop blades that can be “fully feathered” when the engine and prop are not being used such that their pitch is relatively parallel with the prop shaft and creates the least amount of drag. Therefore CPP systems on sailboats will almost always be of the second type with the servo pitch control cylinder integral with the prop shaft assembly and having enough travel on the push rod to rotate the blades from the fully feathered position to the full pitch position.
This somewhat answers your question about being able to use different bands for the various parts of the CPP system. In the first Servo Gearbox type I think they would pretty much need to be from the same company but for the second type, there is no gearbox and so whatever transmission you have on that boat can be easily connected to the CPP shaft system.
In our case we will therefore have a lever, though some boats use a wheel, which transfers the motion of the lever to the pitch control lever on the outside of the CPP Servo Gearbox which in turn controls the movement of the servo pitch control cylinder. In operation it will look much like a fixed prop forward/reverse lever with “neutral” being when the lever is pointing straight up and pushing it forward or back will equate to moving the boat forward or reverse. With this Servo Gearbox type system the engine is always engaged with the prop shaft and thus the prop and shaft are always turning both in the same direction and all the time even when in “neutral” position. Therefore there is a “clutch” cylinder, controlled by a simple on/off switch at the helm, which can disengage the gearbox from the engine when needed.
The huge advantage of a CPP system is that you are able to adjust the load on the engine to be “just right” and achieve maximum efficiency at any speed in any conditions. It is true that fixed props, mostly due to their smaller hub size, are at least theoretically able to produce slightly higher efficiency than a CPP but the big caveat is that this is true for only one specific condition and it then becomes much less efficient in any other conditions. Therefore CPP makes the most sense and delivers the most benefit on boats which operate under varying conditions. XPM type boats such as Möbius will operate under quite a large range of conditions due to changes in the fuel level/displacement of the boat, sea and wind conditions and speed of the boat through the water. Therefore the use of a CPP system allows us to dial in the perfect pitch under any and all conditions and thus enable us to achieve maximum efficiency of the transfer the power to the prop, load on the engine and fuel burn rates. For our use case this adds up to a very significant set of benefits and hence our choice to go with a CPP system was an easy one.
The decision was made even easier when we worked out that contrary to popular opinion of those who have not had a CPP system and as you will read in Michael’s article, there is very little difference in overall cost between CPP and fixed props when we are talking about building a new boat.
I hope that this and Michael’s paper provide a reasonable explanation of how CPP propeller systems work and let me know if there are any additional questions I can answer.
-Wayne