Another week goes whizzing by faster than a MIG welding flash and with lots more progress on the building of the hull for our new boat and soon to be full time home, the mv (motor vessel) Möbius, our all aluminiuum 24m / 78’ eXtreme eXpedition Passage Maker or XPM here at GreeNaval Yachts in the Antalya Free Zone. Thanks for your interest and welcome aboard.
I will continue with the usual style of a series of annotated photos taken throughout the week and end with a similar video version that compiles the videos I shot during the week. Hope you enjoy and please be sure to leave your comments, thumbs up/down and questions in the comments section at the end.
As per the title of this week’s post there is a lot of “baffling” work going on as Team Möbius begins assembling the fuel and water tanks which will soon form the entire below waterline portion of the hull, as well as assembling the framework for the bow section of the hull and continuing to finish the welding all the stringers and bulkhead frames to the deck plates which were put in place last week. Lots to cover so let’s jump right in starting with the baffling part first.
With the eXtreme amounts of liquids we want to carry on Möbius for ocean crossing passage making, the hull has been designed such that pretty much everything below the WL (water line) is filled with either water or diesel fuel. I’ve done a quick colouring of the profile view to the left to help you see how this is all positioned.
In total we will be able to carry about 14,000 litres/ 3700 USgals of diesel and up to 5700 L / 1500 USG of water. The water will all be potable, as we only fill them with the close to pure H2O generated by our high volume watermaker which makes about 220 L/hr 60 USG/hr. However the for such a large tankage of water onboard is primarily to serve as movable ballast. This enables us to trim the boat for different sea conditions as well as balance weight as the fuel is used up. All tanks are divided up into multiple independent compartments with plumbing and valves which enable us to move both water and fuel from any tank to any other tank as needed.
Stripping away everything but the framework (sorry Möbius) I’ve taken these two snips of the 3D model, this one looking up from below the WL shows some of the transverse and longitudinal baffles in Red ….
The magenta surfaces are the tank tops and all the green squares are tank access hatches. The access hatch holes were not CNC cut because we will wait until we finalise the interior arrangements to decide exactly where they will go in order to provide full access to every area within all the baffled compartments for future inspection and maintenance.
As you can see, this integral grid like structure makes the underwater portion of the hull eXtremely stiff and strong. Furthermore, with all of the hull below the WL being tanks we have a significant built in safety factor in the very unlikely event that something should puncture the thick hull plates. A feature we definately hope not to test out!
Here is one of the many piles of baffle wannabes …………..
If you were wondering, the tanks need to be so fully baffled to reduce what is known as the free surface effect which is the technical marine term for what we might more commonly know as “sloshing”. The more detailed definition is:
Free surface effect is the change in stability of a vessel caused by liquids moving about freely in a tank or hold. As a vessel rolls, liquids in tanks or breached compartments accentuate the roll by moving freely from side to side of the tank accumulating first on one side and then the other, and may adversely affect the stability of the ship. The free service effect can be reduced by having baffles in a tank to reduce the free movement or by either emptying the tank or filling it completely.
Given the enormous quantities of diesel and water we will be carrying on Möbius you can understand why we treat this with extreme care and seriousness as it can cause serious instability as noted in the definition above when we are at sea. Fortunately the solution is relatively simple, divide the tankage into multiple independent tanks and put lots of baffles in every tank to reduce the free surface effect.
The top edge of each baffle plate has a 10mm flat bar welded on to provide a surface for welding the tank tops onto after the hull is completed. Our head welder Sezgin was kept busy welding these flat bars as well as continuing to weld all the stringers that were installed last week onto the deck plates so it was a very busy week for Sezgin and he is very fast and very good.
Other Team Möbius welders were busy cranking out more baffles for Sezgin by tacking the flat bar onto the top edges of baffles. You can see how they tack diagonal braces to hold the bar and plate perpendicular when they are being fully welded in place.
Along the centerline of the hull the tanks are divided to create separate tanks on each side and in some places a “void” or space between them is created such as in the middle area of the hull where the large “house bank” of 2v battery cells will go. So some of these are not baffles per se as they form sides of the tanks in these places and must be reinforced further with stiffeners similar to the style you saw in the bulkhead construction. Here you can see one such baffle plate with the stiffeners tacked in place ready to be fully welded with a continuous bead.
For scale, my thumb is on a piece of 12mm flat bar and the stiffeners are 10mm.
Here is a stack of tank side plates stacked up and ready for assembly.
The baffles run longitudinally or lengthwise in the hull and are notched or welded into the transverse running frames such as these ones stacked up here. The frames are spaced one meter apart along the entire length of the hull.
Here are some of the bottoms of these frames with their temporary flat bars tacked in place to keep them flat while being worked on and welded. You can see all the slots cut into their outer edges the stringers which will be slide in there once these frames have been positioned along the length of the keel.
On the left of this shot closer to the center of this frame bottom, you can see one of the tank side plates mentioned above with its stiffeners welded in.
This will give you more sense of scale with Enver standing inside one of the tank cavities. He is clamping that length of 12mm flatbar and will tack it temporarily in place to keep this side plate perfectly straight and will do the same to all the others before tacking the baffles fully in place.
This will give you a nice perspective on how the baffling system works. That large vertical slot you can see in the upper center of this photo that is cut into the frame bottom is where the 25mm keel bar runs down the entire length of the hull forming an extremely strong backbone and central reference point for the entire hull.
That cavity in the middle is one of two which form the battery box for our mammoth 24v house bank of batteries giving us total capacity of 54kWh. These batteries have a mass of 1320 kg / 2910 lbs BUT it is “good weight” in that it sits as low down as you can possibly get and does double duty as ballast which helps with the ride and comfort at sea and perhaps most importantly part of what makes this hull self righting. This was one of several attributes of our sail boats, all monohull sailboats, which we were not willing to give up.
You can now see how these grids of closely spaced baffles very effectively deals with the free surface effect I mentioned earlier.
Uğur is our “main man” on the shop floor and always busy. Here he is using the big hydraulic press to bend one of the 12mm flat bars that reinforces one of the frames. Check out the video at the end to see him in action. If you look very closely you will see that the CNC has etched lines along the bend where Ugur positions the edge of that steel bar on the press and bends it a bit at each line to create just the right radius and angle of the curve.
Here is a closer look at one of these large radius flat bars welded into one of the many frames.
Which provides a good segue to go check out what’s been happening up at the bow where you will see more examples of these frames.
Working our way forward, here we are looking towards the bow from what will be the aft Port (left) corner of our Main Cabin. This is the “ceiling” of course as the hull is being built upside down for this first stage and you can see a slightly different construction as Uğur and Mehmet position one of two very robust I beams running down either side of the centerline. All the longitudinal stringers have been laid in place on the deck plates in preparation for sliding the frames over them to form that interlocking construction you have seen used throughout the deck construction.
Looking at the other side of this Frame/WTB #4 we follow Uğur and Mehmet forward as they start assembling the particularly puzzle like assembly of different shapes and sizes of plates that make up the deck at the bow.
To help orient you with the design of this bow area I’ve grabbed this quick rendering of the 3D model. I will go over all the elements of this in a future post but you can see the interesting “sidewinder” mounting for the big solid 125kg / 275 lb Rocna/Manson anchor, the large hatch into the spacious forepeak storage with lid shown both open and closed, the Samson post, cleats, windlass, etc.
Note too how the deck drops down and slopes down toward the bow so that all the water and anchor muck drains off easily.
Looking at the very tip of the rounded bow at deck level, if you look closely or click to enlarge this photo you can see the red laser they have lined up to show the exact centerline of the boat as the assemble the various pieces and tack them in place.
This is the incredibly helpful laser sight unit which projects perfectly straight sight lines in whatever direction you want. SO much faster and more accurate than the old stretched string we used to use.
Note Frame #2 on its side against the wall behind Mehmet waiting to be inserted in the appropriate slots in the decking.
Stepping back a bit you can see that drop in the hull is nice and deep at the very tip of the bow. If you look back at the rendering above and the one below at the very end of the bow just below the Rub Rails wrap around the nose of the bow, you can see what I’ve been calling the “donut” which is a very thick rounded AL tube for the snubber line when we are anchored. Dennis did a great job of also positioning this such that it also forms a perfect drain off the deck and back into the sea below.
One more quick snip of a rendering of the bow framework, this time upside down to help with what you are seeing in the pictures. Red Frame #1 is fully welded in place on all sides to form a permanently sealed watertight “crash bulkhead” which we hope to never test but adds to our SWAN factor. (Sleep Well At Night)
The forepeak storage area runs from Frames 1 to 4 so 3m / 10 feet long and will provide a huge amount of full headroom storage for lines, fenders, anchor gear, pumps, tanks, etc.
This area is made of thicker 12mm plate compared to the 8mm on the rest of the bow deck to provide an even stronger base for the ground (anchor) tackle and the critically important windlass that brings in the chain and anchor.
This is one of the 12mm anchor bow roller cheeks anxiously awaiting it’s turn in the assembly process. Look closely or click to enlarge and you’ll see it’s mate plate laying on the floor in the upper right side of this photo.
Sticking with Uğur and Mehmet and finishing off strong, check out the top portion of what will become Frame #15 which is where Christine’s Office / Guest Cabin steps up to the Galley area in the SuperSalon.
Whew! Another busy and productive week for Team Möbius and your summary video below as promised.
Hope you enjoyed this week’s update and please add your questions and suggestions in the comments section below. Thanks again for joining us, wouldn’t be the same without you!