I'm working a 24" tugboat as a dedicated rescue boat. Since it doesn't qualify as a warship and it will be used at MNCC battles, I'll put the build thread here. I started with a generic 24" fiberglass hull that I picked up. I'll be modeling the Nokomis, YTB-142, so that works out to about 1:48 scale. Since this won't be a combat ship, there will be no vulnerable windows and I'll include lots of floatation. The plan is put a bow thruster and kingpost crane with a winch in it to make rescues easier. I got a little work done on it Saturday, the subdeck is partially installed and hole drilled for the stuffing shaft. The motor will be geared about 9:1, as long as I can figure out how to keep the gear under the deck. That's a 126 tooth gear. It should turn a 2" prop using less than 2 amps on 6 volts.
It doesn't seem tiny to me. It's 3 times the length of my first tugboat and therefore 9 times the displacement. It's all relative I guess. The hull is from Microglass. It is their generic 24" tug hull. Very nice quality too.
Very cool indeed. That will no doubt come in very handy with me around. Have you given any thought to a salvage ship? I may be running a battlecruiser again next year, and I may be needing more than just an occasional push in to shore. Any progress on the PT boat? Mikey
I've made some progress on the tug recently, although I continue to be distracted by a multitude of other projects. The stuffing shaft is tacked in place and I made measurements to determine the biggest prop that would fit, which turns out to be 55mm, or just over 2". To double check my measurements I cut out a 55mm circle and mounted it on the shaft. With the diameter verified I ordered my prop and the bow thruster and I am impatiently waiting for it to arrive. I started on the rudder, installing the upper rudder tube and lower support. The rudder is roughed out, final shaping and fiberglassing will wait until I have the prop and can check all clearances. Can you guess what 1:96 scale convoy ship prototype is in the background?
It's not a submarine, although I just got done reading "Clear the Bridges" about the USS Tang and started playing with drawings and displacements for a sub just last night. That project completion is far in the future. The ship is a YOG-86, a gasoline yard oiler. Below you see it with the tugboat and PT boat, both 1:48 scale compared to the oiler's 1:96 scale. The original has a 174' LOA, so the model is less than 22", or smaller than my Golo.
Woo Hoo! My prop and bow thruster arrived! The prop fits, somewhat of a relief because there is not a lot of clearance. I made a prop adapter for the shaft and did a trial mount. Then I had to stop by the hardware store to get a brass 10-32 jam nut to finish assembly. So the stuffing shaft is now permanently mounted and the rudder shaped and fiberglassed. I also finished the pulleys to connect the motor and prop shaft. So next is the motor mount and installation of the bow thruster.
Mark installing internal armor in his 96th scale oiler, and the bow-thruster in his rescue tug. Sweet! Mikey
I got the bow thruster faired into the hull and hooked up to an old servo amp for control. Hot tub tests show that it has reasonable thrust on just 6 volts and only 0.25 Amps.
I plan to mix it with rudder to start. I'll set it up with two mixes: the first will push opposite of the rudder for tight turning, and the second will push in the same direction as the rudder. I think the second mode will be more useful, because it should allow me to keep the tug tight against the hull of the ship I'm pushing in. I will probably use the aileron channel, so I can use the right stick to turn it on independently from the rudder if I want. I will be able to select between any of the different modes with the mix switch.
The motor mount is complete and the drive shaft hooked up. Even though I don't have the rudder hooked up yet, I had to take it out to the hot tub for sea trails. I hit the throttle and WOW! I thought the 9:1 reduction would make it slow and powerful. It's powerful alright, but it's not slow. It throws a pretty good rooster tail. I think I'll look into increasing the reduction some more - maybe change the pulley from a 1:1 to a slight reduction. Amp draw with a 6 volt SLA was only about 3 amps. I saw 4 amps once, but most of the time the prop was cavitating so it wasn't loading up completely.
I was able to get the deck fitted this weekend at the build session. I also picked up a 13:1 gear and changed the ratio to the prop. It still cavitates a lot, but it is getting closer. I'll wait until I can make real sea trials before I mess with the ratio any more. As you can see in the picture, the gear is so big it sticks up through the deck about 1/8". I have also started to work on the kingpost crane. I have the servo and servo block that forms the rotating base of the crane temporarily mounted. Next is figuring out how to make and mount the winch.
