Dumas Akula Class Submarine Build - RC Groups
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Sep 23, 2004, 09:01 AM
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P. Tritle's Avatar

Dumas Akula Class Submarine Build

I know this thread should probably be over in "Submarines", but since it's a "scale" boat, and our ponds are so murky that it will spend 98% of it's time on the surface anyway, I'll start here.
Anyhow, the opertunity to review the Akula Class Sub Kit from Dumas came up recently, and since I've never built a Sub before, I thought this might be a pretty cool project to take on -- so here goes.
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Sep 23, 2004, 09:14 AM
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P. Tritle's Avatar

The Kit

The kit itself is really a pretty simple, straight forward method of construction as I see it. The design is basically of Vac-Formed Styrene plastic, with clear covers on both the equipment and battery compartments.
Power and guidence is provided by a single Dumas High Torque motor and reversing ESC, 2 standard servos controlling the rudder and diving planes, with at least a 3 ch radfio required. The forward diving planes are not controlled, but rather, are manualy trimmed for best diving performance.
The kit is complete with everything needed to run the model except for the radio, motor, ESC, and battery. Also included are 2 plan sheets, one with construction details, the other with external scale details, and a fully illustrated book of building instructions.
Sep 23, 2004, 09:24 AM
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Building the Boat

I have discovered over time, that the best way to a proach a project with which I am totally unfamiliar, is to start at step 1 and follow the instructions all the way through the project -- which is what I'm doing with this one. So far, so good.
The hull is prepared first by cutting it from its carrier sheet and sanding the mating edges. Once that's done, the equipment tray mounting rails in the lower hull, and stiffeners in the upper hull are glued in place.
Once the rails are in place, the equipment tray is trimmed and fitted into the hull.
Sep 23, 2004, 09:36 AM
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Installing the Tray

Once the equipment tray has been trimmed and fitted, the servos are mounted, and the tray glued in place in the equipment box. I glued the tray in using Household Goop and clamped the parts in place and let it dry over night. The equipment box was then glued into the hull using silicone. Dimentions are provided on the plans for the proper location of all these components, and so far, everything has gone in without a hitch.
Sep 23, 2004, 09:45 AM
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Fitting the Upper Hull

Once the equipment tray is in place and the glue dry, the upper hull is cut in two, and the forward section glued in place on the lower hull. The rear section will be removeable, retained by rare earth magnets and a series of alignment tabs.
I deviated just a bit from the plans here, and made the alignment tabs significantly larger then recomended, as the .020 styrene looked a bit flimsey, as originally designed.
The next step will be to install the diving planes. stay tuned, it's gonna' start getting good.
Sep 24, 2004, 07:47 AM
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Hooking Up the Controls

With the servos mounted and the hull basically done, the diving planes and rudder are next on the agenda.
The rudder assembly was soldered together and installed in the hull, and the control horn installed and adjusted. Take a little care to sand the baring block to shape so the rudder goes in nice and straight.
The diving planes are set up next, using a common shaft and control horn to acuate. The shaft is 3/16 dia. brass with a slit cut in both ends to accept the .025 brass diving planes. The shaft is bushed through the hull sides with a 7/32 O.D. brass tube bushing. With everything in place, the planes are soldered to the shaft. A little care needs taking here so's not to melt the hull sides. I wrapped a piece of wet paper towl around the shaft, against the hull to disipate the heat. Soldering was done using a small torch and Sta-Brite solder
Sep 24, 2004, 07:55 AM
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Installing the Pushrods

The pushrods are bent from .062 brass rod. There's a guide bushing made from 2 sizes of brass tubes, which must be added while shaping the pushrods. Then once the rods are installed, a silicone tube water seal is added over the bushing. Finally, the whole assembly is installed and adjusted, with the bushings glued into the back of the equipment box and sealed with silicone. Once everything was secured, the rudder and diving planes were set up and adjusted to neutral trim.
Sep 24, 2004, 08:03 AM
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Installing the Stuffing Box

Now that the controls are all in and working it's time to glue the stuffing box in place. The rear tube support was trimmed and glued in place at the stern, and the tube glued in place. Bondo was used to secure the tube into the stern. Since the only support at the aft end of the tube comes from that joint, be sure the attachment is secure.
From here, it's back to cosmetics for a bit. The upper hull details will be done next, so keep an eye out for updates real soon.
Sep 24, 2004, 09:39 AM
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RGinCanada's Avatar

Thanks for taking the time to post this build! The sub is looking very good so far. What I don't yet understand is how the kit will maintain watertight integrity. I'll sit on my hands, and wait for it to unfold....


Sep 24, 2004, 01:18 PM
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Tony Oliver's Avatar
I agree with you Pat - no move to submarines required as it is equally applicable to scale.

Interesting model which would pose problems for me. For example, in your third post you say 'The hull is prepared first by cutting it from its carrier sheet and sanding the mating edges' - how exactly do you do that? I hate vacformed stuff. It's usually very thin and the transition at the right-angle bend makes it even thinner. I always have trouble getting a straight line on mating surfaces. Any hints on how you got it so neat and tidy?
Sep 24, 2004, 04:49 PM
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Looks great so far. I've been looking at these. Do you think they would be able to operate in a 36'x18' swimming pool?

Sep 24, 2004, 09:24 PM
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P. Tritle's Avatar
Tony, Thanks, I was hoping that no one would take offense to the Sub review in the boat section. I justified it by being a "scale" boat as well.
I agree that working with large vac-formed sections can bring out the "best" in me too (if you know what I mean!), and yes, the half shells are a bit on the flimsy side until the internal components go in --But, in this case it's not as bad as it might seem. I miked the hull section and found it to be .045 thick, so it probably started out as .062.
To get started, you first score the hull sections along a clearly difined line along the inside of the shells, which is about 1/8" above the fold line where the plastic takes the 90 degree turn at the bottom. It's best to take your time and make the scribe slowly so the knife doesn't slip off the line leaving a crooked cut. I made 3 light passes with the knife, then broke the plastic along the scored line and basically "tore" the carrier sheet away from the hull section. It is a bit tediouse, but really not all that bad. The good news is that that is the first step in the instructions, so once that's done, it's all down hill from there!
Once the hull sections are seperated from the carrier sheet, tape a full sheet of 100 grit sand paper to a flat board and rub the hull section over it to clean up the irregularities along the edge. Go at it with only a light to moderate preasure, or it will have a tendancy to take too much off the middle, leaving a big arc at the mating surface of the upper and lower sections. Then, lay the hull section on the board and look for high or low spots, which will be fixed with a more "localized" effort, only where its needed.
The process of trimming and dressing the hull sections took about an hour and a half, but a little extra time spent here will save a bunch later.

Hope this helps, but if you need more detailed specifics let me know and I'll do what I can. Actually, doing this kind of thing isn't new to me, as I have built MANY 1/48 and 1/32 scale vac-formed plastic airplane kits over the years, so the technique really isn't "new", it's just "bigger". If it's your first time out though, TAKE YOUR TIME and work CAREFULLY. Like anything else, it's another modeling skill that will devope only by doing it.
Besides, I get bored easy, so I need one like this to wake me up every now and again. And just as an added incentive, the next one up after this is project is the Dumas "Typhoon". I've been looking at that kit for YEARS and am truely "chomping at the bit" to get started!!!
Sep 24, 2004, 09:36 PM
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Dave, Judging by the description in the instructions, a 36' X 18' pool should do nicely. They say the boat will turn about a 7 foot radius -- that gives you 2 feet on each side to spare. I wonder though that with a bit more rudder throw, you might be able to tighten up that radius a bit.
The good news is that I'll be attending the RCHTA show in Chicago with the Dumas guys in October, and will be driving the p-type Akula there, so will find out just how well it does work. And hopefully, mine will be done, and posibly even maidened by then to boot.
Sep 24, 2004, 09:58 PM
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Ray, The "concept" of sealing the model water tight -- in theory anyway -- is really quite simple. The idea is that the equipment comartment top is glued permanently in place with clear silicone caulk. The pushrods are running in brass bushings with silicone fuel tube seals. I will also "pack" the slip joints with a generouse dollop of waterproof grease, as an added measure of security.
The battery tray is sealed with foam rubber gasket, and "clamped" together all the way around the perimiter with styrene tubing split down one side to form a spring clamp. The battery leads exit both compartments running through silicone fuel tubing, sealed with silicone. The battery connector will run wet, so the battery can be charged from the outside, without having to remove the battery box cover. I will probably add a "test tube" to preasure test the battery box for leaks too.
Another interesting feature is the way they access the on/off switch. A plastic bottle neck is glued into the equipment compartment, sealed with it's own cap. So, to water test in the bathtub, I'll make up a cap with a tube in it, conected to a long piece of fuel tubing. The compartment will be submerged, then I'll blow into the tube and look for bubbles, imediately showing any potential leaks without filling the expensive parts full of water.
Now, with all that having been said, the boat is only designed to run at a depth of about four feet, which isn't all bad, much deeper then that you probably couldn't see it all that well anyway.
Sep 24, 2004, 10:58 PM
CG Bob's Avatar
Now, with all that having been said, the boat is only designed to run at a depth of about four feet, which isn't all bad, much deeper then that you probably couldn't see it all that well anyway.
Due to the design of the watertight boxes, 4 feet is about the maximum depth the AKULA can go. Changing to a watertight cylinder (Small World Models, D&E Miniatures, et al) a greater depth can be achieved. Since Dumas recommends using the AKULA in a swimming pool, the maximum depth at which it can be controlled is about 3 feet. Depending on the chlorine content and other chemicals that may be in a pool, the radio signal is reflected at about 3 feet. Dive below that, and you lose control of the model.

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