Moebius Skipjack (Sculpin) - Page 3 - RC Groups
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Jul 09, 2013, 05:23 PM
Man from Atlantis
Sub culture's Avatar
Couple of things worth thinking about with brushless.

Sensored motors are generally only supplied for the car boys, and they're always 500 size motors. This will work for some but not others. They are vastly overpowered for any sub, most boats only need 50 watts or less of power, and these motors tend to be in the 150watt and higher bracket.

There are many smaller outrunenr motors available which are better suited to submarine use, unfortunately they are unsensored.

Sensorless control is pretty good, certainly fine if you like to scoot around the lake, and aren't too bothered about very slow speed running, but in no way does it match up to a good brushed motor and ESC combination for control finesse.

Retrofitting sensors to outrunners motors is possible, but only well suited to those who are a dab hand with a soldering iron. If you want to find out details of this, have a gander at folk fitting large outrunners to bicycles- they are retrofitting sensors to them to make them compatible with the throttle controls.
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Jul 18, 2013, 12:57 AM
Registered User
Tsenecal did you use David Merriman's fittings kit on your Sculpin?
If not and you used the kit's stock rudders and stern planes can you discuss how you did it? Thanks
Jul 18, 2013, 07:38 AM
Submarines, etc.
tsenecal's Avatar
i did not use merrimans fittings kit.

i used a combination of brass fittings, square brass tubing, and small brass bolts. the brass tubing is glued into the plane/rudder using 24 hour marine epoxy (system 3 t88 epoxy), replacing the original plastic piece. the rear diving planes have a brass tube at the hull end, and a #70 brass bolt holding them in place at the outside end. although merriman states that the rudders have to have their pin position moved, i didn't do that, and they seem to work fine. inside the hull, a dubro collar with a brass servo horn is fitted to the brass tube. the original holes for the original pins on the diving planes were enlarged to fit the new brass tubing. the rudders had plastic tubing inserted into the original holes to reduce their size to the size needed for the brass tubing. the forward diving planes are fixed, and do not move.

i used the brass bolt on the rear diving planes because i want to be able to remove everything if a repair or maintenance is required.

I will try to get photos of the stern section and appendages at this weekend's regatta. the plastic parts are thick enough, and when basically filled with system three T88 epoxy to mount the brass tubing, they appear to be strong enough to handle the forces well enough. time will tell if they need to be upgraded.
Last edited by tsenecal; Jul 18, 2013 at 12:29 PM.
Jul 18, 2013, 02:50 PM
Registered User
Extremely well done, Tim! I admire your work greatly.
Sep 16, 2013, 08:35 AM
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HeavyCruser9's Avatar
G'day mate,

Is the G factor brass prop threaded? or just bare bore? Thinking of getting one for my Skippy (As of Sunday I have the Revell version) Am pretty sure I will do USS Shark....

Just gathering research info (and parts...) before I commence any building.

Cheers Bruce
Sep 16, 2013, 05:30 PM
Submarines, etc.
tsenecal's Avatar
Originally Posted by HeavyCruser9
G'day mate,

Is the G factor brass prop threaded? or just bare bore? Thinking of getting one for my Skippy (As of Sunday I have the Revell version) Am pretty sure I will do USS Shark....

Just gathering research info (and parts...) before I commence any building.

Cheers Bruce
the G factor brass prop is an exact knock-off of the original plastic part, which means the "hole" in the prop is actually square, approximately 1/8" x 1/8" (slightly more than 3mm x 3mm) it is intended to be installed on the static model using the same parts the plastic prop would use.

I milled a 4mm stainless steel shaft to fit the hole in the prop, and then glued the prop to the shaft.
Sep 18, 2013, 03:14 AM
Registered User
HeavyCruser9's Avatar
Cheers Mate!!

I am getting the Caswell fittings kit so I shall use that prop then....for now! I might get George Sitek to make me a shiny brass one later!! This will be my first foray into subs so I will be keeping it a simple as possible.

Cheers Bruce

PS I managed to pick up a Graupner/JR MX22 and 5 Rx's(3 7ch and 2 6ch)in excellent condition which I will be using in the boat.
I shall keep an I out for the really cool 10ch and 12ch Rx's for other special projects.....
Sep 18, 2013, 03:17 AM
Registered User
HeavyCruser9's Avatar
Also it really amazes me the creativity different modellers use to make these projects function.

Looking forward to further installments of your build!
Sep 18, 2013, 08:22 AM
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tchalfant's Avatar
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I am not sure if he is going to add more to the build.
These photos are Tim's Sculpin running at Keystone CO this past Summer.
It was a beautiful sub to watch run.
Sep 24, 2014, 08:09 PM
Submarines, etc.
tsenecal's Avatar

redboat asked how i keep the endcaps in place. in the original setup, i used 15 brass flathead machine screws to hold the endcaps on. I didn't like having to remove 15 screws to work on the sub, so i spent last winter re-doing the sub's WTC.

the WTC is now a single cylinder with two endcaps, with bulkheads in the hull. the WTC sits between the bulkheads, the endcaps cannot move due to the bulkheads. there are no screws anymore. the pump pickup now penetrates the forward endcap, and a waterproof switch allows me to turn on and off the sub without having to remove an endcap.

the two tech racks are still the same as they were before, with a 4500mah battery sitting beneath a tray that the balloon now lays in. the tray keeps the balloon from moving around, and if the balloon breaks, the tray will hold the majority of the water. I have no idea how long the battery lasts, i was able to run the boat for the entire weekend at this year's regatta (3 days total) without re-charging it.

i also changed the method that the two halves of the hull are held together. it used to have a 4/40 bolt going through the frontmost alignment pin. now there are four brackets with magnets imbedded in them. two on the lower hull, two on the upper hull. the magnets hold the two hull halves together.

only one set-screw on the propshaft needs to be loosened now to remove the WTC.

also... for your added enjoyment, a closeup photo of the 8+ channel 433mhz receiver and 5cm antenna.

Last edited by tsenecal; Sep 24, 2014 at 08:40 PM.
Sep 24, 2014, 08:50 PM
Registered User
Any failsafes to avert flooding in case something goes with the pump and balloon burst. See also you reverted back to a brushes drive motor.
Sep 24, 2014, 09:38 PM
Submarines, etc.
tsenecal's Avatar
Originally Posted by redboat219
Any failsafes to avert flooding in case something goes with the pump and balloon burst.
there is no failsafe to stop the pump from overfilling the balloon. there is a thing called space. i don't know what will happen when the balloon has filled all the space in the tray and the pump is still filling the balloon. the tray is designed to hold the water if the balloon starts to leak. the receiver failsafe is set to EMPTY the balloon...

the problem would be if the pump ESC shorts out and gets stuck filling, and the balloon starts to leak, and the tray overflows...

Originally Posted by redboat219
See also you reverted back to a brushes drive motor.
nope. the motor is the same brushless motor it had in it before (check post #10 ) this sub has had nothing but brushless motors (both primary and pump motors) for its entire life.
Sep 24, 2014, 09:51 PM
Registered User
In the original build there was a center bulkhead.
It was not water tight because it had a vent hole in it.

So if I trust my work I can eliminate the heavy bulkhead and use just a thin bulkhead just to keep the ballast balloon in place. I see you used a tray that does this and allows you to get your battery farther forward. I'm going to have to think about that one. It has posibilities.

Also half the electrical equipment is move forward of the ballast tank balloon.

I have so much going on at the back cap, moving the water tube and a switch or two to the front cap would do wonders for my planned building.

Tim, thanks so much for this update. It helps a lot and will get me moving on the cylinder stuff.

Thanks ,
Ralph --- SSBN 598
Sep 24, 2014, 10:32 PM
Submarines, etc.
tsenecal's Avatar

it allowed me to move the battery forward, and almost double the size of the battery. i went from a 2600mah to a 4500mah battery.

there are now two 1/8" 3" diameter acrylic bulkheads at either end of the tray, with 1.25" side walls. a 3/16" brass tube penetrates the forward bulkhead and holds the balloon in position. the tray will hold alot of water.

i also set the max throttle on the motor at 30%, it originally was at 40%... sub was too fast at 40%
Last edited by tsenecal; Sep 24, 2014 at 10:42 PM.
Sep 25, 2014, 01:13 AM
Registered User
I remember you were at 40%.
I also remember you said you had plenty left to get out of the way if you needed to.
So, I planned to start at 30% on main motor.

Looking at my transmitter, I think I can limit the pump motor if I need to or just restrict the tubing diameter to reduce flow. OR just a valve so I can change the flow if I need to.

I have to get more work done on this boat. It's starting to want for the water.

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