Moebius Skipjack (Sculpin) - RC Groups
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Jun 11, 2013, 12:05 AM
Submarines, etc.
tsenecal's Avatar

Moebius Skipjack (Sculpin)

a little something i have been working on... it will be going in the water for ballast testing this weekend... then hopefully paint, and the Colorado Crew regatta the weekend after that.
Last edited by tsenecal; Jul 16, 2013 at 03:23 PM.
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Jun 13, 2013, 01:37 PM
Time For Me To Fly!
fastmax's Avatar
Very cool. Would love to see some vid of it in action.
Jun 15, 2013, 07:59 PM
Submarines, etc.
tsenecal's Avatar
ballasting and buoyancy testing done. new non-traditional ballast pump a complete success.
quick paintjob for the regatta is done.

next stop, maiden voyage at the regatta.

fastmax, should have video then.
Jun 15, 2013, 08:53 PM
GSMB Member
ken_nj's Avatar
Damn, 4 days, 19 hours, 54 minutes from the first post.
Jun 16, 2013, 12:21 AM
Submarines, etc.
tsenecal's Avatar

Actual start on the sub was the second week of April, so, more like 8 weeks.

But yeh, it was simple and quick.

I will be posting more details later, especially on the ballast tank/pump setup.
Jun 16, 2013, 12:35 AM
Registered User
tchalfant's Avatar
Tim, would you show us more of your WTC? What is unconventional about it? Photos?
I forgot to say how cool it looks in the water. Great job there!
Jun 16, 2013, 11:18 AM
Submarines, etc.
tsenecal's Avatar
Originally Posted by tchalfant
Tim, would you show us more of your WTC? What is unconventional about it? Photos?
I forgot to say how cool it looks in the water. Great job there!


the ballast tank pump is built from thunder tiger neptune spare parts, a brushless motor, brushless esc, with basic receiver failsafe setup thrown in for safety. it fills or empties a bladder with water, and it appears i guessed the right speed brushless motor, the bladder is filled and emptied at a reasonable speed.

photos soon. right now i am busy getting the rest of the subs ready for next week.
Jun 22, 2013, 08:26 PM
Submarines, etc.
tsenecal's Avatar
just a quick update, the skipjack had its maiden voyage today at the Colorado Crew regatta, got video and pictures of it running on the surface, and submerged. I also took a bunch of photos of its WTC, i will be uploading them here on monday. the maiden voyage went great, only problem was the throttle setting needs to be dialed back to about half of what it currently is, max speed is about a scale 80 knots. ran it for 30 minutes with no leaks.
Jun 23, 2013, 08:56 PM
Submarines, etc.
tsenecal's Avatar
okay, so i lied, the photos wont be uploaded monday...

i have a couple of really short videos of the maiden, and a few photos, as well as some links to parts that i used for the build.

if you have any questions, ask.


Moebius Models Skipjack r/c conversion (0 min 33 sec)

Moebius Models Skipjack r/c conversion (0 min 58 sec)

Jun 23, 2013, 09:05 PM
Submarines, etc.
tsenecal's Avatar
okay, so now the photos of the WTC:

basically what i have done is taken some major replacement parts from the thunder tiger neptune and adapted them to work for me. by buying these replacement parts i was able to save a ton of money versus buying from the germans.
Last edited by tsenecal; Jun 23, 2013 at 09:39 PM.
Jun 23, 2013, 09:15 PM
Submarines, etc.
tsenecal's Avatar
finally a parts breakdown, and methedology, again ask questions:

the moebius sub kit itself retails for around $90.00, i bought mine from freetime hobbies. I also bought the g-factor brass prop from them: it took a lot of finesse to get the prop and prop shaft aligned nicely, i ended up using JB Weld to bond the prop to the propshaft, after machining the shaft to fit the prop.

i bought a 4mm propshaft and stuffing tube from cornwall model boats, not sure which length, but the stuffing tube is about 5"... maybe $10 plus shipping.

i bought the u-joint for the main shaft from cornwall as well (4mm to 4mm):

polycarbonate tubing, 2 feet at mcmaster carr, $16 per foot for the 3.5" tubing

four endcaps, molded by me, from my "inventory" of available sizes.

2 1/8" shaft seals from

the motor and esc are hobbyking parts, designed originally for 1/10 r/c rock crawlers:

(mine is silver, but the new version is anodized red)
and the programmer:

by getting the programmer, i am able to set the max speed of the motor to a more reasonable 6000 rpm at the prop, rather than the 15000 that the motor/esc/battery combo actually produces.
subtotal of parts: $60

then the thundertiger neptune motor mount/shaft seal, as well as the shaft, and u-joint:
i bought the shaft and u-joint, knowing i already had the cornwall part, but this allowed me to make it so that i could have a short stub shaft coming from the WTC, and a solid mounted shaft in the boat, connected together with the u-joint

all three of these parts total about $30

then the pump:
($10 at tower, as much as $60 elsewhere)
pump motor:

pump esc:

the pump esc is the most expensive individual part, and i had it sitting in my parts box, otherwise i would have tried a 1/18 esc from hobbypartz or hobbyking, something to look into later, the ESC is overkill for the specific situation.

and finally the battery:

i will be recharging this tonight, i ran the skipjack for a total of 45 minutes over the weekend. the single battery runs both the main motor and the pump, i really want to know how much juice i used.

last but not least, i built the tech rack out of 1/8th polycarbonate sheet, as well as 4 "brackets" that i have moulded out of the same resin as the endcaps.

this all works because of the sombra labs SL8 and its failsafe programming capabilities, without it, i wouldn't have done the brushless motor on the pump.
Last edited by tsenecal; Sep 05, 2013 at 12:02 AM.
Jun 24, 2013, 01:54 AM
Registered User
tchalfant's Avatar
Great information and photos & video. Thank you for posting.
Would you repost the ESC link?, it is the same as the pump motor. And what features in the Sombra Labs RX did you use? would you elaborate?
Jun 24, 2013, 08:16 AM
Submarines, etc.
tsenecal's Avatar
pump esc url has been fixed.

the basic functionality of the sombra labs receiver allows me to set the failsafe position for the pump esc so that the bladder is emptied when the receiver loses signal (Program Value 96). this isn't as nice as the brushed pump controllers that norbert and engel sell, they also have low battery and pressure failsafes as well, but for 90% of the failure scenarios, the simple signal failure is enough. this receiver programming mode allows all 8 channels to be set to a user defined value, so along with the pump being set to "empty", all other channels are set to equally useful values (neutral dive planes and rudder, no throttle)
Jun 24, 2013, 10:28 AM
Registered User
tchalfant's Avatar
Thank you. I see what you meant. On the ESC you programmed it, that is a separate device from Castle?

I really liked how you were able to move forward submerged in a nice slow fashion and I think that shows off the design very nicely.
Thank you again for sharing.
Jun 24, 2013, 07:36 PM
Submarines, etc.
tsenecal's Avatar

two escs:

1) sensored hobbyking ESC for the main motor, programmed with the programming box to give it max forward and reverse speed of 40% of original max speed (roughly 6000rpm), as small a deadband/neutral range as possible, low startup speed, and very low motor timing. basically setting it up opposite to how it would be setup for a fast car.
the sensored setup is how i am able to get such nice slow speed capabilities. max throttle is a little over scale, giving me a "panic" get out of harms way capability.

2) castle sidewinder micro ESC, used for the pump motor, and the only programming i have done for it is to give it zero brake, zero delay and 100% forward and reverse so when dealing with the pump, fill and empty take the same time. like i said, the castle esc is way over kill for what it is doing, but it was sitting on the shelf. programming was done with a castle link.

I would not use the castle if i had to buy a new one. if i were to buy a new one, it would probably be this one: , and whatever programmer card it needs to set it up with 100% forward and reverse.

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