Thunder Tiger Yellow submarine seen on Norimberk - Page 3 - RC Groups
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Oct 09, 2007, 02:50 PM
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Ok folks the Neptune has finally arrived in the UK with the official importers, should have it in kit form by the weekend!

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Oct 09, 2007, 06:56 PM
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any links plz?
Oct 10, 2007, 03:35 AM
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I think this link will show you.
Nov 12, 2007, 02:22 PM
Registered User
Dear all,

I was lucky enough to see the Neptune in action.
The owner of my model shop has received a demonstrator model from Thunder Tiger and allowed me to see the first trial.
I had to promise not to tell his name or place, because he doesn't like to be mentioned in a web forum. Nevertheless, I can write about the Neptune and show some photos.

Yesterday we tested the sub in a deep swimming pool. You may see additional pictures in the other thread:
Here are my first comments.

The Neptune seems to be well designed. It's simple and allows easy assembly and maintenance.
The outer hull is made of thick plastics. The front bubble is just snap-on and the rear cone is screwed.

The inner WTC is somehow different from the standard.
It is a 5" tube, but the end flanges are much larger than the tube itself, roughly 7". They allow room for 4 external pull rods.
Each flange has three vertical holes for waterproof joints. The overall six holes are used for the rudder levers (two), the switches (two - mains and camera), the camera SMA connector (one) and the water intake (one).

All the joints stay on the side of the flanges, therefore the front is fully free for a large window with 6 bolts. This window can be easily removed to reach the camera, the recharge connectors and the fuse.
Going on, 4 screws allow to remove the camera support frame and, at this point, even the battery can be removed from the bow aperture.
Everything is possible without disassemblying the WTC, by just removing the transparent front window.
In my opinion, the easy assembly is the major quality of the Neptune: a screwdiver seems to be sufficient to disassemble and rebuild the entire sub (I imagine this will take few hours, but by now my friend doesn't allow me to try...).

I expect that this clever construction will allow a large number of modifications and improvements.

The Neptune is a static diving, research sub model. It doesn't need to be fast, and in fact it isn't.
Maybe someone will find it too slow and replace the motor with a more powerful one, but in my opinion the speed is sufficient to enjoy the model and have effective use of the inboard camera.

A good feature is the quick response to the rudder, which stays in the propeller stream. Turning radius is closer to one boat length, i.e. 3 feet only.
On the contrary, the effect of the dive planes is not so good, probably because of the low speed.
In the future, I would like to adjust the ballast position and move the center of gravity a bit upwards: pitch variations will be easier. (By now, I can do nothing because I'm still waiting for MY model...!)

There is a ballast bag with peristaltic pump for static diving. The glass upper canopy clearly shows the waterline position and is useful for sharp trimming, in order to reach a neutral buoyancy.
The user is also helped by the yellow color, the light weight, the endurance up to two hours (depending on the throttle, maybe less).

If no critical defects will be discovered, this model seems to be a good promise .
(but only if TT will let us have it in a reasonable time...! )

Ocean's One
Nov 13, 2007, 02:20 AM
Registered User

The Neptune looks good, how did it perform holding her position under the water?
Nov 13, 2007, 04:52 AM
Registered User
Regarding the capability to stay at constant depht, I discovered that the boat response is rather slow and the operator has enough time to apply corrections.
It takes about 20-30 seconds to fill the ballast bag entirely, so that a one-second action on the radio stick will fill or empty the bag minimally. The control action is quite sharp.

I prefer operating in this way. First, static dive until the turret is entirely submerged, with just the top or the upper ring touching the water surface. Now the boat has neutral buoyancy.
Then I can dive dinamically, using depht rudders (they are not very effective, but work well if the boat is neutral. There's no upthrust to win)

I may stop the Neptune at the desired depht and check its position. If it slowy moves up or down, a short action on the pump is sufficient to correct its position. A very short pulse is needed: not more than 1 second, then wait for the boat response before next correction.

As always, the critical point is the pilot's awareness about depht changes. It's not so easy to see through the water, but I expect the inboard camera will help a lot.

The Neptune is equipped with a basic electronic depht control. Actions on the stick directly correspond to buoyancy variations. The right way to find the neutral position is left to the pilot's skill.
To be honest, it's already so much: some other products on the market don't even offer static dive. However, a large improvement of the Neptune is still possible.

For instance, a nice book of Norbert Bruggen's describes some electronic devices to keep the sub at constant depht. They use a depth sensor and can be interfaced to the existing electronics. The result is to change the pilot's order "decrease the buoyancy by two grams" into "add half foot to the actual depht value", which is for sure a better info.
Needless to say, these circuits are complex and maybe expensive. i don't know whether some manufacturer offers them (maybe Graupner. Does anyone know?)

However, I think it's too early to discuss about improvements. Even if not perfect, the boat response is sufficiently good and I hope that some practice is all that I need.
I'll keep you informed. I would like to run another test and reach my Titanic wreck on the bottom: in this way I will discover how accurate is the sub when approaching the wreck and understand more.

Ocean's One
Last edited by Ocean's One; Nov 13, 2007 at 05:00 AM.
Nov 13, 2007, 09:02 AM
Registered User
Thanks for that Ocean, another point i was wondering about (mine has not arrived yet!) is the connections at the front of the vessel? are these twelve volt connections for the camera?

Nov 13, 2007, 10:28 AM
Registered User
I hope I understand right.

The connector on the upper part of the bow is the SMA connector for the video cable.
The camera takes power from the submarine battery, but needs to trasfer the video signal to the surface by wire, because 2,4 GHz don't pass through the water.
The cable supplied by TT has an SMA connector on the submarine side. On the other end there is a RCA connector that can be plugged to the majority of video devices, and also to the new "Polyphemus" video receiver that can be installed directly over the TX, I was told.

By now I can't tell you more because, sadly, in our trial the video cable was attached to the sub, but nothing was connected to the other end of the cable!
Hopefully, future will be better...


P.S. Did I understand right? Or was you meaning the black and red plugs that can be seen behind the front window? Those are recharge connectors
Nov 13, 2007, 11:40 AM
Registered User
Yes they were the ones i meant, i have my camera set-up ready, i will be using the 2.4ghz with the transmitter aerial lying on the water surface on a buoy of some description.
Nov 13, 2007, 02:43 PM
Man from Atlantis
Sub culture's Avatar
If you want a pitch controller, there are a couple on the market.
Look here-

and here-

Don't bother trying to make the circuits in the Bruggen book, they're dated and don't work as well as commercial offerings.

A pitch controller will be sufficient. A pitch and depth controller, like the one posted in the second link is a nice luxury, but far from essential in a boat like the Neptune.

Nov 14, 2007, 12:03 PM
Registered User

thank you for your comments and the web references. They are really VERY useful.
I believe you, a combined pitch+depht control is probably too much for a small boat like the Neptune.

A simpler pitch control should be an easier solution.
To be honest, even this one seems to be too much on the actual Neptune.
On the model I tested, the ballast is placed very low and the metacentric height is quite high. Therefore, the boat is very stable and has low pitch variations in any case (this probably reduces the effective manoeuvrability...).

At this point, the best improvement will be to move some ballast upwards and, yes, install the pitch control.
I have to understand better, run some more test and, of course, wait for the opinion of someone else (Russ, what about your Neptune?)
In the meantime, thank you again.



I understand you want to install your own camera and not the optional part supplied by TT. If you wish, tell me and I'll verify if it can be simply installed in the Neptune (I have the model available and can make measures on it and check the voltage).

On the contrary, I would like to know something more about your buoy. I'm building my own one and think that sharing experiences is very useful.

Nov 14, 2007, 12:54 PM
Man from Atlantis
Sub culture's Avatar
Some modifications that would help this boat.

1. Fit a prop with more blade area to get a little more speed. Hydrovane response at low speed is often rather poor, which is why research boats tend to be fitted with thrusters. You can always throttle back when you want to go slower. Propshop make some very nice screws, affordable, with lots of pitch and blade area. They're cast in silicone bronze.

2. If the forward hydrovanes aren't operational, consider making them so. Fit a leveller to the rear servo, and you can use the forward vanes to adjust your depth, the leveller will adjust the rear vanes to correct the pitch of the boat. Effectively the boat will dive and surface level.

3. There is a large weight underneath the boat. If this was hooked up to a spare channel, you could have servo adjusted weight distribution. This is well covered in Norberts book.

Nov 14, 2007, 04:01 PM
Registered User
Thank you, Andy.

1) Good idea. I'll start looking for propellers even if, as I wrote, I'm still waiting for my submarine. This sub belongs to my friend and I haven't enough freedom to modify it.

2) I already heard about this technique and I agree it could be effective. However, if you look at the pictures of the Neptune's WTC (beginning of this thread), you'll see that both forward and rear hydrovanes are connected to the same servo, via two external rods. Probably, a way to install two independent servos exixts, but is not so easy and the modification should be well designed. We have to refine this idea and, previously, have all our Neptunes in our hands (by the way, have you ordered the sub too, or have some different model?)

3) Good, but here the weight is the external ballast, outside the WTC. Moving it means another hole in the WTC, a waterproof joint and some additional leverage. Not so easy, do you agree? Maybe shifting the battery is simpler...

Nov 15, 2007, 01:49 AM
Registered User
Oceans, my Neptune is still not here .

However i am trying to organise the camera gear beforehand, is there any kind of fixing plate behind the screen to mount the camera on? is there any chance you can take some pictures of the area just behind the front screen?

Many thanks

Nov 15, 2007, 02:14 AM
Man from Atlantis
Sub culture's Avatar
Okay to answer some of your questions.

I checked the photos and confirmed what you said about the vanes being linked. More effective control could be made of these control surfaces by seperating them.

You could run an additional glanded shaft through the top of the front bulkhead, like a mirror image of the rear bulkhead. A further gland through the bottom of the bulkhead will serve the purpose of a control rod for shifting the ballast weight.

You could move the battery, but I think you would have to modify the internal frames quite a bit to achieve this.

I don't own a Neptune, and it's unlikely I'll purchase one. I do have a couple of smaller submersible craft I have scratchbuilt nearing completion. They're about 14" long and use twin tiltable thrusters instead of hydrovanes.

To you guys interested in underwater video work, check out the Oregon scientific ATC2K camera-

A lot of model submariners are using these now. They give a very good image, and if you use them in conjunction with a live video signal you can see what you are shooting.

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