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Author Topic: cheap and simple RC sub/dorsal fin project  (Read 40845 times)

red181

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Re: cheap and simple RC sub/dorsal fin project
« Reply #50 on: July 04, 2014, 08:52:56 PM »

if someone builds one that works, build two! O0
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U-33

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Re: cheap and simple RC sub/dorsal fin project
« Reply #51 on: July 04, 2014, 10:38:12 PM »

Ah, good man yourself...I'll hang on and buy one of yours, mate.


Rich
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Rich

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U-33

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Re: cheap and simple RC sub/dorsal fin project
« Reply #52 on: July 06, 2014, 10:57:41 AM »

Right gentlemen, about this shark.


I've just had a long chat to Andy about making up a basic shark kit, he's well advanced in making the mould up already.  The idea is to have just a top 'deck' vac formed out of styrene, with either a styrene fin or a latex one(to give a little movement and life to it), supplied with a wtc consisting of the tube, mounting brackets,  a pair of end caps, a styrene tray to hold the radio, watertight exits for the rudder/planes control wires, and maybe a prop shaft as well. That would leave you as the buyer to supply and fit your own three channel radio, motor and battery pack of your choice, as most of you would have these items laying around in the workshop, so that would keep the cost down.


Now, what we need to gauge is the amount of interest in this...the initial idea is to produce half a dozen or so and see what happens from there. I've already put my name on one, so that leaves five to sell. I will add here that this isn't going to be a huge production run, just to knock up a few for those of you who fancy something different. Making shed loads of cash isn't the plan, it's not going to be a commercial set up by any means of the imagination, Andy just wants to cover his expenses really.


So chaps, what do you think about it? I'd be interested in your comments/criticisms/whatever...if you fancy one, please let me know and we can go from there.


The all important price...yes, working on that at the moment, but probably be around 120-150 ish (a very big ish) depending on the cost of the vac forming, and the purchase of the wtc tubes and materials for the end caps. Obviously, the more Andy can sell, the cheaper the price will be.

Rich


(note to moderators...I hope this is ok under Mayhem sales rules to post this up here, if it takes off then maybe it could be placed under a different heading? It's not really a commercial enterprise, so that's why I added it onto Paul's original posting)
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Rich

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Subculture

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Re: cheap and simple RC sub/dorsal fin project
« Reply #53 on: July 06, 2014, 01:50:19 PM »

I don't think a shark is very good choice of subject to model unless it's going to operate fairly slowly or you cheat by adding rear control surfaces.

A shark's pectoral fins aren't very good for controlling pitch as they're too close to the c.o.g. A real shark bends its body to control pitch giving extremely effective vectored thrust, not something very easy to do with a stiff plastic hull though.

A better choice would be a dolphin or killer whale, with the horizontal tail giving large control surfaces located far aft giving exceptional control for a fun aquabatic model.

U-33

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Re: cheap and simple RC sub/dorsal fin project
« Reply #54 on: July 06, 2014, 03:18:54 PM »

I understand that, Andy...but the idea is to just have a visible shark fin, not the complete body, or a scale shark at all. Most people just want see a fin gliding along, and with the addition of a set of planes, to slide under underwater now and again.


A plank of wood with a fin attached would be ideal, but at least this will look more like a shark if it has a black back visible when surfaced.


Rich
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Rich

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essex2visuvesi

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Re: cheap and simple RC sub/dorsal fin project
« Reply #55 on: July 06, 2014, 05:52:38 PM »

I understand that, Andy...but the idea is to just have a visible shark fin, not the complete body, or a scale shark at all. Most people just want see a fin gliding along, and with the addition of a set of planes, to slide under underwater now and again.


A plank of wood with a fin attached would be ideal, but at least this will look more like a shark if it has a black back visible when surfaced.


Rich
Norbert Bruggen succeded with a dolphin
http://www.modelluboot.de/KITS/Delfin_Ordner/Delfin.html


some video in action
https://www.youtube.com/watch?v=2TmiU5Wa6Y0


maybe take a look at the construction and see if it something that could be used as a basis


BTW the leveller will be in the post in the morning
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U-33

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Re: cheap and simple RC sub/dorsal fin project
« Reply #56 on: July 06, 2014, 07:30:39 PM »

Chaps, I think you're missing the point here...


Norbert Bruggen's dolphin was a submarine in a fish's clothing, and I agree, it's a grand piece of kit. But...this is purely a little bit of fun, designed as a shark fin, to be driven along the surface looking menacing, with the capability to slip under the surface as and when the user wants it to.


It's not supposed to be a fully operational, all singing, all dancing submarine, purely as something a bit different to use on your local lake, or for guys like Paul(Red181)to operate in conjunction with his Orca boat.


Norbert's dolphin costs an awful lot more than Andy's shark will, and don't forget the title of this post..."cheap and simple RC sub dorsal fin project.."




Rich
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essex2visuvesi

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Re: cheap and simple RC sub/dorsal fin project
« Reply #57 on: July 06, 2014, 09:33:46 PM »

Rich
sorry, I didnt mean he should buy one.... I was jus suggesting that maybe some of the design and theory could be used in the shark
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red181

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Re: cheap and simple RC sub/dorsal fin project
« Reply #58 on: July 07, 2014, 08:45:59 PM »

If I was at the beginning of the project I would certainly have put my hand up for one, but I am financially a bit deep here, with the MMB kit, and some extras, so as much as I want to say yes, I need to fully commit to this project until I am forced to give up. U33's explanation is exactly what I want, a bit of fun, with the dorsal fin drifting around, and the ability to slip under the water to the depth of the fin. I am probably getting close to assessing if this will actually work, which it should as it is a commercially available kit that has been around from a reputable seller for a while, so for the time being I will carry on.
I have now fitted new pushrod connectors to the rear planes and rudder to give more throw, and therefore more control. I have crudely changed the static front planes to moving ones, and will shortly attach pushrods from rear to front, so servo deflection will now operate front and rear planes, any comments on this would be appreciated. Also, I have a leveller on the way courtesy of essex2visuvesi, not quite sure yet what this will do without a degree of depth control.
Now here is a really dumb question, ever doubted yourself?? well I have that feeling now. So, when diving, will the trailing edge (rear) of the operating planes go up, or down?????? This could be the problem with diving at anything above snail pace speed :embarrassed: :embarrassed:   
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Subculture

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Re: cheap and simple RC sub/dorsal fin project
« Reply #59 on: July 07, 2014, 09:32:10 PM »

If you want the shark to behave in a predictable fashion I would separate the front and rear hydroplanes. Have the rear planes controlled directly from the leveller e.g. no receiver input, just power up the leveller with a 5 volt feed.

Control the front planes manually to change depth. With this approach your shark should dive and surface in a very controlled fashion.

Dive plane angle should be about +/- 30 degrees, with a maximum of 35 degrees, beyond that you will just stall the control surface.

If they're still ineffectual at that angle then you need to think about increasing their area

red181

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Re: cheap and simple RC sub/dorsal fin project
« Reply #60 on: July 07, 2014, 10:58:02 PM »

Hi Subculture,

I cant control the front planes, as all the pushrods etc exit the wtc from the rear only, hence thinking of controlling the front planes via the servo controlled rears, and the question remains, do the trailing edges of the rear planes go up or down for diving. Any other ideas please keep them coming, but I have no direct control on the front planes, I think the original plan was decoration only, or maybe some stabilisation, in the build instructions they are actually optional

thanks
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Subculture

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Re: cheap and simple RC sub/dorsal fin project
« Reply #61 on: July 08, 2014, 09:57:05 AM »

You can either put in an extra control rod at the front, or use a u-bend or reverse motion lever to actuate the forward planes from the rear of the module.

If you remain with rear planes only, the boat will work, but it will dive by porpoising, whereas I think what you are looking for is a more subtle motion where the shark dives in a level fashion.

Regarding the rear planes, if you have them working only, to dive the trailing edges of the planes point down, and vice versa to come up.

red181

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Re: cheap and simple RC sub/dorsal fin project
« Reply #62 on: July 08, 2014, 04:05:42 PM »

Oops :embarrassed:
I had the planes the wrong way.  That will help :}
I like the  u bend to the front planes It will be difficult to remove the battery with anything coming out of the front endcap. Ill give it a go witg inproved travel and planes set the right way :-))
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Subculture

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Re: cheap and simple RC sub/dorsal fin project
« Reply #63 on: July 08, 2014, 09:01:04 PM »

Haven't you ever dabbled with model aeroplanes?

Basically rear hydroplanes behave like the elevator on an aeroplane. They can work somewhat differently if/when combined with forking front hydroplanes.

red181

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Re: cheap and simple RC sub/dorsal fin project
« Reply #64 on: July 17, 2014, 11:50:30 PM »

progress at last with some time off work. I have made new servo control rods, and done a much better job with them, the delay was caused by finding true 2mm rod, most is 1.67mm with m2 thread, the tubes that exit the wtc where 2mm. The loaned leveller arrived, but here is the  thing, on the bench I have had it working, but, if I use the tx to simulate a dive, the leveller fights the tx and throws the servo to surface, which I suppose its doing the right thing??

There is a dip switch fitted, if I leave that on, the the lights are lit up, but nothing is happening to control the servo, so what is the point of the dip switch then? If removed, the unit works if I simulate a dive or surface, but it takes over from the tx...... I'm confused now!

Its actually one of these



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Subculture

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Re: cheap and simple RC sub/dorsal fin project
« Reply #65 on: July 18, 2014, 09:38:30 AM »

It limits the movement to prevent crash diving/extreme manoeuvres. Some levellers override the levelling completely when you extend the control beyond a certain point e.g. half way. LR3 from Norbert Bruggen works that way.

With the microgyros leveller you can turn the levelling off by using a switch to short the two pins adjacent to the servo connection. Perhaps that's what you're doing?

There is a small pushbutton switch to set the controller modes, this can also be selected by infrared (use a torch).

red181

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Re: cheap and simple RC sub/dorsal fin project
« Reply #66 on: July 19, 2014, 10:49:40 PM »

ok makes sense now, I was violently tilting over 45 degrees, that would have been some crash dive!
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red181

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Re: cheap and simple RC sub/dorsal fin project
« Reply #67 on: July 24, 2014, 10:40:50 PM »

for any onlookers, hols means a two week lay off, I am not ignoring all the help! c u soon :-))
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red181

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Re: cheap and simple RC sub/dorsal fin project
« Reply #68 on: July 28, 2014, 12:03:05 AM »

Well managed to get a quick session in before work this morning, but it will the the last, and it went very well. I should be abler to look in from time to time, so comments most welcome to help with this project.

I now have, courtesy of a fellow member, a microgyros leveller. Even though Mike at Microgyros has emailed and spoken on the phone, I am not sure how this should be set up. I changed all the servo rods, and fitted much better connectors. I found that trying to shape a rod from the servo, out of the wtc, and to the planes or rudder, was virtually impossible, so I have done them all in two pieces. A nice straight rod out of the wtc, so no binding, then a second piece to the planes. The wtc is black, so I cannot see inside, which I think presents a problem with the leveller. I hook everything up, seal the wtc, fit in hull, and check for level running. In the pic below you can see how much deflection I need on the rear planes to surface run. The front static planes also have to be angles in a similar fashion, to stop the immediate diving. If this was a model aircraft, I would say the cog was way off, but I don't understand this sub stuff, so some advice would be appreciated.

This will now surface run, it was quite windy this morning, so not very good conditions in the choppy water, but, with some small inputs on the elevator control, it will surface run. Thing is, although I know on the bench the leveller is working, and working the correct way, I have no idea what its doing in the model. Very small inputs create the dive, and if I only dive for a few seconds, I know pretty well where its going to come up, so far so good. I cannot seem to stay at a constant depth. I was thinking levelling off at fin depth (with a barrel attached to indicate this) I should with some stick adjustments be able to maintain some sort of reasonable constant depth (especially with the leveller thingy) but this is not happening, suggesting I am not setting the leveller up correctly. Does it need to be set up every time I hook up the battery? and by the time I have forced everything back in the wtc all things have probably moved. I have to have the motor end of the wtc sealed up at home, its way too fiddly at the lakeside, and all the electronics go in that end. I suspect I need  to cut out a clear "window" so I can see the leveller?
Do I need all that trim on the planes? without that it just immediately dives. Good thing is no roll on the turns, so it looks quite good, however the turning circle is still massive, so I need to increase the rudder area  as even with the larger control horns it turns better, but not enough.
Ballasting seems to be very critical, sitting still level on the water does not really have any influence when its running, the smallest piece of foam making all the difference. I am looking forward to trying again on a calm day.
Any input most welcome!, we will beat this :-))
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red181

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Re: cheap and simple RC sub/dorsal fin project
« Reply #69 on: July 28, 2014, 12:09:20 AM »

second pic in last post shows the planes angle to achieve surface running, below pic shows rudder deflection at maximum, not enough
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CyberBOB

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Re: cheap and simple RC sub/dorsal fin project
« Reply #70 on: July 28, 2014, 04:14:49 AM »

I don't really know much about submarines, but as for knowing your depth, the barrel sounds like it would work.  I haven't watched the movie in a long time, but I seem to remember multiple barrels, you could maybe tow 2 or 3, all on different length strings, to keep track of things.


Keep up the good work, I have been following the thread with interest, its such an unusual subject.
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Subculture

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Re: cheap and simple RC sub/dorsal fin project
« Reply #71 on: July 28, 2014, 06:48:36 PM »

I'll raise a few points.
It seems you have some experience of model aeroplanes- good stuff. I fly too, and there's a lot of correlation between a model aeroplane and a sub.

You will know that if you build an aeroplane with wonky control surfaces, or you get the c.g out, it will never fly well if at all. Same goes with a sub. You can get away with more in a sub because things work slower, all the same a sub with nicely arranged fins will always work better.

The C.G position of a sub varies depending on the hull shape. Going back to an aeroplane, we tend to balance about a third back from the leading edge. You can go a bit more than this, as you no doubt know, but the aeroplane becomes twitchier and more difficult to fly.

With a shark, it's essentially a spindle shape hull. A good starting point for the boats c.g is 40% of the boats length in from the bow/nose. So if your boat is about two foot long, you want the boat to balance at about 9-10" form the front. Moving the C.g forward of that point will make the boat more stable, but less responsive to rudder and hydroplanes, and vice versa for moving it astern.

Regarding the leveller. Basically there are three gain settings, low, medium and high. I'd start with a low setting for a small boat like yours. There's also a setting that enables you to level the sensor in the boat. It's vital the leveller is fixed to a firm foundation that doesn't change when you open the WTC. My own observations of the MMB WTC is that the rack inside is just a floppy plate of plastic- not really adequate IMO. I'd think about beefing it up by making a structure that remains self supporting and stiff.

Regarding setting the unit via infra red, and the lack of a transparent WTC. I agree it's a nuisance. I liked some of Mike's earlier units which incorporated a reed switch, so you could set things up by swiping a magnet. The majority of dive modules out there are transparent or have clear endcaps at the very least, so i guess most people are happy. You can still set things up outside the boat though.

red181

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Re: cheap and simple RC sub/dorsal fin project
« Reply #72 on: July 28, 2014, 11:07:19 PM »

thanks subculture, makes sense :-))

I was under the impression if it sat level static on the water, as the pic earlier, I was ok, but I get the cog stuff, so.. forget ballast to make it sit level, take it all out (only a few pieces of depron etc) get cog correct, then start thinking of the ballast. The leveller is fixed to the plastic plate, that has been modified to be more rigid, but I can do better.

Unfortunately no option to make a window in endcaps, they way its made, and I don't really fancy cutting holes in the wtc, so will set up the leveller on the bench. I fitted it on double sided tape, like a gyro on a rc heli, as my understanding is its doing a  very similar thing, just on a different plane surface. I have it set on medium, so will change to low.

A holiday break from tomorrow, I can look in, but the sub is now away for a few weeks, I think its getting there now, I know it works to a fashion, it just needs setting up correct, and some final tweeks might just produce an acceptable set up. :-))
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salmon

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Re: cheap and simple RC sub/dorsal fin project
« Reply #73 on: July 29, 2014, 02:04:21 AM »

I have Mike's leveler in my Skipjack. It is an excellent product. I found that my leveler needs to be set to higher sensitivity the smaller the sub. That would be the only point that I would differ from Andy's excellent advice.
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Re: cheap and simple RC sub/dorsal fin project
« Reply #74 on: July 29, 2014, 01:31:06 PM »

The best I can offer relates back to my experience with a shark back in the days before digital photographs, internets and things. My shark would nose dive as a default setting, and as mentioned previously, was probably due to a total lack of understanding related to the C of G of the model. I was recently reading an article relating to an american model of a Los Angeles Class sub and the term 'up bubble', where on the surface the sub runs nose up to reduce the effect of water over the sloped bow driving the sub underwater in an uncontrolled manner, then ballasts to a horizontal level for normal, submerged operation. Would a constant 'up bubble' attitude help with the operation of this model? And how would it effect the gyro? Worth further discussion?
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