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[old shrimper]

hi guys
i have the steering arm sorted i got rid of the clevis and went to ball joints all good now no binding
BUT i would like more rudder for slow maneuvering  i have the the servo set in the center and the rudder amidships i get the same amount of rudder port and starboard
i tried shortening the tiller arm about 3mm with some holes closer to the boss  but the servo seams to bind up and i cant lengthen the sevo arm as its at its max
the rudder is free to turn to 90deg eather way when not conected to the sevo
some pic of the in stall
 im getting about 45 deg see yellow square under the boat  [size=78%]ing










[/size]

[Umi_Ryuzuki]

Sounds like you are getting plenty of throw already.
More than the ship can really use without acting more like a speed brake.
Try a different rudder design.
Perhaps a simple Fishtail rudder with a triangle or square(diamond) bar on the trailing edge.
Or for a bit more complexity, use a Becker Rudder.

Then the servo and rudder throw can remain within the area of non binding movement, and
the trailing edge will give the prop wash a larger diversion.

 

[irishcarguy]

Take Umi's advice & use a Becker rudder, you will not reget it. Mick B.

[old shrimper]

ok guys ill have a look at one and see how much work there is to change it


it has about a 8ft turning circle at full speed ?
but is a dog to dock , a lot of its the power i think as its ether on or off sort of thing and way to fast for a 30x10 pool and cavatates like crazy at full throttle in rev
if you have out of the water and watch the prop turn you can get it turning slow but give another 1mm of stick and its at full noise very annoying


i have taken the 60mm 4B off and put a 2B 48mm on so that should drop the  thrust  a lot 

[w3bby]

...I tried shortening the tiller arm about 3mm with some holes closer to the boss  but the servo seams to bind up and I cant lengthen the sevo arm as its at its max.....

From a non scale guy but if that is a fixed bushing aren't you putting a lot of bend in the control rod when applying max rudder? This in itself will cause binding problems I would have thought.
I would slot the bulkhead and seal with a rubber gaiter for a start.

[grasshopper]

Agreeing with Umi- san, soldering a strip across the back edge of a rudder creates a Fowler flap effect, should increase rudder effectiveness.


The prop' you have fitted in the picture seems a strange choice, for the kind of hull shown I would go with a very shallow pitch 3 bladed prop, the shallow pitch alleviating some of the paddle wheel effect suffered when in reverse.


Is your speed controller set up properly? Some ESC's have auto set-up but can be set up or reprogrammed to give smoother control over stick range.

[old shrimper]

grasshopper
the prop in the above pic is the one that came in the KIT , i hated it so put this one on  but it is to fast in a confined space with the steering control i have at the moment ,
and the touchy throttle
pic





wbby
the control rod does NOT touch the bulk head as it is notched to clear at full lock both ways ( my be i took the pic before i did that )




the viper ESC i have does have auto set up,HOW DO i reprogram it to have a more variable speed band ( its at full throttle at about 1/8 trigger then the rest is nothing just full speed
thanks bob

[grasshopper]

The pictured brass propellor still seems quite a high pitch, could you let us have more info on motor type, which Viper ESC you have and voltage you're running everything at?


Viper esc's are good but aren't they designed for model cars? you may find that it isn't being loaded enough hence the poor range of throttle control. The newest type also prefer to be used with modern 2.4 GHz equipment.

[old shrimper]

hi
the ESC  is a viper marine 25
the motor is FMA 540 on 6.1 red
all on 12v lead acid batt 7.2 ah
the TX controller is a 2.4Ghz 3ch FS GT3 with a matching RX
the servo is a hi tec standard
i would run it at half throttle if i could LOL
i went 12v because i was told the MFA would be gutless on 6v
i think 6v would have been close to the mark
thanks bob

[malcolmfrary]

All of the Vipers that I have used have had a small button to put them into programming mode if pressed within a couple of seconds of switch on.  The ESC then "learns" where neutral, full forward and full reverse are by means of you moving the TX throttle stick into those positions.  It then remembers those positions and is then very smooth in response, giving a proportional response to stick position.  It sounds like it might have gained some unexpected programming along the line, and need resetting to factory defaults, but a read of the instructions that came with it should tell you.
The rudder throw is exactly what it should be, the turning circle under way is what should be expected (2 and bit times the boat length?).  Close in maneuvering usually involves coming to a stop, applying full rudder, then blipping the throttle to make water flow over the rudder kick the back end round and cause the boat to start to rotate before the boat starts to move forward.
You have to realize that the kit manufacturers probably knew what they were doing when they supplied the parts that they did. As such, changing the specification before trying out the makers intended is not really the way to improve on the original, and probably will do more harm than good.  At the same time, the 4 blade brass does look a lot better, and with the ESC properly set up, either should offer good control.

[Martin (Admin)]

Can you show a photo of the rudder ...

[Bbadger]

Hi I am new to the forum, only just dipping my toes in to the water, but have experience in RC and robotics.


I would guess that the problem you have with the power is down to two possibilities
1.  The esc needs re-programming - when you set up an esc you need to set the end points of the throttle - if the throttle was only a fraction of the way down when it was set, the esc will give maximum power when it reaches this point.  Answer is to re-program - tere is a download option here http://www.mtroniks.net/details1.asp/ProductID/183/sid/2/Viper-marine25.htm


2.  You can control the throttle response from your Tx - look for the EXP setting - this allows you to set a percentage - which translates as changing the way the throttle is applied - yoyu can set it to give fine control where you move the throttle quite a lot to get a very small change in speed - and then near the full throttle it get less sensitive  -  you need to play with this to find what suits you.

[old shrimper]

THANKS GUYS
i will look in to the ESC  reprograming and the EXP tomorrow
and report back
pic of the rudder 55m H   x 35mm W approx

[craggle]

If you want more rudder throw but the servo binds up....


Are the black fittings on the end of the pushrod the type that go both sides of the servo arm / tiller arm? If they are there is only a limited amount of travel before the servo arm will hit the bottom of the slot that goes over the arm.


Hard to explain but a ball joint sitting on top of the servo arm with a push on cup will allow a full 360 degree rotation but the links you have at the moment will be limited to 250 odd degrees before the arm hits the fitting.


Maybe look at ball joints and cups from radio controlled cars to give a larger range of travel. The rudder looks good on the kit so be a shame to add something out of scale.


Craig.

[inertia]

I have handled three examples of this particular MTroniks ESC (25A) and all have displayed just the symptoms described here i.e. large amounts of stick movement do very little until you get to about halfway, then the motors ramp almost straight up to full speed. The motors also displayed a marked tendency to "hunt" at full speed. Reprogramming the throttle acceleration slope might reduce the problem but I would advise changing the ESC. I have no commercial interest in pushing any type these days but you might consider Electronize or ACTion. Both are British-made and very reliable.
As to the rudder movement, 45 degrees is more than enough. As has been said, any more and the rudder starts to become more of a brake. I think that once you sort out your ESC issues then docking will be much less of a problem.
Dave M

[old shrimper]

If you want more rudder throw but the servo binds up....


Are the black fittings on the end of the pushrod the type that go both sides of the servo arm / tiller arm? If they are there is only a limited amount of travel before the servo arm will hit the bottom of the slot that goes over the arm.


Hard to explain but a ball joint sitting on top of the servo arm with a push on cup will allow a full 360 degree rotation but the links you have at the moment will be limited to 250 odd degrees before the arm hits the fitting.


Maybe look at ball joints and cups from radio controlled cars to give a larger range of travel. The rudder looks good on the kit so be a shame to add something out of scale.


Craig.

the fittings i have are ball joints they sit on a half round on top of the tiller arm same as the ones on your car there about 3 mm clearance between the rod and the ball joint
you can rotate them 360 deg ( if you disconnect one end of coarse ) they are not clevises i had them on and they did lock up [/quote]

[Rob Wood]

I hope I'm not stating the obvious, but rudder authority is gained in only one sure way: by increasing the volume and force of water it deflects.

I suggest trying this simple experiment:

Cut a piece of thin but stiff plastic, such as an old hotel key card, and tape it to the rudder, so that the rudder is longer, fore and aft. The idea is to increase the area of the rudder that is in the thrust wash of the prop. Then see if your turning radius decreases. If it does, it indicates that with the current setup, you simply aren't getting enough thrust against the rudder to produce the sort of rudder authority you need.

Simple ways to increase rudder authority of a barn-door-type rudder:

• First remove any flex in the linkage. If the linkage isn't stiff, the rudder will not deflect all of the prop wash striking it.
• Increase the amount of rudder deflection. You've done that. 45 degrees is about the maximum for effectiveness at slow speeds.
• Increase the volume of the prop wash striking the rudder by (a) increasing the blade area (larger prop, or more blades), or (b) increasing the RPM of the prop, or (c) decreasing the pitch of the prop, which moves more water per revolution, or (d) increasing the rudder area, or (e) some combination of the above.

Good luck!

Rob

[old shrimper]

 OK I think I have it SORTED NOW
 the biggest problem was I didn’t realize that ch 2 was the throttle ch     ( never had RC before )  now I can have the EPA setting in forward at 25% with full trigger and the motor just turns at about 100 rpm up the setting to 50% and it is about half speed  in rev setting at 70% and it gets rid of the auto cut out , so from slow to fast is nice and smooth (wow there's a lot of settings on the controller to figure out ) with the setting under 25% in rev it does hunt a bit but the motor is only doing about 50 rpm forward is fine down to as slow as you want
 
 I was all so able to up the EPA  on ch 1( Steering  )  to 120% and that gave me about 60 deg P/S so now I’m going to put the 60 mm x 4B back on as I can reg the RPM to what ever I like   
 

[grasshopper]

Excellent news......as always with we blokes, if all else fails RTFM!


In return for our advice how about some on water video of you in control?

[old shrimper]

har har bit to do yet as i have to ballast it properly  just using some lead ingots at the moment  1.8 kg in the bow and the same in the stern and the lead acid batt in the middle so about 5 . 5 kg all up giong to get some lead sheet about 6 mm thick and shape up the bilges for a try


and i wouldn't know how to down load the video after i had made it but ill work on it
i still have a concern that something is not wright with the rudder , or power


i have plenty of throw on the rudder now maybe to much ?


what happens is when i go to move away from  a stationery position even with it just ticking over  IT goes straight till it gathers way then it starts to turn
[size=78%]not like a real boat [/size]
[size=78%] i have  [/size]owned[size=78%] 8 trawlers  from 36 ft to 60 ft over  the time of my 52 years at sea and have driven another 6 or so for other owners in the early days, so i  know how it SHOULD handle [/size]
[size=78%]its like it has to much thrust even at low speed and moves a head before it will kick the [/size]stern[size=78%] away from the wall (dock ) the [/size]Becker[size=78%] rudder is [/size]looking[size=78%] as it may be the answer i was reading a report [/size]
[size=78%]a capt was giving about them on real ships [/size]pretty[size=78%] [/size]amassing[size=78%] but [/size]don't[size=78%] give it to  much at speed or you are in trouble [/size]
[size=78%]he recons 2 deg of rudder at 20 knots was enough to put a 10 deg list on 100,000  ton cruise ship but it handled very at low speed [/size]
[size=78%]cheers thanks for the guys [/size]

dont know whats going with all the sizeing stuff ???

[inertia]

Shrimper
Are you inserting square/curly brackets or any other punctuation marks into your text? If you just stick to commas and full stops maybe the unwanted size formatting will disappear and your posts will be easier to read.
DM

[old shrimper]

just some in brackets here and there ?

[inertia]

just some in brackets here and there ?

That'll be it then. Your browser is looking to "translate" them into functions such as size, colour and style of font. Leave them out and it will look much better (or use a different browser).
DM

[Tug-Kenny RIP]

We can modify and correct it at our end if you want.