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Author Topic: is my boat to heavy for motors ?  (Read 10867 times)

Colin Bishop

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Re: is my boat to heavy for motors ?
« Reply #25 on: May 13, 2011, 03:38:32 PM »

Quote
As a quick rule of thumb, divide the running amps of motor under load by the amp per hour of the battery.     

Not struictly applicable to lead acid cells as they don't like being discharged below 50% of their nominal capacity. Nor do they like being fast charged either if you want a useful life out of them.

Colin
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Pete25

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Re: is my boat to heavy for motors ?
« Reply #26 on: May 13, 2011, 03:53:12 PM »

it states on the website i got the battery from this

The maximum charge current is 25% of the battery capacity (e.g. 2Ah battery = 0.5A maximum charge current).
SLA batteries should be charged regularly to ensure that they do not deeply discharge.
Battery Technology:   Sealed Lead Acid (Rechargeable)
Capacity Range:   4000.0mAh - 4600.0mAh
Voltage:   12.00V

the battery i want to charge is    
Ultramax NP4.5-12, 12V 4.5Ah Lead-Acid Battery

my charger i want to use says on it
12v lead acid batteries only
minimum capacity .20 Ah
input 240v ~50Hz 55W
output 12v 2.7A DC 4Amps


@Bluebird  my hull will be strengthened just waiting on the materiel :)
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John W E

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Re: is my boat to heavy for motors ?
« Reply #27 on: May 13, 2011, 04:43:34 PM »

hi here Pete

The battery charger you are using will do the job;

I have included a couple of pics of the Destroyer - HMS Daring - she is just a tad short of 5' - she is 1:72 scale.

This is the running gear set up in her - she has 2 x Graupner 500 motors - rated at 7.2 volts and running at 17,600 rpm.  She draws 9 amps at the most efficient.

There are 2 x 30mm props on the model and with these props the motors draw roughly about 4-5 amps under load.   The speed controllers are ACTion P80s and they are rated at 20 amps each - a bit of overkill - but - hey it does the job.

Also there is a mixer involved in it which mixes the speed of the props and motors with the movement of the rudders.    I run the model on 2 x NiCad packs of 7.2 volts  - 3300 m/a .   This gives me ample time on the water.

aye
john

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Pete25

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Re: is my boat to heavy for motors ?
« Reply #28 on: May 13, 2011, 05:50:56 PM »

thankyou :) loving the pics ! i like how the motors are fixed in. i might use that design in mine if its cool to pinch that design ? :P cheaper than the steel brackets thats for sure .

well iv just ordered 2 12V 4.5Ah Lead-Acid Batteries not sure if you receive them fully charged or not but i will try my charger when they need charging on it :)

at looking at your pics i can see now why everyone is saying i have too much power  {-) but just because iv got all that power dont mean i have to use it all aa cheers everyone for your help :)
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Pete25

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Re: is my boat to heavy for motors ?
« Reply #29 on: May 13, 2011, 07:47:57 PM »

thankyou :) loving the pics ! i like how the motors are fixed in. i might use that design in mine if its cool to pinch that design ? :P cheaper than the steel brackets thats for sure .

well iv just ordered 2 12V 4.5Ah Lead-Acid Batteries not sure if you receive them fully charged or not but i will try my charger when they need charging on it :)

at looking at your pics i can see now why everyone is saying i have too much power  {-) but just because iv got all that power dont mean i have to use it all aa cheers everyone for your help :)

will i need to use 3 speed controllers then as i have 3 motors for propulsion ? i will be using a servo for a rudder
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Stavros

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Re: is my boat to heavy for motors ?
« Reply #30 on: May 13, 2011, 08:52:40 PM »

The batts will have a partial charge in them so charging will be a advisable


stav
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wartsilaone

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Re: is my boat to heavy for motors ?
« Reply #31 on: May 14, 2011, 01:20:38 AM »

Hello again Pete. Yes you will need 3 speed controllers and you would need to use 3 separate channels on your transmitter. Once you go past two props it gets hard to control everything at the same time. With a three prop boat I would suggest a mixer which reduces the channels needed and will help the boat turn by slowing down or even reversing the prop on the inside of turn. A mixer was suggested for my boat but I turned it down as it isn't really necessary, now however I am thinking of getting one so I can free up some channels to use for something els and I won't need two pairs of hands. :}

Yours Ali.    
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Pete25

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Re: is my boat to heavy for motors ?
« Reply #32 on: May 14, 2011, 02:05:59 AM »

Hello again Pete. Yes you will need 3 speed controllers and you would need to use 3 separate channels on your transmitter. Once you go past two props it gets hard to control everything at the same time. With a three prop boat I would suggest a mixer which reduces the channels needed and will help the boat turn by slowing down or even reversing the prop on the inside of turn. A mixer was suggested for my boat but I turned it down as it isn't really necessary, now however I am thinking of getting one so I can free up some channels to use for something els and I won't need two pairs of hands. :}

Yours Ali.    

that sounds complicated to do is there a way i can use one speed controller to begin with then later use a mixer and 3 speed controllers ? the pond i will be using this boat in is my local boating lake which is very big..
cant i just get say like one 60amp speed controller and rig all 3 motors up to the positive and negative (daisy chain the motors to the speed controller)

i need to try and keep cost's down iv spent a scary 100 at the minute and iv only got 3 motors.parts to make 3 drive shafts/parts for water cooling motors/3 50mm propellers/ 12v acid battery and nearly finished hull (needs waterproofing)

if there is no way out and i need to have 3 speed controllers what amp controllers do i need and how do i wire them up ? {-) i cant find any instructions on Google :((
and when i use 3 speed controllers how do i use them on my reciver . thumb stick up and down to control all 3 speed controllers? sorry if this is a nube silly question
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wartsilaone

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Re: is my boat to heavy for motors ?
« Reply #33 on: May 14, 2011, 02:27:44 AM »

Don't rush into anything. It is best to take your time, get the right stuff when you can afford it. You can connect all the motors together but you may find that your boat doesn't want to turn. Plus a big speed controller like a 60 amp one is very expensive and can be a bit un-sensitive.
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wartsilaone

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Re: is my boat to heavy for motors ?
« Reply #34 on: May 14, 2011, 02:37:01 AM »

It may sound a bit preachy but it took me two years and about 900 to build my boat. I may have had some beginners luck with some things but I never rushed and tried to get the right stuff first time. It will cost you even more if you have to replace parts.
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Pete25

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Re: is my boat to heavy for motors ?
« Reply #35 on: May 14, 2011, 03:08:26 AM »

It may sound a bit preachy but it took me two years and about 900 to build my boat. I may have had some beginners luck with some things but I never rushed and tried to get the right stuff first time. It will cost you even more if you have to replace parts.

you have a point there.. ok ill go the 3 speed controllers then :) then its done properly . iv just found a video on how to wire them up to one channel on the receiver which is what i want for the minute .

im unsure which esc's i need would 20amp esc be ok with my 12v Johnson 600 motors Off load Current: 1.57A

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wartsilaone

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Re: is my boat to heavy for motors ?
« Reply #36 on: May 14, 2011, 03:13:33 AM »

I would probably go with 25s or even 30s. 
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wartsilaone

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Re: is my boat to heavy for motors ?
« Reply #37 on: May 14, 2011, 03:18:24 AM »

You will be amazed how much difference it makes when your motors are trying to turn the props in the water.   
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derekwarner

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Re: is my boat to heavy for motors ?
« Reply #38 on: May 14, 2011, 03:19:55 AM »

Pete25....I understand your $ costs constraints  <:(....but it appears you did not plan & do your $ sums prior to the build  >>:-(...hence your current $$$$$ quandry

I also understand & agree with the comments from wartsilaone....so is there a compromise?  ;D

1. you could consider running the two outboard motors only...the middle motor could be installed with the prop...but not connected electrically
2. you could consider fitting oversize rudders [two or three] depending on the vessel original design

From here you could consider two ESC + use two channels on your TX...which wil get you into the water & running....sometime down the track when $ funds were available an ACTion mixer could be considered between the two outboard motors only

Not sure on the best search method here, but I have read about 3 engined model vessels [PT style vessels?] where the center engine is only used for high speed work & running without any form of ESC....this facility could be simply switched by servo to micro switch & controlled by another TX single switch function.....

A few things to consider  :-)) .....clearly all is not lost    :-X ....Derek
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Derek Warner

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wartsilaone

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Re: is my boat to heavy for motors ?
« Reply #39 on: May 14, 2011, 03:28:01 AM »

I agree with Derek. You could have the middle prop running free for now as the other two motors should be enough to push the boat along. Twin rudders would definitely help.
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Netleyned

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Re: is my boat to heavy for motors ?
« Reply #40 on: May 14, 2011, 07:13:06 AM »

Pete, Is this the Boating Lake?
If so, Come down and see us on
Wednesday or Sunday Afternoons
or Tues/Thurs evenings.
Plenty of experts and not so experts
willing to help.

Ned

(my much modified Victoria in a nice breeze)
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John W E

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Re: is my boat to heavy for motors ?
« Reply #41 on: May 14, 2011, 09:42:20 AM »

hi ya Pete25

I wonder if it would be adviseable for you to temporary 'shelve' shis project.  You may wish to take on a project such as one of Glynn Guest's builds which you will find a lot of his plans have a lot of articles which appear in Model Boats magazine.   Doing it this way - everything you require is set outfor you - i.e. motor/speed controller/props & soforth - a simple plan of this sort is a bit like learning to drive - although you dont like the car you are learning to drive in - it may not be your choice it teaches you the basics.

So once you have learned the basics = you can go back to your choice of model with a lot more confidence and understanding of this modelling field.

aye
john
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Shipmate60

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Re: is my boat to heavy for motors ?
« Reply #42 on: May 14, 2011, 11:26:18 AM »

Pete,
It might be worth taking Bluebirds advice for a while to consider ALL the options which are:

All 3 motors on 1 Speed Controller.
This can be done very cheaply with an old fashioned mechanical car controller which will take horrendous current safely.
Or a large capacity Electronic Speed Controller.

Only power the 2 outboard motors.
Can be powered as above or with 2 Speed Controllers.
This has the advantage of only using 2 vertical sticks on your transmitter so easy to control.

As above but with the third motor switched by a high powered microswitch switched from another channel on your transmitter.
2 outboard motors powered by 1 ESC using 1 channel and the third using another ESC from another channel on transmitter.

Another option, but not a good one is to use an ESC on the centre motor and switch the outboard motors.

For me the best option but the most expensive is to use an ACTion P94 plus a condor ESC which will give you a mixing facility on the outer motors and throttle control on the centre motor.

I can only recommend you get the motors tested as SOME Johnsons pull high current on 12 volts but are fine on 6 volts.

Another consideration is the wiring from the battery to the ESC(s) as this will have to be able to take the full current of all 3 motors plus some reserve.

For 3 motors on 12 volts I do not think you have anywhere near the battery power so keep the model on the water for any length of time.

You really do need to have the motors tested to be able to tailor the Electronice to them.

Where abouts are you, it would help if you filled in your location.

The motors you have look to be quite high current motors with 1.57 Amps off load.
For 50mm props you wont need any more than about 5000 rpm so she will be grossly overpowered and looks like power hungry.

Bob
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wartsilaone

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Re: is my boat to heavy for motors ?
« Reply #43 on: May 14, 2011, 11:28:14 AM »

Hi pete. I know as a beginner you don't want to hear some of this and I don't doubt at all your intelligence and ability to make a great model. We are just trying to prevent you making the mistakes we have made and save you the countless pounds we have spent changing things. If you really feel you can do this project don't let anyone put you off. A friend of mine suggested I try something easier when I started my ship but that just strengthened my resolve to do it. Whatever you choose to do we will be here to help. There is no such thing as a silly question if you don't know the answer.

Yours Ali.


  
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Pete25

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Re: is my boat to heavy for motors ?
« Reply #44 on: May 14, 2011, 02:52:42 PM »

thanks again for everyone's help i really do appreciate it.. this is not my area of electronics . i build and modify pc's but my nolage stops at motors and speed controllers if you haven't guessed by now  {-)

i has seen mechanical speed controllers for round 15 but iv heard about arcing and reliability issues with then not to mention the heat. there so easy to set-up and i would probably go that route but the issues are putting me off.
not only that but i couldn't find a 12v model with hight amp capable.

does anyone no were i can get a old fashioned mechanical car controller from in the uk ? i could give it a go i suppose

i am defiantly going to use 2 rudders (large) for this boat im even considering bow thrusters as i have the tool and ability to make some of my own  :-)


@ netleyned

yes thats the boating lake in cleethorpes would it be ok if i pop down Sunday ? its bit late now to run down there. what time tomorrow would be good to turn up ?
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Shipmate60

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Re: is my boat to heavy for motors ?
« Reply #45 on: May 14, 2011, 08:13:51 PM »

Pete,
Here are some videos of my 10 foot Cruiser hull on the water with an ACTion mixer.
The hull and batteries are heavier than your proposed all up weight.
BUT she is running 50mm props (3) at less than half your proposed rpm.
As Bluebird has said she will fly.

http://media.photobucket.com/video/prinz%20eugen/shipmate600/Picture031.mp4?o=4

http://media.photobucket.com/video/prinz%20eugen/shipmate600/Picture030.mp4?o=5

http://media.photobucket.com/video/prinz%20eugen/shipmate600/Picture029.mp4?o=6

Bob
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RaaArtyGunner

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Re: is my boat to heavy for motors ?
« Reply #46 on: May 14, 2011, 09:49:42 PM »

Pete, Is this the Boating Lake?
If so, Come down and see us on
Wednesday or Sunday Afternoons
or Tues/Thurs evenings.
Plenty of experts and not so experts
willing to help.

Ned

(my much modified Victoria in a nice breeze)
Ned,
How did you achieve such a fantastic water display from the Fireboat, looks great
 :-)) :-)) :-)) %) %) %)
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Pete25

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Re: is my boat to heavy for motors ?
« Reply #47 on: May 14, 2011, 10:07:36 PM »

Pete,
Here are some videos of my 10 foot Cruiser hull on the water with an ACTion mixer.
The hull and batteries are heavier than your proposed all up weight.
BUT she is running 50mm props (3) at less than half your proposed rpm.
As Bluebird has said she will fly.

http://media.photobucket.com/video/prinz%20eugen/shipmate600/Picture031.mp4?o=4

http://media.photobucket.com/video/prinz%20eugen/shipmate600/Picture030.mp4?o=5

http://media.photobucket.com/video/prinz%20eugen/shipmate600/Picture029.mp4?o=6

Bob

wow that cuts though the water so nicely  and is really fast ! do you have any pictures of the motor section ? that is a nice hull design did you scratch build that ? i don't think i could ever build a hull that nice  {-)
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Shipmate60

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Re: is my boat to heavy for motors ?
« Reply #48 on: May 14, 2011, 10:26:35 PM »

She is a plank on frame hull built well over 20 yrs ago (not by me)

The pic shows the initial installation before the P94 was produced.
She was 1 of the first to have it fitted and tested.

Bob
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