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Author Topic: Dumas Mr Darby - My build  (Read 26875 times)

oldflyer2

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Dumas Mr Darby - My build
« on: August 01, 2015, 06:57:59 PM »

Hello All

I have just received an untouched Dumas Mr Darby hull that has never been started.

I have the plans, and a multitude of reference pics found on the net. I do not intend to do an actual Mr D, but something of my own design.

I am wondering if anyone has a set of running gear they don't want, either the Dumas one or the Harbour Models one. I could be interested if the price is right.

Also, I would like to do the Kort knozzle version so if anyone has a pair of them for Mr D laying around, I could be interested in that as well.

I am planning on doing the water ballast treatment as I couldn't lift the fully ballasted one anymore.

Cheers

Tom
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oldflyer2

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Re: New To Me Mr Darby Hull
« Reply #1 on: August 08, 2015, 11:28:38 AM »

All sorted. I am going with the open wheels so don't need korts, and the props are on their way from the usa.

Tom
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Martin [Admin]

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Re: New To Me Mr Darby Hull
« Reply #2 on: August 08, 2015, 12:43:41 PM »


What motors will you be using Tom?      :-) 

Some inspiration photos...












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Mark T

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Re: New To Me Mr Darby Hull
« Reply #3 on: August 08, 2015, 06:18:53 PM »

Now that's a nice looking tug - good luck with the build Tom

oldflyer2

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Re: New To Me Mr Darby Hull
« Reply #4 on: August 09, 2015, 11:58:32 AM »

Martin, I haven't decided on the motors just yet. I would like a pair of Pittman 3700's but they are scarce these days. Harbor does a pair of 850's with belt drive as a set of direct drive one's.

I am trying to figure out some timing belt and pulley sizes and then I also might make my own belt drive. There are a couple of robotics suppliers near me where I can get what I need.

Do you have any idea where one can get the knitted brow in the pic or the pattern for tying one up? I really like them.

Mark, I have lusted over one of these tugs for 20 years and I am going to enjoy building her.

Cheers

Tom
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oldflyer2

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Re: New To Me Mr Darby Hull
« Reply #5 on: August 09, 2015, 07:30:43 PM »

I am putting in a stern roller similar to the current day Atlantic Salvor (ex Mr Darby).

This is what will be cut out of the stern at this point ...



That may change as I am making the bits for the roller before I cut the hull away. There does come a time when that needs to be cut though. <:(

I also reinforced the bottom of the hull to make it a bit stronger. It will get more when the battery box goes in.


Tom
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Capt Podge

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Re: New To Me Mr Darby Hull
« Reply #6 on: August 09, 2015, 07:38:19 PM »

Keep the photos coming as you progress Tom - she looks like a mighty beast - good luck with your build :-))
 
Regards,
 
Ray.
 
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oldflyer2

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Re: Dumas Mr Darby - My build
« Reply #7 on: August 09, 2015, 08:49:59 PM »

Ray, she will be around 65lbs when up to the water line. I am going to try water ballasting as I can't lift that much. I am aiming at a 20 to 25 lb finished hull. Err, that doesn't include the celebratory bottle of amber liquid when done.

Tom
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nemesis

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Re: Dumas Mr Darby - My build
« Reply #8 on: August 09, 2015, 10:17:03 PM »

Hi, With water weighing 10lb a gallon plus the size of a gallon can, you will not have the space to get all your ballast in. You will have to use Lead, more weight less volume plus you will still have your boyancy. A fellow club member has this model and it takes quite a lot of weight to take it down to the marks. water ballast,in my opinion, is not the way to go. nemesis
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Stavros

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Re: Dumas Mr Darby - My build
« Reply #9 on: August 09, 2015, 11:36:44 PM »

Personally I wouldn't bother with a MFA850...ok everyone knows I hate them with a vengence for the simple reason of how much amps they can draw...All you need on this one is a Brushless motor with a KVA of 700 ish and that will give you around 8500 which in fact should be right for it flat out with plenty of reserve power....oh and go direct drive nad don't bother with a gearbox you wont need it

Dave
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oldflyer2

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Re: Dumas Mr Darby - My build
« Reply #10 on: August 10, 2015, 12:48:28 AM »

I didn't mention that the 35ah battery weighs in at around 26lbs according to the specs, so I should only be needing another 10 or 15lbs or so. Anyway, it is all speculation at this point and I won't worry much about it until much later in the build.

In my earlier post, I meant to say mfa800 motors. They are being used direct drive in another Darby with good results. This decision will come a bit later as well. I am visiting a friend next week that may have the answer to the motor question.

Version one of the roll didn't wuite work as advertised so I will have another go at that in the morning.

Tom
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oldflyer2

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Re: Dumas Mr Darby - My build
« Reply #11 on: August 10, 2015, 12:32:22 PM »

Dave, is this the sort of thing you are talking about?    http://www.hobbyking.com/hobbyking/store/__9449__Turnigy_540L_V_Spec_Inrunner_w_Impeller_810kv.html

I know absolutely nothing about this new technology. Will these run on a car battery? I refuse to have lipos in the house.

Tom
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Stavros

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Re: Dumas Mr Darby - My build
« Reply #12 on: August 10, 2015, 12:47:30 PM »

http://www.hobbyking.com/hobbyking/store/__12922__Turnigy_D2836_11_750KV_Brushless_Outrunner_Motor.html

That's what I would personally use yes you will need some suitable esc's for them and YES they CAN be used with a car batt....I am exactly the same as yourself with Lipo batts cant stand them......


Dave
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oldflyer2

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Re: Dumas Mr Darby - My build
« Reply #13 on: August 10, 2015, 01:32:43 PM »

Thanks for that link Dave. The one thing I am going to splurge on is a P94 from action. That includes two 20a esc's that I think the motors you linked to would work well with.

The only thing I see is they call for 7.4 to 11.1 v input. Would they take 6 or 12v?

Tom
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oldflyer2

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Re: Dumas Mr Darby - My build
« Reply #14 on: August 10, 2015, 06:29:35 PM »

I have ordered 2 of those motors to check out.

Tom
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Stavros

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Re: Dumas Mr Darby - My build
« Reply #15 on: August 10, 2015, 08:18:40 PM »

Hang on a mo the motors that I linked you are Brushless motors and the P94 will NOT work with them, it is only for brushed motors.
You will need a pair of these esc's to run those motors and get a programming card to set the esc up and YES you can run them off a lead acid batt


Dave
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oldflyer2

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Re: Dumas Mr Darby - My build
« Reply #16 on: August 10, 2015, 10:48:49 PM »

Hi Dave

You didn't include a link to the esc's.

Not to worry, the motors will work in two other boats I have and are cheap as chips compared to what is available here.

What BRUSHED would you or anyone else recommend with the Action controller?

Tom
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oldflyer2

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Re: Dumas Mr Darby - My build
« Reply #17 on: August 10, 2015, 10:59:06 PM »

OK ... just a question ... does a tug boat, going at scale speed, have enough speed through the water to make a scoop cooling system work? The esc's and the motors may need to be coioled under heavy load. Just thinking ahead as now is the time to put the scoops in.

Tom
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Stavros

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Re: Dumas Mr Darby - My build
« Reply #18 on: August 10, 2015, 11:07:08 PM »

I wouldn't have thought they would get warm enough to need water cooling......if they will need cooling all you do is to put a scoop in and use  12v pump to work it.. easy to rig up....Y lead to an esc off the main motor lead to the receiver


Dave
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oldflyer2

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Re: Dumas Mr Darby - My build
« Reply #19 on: August 11, 2015, 12:24:42 PM »

I have been looking for esc's for the brushless motors above. I found these ...  http://www.hobbyking.com/hobbyking/store/__11616__Turnigy_AE_25A_Brushless_ESC.html   They seem to have the right specs except for the input battery type. They call for lipo's or nimh ... will they work with lead acid gel type battery?

Can someone point me to a tutorial that explains all this new battery/brushless/esc technology or a chart that tells me what goes with what? I am getting a very serious headache with this stuff.

Tom
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oldflyer2

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Re: Dumas Mr Darby - My build
« Reply #20 on: August 11, 2015, 01:42:45 PM »

Another silly question ... will esc provide reverse?
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Martin [Admin]

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Re: Dumas Mr Darby - My build
« Reply #21 on: August 11, 2015, 02:03:39 PM »


You could always try the Action P82 micro MOTOR MIXER - which should work with any ESC motor combination


Connects to the Throttle and Steering outputs from the Rx and automatically slows down the motor on the inside of a turn when a rudder command is given. P82 feeds the power for the motors directly through to the ESCs from the receiver connections i.e. the whole model requires only one battery pack to power everything. Suits P68A and P52 ESCs. It has an ABS case - 34mm x 24.5mm x 16mm, with onboard plug-in connectors for two outer motors and the steering servo.

http://www.action-electronics.co.uk/mixers.php
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Martin [Admin]

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Re: Dumas Mr Darby - My build
« Reply #22 on: August 11, 2015, 02:09:21 PM »


It doesn't mention Reverse in the specs for those controllers!
Also, look at Car ESC as there do reverse better than boat ESC's.

Brushless Motors:
   http://www.modelboatmayhem.co.uk/forum/index.php/topic,13538.msg130068.html#msg130068

I have been looking for esc's for the brushless motors above. I found these ...  http://www.hobbyking.com/hobbyking/store/__11616__Turnigy_AE_25A_Brushless_ESC.html   They seem to have the right specs except for the input battery type. They call for lipo's or nimh ... will they work with lead acid gel type battery?

Can someone point me to a tutorial that explains all this new battery/brushless/esc technology or a chart that tells me what goes with what? I am getting a very serious headache with this stuff.

Tom
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inertia

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Re: Dumas Mr Darby - My build
« Reply #23 on: August 11, 2015, 02:12:21 PM »

Tom
Harbor Models offer two alternative hardware sets; both having belt-driven MFA 800 motors. The ACTion P94 will be fine with either of these but NOT with the 850 motors which, as Stavros says, are prone to draw much higher currents than claimed - although with belt-drives the current will be less than with direct drive.

The brushless speed controller you have linked to doesn't have reverse - not many do. There are marine ESCs with reverse; these guys do a couple and there are loads more on the Internet if you include the word "marine" in your search criteria. http://www.componentshop.co.uk/brushless/speed-controllers-esc/boats If the technical blub doesn't specifically mention the word "reverse" then you can assume that it doesn't have it. A number of folk use car speed controllers and program out the brake function. These are generally fan-cooled. As regards water-cooling, tugs will use large slow-revving motors so are unlikely to need any cooling.

SLA batteries are not capable of supplying large currents unless they're the heavy-duty and expensive "leisure" type. LiPos are popular because they're what the aeromodellers use and can supply very large currents. NiMH packs are a happy half-way alternative for those who believe all of the scary nonsense put around about LiPo batteries. Treat them properly and they're perfectly safe; act carelessly with them and they can bite - but so can a Stanley knife...............  O0

Just seen Martin's post - the P40E is a better unit because it has four different modes of operation whereas P82 has only one.

Dave M
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oldflyer2

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Re: Dumas Mr Darby - My build
« Reply #24 on: August 11, 2015, 04:38:13 PM »

I do have a Viper marine esc on the way for another boat. They are supposed to have excellent low speed control. I will see how it works out and then, I may get a pair of them along with a pair of torpedo 800's and a P40.

Thank You for all the information ... the fog is clearing a bit more now and I have a better idea of what to look for.

And now, I best get back to work as all this is errelivent if I don't get the boat built. It is almost time to cut that large bit of the stern out.

Tom
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