Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: Help Please  (Read 2742 times)

Stavros

  • Guest
Help Please
« on: May 23, 2016, 10:41:35 PM »

Right then I bought this hull a while ago and asked for suggestions on what to build out of this hull.I finally decided one night whilst watching the Liverpool Pilot boats going out of Amlwch to build one.
I want to go Brushless and was thinking what Motor/esc combination to install in it.Batterey wise it will be running 12v Minh 4300 stick packs and NOT lipo's...Prop will be around 50mm 4 bladed

What Kva should I be looking at






Length is 32 in Beam 10ins

Thanks in advance......will more than likely buy my motors off component shop ...


Dave
Logged

imsinking

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 532
  • Location: Merseyside
Re: Help Please
« Reply #1 on: May 23, 2016, 11:27:27 PM »

Going to need lots of torque to drive a 50mm prop , so a slow running OUTRUNNER ?
 Kv is RPM per VOLT so around the 1000 or so in Kv is going to give ,at 12v, 12000 rpm at full power , a battery sapping effort if the prop's wrong , too coarse a pitch or too many blades , I'm new to Brushless so I'm probably waffling . . . .
Outrunners are hard to cool properly, inrunners can be fitted with a water cooled jacket and a water cooled ESC is available also (component shop) oh & you'll need a programming card for the ESC .
See my 'Fantasy Huntress build ' in the drydock topic to see how I got there . . .
http://www.modelboatmayhem.co.uk/forum/index.php/topic,51679.0.html
I know you like BIG motors ,but you'll be surprised how small  an efficient Brushless can be , it's a whole new ballgame . . .
Bill
Logged

sparkey

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,228
  • I think I am as mad as I think I am then I am mad
  • Location: wandsworth
Re: Help Please
« Reply #2 on: May 24, 2016, 07:14:06 AM »

I use these brushless outrunners in a lot of my boats,using 50-55 4 blade props on 14.4v (2x7.2v packs) and get good performance all round.   http://www.hobbyking.com/hobbyking/store/__19621__NTM_Prop_Drive_Series_42_48_650KV_1295W.html
Logged
My boats are all wood like my head fluctuat nec mergitur

imsinking

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 532
  • Location: Merseyside
Re: Help Please
« Reply #3 on: May 24, 2016, 11:30:28 PM »

Query about the hull , With the 'droop' snoot bow I was thinking it was a British Power Boat's WHALEBACK MTB , but I dont think they had a keel , so I'm wrong most likely.  :embarrassed:
Bill
Logged

Stavros

  • Guest
Re: Help Please
« Reply #4 on: May 24, 2016, 11:41:27 PM »

Honestly don know what the hull was intended to be,I did ask a few mnths back what everyone thought it was but no one could come up with a logical ans......might have been intended as a trawler of some sorts ??The keel was a lot longer than it is now,but I shortened it

Dave
Logged

sigfortunata

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 58
  • Model Boat Mayhem is Great!
  • Location: Staffordshire
Re: Help Please
« Reply #5 on: July 01, 2016, 08:03:52 PM »

Hmmm will watch this post with interest. I'm shortly going to build Lesro Pilot Boat of the same size 34" long by 10.5"wide and wondering what would be the best motor set up.
Logged

Tugtower

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 97
  • Owner of The RCMB Forum
  • Location: Workshop. S.Wales.UK
    • RCMB Forum
Re: Help Please
« Reply #6 on: July 02, 2016, 12:39:57 AM »

Thats a big boat for a brushless motor to be powered with only a NHMI battery.

I do think you may struggle to get anything decent speed wise out of her with a 50mm prop on a brushless setup, reason i say this is simply most NHMI battery's can only discharge at the 30 amp level, ( as there designed for rc cars)

There are others that can discharge higher but with added cost making lipos more cost effective.

A brush less in runner would give you plenty or rpm but for the size motor your looking at you'll need over 120 amp esc probably a 200 amp ( this is NOT a cheap option) if i'm honest and a battery that can supply the amps which is not your current choice.

A brush less out runner would be a better choice try overlander thumper motors (personal recommendation all my brushless boats use them) they have some 1400KV out runners which run off 30 amp escs meaning your battery could just about cope but will spin a 50mm prop effectively but i expect will lack any huge speeds.

that said the cut out in the stern looks for a jet drive? If that's
the case the out runner might just do the job providing your using a jet system.

If your going normal prop route then perhaps go for a brushed motor, maybe a tornado 850 or 900 with a electrolise 40 amp esc, which will run better for the boats size and no battery worries.

Unless your prepared to go to a 3 or 4s lipo a brushless setup in that boat will get you cruising but i think you'll be disappointed with its performance.


Check out this post for a suggestion i made on a similar sized boat , (it was twin prop so take that into account)


To which the final outcome used was my recommended setup which the guy was very happy with.


http://www.modelboatmayhem.co.uk/forum/index.php/topic,51503.0.html


Quote
I would like to give you a special thanks for your detailed help that enabled me to fit the boat out.  I got exactly what I wanted plus some.  I will now or when funds and her indoors allows, fit out my big huntsman with similar setup.
Regards Glyn



I'm sure Glyn wont mind me posting that from my mail box he sent.

Glyn Roberts

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 140
  • Creativity is contagious, pass it on.
  • Location: Norwich UK
Re: Help Please
« Reply #7 on: July 02, 2016, 03:35:52 PM »

Your welcome tugtower but I better mention that my boat was 50 inches in length so maybe the smaller of the motors you mentioned would be a safer bet in this case.

Regards Glyn
Logged

Tugtower

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 97
  • Owner of The RCMB Forum
  • Location: Workshop. S.Wales.UK
    • RCMB Forum
Re: Help Please
« Reply #8 on: July 02, 2016, 04:11:41 PM »

Could be right there Glyn, its hard to see the actual size of the boat compared to a toddler so i used best guess ( between 36 and 40 inches)
However the motor suggestions would still be fine, if the model is over powered ( which i do think is unlikely since GRP hulls tend to be heavier then Wooden ones) then its a simple case of not using full throttle, although i expect single a 1400KV compared to your duel motor setup will be enough.

That said a brush less motor would be better run from a lipo then a NHMI battery in any case as those size motors can take a range of between 2 and 4 s lipos which in turn will control the no load RPM.

2s Lipo is 7.4 v  running a 1400kv motor is  1400x7.4   = 10,360 RPM < this is as close as u can get with a NHMI
3s lipo is 11.1v  running a 1400kv motor is  1400x11.1 = 15,540 RPM
4s lipo is 14.8v  running a 1400kv motor is  1400x14.8 = 20,720 RPM

4s would be over powered but 3s would be a perfect power supply for a 1400kv motor giving you a decent turn of speed .

Stavros

  • Guest
Re: Help Please
« Reply #9 on: July 02, 2016, 09:58:14 PM »

Tugtower  the cut out in the stern of the hull was never intended for a jet drive it was what I had to do to remove some of the keel that was running fill length of the hull....motor etc still up in the air at the mo

Dave
Logged

Tugtower

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 97
  • Owner of The RCMB Forum
  • Location: Workshop. S.Wales.UK
    • RCMB Forum
Re: Help Please
« Reply #10 on: July 02, 2016, 11:28:29 PM »

Definitely look at the 1400kv-1500kv brushless out runners

http://www.overlander.co.uk/motors/brushless-motors/tornado-thumper-v3-3536-05-1500kv-brushless-outrunner-rc-motor-latest-model.html

tech spec is as follows

Brushless Outrunner RC Motor - Tornado Thumper V3 3536/05 1500KV - NEW FOR 2015!

• 408 watt motor• 6-12 NiMh cells
• 2-4 LiPo cells• Prop size from 8x4 to 10x6 (larger prop with less cells)
• Shaft Diameter 4mm• Motor weight 98gm (excluding accessory kit)
• 3.5mm gold connectors
• Speed Controller Recommended 30A ESC

I only use these brushless motors for my ALL my brushless boats ( I'll only recommend products i've used), i have found they are of superb quality (British made) although a little more expensive then ones from hobbyking  they have stood the test of time in reliability along with the fact on smaller boats the use of NHMI battery's is also handy.  Again a cheaper water cooled 30 amp esc is needed keeping the bank balance in check.

I've included a couple of photos of the 1500 KV version i'm currently using in a build which is a 36" wooden and GRP reinforced boat  ( shes quite heavy now)running on an X45 prop on  S3 for 16,000RPM.

The last photo is of an 1100KV in a 'vintage type' Fast electric boat with an 32mm hydro prop outrigger ( its actually the Dumas Skee Vee 10) which runs a 30 amp esc on a 3s lipo.

The advantages of using an outrunner is you can do away with water cooling the motor there is no need whatso ever... you can also get away with not cooling the ESC ( this is based on using up to 12amp esc's in a boat )  however i do not recommend that as most esc are cooled via air flowing over ( since out runners are mainly used in quad copters, but again very small up to 12 amp escs no problem) you can buy water cooled escs easily enough, which i do recommend buying and using in the correct way to avoid the nasty blown esc's when they over heat. in confined conditions,


Pages: [1]   Go Up