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[Glyn Roberts]

Hi folks

http://www.cornwallmodelboats.co.uk/acatalog/dumas-1211.html

I have built the Dumas Dauntless  (see above)

I am commited to the running gear and props That are 3/16 dog drive and 2inch 3 blade props.  The boat is driven via 2 motors and I intend to go for brushless as the original boat could reach 50 knots so I would like scale speed and then some.  My knowlege of Brushless motors is very limited and so I need to know what motors and speed controlers would suit the running gear and props. 

Thanks and regards Glyn

[inertia]

This motor is comparable in most respects with the Astro 25 Cobalt brushed motor on 12v (3S LiPo). It is also a little cheaper than $385!
http://www.componentshop.co.uk/lc3542-5t-1080kv-leopard-outrunner-brushless-motor.html
That being the case then a pair of them should make the Dauntless fly. I presume that the Astro 25 is OK by Dumas for the props they supply - it certain has that "right" feel about it.
Here's the Astro's specs (if the board is big enough for this URL) https://www.google.co.uk/search?q=astro+flite+25+motor&tbm=isch&tbo=u&source=univ&sa=X&ei=uZ-FVdGmE4aw7Ab1_4PYDg&ved=0CDkQsAQ&biw=1280&bih=875#imgrc=Nhe5W0n5C2zM2M%253A%3BYnxRPXMExCaFYM%3Bhttp%253A%252F%252Fi733.photobucket.com%252Falbums%252Fww338%252Fguapoman2000%252FPT311%252FAstroFlight625Cobalt25Motor.jpg%3Bhttp%253A%252F%252Fwww.rcgroups.com%252Fforums%252Fshowthread.php%253Ft%253D1714096%2526page%253D2%3B637%3B621

[Glyn Roberts]

Dumas recomend that 1. 1/2 inch 3 blade props ok for the Astra 25.  I have been looking at the Turnigy aerodrive sk3  4045- 500kv  or  sk3 5045-500kv motors
2 mayhemers have suggested them in the last couple weeks. 

The LC3542-5T 1080KV Leopard  looks good and the price is right if they make it fly, thats what I want, this boat does not look good untill it is flying.   Not got the hull of the Huntsman that looks good on slow plane.

Would that work ok with Ni-MH power?

Regards Glyn
 

[Tugtower]

i'll refer you to this post i replied to on brushless motors is covers the basics..


http://www.modelboatmayhem.co.uk/forum/index.php/topic,51455.msg526802.html#msg526802


That's quite a large boat, so the linked thread applies, the thread covers Outrunners more then inrunner type motors, being a LARGE boat with 50MM props i would suggest something in the 1500 -2200kv range outrunner, you could go for inrunners but you would have to look at cooling 2 escs and 2 motors , also outrunners are generally cheaper not only for the motor but ESC too.


 BUT to go fast i would recommend swapping out those props to an X45, 2 blade prop (racing props), if you can get them in a 3/16 (check Cornwall model boats dog drive props)


Just be aware that when you run brushless you are running 2 ESCs together ( 2 motors 2 escs needed for brushless systems), you can link both ESC through a Y harness, to the receiver ( so both motors work on the same channel)


but make e Sure one of the ESC's BEC wire is Disconnected.

hope it helps

[Glyn Roberts]

Thanks Tugtower,

Some info that I was not aware of thanks,  you have given me 2 possible ways to go so will have to do some thinking and some research.

Regards and thanks Glyn                    PS   Cornwall do not stock matching pair of counter rev. props.  45mm props have different pitch.

[Time Bandit]

I´d also use "racing prop" on the lake.
You can still replace them for better looking brass props if you display the model.
The dogdrives will make this pretty easy without the risk of loosing the props if you don´t assemble them correctly.
The Graupner K-Series generally works very well on boats like this, 45 mm diameter should do it very good.

For a large boat like this with your intended speed I´d use some large outrunners.
You didn´t mention your battery, this kinda makes it hard to find a good motor.

But calculating with the 45 mm racing props you´ll need around 12.000 rpm to reach 20 mph. And I´m guessing that much faster won´t be applicable to that kind of boat.

So let´s just guess you will use 4S Lipo batteries (I dont recommend less than 4S due to the amps this will draw at high speed, 5-6S should be even better)
--> 810kv * 1,1 (to get rpm without load) --> 900kv.

I´d use brushless outrunner with at least 250g weight for such a big boat.
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=39873
Something like this will do the job perfectly.
On 6S http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=22035

[Tugtower]

Thats pretty much what i said 


That said tho... 100 & 90 amp escs needed for both motors  not sure on your choice of motors to be honest and 6S lipo's ain't that cheap... not when you need 2 of em every 8 min run you get!


one motor £45 other 25.. so thats x2 regardless, cheapest (and closest amp rated esc) watercooled too [size=78%]http://www.hobbyking.com/hobbyking/store/__74073__Turnigy_Marine_120A_BEC_Waterproof_Speed_Controller_with_Water_Cooling.html[/size]


there still £40 each, so between £150-£200 just for the electrics not including batterys wait whats 6's ....


http://www.hobbyking.com/hobbyking/store/__24302__Turnigy_nano_tech_A_SPEC_5000mah_6S_65_130C_Lipo_Pack.html


5000 6s pack with the right C rating for the esc's £67 a pop ......


Sorry Time Bandit that setup is just not right. No ones gonna pay close to 300 'smackers' for an electrical setup like that unless there a professional racer.


i'ld go for something like this


http://www.hobbyking.com/hobbyking/store/__18233__Turnigy_D3548_4_1100KV_Brushless_Outrunner_Motor.html


Or the higher rated 1400 kv ( its the next one up from this, same esc) on 3s for 15,960 rpm


http://www.hobbyking.com/hobbyking/store/__67040__HobbyKing_50A_Boat_ESC_4A_UBEC.html


on 3s so 11.4V ish should give you 12,540 rpm at the prop, per motor on a X45 its also a more down to earth price!! £12 an esc £12 a motor, batterys well there still in the £30 zone for higher rated 3s' but thats half the cost of the 6's total £90 give or take a little.

[kinmel]

Don't forget to buy a programming card for the ESC.

This is the one for the HobbyKing Boat series.. http://www.hobbyking.com/hobbyking/store/__24570__HobbyKing_Boat_ESC_Programming_Card.html

[Glyn Roberts]

I thank everyone for their input,

I have found a matching pair of props under General Purpose props They are 42mm 2 blade and right and left handed.   The only racing props available in counter matching pairs are 60 and 70mm that I would guess are to big.

Would the 42mm props be ok      http://www.prop-shop.co.uk/products.php?cat=general-purpose

Regards Glyn

[Tugtower]

the props are fine.. however..

There are a lot of unknowns in your model, especially when you start adding electrics, and the prop tends to be the most important part to get you moving.. i always suggest attempting to prop your boat with plastic props first to see which ones works best before investing into brass ones, (plastic props are 99p-£3 a go.)

I've suggested X45 for yours based experience of owning boats in similar size so those 42mm ones may be fine.

Only problem is you need dog drive props, which is limited you on being able to test the boat, anyway you can swap out to a standard 4mm shaft with a nut on the end to lock the prop ? this would make a lot more props available to test before investing £25 in brass ones

you could fit the best electrical setup in the world.. but if the props are wrong then the boats just gonna be a bag of nails.

if not you could also try here for props, much larger range or racing props, a lot are subsurface but they have a nice section of 3 blade submerged racing props too.
http://www.prestwich.ndirect.co.uk/octurapropellers.htm

could you post a photos of your boat and some of the inside etc? that might help a little more in determine whats best suited, right now i'm running off guess work!

[Glyn Roberts]

Thanks tugtower for your help,

I found another set props (4518 Cleaver & R/C Hydro LH / 2 BLD Bronze - Default fitting is 3/16" dog drive)     

http://www.prop-shop.co.uk/products.php?cat=cleavers-rc-hydros&page=2     Don't know if they are suitable.        Will go and look at your link now.

Regards Glyn

[Tugtower]

aww thats nice and she looks light as pie   

go for something with the electrical setup I've suggested, (1400kv motos woul;d be best) and probably those 42mm counter rotating props and you should be flying, shes'll be fast but not so fast you cant control it.

This is what one of those 1500kv motors can do .. in a boat 800mm long. so you can imagine 2!

you'll have to mute the sound to drown out my mothers dorset tones.. trust me i gotta listen to that 

You may have to weight down the front of the boat, like we had to in the end to stop her bouncing.

https://youtu.be/2zrfe7dsBNo

[Glyn Roberts]

Wow she really goes, nice design to.     I'm having trouble chasing down the 1400kv motors, they all seem to be for heli's and they are so small.   could 2 of them really push this boat fast.    Would I have to use Lipo or could Ni-MH be ok.    Would this motor be ok (Turnigy Aerodrive SK3 - 3536-1400kv Brushless Outrunner Motor)   http://www.hobbyking.com/hobbyking/store/__18119__Turnigy_Aerodrive_SK3_3536_1400kv_Brushless_Outrunner_Motor.html

Regards Glyn

[Stavros]

Either or would be fine but make sure the NIMH are a high capacity
 
 
Dave

[Glyn Roberts]

Thanks Dave,

There is so much to learn, my wife can't believe that I have taken this on at my age.  Still I got her to join the local boat club.  She likes the tea

Regards Glyn
 

[Danny]

Glyn
The Propshop props are numbered with the first pair being the diameter in millimetres and the second pair indicating the pitch.
I.e. 4518 is 45 mm diam with a 1.8 times pitch.
The greater the pitch, the more the motor (or engine) is loaded.  If the motor can take the load, you would have VERY high speed (once you got the thing going), but if it can't you will get an extremely hot motor which will probably burn out.
The 4518 would be far too coarse for submerged drive and really only suitable for very high speed surface-piercing hydros where half the blade is out of the water!
Multi racers have very quick boats and only use 1.4 pitch (1.2 being normal pitch used on scale boats).
I would suggest you look at the 4514 size which is available in 3/16" dog drive left and right, then if its still not revving enough, go to 1.2 or 1.3 pitch (or reduce diameter).
Cheers
Danny
PS.  I hope the flexi shafts are wound in opposite directions.  If so double check they are each on their correct side.  If they are both wound in the same direction DON'T use contra-rotating props or one of them will splay open and break! 

[Tugtower]

That boat and another i'm building run of 1 of these.
http://www.overlander.co.uk/tornado-thumper-v2-3536-05-1500kv-brushless-outrunner-rc-motor-latest-model.html



Only needing a 30 amp esc and don't require lipos ( although my current project will ) just be sure to get high discharge rated nhmi's if you run those ( componant shop can supply 7.2 and 8.4v nhmi 50 amp discharge rated.)


Those motors are the same size as a 540 type motor just a bit shorter very efficient on a 5000 nhmi battery getting around 25 mins of run time ( you'll get the same but remember 2 motors, 2 escs and 2 batterys are needed for your setup, you can't use one battery for 2 esc's without going down the power distribution board route with higher rated lipos, like the multi rotors use)


I used the thumper and a 30 amp seaking marine esc, x45 prop on m4 JP's slimline stainless shaft running on 8.4v nhmi, the new one will be same but running on 11.1v lipo ( more rear stable boat with flat transom so i can go faster)


*** oh and b4 i forget when hooking up the esc's to the receiver..use a Y lead to run both off the same channel but you must disconnect one of the esc's BEC wire to not blow up your receiver ***

[Glyn Roberts]

Hi Tugtower,

Can I use 9.6V 4300mah SC NiMH Battery Pack with 
Turnigy Aerodrive SK3 - 3536-1400kv Brushless Outrunner Motor
and
http://www.hobbyking.com/hobbyking/store/__67040__HobbyKing_50A_Boat_ESC_4A_UBEC.html.

I feel that I am getting somewhere now,  Thanks.   Regards Glyn

[Tugtower]

yup you can use that battery providing it can handle the 50 amp discharage rate the esc requires please check that asap. if they can't it will result in a murdered battery, or worse a fire.


when esc's & motors talk about voltage in lipo terms and your using nhmi's just compare the lipo battery voltage to a nhmi, '2s lipo =7.4v ... thats equivalent of a 6 cell nhmi at 7.2v, etc..


Only issue with nhmi's is that most cannot handle the discharge rates required, hence why i stated ensure you have one capable of 50,
most 7.2, 8.4's nhmi;s  can only discharge at 30amps max,(most are still old school designs for rc cars) which is when your using brushless esc's over 50 amps i will tell you to use lipo's, and normally 2 or 3s's


only issue is some higher discharge nhmi's they can be expensive, more so then a cheaper 3's lipo which is where you have to thing budget, any nhmi battery that costs you more the £25 and your running brushless i would now say just get a lipo as they are better overall and more ''zoom'' for your cash and in the same price bracket as the nhmi.


hope all this is helping, i'm starting to hate the sound of my own voice in my head 
 

[Tugtower]

If you decide to go down the lipo route, take 10 mins to read through this page i have bookmarked
http://www.rchelicopterfun.com/rc-lipo-batteries.html
A lot of great and exact information which is what you'll need.

[Glyn Roberts]

Thanks Tugtower,

I have learned a lot from you and I appreciate the time and effort that you put forth.    If the batt. cannot handle the discharge I will go Lipo.

Regards Glyn               PS  It can handle 50 Amps

[Tugtower]

No worries bud, most call me Aron, captain grumpy, my mom calls me ''that orible git over there''


i won't tell you what my ex wife calls me its a kiddie friendly forum 

[Glyn Roberts]

This battery claims a 50amp max discharge near top of page,  but under details at bottom of page it states 35amp max?

http://www.componentshop.co.uk/9-6v-4300mah-sc-nimh-battery-pack.html

They did not answer phone at 4-30 so could not get any joy.   Can anyone shed some light on this strange contradiction?

Regards Glyn

[Calimero]

Why even bother with NIMH for such application when LiPos are easily available ? There's even LiFePo4 batteries now.

[Time Bandit]

The LC3542-5T 1080KV Leopard  looks good and the price is right if they make it fly, thats what I want, this boat does not look good untill it is flying.   

Well I thought the target was to get it to fly?
If something like that is "flying" for you, go the route with 35 mm BL and NimH.
https://www.youtube.com/watch?v=xim53MEv4Ew

If not, you should rethink, those motors are pretty comparable to a  700 brushed motor regarding current "capacity" but are running on less voltage.

Just guessing the weight to be >20 pounds if finished?
Think about at least 30-40W per pound of weight to bring it to twice the speed you see in the vid.