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[victor]

As a long time absentee from electric boats, Mabuchi 540, 550 and 6 and 8 cell nicad packs,  and after an abortive try at electric flight. I find myself with a bag of foam bits but I also have a perfectly good 2.4 Ghz radio, a 1050Kv brushless outrunner,  a 20A ESC, and a couple of 2200 MaH 3 cell LiPos.
I am thinking that I would like to put this kit into a sporty scratch built boat. Due to my absence from the boating scene,  I have no idea what hull or prop size would suite the above combination, could somebody advise me ?  I would like a sporty, planing hull and I get as much satisfaction from building as I do operating so I dont want to buy a ready built and just fit it out. I realise that you can't be specific but a good starting point for hull and prop sizes would be welcome.
Thanks in anticipation.

[Perkasaman2]

There's a couple of builds on Mayhem of the German aeronaut kits and they both have nice deep vee planing hulls. They are high quality and relatively inexpensive. Both will suit your motor, esc etc. Here's one of them.


http://www.modelboatmayhem.co.uk/forum/index.php?topic=42219.msg425719;topicseen#msg425719         

[john44]

Hi victor, I know you said your motor is a 1050kv
but what is its size e.g. is it a 3548/1050
35 being the can diameter and 48 the length
is it a in-runner or out-runner?
Ive use a 2835/1000kv out-runner in my Huntsman31
but with a 70amp esc,and a 40mm 2 blade prop.
turning a prop in water takes a lot more effort than
a plane prop turning in air
so you would be limited boat size and prop size with just a
20amp esc

john

[victor]

Thanks for the replies so far, plenty to think about.
John44, I have measured up the motor and it is a 2630/1050 outrunner which to my reckoning is smaller than the one you quoted.
I would like to get my head around this, when I was building boats before I knew that a 540 or a 550 with a 6 or 8 cell pack and a given prop would give me a good starting point with a smallish hull size, be it a 12" x 6" screamer or a more sedate 18" sportster, and there were tables to refer to. I am aware that the cell voltage x the Kv rating gives me the off load RPM but that is as far as it goes. If I wanted to stay within the bounds of the 20A ESC, what hull and propsize could I go to. I don't want a 1 metre offshore racer or an all out micro screamer just a smaller, semi scale MTB type hull with good planing performance. TIA.

[pompebled]

Hi Victor,

Your ESC is the limiting factor here, unless you make it watercooled, which is quite easy.

I'm running this motor in a 50 cm raceboat:
http://www.hobbyking.com/hobbyking/store/__11875__ADS300_Water_cooled_Brushless_Outrunner_3000kv_300w.html
On 2S, turning a 36 mm surface piercing prop (roostertail), it runs about 30 mph and is a handful to control...

The very effective watercooling keeps the motor cold, the 40A ESC gets handwarm.

As your motor is even smaller, mounting it on a watercooled mount would cool it sufficiently to run it in a MTB style hull, provided you build as light as possible.
If your ESC is a flight type, with an aluminum plate over the Fets for cooling, adding watercooling is simple, using something like this:


Or if you have a drill press, make your own, fitting for your ESC:




There are a lot of (free) plans available, I'm currently working on this Italian M.A.S.:



I have the (simple) plan on my harddrive, so if you want a copy to scale down (mine is 43,3") to fit your motor/ESC combo let me know.

Regards, Jan.

[victor]

Thanks for all the help so far but I have some other questions.
I have several old fast electric submerged drive plans kicking about the loft and I would like to know if there is any reason why I should not build one of them with a surface drive. In other words are there any differences with a surface and submerged drive hull ?
If it is OK for me to do this, could someone help with prop position, I am aware of the transom to prop distance, 10 - 13%, but what would be a good starting point for the prop depth with the boat stationary ?  Also any advice on rudder position would come in handy.
Thanks.

[bj]

.........d around this, when I was building boats before I knew that a 540 or a 550 with a 6 or 8 cell pack and a given prop would give me a good starting point with a smallish hull size, be it a 12" x 6" screamer or a more sedate 18" sportster, and there were tables to refer to. I am aware that the cell voltage x the Kv rating gives me the off load RPM but that is as far as it goes. If I wanted to stay within the bounds of the 20A ESC, what hull and propsize could I go to. I don't want a 1 metre offshore racer or an all out micro screamer just a smaller, semi scale MTB type hull with good planing performance. TIA.

Good article in June 2013 Model Boats mag on page 40 entitled "Brushing up on Brushless". Worth the £4.35 cost. They give a comparison of motor sizes on page43.
OS engines give a comparison of I/C engines to brushless on their web site

[pompebled]

Hi Victor,

Powering a boat by a surface piercing drive, using the same power as used for the subsurface drive, makes the boat a good deal faster, as there's less drag under the hull.
When you look at modern designs for surface piercing driven boats, you'll notice the transom is almost as wide as the middel section.
The reason for this is the weight of rudder and propshaft hanging on the transom and the fact you'll have less lift from the prop as with a subsurface drive.

So avoid designs with a very tapered rear end.
Also make sure the keelline if straight in the last kaf of the hull, too much of a rocker will turn the boat into a bunny when sufficient power is applied, like a flat stone skimming the water, virtually undrivable at speed...

Show us the design you want to go surface piercing drive on and we should be able to say if it's a good idea or not.

Regards, Jan.

[spearfish99]

Looking at what you have got, if you did splash out on a slightly bigger ESC say 40-50 amp ( to give you headroom) something like the old aerokits 35" crash tender or similar would fit the bill.
Have a look at the ESC below. It is what I will be using in my tender along with a similar outrunner and 3s
 
http://www.hobbyking.com/hobbyking/store/__24568__HobbyKing_50A_Boat_ESC_3A_UBEC.html

[pompebled]

Apart from the fact that the ESC mentioned above has a reputation of being hard to program (see the comments below the article), it's also rather heavy, given the weight restriction for the entire boat, if the TS wants to use the motor he has available...
A 35" model is on the large side to be powered by such a smalle motor, so the size would need to be reduced.
The 100 gr may bee too much to get the model on the design waterline.

But, let's wait and see which design Victor is going to build.

Regards, Jan.