Here is another new one!!

[golfmike]

Hi there gentlemen,
I'm Giovanni from Italy Rome
A friend of mine gave one of his old projects.
posting few pics how it was and how it is now.
the boat is a fiberglass selfmade 82cm (32'')long 22 width (8.2'') 7cm (2.7'') hight and empty weight is 1,4 kg (52.9 oz).
2012-03-27-12.55.40.jpg2012-03-27-12.56.19.jpg2012-03-27-12.57.15.jpg2012-03-27-12.58.06.jpg20120814_190710.jpg

Now the questions are:
as it will be a brushless motor boat what kind of hardware set up should I get?

By now I'm oriented on these:
STINGER Surface Drive 3/16" flexi-shaft with 3/16" stub shaft
130mm long rudder
5mm to 3/16 flexhex coupling
2 mini turn fins aluminium
watercooled motor mount brushless and 380 540
medium trim tabs
X440 bronze 3/16 dog drive propeller
Rubber bellows for radio linkages
2075kv 3674 brushless motor
90Amp Watercooled ESC

Am I going in the right way? Any suggestions? As I have been told this is the best forum for electric rc boat
I'm expecting many advices and tips for my boat.
By the way I'll not go on racing but I'd like it to be fast ...

thanx a lot gentlemen in advance I'know you are the right guys for me.

Bye bye from Italy .... (PS sorry for my english but .... I'm Italian and it is not easy to be tecnical)

[TheShaughnessy]

looks like you are going the right direction. Do you have a picture of the bottom? Do you plan to keep those thru hull pick ups? You might want to consider removing them, filling the holes and using a rudder that has a built in pick up.

[golfmike]

Hi TheShaughnessy, and thanx for replying me...
here are few pic of the bottom, don't know if you can see much but I put some plastic around the boat to take it away from dust while still workink on it.

20121106_121325.jpg20121111_083215.jpg20121111_083239.jpg20121111_083254.jpg

In the first pic you can see the inside where there are the servo, reciver, ESC mountings and the flexi-shaft lock self made in carbon fiber,
and yes I'll keep the hull pick ups (do you think they do not work well?),
Do you think the motor will be good for the boat? I've been told to get this one .... as still do not get why a 2075Kv should be better than a 3000 something Kv...

thanx a lot again

[siberianhusky]

The under hull pickups work great, no need to change them at all as they are already there, just make sure they are flush with the bottom of the boat. I use them on a couple of boats.
2075 on 4s gives you a good prop rpm to work with and a much lower amp draw than a higher kv motor running a lower voltage turning the same prop. Ballpark you want about 30 000 rpm unloaded. The lower the voltage the higher the amperage to make the same watts. VxA=W
You have to pay attention to the rating of the motor, and not the maximum voltage! The watt rating is what tells you how much work the motor can do and depending on your voltage how many amps it will take to do it.

[golfmike]

thanx for helping me ... well the specifications say 900w for the motor hope are good for my boat..and so you are suggesting me a 4s lipo ...

[TheShaughnessy]

yes 4s for that motor. the thru hull pic ups work good, i used them in my first boat, a sv27. Like siberanhusky said though, just make sure they don't extend more then 1/16 of an inch (1.5mm) below the hull or pretty much flush. The reason i don't care for them is because they airate the water before it gets to the prop, the effects of this will be minimal though and you probably wouldn't even notice a difference if you got rid of them. If they are too long they will cause excessive drag and will cause all sorts of handling problems. Your motor is a good match for the boat.

[golfmike]

Ahh ok now I got it, the pic ups are more or less 1.5 mm as you said so I shoudn't have any problem with dragging or handling...
By the way in my boat specs I said the empty weight (or zero hardware) is 1,4 kg (52.9 oz) but don,t know which kind of misurements do you have in
USA ... do you think it will be to heavy at the end of the story? I mean with the full set up I said mounted plus a 4s 5000mh lipo,servo and receiver that I didn't
mention at all .... probably the servo will be hitech around 8kg of torque and the reeiver will be the hitech Atom3 from the Aggressor SRX Pro 2,4 GHz 3 Ch....

Uhh yeah I forgot something could you explane me how the CG works on boats??

Sorry for my many and silly questions but I'm really new on rc boats, been up for years with rc nitro cars only...
thanx again dudes

[golfmike]

UP....

[golfmike]

Hi there I doing to get a 2075kv 3674 brushless motor is the 90Amp Watercooled ESC the most powefull ESC I can put on?

[siberianhusky]

For the CG you want it 27-30% of the hull length from the transom.
32x.3=9.6
so about 9 1/2 inches from the transom.
For the esc the higher the amperage the better within reason, you could get away with a 120 amp esc but I'd run a 180 or 200 with that setup, better to have the extra capacity. You would be close to the limits of a 120. I personally don't like running an esc too close to its maximum ratings. Not that big a jump in price from a 120 to a 180 or 200, I've had good luck with swordfish ecs, and the new version has data logging, haven't used a new one yet so not sure how the logging works.

[golfmike]

Hi siberianhusky!!
thanks for you explanetion,
this is the motor I'll get and specs:

motor.jpg

Brushless Watercooled Motor 3674 900W 2045 KV For 8.4 to 12 volts. 2S to 4S lipo or 7 to 16 Nicad or NIMH packs. Mounting hole spacing of 19mm or 25mm. Motor diameter 36mm, waterjacket 46mm diameter, length 74mm. shaft diameter 5mm. Max Amps 85.
Replacement for 700 size motors but MUCH more powerful. Use with 70 to 90 Amp speed controller.

and this is the ESC:

ESC.jpg

HW Brushless watercooled 90Amp Speed control (ESC) with 180 Amp burst. complete with full instructions Battery (cell): 2-6S Lipo 6-18 Cells NiMH. Size 94x33x18, Weight: 81g
Forward or forward and reverse.

But in your opinion I could get this one:
HW Brushless watercooled 120Amp Speed control (ESC) with 240 Amp burst. complete with full instructions.
Forward or forward and reverse.


Do you know this motor ? The ESC are seaking... any opinion?

thanks again

[golfmike]

up up

[siberianhusky]

I don't know that motor, but it should work fine on the 120, a buddy runs a tacon motor of that size with a 120 amp esc in his rigger and it runs well, because of space limitations he can only run a single 4s pack, I'd suggest a pair of 4s packs in parallal since you have the room, much easier on the battery.
Watch the esc and motor temps at first and I'd start with no more than a 42mm prop

[golfmike]

thanks siberianhusky Iknew Uwere the men for me....lol

I'm making all these questions as I'll order everithing for Christmas from UK dealer the best one here in Europe... but want to be sure I'm ordering
the right setup....

what do you think the speed would be with this setup???

[siberianhusky]

That depends on many things, for fun sport running I'd say 75K/h good conditions 80. Thats with the setup dialed in and probably a bigger prop than I suggested to start with. There are so many things that will need to be adjusted after the first run it's always best to start conservative for the initial prop choice. It doesn't take long for a poor setup to start creating lots of heat, usually the esc is the first to go.
As you get the boat tuned you can usually run a bigger prop and keep the amp draw within reason.