33'' mono twin setup

[Sheffield]

Hello,
I need your help about a twin setup for a 33'' mono.

Motors : Dr Mad Thrust 2970 2200kv
https://hobbyking.com/fr_fr/dr-mad-t...sion-29mm.html

ESCs : Seaking 120A

Batteries : 5S

Thanks

[Doby]

So....what kind of help do you need?

[Doby]

2200 kv motors are more suitable for 4S.

[Speed3]

That motor may be limited to a 35 to 37mm prop on 4s. Just a thought, two motors will require two speed controls, counter rotating prop pair, two set of batteries, while a single is one of each. A motor like a 4082 or 4092 will give that boat all it can handle.

[Sheffield]

Ok I understand,

If I use 2200kv motors the batteries must be 4S. If I want to use my 5S batteries I must choose 1900kv motors.
Looking to the size of the hull which choice lookk better ?

[Speed3]

1900kv on the 5s will be better than 2200 on 4s.

[Fluid]

What do you want to do with the boat - sport run, oval race, speed runs, long run times? The motors are rather small for a 33" hull. They will "work" but I think you will be much happier with 36mm motors. Unlike the tiny motors you plan to use, they will swing props large enough to be efficient with that hull.

It doesn't matter whether you use separate packs for each motor or both motors pull from the same pack. You will need enough capacity for the amp draw regardless of the number of motors.



.

[Sheffield]

Is a set of two Aquastar 3660 1700kV a good choice with 5S voltage ?

[Fluid]

That's a better choice IMO. Loaded rpm should be around 25,000 with the ability to spin a larger prop. You should be able to spin counter-rotating x442s for speeds in the 40s. You can probably go up to x447s with large enough ESCs, 100 amp minimum. Speeds approaching 50 mph.


.

[Nevs]

...And I would use struts and put them as low as possible..and as narrow as possible. Maybe 50 mm apart so you can prop up.

[ray schrauwen]

...And I would use struts and put them as low as possible..and as narrow as possible. Maybe 50 mm apart so you can prop up.

That's a nice add in to note for a build of mine, thanks!

[Nevs]

Its just logic. The propshaft can probably be anything between 2 and 8 mm lower on a strut then a powertrim. So you will have anything between 2 ang 8 mm more prop in the water...imagine a deep V hull with the drives 10 cm apart..Even a 447 could not, (or barely), toutch the water in an upright hull position.

[Sheffield]

Great, thank you for your help. Anyway the voltage will be 5S / 18,5 v . Last question about motors, what do you think about those outrunner motors ?

Scorpion HK3026 - 1900kv



Thanks

[Nevs]

Well powerfull motors, (193 g). https://www.youtube.com/watch?v=o3KCKjPuZkc
I am curently running a pair of HK Helidrive 49-56, (about 350 G) / 1350 kv /6s /55-14 props in a heavy 15 pound mono..No problem. So if your boat runs well and not build to heavy (6 pounds ?) I think it would be great.

[Nevs]

if money matters you could get aprox. the same power by using these. https://hobbyking.com/en_us/rotorsta...size-heli.html
And they are not 14 pole, but 6. I know the "new" T-180 works perfect with at least up to 8-pole.

[Nevs]

if money matters you could get aprox. the same power by using these. https://hobbyking.com/en_us/rotorsta...size-heli.html
And they are not 14 pole, but 6. I know the "new" T-180 works perfect with at least up to 8-pole.

[Sheffield]

Well, I never used outrunner motors, the guy sells the 2 Scorpion 3026 - 1900kv for 100 us£ , they are new in the box, never used.
Or I saw those 3650, same size than the Scorpion :



Did you look at Dr Mad Thrust 2970 / 2200kv inrunner motors ? I had one in my hands magnets are very strong but 2200kv ...



Nevs, the Rotorstar 1600kv look strong too, thanks for help guys.

[ray schrauwen]

YOu can get just as good for about $50-$60 US Suppo motors.

http://www.altitudehobbies.com/suppo...otor-500-class

[ray schrauwen]

Scorpions are a good deal.

[Sheffield]

Those SUPPO motors look great , I didn' t know them. I add the link in my favorites.

I think I will buy the NOS Scorpion 3026 1900kv.

[Rcsurfrider]

Ive been using heli motors in my Rc jetboat using 28mm kmb drive. Tiny little motors 12pole 2836 with 700 watts and gobs of torque. I can jump it out of the water to clear rocks going upstream. My other jet boat uses a 3656 in runner . I really like how the outrunner boat motor handles better. I use a high pwm 60a heli esc with it, the esc has an added water cooling plate and it is fully water proofed. So I can run 80A continuous through it now and it stays cool:) The heli esc/ motor seems to give better throttle control compared to my inrunner setup, especially when river crawling.
Im a big fan of outrunners as they are torquey has hell and self cool needing only a water cooled motor mount, which is standard for me.

[RunningBeer]

Hi Sheffield, have a look at the photo galleries on my page, I've built a twin pursuit and a twin pirate. I also don't think 29mm motors will disapate enough heat for you. My pursuit had 2x HET 2200KV 3668's on 4S. The boat was a bit wild, there's a lot to learn about twins (like all boats).RB

[Sheffield]

Hi Sheffield, have a look at the photo galleries on my page, I've built a twin pursuit and a twin pirate. I also don't think 29mm motors will disapate enough heat for you. My pursuit had 2x HET 2200KV 3668's on 4S. The boat was a bit wild, there's a lot to learn about twins (like all boats).RB

Thanks, pictures help me a lot, I will install the blade behind the propellers and motors low as possible.

[Sheffield]

I will use flex shafts with 3/16'' prop shaft .
Which one should you use ? 4mm flex shaft with 3/16'' prop shaft or 3/16'' flex shaft with 3/16'' prop shaft ? Thanks.

[RunningBeer]

I'm a 3/16 man myself. I guess it kinda matters what you have in the ol' prop box.

[Sheffield]

I made a motor mount for two Scorpion 3026 1900kv, the two parts are strongly glued using threated shafts in the holes + epoxy . It is strong enough.

Picture with the modified TFL rudder, motors will be low a possible in the hull .

[Nevs]

It looks great..And the shafts between the 2 mounts is another great idea..I have done this a couple of times but used a 1 piece 3mm aluplate...Your mount will be lighter..

[ray schrauwen]

You can only get one threaded shaft between those mounts to join them no?

I've seen it done before but not sure how it was done???

[CraigP]

Nice, very close mounting! Have you thought about a small carbon fiber piece going from the point of the joint to the hull? That would triangulate that mount nicely! Could be epoxy attached the the motor mount I believe...

[Sheffield]

What do you think about those stingers ? I will order 2 stingers for 3/16"" shafts, any suggestion is welcome


http://www.ebay.com/itm/adjustable-s...72.m2749.l2649