Home made balsa catamaran

[OldMann]

Eodman - I think what OldMann is saying is the drives should be as close to the inner edges of the sponsons as possible. Thats what I was told when setting up my twin cat.

Graham.

Right. In this case the boat will glide on the water surface. Drag is very small.

[Rull]

OldMann , Graham Thanks!
What is your opinion - will be able 10 wind 540L motor turm x442 in this cat?
or in other words do the AMMO and Roxxy motors have realy power advantages to little bit bigger feigao motor?

[OldMann]

wen choose the engine choose the controler... drives and they have to withstand the engine speed.
I think feigao 10 wind motor 540L Turm x442 is a good choice.

[CornelP]

I agree, my 30" screams on a 540 10XL with 6S, wiredrive with a 45mm carbon prop. I will upgrade at some point to metal prop...

[Rull]

Thanks All for advice!
ESC no problem because i can make them.

OldMann one more question
Please explane why "drives should be as close to the inner edges of the sponsons as possible. "
I understand why they should be as lower as possible, but cant find difference in horizontal plane.

[roadrunner]

Hi Oldmann
I'll start sooner the same catamaran. The size will be nearly 80 cm. I have several choice with brushed motors. At this moment I wont use brushless.
1) 2 motors (Trinity 16x3 turn car motor) geared 2:1 single propeller
2) 2 motors (Trinity 16x3 turn car motor) 2 propellers
3) 700 size neodyme single propeller (not sure)
4) Robbe Pro Navy 20 (like plettenberg) single shaft

Especially I'm interessted in two motors but I can decide between geared or not. what is your opinion?
thanks

[OldMann]

I know nothing about these engines. But if you want to build a twin-engine CATT, recommend no gearbox, and propeller speed to cross the 25,000 rpm.

[NativePaul]

Oldman, if you are running 4s I think a x442 will be too big, I ran a 10L in a 26" lifting scale type hydro with a M442 for a while but I changed to a tonguecut X637 to try and get more run time and it picked up a lot of speed as well as going longer, the pitch of the props is similar but you could hear it unloading revving out a lot higher with the X637.

If you go over a wave with a twin and one sponson comes out of the water (lets say the left for arguments sake) that left side loses all trust from its prop that is no longer in contact with the water, but the right sponson that missed the wave is still in the water providing thrust, with trust coming only from the right hand side the boat slews to the left, and the weight shift towards the right from the left turn slows the left sponson coming back down and exacerbates the problem, the further towards the centre the drives are the less force there is trying to turn the boat left. Ideal from a handling view point is both props next to each other in the middle like you would with outboards but to do as such with motors in the sponsons requires quite hefty S bends in the flex shafts, disallows wire drives, has more aero drag from the angled stuffing tubes and struts in the tunnel instead of hidden in a low pressure area behind the sponsons and doesn't look scale, I've seen it done successfully to make wider oval style cats twins, but folk with long narrow current scale offshore type cats tend to just mount drives on the inside of the sponsons.

Roadrunner, back in the '90s I used to favour 16tripple motors on my geared 2:1 on 7x 1700 nicads and an X642 in my 18" cats for a 4 minute run time in the high 20s, if I was using them again I would still gear them 2:1 but try 3s lipo and X637s or probably a X645 if geared together, I know back then twin geared 540s had the legs on 700s but had trouble getting the runtime so were mainly used for records days but I think that was before 700 neyodyms too, never used one of those or the Robbe motor so cant comment about them.

[roadrunner]

Hi NativePaul,
I know it's a late reply I had the laser cut parts of the catamaran. I start to build. I'll use a powerfull single motor. Not dure but 6S or 4S lipo I'll use, time to go to lipo

[NativePaul]

Cool, 1 big motor will be faster for the same cost or cheaper for the same speed.

[Simon.O.]

Hi Oldmann
I'll start sooner the same catamaran. The size will be nearly 80 cm. I have several choice with brushed motors. At this moment I wont use brushless.
1) 2 motors (Trinity 16x3 turn car motor) geared 2:1 single propeller
2) 2 motors (Trinity 16x3 turn car motor) 2 propellers
3) 700 size neodyme single propeller (not sure)
4) Robbe Pro Navy 20 (like plettenberg) single shaft

Especially I'm interessted in two motors but I can decide between geared or not. what is your opinion?
thanks

I'll jump in here as I have travelled this road well.
Once you are building a boat this size you will need a lot of power to make it run well.
I stuck with brushed for a long time and even used gear drives too. Today with the low price of BL systems there is no need to go through all that pain.

I used brushed and Ni cells well after I was told to go BL and Lipo. I learnt and now can offer the advice.
If you want to then I'll not stop you, but I will strongly advise against it.

Go with BL and go with a single if coins are few.
Twins are fine, not faster but very cool looking and sounding.....I will do one soon.

[roadrunner]

Hey Simon,
Thanks for your advices. Actually I'm building and I'm sheeting the boat. Sure that it will powered by a single burshed (a powerful motor) and depending the boat and my contstruction, it's possible that I change it with a brushless.
To go with lipo, good idea but I have to change all my charging setup, new batteries, new chargers, I wii decide what to do.

[OldMann]

I finished my new catamaran

[OldMann]

...

[TotalPackage]

can i get plans for this hull