Twin 380l or XL powered Cat

[Simon.O.]

As most of you know I have done my searching and reading so here are the questions now.

Can a twin 380 powered cat be seen to go 35-40mph or above. ??
What length is the max to get a twin 380 cat to 35-40 mph ??

This is a fact finding mission to see if doing a twin 380 build is the go as a winter project.

You may ask why twins ?? Fair call. I want to !!....if it will move out to 35 + mph.

I have a single 540S powered cat and that is a lot of fun and think that a twin would be cool to add to the stable.
IF a 380 powered cat is not the go then I may entertain the idea of a 540L or XL twin build. Naturally this will be a lot more costly

I can design and build as some of you have seen !!

Give me a few numbers to play with and we will see what happens!!

or I could do a big Canard, 6S rigger, 5S hydro......OR ???

[NativePaul]

Brushless 380 or can 380? if its a pair of can 380s I doubt you'll get 35 as there only good for about 100W each and are only about 50% efficient, if you mean BL 380s you should hit it easily, I have an 18" cat that did 34.6mph on a single mega 16/15/3 380 size motor and 3 very old 10C LiPos, twin BL 380s should push a 26" cat to 35 without too much problem but smaller may well be faster, be careful choosing the motor KVs as there aren't too may sizes of left and right hand props. how many cells do you want to use? The 3000kv 3s setup I ran pulled about 35A on an octura x430 (which is available left and right handed) but my old cells were only about 9V under that load so a modern 3s pack will be faster and pull more amps, 50A ESCs and a 3s 5000mah would work well.

[Simon.O.]

Cheers for the reply Paul.
This would definatly be BL motors. 380L or 380XL and you are right about the props 430's would be the preferred option.
I am deffo looking at 3S lipo power and 1 pack per motor so two complete power systems.
3S 2000mAh + ESC + 380BL motor + 430 prop.
If I run two battery packs do I run them completly independantly or do I go 2P and then split the power out to the ESC's.
26" sounds o.k so far, I may be looking at 29-31" if so then I guess that the 380's will be a little small to get me to 35mph and above.

This is still a data gathering exercise at the moment.

[RPC1]

I have a BBY SC21 with a feigao 380 8XL on 2 3s 2100mah batteries in parallel. I use a Grim Racer 3655 prop and run 35mph good temps all around. I would use 1 battery per esc so that the LVC will work with the battery independently instead of discharging one battery more than the other in parallel.

[Flying Scotsman]

Simon, I presume this will be a hull of your own design?
If so, I would suggest submitting your hull design ideas and proposed lengths to some of the cat gurus. I am sure that they will try to assist you in your endeavour.
You are a brave man to design your own cat and I will look forward to seeing your results. A stepped hull may be the way to go based on H & M prior sucesses and failures.

Douggie

[Simon.O.]

Douggie, you are right this will be one of my own designs again. i currently have a smaller 25" cat, 23" to sponson rear.
This one has no steps but does have a 3/4" wide flat ride pad from mid to rear on the sponson bottom.
I still have a lot of notes on cat design from the research that went into that build.

For the twin i have not settled on a length yet as I am looking at this one a bit backwards.
I can put a 3S lipo,ESC, 380L or XL (Twins) package together for a very reasonable price, in fact for about the same as a 540L single package.

Here is the dilema. I am keen to go fo a Cat that is about 31" -33" overall therefore 27-29" to sponson rear. I am trying to see if twin 380's will get me the power to get this up to 35+mph.

If not then I will track down a set of the plans as used by shockerman and lonewolf on rrr and go from there towards a twin 540L cat.

The design and drawing is the easy bit. the build is not hard, just time consuming. paying for the power is the hard bit.

[Flying Scotsman]

There is nothing wrong with twin motors..they look fantastic, but they add cost. I presume you already have the motors and then this makes sense. If not, a larger can motor will provide what you wish, as you well know.

Douggie

[robby76]

look at this cat

this is a very nice hull. buy it bare and do your twin build. several members here have it;

http://www.offshoreelectrics.com/pro...?prod=TP-Jolly

Steve can get it for you along with the "enhancemant" addition.

[Simon.O.]

As some of you will see I have a Cat design thresd going too, I am not double dipping this is a specific thread for twins-for me.
I know that twins does not mean twice the speed even if there is twice the power there.
I am well keen to build a big cat and it will need to have spectacular acceleration, back flips are inevitable.

Here is my proposed setup.
32" - 29"(wet) long narrow scale type Cat. The e-bay one is about the right shape for me to copy in light ply and balsa. It is only fair that I use that to copy off as it is a copy in any case.

Twin 380XL brushless motors and applicable ESC's
If I can find a high enough wind then I will go for one 4S pack split to the two esc's
Otherwise I will go for 2S each side in completely independant systems.
This is down to the packs I have now.

Will a pair of 380XL motors on 2S (or 4S depending on wind) spinning 431 L/R props get a 32" light-build cat up and running towards 35 mph ?

p.s I draw and build my own hulls..........it is alot more fun.

[Simon.O.]

o.k here we go after a bit of search arround on the @bay I have some new plans.
I can do 540L motors for the same price as 380xl or 540s units.

Proposed setup.
30 + inch long narrow cat of my design and build
Twin BL 540L motors #10, 11 or 12
4S1P lipo of 4500 mAh or more
Twin 60A chinese speedies 1 for each motor
Octura props 431 left and right
Wire drives.
All my own hardware, I can make anything I need.

All opinions and questions are welcome.

[Flying Scotsman]

Simon, I would bump up the ESC rating to 100amps, not knowing what brand you intend to use.
Are you still trying to obtain a speed greater than 35mph? That may be a problem with 431 props on the hull length proposed

Douggie

[Simon.O.]

Fair call there Douggie.
I can go 100A speedies on 10-12L motors and easilly up the prop size.
Given that I should be using L + R props there is limited selection.
I can use the Graupner Carbon props but they begin at 40mm in L+R sets.

What we need to know here is if Counter rotating props are a MUST for twin setups.
What happens if I use L turn props only. I have a few ideas but would like some experienced answers.

So we are now at.
32"+ Cat
Twin 540 10-12L on 4S
Twin 100A chinese speedies
????? for the prop.
????? for a possible speed.

[NativePaul]

I run a 12L on 4s in a 26" sport hydro, I started with a Pheonix80 ESC but it wasnt quite enough and I had to turn the current limiting off for it to work and whilst it didn't get too hot unlimited I don't like doing that and bought a hydra 240 to replace it which is way ever the top really but future proofs me to a certain extent. I started with an Octura M440 but am now using a detounged X637 which is less load but much faster, I haven't timed it as we had no records day this year but its hellafast, way too much for my hull, I'm building a 32" hydro for that setup now, a 30" cat with two should fly. The amp draw isn't huge either so you should be able to get away with a single 5000mah pack for both motors as long as you keep the runtimes down, I get over 5 minutes on my single. The graupner carbon props have less load than octura one which would help for the 40mm, I have heard rumour that it's not just the smaller blade area but that graupner carbons are 1.2 pitch instead of the 1.4 quoted.