"Orange Cat" build 2013 - Fast and Reliable

[cugino]

Hi folks,

Can anyone give me rough amp draw estimation with following setup (test purposes only)?

Motor: Turnigy XK3665 2100KV
ESC: T180
Batt: 6S A-Spec NanoTech 6600mAh 65-130C
Prop: Alu CNC pro 36mm 1,4 pitch and Octura X442?

I think, it will be under 90Amp per motor with X436. But with X442 i have no clue? I am little warried about XK with X442.

If cat perfomes well, i will spend more money for better motors. Its to early, but what would you suggest. I was considering Tenshock EDF 2240/7, Lehner 1950/6 or NEU 1415 1Y. I am limited to 36mm dia. motors.

Or are there another good options?: MEGA, HET, Plettenberg, Kontronik, Hacker, etc..?

What do you think is the best choice and why? If everythink goes well, i will be looking for most efficient setup for speeds around 150kmh for SAW and 110kmh for bashing. 2x3S pack is only one possible battery configuration. So, my vision is to heve in the end two sets of prop. One set for bashing another for rare adrenalin SAW passes. :)

[TheShaughnessy]

are you gonna spin the props in or out? Why 6s? thought those motors would be better on 4s. 46000 rpm is pretty high, even for a saw set up

[cugino]

I decided to use 6S (3+3) because it is common configuration for my all other RC models. I dont want to have separate battery pack for each model, it is expensive.

I dont understand why is 46000 rpm high, when amp draw is low enough? What issues i can expect?

I have experience for five years with that high rpm setup using Hacker motors. Off course, perfect driveline and bearing is a must. It performs quite well and overall efficiency is satisfiing.

I gonna spin props in for few first tests, then out.

[mtbenjamin77]

I decided to use 6S (3+3) because it is common configuration for my all other RC models. I dont want to have separate battery pack for each model, it is expensive.

I dont understand why is 46000 rpm high, when amp draw is low enough? What issues i can expect?

I have experience for five years with that high rpm setup using Hacker motors. Off course, perfect driveline and bearing is a must. It performs quite well and overall efficiency is satisfiing.

I gonna spin props in for few first tests, then out.

the motor will lose efficiency and create more heat than necessary at that rpm.

[cugino]

Thank you for your reply,

do you have any data? or estimate of efficiency lost? Is there any graph of efficiency showing efficiency lost depending on RPM for any motor?

Thank you.

[cugino]

If i understand correctly, u should use lower KV motor then i originaly intended. But with lower KV i should use much bigger prop to keep same speed. I thing, it is not acceptable, i love small props because of handling.

I think, i should find balance point for rpm/propsize/desired speeds/overall efficiency.

[mtbenjamin77]

I would just aim for about 35000 to 37500 unloaded RPM. remember that is unloaded rpm. I've found in some cases a lower KV motor will spin higher loaded RPM than a higher KV motor in the same setup. The prop really needs to be determined by the hull design & size. Determine the best prop range for your hull and start at the smalledst size and work your way up. It's best to use some type of data logging to determine the current draw as your move up in prop size. You can also analyze your current draw by very closely monitoring your component temperatures. Also, it's been my experience that large CR props do really well on CAT hulls. Because they create more lift than samller props and the CR cancels the negative effects you would find in a single drive. To control your lift, first start with props rotating inward, then outward. determine which configuration worksf best and adjust your stingers to fine tune. Also setup your CG so that you have plenty off room to adjust your battery location to compensate for variable water conditions. The stingers can be adjusted for this but you lose forward thrust the more +/- angle you have on your driveline

[cugino]

New season is going to come, my project is going to continue.

Package actualy arrived home. So here R some pics i must share with you all.

NEU 1415/1Y 2200KV will be installed.

DSCN8855_resize.jpgDSCN8861_resize.jpg

[ray schrauwen]

Nice choice of motors. Your attention to driveline vibrations will allow you to get as much out of these motors as possible. Many don't realize how much power is lost to vibration as well as the damage to bearings and the heat created.

You are on track, this will be a very fast boat.

Your hull is absolutely beautiful ! Even Hanspeter would raise an eyebrow. Great work!!

[cugino]

Thank you for your post.

I willl do my best to eliminate vibrations as much as i can.

Now i am waitnig for my hull, it is at paintshop now. I am looking forward :)

Hull isnt build by my hands, maybe next time, i hope.

[ray schrauwen]

Was it hard to remove the wires from the T180? How many watts is your solder iron?

[cugino]

Removing wires was quite easy. I used 100watt high kapacity solder iron. Only about 0,8 second was enough to trasnfer heat to ESC connectors. Any part of ESC wasnt heated much. It is very safe to unsolder wires from ESCs PCB.

I prefer to solder motor directly to ESC to avoid high RPM motor-ESC sync. issues and low internal resistance of very short wires, wight comes to play either. Lighter is always better. Any saved gram is lot of saved watts.

[cugino]

Hull is back from paintshop where 2K filler was applied. I already sended the hull again. Here R pictures.

Tomorrow i going to take her to painshop again, where next two coat of base paint will be there. I have already cut vinyl stickers, pretty simple, i like.

DSCN8897_resize.JPGDSCN8900_resize.JPG

[iridebikes247]

Nice boat I imagine it will run best with props spinning in. Spinning out at high speed I usually run into problems but this is my personal exxperience.

[cugino]

First test will be definetely with inwards rotating props. I am going to do first test with very conservative props 436 only to ensure, the driveline works perfectly and any other problems found last year were solved. Next step will be Alu CNC prop X442. I thing, it will be my final choice for this hull. May by ABC 1616 would work well. I am very curios now, i like high rpm setup.... :-)