Broke into the 70's on 3s with a single drive 32" cat

[kfxguy]

So you guys (most of you anyway lol) know I sank my Rivercat a few months back. Well I sold my 34" mono to build another Rivercat. I just finished it up and it's first run was last weekend. Did pretty well, but let me back up a little. I bought a motor from neu a while back for a different build that I have had time to fool with, so I tried this motor out in another boat. It ended up being the wrong kv. So, I had this idea to try and run this higher kv motor in my Rivercat and see how far I can push it on low voltage. Just for kicks. I see some pretty impressive speeds out of higher voltage with people just adding cells and adding cells to go faster. Well I wanted to try the opposite as its more of a challenge for me. Something different you know. Tired of the same ole stuff. Anyway I've only run this 32" Rivercat on 3s so far and it's a frigging hoot. I built it to run on 4s and 5s if I really want to go fast but 3s is pretty impressive (to me anyway). I'm still working the kinks out and tuning it in but right now I'm at 73 on 3s. I think I can get it to 76-78 on 3s with some more tweaking. Rudder hadn't been shortened or thinned yet. Also I'm running it on not fully charged batts just so I don't get inflated numbers. This was my very first attempt and batts were at 4.0v per cell




I make some changes and a few little tweaks. Batts at 4.10





This pass is taking some rudder trim out and setting the rudder straight. Boat seemed to go straight under full throttle.





And this is a fresh set of batts fully charged just to see what the potential is

[kfxguy]

I wonder if my amp draw is ok....here's some data I pulled from the data log last night:


At 120.5 seconds it's 259.8amps
120.7 it's 265.0amps
120.9 it's 257.1amps
121.2 it's 243.4amps
121.9 it's 212.9amps
122.4 it's 205.0amps
At my peak rpm it's at 202.6 amps.

My temp hit a max of 128f and the motor is cool to the touch. The high amp draw is right when I pull the trigger. What do you guys think? The esc is a mamba xl2 converted to water cooling. It's the same thing as an ice 240. Am I pushing it too hard or can it survive these 1/2 sec - 1 second spikes?

[srislash]

You can back figure the wattage Travis. That will help settle things if you are thinking a setting is wrong. You should know by now what wattage it takes that prop to attain that speed with another setup.

I myself am curious as I am working on a 3s+ setup myself

[kfxguy]

You can back figure the wattage Travis. That will help settle things if you are thinking a setting is wrong. You should know by now what wattage it takes that prop to attain that speed with another setup.

I myself am curious as I am working on a 3s+ setup myself

Well I've only run that prop on one other boat that I've logged. It was on 5s that it was doing about the same speeds and amp draw was in the 180's. So being less voltage I may not be that far off. I think I can raise the strut a tad and lower my current draw though. Rpm is around 30k and figured rpm at 3.7v should be 32k so it's being loaded a little more than it should be. I do have a 1.4 pitch version of this prop, I'll try it. I tried a 1.4 pitch three blade and the mph dropped to 66 and the temps were a good bit higher and amp draw was I think 20+ amps higher.

[TRUCKPULL]

Travis

What is the motor, Y or D and the Kv??

Larry

[kfxguy]

Travis

What is the motor, Y or D and the Kv??

Larry

Umm well the kv was incorrect so the motor is labeled wrong. Not exactly sure what it is. But it seems to work well except my amp draw is a little more than I like. I'm working on that right now. I've been trying to build up the ride pads over the past week and square, sharpen and level them out. Haven't had very much luck so I'm taking a different approach to it. I was hoping to run it again tomorrow and try it on 4s but looks like that won't happen. It's ok tho, got some props that need working so I can try some different things. I haven't shortened the rudder yet either. Still trying to work the bugs....ill keep this thread updated.

[rayzerdesigns]

I wonder if my amp draw is ok....here's some data I pulled from the data log last night:


At 120.5 seconds it's 259.8amps
120.7 it's 265.0amps
120.9 it's 257.1amps
121.2 it's 243.4amps
121.9 it's 212.9amps
122.4 it's 205.0amps
At my peak rpm it's at 202.6 amps.

My temp hit a max of 128f and the motor is cool to the touch. The high amp draw is right when I pull the trigger. What do you guys think? The esc is a mamba xl2 converted to water cooling. It's the same thing as an ice 240. Am I pushing it too hard or can it survive these 1/2 sec - 1 second spikes?

I have been testing my q mono 6s with 56 mm motor and converted xl2.. Have seen peaks in 310 to 315 range and constant 245 at wfo.. Speedo has gotten to 135 on data logger but cool to touch.. 97 hottest ive seen on caps

[kfxguy]

I have been testing my q mono 6s with 56 mm motor and converted xl2.. Have seen peaks in 310 to 315 range and constant 245 at wfo.. Speedo has gotten to 135 on data logger but cool to touch.. 97 hottest ive seen on caps

Well that's definitely good to hear. Maybe mine will live too. Last log my temps were peaking in the high 120's but the esc was cool to the touch. The three blade cause temps around 160 iirc. And it went slower so that answered that. Maybe the heat transfer to the heat sink doesn't work well. I used Artic silver thermal paste and Artic solver epoxy to glue the cooling blocks to the heat sink.

[kfxguy]

Small update. All week I've been working on squaring my ride pads and making them flat to see if it will handle better. Well I went test I today and it did. I didn't get much run time at all, it's been raining. It stopped for a little bit and I decided to throw some 4s packs in the charger. I was packing up and got cold feet with the 4s so I threw a couple 3s packs on th charger and finished loading up. The packs were st 4.05v when I took them off about 10 minutes later. Running out of daylight I grabbed them anyway. Made a pass the way it was last weekend, only change was the ride pad work. 69.8mph and more stable. Batts charged all the way it would have gone faster than it did last weekend I'm sure of it. I worked a new prop while batts were charging. This one was about the same thing I had on it but less pitch. Same diameter. It only lost about 1 to 1.5 mph but it was more stable and the prop walk was almost not even there anymore. Got the courage to throw 4s in it at this point. Nervous. Made a couple little half passes maybe a little more than half throttle. Threw a blip or two in there. Nose came up on one. I brought it in as was about to move the batts further up front (they are a good bit lighter than the 3s setup, 5800 3s...3100 4s packs) and then I looked at the gps. It said 66.6mph. Time to pack up at this point! Lol. I wasn't trying it anymore! I can say that the sound of it when I blipped the throttle on 4s was pretty nasty. If it's not raining tomorrow I'll be back out. I noticed my rudder was angled back a few degrees and I repositioned it to be straight up and down. That should keep the bow down more. We shall see. It'll be another journey like my other Rivercat but this one should be even faster. Heck I started out in the low 60's on 6s with my first one. This one blistered off 68mph on my first 3s attempt. So I'm not disappointed in the least bit!

[kfxguy]

Ok so I had a little time to run it again. Ran on 3s as a baseline. It was down about .25 mph so it was pretty much good to go. Went 72.8, best was 73.0 on 3s. That was with my normal prop of course. Propped down and put 4s in it. Made two clean passes. One up the lake and one back down it. Little bit of ripple and kinda windy. No flips. Whoohoo went this fast with a prop that's a couple mph slower than normal

[kfxguy]

Because I'm never happy with anything the way it is, I went back through some notes of mine and noticed that I picked up some speed on one of my other builds by shortening the power wires and adding more caps. Guess the initial setup was preliminary just so see how it was going to work (like I said before) so not everything was as good and tweaked as it could be. One thing is my wires were extremely long. Guess it's better to have too much than not enough. So I chopped off 2" of length from 4 wires. That's 8" less right there. The batteries, well revo offers the batteries with connectors already installed but the wires can almost reach across the room lol. I tried to get them to do them shorter but no luck. I usually have mine about 3". They come about 5.5 to 6". So I'm redoing all those and that is 10+ inches of wire gone. On my cap bank I only have 4 1000uf 35v caps. I made another one with 10 caps just to be safe. Making changes like this on my other Rivercat was worth about 2mph. So maybe it's worth the effort. Got some new props in today to try out so I should have an interesting weekend should weather permit. I'm crossing my fingers for close to 80 on 3s and over 90 on 4s.

[srislash]

I am real curious what gain will be had from shortening the wires. This follows my thoughts except that perhaps with short wires the caps may not be needed( in an ideal world).

[kfxguy]

I am real curious what gain will be had from shortening the wires. This follows my thoughts except that perhaps with short wires the caps may not be needed( in an ideal world).

I'll sure let you know. I also added some more floatation to the thing just in case. I put pool noodles wherever I could (under back deck, front and right rear empty space) in addition to the two part foam. I also added some to the hatch. I was reading some old threads of mine and you predicted it on my lehner Rivercat. You asked me if it would float if something happened. Well I had more faith in the two part foam than I should have. I hope this one floats if I have any mishaps lol. It should but I won't know till something happens.

[kfxguy]

I didn't get to run it today. Was cold as heck and drizzling. So I went in the shop and worked on some stuff. Decided the little 3100mah 4s packs just weren't enough for what I'm doing and about to be doing so I made some room to fit the 5800 4s packs I have. The 3100's just don't have the amps anyway (I'm really gonna need this extra power for the next few props I try....I've been using low pitch props to start dialing it in...time to get more seriouslol) I'm steady tweaking away at this thing I guess. I definitely expect to pick up some speed from the more available amps on tap. I will test it back to back tho. I want to see how much difference shortening the wiring and the bigger cap bank made. I'm going to get some 5000 mah packs to go in here eventually but I'll use what I have for now. Adding the 5800's adds exactly 1lb to the boat lol. Might be a good thing. I also reset my cg, I had it off a little. The original 97mph Rivercat was running perfect. I set the cg a tad further up towards the front just in case. Now that I think about it, the 18" of wire I removed probably moved the cg further back which made me have to move it up again. Here's my little cap bank I built installed.






Here's a pic that shows the side rails narrowed, moved the gps to the left, used a shorter servo arm (make room for gps and cut the steering rate down) and the pool noodles I added. I wish I could find some black ones. Maybe I could use that dark grey pipe insulation but I'm not sure it floats as well. Somehow need to compare





And I added some ugly noodle pieces to the hatch. Don't like it but I'd rather not lose this boat. I'm making every effort to make sure it will float even if it fills with water. Maybe one day I'll get brave enough to try and sink it in a swimming pool. Or not. Lol

[kfxguy]

Well looks like I'm not going to be able to make an accurate comparison. My charger will only charge to 4.25v today. It's giving me a cold weather message. Apparently when it gets to a certain point it slows the charging dramatically to preserve battery life. I don't have much daylight left so I'm taking them off at the slowdown point. It's not that cold here but evidently there's a default temp setting it does this. I don't have time to mess with it right now so I'll roll with it the way it is. I've been running it on not fully charged batts for the most part anyway.