Whats going on??-boat wont plane

[mm123521]

All,

Over the winter I built up a twin SprintCat 40.
It's actually 34.5 inches long.
Running CC1520 - 1600KV motors on 5S -- 33300 no load rpm.

The ice is just melted off the pond in Illinois so I gave her a run.
First run was using 442's right and left, Sharpened and balanced (otherwise stock).
It took 15 feet to get on plane, there was a lot of cavatation.
When on plane, the hull ran flat. There was no bow up attitude, but it ran fast.
Roster tail was 90% flat- about 2 feet high, the other 10% was a light mist that was 5 feet tall.

Ok, I took the boat home and opened up the hatch. 100% dry.
I wanted to get rid of the cavatation so I installed new props: 447's S&B, silghtly detounged.
Charged the batteries and ran back to the lake.

The boat would not get up on plane!
Motors ran, the hull "pushed" water.
No cavatation at all.
The props were fully under water.
If I ran it for 50 feet or more, it would kinda plane.
The full length of the sponsons were in the water and the speed was SLOW.
It didnt seem like the motors were turning 33,000 rpm.

Two batteries in parallel for both ESC's.
5S, 5000MAH each for 10,000Mah total.
ESC's are T180. The low voltage cutout = 2.8 volts.

Is this a Low voltage cutout problem?
If it wasnt, I should have burned out the ESC's trying to turn the props at 33,000rpm?
If I turn off the LVC, how do I keep from damaging the batteries by too much discharge?
Should a CC1520 turn 447 props? Boat weighs 15 pounds RTR.

Mark

[Raydee]

So it ran fine with the 442 props but wouldn't get on plane with the 447's? I don't think its a low voltage cutoff problem. Might be that the props are just a little to much for the motor's and they are not getting enough RPM to get the boat up on plane. Might just need to raise or lower the strut some too.

[Rumdog]

No way. The 1520's will easilty spin x447's. I'd bet it is an esc setting. Make sure they are set for the proper voltage.
If I were you I'd run 6s per motor. I rant this exact setup in my Sprintcat with the x447's and it was a rocket!
Where is your CG?
Throw up some pics if you could of the layout and transom.

[keithbradley]

No way. The 1520's will easilty spin x447's. I'd bet it is an esc setting. Make sure they are set for the proper voltage.
If I were you I'd run 6s per motor. I rant this exact setup in my Sprintcat with the x447's and it was a rocket!
Where is your CG?
Throw up some pics if you could of the layout and transom.

I ran a pair of 1520's with x447's in my twin cat and it was downright violent, even when I tried running it on 3s. If its not planing on 5s it has to be an esc issue, and if it is LVC, I would say you have a bad cell somewhere.

(2) 447's produces a lot of thrust. Planing should not be a problem...you should be able to pull a bowling ball and still plane out.

[785boats]

A lot of people seem to have this problem with the T180 ESC's. A few in our club have had it too. Works for a couple of runs & then seems to hit LVC even on fully charged packs.
It is a problem with the LVC.
Did You set the cell count for 5s? Do not rely on the 'Auto Cell Count Detection' mode.
Also, 2.8V setting is too low. If you ever hit that under load you will damaged your batteries. 3.2-3.4 would be better.
If after you set the proper cell count the ESC still wont perform, the remedy is to switch off the LVC option. This will fix the problem. So you might need to get an external LVC unit if you think you need one. I personally don't run a pack down to the cutouts.
The other thing is that the Throttle Range needs to be set with your TX. It can't be done with the program card. It must be done with the TX. It's in the instructions somewhere. Failing to set that can also restrict your top end revs. Note... set this first, before you play around with the other settings.
hope this helps a bit.
Paul.

[sailr]

785boats has excelleng suggestions. Another thing I'd look at is lazy batteries!

[mm123521]

Ok guys -- thanks for the advice.

This is my first FE.

I have been getting the boat ready for another run and thinking about this.
I ran it long enough, fully wet, and pushing water to have smoked the ESC's.
So it must have been a LVC problem - I hope.
Checked the ESC programming and shut off the LVC.

Ok Keith, I forgot to attach the bowling ball, I'll put one on for this run!!

Rum, CG is about 10.5 to 11 inches - it should be good there? How heavy was your twin sprintcat? Am I too heavy @ 15 pounds RTR?

Raydee: that was what I was worried about -- the props were just too big, but Keith and Rumdog have run this setup and it looks like the CC1520 should pull the 447's

Batteries look good, they are balanced within .01 volt.

Allright, I am heading out into the cold (45 degrees) for the third run!

Mark

[sailr]

You can't tell anything about lazy batteries on the bench. They will test out just fine...but when put under a load, they have simply lost their oomph. I also fly planes. When my boat batts get lazy, they still work fine in planes because aircraft motors don't put the heavy demand on amp draw that boats do.

I would suggest getting or borrowing some known good batts and by all means run on 6S, not 5S.

[mm123521]

785Boats,

I was almost out the door, and I saw your post.

That was it! Throttle range. Thanks Paul.

I just put the tachometer on the prop and it was only running 19,000rpm!
Somehow it got messed up between the first and second run.
On the bench, that 19,000 sounded like a lot, but 33,000 really sounds like a lot!!!!

OK, I gotta reset the LVC now.

This site sure is great, Thanks everyone!

Mark

[keithbradley]

785Boats,

I was almost out the door, and I saw your post.

That was it! Throttle range. Thanks Paul.

I just put the tachometer on the prop and it was only running 19,000rpm!
Somehow it got messed up between the first and second run.
On the bench, that 19,000 sounded like a lot, but 33,000 really sounds like a lot!!!!

OK, I gotta reset the LVC now.

This site sure is great, Thanks everyone!

Mark

Make sure it is set specifically for 5s, not auto detect (as 785boats mentioned). Its common to have LVC problems when using auto detect.

[mm123521]

All:
Back from the lake.

Wow! This is the most fun boat I have ever run!!!!
It does explosive hole shots! (they were a little slower when I ran with the bowling ball, Keith)
Perfect running attitude, bow slightly up.
Great acceleration out of the corrners.
I even did a full speed turn -- solid as a rock, of course the water was like glass today.

I ran it for about 6 minutes (did not want to quit) and the batteries came back with 3.8 volts -- so good run times also.
I am guessing 55 MPH, but this is 5s and I have two sets of 6S batteries waiting to try out.
Also got a pair of CC1518's (1800KV) to replace the CC1520's (1600KV), when I get practiced up on my driving.

Rum, this one was inspired off your twin SprintCat --- Thanks!!

Wanted to video, but no one wants to go out in the cold with me, next time Ill get a camera man.

Keith, got her set up on 5S for sure - no auto detect - Thanks!

Mark

[785boats]

I'm glad to hear it all worked for you.
Take a special note, in the instructions, of the three instances when you have to recalibrate the Throttle Range .
But I would still raise the cutout voltage to 3.2 or 3.4V if I were you. Or did you?
2.8V is too low.
All the best.
Paul.

[mm123521]

Paul:

Yes, I raised it to 3.0 before yeserdays run.
I will definatly raise it to 3.4 for the next run.
I took the boat off the water with 3.8 volts remaining, yesterday, because of your cautions. I thought about what you said all the way to the lake, and knew I was under protected.
Thanks for the assistance, I would have had another failed attempt on sunday, if you hadnt sugested "Throttle Range".

I'am on a high! Wait till the boys down to the pond see this thing run. I am the first to go electric at our boat club.

Mark

[Rumdog]

Congrats!
By far the best boat in my fleet as well!