Trouble breaking 70

[blackcat26]

I've been experimenting aroung quite a bit with my blackjack twin and am having a really hard time getting to and past 70mph. My fastest setup on 4s was with the Turnigy 36-56-2600's and x442's running 68.8mph gps'd. I thought I would try my Align 600xl's (1650 kv rated for 1600w each) in there to see if that would get me where I needed to be. So far they have only yeilded 69.4 mph turning some 447's. How can a motor with like 4x the wattage only give me one more mile per hour? Need input bad. They are rated for 85a max and I am running them on (2) 3s packs in series with 5000mah 40c batts. Are they requiring more juice than the batts can dish out? Any help much appreciated.

[Fluid]

What a motor is "rated for" has little to do with the power it actually puts out. That is determined by motor load and efficiency with the watts into the motor. But 'power' alone is meaningless without efficiently transferring that power to the water.

Your Turnigys are spinning up almost exactly what I'd expect for 2600 Kv motors on 4S with x442s at that speed. Ditto the Align motors, just what would be expected. Your problem is you do not have enough pitch in the props to go faster with those motors. You could put the x447s on the 4S setup, but they might be too big and bog down the smaller motors. Reduce the diameter to 42 mm and you'd be golden. The other idea is to pitch up the x447s on the 6S setup. That, or go to motors with a higher Kv on either voltage.

I'm surprised you are keeping the BJ on the water at those speeds, you can't be running at WOT for very long....



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[blackcat26]

Thank you Jay. What about the power demand on the 6s setup? Do you think my packs are supplying enough juice? I have a set of raw 450/3's on the way. Do you think that if I whittled them down to 447's would it help? As for stability it's pretty stable, moreso on the turnigy setup (I could stand in it from a dead standstill and just go). With the Align I leaped the 8.3lb boat out of the water about 3 feet from a dead standstill earlier today. If I decide to stay with the 4s setup what about the Castle/Neu 2650kv's? Will try and get some video this weekend. 70 will be broken......

[RCKong]

If I remember right Mudl ran his boat with 2600's like yours, but had to run 5S to get it over the 70mph mark... man thats alot of kv ...also a set of those new hyperion G3 EX 45c lipos might get you over the top also.

[Flying Scotsman]

I do not understand this speed fixation....no wind..no chop and yes you can achieve high speeds on a well setup hull BUT that is not what is all about. I want to run my boats under all conditions that are stable with adjustments unless you are a saw racer. I do not like to send out the rescue boat, but this one is cool

http://thechive.files.wordpress.com/...t-12.jpg?w=500

Douggie

[blackcat26]

If I remember right Mudl ran his boat with 2600's like yours, but had to run 5S to get it over the 70mph mark... man thats alot of kv ...also a set of those new hyperion G3 EX 45c lipos might get you over the top also.

Kong you are correct about the 5s. He ran a lone 5s batt for the power. I am a little worried about turning 55k unloaded. (eventhough its only a $20 motor) I will say this I'm impressed with the Turnigy line especially for the money.

Douggie, to help you understand this speed thing here it goes......I just set a goal for myself of at least 70mph. It may be silly to some and it has been a real challenge so far. One good thing is that I am learning alot on the way there. First maiden run was 61mph. BTW, love the rescue boat picture!

[RCKong]

Well like you said the motors ore only $20, and if the props are in the water they are loaded. I'm sure the SAW guys run past the SAID limits too.
FE boating is what ever the individual boater wants to do - some for scale, some for modeling, some for speed, and racing - as long as it's what that individual wants to do, and has fun with it, thats what counts!!!

[blackcat26]

Amen brother. How is your 26 twin doing?

[RCKong]

Man Dude, I'm struggling with this boat like no other I have ever had. It's still a work in progress. I asked for help on this site with no reply. I put it down for a while because it was REALLY pissing me off... Every time I set it up and run it, I flip it and it gets wet inside so its done for the day... The radio acts as if it is on a 1 second delay. I'm having trouble with the radio signal because I put too much CF in the boat. I keep playing around with moving the radio, but It has not helped. I might have to go back to a 75mhz FM with an antenna. I might get pissed enough to try to burn it down.... HA HA HA... 2 CC120's on 2 AMMO 2600's on 6s with 447's bet she'll do 75 before she burns...

[blackcat26]

Here is one thing I have learned about this boat, it hates the 447 unless just a straight wide open run. The 442 is much better suited and acting on this hull. Also the 6s makes this thing very heavy, probably too heavy. My advise is 4s and 442's and as Fluid stated pitch em up. Are you running 6s to each motor or 3s to each one?

[RCKong]

I'm just trying to make the 4s with 442's work. No 6s...just a RANT

[blackcat26]

What kind of speed have you gotten so far?

[RCKong]

Oh its fast, a tick faster than my DF33 clocked at 59 with a 1521 in it. I have to borrow a gps or have a gun on it to tell actual speed, but it's more than difficult to operate it. It's hard to get it wide open, without some kind of glitch, with the radio the way it is. I have a spektrum receiver with an antenna I might try that next

[mschaffer66]

Don't you just hate when you ask a question and instead of an answer you get people offering their opinions on why what you want to do is wrong?

Good luck with the quest for speed :) I think making your boat as fast as you can get it is cool. If it isn't all of those guys that try to break the sound barrier on the Utah salt flats must be dumb too :)

Have you tried a prop thats been worked a bit more? The owner of our hobby shop used to be deep into boats and neurotic about sharpening, balancing, and shaping his props. I ran one of his crazy props on my boat and just the difference in my balance and his prop was a few mph...an idea?

[blackcat26]

Well a few mods. Fluid recommended to pitch up a bit (that is a great idea). Not at all sure how to go about that myself. I have detounged a few sets now and have a set of pretty wicked 442's that I back cut. This weekend I will break 70 with the 447's, and hopefully faster than 70 with some light chop.