Delta Force 33" Speed Questions...

[electric]

Here are the stats.
8s / 28.8 volts , 12L 580 motor. 33" DF (knock off), 120HV Castle ESC
1st - x337 (3blade) 68amps
2nd - x337 70.55 amps, 2070wp, 30mph ( I moved the CG foward, ran wetter)
3rd - x442 101.34 amps, 3042wp, 44.7mph
4th - M445 - 129 amps, 3820wp, 38.4mph


5th run after all the HELP here.
M445 - 126,62 anps, 3727wp, 54.2mph! (The trim tabs got me a whopping 16mph!!!)...

So, does 44.7mph seem reasonable to you on the 3rd run? What I found interesting was that last run was way more amps, more prop, slower speed?? Can the GPS be sometimes less accurate? On the 4th run it "felt" faster, but the numbers say otherwise. I have the CG pushed back pretty far, just looking for top speed. I am kicking out a fairly large rooster tail, possibly I need to turn the strut down just a bit? Looking for suggestions and advice. I am shooting for low 50's as a goal.

This is my first time to a high voltage set up. MUCH cooler temps, no heat issues at all.

[RIPFENCE]

maybe try a higher pitch like an x642-x645 and you should gain some speed...that motor can turn a big prop but i think you may be limited by the esc at 120 amps...the temps on your esc were not high after the 129 amps? or were those numbers just spikes?

[electric]

The number is just the spike. It looks like I need to invest in a 240amp esc or a smaller boat?

[RIPFENCE]

i had a df 33 with a neu 1515 1y which i ran on 6s lipo..my df liked the x646 and i topped out at 54.3 gps...i had a turnigy seaking 180 which ran 100-108 degrees on 3.5-4 minute runs..i would recommend this speed controller especially for the price..i am sure you can get that boat into the 50's with the right prop and a little more esc

[RIPFENCE]

rumdog has a df boat in the build section too that looks like a good setup worth checking out

[m4a1usr]

Can the GPS be sometimes less accurate?

Thats been stated on many forums repeatedly. Its not an accurate tool to gauge speeds. You can use it as a guideline for improvements and changes in setup. But to boast speed or be taken serious as an achievment its just not the truth. Still a GPS is a usefull tool as stated before.


John

[electric]

Thanks for the information on the GPS. So what are people using to get accurate speed measurements? I will re-run the boat with the 445 a few more times to get an average speed and see how that goes.

[electric]

Ripfence, thanks for the ESC recommendation..

[m4a1usr]

Thanks for the information on the GPS. So what are people using to get accurate speed measurements? I will re-run the boat with the 445 a
few more times to get an average speed and see how that goes.

If you dont race where there is a set of trap lights already setup you can run between 2 bouys (or more) that are set at a known distance and you can time the run between the bouys. It helps to have a couple friends and stop watches plus communication but you can get pretty good at doing it with just another person (fellow boater). Bottom line is it will be more accurate then GPS.

If GPS was truely accurate then the clubs or racing associations would allow its use during races or for meets where setting records was the goal. It would become a standard as it does make things easier for the sponsoring organizations. Just throw a calibrated unit in the hull and make few passes. Log the results or down load the data. What could be easier?

Again, a gps is a decent tool to use for us sport boaters. But if a person thinks he's going to impress the racers with speed claims based on a gps he is talking to the wrong crowd. They know better.

John

[Mel279]

Here are the stats.
8s / 28.8 volts , 12L 580 motor. 33" DF (knock off), 120HV Castle ESC
1st - x337 (3blade) 68amps
2nd - x337 70.55 amps, 2070wp, 30mph ( I moved the CG foward, ran wetter)
3rd - x442 101.34 amps, 3042wp, 44.7mph
4th - M445 - 129 amps, 3820wp, 38.4mph

So, does 44.7mph seem reasonable to you on the 3rd run?

This is my first time to a high voltage set up. MUCH cooler temps, no heat issues at all.

Thats pretty slow for 8s setup, could u give detail about your 8s lipo mah?seem that your boat is heavy and getting slower when u prop up.

[electric]

Thats pretty slow for 8s setup, could u give detail about your 8s lipo mah?seem that your boat is heavy and getting slower when u prop up.

The MAH on the Lipo's is two 4s packs with 5100mah and 40c rated. I have always wondered about the hull weight since it is a knock off. The trim tabs seem excessive in size to me as well. I did contemplate(yes I am thinking of this stuff in bed as I try and go to sleep at night) taking off two of the four tabs just to see what effect that has as well.

By the way, I am also thinking people are "puffing" their speed numbers! I was running the calculations on the estimated speed of the boat based on prop size and voltage and it is pretty closely matched to what I got with the x442 so I am thinking I am getting about what you would expect? Without finding a club to race with in Texas this forum is my only way to get some idea whether I am on the right track or not.

Maybe the amp meter itself could be constraining me in some way? Here are the specs:
Color: Blue
Current: 0-100 Amps
Power: 0-6500 Watts
Voltage: 4-60 Volts
So I am exceeding the amperage rating (still works by the way), but there is a lot of wire with all this measuring stuff.

The other item, is I do remember seeing a setting for the castle esc software that had some feature that I think limited the esc amperage flow to avoid frying the esc. It was a setting that had something "cutoff" setting. Not the voltage cutoff, but something else.

At this point, I have a couple choices to get to a reliable 50mph speed. New DF hull, bigger ESC, or ???. Trying to figure out which is less expensive...



I am going to run the m445 again today to check the speed again and then go from there. I do have a x447 I could try, but I think that may very well kill the 120HV amp esc I have.

[DISAR]

Sure many people give some "advance" on the gps numbers more or less. Don't chase speed numbers, you will never finish. Just to be happy with the boat and to handle well.
The 40-45 mph speeds are reasonable and very good, higher speeds are most of the times only for one or two passes, you should choose what you want. The 45 prop should give more speed than the 42. Probably in your test run something happened, probably lipos started to discharge considerably.
For more speed, a couple of thoughts are:
centre of gravity 27%-29% from tansom
trim tabs upwards (3-4 mm) from hull bottom

[electric]

Thanks Disar, yes I am going to do some speed runs(for river bragging rights) and then back off for fun. Thanks for the trim tab suggestion I am going to do that for my next run.

[electric]

Disar is the winner!, The mystery is solved. I just did a run and turned up the trim tabs quite a bit. The results:
M445, 126.62amps (peak) 3727wp, 54.2mph!
The boat was running on the edge of stability, but now that I understand what was holding me back I am going to dial in a bit more on the trim tabs and then also move the batteries forward until I get the right blend of speed and control. Thanks everyone for your help!!!

[RIPFENCE]

Nice job...maybe if i had turned up my trim tabs up my inaccurate gps reading would have been even higher...but then i would be bragging about it or something...good luck with the df