Genesis on 10S not fast enough

[martin]

The way i calculate would give 77mph but thats using 44000rpm at the prop & not using 80-85% motor efficency.

[Mtwinste]

Even if I had the Eagletree I wouldn't know what I was reading. I'm a nitro buggy racer who got the FE itch and wanted to see some real speeds. The amp draws and current lingo is something I'm playing catch up on.

I've set the boat up from advice I get on the forums so I appreciate all the help.

DASBOATA is doing my prop work and seems to be quality so the props should be in good shape. I'll try the M445 this weekend and give y'all an update.

Running 60sec at a time with hatch locks and tape is a PITA

[T.S.Davis]

If you time your run and then measure how many mah you put back in the cells you can come up with the amperage. Then it's easy to decide if more prop is the answer. Winging it can be a mess. Pushing until it burns is the expensive way.

[Fluid]

Considering the small prop on the end of the cable you would never have gotten there. If looking for a specific speed you need to do the math first, and that motor (not the most efficient) will spin around 38,000 rpm on the water. Your boat is achieving very close to my own software prediction based upon what you are telling us about it. To get to 80 mph with your setup you need around 2.8" to 3" of pitch, and an x445 simply won't do it.

But as important as the prop is, the boat also needs to be correctly trimmed. If it runs wet it will never see your desired speed goal. It needs to be running lightly carrying the fronts of the sponsons clear of the water. The rudder needs to be nearly parallel to the boat's axis, not trimmed a lot to the left. I suspect that your cat is running pretty well at 62 mph, but how it will run at 80 mph can only be known by trying. Work up with increasing prop pitch checking temps often.

An example: my current 6S SAW cat ran just 56 mph on its first test because it ran real wet. Once I trimmed it out properly it picked up over 30 mph - no other changes. Simply throwing lots of money into a build does not guarantee a speed demon. A fast boat is a system which requires all parts to be working together, including the driver. It also requires decent water - a long enough run-up to achieve high speeds, and pretty flat water. Rough water can slow even a fast boat by many mph.



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[martin]

Around 38000rpm at the prop is what i worked with on calcs, 44000rpm unloaded x 85% efficiency gave 37400rpm less 20% slip.

[Mtwinste]

The boat was very dry at 63mph. Nearly the Entire sponson was out of the water at top speed only the rear most 4 inches or so was in the water. I will post some videos this weekend with a M445.

[Mtwinste]

Should the shaft be angled any differently? I know it's not flush with table. This is where I had it on the 63mph run. I'll move it flush today.




Sent from my iPhone

[Mtwinste]

[lenny]

The boat should be on a level surface and the strut should be level with boat and surface.
Loosen collet at motor make shore prop and flex shaft turn free and greacs it !
Than if its running wet,
Move the cells to the stern of boat some 1/2 at time and mark it so you know where it was,
Than see if it runs dryer or looser and check speeds and temps.

PS
Did my parts shipped yet ?

[Fluid]

If the boat is running as described then it is plenty free and does not need further adjustment until the speed increases. As I stated above, you won't go faster without more pitch value. Using your values in my calculator you should be at 61.5 mph - pretty close. Toss that little prop and put on a man's prop!

Seriously, try an x642 and you should be around 70 mph. An M645 should put you close to 75 and an x648 close to 80 if the boat is still trimmed correctly and can stay on the water.




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[Make-a-Wake]

I have never ran a 1200kv motor on 10s, but for a 4082 with that voltage 645's and 648's seem like ALOT of prop.................possibility of pulling huge amperage and damaging the ESC................or could i be wrong. Just seems like alot.

[Mtwinste]

Lenny shipped yesterday.

[lenny]

Ok thanks for info.

[Fluid]

...a 4082 with that voltage 645's and 648's seem like ALOT of prop...

It is capable of pulling a lot of amps, but if the OP wants 80+ mph that's what he'll need. High speeds simply require risk - burning down, crashing, sinking - and it is up to him to assume that risk. While most posters here seem to assume it is easy to get to these speeds with cats and hydros, that just isn't so. But several here have posted using ~1500 Kv 4082s on 9S/10S with 3" pitch props without burning down, it depends on how he runs it. This is clearly a SAW-only setup, not for five minutes of constant running.


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[Mtwinste]

X645. 140degrees on motor.

I feel 80 is soon