Kt value in FE calc ?

[Xfactor]

you can make motors have the same wattage output using different voltage and amperage settings but remember each motor has it own characteristics meaning that one may do fine with a draw of 100 amps while that may burn another motor up.As far as mass to me that obvious physics. More mass can push a larger boat. ex.Two motors same rpm different masses for one the heavier took more power to get it to the same rpm then once its there it has more energy than the lighter motor.Larger displacement=more torque.Duh

[Xfactor]

he did mention horsepower relative to boat size... is there a way to calc horsepower from the data fe calc provides? and if so .. is there a chart of HP vs. Boat size or weight...

ozzie..

Divide you watts by 745 that will give you appox. hp

[ReddyWatts]

Divide you watts by 745 that will give you appox. hp

then mutliply by the motors effeciency. Usually between .75 to .95.

[Xfactor]

I think hp to weight ratio is the key. I may get ran down for this statement. Forget HP its whats left over after the work is done. The torque is whats truly relevant. Does anyone concur?

[sporthydrofan]

I think hp to weight ratio is the key. I may get ran down for this statement. Forget HP its whats left over after the work is done. The torque is whats truly relevant. Does anyone concur?

so according to you the torque is how you relate to the boat weight .. so generally speaking how much torque or HP or watts per Lb do you need to get 50+ speeds and keep a cool setup asuming the torque produced is within the esc & motor amp draw rating.. I can figure everything else out... motor esc prop voltage combo etc..

1 other question that i just thought of on a hydro or cat at high speed the hulls get lighter due to lift so technically at wot straights your not pushing a 6lb boat any more rather a 3.5lb boat due to lift... not sure if that is accurate just throwing numbers out there.

[ozzie-crawl]

as far as i see your rite, in full scale tunnels,cats at top speed the lift can be as great as 80-90 percent of the hull weight,this is there design, at slower speeds the lift may only be 30-40%
would be the same with our models.

[Xfactor]

That is your slip. I think that is included in the algorithm in the fe calc program code. Different hulls have different slip coefficients.

[Xfactor]

The weight is still there but less drag so less energy is needed for acceleration to occur.

[Xfactor]

You have to lift a 6 pound boat period. Do not you have to keep going a certain speed to keep the boat up on step? Then to me the energy to lift the 6 pound boat out of the water is always present. The drag is what is different between a wet and dry running boat.Not to mention the motor unloading more easily due to less prop being in the water.

[m4a1usr]

1 other question that i just thought of on a hydro or cat at high speed the hulls get lighter due to lift so technically at wot straights your not pushing a 6lb boat any more rather a 3.5lb boat due to lift... not sure if that is accurate just throwing numbers out there.

Gravity is why the hull weighs 6 lbs. It doesnt matter if its on the water or 6 inches above it. It will always weigh 6 lbs. I think your comment was more about friction or drag. That 6 lb boat will require less force to go forward as the friction or contact with the water continous to decrease.

John

[Xfactor]

Thanks I see someones on the same page.