Prop torque

[scuba_mc]

I'm looking for my first DPV. I do a lot of shore diving and I ideally want something light (under 35lbs) but still with a decent run time. However was reading about prop torque effects when using smaller DPV's and had some questions:

Is there a general relation with the size of a DPV and torque effect? Is it accepted that a short or narrow or light DPV will be harder to steer in a straight line due to torque effect?

If so, can manufacturers offset this by clever weighting or can this even be done as a diy job? Does the choice of a small, light DPV create a compromise with comfort on long dives due to "counter-torque" steering?

Thanks

 

[cool_hardware52]

I'm looking for my first DPV. I do a lot of shore diving and I ideally want something light (under 35lbs) but still with a decent run time. However was reading about prop torque effects when using smaller DPV's and had some questions:

Is there a general relation with the size of a DPV and torque effect? Is it accepted that a short or narrow or light DPV will be harder to steer in a straight line due to torque effect?

If so, can manufacturers offset this by clever weighting or can this even be done as a diy job? Does the choice of a small, light DPV create a compromise with comfort on long dives due to "counter-torque" steering?

Thanks

If you are walking in to the water off the beach with a single tank torque is the last thing I'd worry about. You don't have enough gas to scooter far enough for "torque" to be a big worry.

Tobin

 

[Jon Nellis]

Is there a general relation with the size of a DPV and torque effect?

No, the torque generated by a DPV is basically related to thrust and propeller efficiency. The faster you go or the less efficient your propeller is, the more torque you will experience.

Is it accepted that a short or narrow or light DPV will be harder to steer in a straight line due to torque effect?

No, light scooters are more susceptible to minor directional control inputs than heavier scooters simply due to their weight. It takes less force to change the direction of a lighter scooter than a heavy one. Simple physics, F=MA. It is easier to make a light scooter go straight than it is to make a heavy scooter turn quickly. You just have to pay attention.

If so, can manufacturers offset this by clever weighting or can this even be done as a diy job?

Many old single speed, lead acid scooters have the batteries off center to help reduce the toque felt by the diver. We do this with the Genesis 600 and 1200 batteries as well, but being both lighter weight and higher thrust, it cannot completely compensate for the propeller torque at high thrust.

Does the choice of a small, light DPV create a compromise with comfort on long dives due to "counter-torque" steering?

No, see question #1. As an example, the Genesis 600, 1200 and 1500 all require about the same torque at the same power level, even though the weights go from 33, to 44 and 49lbs. I'll do a 90 minute dive, on the trigger the entire time and the torque is not really noticeable at normal speeds. At high speeds the torque becomes noticeable, along with the drag from the water and your mask being smashed into you face. There are other things beside torque that you should worry about at high speed and you will not likely be staying at that speed the entire time.

Cheers,
Jon