Just when you thought it was safe to go back in the water!

[seahorse]

way to go BD !!!

way to go BD !!! slicker than clown snot !

[petn7]

Great pictures, especially the second

Great pictures, especially the second one.

Sent you a PM, Dave.

[bigdave]

Well I will have some

Well I will have some very short video of the WaterSlider at the regatta.
The camera man was trying to take underwater video instead of above the water video.
I should have been watching him instead of the sub. I don't know what he was thinking.
He only got a few seconds underwater and none of the jumping out of the water shots. (Cheap Help!!)
Then he was able to capture the rescue by Kerry Addington.
Go figure!!
The torque was so great on the hull that it spun the seal off the sealing surface and opened up the hull to the pond.
It left a very impressive bubble trail as it sunk to the bottom. I guess I will need a sealing tape backup like I use on the Dolphin boat. It was really hauling a-- before it sunk.
It was leaping out of the water like a fish. I think some video was gotten by others. I saw some of the Saturday video done in slow motion that looked very cool!!
I will post my video in a few minutes. BD.

[bigdave]

I have lots of footage

I have lots of footage of the WaterSlider running at the Subron-4 regatta. This is the first short video I put together. You have to look close. She is a handfull.
It is still a prototype and needs more adjustments. I have some ideas.
Most all of the jumps are standing start jumps.
No speed is required to climb right out of the water.
I could not give her full power as the sub started to cork screw.
I will post some more video when I can. BD.

[ronnie b]

looks good do you plan

looks good do you plan on making models for sale or is this just a one of a kind thing

Ron

[bigdave]

It all depends if I

It all depends if I can get the beast dialed in.
I have molds and can make more but it is just to much of a handful now.
But she sure it fun!!! BD.

[Wheelerdealer]

Hi Dave, can I ask

Hi Dave, can I ask what prop/motor/ battery combo you are using? I am buiilding a speedster myself and am looking to get similar performance to yours. I have only tested her in the bath (doesn't seem as powerfull as yours) and with a 1800kv motor and a 32mm 2 blade prop, it pulls 27Amps off a 11.1v battery.

[bigdave]

Hi Ramesh,
Right now I

Hi Ramesh,
Right now I am running a Venom Fireball 21T brushed 500 sized motor with a 40MM two blade hydro type prop. I have a 2000MA nicad battery and a Astroflight 40A ESC. I am going to be testing a smaller prop as I am getting to much torque roll. BD.

[Guest]

Have you seen what they

Have you seen what they do in Germany to counter torque roll?

They use two levellers mounted at angles, and use independent control of the hydrovanes to counter the prop torque.

Have a look here to see how it is set-up with Norberts Dolphin-

http://www.modelluboot.de/Anleitungen/A ... _80429.pdf

[bigdave]

Thanks Andy. I will check

Thanks Andy. I will check this out. BD.
BTW- I am moving all the new WaterSlider videos to the video section.

[Guest]

Hi Dave, can I ask

Hi Dave, can I ask what prop/motor/ battery combo you are using? I am buiilding a speedster myself and am looking to get similar performance to yours. I have only tested her in the bath (doesn't seem as powerfull as yours) and with a 1800kv motor and a 32mm 2 blade prop, it pulls 27Amps off a 11.1v battery.

I wonder if you're over revving the prop? There is a window of ideal RPM for a prop, assuming the pitch of your prop is somewhere between 1.2-1.4 times the diameter I'd suggest ideal RPM is about 9-10000RPM, beyond that the prop is just slipping in the water.

It's a bit like putting a V8 through mini wheels- the extra power just results in wheelspin. The car needs wider wheels to get the power down.

Therefore I'd look towards monitoring what the RPM of the motor is when under load. If it's significantly higher than the figure I've put down, then you may need to fit a lower revving motor.

The way to higher performance is to fit the largest prop you can get away with without inducing torque roll, or applying some active compensation.

Anyway here is a nomogram from a nice little (sadly out of print) book I own which should put you in the right ballpark. You need to know the pitch in inches of your prop, most racing props are between 1.2-1.4 times the diameter of the prop. You should aim for about 20% slip, and no more than 30% slip , so line 20% up with your propeller pitch and see what shaft RPM is required.

[Wheelerdealer]

Useful diagram Andy, unfortunately I

Useful diagram Andy, unfortunately I don't know the pitch of any of the props I have, simply descriped as 2 blade racing props in a variety of diameters. My Subdog (Subpirate!) comes in at a full 3kg with a stack of lead right at bottom so it doesn't know the meaning of torque roll! I fitted a 35mm plastic prop which has seems to have a significantly greater blade area than my 2 blade 32mm prop, and that pulls all of nearly 50 amps in the bath (that with me holding it down). Thats more power than my motor is rated at. I cant get my brain around the math at the moment but does this mean it will pull less amps when under way. I can only fit my Watts meter in there when the front of the sub is open so I am unable to get any dynamic amp readings. Also as I throttle up the thrust does seem almost proportional , with no obvious letting up of action as I reach maximum revs.

Compared to BD Waterslider, mine looks to have a larger diameter and and seems longer. So this will mean a greater wetted surface area so more power needed to achieve the same under water speed. Also the weight will limit any vertical out of water excursions. So whilst I may be able to get close to BD's underwater speed, I fear I may need rather more juice to get airbourne. It would be intersting to hear how much BD sub weighs and its dimensions.

[Guest]

To calculate pitch on an

To calculate pitch on an unknown prop use the formulas shown here-



An electric motor will take as much current as you can supply it with, until it destroys itself. the wattage figure given with the motor is probably just a nominal figure.
You could invest in a Eagle tree elogger, I believe on-board recording of voltage, current and RPM is the only true way to assess what really works.

[bigdave]

I will weigh the Waterslider

I will weigh the Waterslider when I am back in the dockyard and get the length and diameter. BD.

[fgroza]

BD,
You might try a X427

BD,
You might try a X427 Octura prop on that motor. I run a Magnetic Mayhem-22 double turn- on 7 cells in a runabout and it moves. The prop is 27mm dia. and lets the motor unwind.
Just a thought.
Frank