Twin 6S rigger - Done!

[mm123521]

Finally done -- It will hit the water in another 3 hours.

Build thread: http://forums.offshoreelectrics.com/...40-inch-rigger

6S1P 5300 MAH Gens Ace batteries
CC2018 Motors (1800KV) spinning at 40000 RPM
Wire drive with 447 props.
44 inches long, 26 inch wide.
Weighs 13.5 pounds RTR
Finish is clear polyeurothane over plywood.

I hope this thing works? With a homemade hull, homemade turnfin, etc. -- it is highly probable that it will blow off or suck down or something will go wrong.
If the hull works correctly it may go between 80 and 90 MPH.
The no slip speed is 98 MPH
The 15% slip speed is 83 MPH
The 10% slip speed is 88 MPH

Mark
Homemade: turnfin, motor mounts, struts, wire drive, water pick up's.
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[mm123521]

Pictures:

I believe these motors are rated at 3500 Watts - Thats 9 horsepower in a 13.5 pound boat!

Check out my hull inspector!


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[mm123521]

More Pictures

Check out the turn fin, it's home made from polished stainless steel plate.
It is non-adjustable. If it is set on the wrong angle, it can only be bent.
It was precision aligned and precision bent, so I am hoping it works.
If you look real close, you can see horizonal scribe lines - those are my bend lines.
The boat was setup on a 3/4 inch thick, flat, alluninum plate and the lines were scribed from the surface of the plate, so I know they are perfectly parallel to the hull.

If it doesnt work, I have a second turn fin blank ready to bend.

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[Rumdog]

Let her rip! Gimme some vid!

[Jedi Master]

Wow, this should be an awesome first run.....

[mm123521]

Rumdog, & Jedi,
First run went good and bad.

BAD,
I wasnt paying attention and a cooling hose was up aganst the coupler. It rubbed through and flooded the hull.
Darn it -- an amateurs mistake!

GOOD,
It ran fast, straight, and flat -- no hopping, no blow overs, no flips.
I am used to running a 71 MPH SprintCat, and this rigger scares me, it's so fast.
When you get off the throttle, it coasts forever, before it drops off plane.
No GPS on this run, but I am sure its in the high 80's.
Acceleration is spectacular!


The water was half way up on the motors for 30 minutes -- how do I dry out the motors?
Electronics were mounted high and seem to be OK.

Mark

[Jedi Master]

Sounds like it went well, except for the mishap. I've flooded a lehner motor before. Didn't let it dry out completely, but got as much of the water out as I could before giving it a good blast with silicon spray. Then I ran it slowly to clear the rest of the water with more silicon sprayed in to keep the parts coated. I'm no expert, and my method may not be the best but I figured it would not do the motor any good if I let it dry out on its own. I replaced the bearings and it ran like a dream.

Would love to see some video!!!

[v-spec]

I'd just spray the motors down with corrosion x or similar. Wish you had a video!

[mm123521]

I'll get this thing dried out and make a video run tomorrow, after work.

Mark

[Fluid]

Yes, shake out as much water as possible, then FLOOD the inside with CorrosionX - or even WD-40 - until it pours out the screw holes. Corrosion inside the motor can lead to motor failure if the bearings seize or chinks of rust get thrown into the windings. A few $$$ investment in water displacement chemicals is well worth it.

A suggestion - paint the rigger a bright color so it is easier to see. I ran SAW riggers with natural finish like yours, but it is too easy to lose sight of a fast boat under many light conditions. Bright yellow, orange or even white will help to take the "fear factor" down a notch.

You do realize that you don't have near enough prop pitch on that thing don't you? Try some x648s or Prather 235s....

.

[mm123521]

Fluid,

Yes that has to be the conclusion. --Bigger props!
Step one was to see if the hull was balanced , both hydrodynamicaly and aerodynamicaly.

It's hard to believe that a rigger runs correctly on the first time out??!!
I did not expect this!
This thing was built with dial calipers, toolmakers squares, etc. - a precision build.
The wood components were all machined out perfectly square, not just cut on a saw.

It sticks to the water like glue and there is plenty of excess horsepower, so bigger props are next.

The fear factor comes from running out of lake too quickly!

The instructions for ZipKits riggers (my sponsons are modified from a zipKit 45 rigger) specify a slight sponson toe-in, but I set this one up with zero toe-in?
What does toe-in do for you??

Joe from ZipKits, said his riggers should stick to the water at over 100 MPH.

On the first run, the boat would not turn. There was only an inch of rudder in the water.
Next run, I put a longer rudder on (2.5 inches in the water) and now it will make a 175 foot diameter turn at 1/2 throttle.
The CG is only 1.5 inches behind the turnfin center. I think i need to move the aft battery back to increase this distance and help the turning.
The next step is to get rid of the counter rotating props as you sugested.

Mark

[LarrysDrifter]

You might want to try ABC 1816-3 counter rotating props. They are 45mm x 1.6 pitch. My cat, which I know isn't a rigger, pick up A LOT of speed over X447's.

[mm123521]

LarrysDrifter,

I was looking at exactly that prop a few days ago.
It retains the advantages of counter rotating props.
They are kinda expensive, I think they are about $30 each.

Larry; how much speed do you think you got?
What motors are you using? KV and # of cells?

2.88 inch pitch @ 40,000 RPM = 109 MPH -- no slip
Thats 92 MPH @ 15% slip
And 98 MPH @ 10% slip

Hummm -- bumping up aganst 100 MPH!!!

Thanks!
Mark

[Fluid]

Twin riggers do not like counter rotating props. This has been well known for decades - no one races twin riggers with CR props. These boats just will not turn well at all with CR props. Yes you'll have some prop walk with LH props, but you will be able to turn. 175-foot diameter turns is not even turning IMO.

A more real-world estimate of speeds with 2.8" pitch props - assuming you have a long enough straight - is closer to 90 mph. Still hauling. More speed needs more pitch. Don't be frightened...


.

[mm123521]

Jedi,

I had a can of "Liquid Wrench" Silicone spray that had a damaged spray nozzle, so I drained out the pressure and emptied the liquid into a plastic container. I soaked the motors in the silicone liquid for 20 minutes. Now the motors are hanging by the wires, draining.
Tomorrow, I'll reassemble the motors on their mounts and cooling jackets.

Thanks!
Mark