What stops chine walking

[chrispycontrol]

My revolt setup.
leopard 3674 2200 kv
SK 180a esc
LVC 3.4
Trim tabs, inside and outside, both sides set about even with hull ( useing a straight edge on bottom of hull they almost touch.
Turn fins half way and angled back

Steering trim set at 0 on my futaba 3pl
rudder is perpendicular to transom

Prop is x442, sharpened and ballanced, could probably be worked more but its pretty sharp, ballances on my grimracer prop ballancer.

It walks pretty bad at WoT with 0 steering input, when I give it a bit of right or left steering to go in an oval the walk goes away and runs great, I can go full throttle but if I go to 0 steering it walks vilently and will crash.

Strut is angled up a bit, runs on the back 3-4 inched of the hull
hull is scuffed.
Useing a gens ace 4s 5000mah 40c lipo set all the way back just about touching the motor.

Other than the walk at neutral steering she runs good.
Would like to get rid of the walk so I can run her straight with no steering without it walking.
The walk is better if the lake is glass flat, but its still there.
Need more help to stop it, I have tried adjusting the trim tabs and turn fins, but not sure if I am doing it correctly to get rid of the walk.

Can anyone give me some advise?

[Fluid]

It walks because too little of the hull is in the water. It is trying to balance on the sharp edge of the keel, and any small disturbance (waves, etc) will start the oscillations. Raising the strut (not the angle) will settle the boat down in the water a bit, this usually eliminated walking.

The following was posted by John Finch (a noted nitro guy who recently started FE) several years ago and is very valuable. Note that this was for a much larger boat than the Revolt so the measurements John uses will be different.

"The problem is in your strut location. The further back the prop the higher it must be out of the water to let the transom of the boat settle into the water for control. So raise the strut and prop. If you shorten the strut an inch that will help too, but cut an inch off the trim tabs too. If the prop is off to the right or left of centerline the boat will be lifted on that side as well, and that starts to control the boat half way down the straightaway when the boat is easily influenced by the lift of the prop. At slower speeds and acceleration you don't see the problem because the boat is not yet balancing on the prop. The turn fins are not the problem because you don't see the problem when accelerating. The centerline of the strut should be about 5/8ths of an inch above the transom vee when the prop is about 3 to 4 inches from the transom to get good control. It is imperative that the prop be centered unless the rudder causes lift when the boat airs out. If the rudder lifts the right side of the boat then you can shift the prop to the left of centerline to compensate for rudder lift. Deeper rudders cause more lift. Keep in mind all these little things don't have much effect at average speeds, but if you get the boat aired out and going fast they then become your tuning devices. John Finch"


,

[ray schrauwen]

Thanks Fluid. Always good reading...

[rickwess]

Yes great info. The Revolt has an offset prop so balancing on the prop will be almost impossible.

Chris. What's your speed at WOT?

[chrispycontrol]

Thanks, just to clarify, Raising the strut? If I loosen the nut holding the strut to the strut brace I can push it up or down then retighten the nut. currently I have it pushed up a bit, would making it straight or even slightly down acomplish this?
Or is raising the strut actually removing the tubing and redrilling it higher? and making it higher than its current position?
From center of the tube to bottom of the V it looks to be about 3/8 of an inch on the revolt
A little confused, I dont want to have to drill and repair holes if I don't need to

[Mike Caruso]

Is your rudder flat on the bottom? If so just radius it. Yes stuffing box is @ .400" no up or down angle.

[chrispycontrol]

Never gpsed it, if I had to guess its about 45mph. I should get a gps, but my RC budget was cut by the boss :( Needed a new washer and dryer.
Yes my rudder is flat, I was going to radius it, but never got around to it
Got to run it last night, I think I had the angle up to much, I lowered it, too much at first, took a few times to get it right, its amazing how such a small adjustment can make a huge difference. I tend to over adjust
Taking it to the lake today, going to try and get it perfect

[lenny]

Also some added weight will help to sometimes,
To get it to stay planted and stable to a point.
Oh and you should try a three bladed prop,
I use a x440/3 on my modded Rio.
The three blade make a mono run a lot smoother and have a lot less torque roll for me,
I am using a x447/3 on my Pursuit now for testing.

[chrispycontrol]

I put the strut and trim tabs back to neutral yesterday, ran 2 packs thru it making adustments very small, made a sticker with my ptouch labler and put it on the strut brace, with lines so I can guage my adjustments better
need to find that spot where its not running too wet but not walking.
ATM it is 1.5mm angled up from straight, it is very stable, but running wet, trim tabs are at neutral, I think 1-1.5mm more and it might be purrrfect.
And I have the rudder at work today, going to round it out, when I round it out, do I want to sharpen it all the way to the back edge?

ANother question regarding props.
I have 1 cnc prop, I believe its from OSE, I was going to pick up a 3blade cnc prop, I wanted to get the equivelent to maybe an m545, if the pitch in a 2 blade is say 2.65, would a 3 blade with the same pitch produce the same speed?

Would there be a big difference in speed or performance between a cnc and say a copper berilium prop? grim or octura?
the CNC props are lighter by far, spinning a lighter prop better for run time? better for electronics?
S&B props hurts my hands

[Mike Caruso]

No squared off and sharp corners.

[chrispycontrol]

You wouldnt happen to have a pic of a radiused revolt rudder would ya?

NM saw the picture of yours in your profile, I got the jist now

[Mike Caruso]

You wouldnt happen to have a pic of a radiused revolt rudder would ya?

NM saw the picture of yours in your profile, I got the jist now

Look at Pre-preg carbon self righting Titan 29 build #79