prop walk

[Gary]

Can anyone tell me how to keep a 33 inch hydro from prop walking to the left under excelleration . A smaller prop will not do it but speed goes away. A shallow prop will not do it but again loss of speed. If i could figure out how to make it work with a deep strut i think the boat will really fly because it pulls really hard before it starts to walk. Any ideas/ Thanks

[detox]

Try to fix problem in the following order.

1. Strut may have too much upward angle pushing stern out of water. Try setting your strut bottom level with setup board.

2. Try moving your center of cravity a little more rearward toward stern

3. If that does not work try bending your prop tips

Read this post by Raptor347:

"Another possibility is the prop stages as it comes up to speed. What I mean is at some point during acceleration the prop starts to climb out of the water. When it does that the sponson AOA it decreased, cutting out some of the compression lift. At the same time it increases the downforce produced by the tub (or neutralizes some of the lift). An extreme indication that this is happening is the boat will accelerate and all of a sudden the back end starts to hop (prop blows out).

One way of reducing that tendancy to climb out of the water is to add some cup to the tips. Look at the trailing edges of the two props in the picture. Notice how the outer 1/3 is bent/curved forward. That allows the blade to take a scooping bite of the water (sorry, best description I could come up with) that counteracts that lifting tendancy. Where you start that bend is how you adjust how high the prop will climb. You can actually over do it to the point it will draw the back end down rather than lifting.

Don't know if that helps, but it's a little more info for you.
BTW, that full bladed V935 is the prop that pushed my O hydro to a one way of 100.8mph on 8 NiMH's at the '06 LA SAWs."
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[detox]

A slightly deeper rudder will help it stay strait under acceleration. You may also want to sharpen the bottom of rudder to prevent lift.

Practice, Practice, Practice...............

[Gary]

Will this slow the boat down or change the load on the motor? I always used the shortest rudder possible to reduce drag but i will try a deeper one. ......I dont think it will do much because its all in the prop i think. Only because it becomes very violent and trys to excellerate very hard. Even if i excellerate to top speed as slow as possible it will eventually start getting crazy.

[Diegoboy]

I would offset the driveline to the right!

[detox]

. I am sure a slightly longer rudder will cause SLIGHTLYmore drag. Once you get the hopping or extra lifting cured the boat should run strait. So ORIGINAL rudder should be OK...just sharpen the bottom.

[detox]

This article may help some:
http://www.offshoreelectrics.com/inf...s-and-more.php

[Gary]

I tried off setting to the right but then it did some really crazy crashing LOL One thing i forgot was when the water has a slight breeze and creates some ripples it will definetly help the boat and its much more stable. ...im bending the prop tips right now!!!!

[Flyguy55]

I'm assuming the boat is turning right , the stern is going left ?
A couple other things to check.
Is your prop razor sharp ? A dull prop will cause prop walk .
Have you clamped a straight edge on your turn fin to be sure its straight ? eyeball is not good enough.

[Gary]

I have tried 3 turn fins and customized two.I always made sure they are straight. I have 9 props in my collection that i have tried and yes the prop i have now is very sharp................Would it be unrealistic to have both batteries on the left side to compensate for the lift/walk to the side?................ The batteries are 6.5 inches long and are 3 inches past the end of the sponson forward,this is where it ballances 50/50. I have moved them around but not drasticly. What do you think.......Where SHOULD they be? Detox the article was great and i am going to try a few of the ideas listed !!!
ps... I talked about this in other threads but did not mention that the boat is a dream at 50 mph. Throw in the big boy voltage and it goes 60 mph ...an out of shape god save it 60 but 60 so the only change is prop speed, dont know if that helps.

[Gary]

Ok ..moved batts up 2 inches.....put deeper rudder on and sharpened bottom to razer edge .....cleaned up prop even more so it almost cuts paper and put some cup on tips. Also changed turn fin to short straight style.I will have to wait for good weather to try. Do you think putting batts on left side will help keep sponson down?

[Flyguy55]

You have changed a lot of things. if its better you won't know what helped and what didn't.

Torque effect will try to lift the left sponson. If it still goes right , try moving the batteries. :-)

[Gary]

I know but i have been fighting this for a long time and changed so much i figured why not make some drastic improvments??? and see what happens.

[detox]

Do you mind stating what prop you are currently using? It sounds like your using a big lifter prop. What Motor/ESC/battery combo are you using? What hull are you using?

There are a few really smart guys on the forum that know how to set up a hydro...you may want to send them a Private Message asking questions. It seems that lots of their setup tricks and prop knowledge is very carefully guarded.

You may want to send Darin Jordan a PM.

[Gary]

Thanks for the input Detox. Its probably better that i dont since i really dont know them personally. But as far as my combination it is a Miss Vegas hull that the bottom has been modded buy removing the bottom hump and making it flat. It has a Hydra 240 and a Neu 1521 1.5d motor. I run a M545 ...this prop has performed the best out of x442,x445 , x447, all of the M props that octura offers and a few others.I also run two 11.1 batts. I know the rpm is up there but if i can get the boat to settle down it will go faster than its 60.8 best. Its almost like there is a governer on it .....I can turn 60mph runs all day untill all my batteries are done. {I have 5 sets} LOL