Boat turning problem

[Ken_NJ]

This is a very odd problem I'm having. I have this Dumas Scarab I built back in 2014. It always ran with no problems. Recently I started having a problem with it turning. I'm using a Hitec DX4C radio with a Hitec SR410 receiver and Hitec servo. The boat would run fine with the normal turning radius, then all of a sudden the turning radius was almost nonexistent. Running at slow speed the boat would turn in a tight circle like it usual did. Sometimes when running at speed the turning radius would be fine then all of a sudden it was making a very wide arc. If I stopped the boat then startup again, the turning went back to normal for a short time. I swapped out the receiver and servo and the problem still occurs. The rudder moves freely. The only questionable thing at this point is the transmitter. Anyone experience something like this? Any idea what's going on here or what I can try to do?

https://forums.offshoreelectrics.com...ghlight=ken_nj

[MarkF]

Sounds like your receiver battery is going bad. What are you using?

[Ken_NJ]

A 2000ma Nimh pack. I just checked it, batteries are at 5.21 volts after running the boat.

[rol243]

replace the rudder servo.

[Fluid]

I too think the issue could be the rudder servo. Exactly what servo does the OP have in the boat? I had a steering problem in one of my big 10S boats using a quarter analog scale servo. I replaced the servo with an identical one but the problem persisted. I replaced the servo with a digital model and the problem disappeared. The analog servo just lacked enough centering power.

Other things to check include the condition of the plugs - the servo and the pack. And just because a pack shows decent resting voltage doesn’t mean it does so under a load. There isn’t much else.


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[MarkF]

Your Nimh pack could cause what your seeing but I would change your servo again with a new one and if that fails then change your receiver pack.

[dasboata]

Batteries or servo my money is on the batteries

[Ken_NJ]

The original servo is a Hitec HS-485HB which has karbonite gears. The second servo I tried is an HS-322HD which also has karbonite gears. Already replaced the receiver. Next time out I'll try another battery pack.

https://hitecrcd.com/products/servos/sport-servos/analog-sport-servos/hs-322hd/product

https://servodatabase.com/servo/hitec/hs-485hb

[bogieboy]

i would run a servo with substantially more torque than any of those.... even my 23" vector i run around 200 oz-in. servo for steering... also ditch the NiMH reciever pack. i have good luck with my LiFe reciever pack in my Dumas DV60 running 2 300oz-in servos, one for throttle and one for steering.

these are the servos i run in my Dumas... https://www.amazon.com/gp/product/B076CNKQX4

more than enough to turn a 46" gas powered boat...

[Jesse J]

How to check the turning issue:
Power on everything as if you were going to toss it in the water, except don’t tape it up and you don’t need the esc powered up (safer for this experiment).

On the bench, try turning the rudder with your hand, it should be hard to turn. Watch your linkage, does it bend? If so, that could be it. Does it push or pull to turn right? I almost always have my big boats pull to turn right.

Next, if that test passes, try turning the servo with the radio and add resistance with the hand again, if the rudder is easily returned to straight without any mechanical issues, then a stronger servo, >300oz. If the linkage bends, add a carbon fiber tube around your linkage rod, or replace with thicker piano wire.

Please update with results of recommended experiments.
Jesse

[Fluid]

I too believe the servos are inadequate. I use stronger servos than those in my little P-powered boats. Gas boaters who run boats the size of the OP’s run a minimum 180 oz-in at 6.0 volts. My T boats ran perfectly with servos producing over 250 oz-in at 6.0 volts. Get more servo!



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[Ken_NJ]

Found the problem. On the bench I held the servo arm in place and applied force to the rudder like Jesse J said. The push rod was solid and didn't see anything out of the ordinary. I removed the servo linkage to inspect it. Found a hairline crack in it on the side I couldn't see. Looks like the pressure against it while running the boat was enough to let it slip out while in a turn. Still seemed solid on the bench though. Will replace it and run it again, but not till the weekend.

[bogieboy]

you will still have the problem if you are trying to run a 55" dumas scarab on a 50-60 oz in servo... the servo simply cant hold that much rudder... shoot, my first throttle servo in my DV60 couldnt even hold the throttle open (foot long cable in teflon sleeve on a short arm on the servo, and stock mounting point for the engine on the carb, and that was a 195oz in analog servo. go to a 300oz digital... it is well worth it....

[Ken_NJ]

This is not the 55 inch Dumas. Its the 45 inch hull.

[bogieboy]

then we are in the same "boat" so to speak... a 60-80oz servo is nowhere near enough even for a 45". like i said before, my 45" dumas is running a 300oz servo for steering duty...

also, if you read the zippkits supersport 46" shallow v boat manual, they recommend at least a 150oz servo... http://zippkits.com/ssman.pdf