!/8 Scale Rudder Placmnet

[Tom G]

Rudder placement.
On my RCBc SG118H 1993 Miss Budweiser T-3 hull in one of Steve's pic's the rudder is located on the same side of the hull as the turn fin (right side)

On the full size Miss Bud we ran the rudder on the opposite rudder (right side) of the hull from the turn fin on the left side

Most of the 1/8 scale hulls I see around here the have the rudder on the left side (opposite to the turn fin )
Which has the best turning performance (less prone to spinning out ) rudder on left or right

[CraigP]

Good results are obtained with both approaches but are slightly different approaches to boat setup. I go with the left, because I want my hydro to have a drifting attitude in the corners. Some call it a crab turn. I think the physics vectors makes more sense as well. So it’s up to your vision on how you want to see the boat run. Note on my Mono, it works very well on the right. On my Cat, the left. I come from full scale hydros too, so I have a natural bias to opposite side setup.

[Fluid]

It used to be normal to place the rudder on the opposite side of the R/C hydro hull from the turn fin. When the rudder is moved for a left turn (for scale boats) it generates a lifting force which loads the turn fin, helping to keep it planted. That’s the good part. The bad part is this makes the hull very sensitive to right turn input, often resulting in a spin out or flip. During a race right turns can be necessary to avoid a slow or dead boat, or as a course correction to stay on the oval. A flip means a DNF, worse than finishing in last place.

The use of hooked turn fins reduces the advantage of an opposite side rudder. It holds the left sponson down well in left turns (it also complicates tuning by adding an additional adjustment). An additional advantage is a marked reduction in right input sensitivity, so the boat is more likely to finish a heat particularly when driven by a less experienced driver. Many consider this a good reason for mounting the rudder on the same side as the turn fin. A great many drivers have won a lot of championships with this setup.

All that said, if you are not racing and are not an experienced hydro driver or are using a straight fin then it would be best to mount the rudder on the opposite side. It could be a matter of personal preference.


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[CraigP]

That makes perfect sense and explains why the curved fin didn’t work as well as an angled, straight turn fin for me.

[CraigP]

I just re-read Fluid’s response and I have a question. You seem to indicate that left hand turns are the norm and right hand turns may be necessary, under actual conditions. Are your courses set up for counter-clockwise running? Are there clubs or regions that run differently to each other? I have seen videos of rc boats running left, but they were scale boats and I just thought they were running them as per their full sized counter parts. Just wanting to know...

[CraigP]

I think I got it... Viewing the rudder from the top, you turn it to the left, so the edge in the southern hemisphere swings right. It is inverted due to the rudder edge placement... Never mind...

[worthing3104]

Just sayin, Unless something has changed. Clockwise racing, and I've always run my rudders on the same side as my turnfin (right) with no issues ever. I like the feel as if it's on a rail.

[worthing3104]

Here's a couple20171126_210054.jpg pics of my Winston Eagle I'm almost done with