Is an inline rudder faster than an offset rudder?

[sundog]

These aren't sailboats! Put your hand in the propwash of a boat and then tell me it does not push back.
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Jay, I think you know what I was trying to convey with the sailboat example. But thanks for your input, that helps to clarify things.

[sundog]

Mtn Home?

Close enough! (Harriet) Oops, typo - I meant 'to play in' but that works too.

[jevmax]

No, I don't believe that holds up. That is what Rumdog was alluding to in a different post. If you are standing on the dock and push on a sailboats mast, the boat will move. But if you are standing on the sailboat and push on the mast, nothing will happen. Propwash pushing on itself (rudder is connected to the prop via a strudder) would cancel out any such forces.

It's simple physics. Keep anything attached to the hull out of the prop wash.

[jevmax]

To help visualize the concept, imagine if a rudder directly behind the prop was 4" wide. That would completely block the prop wash, and the boat wouldn't move at all! Now.....how wide do you want the rudder to be, and where should it be mounted? I hope that helps.

[Flying Scotsman]

That is a rude reply and I am an old fart also and I appreciate the kowledge of seasoned boaters!! as I learn the nuances of FE boating

Douggie

Jay, I think you know what I was trying to convey with the sailboat example. But thanks for your input, that helps to clarify things. Why you have to be such an old fart about it is beyond me. I guess it's no fun anymore when you've done everything! My condolences.

[sundog]

To help visualize the concept, imagine if a rudder directly behind the prop was 4" wide. That would completely block the prop wash, and the boat wouldn't move at all! Now.....how wide do you want the rudder to be, and where should it be mounted? I hope that helps.

Thanks for the analogy - yes, that is a good way to explain it. That makes sense....it's all becoming so clear to me now!

That is a rude reply and I am an old fart also and I appreciate the kowledge of seasoned boaters!! as I learn the nuances of FE boating

Douggie

Whoops, busted. My sincere apologies to all other old farts on this forum. You know who you are.

[Steven Vaccaro]

So if I ran a cat at 65mph last week with an inline rudder. How much faster could I have gone with a offset rudder?

Here is the info.

DF Cat
Leopard 4092 1730kv
Octura x447/3
(2) 3s 45c 5000 Hyperion packs
SeaKing 180

[jevmax]

Steven,
You should go slightly faster. However, the difference could be so small that it's not noticeable on a GPS.

[JIM MARCUM]

Steven, if you are getting 65 MPH with your strudder I would expect 1-3 MPH increase with an offset rudder. And, you should also see a considerable improvement in stability and more control when turning. Please, give it a try & let us know what you find. JIM

PS: I was running a strudder on my 56" Segad. It was squirely as hell. www.youtube.com/watch?v=IPZGtssIXyQ Gonna put an offset on it & test it in a few weeks. Let you know how that goes.

[Steven Vaccaro]

Steven, if you are getting 65 MPH with your strudeder I would expect 1-3 MPH increase with an offset rudder. And, you should also see a considerable improvement in stability and more control when turning. Please, give it a try & let us know what you find. JIM

PS: I was running a strudder on my 56" Segad. It was squirely as hell. www.youtube.com/watch?v=IPZGtssIXyQ Gonna put an offset on it & test it in a few weeks. Let you know how that goes.

I'm running a couple of inline boats, none of them handle as quite like that.

[martin]

My friends Genesis would do the same as Jims on straight line runs along with a bit of porpoising, you didnt know which way the boat was going to shoot off suddenly. He even fitted a more powerfull servo thinking the rudder & servo was being pushed round but it made no difference. I told him to offset the rudder & bingo a completelly different boat in every aspect, no porpoising faster speed & turns like on rails. With the inline rudder i saw it turnover in turns more times than that now first time out never came close to flipping & going much faster in turns. Martin.

[detox]

A rudder that is not fighting itself to keep hull tracking strait is a fast rudder. For perfect rudder adjustment set rudder dead strait in line with centerline of hull (offset or inline rudder). Then remove turnfin and run the boat (accelerated quickly)then check to make sure boat is tracking strait. If not bend or shim your strut until hull tracks strait. Once strut is set do the same for turnfin making sure rudder is dead strait. You may have to bend or shim turnfin bracket to get hull to track strait.

[martin]

Steven do you think their would be much noticable difference between the Leopard 4092 motor & the 4082 on 6s in a 41" deep v mono. Martin.

[JonD]

I guess it was my recent thread about Genesis prop/strut angle and porpoisong that started this (very informative) offshoot thread Re Offset rudder versus in line rudder. Wow, this forum is the "best" I have (and still am) learning so much. Thanks guys.

From my limited experience, I would like to add one comment. I have not had any problems running with the strudder with regards running in a straight line at any speed (about 60 mph full speed with my current set up). It always runs straight as a die. But I have upped the size of the steering rod and sleeved it with a carbon fibre tube (from Kintec) that fits it precisely. It pretty well has zero bending flex in it now - incredible the difference that added the carbon fibre tube made. I am wondering whether this may prevent the problem that Fluid spoke about, by keeping the rudder on track, so to speak, and not allowing any slight oscillation movements in it "The worst offender is the aerated water. This causes random air pockets to form on the sides of the rudder, inducing a slight oscillation or 'hunting' down the straights. This causes drag and may require steering corrections to keep the boat running straight" .

Just a thought from a newbie!

However, I certainly have some turning problems. Turning one way (can't remember which direction - I'll have to check) the boat seems to turn pretty OK, even at speed. But turning in the other direction it is an absolute pig and squirrels and bounces all over the place. Would I be right in thinking that this is due to the in-line rudder set up, and an offset rudder would eliminate this?

Cheers,

Jon

[martin]

My friends Genesis was very squirrelly in the turns & would flip if to tight turn was taken, he had to take quite wide turns to prevent this. Switched to the offset rudder & it turns very sharpe much faster & stays flat & planted in turns now.