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Dual rudder - few questions

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Jake Ellwood

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Joined
Aug 11, 2019
Messages
76
Hi all

Looking at building a mono next. Specifically the MHZ Powerboats Cougar 55" model - Linky!

Have been looking up hardware and quite fancy a dual rudder setup because...well because I think it looks cool and will be different.

But I am wondering. Can anyone with experience provide any guidance or thoughts about them? why are they not more popular if they offer better turning performance? Assuming they do anyway.

Thanks all :)
 

Hydro Junkie

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Joined
Oct 2, 2006
Messages
4,778
I think the biggest things are weight, drag and maintenance. If you're building a boat for play, it's not a big deal. If you're building a boat for racing, however, the extra weight can screw up the balance of the boat. What you have to remember is for every ounce you have hanging off the back of the boat, you have to have weight to offset it in the front. This can be accomplished in many ways, one being to move the motor forward. That will, however, make it harder to access the motor so you're trading cool for access in this case.
Now, let's talk drag. Again, for a play boat, no big deal. For a race boat, however, anything that hangs down into the water makes more drag to overcome. That equates to a slower boat due to the added drag, a heavier boat due to more power being needed to overcome the drag of the extra blade by going with a larger motor and fuel tank or shorter run time by sticking with a smaller tank and larger motor. Again, you're trading speed, weight or time for cool.
You're probably wondering how maintenance can be an issue. Using a twin rudder will actually will make setting up and maintaining your boat harder:
1) To replace the prop or drive shaft, you will have to work around two blades instead of one, making access much more difficult unless you remove one or both blades every time you need to access the prop or shaft
2) Two rudders mean twice and many bushings/bearings to have to maintain or replace when compared to a single rudder set up. That means twice the expense as well.
3) Two rudders also means aligning them every time you have to remove them or do anything to the rudder linkages. If they are not properly aligned, you will have to deal with a boat that is hard to drive since the rudders will be fighting each other. The best comparison I can give on this is a car that needs an alignment. It won't track straight so you're constantly having to correct for drifting and it causes the tires to wear faster. While the rudders won't wear as tires on a car do, the other effects are still there.

Are you sure the "cool" factor is worth it?
 

Jake Ellwood

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Joined
Aug 11, 2019
Messages
76
Thanks for the informative reply Hydro Junkie!

So its a case of more fiddly setup and maintenance. And more fiddly to balance. Personally not worried about drag/weight. I don't race and if I were to I've got a nitro cat which I would use anyway.

I understand the alignment and how they could fight against each other if not setup correctly. Again, its more setup time but once its setup its done. I'll have a think on it.

Cheers!
 

Hydro Junkie

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Joined
Oct 2, 2006
Messages
4,778
So, if you think my answer was too long, why didn't you answer the question first? And with answer, that doesn't mean a quick, nothing answer like "it will slow the boat down". Why not show us how to properly answer a question like Jake's? Then I won't have to worry about it
 

Greg Wannamaker

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Joined
Sep 12, 2008
Messages
491
Don’t need to Phil
So, if you think my answer was too long, why didn't you answer the question first? And with answer, that doesn't mean a quick, nothing answer like "it will slow the boat down". Why not show us how to properly answer a question like Jake's? Then I won't have to worry about it
Don’t need to the question is already asked and answered, twice and I don’t answer to you at all, life is way to short and valuable to get tangled up inside the bag of cats that live inside your head. Sorry Jake for derailing your post.
 

dwilfong

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Joined
Jul 1, 2008
Messages
5,351
The first boat I ever built I put 2 rudders on it. Was a moded Dumas deep V40 that I built in 2010.
It was 2 speed master rudders one RH and one LH with a tie rod between.
Was not hard to set up at all and work flaw less.
When I changed it to 1 rudder I did not see any difference in the boat at all.
It looked way cool.
JUST DO IT!!!!!!!
 

Jake Ellwood

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Joined
Aug 11, 2019
Messages
76
Its going to happen, planning the build as we speak :) - it'll be built early next year.
 

Christian Lucas

Well-Known Member
Joined
Aug 23, 2012
Messages
310
Hi,
the 100 mph monoboat from R.Moser had twin rudder . As it is possible you can run two smaller with the same drag , so no question about to slow down topspeed. The reason was that the twin rudder has a longer lever arm as a trim tab and with twin rudder you can set then up not real parallel . If the trailing edge of both are closer than the leading edge this rudder will cause lift and workes so like a trim tab but as with longer leverarm it has less drag. As you can use separate servo for each rudder you can set up different stearing angle you can set different forces to lay the boat inside when cornering . Maybe only stear the outside placed ruder and let the inside ruder stay straight . Many interesting options .
Try it and you will get a lot to play with.Have fun .

Happy Amps Christian
 

Christian Lucas

Well-Known Member
Joined
Aug 23, 2012
Messages
310
Hi,
you can also consider different ruder position close to the middle or moore outside , or only ruder and no extra fin at the transom.
Have a look at the Mercedes Formula 1 stearing system . It is not what you can do with the boat ruder but it show that different thinking can have an advantage.
, this is for a car but you will understand. Mercedes is currently unbeatable in Formula 1 racing.

Happy Amps Christian
 

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