Seaplanes Aircraft that typically take off and land on water...radio control seaplane discussions are in here.

WATER RUDDER - EASY:

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Old 08-03-2004, 06:51 PM
  #1  
richardclausen
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Default WATER RUDDER - EASY:

I need some plans on how to make water rudders that are fixed to the floats & that retract as the aircraft gains speed.

Could anyone please help me with this. This is what I have designed, but dont know if it will work?

Richard
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Old 08-03-2004, 08:29 PM
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CraigA
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Default RE: WATER RUDDER - EASY:

Richard,
Williams Brothers makes these commercially...and Tower sells them. I have not seem them up close but it looks like your design is close....they use a rubber band instead of a spring. Maybe you can get some ideas from these links.
http://www2.towerhobbies.com/cgi-bin...?&I=LXKK27&P=7
http://www2.towerhobbies.com/cgi-bin...?&I=LXKK28&P=7
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Old 08-03-2004, 08:52 PM
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JimCasey
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Default RE: WATER RUDDER - EASY:

You have the right basic idea. Here's one that I made from an old hinge and some brass sheet.
And if you want to BUY a water rudder, the ERNST unit comes in 3 sizes and is superior to the good previously referenced Williams Brothers unit.
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Old 08-03-2004, 09:23 PM
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Oregon Craig
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Default RE: WATER RUDDER - EASY:

I have used the Ernst, and it is good. I actually found that leaving the rubber band OFF was better. THe rudder will fall into the water at slow speed, and ride up when you are starting your takeoff run. This worked better for me. When at speed and up on the floats, the air rudder was all that was needed. After slowing down from landing, the rudder dropped back down under water for taxi time.
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Old 08-04-2004, 10:47 AM
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Default RE: WATER RUDDER - EASY:

I really don't understand why you would want them to retract when speeding up. They are not detrimental to anything.

The only reason they are designed to pivot at all is in case you hit something (so they won't break) or to prevent them from snagging on something (like a strong weed or abandoned fishing line) and prevent you from moving.
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Old 08-04-2004, 05:57 PM
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Default RE: WATER RUDDER - EASY:

ORIGINAL: MinnFlyer

I really don't understand why you would want them to retract when speeding up. They are not detrimental to anything.

The only reason they are designed to pivot at all is in case you hit something (so they won't break) or to prevent them from snagging on something (like a strong weed or abandoned fishing line) and prevent you from moving.
The one I was talking about would not center properly with the air rudder, too much play in the control, thus the 2 were often fighting each other. Removed the rubber band, and instant straight take-off runs.
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Old 08-05-2004, 06:25 AM
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Default RE: WATER RUDDER - EASY:

Water rudders should be retractable because they cause a LOT of drag in the water. A properly-sized rigid water rudder sticks down no further than the step, but almost everybody uses a "scale"-looking water rudder that sticks down much further. "Scale" water rudders also retract, and are only dropped into the water for taxiing in the displacement mode. The Ernst units provide for a retraction cable for true scale operation. A WR that drops into the water of its own accord is also adequate for model operation.

The previously-mentioned alignment issue is also a valid one.

If your water rudder drags in the water when you are on-step, your takeoff run is a lot more "run" than it needs to be.
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Old 08-08-2004, 06:13 AM
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Default RE: WATER RUDDER - EASY:

THanks for all the replys.

Where can I buy this ERNEST water rudder?

Which shop, in which country?

Here are some pics in the meantime....Can you see any faults if any ???? My first float plane!

THanks Rich (& How much +/-)
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Old 08-08-2004, 09:55 AM
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Default RE: WATER RUDDER - EASY:

Well, in this country TOWER or OMNIMODELS.COM

Over there, I don't know

http://www2.omnimodels.com/cgi-bin/w...I=ERNQ2600&P=7
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Old 08-11-2004, 02:29 PM
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Default RE: WATER RUDDER - EASY:

Looking at your float set up, I see one problem, actually two. First is, I think your wing incedence is to steep. You want it at about zero to 1 degree postive to your floats. Next thing is, I've see those floats in action and they have very little internal bracing. Consquently they break at the mounting area very easily with any side load. Hope this helps.

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Old 08-11-2004, 08:35 PM
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Default RE: WATER RUDDER - EASY:

Ben, I'm not saying you're wrong, but I think the photos are misleading....particularly the stripe on the Hoerner tips make it look like the wing incidence is extreme. Looking at the fuselage, it's about perfect. Also, it's floating a little tail down, which adds both to the illusion and to the seaworthiness of the craft.
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Old 08-12-2004, 09:57 AM
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Default RE: WATER RUDDER - EASY:

Jim,
You have a good eye. Once I looked agin, it seems everything is kosher.

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Old 08-13-2004, 03:57 AM
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richardclausen
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Default RE: WATER RUDDER - EASY:

Hello Gents

THanks for all you positive feedback, Its been great. Well I have been hard at work making & designing my water rudders. Im attaching pics to show you. Just remember that I live in Hong Kong, so space is at a premium. I dont have a workshop & EVERYTHING was done on the floor in my living room, with a 9 month old baby crawling around (Well Trying to keep her away....Bizzy bee.

I can adjust the forward float by +4 deg to - 4 deg, so I have some flex there. How can I make the floats more rigid. As they feel now they are rock steady & feel realy strong. When you mean side loads, do you mean if I crab it in for a landing, or taxying???

Here are the pics. Im almost innished. Just have to paint the gear with rust proof Oxidant primer / paint.

Richard
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Old 08-13-2004, 03:11 PM
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Default RE: WATER RUDDER - EASY:

Richard,
Yes , landings that are crabbed in and landed at that angle can put extreme side loads on the float. Sometimes, take off runs can degrage into a wide turn, catch an outside edge, and dig into the water hard. To guard against this, the floats should be supported as wide as possible laterally across the float mounting area.
Your float mounting gear look very strong from the fuse down to mounting point, but are attached to the floats with a narrow bracket.
If these are the floats I'm thinking off, they are hollow inside with no bulkhead to speak of, and only have a narrow strip of hard wood nose to tail under the float surface.
One way to guage the strenght would be to grasp the float on the bottom and rotate it side to side. If that feels sturdy, you'll be OK.
If it flexes at all, any landings that are not straight ahead and soft will give you trouble.
Hope this helps, and I'm not being to advisey. All I can say is, Been there! Done that!

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