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Roo speed brake ??

Old 01-18-2005, 10:11 PM
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r degen
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Default Roo speed brake ??

Is it necessary to make the speed brake as big as on the plans the one on mine is 11 3/4 long and 2 3/4 wide has anyone made it smaller. Thanks Randy
Old 01-18-2005, 10:45 PM
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BCoston
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Default RE: Roo speed brake ??

I would not recommend a smaller one, my first Roo was the size suggested in the plans. On my second Roo that I am currently flying I made the airbrake 12" X 3.5". I like the bigger brake much better.
Old 01-18-2005, 10:59 PM
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ghost_rider
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Default RE: Roo speed brake ??

You can actually bypass the speed break on the bottom and use the rudder as speed break. Just program the rudders so that they will deploy outwards when you activate the speed break. It works great and by not cutting out the speed break at the bottom, it helps with the structural integrity of the airplane.
Old 01-19-2005, 01:33 PM
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vortex00
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Default RE: Roo speed brake ??

ORIGINAL: ghost_rider

You can actually bypass the speed break on the bottom and use the rudder as speed break. Just program the rudders so that they will deploy outwards when you activate the speed break. It works great and by not cutting out the speed break at the bottom, it helps with the structural integrity of the airplane.
About how much outward deployment of the rudders seems to work?
I'm thinking about doing this with my TopCat.

What about yaw control before the nosewheel is down? Do you program a mix for that?

Jack
Old 01-19-2005, 04:26 PM
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r degen
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Default RE: Roo speed brake ??

ORIGINAL: vortex00

ORIGINAL: ghost_rider

You can actually bypass the speed break on the bottom and use the rudder as speed break. Just program the rudders so that they will deploy outwards when you activate the speed break. It works great and by not cutting out the speed break at the bottom, it helps with the structural integrity of the airplane.
About how much outward deployment of the rudders seems to work?
I'm thinking about doing this with my TopCat.

What about yaw control before the nosewheel is down? Do you program a mix for that?

Jack
Hey Ben tell me more I have not cut the speed brake out yet . How much travel does it take on the rudders? Thanks Randy
Old 01-19-2005, 04:53 PM
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Default RE: Roo speed brake ??

Randy

Just use as much as you could get and still allows you some rudder deflection when you move your rudder both sides without binding.

Tim Redleman and Ralph Braun flew their Roo’s many seasons with that setup and it works flawlessly.

Tim, if you have your ears on, could you chime in here?



Jack (aka vortex00)

FWIW. I've not seen this type of setup used on a TopCat so I would not recommend it.


Regards

Ben
Old 01-19-2005, 09:34 PM
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KFalcon
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Default RE: Roo speed brake ??

If you do decide to go with the bottom speed brake method, I would also suggest making it bigger than stock. It allows you to carry more throttle on final so the turbine will get to full throttle faster if needed.
Old 01-20-2005, 10:16 AM
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seanreit
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Default RE: Roo speed brake ??

I made mine bigger than stock and it worked great! One thing I don't get about the rudder deflection method is that I always felt like the rudders were not very effective, and I guess in my mind I justified that by the high angle of attack on landing that the fuse was cancelling out the rudders?? So if that was true, I'm not sure how effective deploying the rudders would be, plus between the two, they do not even compare at all in size to the stock speed brake.

I wonder if it's possible that the ones that flew that way had an exceptionally placed CG and since delta wings slow down so well anyway, that it was just observed that they slowed down well using deployed rudders and maybe it was just all that fuse and wing at a high angle of attack that was doing it??

Don't know, but the reality is that the roo might not even need a speed brake if you get the CG right??
Old 01-20-2005, 11:30 AM
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Default RE: Roo speed brake ??

ORIGINAL: seanreit

So if that was true, I'm not sure how effective deploying the rudders would be, plus between the two, they do not even compare at all in size to the stock speed brake.
Why not try it and report back to us. I flew Tim/Mr. Brauns Roo and it slowed down better than 3 Roo's that I use to have. Believe you me, with more than 700 flights on my Roo's I know what I am talking about.

BTW, if you think the rudders are ineffective, how come you could fly Roo from one end of the field to the other and back on a knife edge?
Old 01-20-2005, 11:43 AM
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seanreit
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Default RE: Roo speed brake ??

Ineffective at high angle of attack. You've got more flights on ROO's than I do, can't argue with success. I'm just suggesting that at slow speeds and high angle of attack, the fuse might have been doing the slowing rather than the rudders. Either way, I believe what you are saying, just not sure it had much to do with the rudders when a very non-conservative CG would do the same thing.
Old 01-20-2005, 12:21 PM
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Default RE: Roo speed brake ??

ORIGINAL: seanreit

Ineffective at high angle of attack. You've got more flights on ROO's than I do, can't argue with success. I'm just suggesting that at slow speeds and high angle of attack, the fuse might have been doing the slowing rather than the rudders. Either way, I believe what you are saying, just not sure it had much to do with the rudders when a very non-conservative CG would do the same thing.
I just measured the speed break and rudder on my Rookie which happens to be the same dimension as the Roo and found the following:


• the length of the rudder is the same as the length of the speed break.
• the width of each rudder happens to be ¾ width of the speed break which means that the combination of the two rudder surface area are more than the surface area of the speed break.

My hypotesis then would be that the rudder deflection would give even more breaking force than the speed break when fully deployed.

I am going to contact one of the sharpest mind in this field (my good friend Mr. Bob Parks) and would report back with his reply.
Old 01-20-2005, 12:55 PM
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Default RE: Roo speed brake ??

ORIGINAL: ghost_rider



My hypotesis then would be that the rudder deflection would give even more breaking force than the speed break when fully deployed.

If it's truly in the air stream??? Straight and level flight if the dimensions are accurate, I agree.

Also consider the lift charachteristics/benefits of the speed brake??
Old 01-20-2005, 02:40 PM
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grbaker
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Default RE: Roo speed brake ??

The speed brake is normally deployed 90 degrees. I doubt seriously if the rudders are deployed more than 45 degrees, if that much. I am anxious to hear what Mr. Parks has to say.
Old 01-20-2005, 03:31 PM
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Default RE: Roo speed brake ??

Good point Gary, 45 degrees sounds about right for what mine deflected. Any more and I think you might be pushing the limits of the fiberglass hinge.

Look, I'm not saying you have to have a speed brake on the ROO. I've never landed one without it, but have no doubts the airplane can be slowed to damn near nothing if you move the stock CG aft.
Old 01-20-2005, 03:31 PM
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Default RE: Roo speed brake ??

Hi Garry,

Would a Futaba 9451 servo be enough to maintain a 90 degree deflection at landing speed?
Regards

Reuben
Old 01-20-2005, 03:48 PM
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Default RE: Roo speed brake ??

I recommend at least 100 oz torque. Speed and metal or analog don't mean a thing here in my experinace.

In all three of the roos I built I placed a $20.00 metal gear cirrus servo that has 110 oz of torque. Never had a problem.

I used those same servos as flap servos in my first isobar. Many flights, no issues.
Old 01-20-2005, 04:18 PM
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Default RE: Roo speed brake ??

My speed brake had a Hitec 645MG on it. I flew my Roo with the CG back at the recommended position. It could be slowed down without the speed brake, but I sure liked the way the speed brake slowed it down. It would definitely be easier to land on a short runway with the speed brake.
Old 01-20-2005, 07:13 PM
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Default RE: Roo speed brake ??

I have over 100 flights on my roo. I built it without speedbrake and made the rudders bigger and use them to slow down,being deflected out on landing. They are apig in a crosswind landing!They work ok in a nocrosswind situation. I wouldnt use them again .Paul.
Old 01-22-2005, 12:15 AM
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Tim Redelman
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Default RE: Roo speed brake ??

Ben,
I can't quite remember the way it was mixed exactly but I have it set up so both rudders kicked out when I activated the mix. I think The right rudder was plugged into the rudder channel and the left was plugged into the aux2 channel on my 10X. Turn off channel 7 (or aux 2 ) Mix rudder to aux 2 100% in both directions. No offset and activate the trim function so when you use rudder trim they both move. Then make another mix rudder to rudder and hold full right rudder and push the offset button. It should read something like 86% +or- then activate the mix with whatever switch you want to use for speedbrake control. Then make another mix aux2 to aux2 Give it full left rudder and set the offset again and use the same switch as before. Go into each program and select the switch you have chosen to activate the mix and turn it to the on position. You will need to run the value up to whatever amount of deflection you desire. I used full deflection. I also had to make another mix to give down elevator when the rudders were kicked out. All this creates drag and slows the airplane dramatically and it works killer! The time spent programming this seems like it would take forever but it takes alot longer to build the speed brake trust me. This could be done with about any computer radio that has 4 available mixes. And this may be simplified but its the way I did it and it is still flying today. It also helps you learn to take full advantage of your radio system, something most guys don't seem to do. If you need help programming this on a JR radio I can help you through it just send me a PM and I'll give you my # so we can talk face to face so to speak! Also the rudders still work when their deployed one just moves in when necessary and the rudder is still very effective too. I could help try to figure it out on a Futaba but can't make any promises. Hope this helps, Tim Redelman
Old 01-22-2005, 12:22 AM
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Default RE: Roo speed brake ??

Thanks Tim…..I knew I was not hallucinating.




....ghost rider.....out.....
Old 01-22-2005, 08:24 AM
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Glorfindel
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Default RE: Roo speed brake ??

I already ask 'Dany' from team Jr here in RCU a couples years ago. See how to do it here : http://www.rcuniverse.com/forum/m_69.../tm.htm#699876
Old 01-22-2005, 09:05 AM
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r degen
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Default RE: Roo speed brake ??

Hey Thanks for all the info Guys Randy
Old 01-22-2005, 09:13 AM
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Default RE: Roo speed brake ??

but have no doubts the airplane can be slowed to damn near nothing if you move the stock CG aft.
This is exactly I done with my first roo, It had no speedbrake and landed quite well, but I lost
it in a unintentional inverted flat spin that I went entering a looping. be careful if you put the cg
aft... on the second roo I installed the conventional speed brake and the plane was a lot easier
to land and it uses a single servo (also used a cheap giant servo). The rudder deflection method works, but I still prefer the standard speed brake system, mostly because I like to have
as many resources as possible to control the plane at low speeds in the final approach. If you
are using the rudders as speed brakes they loose almost all of their action. Hope this helps,

Enrique
Old 01-22-2005, 12:54 PM
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Default RE: Roo speed brake ??

Hi,
a question to the list.
The Roo airbrake has some flexing if pressed backward (simulating air pressure). Airbrake moves around 1/2" - 3/4" backwards.
The Robart type horn (1.25" high type) is situated approximately in the airbrake centre and is connected to the servo by a 4/40 type rod which is about 3" long.
Well a picture says a thousand words so are included.

Should this flexing of the airbake be of any particular concern?


Thanks in advance

Reuben
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Old 01-22-2005, 01:06 PM
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grbaker
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Default RE: Roo speed brake ??

I stiffened my speed brake with a laminate of 1/8" balsa and 1/64th plywood epoxied to the inner surface. I have also seen a roo with what looked like 1/8" ply "ribs" glued perpendicular (90 degrees) to the inner surface. The ribs were only about 1/4" tall and ran to within about 3/4" of either end of the speed brake.

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