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Bob Cat Copy Falcon 120 Jet

Old 03-13-2010, 01:35 PM
  #3301
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Default RE: Bob Cat Copy Falcon 120 Jet

Hi Dave,

Thanks for watching and for the tip.

You have a very accurate vision. You must be right, I need do add more down thrust. I have 6 degrees, but will change to 8 degrees. Thanks to remember me that. I was so anxious and with so much adrenalin that I forgot some plane behaviour to be corrected. It was my maiden on jets too.

Its CG is also behind the manual position. ItĀ“s 355 mm from leading edge with only UAT filled. I felt its elevator too sensitive.

Now it will go back to the bench and I will do the following changes:

1) More down thrust;
2) Bring CG forward to 330mm;
3) Install wheel brakes;
4) Change fuel tank from 2L to 1.5L coke pet. I flew 5 minutes with 2L pet and landed with a little more than half tank.

Thanks

Ricardo
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Old 03-13-2010, 01:51 PM
  #3302
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Default RE: Bob Cat Copy Falcon 120 Jet

ttt
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Old 03-13-2010, 01:53 PM
  #3303
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Default RE: Bob Cat Copy Falcon 120 Jet

Nice flying Ricardo [sm=thumbs_up.gif]

Good video.
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Old 03-13-2010, 03:25 PM
  #3304
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Default RE: Bob Cat Copy Falcon 120 Jet

Six degrees should be the right amount of down thrust for that engine. First, I suggest that you put the CG at 330 mm. and set your elevator trim for straight and level flight at your normal flying speed. Then adjust the down thrust if needed.

Joe
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Old 03-13-2010, 09:20 PM
  #3305
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Default RE: Bob Cat Copy Falcon 120 Jet

Thanks Sonnich Johannesen and Joe!

Joe,

I used 6 degrees based on your past posts. I followed many tips from you and have much confidence on your experience.

Dave noted a little up/down instability on my Falcon but he did not know I had a rear CG, so you may be right, it may be CG, may be down thrust or both things.

So I will do one change at a time, first CG and then down thrust if needed.

Your Red Bull FAlcon is a state of the art!

Ricardo
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Old 03-13-2010, 10:07 PM
  #3306
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Default RE: Bob Cat Copy Falcon 120 Jet

Excelent flight Ricardo, parabens!


did you shut off the turbine at landing?


Enrique
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Old 03-13-2010, 10:38 PM
  #3307
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Default RE: Bob Cat Copy Falcon 120 Jet

Hi, amigo Enrique!

Yes I did shut off the engine at landing. I did command a shut off after touching but, as turbine has a delay on shutting off, the engine only stopped middle past runway. I did that cause turbineĀ“s idle was producing much thrust and the plane couldnĀ“t stay stopped. Also did not have brakes. So, for safe, we decided to shut it on landing.

To try to solve that "problem" we lowered turbine idle rpm from 45000 rpm to 40000rpm, but it still couldnĀ“t stay stopped. I did this with some fear, but the turbine was reliable all the time. I intend not to do that anymore and install brakes.

AbraƧo

Ricardo
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Old 03-13-2010, 11:00 PM
  #3308
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Default RE: Bob Cat Copy Falcon 120 Jet

Yes, there is always residual thrust in any turbine so brakes are needed in jets, in both main wheels. You can use a simple on/off switch air valve with plenty of silicone grease on the wheel hubs for excelent results or a proportional jettronic type valve for smooth stops as well.

Again, congrats on your flight and specially for the landing without brakes!



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Old 03-14-2010, 05:15 AM
  #3309
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Default RE: Bob Cat Copy Falcon 120 Jet

Lowering the turbine idle can result in a low speed compresser stall and flame out, it you need to do that again I suggest you put a mix on with your retract valve to keep the idle at the manufactures settings whilst in the air and having the lower idle only available on landing. Do remember to re-teach your ECU the new settings.

Mike
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Old 03-14-2010, 08:17 AM
  #3310
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Default RE: Bob Cat Copy Falcon 120 Jet

Thanks Enrique and Mike,

Your tips are really helpful. I will choose the cheapest brake system (on/off switch with grease on hub) and hope I will not need to low the idle anymore. If itĀ“s still needed I will do as suggested by Mike, thatĀ“s a really good idea.

Ricardo
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Old 03-14-2010, 08:42 AM
  #3311
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Default RE: Bob Cat Copy Falcon 120 Jet

Hey guy's

I have been working away at my Falcon120 and she is getting closer to being finished. I thoguht i better put someone in the office so here is my slapped together cockpit. I just made up some Vac from molds to keep the weight down. Not all that easy to see with such a tinted canopy but I need the nose weight so why not?

Thanks

dave
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Old 03-14-2010, 11:17 AM
  #3312
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Default RE: Bob Cat Copy Falcon 120 Jet

Guys, I donĀ“t think that is a good idea to use a low idle landing mix on a turbine plane. The residual thrust reduction will be very small and the spool up time and turbine reliability will be worsened at landing, when it is most needed in case of a go around. Worst case scenario would be a flameout, based on how difficult is for the turbine go from idle to full power specially in hot and humid conditions and at some altitude, like the one I presume Ricardo is flying (Sao Paulo).
I know it is a extreme example but interesting anyway: in carrier landings the pilots gives 100% of throttle just before touchdown in case he didnĀ“t makes the wire so he can do a safe go around.


So I think that having a good pneumatic brake system, with grease or a smooth stop valve and a reliable spoolup idle is a better option for our models.
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Old 03-14-2010, 11:24 AM
  #3313
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Default RE: Bob Cat Copy Falcon 120 Jet

Ill take one mate.
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Old 03-14-2010, 11:38 AM
  #3314
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Default RE: Bob Cat Copy Falcon 120 Jet

Ricardo,

Looking at your video it doesn't appear that you're using a lot of flap. I use about 45 degrees, and some guys use more. By using the flaps as air brakes you need more throttle on your approach and you have very good control over your speed and decent. The plane is very stable and it is possible to come in and land at almost walking speed. Try more flap instead of lowering your idle speed.

Joe
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Old 03-14-2010, 01:00 PM
  #3315
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Default RE: Bob Cat Copy Falcon 120 Jet

As I said it can lead to a low speed compressor stall and flame out, so not a good idea, just an idea to get over a problem, in fact I have my turbines set up the exact opposite i.e. higher idle with gear up, gives an amazing responce time with the 120SX I would go as far as saying as fast as any IC I have.

As Joe says use more flap, anything beyond 45 deg will act like an airbrake and will need higher throttle to keep flying, my flaps go to 90 deg and the control on landing is excellent, but then I have reflexed ailerons as well all controled on a side slider to give me something else to play with, first half of the slider gives me flap only up to about 45 deg and the second half gives me up to 90 deg of flap and about 30 deg of up aileron, fun on slow fly byes as the turbine is still in the upper range and once you put the flaps and things away the acceleration is instantainous, well it impreses me.

Mike
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Old 03-14-2010, 05:50 PM
  #3316
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Default RE: Bob Cat Copy Falcon 120 Jet

Hey atomicx I bought one of these a while back. havent gotten to building it yet but i live in provo and would like to see what you did on yours if you dont mind. would you please drop me an email at beisele@hotmail.com? thank you
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Old 03-14-2010, 07:38 PM
  #3317
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Default RE: Bob Cat Copy Falcon 120 Jet

Quote:
ORIGINAL: BaldEagel

As I said it can lead to a low speed compressor stall and flame out, so not a good idea, just an idea to get over a problem, in fact I have my turbines set up the exact opposite i.e. higher idle with gear up, gives an amazing responce time with the 120SX I would go as far as saying as fast as any IC I have.

As Joe says use more flap, anything beyond 45 deg will act like an airbrake and will need higher throttle to keep flying, my flaps go to 90 deg and the control on landing is excellent, but then I have reflexed ailerons as well all controled on a side slider to give me something else to play with, first half of the slider gives me flap only up to about 45 deg and the second half gives me up to 90 deg of flap and about 30 deg of up aileron, fun on slow fly byes as the turbine is still in the upper range and once you put the flaps and things away the acceleration is instantainous, well it impreses me.

Mike
Perfect.[sm=thumbs_up.gif]
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Old 03-14-2010, 10:01 PM
  #3318
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Default RE: Bob Cat Copy Falcon 120 Jet

I think I have 40 degrees or almost that.

I loved your flap configuration, Mike. I think I will copy it, if you donĀ“t mind... just donĀ“t know if mine can reach 90 degrees, but if I get 60/70 is also good in a crow mix. I will try.

Added to the right CG and a wheel brake system, it will be still better.

Dave, nice job on that cockpit. I had a rear CG issue on mine.

I installed everything less batteries more to the rear cause I thought it would need more weight on the tail. But that was a mistake in my falcon configuration. When it came time to measure CG to install batteries and switches, I could not reach the correct position even with 3 batteries near the nose, over the nose LG. So I had to move the pump and the UAT more to the front and only got CG at +/-350 mm. Now I will install brakes but its little extra weight wont correct CG, so I may unfortunately add some weight in the nose. Anyway it will still fly lighter cause I will change tank and save +/-500g of fuel weight.

Ricardo
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Old 03-15-2010, 04:16 AM
  #3319
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Default RE: Bob Cat Copy Falcon 120 Jet

Ricardo

On the flaps, the taper on the bottom side of the flap does not allow 90 deg flap movement as standard, however if you use the left flap on the right side and visa versa, turn them upside down and the straight edge of the underside of the flap allows 90 deg movement when installed with Robart pin hinges.

Mike
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Old 03-15-2010, 04:17 AM
  #3320
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Default RE: Bob Cat Copy Falcon 120 Jet

Hey,

This thing is CRAZY!!! LOL, I had no idea how literally you guys meant "just pull on the bulkheads and they'll pop out..." How was this thing ever supposed to fly on glow power with the engine shaking everything?? It's amazing...
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Old 03-15-2010, 04:21 AM
  #3321
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Default RE: Bob Cat Copy Falcon 120 Jet

I don't think anyone on here was under any illusion that these things are made to a very low standard, but personnaly I think it was very good of the manufacturer to make it easy for use to remove the suspect parts. LOL

Just a heads up, when you install the UC in the wing, don't screw them on too tight, the bearers will fall out.

Mike
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Old 03-15-2010, 09:48 AM
  #3322
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Default RE: Bob Cat Copy Falcon 120 Jet


Quote:
ORIGINAL: YellowAircraft

Hey,

This thing is CRAZY!!! LOL, I had no idea how literally you guys meant ''just pull on the bulkheads and they'll pop out...'' How was this thing ever supposed to fly on glow power with the engine shaking everything?? It's amazing...
I think it would have been more of a problem if they would have put the bulk heads in a plastic bag.
I looking for a carbon fiber wing spar. were do i get one.
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Old 03-15-2010, 09:56 AM
  #3323
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Default RE: Bob Cat Copy Falcon 120 Jet

http://rcfoam.com/cart.php?target=pr...category_id=94
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Old 03-15-2010, 10:00 AM
  #3324
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Default RE: Bob Cat Copy Falcon 120 Jet

ha! been pulling my hair out for nothing , thanks!
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Old 03-15-2010, 10:04 AM
  #3325
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Default RE: Bob Cat Copy Falcon 120 Jet

No problem.
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