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Bob Cat Copy Falcon 120 Jet

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Old 08-29-2007, 04:35 PM
  #326
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Default RE: Bob Cat Copy Falcon 120 Jet

Ok, but whats the size ? since i might use wheels with brakes.
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Old 08-30-2007, 06:16 AM
  #327
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Default RE: Bob Cat Copy Falcon 120 Jet


Quote:
ORIGINAL: i3dm

Ok, but whats the size ? since i might use wheels with brakes.

69.66mm all three!
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Old 08-30-2007, 06:18 AM
  #328
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Default RE: Bob Cat Copy Falcon 120 Jet


Quote:
ORIGINAL: Woketman

Which ones? Do they fit well without a lot of re-work? Thanks.
I'm using 302's for my Falcon 120. They are the ones I used from my AMD Hawk.[&:]

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Old 08-30-2007, 08:46 AM
  #329
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Default RE: Bob Cat Copy Falcon 120 Jet


Quote:
ORIGINAL: tim777jet

The pic of the inside fuse, shows where I cut the frame top web. I removed the pre-installed throttle cable and trimmed the 2 frames to the rear of this one. Afterwards I fitted a ply top web, held by 1 screw each side.

The nylon wing bolts were binned and I managed to buy some ally 7075 grade 6 mm bolts which weight nothing compared to steel bolts.

When I test ran the engine, I made up a .020" stainless plate to wrap around the tailplane and located it simply with 2 wire clips in case of a hot start. The engine would not light up, strange as for the past 10 years it has always lit up beautifully first time. I had to extend the glow plug leads by around 4 inches, but used high quality wire for this. I found that I had to increase the glow voltage 0.2 volts, then all was well. Strange.

I am using the spektrum 2.4 gig radio and am using DS 821 servos. (sorry i said DS 811 servos in my previous post). The DS821 is designed to run on 6 Volts, unlike other Digital servos. I am using a 5 cell nicad pack, direct into the receiver. Nicads are way fwd in the nose, ahead of the air tank, and receiver near rear of the canopy. I used heavy duty switch harness and wire, but havnt measured the voltage going into the receiver. Is it best to use a high current voltage regulator, or are these Digital servos ok at higher voltages when the nicads have just been charged?
. Recever pack was mounted on 2 carbon rod rails, which locates in a hardwood bearer on one frame ahead of the air tank (I removed the installed air tank holder) and another bearer block one frame rear of the first. My engine weighs @ 3/4 pound more than an MW 54, and this alleviates any nose ballast.
I was browsing today....

I dont think you ever got this answered. the 821's are fine on a raw NICAD pack. no regulator required, nor would I use one with the AR7000. its good also from 3.9 to 9 volts, and 0-30 amps.

Just make sure your setup doesn't allow voltage to drop below 4 volts at any time. it resets the receiver and goes stupid for several seconds. I think regulators that couldn't handle the demand was resposibile for alot of the problems. A good NICAD pack will have plenty of power with a 5 cell. If the wires are long, wouldnt hurt to use larger guage from the batt to the switch. I will say alot of folks are putting double output plugs on their switches where they plug into the receiver. One in the battery port and one in any open port, or on a Y cord with anything.

good luck.
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Old 09-01-2007, 10:11 PM
  #330
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Default RE: Bob Cat Copy Falcon 120 Jet

OK I got mine flying 6 flights so far ( all of this came out of my yellow aircraft stare fire )(very fast and to small )
50 oz tank
10 oz header tank 6.5 minutes with plenty of fuel left
wren 54
funky re-tracks
9650 futabas digitals all around ( these work great )
robat struts
brakes and wheels from tam jet
futaba 5014 Rx and 12 z TX
I happen to have the wright length turn buckles In my shop these worked great and saved about 4 hours
in build time
THANKS to all that have posted it made the build go a lot faster bty the hatch mount suggested previously work awsome
Ill post pics an maybe a movie soon
no I don't know what it weighs yet and the cg is per the Manuel and needs to come back .25 in
the 45 deg of flaps would be nice but I only get about 30
I am going to try split rudders for More braking
thanks again guys
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Old 09-02-2007, 07:44 AM
  #331
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Default RE: Bob Cat Copy Falcon 120 Jet

454, which size wheels did you use, and which model robart strtus fir the falcon ?
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Old 09-02-2007, 10:08 AM
  #332
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Default RE: Bob Cat Copy Falcon 120 Jet

my wheels are 2.25 but the came out of a stare fire
I do like the size though I think the are to small for grass
I dont remember the nummber for the struts
ill have to digg that up
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Old 09-02-2007, 11:03 AM
  #333
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Default RE: Bob Cat Copy Falcon 120 Jet

If you can, please do.

A picture of the set installed could be great !!
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Old 09-03-2007, 11:27 AM
  #334
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Default RE: Bob Cat Copy Falcon 120 Jet

OK guys heres the pics keep in mined that all this came out of a yellow aircraft stare fire .
The struts had been cut off and the retract air cylinder point the wrong why (for this airframe)
but it all works great.
One thing no one has mentioned,is that the nose strut need to be longer than the mains
this make the bob cat rotate more like a real airplane instead of jumping into the air
I also use the tail pipe out of the stare fire for starting it saves the weight of the alum tape and works very well
I have not weighed it yet but will let you know when I do

AND yes you need the down thrust , for full throttle flight .
The throws in the book are good but I have found that more elevator is needed for landing.
Do add 5 mm Of up or put it on a flight mode so you only get it with the gear down.
Flaps are not needed for take off . remember these are split flaps and only make drag IE no lift

I hope this helps you as much
as this thread has helped me
I took a grand total of 4 days to bulit my bob cat ,(yes I build fast )
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Old 09-03-2007, 12:57 PM
  #335
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Default RE: Bob Cat Copy Falcon 120 Jet


Quote:
ORIGINAL: bigplumbs

The prepared cut outs are too small for standard servos the HS225 fit perfectly and have enough power so why make life difficult...
Dennis/All,

I'm working on assembling my Falcon 120.

It doesn't appear to me that HS225MGs fit the cutouts for either the elevator or the rudder. They are *slightly* too big, and it looks like I'll need to use a dremel to open them up in both width and length.

Have they changed the size of the cutouts, or what happened here?

-- Preston
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Old 09-03-2007, 02:30 PM
  #336
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Default RE: Bob Cat Copy Falcon 120 Jet

Preston,
I have recently started a Falcon as well. My servo cutouts were a bit to small on my kit also. I glued a piece of sandpaper to a 1/4x1/2 piece of balsa and sanded the cutouts a bit. It doesn take much. I also had to enlarge one of the flap servo cutouts for a std servo. the other flap and aileron cutouts were fine.

Cody
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Old 09-03-2007, 04:40 PM
  #337
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Default RE: Bob Cat Copy Falcon 120 Jet

So was mine!
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Old 09-04-2007, 10:27 AM
  #338
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Default RE: Bob Cat Copy Falcon 120 Jet

It flies. RAM500 2x24oz tanks for fuel Robart spring down retracts and Jet1A struts. Gary Szetlak
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Old 09-04-2007, 11:05 AM
  #339
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Default RE: Bob Cat Copy Falcon 120 Jet

Gary,

So how does she fly with the RAM 500 ?
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Old 09-04-2007, 02:21 PM
  #340
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Default RE: Bob Cat Copy Falcon 120 Jet

Good Stuff!
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Old 09-04-2007, 02:24 PM
  #341
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Default RE: Bob Cat Copy Falcon 120 Jet

Ready to let it go yet???? LOL...........................
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Old 09-05-2007, 11:08 PM
  #342
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Default RE: Bob Cat Copy Falcon 120 Jet

Well, my tail servo pockets were pretty darn undersized for HS-225MG servos. Maybe the guy doing the cutouts didn't drink his coffee and used the wrong template while doing the cutting, I dunno...

-- Preston
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Old 09-06-2007, 05:07 AM
  #343
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Default RE: Bob Cat Copy Falcon 120 Jet


Quote:
ORIGINAL: preston_brown

Well, my tail servo pockets were pretty darn undersized for HS-225MG servos. Maybe the guy doing the cutouts didn't drink his coffee and used the wrong template while doing the cutting, I dunno...

-- Preston
Hmmm... I just reworked only 2 sides of the pocket to get the servo to fit. I see you did all four! Maybe a cup of coffee for you too!

Dave
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Old 09-06-2007, 09:56 AM
  #344
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Default RE: Bob Cat Copy Falcon 120 Jet

I did a little off all 4 sides so as to not thin any of the underlying support blocks too much in any one direction. They aren't too big...

-- Preston
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Old 09-06-2007, 08:07 PM
  #345
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Default RE: Bob Cat Copy Falcon 120 Jet

The set up for the ELE is 2 -81MGs as one, and the rudders are 2-225MGs , or
somthing in that area.

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Old 09-06-2007, 09:31 PM
  #346
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Default RE: Bob Cat Copy Falcon 120 Jet

yes the scale is good
mine is 14lbs 6oz
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Old 09-06-2007, 09:50 PM
  #347
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Default RE: Bob Cat Copy Falcon 120 Jet


That looks like it might have been the case. I may be asking a dumb question, but wouldn't the elevator need more servo than the rudder? It would seem like it would be subject to more forces.

No matter, I've got HS-225MGs all around the tail now. Got to route out the holes in the fuselage and wait for my retracts. Starting to look like a real plane...

Quote:
ORIGINAL: angelrcdesign

The set up for the ELE is 2 -81MGs as one, and the rudders are 2-225MGs , or
somthing in that area.

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Old 09-07-2007, 07:26 AM
  #348
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Default RE: Bob Cat Copy Falcon 120 Jet

Quote:
ORIGINAL: preston_brown


That looks like it might have been the case. I may be asking a dumb question, but wouldn't the elevator need more servo than the rudder? It would seem like it would be subject to more forces.

No matter, I've got HS-225MGs all around the tail now. Got to route out the holes in the fuselage and wait for my retracts. Starting to look like a real plane...

Quote:
ORIGINAL: angelrcdesign

The set up for the ELE is 2 -81MGs as one, and the rudders are 2-225MGs , or
somthing in that area.

Winart will tell you I'm sure, that you need to have up elevator when it's in the neutral position, so as the trailing edge of the elevator is in line with the top of the horizontal stab. Otherwise take off is difficult?

Regards

BiGToP

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Old 09-07-2007, 10:21 AM
  #349
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Default RE: Bob Cat Copy Falcon 120 Jet

If up elevator is required at takeoff, it sounds like the decalage angle of the whole horizontal stab is incorrect? Is "neutral" while flying level still going to require up elevator, or is this a takeoff condition only?

-- Preston
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Old 09-07-2007, 11:43 AM
  #350
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Default RE: Bob Cat Copy Falcon 120 Jet

Or perhaps excessive down-thrust (turbine nose-up) on the turbine is cuasing too much of a nose-down pitching moment and that, in turn, is causing the elevator up-trim. Might be worth a try to decrease the turbine angle.
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