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Bob Cat Copy Falcon 120 Jet

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Bob Cat Copy Falcon 120 Jet

Old 07-04-2009, 03:55 PM
  #2726  
Pekki
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Default RE: Bob Cat Copy Falcon 120 Jet

Where to put the CG on the Falcon 120 (King Cat 54)?
Old 07-04-2009, 05:46 PM
  #2727  
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Default RE: Bob Cat Copy Falcon 120 Jet

330mm from the leading edge, measured at the fuse
Old 07-05-2009, 03:27 AM
  #2728  
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Default RE: Bob Cat Copy Falcon 120 Jet

Had 2 more flights on the Falcon today (retract air pump went flat!! Plan was to have 4 flights) Great grass jet, but is anyone getting board with their Falcon?

Mav
Old 07-05-2009, 06:59 AM
  #2729  
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Default RE: Bob Cat Copy Falcon 120 Jet

how does it rotate with so much fuel ahead of c/g???
Old 07-05-2009, 07:19 AM
  #2730  
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Default RE: Bob Cat Copy Falcon 120 Jet

They rotate fine.
I have 64 once juice bottle for fuel. I have found that using about 15 degrees of flap on take off makes for a much nicer looking take off. Without flaps, it tends to pop off the ground. if you use flaps it gives it a smoother lift off the ground.


No, I am not board with mine. Its a fun plane and I have been flying it for 2 years now.

Joe L.
Old 07-05-2009, 08:29 AM
  #2731  
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Default RE: Bob Cat Copy Falcon 120 Jet

If you don't have a slight nose up attitude the plane will tend to leap off the pavement. When building one of these make sure that your retract location and strut length are such that the center of the wing leading edge sits slightly higher off the ground than the center of the wing trailing edge. If you put in too much nose up attitude it will tend to bounce on landing.

My wing is about 3/4" higher in front with the model sitting on the ground. This gives a nice smooth take off. There are a couple others in my club that sit slightly lower in the front and they leap off the runway. If your model is already built you could put a spacer under the nose retract, or the easy fix is to use take off flaps as Joe L. suggests.

Joe
Old 07-05-2009, 05:58 PM
  #2732  
Jetpilot24
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Default RE: Bob Cat Copy Falcon 120 Jet

Joe

I built mine so the leading edge of the wing and the trailing edge sit level. With no flaps on take off she leaps into the air. The take-off flaps make for a nice take off.

Joe L.
Old 07-06-2009, 11:51 PM
  #2733  
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Default RE: Bob Cat Copy Falcon 120 Jet

Flame Turbine Mounts!

made on my home made CNC Router!

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Old 07-07-2009, 03:49 PM
  #2734  
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Default RE: Bob Cat Copy Falcon 120 Jet

Nice work.
Mounts will be a later project on mine. Right now i am building my own struts and looking for a more economical brake setup.

Blazer
Old 07-15-2009, 11:20 AM
  #2735  
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Default RE: Bob Cat Copy Falcon 120 Jet

Derrick I have been watching the For Sale part of RCU and have not seen your tanks there. Are you still planning on selling them?
Old 07-15-2009, 03:31 PM
  #2736  
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Default RE: Bob Cat Copy Falcon 120 Jet

Yes they are for sale. Let me know if you want a set.

Thanks,
Derrick
Old 07-17-2009, 07:51 PM
  #2737  
derrickxp8103
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Default RE: Bob Cat Copy Falcon 120 Jet

Center Tank is about 85oz.

New price for set is $130 .........NO FITTINGS.

Center Tank........$70

Wing Tank........$30/each

I will post these in the buy/for sale section in this site !!!

Derrick
Old 07-23-2009, 10:14 PM
  #2738  
derrickxp8103
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Default RE: Bob Cat Copy Falcon 120 Jet

I use West Systems Epoxy extra slow cure.

Thanks,
Derrick
Old 07-24-2009, 11:22 AM
  #2739  
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Default RE: Bob Cat Copy Falcon 120 Jet

120 OZ TANK.you can put acid in this if you like.. its vynalester resin..
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Old 07-24-2009, 11:41 AM
  #2740  
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Default RE: Bob Cat Copy Falcon 120 Jet

Rapptor what about the front wing tube??????
Old 07-24-2009, 02:21 PM
  #2741  
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Default RE: Bob Cat Copy Falcon 120 Jet

you are a very sharp guy!!the front tube is for rotation of the wing only..not a spar.i put 3/8 ply inside of fuse just around the hole.then i cut and glue the front tube in the wing only.make it just long enough to go through the ply ring dubler.ther is about 1/2 inch clearance at the bottom ,lower corners ,of the tank. you can run fuel lines and wires in this area.. tank weight is 2.3 oz..
Old 07-26-2009, 04:07 AM
  #2742  
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Default RE: Bob Cat Copy Falcon 120 Jet

Hey Rapptor!

That sounds like a good idea! but i wouldnt put my money on that being to successfull...bigger tank more "G,s" in the frame...but please i would love to be wrong on this one...so let us know how the flights go...We have seen bent spars right here on this forum so the wing loading must go some where,and with the fuel bowzer you just cramed in there its gonna really load up the frame around the holes....keep us informed of your succes or lack of either way it will be very interseting!

Cheers

Haydn
Old 07-26-2009, 06:13 AM
  #2743  
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Default RE: Bob Cat Copy Falcon 120 Jet

Hi guys, Im with jet junkie on this one, I think the front spar is doing its job and adding to the overall strength of the wing, obviously we all have a choice, and I have the front spar passing right through to both wings. Also, just a reminder, some wing spars are too short and do not reach fully into the end ribs of the wing, check both spars before you fly, as this is a serious weak spot. cheers Tim
Old 07-26-2009, 06:31 AM
  #2744  
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Default RE: Bob Cat Copy Falcon 120 Jet

I WOULD NOT RECOMEND USING A STOCK SPAR ON ANY TURBINE CONVERTION..THE FRONT TUBE DOES NOT GO INTO ,OR FAR ENOUGH, TO DO ANY GOOD,AS A SPAR.ITS IN A PLASTIC TUBE.. THAT SHOULD BE A HINT ..SORRY FOR CAPS ..FORGOT
Old 07-26-2009, 01:04 PM
  #2745  
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Default RE: Bob Cat Copy Falcon 120 Jet

Just to clarify, with my old kit and the newer one, the kit is suppilied with an Ally front spar and Ally rear spar.
Inside the wing, there is a lightweight paper/fiber guide tube, that guides the spars into the wing only, it has virtally no strength. It is a guide
The newer kit, has the same two spars but has an additional bolt, towards the front of the wing, which clamps the front of the wing to the fuse. The Older kit, only has the one bolt, which you access through the bottom of the fuselarge.
The newer wing is built lighter, and the wing ribs are spaced slightly further out. This means that the front and rear spares, are approx 1 inch too short to reach the outer most wing ribs, they were supposed to meet up with. This is what i found on mine and as I was abroad at the time, with no access to model equipment, I extended both my spars by 1 inch, by using a piece of fiberglass fishing rod inserted inside the ally tube and joined a 1 inch extension at one end. This is extreamly strong.
I have always used a replacement carbon rear spar, I think its around 20 or 22 mm diameter.

With the addition front bolt on the newer wing acting as an anti rotation device, I am sure the manufacturer, would have left the front spar out of the kit, to save money, if they didnt think it was neccessary.

As I said before, if the spars do not reach their end ribs in the wing, there is a serious lack of of strength and also I would never fly without both spars fitted. cheers Tim
Old 07-26-2009, 03:58 PM
  #2746  
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Default RE: Bob Cat Copy Falcon 120 Jet

the main spar does not fail at the ends.. it fails in the center..mine was also to short..you are missing the point.. when fliyng,the wing loading is more or less spread over the entire wing..its not lifted just at the wing tip.anyway, after taxie, and 2 minutes of flight,its {the fuel tank}the same as the guy who has 3 tanks!!! now you can fly like a ."SPAZ"... so much for extra g"s the front ,so called spar does not even go all the way through the rib it ends at.. its capt off.. spar?????????
Old 07-26-2009, 06:01 PM
  #2747  
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Default RE: Bob Cat Copy Falcon 120 Jet

Rapptor, I also cut the front tube so that I could fit a kevlar tank in mine from turbine connections, the same tank that goes in the old kangaroo's. I got over 30 flights on mine and never had a single issue with the spar. If you look back I believe I have pictures of this. Like you stated the front spar is for anti rotation only.
Old 07-27-2009, 02:35 AM
  #2748  
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Default RE: Bob Cat Copy Falcon 120 Jet

ORIGINAL: RAPPTOR

the main spar does not fail at the ends.. it fails in the center..mine was also to short..you are missing the point.. when fliyng,the wing loading is more or less spread over the entire wing..its not lifted just at the wing tip.anyway, after taxie, and 2 minutes of flight,its {the fuel tank}the same as the guy who has 3 tanks!!! now you can fly like a .''SPAZ''... so much for extra g''s the front ,so called spar does not even go all the way through the rib it ends at.. its capt off.. spar?????????
Unfortunatly this is not quite correct, a wing is a cantilever and does not have a Universly distributed Load (UDL) due to the wing being tapered and the tip voticies dimminishing the lift capability of the wing due to turbulance, the fulcrum for the wing spar/cantilever is at the root rib and any failier whould be at a point away from this fulcrum, assuming the spar is able to take the shear load. but along the spar towards the other wing at a point that the cantilever changes load application or the load is equalised i.e in a rate turn when both wings are loaded equally this would be in the centre and the maximum bending moment would be there. The front so called spar if only a incidence pin would only need to be short and through the root rib into the fus, the designers of this airframe considered the front spar needed to be longer to take some of the load off the main spar and distrubute this into the fus at that point, if the manufacturer thought they could get away with an incidence pin only 1" long then that is what they would have supplied in the interests of cost efficiency.

Taking into account the stories of folded wings admittedly not total failiers and bent main spars, I would suggest that the main spar is reinforced in some manner to help with the increased load that would be placed on this by removal of the continuity of the front spar.

Just a suggestion.
Mike
Old 07-27-2009, 06:06 AM
  #2749  
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Default RE: Bob Cat Copy Falcon 120 Jet

[&o]working on this theory,, i would sure think a prop would aso need a spar???cetrafugal forces aside.did you take note ,that most ,if not all ,wing spars do not go to the tip of the wing?? also they get smaller.. even in a non taper wing..remember the term, main arodynamic center??
Old 07-27-2009, 06:12 AM
  #2750  
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Default RE: Bob Cat Copy Falcon 120 Jet


ORIGINAL: RAPPTOR

[&o]working on this theory,, i would sure think a prop would aso need a spar???cetrafugal forces aside.did you take note ,that most ,if not all ,wing spars do not go to the tip of the wing?? also they get smaller.. even in a non taper wing..remember the term, main arodynamic center??
I do not understand your reference of a prop needing a spar?

If a wing spar does not go to the tip of the wing, what supports the ribs?

Main areodynamic center Explain what that is please?

Mike

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