Bob Cat Copy Falcon 120 Jet
10-06-2008, 03:58 PM
#1753
Member
Join Date: Jul 2008
Location: Wichita Falls,
TX
Posts: 79
Likes: 0
Received 0 Likes
on
0 Posts
RE: Bob Cat Copy Falcon 120 Jet
I have a Nitro Models Bob Cat 52 With a Welgard C50/55/06. Available frm BPHOBBIES.com (About the same power as a 40 size wet engine) 5 Cell Lipo at 3700mh.
It flyes great about 80 or 90 MPH? Total About 6Lbs.
Ray
It flyes great about 80 or 90 MPH? Total About 6Lbs.
Ray
10-06-2008, 04:11 PM
#1754
My Feedback: (9)
Join Date: Apr 2002
Location: Belton , MO
Posts: 3,126
Likes: 0
Received 0 Likes
on
0 Posts
RE: Bob Cat Copy Falcon 120 Jet
I used a 67 floz. Windex Bottle, Fitted in with the cap to the rear, it slides in till the cap hits the last wood bulkhead. I left it in. this bottle fits very well, leaving complete access to the wing attach bolts. Also it is sitting on top of a 12 fl oz. Sullivan boat hull flat tank, for Smoke. The windex bottle looks like it is made for this application. Ill try to get some pix.
10-07-2008, 06:53 AM
#1756
Junior Member
Join Date: Jul 2007
Location: Kernersville,
NC
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
RE: Bob Cat Copy Falcon 120 Jet
HI, here is a link to a video of my new nitroplane. http://www.youtube.com/watch?v=AMLDiDmX4Ug [X(]
10-07-2008, 09:45 AM
#1757
Senior Member
Join Date: Mar 2006
Location: Kingsville, TX
Posts: 139
Likes: 0
Received 0 Likes
on
0 Posts
RE: Bob Cat Copy Falcon 120 Jet
Jets 2
You should start a new thread on your build of the F-86. I would be interested in converting one myself. How about it?
Jeff
You should start a new thread on your build of the F-86. I would be interested in converting one myself. How about it?
Jeff
10-07-2008, 05:04 PM
#1760
Junior Member
Join Date: Jul 2007
Location: Kernersville,
NC
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
RE: Bob Cat Copy Falcon 120 Jet
ORIGINAL: drdoom
jets2: wow. nice job. What turbine. who's pipe. this begs its own thread.
jets2: wow. nice job. What turbine. who's pipe. this begs its own thread.
10-08-2008, 07:08 AM
#1761
RE: Bob Cat Copy Falcon 120 Jet
Hi guys
I am new to this Thread as I picked up a Jetcat 120 recently, I have been through the whole thread and am a bit confused, some of you have down thrust efflex pipe sitting high and some have up thrust, efflex pipe sitting low, can someone who has their aircrft trimmed for straight and level at part throttle and the plane does not climb when opeining up to high throttle clear this up for me.
Mike
I am new to this Thread as I picked up a Jetcat 120 recently, I have been through the whole thread and am a bit confused, some of you have down thrust efflex pipe sitting high and some have up thrust, efflex pipe sitting low, can someone who has their aircrft trimmed for straight and level at part throttle and the plane does not climb when opeining up to high throttle clear this up for me.
Mike
10-08-2008, 07:43 AM
#1762
My Feedback: (48)
RE: Bob Cat Copy Falcon 120 Jet
I hope you're not planning on putting a Jetcat P120 on this plane. It's way too much thrust and too heavy for a Falcon 120.
Most are using 5 degrees downthrust (engine tailcone down, starter up). That's about right for a 14# class engine. If you go with a larger engine you'll want a bit more. 6 degrees works fine with my Wren SS. I didn't notice anyone in this thread proposing upthrust. That would be a big mistake.
Joe
Most are using 5 degrees downthrust (engine tailcone down, starter up). That's about right for a 14# class engine. If you go with a larger engine you'll want a bit more. 6 degrees works fine with my Wren SS. I didn't notice anyone in this thread proposing upthrust. That would be a big mistake.
Joe
10-08-2008, 07:57 AM
#1763
RE: Bob Cat Copy Falcon 120 Jet
Joe
Sorry for the plane description I am working on a Flycat 90 at the moment and got a bit confused, I meant the Falcon 120.
The problem I have is that if the tailcone is down and the starter up that is up thrust not downthrust is the declage that far out? I will look up the picks showing the various thrust angles and link them on this thread.
Mike
Sorry for the plane description I am working on a Flycat 90 at the moment and got a bit confused, I meant the Falcon 120.
The problem I have is that if the tailcone is down and the starter up that is up thrust not downthrust is the declage that far out? I will look up the picks showing the various thrust angles and link them on this thread.
Mike
10-08-2008, 08:22 AM
#1764
My Feedback: (48)
RE: Bob Cat Copy Falcon 120 Jet
Mike,
If the tailcone is pointed down then the thrust is directed downward. I'm not sure what the aerodynamic textbook definition is but that's what I am calling downthrust.
Rather than argue semantics, what I'm saying is that's what is needed. I've got 66 flights on my Falcon 120 and have also made motor mounts for several others. The plane tends to climb under power and at higher speeds, the angle of the engine needs to push the rear of the plane up and the nose down to offset this tendancy.
Joe
If the tailcone is pointed down then the thrust is directed downward. I'm not sure what the aerodynamic textbook definition is but that's what I am calling downthrust.
Rather than argue semantics, what I'm saying is that's what is needed. I've got 66 flights on my Falcon 120 and have also made motor mounts for several others. The plane tends to climb under power and at higher speeds, the angle of the engine needs to push the rear of the plane up and the nose down to offset this tendancy.
Joe
10-08-2008, 09:32 AM
#1765
My Feedback: (9)
Join Date: Apr 2002
Location: Belton , MO
Posts: 3,126
Likes: 0
Received 0 Likes
on
0 Posts
RE: Bob Cat Copy Falcon 120 Jet
The Declage is not off, this was designed for GLOW. but will work with a turbine if you use 5 to 6 Deg down thrust,
The reason being, semi symmetrical (almost flat bottom) wing, it is ultra high lift. the faster it goes the more lift it will produce.
It is also better to have the heat from the turbine blow under the stab. that is my .02 Cents...
The reason being, semi symmetrical (almost flat bottom) wing, it is ultra high lift. the faster it goes the more lift it will produce.
It is also better to have the heat from the turbine blow under the stab. that is my .02 Cents...
10-08-2008, 09:39 AM
#1766
RE: Bob Cat Copy Falcon 120 Jet
Joe
I don't wish to argue semantics either, but that is what has caused my confusion, the thrust line is related to the fus datum and no matter which way around the engine is the engine in your picture has up thrust compared to the fus datum, I have not assembled mine yet so have no idea if the wing has a positive or negative angle in relation to the datum, but to generate lift the wing must be at a positive AOA, have to get mine assembled and have a look.
Incidently I am putting a Graupner Kero start G 80 + on mine only weighs in at 40gms more than a Wren 54SS and can be dialed down for the amount of thrust available, but does have 21Lb on tap, also have trailing link legs and air up and down retracts, just got to glue everything in proply.
Mike
I don't wish to argue semantics either, but that is what has caused my confusion, the thrust line is related to the fus datum and no matter which way around the engine is the engine in your picture has up thrust compared to the fus datum, I have not assembled mine yet so have no idea if the wing has a positive or negative angle in relation to the datum, but to generate lift the wing must be at a positive AOA, have to get mine assembled and have a look.
Incidently I am putting a Graupner Kero start G 80 + on mine only weighs in at 40gms more than a Wren 54SS and can be dialed down for the amount of thrust available, but does have 21Lb on tap, also have trailing link legs and air up and down retracts, just got to glue everything in proply.
Mike
10-08-2008, 09:45 AM
#1767
RE: Bob Cat Copy Falcon 120 Jet
ORIGINAL: drdoom
The Declage is not off, this was designed for GLOW. but will work with a turbine if you use 5 to 6 Deg down thrust,
The reason being, semi symmetrical (almost flat bottom) wing, it is ultra high lift. the faster it goes the more lift it will produce.
It is also better to have the heat from the turbine blow under the stab. that is my .02 Cents...
The Declage is not off, this was designed for GLOW. but will work with a turbine if you use 5 to 6 Deg down thrust,
The reason being, semi symmetrical (almost flat bottom) wing, it is ultra high lift. the faster it goes the more lift it will produce.
It is also better to have the heat from the turbine blow under the stab. that is my .02 Cents...
Of course, I have been flying symmetrical for too long, as a high lift section as you say the faster it goes the more lift, therefore the wing must be forced into more and more negative to prevent excessive climbing, all now becomes clear, silly Englishman. LOL
Mike
10-08-2008, 10:02 AM
#1768
Member
Join Date: Aug 2008
Location: WestCoast,
CA
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
RE: Bob Cat Copy Falcon 120 Jet
BladEagle, Whatever ever you call it, the tailcone of the turbine NEEDS TO BE PONITED DOWN about 5-6 degrees. Just like the BVM Kingcat/Bobcat...
10-08-2008, 10:15 AM
#1769
RE: Bob Cat Copy Falcon 120 Jet
NightFlyer1
I know have this sorted in my feeble little brain, I need 5 - 6 degrees of upthrust to force the wing into a negative angle of pitch relative to the fus datum as the speed increases to prevent excessive climbing, it was drdoom who came up with the pearl of wisdom concerning the flat bottom wing section having a larger differential of negative and positive pressure above and below the wing as the speed increases, remembering back 40 years to my days of study of fluid dynamics hurts my brain now days. LOL
Mike
I know have this sorted in my feeble little brain, I need 5 - 6 degrees of upthrust to force the wing into a negative angle of pitch relative to the fus datum as the speed increases to prevent excessive climbing, it was drdoom who came up with the pearl of wisdom concerning the flat bottom wing section having a larger differential of negative and positive pressure above and below the wing as the speed increases, remembering back 40 years to my days of study of fluid dynamics hurts my brain now days. LOL
Mike
10-08-2008, 11:05 AM
#1770
Senior Member
Join Date: Apr 2008
Location: cheltenham, UNITED KINGDOM
Posts: 111
Likes: 0
Received 0 Likes
on
0 Posts
RE: Bob Cat Copy Falcon 120 Jet
ORIGINAL: BaldEagel
NightFlyer1
I know have this sorted in my feeble little brain, I need 5 - 6 degrees of upthrust to force the wing into a negative angle of pitch relative to the fus datum as the speed increases to prevent excessive climbing, it was drdoom who came up with the pearl of wisdom concerning the flat bottom wing section having a larger differential of negative and positive pressure above and below the wing as the speed increases, remembering back 40 years to my days of study of fluid dynamics hurts my brain now days. LOL
Mike
NightFlyer1
I know have this sorted in my feeble little brain, I need 5 - 6 degrees of upthrust to force the wing into a negative angle of pitch relative to the fus datum as the speed increases to prevent excessive climbing, it was drdoom who came up with the pearl of wisdom concerning the flat bottom wing section having a larger differential of negative and positive pressure above and below the wing as the speed increases, remembering back 40 years to my days of study of fluid dynamics hurts my brain now days. LOL
Mike
O come on, can`t you get you feeble little brain round this, your letting the uk down. engine is on the back so it will have down thrust if the tail cone is pointing down!!!!!!!!!!!!!!!!!!
10-08-2008, 12:27 PM
#1772
My Feedback: (48)
RE: Bob Cat Copy Falcon 120 Jet
I know you Brits like to do things like drive on the wrong side of the road, but we ought to be able to agree on which way is up and down.
Seriously, this is an interesting discussion and we obviously don't have concensus. I thought that downthrust was angling the engine to force the nose of the plane down. So if the engine is on the front of the plane the front of the engine would be angled down. If the engine is in the rear then the part of the engine that faces forward would be angled up.
The confusion results from what one guy calls downthrust the other calls upthrust. Perhaps one of the aeronautical engineers out there can straighten us out. It would be nice to know the correct textbook definition.
Joe
Seriously, this is an interesting discussion and we obviously don't have concensus. I thought that downthrust was angling the engine to force the nose of the plane down. So if the engine is on the front of the plane the front of the engine would be angled down. If the engine is in the rear then the part of the engine that faces forward would be angled up.
The confusion results from what one guy calls downthrust the other calls upthrust. Perhaps one of the aeronautical engineers out there can straighten us out. It would be nice to know the correct textbook definition.
Joe
10-08-2008, 01:05 PM
#1773
Join Date: Mar 2006
Location: Hensley,
AR
Posts: 390
Likes: 0
Received 0 Likes
on
0 Posts
RE: Bob Cat Copy Falcon 120 Jet
Joe,
I used the pattern you posted here to make an aluminum engine mount for my second Falcon. What is the downthrust (degrees) of that mount?
Cody
I used the pattern you posted here to make an aluminum engine mount for my second Falcon. What is the downthrust (degrees) of that mount?
Cody
10-08-2008, 02:33 PM
#1774
My Feedback: (48)
RE: Bob Cat Copy Falcon 120 Jet
Cody,
The pattern I posted some time ago was the one I made up for my Artes Falcon, which has 4 degrees of downthrust. That seemed about right for a 12# engine. After the first few flights I wanted more power so I put a Wren SS on it dialed down to 14#. It tended to climb slightly so I used washers to get it to about 5 degrees. That seemed fine. Later, when I had more confidence in the booms holding up I gradually increased it to 18#. At that power it tended to climb a bit so I made a new mount at 6 degrees.
So my recommendation for a 14# class engine is 5 degrees (that's what most are using). For an 18# class engine use 6 degrees. I would not recommend anything more than 18#, I don't think the airframe would hold up.
What engine are you using?
Joe
The pattern I posted some time ago was the one I made up for my Artes Falcon, which has 4 degrees of downthrust. That seemed about right for a 12# engine. After the first few flights I wanted more power so I put a Wren SS on it dialed down to 14#. It tended to climb slightly so I used washers to get it to about 5 degrees. That seemed fine. Later, when I had more confidence in the booms holding up I gradually increased it to 18#. At that power it tended to climb a bit so I made a new mount at 6 degrees.
So my recommendation for a 14# class engine is 5 degrees (that's what most are using). For an 18# class engine use 6 degrees. I would not recommend anything more than 18#, I don't think the airframe would hold up.
What engine are you using?
Joe
10-08-2008, 03:09 PM
#1775
Senior Member
Join Date: Apr 2008
Location: cheltenham, UNITED KINGDOM
Posts: 111
Likes: 0
Received 0 Likes
on
0 Posts
RE: Bob Cat Copy Falcon 120 Jet
ORIGINAL: joeflyer
I know you Brits like to do things like drive on the wrong side of the road, but we ought to be able to agree on which way is up and down.
Seriously, this is an interesting discussion and we obviously don't have concensus. I thought that downthrust was angling the engine to force the nose of the plane down. So if the engine is on the front of the plane the front of the engine would be angled down. If the engine is in the rear then the part of the engine that faces forward would be angled up.
The confusion results from what one guy calls downthrust the other calls upthrust. Perhaps one of the aeronautical engineers out there can straighten us out. It would be nice to know the correct textbook definition.
Joe
I know you Brits like to do things like drive on the wrong side of the road, but we ought to be able to agree on which way is up and down.
Seriously, this is an interesting discussion and we obviously don't have concensus. I thought that downthrust was angling the engine to force the nose of the plane down. So if the engine is on the front of the plane the front of the engine would be angled down. If the engine is in the rear then the part of the engine that faces forward would be angled up.
The confusion results from what one guy calls downthrust the other calls upthrust. Perhaps one of the aeronautical engineers out there can straighten us out. It would be nice to know the correct textbook definition.
Joe
