Nitro models pusher Bobcat?
02-02-2009, 09:46 AM
#3626
Senior Member
RE: Nitro models pusher Bobcat?
When banking in a left hand turn and applying elevator to tighten the turn, the plane wants to climb.
I am changing from an OS .50 to a Tower .75 and wondered what rpm the APC 11x7 turns on the OS .75? Is the take off run improved?
Bill
02-02-2009, 09:28 PM
#3627
Senior Member
Join Date: Nov 2005
Location: Bangkok, THAILAND
Posts: 129
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
The takeoff run on the os75 is pretty decent, and shorter than the 50 size engines without a tuned pipe. The APC 11x7 is turning about 13k on a pusher, but it turns a tractor prop 14.5k. The plane will be LOUD....as just experienced with my initial flight with the os75. It's got plenty of power to do whatever you want, but the top speed to me seems lower than my old setup (50 heli engine with macs pipe), but then again, I didn't really wring it out. My CG balances at 10.5 inches, and I added about 25 grams of lead to the nose to achieve this. I don't have this problem with my Bobcat 25, so I'm wondering if the rudder thrust line may be off.
02-02-2009, 11:19 PM
#3628
Senior Member
RE: Nitro models pusher Bobcat?
Thanks for the rpm numbers.
I also see a thousand rpm or so less with pusher set up’s. For those engines that can be run backwards I also see a thousand rpm or so less using tractor props. Don’t know why.
A few very hard bounce landings will bend the wing tube. The bend in my wing tube was not noticeable until the wing was removed. Something you might like to check. A bent wing tube will skew the horizontal stabilizer. Seems like a large slow loop could be used to check both the “rudder thrust line” and engine left/right thrust line.
Bill
The APC 11x7 is turning about 13k on a pusher, but it turns a tractor prop 14.5k.
I'm wondering if the rudder thrust line may be off.
Bill
02-03-2009, 12:00 AM
#3629
Senior Member
Join Date: Nov 2005
Location: Bangkok, THAILAND
Posts: 129
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
My wings are epoxied on, so the wing tubes shouldn't be bent. I guess I just have to take out the straightedge and measure the booms to see if there are any discrepancies. As for eyeballing the rudders, I find that the left rudder ( looking from the back of the plane ) seems to be curving inwards, which could be causing the additional lift while the plane is banked left. I haven't tried to turn right yet, as the pattern at my field is just left turns. If the airplane nose drops while turning right, then I guess I'll have to splay the rudder out a bit to correct the tendency of the plane to climb in a left turn. I have some degrees of left thrust in the engine, so I should check if it flies straight in level flight, and not going in one direction or the other...if it does, then the rudder is off. Problem is, I can't find another airfield to fly it because of the noise it makjes.
02-03-2009, 04:22 PM
#3630
Join Date: May 2003
Location: Corning,
NY
Posts: 152
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
When balancing the plane at 10.5" i need to draw a horizontal line about 4" from the fusalage at that mark so my balancing device will fit uner the plane. Do you forsee a problem with that technique? Will it throw of my balancing point or should I use the finger method instead?
02-04-2009, 08:03 PM
#3632
My Feedback: (21)
Join Date: Aug 2005
Location: EdmontonAB, CANADA
Posts: 571
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
I got one of these as a "pre-jet trainer." I bought an OS 55AX, APC 11x7P prop and Robart 520W1 retracts.
I'm just looking in to what servos to use. I am not a Hitec fan, I like Futaba servos. I'll see if they have a good mini-digital that fits the bill. I'll likely run the stock servo setup with 2 rudder servos and two elevator servos matched up.
I'm not looking for flat-out speed but 100MPH or so would be great. This is just for fun and to practice landings etc in prep for an EDF or turbine some point down the road.
Lots of great information on this thread!
I have had a couple of small EDF's including a Kyosho Illusion (over weight and WAY under powered but still fun.)
I'm just looking in to what servos to use. I am not a Hitec fan, I like Futaba servos. I'll see if they have a good mini-digital that fits the bill. I'll likely run the stock servo setup with 2 rudder servos and two elevator servos matched up.
I'm not looking for flat-out speed but 100MPH or so would be great. This is just for fun and to practice landings etc in prep for an EDF or turbine some point down the road.
Lots of great information on this thread!
I have had a couple of small EDF's including a Kyosho Illusion (over weight and WAY under powered but still fun.)
02-05-2009, 09:57 AM
#3633
Join Date: May 2003
Location: Corning,
NY
Posts: 152
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
CRhammond,
I have mine outfitted with the following Futaba Servos using a 6.0 volt battery:
2 Rudder S3010 .90 oz of torque
2 Alieron S3010
1 Elevator S3010
1 Throttle S3004 57 oz of torque
1 Nose gear S3004
1 retract valve S3004
I have not flew mine yet, but I will be using a evolution .61 with an 11X7 APC prop. My balance point will be at 10.5", and looks like I will need a lot of lead in the nose to get it to balance i am guessing.
I have mine outfitted with the following Futaba Servos using a 6.0 volt battery:
2 Rudder S3010 .90 oz of torque
2 Alieron S3010
1 Elevator S3010
1 Throttle S3004 57 oz of torque
1 Nose gear S3004
1 retract valve S3004
I have not flew mine yet, but I will be using a evolution .61 with an 11X7 APC prop. My balance point will be at 10.5", and looks like I will need a lot of lead in the nose to get it to balance i am guessing.
02-07-2009, 12:51 PM
#3634
Senior Member
RE: Nitro models pusher Bobcat?
I just changed my 50 heli engine to a OS75 AX and flew it this weekend...it flew all right, but not with the speed of my 50 engine with a macs pipe. Bad news is, the 75 is just as loud as my 50 with the pipe, and the airfield already had comments about the loudness...
Bill
02-11-2009, 10:27 AM
#3635
Member
My Feedback: (1)
Join Date: Aug 2005
Location: Tewksbury,
MA
Posts: 70
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
Hi all, my buddy and I are both building these planes now. Thanks for all of the tips in the last 150 pages!
I see lots of discussions and people seem to have good luck with many different engines. I have an OS 55 and an OS 75 available. I want to use the 55 since it seems like a good size with plenty of power. My buddy wants to go with an OS 75. I'd like to keep the planes the same so we can have some fun with them.
Our field is very noise sensitive so I feel the 55 will be best. No sense having a 75 if I can't turn a bigger prop. There's no way I would run a 75 with an 11x7, the noise would be a killer. Nobody makes an 11x9 or 10 x 10 etc. So I'd end up running it at half throttle I guess. Also the 55 is lighter in the tail so less weight needed in the nose.
Who's right here? What's your vote?
I see lots of discussions and people seem to have good luck with many different engines. I have an OS 55 and an OS 75 available. I want to use the 55 since it seems like a good size with plenty of power. My buddy wants to go with an OS 75. I'd like to keep the planes the same so we can have some fun with them.
Our field is very noise sensitive so I feel the 55 will be best. No sense having a 75 if I can't turn a bigger prop. There's no way I would run a 75 with an 11x7, the noise would be a killer. Nobody makes an 11x9 or 10 x 10 etc. So I'd end up running it at half throttle I guess. Also the 55 is lighter in the tail so less weight needed in the nose.
Who's right here? What's your vote?
02-11-2009, 11:55 AM
#3636
Join Date: Nov 2005
Location: Poolesville, MD
Posts: 12,624
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
The noise comes from the propeller not the engine, and this is exacerbated by the pusher configuration.
To reduce the noise you'll have to spin the prop more slowly, e.g. use a bigger lower pitch prop... this will produce more thrust, but the plane will not fly as fast.
So it's your choice, slow the plane down and you'll reduce the noise. Speed it up and it will be LOUD!!!
Pusher's are inherently and surprisingly loud.
Even my electric Bobcat 25 sounds like I have a .46 glow engine on it screaming at full throttle.
I think you'll end up surprised at the sound that comes out of your plane, even after taking all anti-noise precautions.
To reduce the noise you'll have to spin the prop more slowly, e.g. use a bigger lower pitch prop... this will produce more thrust, but the plane will not fly as fast.
So it's your choice, slow the plane down and you'll reduce the noise. Speed it up and it will be LOUD!!!
Pusher's are inherently and surprisingly loud.
Even my electric Bobcat 25 sounds like I have a .46 glow engine on it screaming at full throttle.
I think you'll end up surprised at the sound that comes out of your plane, even after taking all anti-noise precautions.
02-11-2009, 01:10 PM
#3637
Senior Member
RE: Nitro models pusher Bobcat?
After flying with two different .45’s and a .50 I think a .75 is the correct choice. The airplane will weigh almost 8 pounds. Pusher configurations also seem to turn the prop about 1.000 rpm less on the Bob Cat than one would expect with a conventional airplane with tractor prop. An 11 x 7p will probably be correct for a .75 however I purchased a 12 x 6p Zinger just in case.
Bill.
Bill.
02-11-2009, 01:21 PM
#3638
Senior Member
RE: Nitro models pusher Bobcat?
Has anyone had a Tower .75 apart? My Tower .75 came with two head gaskets installed, .004” and .0085” thick. Does anyone know if two head gaskets from the factory is normal?
Bill
Bill
02-12-2009, 08:17 PM
#3639
Member
My Feedback: (1)
Join Date: Aug 2005
Location: Tewksbury,
MA
Posts: 70
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
For those of you that modified the elevator to use one servo, how the heck did you run the wire? Making a mounting plate should be easy but then you have to cut across at least 2 ribs. Are the ribs on the horizontal stab solid? On the vertical stabs there are no holes passing thru to the bottom. You'd have to drill a long hole, then cover it up somehow.
Am I missing something?
Am I missing something?
02-12-2009, 09:22 PM
#3640
Join Date: Nov 2005
Location: Poolesville, MD
Posts: 12,624
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
ORIGINAL: BillS
Has anyone had a Tower .75 apart? My Tower .75 came with two head gaskets installed, .004” and .0085” thick. Does anyone know if two head gaskets from the factory is normal?
Bill
Has anyone had a Tower .75 apart? My Tower .75 came with two head gaskets installed, .004” and .0085” thick. Does anyone know if two head gaskets from the factory is normal?
Bill
02-12-2009, 09:40 PM
#3641
RE: Nitro models pusher Bobcat?
I dont remember any problems feeding the wire through the tailplane so the ribs must have holes.
What I done for the fin was to cut a 20mm square piece out of the bottom of the boom and drill up from there through the ribs with a long bit, the hole was also useful for fishing the wire through to the front of the boom. I then simply just glued back in the square.
I did post pics but not sure if on here or maybe on rcgroups.
What I done for the fin was to cut a 20mm square piece out of the bottom of the boom and drill up from there through the ribs with a long bit, the hole was also useful for fishing the wire through to the front of the boom. I then simply just glued back in the square.
I did post pics but not sure if on here or maybe on rcgroups.
02-13-2009, 06:46 AM
#3642
Join Date: Sep 2006
Location: Fort Washington, MD
Posts: 1,261
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
Hey Everyone,
I made the plunge and bought the Falcon .25, I want to do nitro so what's the best engine? OS 25fx OS 35ax, GMS .32, Supretiger .34, ThunderTiger .36.
Any suggestions will be welcomed.
I made the plunge and bought the Falcon .25, I want to do nitro so what's the best engine? OS 25fx OS 35ax, GMS .32, Supretiger .34, ThunderTiger .36.
Any suggestions will be welcomed.
02-13-2009, 08:39 AM
#3643
Senior Member
RE: Nitro models pusher Bobcat?
For those of you that modified the elevator to use one servo, how the heck did you run the wire? Making a mounting plate should be easy but then you have to cut across at least 2 ribs. Are the ribs on the horizontal stab solid? On the vertical stabs there are no holes passing thru to the bottom. You'd have to drill a long hole, then cover it up somehow.
Bill
02-14-2009, 09:38 AM
#3644
RE: Nitro models pusher Bobcat?
For you turbine guys flying with the aileron split to form flaps, does the model pitch up or down when the flaps are deployed. There seems to be conflicting reports in the thread.
02-15-2009, 10:22 AM
#3647
Senior Member
Join Date: Nov 2005
Location: Bangkok, THAILAND
Posts: 129
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
HeliTB,
I bought the falcon 25 as well, and ended up using a TT 36 engine, which has the highest power output according to the spec sheet. Initial flights were with an APC 9x6 pusher prop, and I was getting about 14+k. However, the speed was just so so, about 70 - 80 mph level flight. I then experimented with a 10x7 cut down to 9x7, still no real improvement. I then cut down a 10x8 to 8.5x8, which showed some improvement on speed. Not too shabby, but I think I'll cut down the prop to 8x8, which should give me a few more rpm. BTW, remember to reinforce the landing gear blocks, as it is very weak. I drilled mine out and inserted 1/4 inch hardwood dowels, but it still gave way even with lots of epoxy. This planes lands just like its bigger brother, and if the front incidence is too high, it will contribute to the land and bounce syndrome...don't ask me how I know.[:@]
I bought the falcon 25 as well, and ended up using a TT 36 engine, which has the highest power output according to the spec sheet. Initial flights were with an APC 9x6 pusher prop, and I was getting about 14+k. However, the speed was just so so, about 70 - 80 mph level flight. I then experimented with a 10x7 cut down to 9x7, still no real improvement. I then cut down a 10x8 to 8.5x8, which showed some improvement on speed. Not too shabby, but I think I'll cut down the prop to 8x8, which should give me a few more rpm. BTW, remember to reinforce the landing gear blocks, as it is very weak. I drilled mine out and inserted 1/4 inch hardwood dowels, but it still gave way even with lots of epoxy. This planes lands just like its bigger brother, and if the front incidence is too high, it will contribute to the land and bounce syndrome...don't ask me how I know.[:@]
02-15-2009, 02:05 PM
#3648
Join Date: Sep 2006
Location: Fort Washington, MD
Posts: 1,261
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
cyborg1...Thanks for the tips and flight report. I bought the OS 35AX. Everything should arrive on Tuesday. Will do on the landing gear. I learned that from Bobcat 51
02-16-2009, 07:59 PM
#3649
Junior Member
Join Date: Sep 2005
Location: LisbonLisbon, PORTUGAL
Posts: 18
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
Hi all,
Just to report my first flight with Bobcat 50 with an OS55AX engine.
I read maybe much in this tread about this plane, configurations, engines, etc.... and the idea that i get was about a very dificult plane to fly and to land. I also see some movies in youtube about it and the idea was right.
This weekend a friend who alread knows this plane flown for the first time mine and after some tunning in elevator and ailerons the bobcat was set. After that i just touch in elev/ailerons stick just to feel and it was great and not so agressive as i thoutgh.
After landing my friend told me to just fill the plane and take off. It was realy a surprise for me the atitude of this plane and not so dificult to fly has i thought, so after some curves and tounneaus i land the bobcat without too much stress !!!!
I have CG at 265mm and EXPO in Ailerons at about -50%.
Flaperons or spoilerons i think that was not needed but i will try latter some.
About the noise is just a very pretty sound !!!!!!!
Best Regards
Just to report my first flight with Bobcat 50 with an OS55AX engine.
I read maybe much in this tread about this plane, configurations, engines, etc.... and the idea that i get was about a very dificult plane to fly and to land. I also see some movies in youtube about it and the idea was right.
This weekend a friend who alread knows this plane flown for the first time mine and after some tunning in elevator and ailerons the bobcat was set. After that i just touch in elev/ailerons stick just to feel and it was great and not so agressive as i thoutgh.
After landing my friend told me to just fill the plane and take off. It was realy a surprise for me the atitude of this plane and not so dificult to fly has i thought, so after some curves and tounneaus i land the bobcat without too much stress !!!!
I have CG at 265mm and EXPO in Ailerons at about -50%.
Flaperons or spoilerons i think that was not needed but i will try latter some.
About the noise is just a very pretty sound !!!!!!!
Best Regards
02-16-2009, 08:01 PM
#3650
Junior Member
Join Date: Sep 2005
Location: LisbonLisbon, PORTUGAL
Posts: 18
Likes: 0
Received 0 Likes
on
0 Posts
RE: Nitro models pusher Bobcat?
ORIGINAL: Romulo
Hi all,
Just to report my first flight with Bobcat 50 with an OS55AX engine.
I read maybe much in this tread about this plane, configurations, engines, etc.... and the idea that i get was about a very dificult plane to fly and to land. I also see some movies in youtube about it and the idea was right.
This weekend a friend who alread knows this plane flown for the first time mine and after some tunning in elevator and ailerons the bobcat was set. After that i just touch in elev/ailerons stick just to feel and it was great and not so agressive as i thoutgh.
After landing my friend told me to just fill the plane and take off. It was realy a surprise for me the atitude of this plane and not so dificult to fly has i thought, so after some curves and tounneaus i land the bobcat without too much stress !!!!
I have CG at 265mm and EXPO in Ailerons at about -50%.
Flaperons or spoilerons i think that was not needed but i will try latter some.
About the noise is just a very pretty sound !!!!!!!
Best Regards
Hi all,
Just to report my first flight with Bobcat 50 with an OS55AX engine.
I read maybe much in this tread about this plane, configurations, engines, etc.... and the idea that i get was about a very dificult plane to fly and to land. I also see some movies in youtube about it and the idea was right.
This weekend a friend who alread knows this plane flown for the first time mine and after some tunning in elevator and ailerons the bobcat was set. After that i just touch in elev/ailerons stick just to feel and it was great and not so agressive as i thoutgh.
After landing my friend told me to just fill the plane and take off. It was realy a surprise for me the atitude of this plane and not so dificult to fly has i thought, so after some curves and tounneaus i land the bobcat without too much stress !!!!
I have CG at 265mm and EXPO in Ailerons at about -50%.
Flaperons or spoilerons i think that was not needed but i will try latter some.
About the noise is just a very pretty sound !!!!!!!
Best Regards