RE: Nitro models pusher Bobcat?  
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    • All Forums >> RC Airplanes >> RC Jets >> RE: Nitro models pusher Bobcat?
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    RE: Nitro models pusher Bobcat? - 9/3/2008 11:59:01 AM   
    cyborg1


     

    Posts: 61
    Joined: 11/24/2005
    From: Bangkok, THAILAND
    Status: offline     		As far as I know, Opjose tried it, but it pitched up abruptly, working as an elevator

    (in reply to Xairflyer)
           Post #: 3426

    RE: Nitro models pusher Bobcat? - 9/3/2008 12:23:43 PM   
    HeliTB



    Posts: 1203
    Joined: 9/14/2006
    From: Fort Washington, MD, USA
    Status: offline     		XairFlyer...I saw that someone tried it in post further back. The results from what I remember is "stall stall stall"


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    Raptor v2 OS 37/Bobcat Jet OS .55 AX
    Extra 330L 25% SV26cc/SIG Kougar OS .46 AX

    (in reply to Xairflyer)
           Post #: 3427

    RE: Nitro models pusher Bobcat? - 9/3/2008 1:04:43 PM   
    Xairflyer



    Posts: 313
    Joined: 12/17/2002
    From: Co. Donegal, IRELAND
    Status: offline     		A friend has a reaper and he said it worked very well, but every aeroplane is different.

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    (in reply to HeliTB)
           Post #: 3428

    RE: Nitro models pusher Bobcat? - 9/4/2008 12:44:29 AM   
    Boomerang1



    Posts: 902
    Joined: 6/24/2005
    From: Sydney, AUSTRALIA
    Status: offline     		The pitch up is probably due to the very swept back rudder hinge line. In effect it IS acting as an elevator & would be the same problem if the rudders were deflected outwards or inwards. - John.

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    Distributor for: Nothing! So my posts can be unbiased.

    (in reply to Xairflyer)
           Post #: 3429

    RE: Nitro models pusher Bobcat? - 9/4/2008 2:56:08 AM   
    amcleod



    Posts: 26
    Joined: 7/31/2004
    From: Bridgetown, BARBADOS
    Status: offline
    quote:

    The pitch up is probably due to the very swept back rudder hinge line.

    What about mixing in a bit of ELE to compensate?

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    Angus

    (in reply to Boomerang1)
           Post #: 3430

    RE: Nitro models pusher Bobcat? - 9/4/2008 3:21:36 AM   
    cyborg1


     

    Posts: 61
    Joined: 11/24/2005
    From: Bangkok, THAILAND
    Status: offline     		I was wondering about the retract ready version, which I have. If I leave the wheel wells open (not using the plastic wheel well provided), will there be any adverse effect on flight performance? As it is, my spring air retracts don't retract completely into the wheel well, and almost half of the wheel is hanging in the breeze anyway. Which brings me to another question-can these spring air 301's be adjusted for slack? My front nose gear has quite a lot of slack when retracted, and it makes the gear hang even lower, looking like it's not fully locked in position, when in reality it is.

    (in reply to amcleod)
           Post #: 3431

    RE: Nitro models pusher Bobcat? - 9/4/2008 11:23:51 AM   
    Xairflyer



    Posts: 313
    Joined: 12/17/2002
    From: Co. Donegal, IRELAND
    Status: offline     		What I done on my AMD hawk was to slightly angle the retract so that it allowed the wheel to retract further, leg will be slightly angled back sitting on its wheels but actually helps with the tracking.

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    (in reply to cyborg1)
           Post #: 3432

    RE: Nitro models pusher Bobcat? - 9/4/2008 1:43:55 PM   
    HeliTB



    Posts: 1203
    Joined: 9/14/2006
    From: Fort Washington, MD, USA
    Status: offline     		Yeah...I kind did something similar with my retracts mounting block. I used my dremel and sanded them at slight angle so that they retract further. Also flew well with no plastic bay inserts.

    You could also bend the wire so the wheels fully disappear.


    _____________________________

    Raptor v2 OS 37/Bobcat Jet OS .55 AX
    Extra 330L 25% SV26cc/SIG Kougar OS .46 AX

    (in reply to Xairflyer)
           Post #: 3433

    RE: Nitro models pusher Bobcat? - 9/7/2008 5:34:10 AM   
    cyborg1


     

    Posts: 61
    Joined: 11/24/2005
    From: Bangkok, THAILAND
    Status: offline     		Well, finally re-maidened my bobcat. Pleased to say that it went well. Had a few hairy moments when I took off, as I adjusted the elevator servo arm to compensate for my previous flight, which required almost full up trim. Since the plane is heavier from the fiberglass repair, I added 2 clicks of up elevator just in case. Well, the plane tracked straight, and I used about three quarters of the runway for my takeoff roll. Near the end of the runway, I applied up elevator, and she shot straight up like a rocket..too much up elevator!!!!!!!!I quickly down trimmed and got her flying straight and level before she stalled. Flew the circuit for about 2 minutes, and concentrated on the landing approach. First actual landing approach bungled, went around at full throttle, and she settled in for the second approach. Spoilerons were a great help in settling down. managed to get her down safely. All in all, a great flight. Speed wasn't very fast with my 50 heli engine and tuned pipe, but I didn't really try for speed, as I wanted to concentrate on landing first. It was probably doing about 90 mph in straight and level flight with an 11X6 apc pusher. I'll try to max it out even further on my next flights. I was wondering if a 10X7 apc pusher qould be better for speed?

    (in reply to HeliTB)
           Post #: 3434

    RE: Nitro models pusher Bobcat? - 9/7/2008 2:43:57 PM   
    BillS


     

    Posts: 3077
    Joined: 9/6/2004
    From: Greensboro, NC, USA
    Status: offline
    quote:

    … with an 11X6 apc pusher. I'll try to max it out even further on my next flights. I was wondering if a 10X7 apc pusher qould be better for speed?

    My Bob Cat is 8 lbs and recently changed to an OS .50. I have two flights with 11 x 6p and 2 with a 10 x7p. It lifts off from grass with more authority with a 10 x 7p with maybe 8 to 10% more authority. Lift off with 11 x 6p was slow, scary and once at stall speed.
    11 x 6p APC turns 12,500
    10 x 7p APC turns 13,500/13,700

    In flight with 10 x 7p seemed to require less throttle although both props were OK in the air. I found more reserve power with the 10 x 7p. Will be interested in your findings.

    quote:

    10X7 apc pusher qould be better for speed?

    Don’t know.

    Additionally over a minute ground run time with a pusher seems to overheat the engine. Often the engine will sag during the take off roll or immediately after take off which is not good. I have started to crank on the runway, quickly check rpm, and go. Also I left the idle deliberately richer than normal.

    Bill

    Should have also mentioned that I have another Bob Cat that has been sheeted, glassed and painted that will be 10 lbs or more after adding engine and radio gear.


    < Message edited by BillS -- 9/7/2008 3:58:59 PM >

    (in reply to cyborg1)
           Post #: 3435

    RE: Nitro models pusher Bobcat? - 9/7/2008 6:22:44 PM   
    opjose



    Posts: 6145
    Joined: 11/26/2005
    From: Poolesville, MD, USA
    Status: online     		I fly mine with a GMS .76 and a Graupner 11x8 Pusher Prop.

    Initially I too was having overheating issues as the cylinder head is not in the air blast when the engine is running on the ground.

    A laser temperature guage helped immensly.

    I noted that the head temp at the plug was exceeding 380 degrees F which is MUCH higher than what I should see.

    So I adjusted the high end needle richer until the head temp dropped to 280-300 degrees F which was perfect.

    This is one of those things where no amount of listening or taching the engine will help. I would not have thought of it if it wasn't for a friend who offered the use of his laser thermometer. After the very first reading I know what was wrong, and within a few minutes I had the engine operating as it should.

    I'd suggest doing the same.



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    Build em'', fly em'', crash em'' and build more.

    (in reply to BillS)
           Post #: 3436

    RE: Nitro models pusher Bobcat? - 9/8/2008 1:59:02 AM   
    BillS


     

    Posts: 3077
    Joined: 9/6/2004
    From: Greensboro, NC, USA
    Status: offline
    quote:

    I fly mine with a GMS .76 and a Graupner 11x8 Pusher Prop.
    …
    So I adjusted the high end needle richer until the head temp dropped to 280-300 degrees F which was perfect.

    Do you remember the rpm at the lower temperature setting?

    First flight today was great. Second flight over an hour later was rich, rich with no change in needle setting and a disaster. Wallowed through a 180 degree turn and was about to go over the pits and parking lot when I aborted and paned into the grass out of sight and far away.

    Bill

    (in reply to opjose)
           Post #: 3437

    RE: Nitro models pusher Bobcat? - 9/8/2008 4:16:16 AM   
    cyborg1


     

    Posts: 61
    Joined: 11/24/2005
    From: Bangkok, THAILAND
    Status: offline     		I've found that using a