RE: Nitro models pusher Bobcat?
 

the byro-blaster conversion on the Enforcer has a duct about 6" long including fan housing

the D/F Enforcer pictured here is Joeflyer's

RE: Nitro models pusher Bobcat?
 

Nony,
It looks like you are right about them setting things up ahead of time. As of today it is still no record when tracking it. I also checked my credit card and it hasn't been charged yet, which is a good thing, but that also means it hasn't gone out.

RE: Nitro models pusher Bobcat?
 

Don't know if anyone else has had issues with them, but the 1 3/4" motor mount bolts are aluminum and strip very easily. I'm replacing them with steel bolts.

RE: Nitro models pusher Bobcat?
 

Had the maiden flight today. Went well. I used a 91FX with a shortened master airscrew 14x7 3-blade. I put a big 2400mah nicd battery pack in the front. It actually came out a bit nose heavy. As you see in the video the plane drops the nose after the first take-off. I actually had to use all the elevator trim. It was fun though. It lands pretty nicely. I am used to landing my zen90 pattern plane (glides forever) and that is why I keep landing at (or before) the runway. :-)

http://media.putfile.com/Bobcat-50-Nitro-Jet-

JKR

RE: Nitro models pusher Bobcat?
 

Nice video,

yah, it didn't look that fast, I agree you need a higher pitch prop, that .91fx should be faster. Judging the two, My my tower .75 and 11x7 is a lot faster but probably can use an 8 or 9 pitch as well. I think the problem with the .91fx is that it is too much engine and you can't get a big enough prop to justify the HP on this airframe. You are spinning your wheels (props) with no results on the bigger HP engines. I think this airframe is at its limit with a .75. Retracts will help with the airspeed but more pitch is still necessary. Maybe the OS .55 will be the better engine. It's too bad Nitromodels can't make their own bobcat 11x9P prop for this one. Hey APC, there is a market here!

RE: Nitro models pusher Bobcat?
 

it looks like it would work better on take off and landing if the back wheels were moved up closer to the CG. i moved mine just behind the CG, but haven't gotten to fly it like that yet. like it was it was a real beast when taking off. i fly from a grass field and you really have to get on it to get enough speed and then it leaps into the air. i have a rossi .81 ducted fan engine with a llx7 apc and it really screams.

RE: Nitro models pusher Bobcat?
 

91fx isn't a high rpm engine. You will need at least a 10 pitch prop to use the power of that one. A piped Super Tiger .75 would be a better bet.

RE: Nitro models pusher Bobcat?
 

I have 3 of these, and all three arrived at my work before the card was charged. So don't worry about no shipping info. I finally figured out to just wait and it will get here. I am also using a .91fx, and you really need a higher pitch prop for that engine. Bob

RE: Nitro models pusher Bobcat?
 

Thanks B58. I was just surprised to see anything like that from them so early, since the web said shipping the 21st.

jrosaker, nice video and congrats on the successful maiden....

RE: Nitro models pusher Bobcat?
 

Bluemax,

I started with a 10x7 APC pusher, LHS ordered in 10x8 for me. I seemed the 10x7 was over revving. the 10x8 I did not get a chance to really wring it out major temp change required mixture to be reset and then fuel system started to send bubbles. Now fall is here, flying has ended as I go hunting after work

I am getting a new tank to install and spring air retracts for next season.

C4F

RE: Nitro models pusher Bobcat?
 

You can email them ...they will respond. Nitroplanes seems to be pretty decent to deal with. A reasonable product, well packed, and very cheap! The only complaints I have noticed have been when they are out of stock!

RE: Nitro models pusher Bobcat?
 

Here's some exciting news I found on the Wren site:

http://www.wrenturbines.co.uk/galler...mbs/tb_168.jpg

RE: Nitro models pusher Bobcat?
 

I use the 91FX on a pattern plane with a 15x8 prop with great result, but the specs says that the rpm range goes up to 16000rpm. Isn't that high rpm? How is this engine timed? For high or low rpm? I haven't tacked my engine yet, but I guess it is getting close to 16000rpm with the MA 13.5x7 3-blade. If anyone else finds a higher pitched prop for this engine let me know.
JKR

I will probably install retracts soon. I will move the retracts closer to the cg. I think that would make the take-offs better.
JKR

RE: Nitro models pusher Bobcat?
 

I just found a better prop for the 91 fx:
http://www2.towerhobbies.com/cgi-bin...&I=LXAPX5&P=ML
I will just have to make it around 13.5 inches long and balance it.
JKR

RE: Nitro models pusher Bobcat?
 

I believe the 91 FX is tuned to run right around 10k. While it won't blow apart at 16k it doesn't perform very well there. Look at the Tower listing for this engine, you will see the tested props keep it right around this range.

RE: Nitro models pusher Bobcat?
 

If you have an older engine with a two piece crankcase (OS 60 comes to mind), you can rotate the carb around 90 degrees, and the engine will be timed to run in reverse...then you have an unlimited selection of props to choose from.

RE: Nitro models pusher Bobcat?
 

Maidened my Bobcat today.

My setup is as follows:

Motor
OS 55ax motor w/APC 11x7 pusher prop.

Radio
Used a single HS125 in the stab for elevator control.
2 HS125's for rudder. The rest are 3004's.

Modifications
Assembled as single piece, no assembly/disasssmbly required/possible. Sealed all joints with clear silicon seal.
Drilled holes in front of and behind the main gear mounting blocks and poured 5min epoxy in to strengthen due to reported weakness in this area (tested real good on 2nd landing!)
Glued horz stab to vert stabs + epoxied wing in place.

Balance
10" from wing LE, had to add 4oz of lead to nose with battery and receiver at front nose gear bulkhead.

Weather Conditions
60 deg. Winds 15 gust to 26mph (!) varying from 45 deg cross wind to straight down runway.

Motor Notes
Motor was brand new. Ran 1 tank of fuel through it per OS instructions on the ground. At end of first tank it had a nice very low idle, excellent transition and plenty of power at the top end. Lots of prop noise. Could probably switch to an 11x8 prop, but don't think it's needed. Prop clearance was about 1/2" from the ground, maybe 3/4".

Take off
I left plenty of room for TO due to reported long TO rolls and jumping off the ground behavior. I installed the nose gear at maximum height possible to give a positive AOA on the ground. Ground handling is fine, no tendancy to tip and tracked very well (even in the high winds). Take off roll was uneventful. Took maybe 100-150'. Rotated nicely and did not jump off the ground. 2nd take off was shorter (75-100'). Don't know how much the wind effected it, but it was smooth and not suffering from the jump into the air syndrome.

Flight
Needed about 3 or 4 clicks of nose up trim. I think it needed it more due to the design then the balance. The plane has a nice flat glide profile at low speed and is not too pitch sensitive, so I figure the CG should be just about right.
Stalls were gentle at a very low airspeed. It didn't appear to break consistantly to left or right, but would rock slightly before it happened.
I was flying the pattern with another guy flying a 424 class Q500 pylon racer. He had competed with it the previous weekend at our field and it was competitive in speed with the other 424's running. The Bobcat's speed was identical to the 424, he could not pull away until we had to turn and I wasn't willing to test the highspeed stall capacity on the first flight.

Landing
Considering it was blowing over 20mph, it was pretty solid on approach. I had a gust blowup just as I was getting into ground effect and ballooned it on flair, so I went around. The next landing approach was smooth. On my 2nd flight the glow plug came loose and popped out as I was headed upwind, low and highspeed. I was above the beginning of runway when the motor quit. I had checked the plug after the initial ground run-in and tightened it a hair, but did not check it after the 1st flight. Anyway I was headed into a strong wind, deadstick with about 500' to slow it down and land. Needless to say I was too low to turn and did not want a 15-26mph tailwind to make the landing interesting by turning downwind. So I landed straight ahead. Held it up as long as I could then touched down at 30-40 mph. No bounce just a smooth and solid highspeed touch down. The result of the landing was the mains bend back an inch and the nose gear bent to the side about the same amount. Bent them back into shape. No other damage noted. Didn't have another glow plug, so I ended the day.

Everyone at the field thought the plane looked and flew great. They were amazed at how fast/slow it could fly and it's gentle stall. The OS 55AX rocks. I'll chock the glow plug loss up to a new motor and me not wanting to overtighten it. I usually torque the plug tighter then I did this time.

Bud

RE: Nitro models pusher Bobcat?
 

I have a brand new never mounted in a plane Nelson Sport 50. that would be perfect for this plane, it has a throttleable ST carb and is not of a racing setup. Prop range in the instructions state 11k-14k rpm range 11-7, 12-8 prop range 15% fuel. paid over $400, it getting close to christmas and I just might entertain highest offer............

fwiw, I have'nt burned nitro in 3 years, no plans too, I can get to 125MPH+ with electrics and kero...............

RE: Nitro models pusher Bobcat?
 

Thanks for that excellent report, gehr2box. Did you mount the main gear as per the plans, or did you rotate them to bring the wheels closer to the cg? On landing, was there any risk of the prop hitting the ground as you flaired??


now, having read everyone elses contributions to this thread, it is time for me to start contributing as well... I think that the 55 AX would probably be the engine of choice, but as I have a 46FX sitting here doing nothing, I am using that, and taking the "keep-it-light" road.

With that in mind, and not being too keen on the elevator servo setup, I started by installing the servo right in the stab. My first choice was the 5125 digital wing servo, but I found the 85MG would fit as well...same 42oz of torque and a couple of grams lighter. I used a Hobby Lobby servo hatch and it literally fell into place.. I also found that the 85MG's would fit in the rudder servo holes as well. So, I figure that using 3 mini servos instead of 4 standard servos saves a little over 4 ounces right in the tail, and that will also reduce the balance weight needed.............

RE: Nitro models pusher Bobcat?
 

Thanks. The gear is mounted per the instructions with the wheel end to the rear. A far as danger of the prop striking the ground on rotation, I can't see any scuffing on the blade tips. I fly off of grass.

RE: Nitro models pusher Bobcat?
 

Congrats Bud on the maiden and thanks for the report.


Great idea Nony using the HL servo hatches..

RE: Nitro models pusher Bobcat?
 

So you've got 1 HS85mg on the stab? Hopefully that is enough, should be I would think.. I've got it setup the trad. way with 2 85mgs on the stab, 1 85mg for each rudder, 1 225mg on each aileron, and a hitorgue car servo on the steering. 2 4 cell nimhs (about 3100mah) packs in the nose for balance with a tower .75 as the plant and batt to fly all day, I tell you I wrench on this thing just to see what it can handle. For testing, I do full throttle snap rolls, come into a straight dive and yank the sticks. I couldn't do anymore stress on this airframe,. I've got removable wings, stabs and just temp. clear tape the wing gaps. time for retracts on the next one.

Bud, nice to hear the 0S.55ax works for you, I've got one but put it in my lancair, broke in the engine, started instantly and idle flawlessly right out the box without adjustment, I'm very impressed thus far with this engine, very nice workmanship on it. Will maiden the lancair this week, may try it on the bobact but the tower .75 works great for now.

RE: Nitro models pusher Bobcat?
 

Ya that 55ax is a sweet motor.

We had somebody maiden one of the KeeCats this week with a ST-75 for power. I didn't see it fly, but one of the other guys said it was really underpowered. Anybody else seen a KeeCat in action?

Bud
(for Pete's Sake :) )

RE: Nitro models pusher Bobcat?
 

Yes, one 85 mg on the elevator.. It is not a very big surface and deflection is limited by the bevel on the front of the elevator. 42Oz should be more than enough...on top of that I only have a 46 blowing air over it.........

RE: Nitro models pusher Bobcat?
 

Dragon,

Are you using the nylon bolts on the tail booms, have you had any trouble?