RE: Nitro models pusher Bobcat?
 

Where can I find a BobCat-52 for sale? All I've been able to find is the BobCat-50, with 51" span.

RE: Nitro models pusher Bobcat?
 

Just curious, why would you want 52" WS instead of 51" for 100 bucks? :eek:

RE: Nitro models pusher Bobcat?
 

I don't, particularly. I just see people referring to the BobCat-52 and as far as I can determine, there is no such aircraft. If indeed there is such a model, I'd like to have a look at it, since NP doesn't seem to want to sell me a BobCat-50.

RE: Nitro models pusher Bobcat?
 

Try Texasrcplanes.com.

RE: Nitro models pusher Bobcat?
 

You are making the ( erroneous ) assumption that the 52 represents wingspan.

It does NOT.

The numbers represent the engine size used on the plane.

The Nitroplanes version - IS - the .52 Bobcat...

My NP .52 Bobcat:
http://image2-6.rcuniverse.com/e1/ga.../lg-113283.jpg


"Engine Required: 2c 0.46-0.60 cu in or 4c 0.52 - 0.70 cu in"

Most of NP models are listed by their CU displacement when using a four stroke engine with a few exceptions.

RE: Nitro models pusher Bobcat?
 

I really hate to reply b/c this thread is already too long. It took 3 weeks for me to read...please read the thread before posting.
Like opjose said, the "50" is the recommended engine size. Look at nitroplanes pictures and you will see the "Bobcat-52" sticker.

RE: Nitro models pusher Bobcat?
 

before you tear into this. maybe consider a 2 ounce UAT tank in front of the current tank, it will pressureize and milk your last bit of fuel before landing. I know a guy that did that in a keecat, and it worked

RE: Nitro models pusher Bobcat?
 

I used a 1 oz. header tank facing forward and behind the supplied tank. The standard tank faces to the rear and is vented to short fill to 8 Oz. The header tank was installed from the rear which required cutting a larger hole in the fuselage.

The fuel lines are considerably shorter. Both needles are easier to adjust. With full fuel anything over 35 degrees AOA draws only from the header tank. Working room is nonexistent and the fuel lines were difficult to plumb. After considerable ground testing (no flights) deceleration after a high speed run often shuts the engine down. Cause unknown.

Bill

RE: Nitro models pusher Bobcat?
 

When you decellerate after a high speed run the engine stops being cooled by the passing air.

You may be getting an overheating condition which is causing the engine to lean even further.

Try richening the high end up somewhat.

Also double check your fuel flow...

Does it take relatively little pressure (almost none, check with clean fuel tubing and blow into the muffler pressure line ) to force fuel out of the tank?

Remember that when you decellerate the pressure at the tank will drop suddenly, causing, even more leaning as the engine transitions to idle.

I've been through all of this... I found that I had to set the engine at least 1/2" turn or MORE richer than how I would normally set the same engine on a standard tractor plane.

That's optimum, then back out 3/4 turns or more... more than you might expect.

The engine may then seem too rich on the ground.... but it leans out just right in the air.

RE: Nitro models pusher Bobcat?
 

I'm not sure a lot of full throttle ground testing of a pusher is the best thing for your engine, it's very possibly overheating. On the header tank subject, I'll go back to what I mentioned earlier, keep it simple. Really no need for all the extra plumbing on this plane. Hope you get it all worked out and in the air. ;)

RE: Nitro models pusher Bobcat?
 

Whats the best choice of nose weight and how have you mounted/inserted it at the nose.

Plenty of room in the nose, but not a whole lot of access to get in there - so my receiver & battery are at the backside of the front LG bulkhead.

Eric

RE: Nitro models pusher Bobcat?
 

I used a long but thin Venom 1200mAh battery pack. I had no problems putting it into the nose. You could even insert two of them there... that way the weight is "working" weight for you.

RE: Nitro models pusher Bobcat?
 

Yup something I found out the hard way.

Until I understood this I had many problems trying to get the engine tuned up and trying to avoid it cutting out at run-up/takeoff.

RE: Nitro models pusher Bobcat?
 

Velcro is about the best solution for holding the battery in the nose. My battery and Rx are in the same location as yours. I only had to put about an ounce of lead in the nose of mine. I glued some sheet lead to a piece of 1/4" balsa. I reached in with a long pair of forceps and epoxied the balsa into the nose. If I ever need to get it out I can simply reach in and break the balsa loose.

RE: Nitro models pusher Bobcat?
 

While I don't know the final outcome of the concept of drawing fuel from the main tank only when reasonably level, the concept seemed sound in the beginning and it still seems sound. Also I had fun with the implementation. Running an engine in a reverse configuration does seem to require different tuning techniques.

Bill

RE: Nitro models pusher Bobcat?
 

There were a few suggestions on CG & Throw.

Should I start with the 10.3" from the front edge of the wing for CG or is there something better.

What about the throws.

I'd hate to have to re-read this all and have to pick from the posters.

Please someone chime in who flys this plane on a good flyable setting.

I'd hate to be overcontrolling and snaping or not having enough throw to bring it back in one piece.

Eric

RE: Nitro models pusher Bobcat?
 

Have 2 being deliverd tomorrow:D. Very much looking forward to digging in. A question for those of you that put the air retracts in: Most had to cut into the fuse to accomodate the wheels when the gear is pulled up. What does the idea of moving thegear further outboard on the wings and also moving the aileron servo outboard furhter seem like to you guys? If this can be accommodated, cutting into the fuse could possibly be elimintaed, yes?

I have read the entire thread (whew!!), but can't remember if I saw this addressed in here, has anyone started with the fixed gear and added the retract later? My concern is going to far with $$ on the retracts in the event this thing has a short life span (ie: midair with earth).

Thanks!

Sqidster's Dad.

RE: Nitro models pusher Bobcat?
 

Yup that is optimal.

Start by setting your high rates to the recommended throws, and your low rates to be about 65-75% of the recommended throws.

That way on your first flights, if you find things too fast or twitchy, you can dial things down, but DO NOT restrict elevator throw too much, or you will have a hard time landing the plane.


Make SURE you have a positiive angle of attack on the wings.

Also plan on putting the plane on one end of the runway and quickly running up the engine then back down again, so you can see how it responds. Do this after the plane has sat on the runway for at least a minute to double check your tuning too.

Do NOT pull back on the stick hard at takeoff. Give it as much room to accelerate as you can and then pull up gradually... ( again assuming that the AOA is positive otherwise the plane will "stick" to the ground ).

Once in the air trim the plane, then start working the spoilerons and low speed flight characteristics at high altitude. Get a feel for how slow the plane will go, and make turns. The first time it starts to wallow around on you, you will be surprised... and you are too slow.

Dedicate two runs around the field to slow speed and spoilerons, then work on your approaches and landings.

This is a fast hot landing plane ( for a propped plane ). You need to get the sweet spot for landings.

You want to get it low and let the spoilerons/nose high attitude/ bleed off the airspeed until it settles in, in a very jet fighter manner.

RE: Nitro models pusher Bobcat?
 

No, not on the retract ready versions.

This is not needed on the retract ready versions.

I would not recommend trying to install retracts after the fact. If you install the fixed gear there are gear blocks which must be put in and epoxied. These will be impossible to remove later.

If you are going with retracts, do so from the onset.

If you lawn dart the plane, it is unlikely that the gear will be severely damaged.

The biggest problem is hard landings, and if you've gone with the recommended gear sets, most of the damage is to the wing or fuselage.

I have yet to even bend a gear wire, but I've yanked the gear out of the wing twice now with bad landings.

RE: Nitro models pusher Bobcat?
 

Thanks for the quick response! Another question came to mind while reading. The Robarts, 520w1 set comes with wire gear as I recall. If I go this direction, can the wire be changed out to the shock absorber struts after the fact or does it need to be done initially and do you know what the model # is if I go with the struts instead of the wire set up?

Thanks again for a great thread and read.

RE: Nitro models pusher Bobcat?
 

Usually you have to do this from the onset.

The Strut ready gear have larger openings for the struts.

There may be some exceptions to this, but I am unfamiliar with them.

RE: Nitro models pusher Bobcat?
 

I thought that might be the case. Thanks!

RE: Nitro models pusher Bobcat?
 

Can't speak for everyone but my settings are as follows:

CG @ 10.25" from wing leading edge at fuse.

Elevator LOW rate 15mm - HIGH rate 25mm (high rate needed for landing)
Ailerons 15mm (manual suggests 25mm which in my opinion is WAY too much)
Rudders 15mm
Spoilerons 3mm (for landing)
Neutral setting of elevator - Trailing edge 5mm up from a straight edge held against flat bottom of stab.

RE: Nitro models pusher Bobcat?
 

Yup but I have mine at 35mm, and does it ROLL at speed!

Expo tones things down...

RE: Nitro models pusher Bobcat?
 

Video of my Bobcat.....flown by club president Dan.
I have a 'How Fast' airspeed instument on the plane,...but forgot to read it after this flight.
The flight before read 113.4 mph ( in a dive of course)...and 90.4 mph straight and level flight.

New O.S. 55 with only about an hour run time on it,...Springair retracts....no rudder servos,....and Hitech flat servo mounted inside stab.

Darn glow plug unscrewed itself during gear check pass.....hit the prop...ruined the prop.

http://home.dc.rr.com/maurie/Bobcat%20March%2018.wmv