I've flown my Bobcat .25 extensively now... I love the plane.

Here are some tips and ideas for anyone looking at one of these..

First some pictures...

Removeable Motor Mount




It actually flew quite well with the Rimfire, but I wanted more speed...



Removable Canopy mounting system... magnets are NOT needed with this simple mount.

Package Contents





Boom mount points



Aileron Servo Doors


Fiberglass Fuselage
Note the bottom "door" re-inforcement.

Door is useful to aid battery cooling...

This might sound kind of dumb but would there be any advantage to having a flap switch on the TX make the the rudders go either full out or full in as a speed break for landing? Tried it out last night while setting up my radio. Would it work as a way to slow the Bobcat down?

Don't jump on me too hard, just thinking...

Thanks

Unfortunately because of the "angle" of the rudders, moving them out or in simultaneously has the detrimental effect of pushing the nose up or down respectively in a difficult to control manner.

I modeled this in G3 and discovered that the behaviour of the real plane was no different.

Even when this is offset by adjusting the elevator, it's not all that useful.

What seems to work very well for everyone however is to utilize the flap switch to activate "spoilerons"...

That is hitting the flap switch causes both ailerons to move up about 1/4" or slightly more, while pushing the nose down a tad.

This makes the plane much easier to control at landing and makes nose up approaches easier.

The nose up landing not only looks very scale like, but it also tends to slow the plane down far more quickly than the rudders.

Think of those videos of an F-16 or F-22 landing and you'll get the idea.

Some notes on this plane in no particular order:

- If you use an electric motor, your prop selection range opens up greatly.

Pusher prop's are not all that common, and the range of available prop sizes is a bit limited.
You often have to use a prop that may not be ideal for your glow engine.

With an electric brushless motor, you can simply reverse two of the leads to reverse the motor direction, then simply turn a standard prop around and remount it like a pusher...

- With a 3900mAh 11v battery my plane came in at 3lbs 4oz. The airframe is designed for more weight so you have a good bit of leeway when selecting battery and motor combinations. Since this is ideally a speedly "jet like" plane you want to shoot for a high WATT per Pound ratio when going electric.

- You will have to make your own battery mount from Lite Ply Balsa. I cut the former a bit where the fuel tank would go, to permit me to install wide ( or stacked ) battery packs. The front of my battery tray extends from the glow tank's "hole" all the way to the servo mounting plate under the canopy.

That way I can move the batteries back or forward to affect the C.G.

- Pictured above is my solution for a quick removable canopy mount, to permit battery access.

I could have installed two of the bars and "catches" but I find that one will hold just fine. The magnets ( my first effort ) are not required.

- Spoileron's help landings greatly.

To get spoilerons to work you must have a computer controlled radio with mixing and have an extra available channel for the left Aileron.
Typically you adjust the wing "type" in the radio from "normal" to "flaperon".

Then you adjust the radio's programming so that when the flap switch is turned on, both ailerons will move UP about 1/4" or so.

Normal left-right stick movement should remain unaffected except for the up incidence of the ailerons.

Some radios have a "landing" switch that permit you to adjust several control surfaces by flipping one switch. I use this to bring the "flaps" UP and add a bit of downward pitch to the nose.

This has to be fine tuned in flight ( while HIGH ), so that ideally when you hit the "flap" or "landing" switch the ailerons come up but the plane does NOT pitch up as well.

Unlike typical tail draggers, moving the "flaps" ( actually spoilerons ) up causes the nose to pitch UP instead of down.

More to follow...

Good work Opjose, when is your maiden coming up? I have a Falcon 25 in the box waiting on me to pick a motor.

It flew the weekend before with the RimFire motor.

The Rimfire had no problem getting the plane up in the air and it exhibited decent speed, but verticals were underwelming...

I haven't had a chance to try the pictured TowerPro motor though...

I'd have to go glow with this one.....perhaps a vintage OS 25 VFR with a tuned pipe back forward inside the fuselage, the K&B 3.5cc with the "barrel" type muffler would do, and last but certainly not least the OS Wankel with a straight pipe out past the prop!

Say Opjose, what size is the stock fuel tank, and with little or no modifications what larger size tank do you think would fit? The Wankel is THIRSTY!

Rube

I'll have to double check. I didn't install the tank so I still have it in it's plastic cover... I'll post this later.

You can indeed put a larger tank in there.

To be able to fit larger batteries I used a coping saw to open up the former a bit, which normally supports the mid-rear part of the tank.

You could simply get rid of it too, as the fuselage is strong in that area... the people who are putting in Jet Engines on the larger models do this all the time and they seem to have no problems.

You could practically double ( or more ) the size of the included tank.

Re: Pipe

On my .52 I ended up routing the exhaust right thru the wing. This has worked well.

I suppose you could do the same with a pipe too.

Happy to find this thread-

Trying to decide how to power my Falcon 25. E or glow?
What electric motor is that on the three blade? What battery are you using?

(here's another forum with discussion on e-power for the Falcon- http://www.rcgroups.com/forums/showthread.php?t=738285)

And for glow- do you have any recommendations?

thanks.

That's a 9x7 3 blade prop.

I wanted MUCH more speed on my Bobcat .25 so yesterday I flew it with two 3S 3900mAh battery packs in series to produce 22 volts.

I swapped out the motor for an 893KV motor capable of taking 22volts.

I also tried a 9x6E prop on this setup.

This increased the weight of the plane by about 5-6oz, but it still is under the glow engine weight.

On the ground the motor cannot spin as fast as the ESC is pulsing it, causing the motor to make a screeching noise and STOP at high throttle.

However once it unloads in the air, it does just fine.

The plane is a small rocket this way and I like how it flies.

I will be testing it with the 9x7x3 prop too.

---

If you want speed w/o the expense get a .30 GMS engine and put it on this plane.

It will do very well with the GMS.

Thanks. I'm not familiar with GMS- can you provide a link?
The one link I found- they're not listed as available anymore.
Perhaps you meant to find one used?

apreciate the help.

GMS Engine: [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXDXM0&P=ML]CLICK ME![/link]

While I value Opjose' opinions, I have to disagree with him on his engine choice. Spend the extra $12 and go with the Super Tigre 34-----MUCH more reliable engine with very tall thin cylinder head cooling fins that work very well on a pusher engine configuration. I've got a 40 sized Long-EZ that I swapped out an OS 46AX for a Super Tigre GS45 and the difference was night and day.
I'm also running one of the 34's on a Bridi Sun Fli 4-20 and a pair of the 34's on a twin.

I've had ONE GMS engine, it was a 75 or 76, and upon the initial running of the engine for breaking in it abrubtly stopped. I turned it over by hand and it had NO compression. Took the head off and found the piston ring sitting on TOP of the piston! Sent it back for a replacement and wound up trading it off.

Rube

I've run many different engines.

The SuperTigres do well for me, although getting that transition in the midrange right requires a bit of work.

GMS manufacturers the almost identical Tower Hobbies engines, both of which are a pretty good value for the money and well received here.

They DO require a bit more TLC during break in than say an OS or Evolution engine, but I've had very good luck with them.

I'm running the GMS .76 and TH .75 on the Bobcat .52's, and the GMS 1.20 on the Falcon 1.20 as well as a bunch of the T.H. .46's on many different planes.


It sounds like the GMS .76 that you had problems with, had a bad piston rod, or it overheated and siezed causing the rod to break.

Especially during break in, you have to be careful with this type of thing and run ANY engine overly rich.

I seized one GMS .76 on break-in, ( too lean! ) but after letting it cool for 30 minutes and richening it out, I was up and running again.

It's the one I'm currently running on my Yellow Bobcat... SuperTigre decals not-with-standing!

Flew my Falcon 25 with a new 36mm 1300 kv Medusa motor, 6s battery, and 7x5 cut down to 6.5x5. 1300 watts flew her pretty good. Here is some video of her flying. Sorry, this is all we could keep in frame with my camera that is having problems with its autofocus.

Added a nosegear door which really helps slow her down for landing.

http://www.rcgroups.com/forums/showt...84#post8490044


Tumbler

I want MORE SPEED with my .25... especially after seeing your video on a big screen.

I may rip out the electronics and convert mine over to a glow .32.

From what I've seen in the sim, there seems to be a vast performance difference, potentially hitting 130 mph+ under decent conditions with almost unlimited vertical.

Mine was clocked on one ofthe diving passes at 139mph and the inverted pass was 122mph. I think you are going to get more speed out of an electric set up because there are more prop choices.

Brian

Your probably right, but next I'm forced to purchase another motor, and maybe more batteries... to bring the speed up.

Where-as a .32 engine looks mighty cheap for similiar performance.

I don't think I'm getting over 80 mph at the moment.

OPjose.

I have the 52 sized Bobcat. Same color even. I still have yet to get around to building it. Had it for almost a year now, don't know why I haven't built it yet. Any bad habits or recommendations?

I'm going electric with mine. 1000kv Quannum inrunner, 8 cell 5000 mah lipo, 7.8 x 6 APC pattern prop. 1754 watts. On the bench it pulls 67 amps, the scale reads just over 7 lbs of static thrust. I really need to get a tach to verify this, but according to the performance calcs, that's a prop speed around 25,500 RPM, pitch speed should be somewhere around 145. Sure kicks up one heck of a windstorm with a fair amount of noise.

That's going to be a very nice flyer.

Assuming that you only get within 85% of what you are seeing on the bench, you'll still do very well.

It will be something to see.