Question:

I just got in a NP Falcon 1.20 retract ready.

I am planning on installing the Robart wire retracts.

How do you normally hook up the front wheel servo to the fron wheel control arms?

e.g. how are you doing it on the Bobcat 50, knowing that the gear needs to move back into the well?

Hi guys,

Just got one of these things and was curious what is the best retract setup to use??? Robart? Spring air?..... Which ones 100, 200, 300?

Thanks!

NP

Terry,

You aren't kidding. I had this engine on a bi-plane using a pitts muffler and it feels like half of the power is gone... unbelievable.

Mark

Hi,

Got my Bobcat set-up ready to go:

Jen 57 with CVEC pipe
Futaba 3004's in ailerons and throttle/nose steering
SD200's in the tail section

Modified the wing to take captive nuts just before the small metal rod and put nylon bolts/washers from the inside of the fuselage. I still have a slight gap at the trailing edge, I think the metal wing tube is a little big and might sand it down.

Has anyone flown with the wings fastened in this way or do you suggest glue?

I've run the engine up with an 11 x 7 APC pusher. It sounds a little noisey close up and we have a restricted of 80db at our club. I see a lot of people talk of Zinger props, will a 11 x 10 or 12 x 6 give me a quieter aircraft?

A fellow member told me that they allow an extra 2db for pushers because of the way the noise disperses and is quieter once airbourne?

All up weight is about 6.6lbs, no extra weight added just the battery pack (2100mah) shuvved up front.

Oh and I forgot a nice little tip for those with computer trannies.

If you plug all the servos into separate channels you make use of mixes.

I've got a mixes on rudders and elevators.

The useful one I put on the nose wheel steering using rudder as master and wheel as slave. You can assign it to a switch so the nose wheel doesn't move in flight.

Jason

[quote]ORIGINAL: wildswan

Modified the wing to take captive nuts just before the small metal rod and put nylon bolts/washers from the inside of the fuselage. I still have a slight gap at the trailing edge, I think the metal wing tube is a little big and might sand it down.

Has anyone flown with the wings fastened in this way or do you suggest glue?

I've run the engine up with an 11 x 7 APC pusher. It sounds a little noisey close up and we have a restricted of 80db at our club. I see a lot of people talk of Zinger props, will a 11 x 10 or 12 x 6 give me a quieter aircraft?

Hi
The wings will be fine built the way you have done It , the tail booms tend to pull the wing away from the Fuzz when tightened up sometimes
the front bolts will hold It together nicely, It is not meant to be glued Together .
OS 50 turns the 11*7 prop at 13300 on the ground and runs at 96 to 100 Decibels , so you may have problems with the Noise factor
I have done all I can to get It lower but to no avail , speed sits around the 150 to 170 K,s so It Is not a high speed machine Unless you put a turbine on It going By past posts
Before you assemble it check to see how far the alum spar goes Ito the wing , you do not want It to go further Into one wing more than the other , which might present a problem if One end is not supported properly by the wing ribs .
just my observations
Cheers G

Thanks GSK,

Have you flown yours yet?

Appears to have plenty of power taxing. One thing I noticed on a gusty day is the thing flips over if the tail is side on with the wind.

Jason

Had heaps! lost track now after 70/80 flights , yes you have to take It easy when turning while taxiing , got a scuff on mine when flying of a tarsal airstrip, but If you read previous posts you will see how I have the muffler setup also , that system works well, but still noisy ,had heaps of stick from the guys about that , but a few of them have got them now also .
Cheers g

I am writing this in hope someone has an answer. I have a Nitro model Bobcat which is electrified. A friend had one with glow and it went in. It went the entire length of our field and went straight vertical and was uncontrollable. Has anyone experienced this and do you have an answer to the cause? We feel the problem might be the CG but can't get a definite answer from Nitro. No one there seems to have any technical answers. The mains were too far back and they were moved forward closer to the approximate CG. Also the horizontal stab was changed out to a flat stab since an aeronautical engineer in our club felt a lifting stab would keep the nose from rotation.
I was told by John of Nitro that a user of username OPJOSE is an expert on this plane. Hopefully I will get a response from same. E-mail me at [email protected]

Thank you RCPULLER

Heh, Expert? Not by any stretch of the imagination!!!

However I'm trying to help them out by writing a better manual for this plane and the Falcon 1.20 as well.

I have a few of these to play with so I'm going through the different interactions. I have over a dozen NP ARFs as is.


It sounds like you had the Nitro Models Bobcat .50. Is that correct? Did you get the one that is retract ready?

As posted here, the C.G. should be set to approximately 10.3"-10.5" from the leading edge of the wing at the wing root.

The plane will fly with the gear as it comes, but it is important to make sure that the attitude of the plane at rest on the ground has a positive incidence relative to the ground. If you don't do this the plane will not lift off the runway at run-up.

There was no need to change out the stab as you've done. Many here have flown it as is.

uncontrollable sounds to me like the plane abruptly rotated and caught the pilot off guard. Since you modified the plane, I do not think any of us can help you other than to suggest you put the original stab back on, put the gear back in the stick position, use the suggested CG and keep a positive angle of attack by raising the nose gear a bit.

Sounds like the COG was wrong. I have a corrected manual that is printed and not scribbled on.

Won't the flat stab change the CG?

do you really need the rudder? can i just installed them in a fix position or i have to go with the dual rudder servo installation?
fernando

Interesting question, having done a bit of flying with the Bobcat I would not bother with Rudder If I built another . I would just fix them. They have little affect from my observations
Interested In what others feel about this.as the cost of two servos is a big saving

Cheers G.

My friend Serge and I both bought our Bobcats at the same time, I installed rudder servos, he did not.
The only time I used rudders were on landing,...to help line up the runway. Winds are usually straight down the runway at our field, so I found I didn't really need the rudders, so I removed the servos, and fixed the rudders. I also have the elevator servo inside the stab now, so plane is alot cleaner (and faster) without all those servos hanging out there. I would say, if your field is not prone to strong cross winds,..then don't bother with putting rudder servos on.

What about knife edge flight? Or, was the Bobcat incapable of KE flight with rudders?.

Texan,

The rudders are very effective. However, if you don't use them, you don't need them to fly this plane.

Mark

My Bobcat 50 won't knife-edge (with an ASP52 pushing it along).

One of the problems is that there's only a single-bevel on the rudders so the throw is somewhat limited.

As others have said -- they're fine for keeping the nose straight in a cross-wind landing but other than that the rudders are not essential. If I didn't have any servos suitable, or if I had a CG problem I'd just leave them out.

My Bobcat is still flying real funny though.

At low airspeeds it wants to climb like hell -- needing about 1/3 down elevator to stop it going vertical if you open the throttle to full during an overshoot (for example).

Once it gets flying speed up though, it wants to tuck under.

It's also mondo-sensitive to elevators on the approach (to the extent that getting the flare right is more luck than skill). However, if you reduce the elevator throw it runs out of authority in turns and when pulling out from steep power dives. The servo on the elevator is rated at 3.5Kg/cm (45oz/in or so) which should be plenty-strong so I don't think it's blow-back causing the problem.

These are symptoms of a rearward CG but mine is right on 10.5 inches from the LE as recommended. I'll try some lead in the nose and see how it goes.

Right now, at 2/3 throttle it flies straight and level with the elevator perfectly neutral relevant to the tailplane and dives when rolled inverted, needing about 1/3 down stick to hold the nose level.

We had a radar gun at the field on the weekend and my Bobcat was only good for just over 100mph. My (slightly modified) trainer is good for more than 110mph so the Bobcat isn't exactly as fast as I'd hoped.

Xjet,

Check the thrust angle of your engine. Mine will knife edge easily although it does tuck a bit. I can hold the nose high for the entire landing approach. Pretty much don't need need to flare when it is in this attitude. I do hold almost full up on landing it could use a touch more for comfort.

Mark

One more thing, I am using 10" props. I do not know if the prop wash from larger disks will upset the stab.

I didn't get a chance to maiden mine this weekend but Hope to next Saturday. I built my mount out of aluminum since I would have had to modify the stock mount to make my Tower Hobbies .75 fit any way. I intend to try some shims to alter the thrust angle if I get similar problems as the ones I've heard here. I will report back after I've tried it.

Blessings, Terry

Terry,

I had to change to aluminum as well. The wood would compress and I ran out of space to tighten any more. No shims necessary to date.

Mark

Hi Mark,

That is good news about the shims. I wanted to fly mine this past weekend but by the time I got my nerve up the wind had kicked in. We have a very bad cross wind problem at our field. I saw a guy fly his a couple of weeks ago and it tipped sideways during his take off. Fortunately with the pusher design it didn't hit the prop but still scuffed the wing. I figured I would wait until I have good conditions before I try mine. I have the retracts model and I think the rear gear is spread farther part than the non retracts model so maybe it won't be as susceptible of tipping.

I thought is was strange that they chose Balsa for the engine mount. I figured it would just be a matter of time before it would compress.

Blessings, Terry

I'm pretty sure it's not the thrust angle -- it's 100% stock at the back and when I "punch" the throttle at low speed it briefly responds by pitching down slightly before then pitching up sharply. It looks as if the thrustline tries to push the nose down but then something else takes over and the nose pitches up very strongly.

Still a ball to fly though -- just requires a lot more attention to the sticks than other people's bobcats seem to.

Please post photos from the side, back and front. Take from a distance so we can see the alignment of everything. The plane shouldn't pitch at all. Is your engine bolted tight?