RE: Nitro models pusher Bobcat?
 

New video......

I almost never get video of my planes because I usually run the video camera, anyway I'm trying to teach my son to take video for me this was a session with my Bobcat called "Where'd it go?"

We were alone at the field so I had my radio playing for him, so there is what some might consider annoying music in the background.

[link=http://video.google.com/videoplay?docid=1906584544675286481&hl=en]Where'd it go..Bobcat[/link]

RE: Nitro models pusher Bobcat?
 

If you really want to save some money on the tail servo setup, go back to page 99 and check out posts 2461 and 2468. ;)

RE: Nitro models pusher Bobcat?
 

I am selling my unassembled Bobcat for $100 bucks. PM me if you are interested or view it in the marketplace. This thing looks like a pain to build. Alot of mods!

RE: Nitro models pusher Bobcat?
 

I'll address a couple of things:

GWS servos...I dunno....saving money on the moving parts of the plane, that actually make it fly....I'd suggest that thsi is where you don't skimp to save a couple of bucks. Buy a cheaper motor instead, and use good servos.

My plane does not land hot at all using the spoilerons. Slow as a cub on takeoff... But I think OpJose is mistaken on my field, we fly off of paved runway. I don't need brakes at all now that I use the spoilers to slow down.

I flew Hal's Bobcat today. It's the non-retract version. I think it's FASTER because of the thinner wing, but it also came in and took off faster than mine, He's got the OS 55AX, but stock pipe and still using 15% - it's a great motor, plenty of power.

I also flew mine today using the Weston pipe. I like the Jett pipe much better - there was a significant difference in top end. So the Weston is going on Ebay - or if anyone wants it, $50+shipping (save yourself $25 and buy mine with 2 flights on it. Email me ([email protected] if you're interested - remember, every motor will treat a pipe differently)...and I'll mount the Jett pipe again. Time for maintenance, and especially new servo arms and control horns, as I noticed a little flutter at high speeds. On closer inspection, I realized I almost had a bad accident waiting to happen...when I ran last, I stupidly hit the retract switch on takeoff, and the plane pancaked onto it's belly (and the aileron control horns), and shaved them down pretty good. WHEW! Glad I noticed as the clevis was on thin plastic! I'll switch everything to metal now.

Well, it's been beautiful weather here - 70's and sunny - I guess this is why our club doubles in size in the winter! :)

Cya,
Mark

RE: Nitro models pusher Bobcat?
 

No not at all.

It goes together quite easily and quickly.

The mods are all optional as with most ARF's.

Re-inforcement is always recommended.

RE: Nitro models pusher Bobcat?
 

I too don't see the efficacy of installing a cross bar to save utilizing one servo. It doesn't seem to have any advantage.

However servo price does not always equate to durability or viability.

I'm using Tower Pro SG5010's on many planes, including the Bobcat which cost me a whopping $6.65/ea in lots of 20. These are 88oz+ torque BB servos.

They have been more reliable for me than say some of the far more expensive Hitec equivalents.

Yeah I've gotten a bad one or two over the 70+ servos I purchased, but these are easy and quickly weeded out. Once in place they work well.

Part of this may be me, part of it may be my spoileron settings not being high enough, but mine comes in quite hot.

I don't think I've loaded the plane down any more than you have though.

RE: Nitro models pusher Bobcat?
 

Hi Stick Jammer,

My solution was to cut the elevator in half! Each elevator servo then can't interfere with its partner. I did this mainly to ensure that the two elevator servos were not fighting each other at any elevator position.

Seams to work OK.

http://www.youtube.com/watch?v=OucKVUMAzKQ

Eric

RE: Nitro models pusher Bobcat?
 

Just like the "big boys"!

I was planning on doing this to the Falcon 1.20.

RE: Nitro models pusher Bobcat?
 

Original: opjose

Without getting into a big debate here, a fairly good $$ savings is the advantage. Two mini (Hitech) servos cost $50-$60 plus the cost of a second 36" extension and a "Y" connector if the Rx doesn't have a spare channel. The cost of one good standard BB servo is less than $20 and the cost of the complete carbon fiber tie rod assembly for the rudders is about $4. Along with a single elevator servo, the savings are quite substantial not to mention the simplified installation and Rx connections. A six channel Rx can be used without any "Y" connectors or reversing "Y" for the tail servos. ;)

RE: Nitro models pusher Bobcat?
 

I can see why you may want to do this if you need to save a channel.

But given the 30.00+/ea price per servo you are citing you would be talking about high torque minis with metal gears.

So you will end up with about the same amount of torque with a good standard size high torque servo.

That equals out pretty well.

Weight wise, things will be about the same.

The downside is that now you have the CF rod hanging in the middle between the two rudders.

As it is I have to pass my electric starter UNDER the tail after starting the plane, and the CF rod would make this even harder to do.

From a drag standpoint, it would be debateable as to which is more aerodynamically efficient, but I'd expect them to be about the same.


So I see things of equal value, and one negative point.

What am I missing that would offset the negative point?

RE: Nitro models pusher Bobcat?
 

I have a singe HS125MG mounted in the Horizontal stab. I'm using a 6V battery pack, and it's great - works perfectly fine.

BTW: Twice now I have dumb-fingered and hit the retract switch DURING the takeoff roll by accident, which Immediately retracts the gears, and causes minor prop damage and bruised pride...but I flew yesterday, and I noticed some aileron flutter during a high-speed pass (125 mph I'm guessing with the slower pipe on it)...so I quickly landed.

Upon closer inspections, I realized that the control horns had worn down as if I touched them to an electric sander (from sliding on the runway when the gear retracted)...they had worn down enough that the holes where my pushrods were inserted started to bow (ready to break)...so I just wanted to let you all know to be aware and if you do a stupid mistake like I did to really check things out!

I will be replacing the horns with something better, and at the same time, I will also replace the servo horns themselves as they are getting a bit of play in them as well. Seems like it's just the ailerons that have developed the play, but interesting that the flutter seemed to widen the hole up on the servo arm, too. I guess this is a good enough reason to switch to metal arms (on the ailerons, at least) and get rid of the slop.

RE: Nitro models pusher Bobcat?
 

The tie rod I installed is only about 1" down from the top of the rudders, not in the way of my electric starter at all. As far as things being equal, you are correct except you over looked the money savings.

Stock configuration:
(4) HS-81MG's= $88 or
(4) HS-85BB's= $100 or
(4) HS-85MG's= $124
(4) 36" servo extensions = $32
(1) Reversing Y harness = $12 (if no extra channel)
(1) Regular Y harness = $10 (if no extra channel)

Total with a 6 channel Rx would be $142 - $178
No Y harnesses would be needed with a 9 channel Rx but the total would be even higher due to the extra cost of the 9ch Rx over a 6ch

Option "B"
(2) standard deluxe servos HS-475HB's= $34
(2) 36" servo extensions = $16
(2) small control horns, (2) 2-56 ball links, 13" of CF pushrod, (2) short lengths of 2-56 threaded rod, and a little epoxy = $4

Total with 6 channel Rx would be $54

Maybe I'm a penny pincher but that's a big savings.

RE: Nitro models pusher Bobcat?
 

On mine I ended up removing the "Y" harness and just putting in one servo upside down compared to the other.

I haven't had any problems with linkage travel or binding, because I set up the control horns using right angles ( as you should ).

I purchase the extensions in bulk, so my costs were about $92.00.

I have an electric starter with a battery pack under it.

If amuses people to watch me trying to start the bobcat because of the gyrations I engage in...

RE: Nitro models pusher Bobcat?
 

Well ZACKMcOOl,,,
The Bob Cat 52 is a great way to get into JETS.. I have one with the os 46 ax and an 11 X 7 Pusher prop...Will fly fast or slow. I have no problems landing at a slow, nose up pace. Make shure you balance the cat up side down. I also put on a fibor rear gear and mounted under the eng mount. Also a longer front gear to get the nose up. Use a inverted pits and you will not have much cleen up. I will try to post some pix. ....Jim

RE: Nitro models pusher Bobcat?
 

Did you place the gear BEHIND the stock location.

If so I guess your plane doesn't actually "rotate" at takeoff, but lifts off instead. right?

RE: Nitro models pusher Bobcat?
 

Original: opjose

I assume you're referring to dual elevator servos and you have the servo arm pointing up on one servo and down on the other?
This would indeed eliminate having to reverse the direction of one servo but in doing so it creates a geometry conflict between the two linkages. This conflict may be unapparent to the eye but it is there none the less. Your setup is obviously working but typically the best setup for multiple servos on the same surface is for the linkages to be identical in length, travel, and angle at any and all positions.

RE: Nitro models pusher Bobcat?
 

I need HHHHEEEELLLLLPPPPPP!!!!!

OK, so I´ve flown the bobcat three times and it is a fast plane. I have one big problem. When the plane is facing the wind it acts very well but when the plane has tail wind it tends to fly up. I tried both ways at full speed doing the same thing and slow and still does the same thing. I don´t know what to do now.

RE: Nitro models pusher Bobcat?
 

How much of a tail wind are you talking about?

You could be approaching stall speed when flying with the wind.

It sounds like it may also be too tail heavy...

If anything it should nose down not tail down.

RE: Nitro models pusher Bobcat?
 

Got the bobcat in last night and started to work on it. The wings did not line up just right so I spent most of my time working on that. The i went to bolt on the booms and noticed that I am missing the "plastic bolts." Has anyone ells received a bobcat that was missing this part?

RE: Nitro models pusher Bobcat?
 

Zach you want to replace those with metal anyway, do not trust the plastic on the booms.

I'll do a search and see if I can find the exact size for you.

I believe the correct size is 3x30mm

RE: Nitro models pusher Bobcat?
 

If I recall correctly my Bobcat came with metal boom mount screws.

The same is true of the elevator mount screws.

All were metric.

RE: Nitro models pusher Bobcat?
 

Well the manual states 3mm bolts for the booms and 4mm for the stab but mine was just the opposite. As AGR413 has mentioned, you need steel bolts for this anyway. 25mm lengths should do, you can always cut them down if they're too long.

RE: Nitro models pusher Bobcat?
 

I used the motor mount bolts Holes with longer bolts and lock nuts, and if you look it comes out in about the same place. The stock gear is to the rear and not strong at all. This set up lets all the flex come in on the fuze. and motor mount. I used a du-bro front wire a little longer and the cat rotates just fine. With the C/G right flairs on landing good to....Jim

RE: Nitro models pusher Bobcat?
 

I believe we were talking about the tail boom mounting hardware not the motor...

Though I may be wrong as so many threads may be confusing me...

Dyslexia is a thing terrible.

RE: Nitro models pusher Bobcat?
 

I figured out how to mount the tail booms and the horizontal stab. I do have a question about the wings. I put a t-nut on the inside of the wing about an inch form the leading edge, i then have a bolt going threw the fuse to the wings. This mates the front of the wings with no gaps. As you go back on the wing one has ~1/8 inch gap at the trailing edge and the other has no gap. Is this something that needs fixing?