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Nitro models pusher Bobcat?

Old 04-17-2007, 10:31 PM
  #1526  
thebluemax
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Default RE: Nitro models pusher Bobcat?

Thanks Bob for the pictures. Looking at these I see and understand what you did.

thanks again....
Old 04-17-2007, 11:26 PM
  #1527  
dragonpilot
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Default RE: Nitro models pusher Bobcat?

Very nice job on that install. I'll do that method on my next one. I did the quick version for this one with pull pull steering.
[link]http://www.rcmachinery.com/noseretract.JPG[/link]
Old 04-18-2007, 07:10 AM
  #1528  
PointMagu
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Default RE: Nitro models pusher Bobcat?

Nice job on the nose gear install. Sure looks crowded up front, lol...

Just a thought on fiberglass fuselages, cowlings and the like. Every 90 degree cut that I've ever made has resulted in stress cracks forming. I've learned that by rounding out all cuts, I eliminate this annoying tendency.

I would certainly think that on a high-stress area such as a nose gear cutout, this would be very likely to happen.

All it takes is a small sanding drum on the Dremel to insure a long lasting finish.


PM
Old 04-18-2007, 07:22 AM
  #1529  
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Default RE: Nitro models pusher Bobcat?

ORIGINAL: rhklenke
jets look silly with fixed gear
Yep, but doesn't impact on the speed with a MW44 Gold behind it

I think jets look funny with props!

Dry weight 3.5 kg, thrust over 5kg.......Beauty!

Mine balanced at 10", flies real nice.

Landing gear bends like a banana on our grass strip.[:-]

Takes off in less than 30m from grass. with no flaps, Comes in nicely through the trees too.

Thanks to Jules for photos and ground crew!
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Old 04-18-2007, 07:23 AM
  #1530  
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Default RE: Nitro models pusher Bobcat?

Couple more..
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Old 04-18-2007, 07:27 AM
  #1531  
Stick Jammer
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Default RE: Nitro models pusher Bobcat?

There is a 3/4 of an inch difference between the top and bottom. I measured from the back of the bulkhead for the nose gear to the rear end of the bulkhead where the servos mount. The bottom was 8 1/2 inches while the top was 9 1/4 inches. So it is worse than I thought unless I am missing something.
bluemax,
That doesn't seem right. If you are referring to the former where the stock nose gear would normally mount it can't be that far off. The stock nose gear block bolts directly to this former which puts the wire pretty much 90 degrees straight down. Maybe you got a Monday or Friday version.
Old 04-18-2007, 07:32 AM
  #1532  
Stick Jammer
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Default RE: Nitro models pusher Bobcat?

I agree with PointMagu on the sharp corner cut-outs. Usually not a good idea on any material; plastic, fiberglass, or metal.
Old 04-18-2007, 07:39 AM
  #1533  
Stick Jammer
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Default RE: Nitro models pusher Bobcat?

Landing gear bends like a banana on our grass strip.
J.F,
Looks like the nose gear spun on ya in one of the pics. File flat spots on the wire and use some Loctite on the set screws. Looks good except for that darn green anti-glare! What servos did you use in the tail?
Old 04-18-2007, 10:30 AM
  #1534  
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Default RE: Nitro models pusher Bobcat?

I didn't put carbon tube over the standard push rod on the steering rod so it bent and turned on landing. Suprisingly it didn't flip and remained completely upright and stable, incredible!
I used 2 of HS225MG's on the elevator and 2 of HS85MG+ on the rudders.
Didn't have to add any lead for balance either, though i do get a very small bit of trim change through the flight 'cause of the amount of go-go juice on board, but its only small.

J
Old 04-18-2007, 09:17 PM
  #1535  
thebluemax
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Default RE: Nitro models pusher Bobcat?

Stick Jammer,
It is definitely a Monday or a Friday version, not only is that way off. the one landing gear block was never drilled out and the marks on the fuse for the retaining rod were off. I will try Bob's method of mounting the nose gear as the bad angle on the nose gear bulkhead should not impact anything. I hope....

Old 04-19-2007, 06:42 PM
  #1536  
Stick Jammer
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Default RE: Nitro models pusher Bobcat?

Yeah, one of my landing gear holes wasn't drilled either but it didn't matter as I cut open the wings and built my own blocks side to side and reinforced them the way they should be. That sucks about your nose gear, I thought the motor mount idea was pretty clever.
Old 04-19-2007, 06:47 PM
  #1537  
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Default RE: Nitro models pusher Bobcat?

Original: J.F

I didn't put carbon tube over the standard push rod on the steering rod so it bent and turned on landing.
Hmmmm........I just used a length of 2-56 plain rod and now I'm re-thinking that choice. [sm=71_71.gif] I'm surprised it bend the rod that far and didn't strip the servo. Anyone using a servo saver on the nose gear?
Old 04-22-2007, 09:42 PM
  #1538  
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Default RE: Nitro models pusher Bobcat?

Greetings everyone! I first would like to thank all of you for posting such detailed information about the BobCat. I've just finished mine and will maiden it tomorrow, and I have to tell you, I feel very confident because of all the great info posted here. I'll include a couple of photos, particularly of the unique exhaust routing that my turbine jet buddy came up with to keep all the goo below the plane and off the servos in the tail.
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Old 04-22-2007, 10:45 PM
  #1539  
GSK
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Default RE: Nitro models pusher Bobcat?

Looks the part can I suggest that you reverse the rear undercariage legs

If you leave where they are now you will have a lot of trouble getting the model off the ground, in fact it could leap into the air and stall if you are not careful,
you really need to have those rear wheels closer to the C/G so that It can rock a little on the rear wheels

They do fly well with no vices as long as the C/G Is correct
cheers G.
Old 04-23-2007, 12:12 AM
  #1540  
dragonpilot
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Default RE: Nitro models pusher Bobcat?

ORIGINAL: GSK

Looks the part can I suggest that you reverse the rear undercariage legs

If you leave where they are now you will have a lot of trouble getting the model off the ground, in fact it could leap into the air and stall if you are not careful,
you really need to have those rear wheels closer to the C/G so that It can rock a little on the rear wheels

They do fly well with no vices as long as the C/G Is correct
cheers G.

To this day, the posts about the bobcat with the stock gear setup "leaping" into the air baffles me. Adrians, your gear is fine where it is.

If you Bobcat is "leaping" into the air, you are doing one or two things wrong.
1. you don't have a inclined AOA, basically, your nose wheel strut must be long or set high enough to produce a decent wing angle of attack. Remember this is not a trainer prop plane, it is a delta wing configuation.
2. you are not building enough speed up on takeoff. Again, it's not a normal prop plane. if you have an positive angle on the wings, the bobcat will gently lift off the ground with little elevator input depending on the angle. It will not "leap" into the air unless you jam on the elevator, a common pilot mistake.

Lastly, another reason you should not reverse the gear struts is that you need rearward clearance for the prop. They are wire struts and will bend upon a hard landing should you have one and then ruin your prop if it hits the pavement. Some props get fairly close to the ground clearance. This may happen over time anyway as well as the struts weaken.

Go fly, have fun.. let us know how it goes.

Leave the struts, they are fine where they are.

Old 04-23-2007, 12:20 AM
  #1541  
AGR413
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Default RE: Nitro models pusher Bobcat?

Another vote for not messing with the landing gear, if your CG is right and you make the nose gear strut as long as possible it will not leap into the air.
Old 04-23-2007, 04:36 AM
  #1542  
XJet
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Default RE: Nitro models pusher Bobcat?

There are benefits to not setting up the plane with a positive AOA while it's sitting on the gear...

If your noseleg is too long then the plane is far more inclined to bounce on a *fast* landing -- because it *will* touch down before the mains and thus force the nose to pitch up -- with resulting ballooning back into the air.

A shorter noseleg will ensure that once you touch-down, even if your landing speed isn't *perfect*, it will stick - because once the nose drops there will be no lift (or maybe even a little negative force).

If you can do a perfect two-pointer every time then a longer noseleg and rearward mains will work just fine -- but if you're an average flier (and especially if operating from tarmac) then the shorter noseleg and repositioned mains is a far safer option.

And, as for the prop-strike risk -- if you're worried about this, just put some wire anti-rotation legs on the bottom of your tailbooms so they limit the maximum AOA while on the ground -- I've seen plenty of (baby) boomerangs with these fitted and they don't even have a prop to strike :-)
Old 04-23-2007, 11:08 AM
  #1543  
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Default RE: Nitro models pusher Bobcat?

Well we flew it today and the only trouble we had with the gear was that it twisted inside the block causing to take on a "semi retract" sort of configuration. Took it over to my friends shop and we have some fiberglass reinforced epoxy lining the blocks now on the inside and it has stiffened up the gear trememdously. My friend flew all the takeoffs and landings, I'm a tail dragger pilot and have to get used to three wheels again. It's been a while, and since it was the maiden flights, I wanted someone who knew what the heck he was doing. I could use some advice about the darned receiver antenna wire as to the best routing. You can see by my pictures how we addressed it, but we took some strong hits today at the field (only two other flyers out there and they were on Spektrums) so I"m not sure our arrangement is best.


ORIGINAL: GSK

Looks the part can I suggest that you reverse the rear undercariage legs

If you leave where they are now you will have a lot of trouble getting the model off the ground, in fact it could leap into the air and stall if you are not careful,
you really need to have those rear wheels closer to the C/G so that It can rock a little on the rear wheels

They do fly well with no vices as long as the C/G Is correct
cheers G.
Old 04-23-2007, 11:13 AM
  #1544  
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Default RE: Nitro models pusher Bobcat?

We did have some ballooning issues but mostly it was because the rates were dialed in a little high (5 1/2 rotations per second on a roll) so when we dialed it down it was more docile. It does require me to put a little more effort into turns because I'm used to flying a 60 size Ultra Stick and a UCanDo and they are both tail draggers. This thing is also quite a lot faster than anything I currently fly so again, a little learning curve to conquer here.


Bruce


ORIGINAL: XJet

There are benefits to not setting up the plane with a positive AOA while it's sitting on the gear...

If your noseleg is too long then the plane is far more inclined to bounce on a *fast* landing -- because it *will* touch down before the mains and thus force the nose to pitch up -- with resulting ballooning back into the air.

A shorter noseleg will ensure that once you touch-down, even if your landing speed isn't *perfect*, it will stick - because once the nose drops there will be no lift (or maybe even a little negative force).

If you can do a perfect two-pointer every time then a longer noseleg and rearward mains will work just fine -- but if you're an average flier (and especially if operating from tarmac) then the shorter noseleg and repositioned mains is a far safer option.

And, as for the prop-strike risk -- if you're worried about this, just put some wire anti-rotation legs on the bottom of your tailbooms so they limit the maximum AOA while on the ground -- I've seen plenty of (baby) boomerangs with these fitted and they don't even have a prop to strike :-)
Old 04-23-2007, 11:44 AM
  #1545  
scoobystig
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Default RE: Nitro models pusher Bobcat?

ORIGINAL: Adrians flyer

I could use some advice about the darned receiver antenna wire as to the best routing. You can see by my pictures how we addressed it, but we took some strong hits today at the field (only two other flyers out there and they were on Spektrums) so I"m not sure our arrangement is best.

hi mate check my picture below, i mounted a whip aerial on the front bought from Motorsandrotors.com.

i have had 5 flights now with not even the tinyest of glitches, i am on PCM1024 though

in regard to the undercarriage i have had 5 flights from a bumby grass strip with no problems and no sign of it leaping in to the air

CofG bang on 10inches from leading edge

steve
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Old 04-23-2007, 01:02 PM
  #1546  
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Default RE: Nitro models pusher Bobcat?

I finally opened mine this past week. Opened it on Tuesday, flew it on Saturday. It went to gether very quickly. I used a SkyShark 50 electric motor with their ESC and a 5 cell pack. Bent the landing gear forward 2 inches, set the CG at 9.75 inches and set the nose gear a little high to give it a positive angle for takeoff. She took off with no problems. Handled beautifully in the air, and the 50 is plenty of electric motor for this plane using a 12x8E prop. I am satisfied since this was my first glow to electric conversion and it went very smoothly. I did not use the stock setup, but put a 125MG servo in the horizontal and two smaller Hitecs in the booms for the rudders.
Not a bad plane for the money and it looks great in the air.
Tommy
Old 04-23-2007, 09:25 PM
  #1547  
Stick Jammer
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Default RE: Nitro models pusher Bobcat?

Original: Adrians flyer

I could use some advice about the darned receiver antenna wire as to the best routing.
Go back to page 55, post 1369.
Old 04-23-2007, 09:45 PM
  #1548  
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Default RE: Nitro models pusher Bobcat?


ORIGINAL: Stick Jammer

Original: Adrians flyer

I could use some advice about the darned receiver antenna wire as to the best routing.
Go back to page 55, post 1369.

DEANS MINI WHIP
Old 04-24-2007, 08:02 PM
  #1549  
dragraces
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Default RE: Nitro models pusher Bobcat?

5 More flights today gettin the hang of it no bad habits 2 report
46fx
10x7 prop
C.G. 10.5
DEANS MINI WHIP

STILL NEED A CANOPY

HEY NM MARK U EVER TRY THAT 11X6 PROP ??

STICKJAMMER U FLY YOURS YET????????????????
THX
JASON
Old 04-24-2007, 09:06 PM
  #1550  
Wayne22
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Default RE: Nitro models pusher Bobcat?

Any guess on the speed with the 46??

I'm starting with a 10-6 3 blade grish, which I have used before and know works very well, but I am not expecting any great speeds out of it..i plan to got to a 10-7 or 10-8 after a few flights.

Too much mud to fly yet, though



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