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Nitro models pusher Bobcat?

Old 01-13-2007, 03:51 PM
  #926  
Larry Legg
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Default RE: Nitro models pusher Bobcat?

Would it make scense to position the tank right at the CG? That way full or empty the CG remains consistant...or am I missing something.
Old 01-13-2007, 05:03 PM
  #927  
PointMagu
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Default RE: Nitro models pusher Bobcat?

I have my 24 oz tank dead on the CG of my Goldberg Sukhoi.

I concour: empty or full, placing it there has -0- impact on balance. I never considered this on the Bobcat but after reading your posting, I too will be placing the tank forward abit, lol...

PM
Old 01-13-2007, 06:26 PM
  #928  
Larry Legg
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Default RE: Nitro models pusher Bobcat?

Angus,

Great craftmanship!

Please continue to post more pictures of your build. I want to learn from a master.


ORIGINAL: Angus McDonald

I removed most of the underside and built up some of the spars as well as add another one. Then I glued in a mount for the retracts similar to a flex plate. I moved the servo well over for the ailerions. When I pulled off the balsa sheeting to remove the existing mounts and do the build up, I sure noticed the poor and lack of gluing done inside.....I'm not sure if I would put a turbine on one, it's going to give sooner or later. Anyway I re-glued everything and did full sheeting so I can glass it.

Angus
Old 01-13-2007, 08:16 PM
  #929  
AGR413
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Default RE: Nitro models pusher Bobcat?

I highly recommend flying the Bobcat and fine tuning the set up before anyone considers moving the fuel tank. I am finding that the "real" nuetral CG is closer 11" aft of where the leading edge meets the fuselage.

There have been many posts talking about the need to increase elevator throw, I now believe this is due to forward CG. I moved my CG back from 10.3 to close to 11" by removing .75 oz of lead from the nose. The elevator authority is much better and the plane is still slightly nose heavy based on analysis in flight.

The more I fly the bobcat the more I am impressed. I suspect this is due to the design of the airframe which I think we must credit to Bob Violett for. This plane has a very wide envelope and flys very well. With that said when the model was "converted" into the NitroModels Bobcat some of the background was obviously missing. At the center of this is the CG issue.

I was very fortunate in that many people had already flown the Bobcat when I did my review and had found the CG to be wrong. There were many other issues pointed out by early builder/flyers that made my project easy. I remember several posts scattered through different threads indicated that several CG calculators indicated 11" inches or slightly more to be the correct CG.

I can say with certainty that especially with heavier engines, the pilot needs to run out of elevator at the same time he/she runs out of altitude. If you do this the stock landing gear will not bend. If this is not somthing you can do or you don't have a very smooth landing strip I would simply replace the stock gear wire from the beginning.

Angus and others are sure making me want to try retracts, this plane is fast dirty, I can only imagine how much a cleaner aerodynamic footprint would help.
Old 01-13-2007, 08:56 PM
  #930  
ROB J.
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Default RE: Nitro models pusher Bobcat?

hello,

have a question. everyone talking about fixing landing gear blocks. I read in a post about putting epoxy in hole in front and behind of blocks. dou you have tomake your own holes, and how do you know where to make holes. not very experienced with patching covering

thanks
Old 01-13-2007, 10:40 PM
  #931  
dragonpilot
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Default RE: Nitro models pusher Bobcat?

ORIGINAL: mattgrant

Original Response:

The fuel tank is over the CG at 10". If you balance it at 10" there is a slight change in trim between full tank and nearly empty.


Are you saying to move the fuel tank forward? Right now as we all know, it is installed in the rear compartment, right be hind the engine. Just curious, can the manuel be that in correct?
1. Ok, everyone is getting way to worked up over moving the tank. It is fine where it is. I haven't found any negative tendencies with the fuel drain causing any problems with balance. I even had this Bobcat hovering -anyone try this yet, pretty cool to see. Dive up and then bleed off your speed in the vertical and use large throw control but leave yourself enough altitude for a recovery. You will need it!

2. If you are having problems with richness due to increase pipe pressure, install a hopper in there, and bonus you can fly longer!
3. Regarding reinforcing the landing gear blocks, you can drill holes and fill with exoxy or take a sharp xacto and cut nice square openings near the blocks, carefully remove the balso/covering squares, glue/glass in the blocks and then replace the squares and then wick in CA. Either that or get some same color stick on monokote from your LHS and patch.
4. DON'T ADD SO MUCH LEAD WEIGHT TO THE NOSE. Shove your battery pack way up there and hold in place with some thick foam pad and if that is not enough, Y-connect another pack and shove it in there and balance for aft with that, that way your dead weight is actually usable power for longer flight days.
5. You shouldn't be jumping off the runway, set the nose gear for slight positive angle and hammer it down the runway, it will take off and fly 2-3 off the deck smoothly.
6. I've got triple rates on the elevator, I fly with low and landing takes mid, and 3D stuff take high. If you don't have enough, you need a stronger servo!
The plane will nearly land itself, and touch and goes are fun. keep your rudder handy for the wind...


Hope this helps, thanks.
Old 01-13-2007, 11:29 PM
  #932  
gehr2box
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Default RE: Nitro models pusher Bobcat?

The tank is pretty close to being right on the CG at the stock location. Like I said, I happened to notice a very slight trim change near the end of the tank. Nothing major and at most it would need a single click or two of elev trim to compensate. Moving my CG aft .25 to .5" might eliminate it.


ORIGINAL: Larry Legg

Would it make scense to position the tank right at the CG? That way full or empty the CG remains consistant...or am I missing something.
Old 01-13-2007, 11:39 PM
  #933  
gehr2box
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Default RE: Nitro models pusher Bobcat?

To date may MLG have held up fine. I drilled a 1/4" hole in front of and behind the MLG mount blocks and poured in 5 min epoxy. I patched the holes with monokote. Worst case scenario you can put a piece of clear tape over the holes or matching color of self adhesive trim monokote.

To locate the position of the beginning end of the landing gear blocks poke a pin in the area in front of and behind the landing gear mount area. The pin will not be able to pop though on the hardwood of the gear blocks, but will easily poke through the balsa sheeting in front of and behind the blocks.


ORIGINAL: erin-rob

hello,

have a question. everyone talking about fixing landing gear blocks. I read in a post about putting epoxy in hole in front and behind of blocks. dou you have tomake your own holes, and how do you know where to make holes. not very experienced with patching covering

thanks
Old 01-14-2007, 12:30 AM
  #934  
Flyboy Dave
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Default RE: Nitro models pusher Bobcat?

....I agree.....the tank don't need messed with.

FBD.
Old 01-14-2007, 09:52 PM
  #935  
mattgrant
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Default RE: Nitro models pusher Bobcat?

DRAGONPILOT was are you using for your CG??? 10.5"???
Old 01-14-2007, 10:03 PM
  #936  
dragonpilot
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Default RE: Nitro models pusher Bobcat?

ORIGINAL: mattgrant

DRAGONPILOT was are you using for your CG??? 10.5"???
Hi Matt,

Yep is right around there, I shot for 10.3 initially but I haven't checked in a while. I failed to mention that my Bobcat came with 2 3/4" beefier wheels the first kit and the second unbuilt kit were smaller. (see earlier post by me).
In any case, I've got those in the rear and a Greatplanes 2 3/4" rubber tire on the nose gear. (a little more weight up front). I'm going to retracts as soon as I can free up some time with smaller rubber tires and wire struts. The gear hanging down is ok but damn it'll look good without it. And faster. If you're using a bigger volume engine, install a 2 oz hopper. It makes all the difference. Smooth runs, longer flight times. PS, you're looks fantastic, great job with that finish.
Old 01-15-2007, 03:26 PM
  #937  
i3dm
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Default RE: Nitro models pusher Bobcat?

Anyone else knows where i can order a bobcat immidately ? im not having luck getting Nitro Models on the phone.
Old 01-15-2007, 03:32 PM
  #938  
mattgrant
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Default RE: Nitro models pusher Bobcat?

http://www.raidentech.com/bobcatjets.html

Trying this. There are only two sites that I know of that carry the Bobcat. You can also try: AK-Models. They carry a similar plane. Good Luck.
Old 01-15-2007, 03:33 PM
  #939  
blueman260
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Default RE: Nitro models pusher Bobcat?

RaidenTech's site shows they have silver and Yellow ones still available
Old 01-15-2007, 03:34 PM
  #940  
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Default RE: Nitro models pusher Bobcat?

Im afraid RaidenTech isnt picking up their phones yet as well.. []
Old 01-15-2007, 05:55 PM
  #941  
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Default RE: Nitro models pusher Bobcat?

http://stores.ebay.com/Harris-and-An...-C-and-Hobbies

$125.00 + 39.95 shipping BUT they have them...

Well, they HAD them, lol...

PM
Old 01-16-2007, 03:03 AM
  #942  
bigplumbs
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Default RE: Nitro models pusher Bobcat?

Fuel Proofing

Earlier in this thread someone said that they did not think the paint on the fus was fuel proofed. I did a little test bu dripping some fuel on the fus engine mount over night and when I whiped it in the morning with white tissue there was no paint colour on the tissue at all. I therefore conclude that is is fuel proofed... I used 10% nitro fuel.... Has anyone else found this

Dennis
Old 01-16-2007, 01:10 PM
  #943  
AGR413
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Default RE: Nitro models pusher Bobcat?

My experience says the paint is fuel proof. I think I remember what you are talking about and in a later post there was a clarification that it must have been residual powder because the problem went away.
Old 01-17-2007, 03:47 AM
  #944  
Crashtruk
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Default RE: Nitro models pusher Bobcat?

I am curious. I see that 2 mini servos are required for the elevator. Do these 2 servos need to be run through any kind of matching box or is a Y lead sufficient ?
Old 01-17-2007, 07:50 AM
  #945  
MMallory
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Default RE: Nitro models pusher Bobcat?

Yes, a reversed servo, an electronic reverser or move the servo position. I used separate channels and mixed them.
Old 01-17-2007, 09:33 PM
  #946  
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Default RE: Nitro models pusher Bobcat?

For you guys that used the stock hardware, how did you manage to hook up the rudder horns? With the extreme sweepback of the hinge line, I can see how a horn and clevis would work from the stock servo position..... I cut slots and epoxied in Tamjets (keeping the topic jet related....) CF horns and used ball links to the servos....that works! ....on the ground , at least!
Old 01-17-2007, 11:22 PM
  #947  
Flyboy Dave
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Default RE: Nitro models pusher Bobcat?

The metal control rods that came in the kit were soft as butter....

....I chucked them.
Old 01-18-2007, 02:55 AM
  #948  
bigplumbs
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Default RE: Nitro models pusher Bobcat?


ORIGINAL: Flyboy Dave

The metal control rods that came in the kit were soft as butter....

....I chucked them.
Thats odd mine were very hard infact one broke when bending it

Dennis
Old 01-18-2007, 03:15 PM
  #949  
CrashPro
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Default RE: Nitro models pusher Bobcat?

Maiden flight of Serge's BobCat....video http://home.dc.rr.com/maurie/BobCatMaiden.wmv
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Old 01-18-2007, 04:21 PM
  #950  
bigplumbs
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Default RE: Nitro models pusher Bobcat?

Very nice first flight what engine and prop have you in her. Mine is about finished I have almost completed my build thread here :

http://www.rcgroups.com/forums/showthread.php?t=625414

Dennis

www.densplanes.co.uk

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