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Nitro models pusher Bobcat?

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Old 08-21-2006, 11:34 AM
  #151
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Default RE: Nitro models pusher Bobcat?

Quote:
bobber again:
. . . You are right about the fuselage effects.
Heh, heh, I found that out the hard way [>:] when I arbitrarily extended the nose on one of my ByroBlaster Enforcers - the jet was extremely pitch sensitive (doh) and the CG had to be move forward to compensate. I think the CG location for the NitroModels rendition is pretty darned close.

The 1st of the 2 yellow-flavored ones I ordered arrived last week. What a great thread! We're going to have fun with this airframe.

Mike
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Old 08-21-2006, 07:33 PM
  #152
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Default RE: Nitro models pusher Bobcat?

Just got mine in today also. I'm going to go ahead and use a .46 fx and try and see how light I can make the plane and see how it balances/performs on the 46 (doesn't seem like anyone else is going this route). If I like it I may do something like a Dubb Jett .46 in it later.
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Old 08-21-2006, 08:10 PM
  #153
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Default RE: Nitro models pusher Bobcat?

I was able to order one although I paid a bit more so for all those who got em cheap, well done. At first glance the kit and build seems very good, The paint work look well done as well. I'm impressed at this point. It was also packaged very well. The kit is far superior to any Lanier kits and others I've built. I hope they produce more and offer them at the same price, I would order another - (assuming it DOES fly!). I was planning on putting a dynamax fan and a .61 on it. We'll see with all the balancing concerns to date.
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Old 08-21-2006, 08:28 PM
  #154
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Default RE: Nitro models pusher Bobcat?

Is there not anyone who has a flight report yet?? Anxiously waiting for flight report everyone!
Seems like a good deal for this plane.
Myles
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Old 08-21-2006, 09:05 PM
  #155
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Default RE: Nitro models pusher Bobcat?

I have calculated the cg several times using different websites, and formulas. They all come out about the same. Around 11" back from the leading edge of the wing AT THE CENTER OF THE FUSE or around 9.3 or so from the leading edge where it meets the fuse. This would agree with the few post back. However, this does not take into account the lifting design of the tail. But I am not sure that it would make all that much diff. However, I am going to get some measurments on a bvm bobcat wing and then run the numbers on it and see if it comes out where the formulas say. If so, then I will prob. try and bal. somewhere between the cg rec. and what I caculated.

any ideas on this?
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Old 08-21-2006, 09:46 PM
  #156
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Default RE: Nitro models pusher Bobcat?

Miles

Ask Easykitty, apparently he has the answer for every question in the universe, I don't know, may be it is that he's to smart for me. [:-][sm=bananahead.gif]
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Old 08-21-2006, 09:54 PM
  #157
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Default RE: Nitro models pusher Bobcat?

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ORIGINAL: CARS II

Miles

Ask Easykitty, apparently he has the answer for every question in the universe, I don't know, may be it is that he's to smart for me. [:-][sm=bananahead.gif]
Yes, I probably am. I am also too gracious to point it out, but since you brought it up...
I have one on the way, and MAYBE one of the Avia-Richmodel ones, (the all balsa one), but I don't know exactly what I will do with it.
I'm kind of thinking what Mugenkidd is thinking...that unless you are trying to see exactly how heavy you can make it, for future turbine conversion, that lighter is better. I think a YS45 is the ticket, I have to look in the archive and see if I have one!

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Old 08-21-2006, 10:01 PM
  #158
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Default RE: Nitro models pusher Bobcat?

At least we agree on one thing, the YS 45 is the ticket for the Bobcat.

Good luck with it.
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Old 08-21-2006, 10:10 PM
  #159
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Default RE: Nitro models pusher Bobcat?

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ORIGINAL: CARS II

At least we agree on one thing, the YS 45 is the ticket for the Bobcat.

Good luck with it.
IF I had known YOU said YS45, I would have definitely recommended something different! Damn, too late.
The 45 is often the ticket for this kind of thing, the Combat Models F-15, etc, it does not mind being a pusher, and it really honks.
But I don't really WANT a glow pusher prop plane...just not that interesting to me, been there already, so I may do large EDF instead.
I do understand the point of B-58, though, of stuffing in a large engine just to add weight to see how it goes before doing a turbine. That makes sense to me.
Noah...IS the stab a lifting section? You mentioned the lift of the stab...
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Old 08-21-2006, 10:42 PM
  #160
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Default RE: Nitro models pusher Bobcat?

easy,

The stab is an flat bottom airfoil, ( wing is flat bottm too) you should be able to get a hitec thin wing servo in the stab if desired. But will have to drill through the fin panel's ribs (2 of them...or more? ) to feed the servo lead.

Work on mine in spare time a Dubb Jett BSE 50 should be here tomorrow.
I plan on wing bolts similar to my roo for wing attachment (not glue!)
Fixed gear for now spring airs next winter
with any luck i will fly it this weekend. with full report (AKA Crash damage)
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Old 08-21-2006, 11:34 PM
  #161
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Default RE: Nitro models pusher Bobcat?

well guy's this is the finished product with the YS-45 and tuned pipe with a 10x7 prop, my CG is 175mm (6.9in), total weight is 8 1/4lb, I'm gonna go for the maiden Wednesday.
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Old 08-21-2006, 11:48 PM
  #162
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Default RE: Nitro models pusher Bobcat?

Finally, we are about to see the light or should I say the flight? he he . Thank you topper5.
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Old 08-22-2006, 06:06 AM
  #163
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Default RE: Nitro models pusher Bobcat?

Can you show more pic's of your canopy? I need to know how you are fixing the canopy.
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Old 08-22-2006, 09:15 AM
  #164
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Default RE: Nitro models pusher Bobcat?

ET, another reason to go with the FX .91 is that I have one. I also have an unrun K&B .61 with pump that is sitting here looking pretty. I thought about that too and I could mount the tank far forward. But with the other opinions on the cg I will probably stick with the OS. Really looking forward to some flight info. I will finish the P-47 I have been slowly working on today, and that will free up time and space for the little Bobcat. Bob
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Old 08-22-2006, 12:37 PM
  #165
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Default RE: Nitro models pusher Bobcat?

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ORIGINAL: B58

ET, another reason to go with the FX .91 is that I have one. I also have an unrun K&B .61 with pump that is sitting here looking pretty. I thought about that too and I could mount the tank far forward. But with the other opinions on the cg I will probably stick with the OS. Really looking forward to some flight info. I will finish the P-47 I have been slowly working on today, and that will free up time and space for the little Bobcat. Bob
Makes sense to me...don't think I want to buy another glow engine for this bird, though I WOULD get the high powered EDF gear for it, as I have another project in mind that could use that stuff.
I know I have a pumped K&B61 around...I also remember that after two gallons or so, it's STILL not really broken in, and won't idle right! Another reason not to use that! The FX 91 should go great guns. My guess is that you will need to cut the engine off entirely for landing, that the idle thrust will be too much with a 91, but, again, that remains to be seen. But I would set the engine up to give you cutoff if needed...
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Old 08-22-2006, 06:05 PM
  #166
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Default RE: Nitro models pusher Bobcat?

well guys, after running numbers over and over I don't see how they came up with there cg calculation. Now I know I am not the designer, but even if I compute it at 15%of the mac, it's still far off. I am comming up with numbers in the 9" range from the leading edge next to the fuse. Maybe someone else out there can enlighten me/others as to why the cg is so far forward. Are bvm bobcats like this?

Just want to be sure as I would hate for someone/me to take off with the wrong balance and hose an airplane.

thanks
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Old 08-22-2006, 06:50 PM
  #167
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Default RE: Nitro models pusher Bobcat?

noah, I did a quick graphic calculation of the Composite BobCat MAC based on a small 3 view pulled off the BVM website. I calculated that the recommended CG is at about 23%. I'm not an aerodynamicist, so take it for what it is worth.
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Old 08-22-2006, 08:27 PM
  #168
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Default RE: Nitro models pusher Bobcat?

bobber, does it look as if it is as far forward as the bobcat 46? If you look at the top, it is pretty far forward. I don't want to doubt the designer so to speak, but I think it's a misprint. I don't see anything on the bobcat that would justify a forward cg as the instructions called out. If it was say .5" that we were talking about then it would not be that big of a deal, but it's around 2.5 ". In an earlier post, somebody posted they added 1.5lbs to the nose to obtain bal. I just don't see that happening unless they used a huge engine.

any one else has a thought on the cg?
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Old 08-22-2006, 08:28 PM
  #169
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Default RE: Nitro models pusher Bobcat?

Topper, did you have to add weight to obtain that cg balance?
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Old 08-22-2006, 09:09 PM
  #170
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Default RE: Nitro models pusher Bobcat?


Quote:
ORIGINAL: H.Dale

PST I am just using two 16oz Dubro's tanks. Just plumb them together. You won't have to cut the bulkheads and it's a lot cheaper.

Has anyone mounted the turbine yet? I would like to see how you did it. I was just going to use a couple of blocks but there may be a better way.

What about a latch for the canopy. Has anyone done that yet?

Hal
Yep, a lot cheaper but I did get 2 more oz. Works out about $20.00 per oz!! OH Well!!

Here's some pix of the canopy. It's not completed as I need to complete the framing of the entire canopy. But should be easy to do. The screws are small poly screws from BVM with the counter sink heads. It's held on the fuse. by a hook at the front and an 8-32 nylon screw at the back. I'm plagiarizing the real thing.
Galen
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Old 08-22-2006, 09:36 PM
  #171
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Default RE: Nitro models pusher Bobcat?


Quote:
ORIGINAL: noahb

bobber, does it look as if it is as far forward as the bobcat 46? If you look at the top, it is pretty far forward. I don't want to doubt the designer so to speak, but I think it's a misprint. I don't see anything on the bobcat that would justify a forward cg as the instructions called out. If it was say .5" that we were talking about then it would not be that big of a deal, but it's around 2.5 ". In an earlier post, somebody posted they added 1.5lbs to the nose to obtain bal. I just don't see that happening unless they used a huge engine.

any one else has a thought on the cg?

I had to add the 1.5 lb to the nose, I'm running an O.S. 61 W/ stock muffler. That was setting the CG @ 6.9". I like the 11" cg idea better, Then it would balance just fine
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Old 08-22-2006, 10:16 PM
  #172
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Default RE: Nitro models pusher Bobcat?

well that would be 11" from the center of the fuse if the wing cont. on to the middle. Its more like around 9 or so if you go from the leading edge by the fuse.

However, I would be very careful flying it at either location until we find out further info. Not sure what to do. It's not like we can contact the mfg.
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Old 08-22-2006, 10:45 PM
  #173
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Default RE: Nitro models pusher Bobcat?

NOAHB yes i added 1/2LB weight plus a 1/2lb c-cell battery to achieve the proper CG at (6.9in-175MM)... AND IT'S ALL WRONG THE CG CAN'T BE (6.9in)... I could'nt wait until tomorrow morning, so i wen't this evening, tuned my motor in and let her go! after 300.ft (approximately) clear down the road!!! it would not get off the ground, at the last second i could see the nose rise, but at that moment i realized it had gone too far with out rotating so i dropped the throttle and went home.
ill pull out the 1/2lb weight and leave the 1/2lb c-cell battery, and on that note it will balance closer to the 9in CG that had been suggested earlier in this thread.

maybe ill try again in the morning.
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Old 08-22-2006, 11:26 PM
  #174
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Default RE: Nitro models pusher Bobcat?

minus the the 1/2lb weight my CG is exactly 9.in (total weight 7-3/4lb)
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Old 08-23-2006, 09:24 AM
  #175
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Default RE: Nitro models pusher Bobcat?

Please keep it coming.
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