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RE: Nitro models pusher Bobcat?
ORIGINAL: Eric Banner Hi guys, The canopy on my 50-size bobcat came off in flight yesterday. The canopy was completely destroyed but did not cause an appreciably trim change and I landed safely without further damage. Can anyone assist with any information to help in locating a replacement? Thanks, Eric Video of penultimate flight: http://www.youtube.com/watch?v=OucKVUMAzKQ |
RE: Nitro models pusher Bobcat?
Hi Jim,
Ah, that's what I suspected the solution would be. Just being lazy looking for a quick fix... Best regards, Eric ORIGINAL: Jascat100 ORIGINAL: Eric Banner Hi guys, The canopy on my 50-size bobcat came off in flight yesterday. The canopy was completely destroyed but did not cause an appreciably trim change and I landed safely without further damage. Can anyone assist with any information to help in locating a replacement? Thanks, Eric Video of penultimate flight: http://www.youtube.com/watch?v=OucKVUMAzKQ |
RE: Nitro models pusher Bobcat?
On my second bobcat. first one never made it over the trees. Second one flew the circut once but nose dropped when I let the stick go to neutral. CG was at 10.3. I'm wondering if I have the elevator control surface set correctly. Does anyone have a picture or a description of the neutral position on the elevator? Do I align the bottom with a ruler on the bottom of the stabilizer or do I put the trailing edge tip of the elevator in the middle ?
Any help would be greatly appreceated. Ken ' |
RE: Nitro models pusher Bobcat?
Ken. The elevator neutral position on mine just follows the natural curve of the top surface of the elevator. The one I fly has a turbine which is angled down at the rear, so this may result in a different effect from one with a propellor.
A solution is to get someone you can trust to stand beside you when you take off. Climb to a safe height & check the neutral pitch. If it tends to dive, quickly pull back to straight & level. Get your helper to add a few clicks of up elevator & try again until it flies level. When you land, move your servo arm to the new neutral position & fine tune with the clevis adjustment. If you find the pitch varies with the amount of throttle used, then you have an engine thrust line problem. |
RE: Nitro models pusher Bobcat?
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Ok, here are 3 side views. I would have guess the first one, bottom of control surface even with bottom of stabilizer was right, but after flying it does not appear correct. The second I think best matches the curve of the top, the last one matches another poster who said that they had the trailing edge match the top of the stab.
Any ideas on whats best or even "right" Ken |
RE: Nitro models pusher Bobcat?
The "right" mid point setting will be somewhere between the picture on the right and the picture on the middle.
This is an important point... I did exactly as you did and attempted to align the elevator with the bottom of the stab. The first flight was a bit horrific. The plane DID NOT want to take off even after a long runup... and once it did, it SHOT up... I was struggling with it in the air. Fortunately a bunch of Kingcat guys were next to me and one particularly experienced person helped me trim it out ( I didn't have enough trim available !!! ) as much as possible then bring it down. Once I landed the plane he looked over it and commented that I had the elevator pushing the nose down. That even on the Kingcats there had to be some deflection towards the upper part of the wing surface. I moved the servo arm ONE "tick" to bring the elevator up, and this fixed the plane's flight characteristics. I also added "spoileron" flap settings of about 1/4" up as suggested here, which helped landings quite a bit. Now I'm very happy with this plane... |
RE: Nitro models pusher Bobcat?
hello all,
i've read this entire saga from begining to this point and have assembled one of these birds with a tower 75 on the back. i am currently breaking the engine in with an eleven/seven tractor prop, and have about 40 ounces through it. i don't seem to be getting the rpm that every one else seems to be getting. i'm using 20 % wildcat 2/4 cycle with 20% synthetic oil. i'm getting very good smoke from the muffler, but can't seem to get the high needle more than 2 1/4 turns out with out it starting slow down. i richen it back up to about 2 1/2 turns and it speeds up again to a nice sounding 10,400-10,700 rpm all the while the exhaust smoke is in great abundance. any ideas ? i am using the remote needle if this makes a difference. |
RE: Nitro models pusher Bobcat?
Ken,
I have the smaller one and lined it up with the botton of the stab and it required just a click or two of up trim. The stab is a flat bottom airfoil on mine which looks just like yours, so should be flat. Brian ORIGINAL: Ken LaPointe Ok, here are 3 side views. I would have guess the first one, bottom of control surface even with bottom of stabilizer was right, but after flying it does not appear correct. The second I think best matches the curve of the top, the last one matches another poster who said that they had the trailing edge match the top of the stab. Any ideas on whats best or even "right" Ken |
RE: Nitro models pusher Bobcat?
The Tower .75 doesn't seem to come into it's own until you have well over a gallon run through it. You'll know you are at that point when two things happen, 1- the engine will seem able to idle reliably at a very slow speed, 2 - you are able to get the RPM's to about 11,000+ at WOT with the recommended break in prop size. Once that happens you'll find that the engine will unload even more in the air. It will be QUITE LOUD as it screams by you. You don't need to run 20% through the T.H. 20% will not hurt it, but it's a bit of a waste. Once the engine has broken in, it idles very well. Higher Nitro gives you better idle and a wider tuning range, something that's lost on a broken in T.H. .75 once it's dialed in. Don't worry about the smoke. As long as you are not blowing out fuel, smoke is good. It sounds like you are approaching optimum, but are not quite there yet. Go 1-2 clicks leaner on the high end and check you RPMs. Try to do this on less than 1/3 of a tank so you are checking the engine at it's leaner points... I'd recommend starting from the extreme end of the airfield, that way if you notice the engine hesitating too much at runup, you'll have plenty of space to abort the takeoff. If you are getting good transition during the runup as the plane takes off, start flying the plane. After a few flights you'll notice that you could lean the engine out a bit more. Do so. You'll not that the needle is fairly sensitive. You can gain ( or loose ) a LOT of RPM's with a click or two. BTW: The first time I flew mine it initially felt underpowered. I kept adjusting slightly after each flight... by the 4th or 5th flight it was screaming along, especially as the engine unloaded during a very shallow dive. Now the "jet guys" come up and tell me that the Bobcat flies "very well. |
RE: Nitro models pusher Bobcat?
ORIGINAL: TUMBLER Ken, I have the smaller one and lined it up with the botton of the stab and it required just a click or two of up trim. The stab is a flat bottom airfoil on mine which looks just like yours, so should be flat. The smaller Bobcat needs less elevator up in comparison to the larger .52 or Falcon 1.20. Do NOT make the elevator level with the lower back of the stab on the larger planes. Also remember that we don't know exactly what 1 or 2 clicks equals on Tumbler's radio. My JR defaults to 4% movement per click which is quite a bit ( it is user adjustable ), so Tumbler's two clicks could be enough to bring it more in line with the rightmost picture. At the very LEAST go with your middle picture, then dial it further up as needed. From experience ( and I have the smaller and the larger planes ) DO NOT attempt to fly with the leftmost picture. |
RE: Nitro models pusher Bobcat?
Here is how I made the Bobcat .25's Canopy easy to remove...
http://image2-6.rcuniverse.com/e1/ga.../lg-113287.jpg http://image2-6.rcuniverse.com/e1/ga.../lg-113288.jpg |
RE: Nitro models pusher Bobcat?
Here is how I made the motor box removable.
http://image2-6.rcuniverse.com/e1/ga.../lg-113284.jpg http://image2-6.rcuniverse.com/e1/ga.../lg-113285.jpg http://image2-6.rcuniverse.com/e1/ga.../lg-113286.jpg Later the motor was changed from the Rimfire to the BP2915D ( Tower Pro Motor ), MA 10x7 3 blade prop. http://image2-6.rcuniverse.com/e1/ga.../lg-113289.jpg |
RE: Nitro models pusher Bobcat?
Shot of flight ready configuration of the Bobcat .52
http://image2-6.rcuniverse.com/e1/ga.../lg-113283.jpg |
RE: Nitro models pusher Bobcat?
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Nice canopy mod, i like it! I had to add 2 washers to the front of the motor to get it to fly level. The mount had 1 degree of negative incidence, which gave it up thrust. mine is now a little more than 1 degree postive. I opened up the motor wire hole for cooling, but good use a little more, as the speed controller got hot. I got the retracts almost finished up as well for the mains. Time for the nosegear.
Brian |
RE: Nitro models pusher Bobcat?
Awesome!
You put RETRACTS in the .25!! ... very nice. I didn't have any problems with the motor incidence, but that is probably because I went with their "box" that raises the motor a bit. Yours seems to sit a bit lower than mine, and closer to the fuselage. Of course I may not be flying as FAST as yours too, so maybe I need to wait until I have it flying at faster speeds. |
RE: Nitro models pusher Bobcat?
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Yes sir! I think this thing is just awesome lookn, so its worth the extra effort to clean her up a bit!
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RE: Nitro models pusher Bobcat?
RE: Tower .75
IMHO a gallon is about right for a proper break in, I think mine took a little less than a gallon, I used 15% omega, I like a little castor when breaking in an engine. You need to get the tower pretty warm to encourage the break in process, I would lean mine to point where it was still slightly rich and monitor the head temp with my fingers. I let the temp get up to a point where I can't hold my finger on the head for more than a second or just a little less. It it gets where you can't even touch it at all then it's too hot (remember to keep it just a touch rich using the pinch test) After about a minute I richen it up and let the head cool and then move it toward peak RPM again keeping it just a touch rich. If you use this process it does not take long and each time you will find an increase in RPM and a little more range in the needle. Additionally as the process moves forward it will take longer to heat up. The result is (once I got the low end dialed in) and engine that starts on the first flip and screams in the air. |
RE: Nitro models pusher Bobcat?
ORIGINAL: opjose The Tower .75 doesn't seem to come into it's own until you have well over a gallon run through it. You'll know you are at that point when two things happen, 1- the engine will seem able to idle reliably at a very slow speed, 2 - you are able to get the RPM's to about 11,000+ at WOT with the recommended break in prop size. Once that happens you'll find that the engine will unload even more in the air. It will be QUITE LOUD as it screams by you. You don't need to run 20% through the T.H. 20% will not hurt it, but it's a bit of a waste. Once the engine has broken in, it idles very well. Higher Nitro gives you better idle and a wider tuning range, something that's lost on a broken in T.H. .75 once it's dialed in. Don't worry about the smoke. As long as you are not blowing out fuel, smoke is good. It sounds like you are approaching optimum, but are not quite there yet. Go 1-2 clicks leaner on the high end and check you RPMs. Try to do this on less than 1/3 of a tank so you are checking the engine at it's leaner points... I'd recommend starting from the extreme end of the airfield, that way if you notice the engine hesitating too much at runup, you'll have plenty of space to abort the takeoff. If you are getting good transition during the runup as the plane takes off, start flying the plane. After a few flights you'll notice that you could lean the engine out a bit more. Do so. You'll not that the needle is fairly sensitive. You can gain ( or loose ) a LOT of RPM's with a click or two. BTW: The first time I flew mine it initially felt underpowered. I kept adjusting slightly after each flight... by the 4th or 5th flight it was screaming along, especially as the engine unloaded during a very shallow dive. Now the "jet guys" come up and tell me that the Bobcat flies "very well. thank you for your advice. i will follow it to the letter. if all goes well and weather permitting, i will maiden it this weekend. wish me luck, and thank you for the response. fair winds straight down the runway! |
RE: Nitro models pusher Bobcat?
thanks for sharing your experience. i'm getting a good low idle now with almost instant throttle response. there is no hesitation from idle to wide open. it's like throwing a switch. idle to top rpm instantly. if i can get about five to six hundred more rpm on the grond i will be happy with it. this engine seems to be very well built except for the remote needle mount. i think i will move it to the throttle body when it is finally broken in.
thanks for your help. this is a great hobby with great people. |
RE: Nitro models pusher Bobcat?
Hi guys My Name Is Ghanesh From Chennai India.I have bought a Gas Bobcat .50 retracts ready model.I am fixing a O.S. .46ax.I would like to know the difference in performance between this and a turbine one.Also pls help me with the retracts that i need to fix in this.I dont know anything abt retracts so pls avoid technical terms.Also i need info abt a tucano t1 which i have inline
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RE: Nitro models pusher Bobcat?
Ghanesh Here again please also let me know what i should put instead of a spinner in a bobcat
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RE: Nitro models pusher Bobcat?
I just wanted to chime in on the engine selection discussion, because I'm amazed at how many people will put the best radios, servos, retracts, etc, and then go with the "discount" motors. I truly believe you get what you pay for 99.9% of the time in this hobby...for example:
It sounds to me that after you put about 2 gallons through the Tower, it will be almost up to the performance level of the OS55-AX...this is why I always recommend to people not to buy the cheap motors...my Bobcat flew on the second tank with the OS...the "break in" tank had a beautiful idle after 3 minutes, and I was able to lean it out to normal operation by the end of the first tank (of course a bit rich). So add the price of an extra couple of gallons of nitro to the price of the Tower 75, and you're a LOT closer to the price of the OS....now factor in the amount of time you've spent breaking it in, and what your time is worth.....even CLOSER to the price, if not more now....and now it's broken in, and there're reliability issues (I've read in several different threads) with this motor, too. At the end of the day, I think that you're not really "saving" anything by going with the Tower 75....you've added an extra 10 oz. or so to the plane, higher fuel consumption, and we're still stuck without many prop choices for the larger displacement motor. My current configuration (that I'm happy with) is: OS 55 AX with the Jett Pipe (I haven't yet tried the Weston, but I do have it to try tomorrow), 30% nitro, APC 11x7 prop....and I'm guessing that I am doing about 120mph or so under normal flying conditions (I was clocked last weekend at about 101mph into a strong headwind as measured by radar.) It's turning 14,000+ on the ground now. Believe me, it's fast! Until you put a radar, people tend to estimate MUCH faster... I fly for about 7 minutes, and can probably stretch it longer, but why? :) I REALLY REALLY like this motor - it's sweet. If you really have to pop in a larger displacement motor, I'd definitely spend the extra cash on the OS 75 AX...but again, there's prop issues... OK, my $0.02 for the new Bobcat fliers out there... I'm definitely intrigued with the little electric one - you can make the motor turn the opposite direction, and that really changes the prop game...interesting. |
RE: Nitro models pusher Bobcat?
ORIGINAL: marktur I just wanted to chime in on the engine selection discussion, because I'm amazed at how many people will put the best radios, servos, retracts, etc, and then go with the "discount" motors. I truly believe you get what you pay for 99.9% of the time in this hobby...for example: It sounds to me that after you put about 2 gallons through the Tower, it will be almost up to the performance level of the OS55-AX...this is why I always recommend to people not to buy the cheap motors...my Bobcat flew on the second tank with the OS...the "break in" tank had a beautiful idle after 3 minutes, and I was able to lean it out to normal operation by the end of the first tank (of course a bit rich). So add the price of an extra couple of gallons of nitro to the price of the Tower 75, and you're a LOT closer to the price of the OS....now factor in the amount of time you've spent breaking it in, and what your time is worth.....even CLOSER to the price, if not more now....and now it's broken in, and there're reliability issues (I've read in several different threads) with this motor, too. At the end of the day, I think that you're not really "saving" anything by going with the Tower 75....you've added an extra 10 oz. or so to the plane, higher fuel consumption, and we're still stuck without many prop choices for the larger displacement motor. My current configuration (that I'm happy with) is: OS 55 AX with the Jett Pipe (I haven't yet tried the Weston, but I do have it to try tomorrow), 30% nitro, APC 11x7 prop....and I'm guessing that I am doing about 120mph or so under normal flying conditions (I was clocked last weekend at about 101mph into a strong headwind as measured by radar.) It's turning 14,000+ on the ground now. Believe me, it's fast! Until you put a radar, people tend to estimate MUCH faster... I fly for about 7 minutes, and can probably stretch it longer, but why? :) I REALLY REALLY like this motor - it's sweet. If you really have to pop in a larger displacement motor, I'd definitely spend the extra cash on the OS 75 AX...but again, there's prop issues... OK, my $0.02 for the new Bobcat fliers out there... I'm definitely intrigued with the little electric one - you can make the motor turn the opposite direction, and that really changes the prop game...interesting. YOu are are right ebout the engines , my gms 76 turns the 11x7 at 14,000[:-] |
RE: Nitro models pusher Bobcat?
Mark whats you altitude im at 3300
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RE: Nitro models pusher Bobcat?
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXNMD1]OS.55 AX[/link] = $149.97
[link=http://www.jettengineering.com/]Jettt stream 90[/link]= $85 + shipping Total = $234 [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXUR78&P=ML]Tower .75 ABC w/ Stock muffler[/link] = $89.99 (right now, free shipping) $234 -$90 $144 I can buy quite a few gallons of fuel for $144 and I'm going to have to check again but I'm pretty sure I was getting at least 14,000RPM with the 11x7 on 15% nitro. I have run less than a gallon of fuel through my TH 75 and it idles and transitions perfectly. Also, the Tower 75 w/muffler weighs 23oz. The AX55 w/muffler weighs 18.52oz. That is less than 4 1/2oz. I haven't tried them side by side yet, but I'd be surprised if the AX 55 is any stronger that the "discount" Tower 75. As a matter of fact, I would be willing to bet that if you put a Jett Stream muffler on the Tower 75 it will eat the AX55 for breakfast. There is nothing wrong with saving money when performance doesn't suffer. My $.02 for the new Bobcat fliers. ;) Blessings, Terry |
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