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RE: Bob Cat Copy Falcon 120 Jet
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heres picture of the lipos attached to the carbon support rails, then taped to the air tank.
Also pic of spring and clip retainer for the air tank. Simple to remove the lipos from the plane for charging, no tools required. I put wing mounting tape on the cut out for the air tank, so it holds the tank firm without sliding. |
RE: Bob Cat Copy Falcon 120 Jet
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pic of spring back undercarriage, you can see, when retracted, the top part of leg is protruding from the wing lower surface. This concerned me, if made again I would have offset the mounting pin to sink the gear in a bit more. Took plane high before first retraction, everything was fine. In fact when the gear is stowed, the reduction in drag is noticable,
I had to remove and scrap the original leg plastic trims that fit in the wing recesses. I left the wheel tubs alone. I had to trim the wing skin lightly to allow the trailing link gear to fit. I filled the voids in the wing, with self adhesive ally tape. Formed the tape around a tube, positioned them, then retracted the gear and let the gear form the correct shape, nice and easy. |
RE: Bob Cat Copy Falcon 120 Jet
Well done TimJet,
She looks great and well done for all the engineering that you have done. Does your home made Turbine have a delay if so how much? Well done again. Regards BiGToP |
RE: Bob Cat Copy Falcon 120 Jet
Nice job on the LG.Where's the "ally" tape you refer to?
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RE: Bob Cat Copy Falcon 120 Jet
TimJet, looking good. But make sure those Lipos receive some air to cool down. I saw an electric version of the small one with a shubeller fan. The guy had two lipos packs one behind the other and when he land, we smell something like solvent. Guess what, that batt. in the back did not recive enogh air to cool down while in the air. Almost explode inside the model. We took it out and put aside far from us just in case. [sm=71_71.gif]
Rgs Alex |
RE: Bob Cat Copy Falcon 120 Jet
The ally tape is not shown in the picture, I fitted it just prior to flying as I did not want airflow entering the wing area and lifting the skin off. The tape I used, is used on comercial aircraft, it is called speed tape, and is used to cover non critical temporary repaired areas , until down time is available for sealant etc to harden and stop moisture ingress and freezing damage in flight. Not sure where it is commercially available. What you could use, is an old chinees take away tin foil pot and attach it with double sided tape. How about an old cigar tube.
I had a hell of a job trying to find ally self adhesive tape, to fit on the tail plane lower surface, that was light enough. Dave from Colchester Models donated some of his to me (thanx Dave), but I found some today in builders merchant, Travis Perkins. It was with the Gaffer tape, £6 pounds a roll. I tried a small sample today on a piece of balsa with a flame directly on it, seemed to work ok. If you get stuck maybe give it a try, but I can not say if it is the same stuff, use at your discresion Ref the spool up time on the engine, by their nature, it will always take a time for the engine to accelerate, due to inertia of the rotating assemblies. Also, to keep the turbine temps within limits, then the fuel has to be ramped up at a rate not to exceed the design temps of the back end. The other phenominan, is compressor stall and then surge. If you imagine the engine at constant speed, then the compressor is creating more pressure than is being generated in the combustion chamber, so the gasses flow out the back and hit the turbine, generating work. If you suddenly pour fuel in, there is danger that the turbine can not spin the compressor up fast enough and the pressure in the combustion chamber can cause too much back pressure on the compressor, and cause the air to be disrupted. This is dangerous, at worst, the airflow can reverse. This is why spool up is controlled at a controlled safe rate. Also during spool down, you have to be carefull not cause a flame out. This is a very very simplified brief explaination. I found the lag does not cause problems in flight. I have posted a quick video below. If you listen, engine is at around 1/4 to 1/2 throttle, most of the flight. After flying past, you can hear the engine accelerate to around 3/4 throttle, up into the turns. The lag is noticable during a go around, if the engine is at idle. This is the worst case, so I will be trying 45 degrees flap on my next flights, so the engine will need to be producing some thrust to overcome the drag, hence a higher initial speed and faster spool up. During loops, at the top, I have tried pulling the throttle back quite rapidly and all has been fine, but in general I operate the throttle very slowly. The plane flys so well, that if you make a cock up, it will slow down to nearly nothing, while engine accelerates, then away you go. In this video shot or the previous one, you can see this, when I cocked up the landing and went around. You have to think a couple of seconds ahead, but this is my first turbine and would say that the plane is easier to fly than I first imagined, it is a credit to the designers, thanx designers. Check out the gear on this bouncy landing http://www.youtube.com/v/ERI2tS2u5Ro www.youtube.com/v/y_s54YJCod8 Fuel tanks - I am still using the 2 ltr soft drink bottle, which gives good access inside for the wing attachment bolts. The CG position means that our fuel tanks are mainly fwd of the CG, which obviously will not help on the take off roll, where the model is now nose heavy, so more speed is required before the elevator becomes effective. Not sure how much more nose heavy the model is with a full tank, I will have to test it, but maybe a purpose made tank, possible from fibergalss made from a foam plug would be good, which could take advantage of the curved roof of fusealarge allowing for a shorter tank but with the same capacity. I tried pouring boiling water over a plastic bottle to reshape it, it dose mould, but hard to control. Maybe a plywood frame the correct size could be made and the bottle heated with warm water and pushed into shape, whilst slowly releasing the air from inside through the filler niple. Might try some experiments. |
RE: Bob Cat Copy Falcon 120 Jet
Guys,
On my friend's falcon with JJ 1400 he wants to use 0.5L of smoke (16 oz). we found the original tank to fit inside the fuse above the Dubro 50 oz tank, but didnt count for the wing front aluminum spar. when we installed the spar, its hard to get them both to fit. any ideas on how to make the 50 oz Dubro fit together with another 0.5L tank for smoke ? pics would be great ! |
RE: Bob Cat Copy Falcon 120 Jet
Guys,
Can the Falcon accept 2.25" main wheels if using a turbine ? |
RE: Bob Cat Copy Falcon 120 Jet
ORIGINAL: tim777jet Had three excellent flights yesterday, I made a few changes since my last flight. I fitted spring back struts on the mains, like the Jet-1A type. I saw someone on this site had fitted them but no info on what type. I also contacted Digitec to work out which ones would fit. No answer. I think they are crazy, because these models are going to be really popular. The field I am flying from is grass, so decided that to proplong the wing and fuse structure, I definatly needed better legs. I bought 2 legs from Motors and Rotors, they are made by AT, I had to mod them to fit. A lot of milling and cutting down. They work great, they take a lot of punishment away from the undercarriage mounts, very impressed. Will post some pics later and try to upload some vid footage on youtube later. My lipo batteries for ECU and radio are as far forward as possible, as my home made engine is heavier than your manufactured ones, to get the correct the CG. I had made up a rail system to hold them, but for ease of removal, I have now taped my carbon rail holders directly to the air tank, so I just pull the tank out, complete with batteries for charging and balancing. I also found a really easy way to hold the tank in, a simple spring and clip that clips around the air tank supply pipe. real easy. Flights were @ 7.5 mins, so about 9 min run on the engine. I use just a 1320 ma lipo for the jet ( for weight reasons), so with starter motor giving the lipo a battering, I tried a different soloution. I soldered on another lead to the power lead just as it enters the ECU. When i start, I plug an old Nicad pack into this fly lead. I start the engine and as it acelerates through its idle rpm up to its calibrating speed, I quickly switch on the onboard lipo pack and imediatly unplug the nicad pack. After landing, after shut down , I plug the nicad in and imediatly switch off the lipo, so cooling runs are from the nicad. This way I fly many times without recharging. My 1320 Lipo reciever pack was fine after 3 flights, the excellent Align regulator voltage LEDS had dropped just 1 indication, so hadly any consumption. With the flaps, had a slight amount of up programed in with 20mm flap. This is not reqiuered and causes the model to ballon slightly. With no elevator input it is just right. Have to try the full 45 degrees yet. For info, my Undercarriage and heavier wheels, have added a bit more weight. With a full UAT, dry weight is around 14.5 pounds. Engine puts out about 13 lbs thrust. Fuel is around 3.5 pounds. On the grass there is lots of drag. The model will accelerate to a set speed then will go no faster. Feed in a little up, and the model accelerates rapidly and smoothly lifts off on its own accord. On landing the stoping distance is really short due to the grass. No brakes required. Model is docile and rock steady, can be slowed up to unbelivablely slow speeds and yet you can throw it arouond. I am still getting aquanted with my model and love it. Cheers Tim sorry did not see your email..... anyway here is the problem it is a 6.5 kilo model with its crappy gear therefore it needs a robuust gear setup. the gear we have for the l-39 is to small (max 5 kilos) and the gear for the intro is a bit big and will add another 400 grams on total.. so please tell me what you guys want , and i will make it.. |
RE: Bob Cat Copy Falcon 120 Jet
Hi digitec, the main legs I have altered to fit the model, have the spring built inside the main strut, to reduce the amount of wing structure removal required to fit the legs. The legs need to be approx 160 to 165mm between the axel centers and the the top of leg where it meets the retract unit and the nose needs be aprox 145 mm. I say aprox, because it depends on what size wheels you use and which type retract units. I am using 70 mm wheels on mains and 72 mm (2 3/4 inch) on nose, to prevent the nose digging in to the long grass on take off. Remember there is 5 degs of down thrust from the engine.
I am using soft rubber tyres, which weigh more than the foam ones in the kit. My original legs, fitted with JP oleos and the foam wheels were only slightly heavier than the supplied spring steel leg and foam wheel. These weighed 70 gms each. My new legs with the foam wheels weighed 100 gms. With the heavy wheels they are 120 gms. I can still machine quite a bit of the legs away to reduce weight, but left them for now, so I can experimant with different spring positions. I think the mains need to be slightly toughened up, so will fit a bush to the spring pick up bolt to preload it slightly more. I would like to fit a spring back nose leg to the model, instead of the Euro kit trailing link leg I have now. The trailing link leg with its compression spring and no form of damping, leads to a bouncy nose. The Jet1A Boomerang nose leg is, I have been told, 145 mm, but the wheel it can accept is only about 2 1/4 inch, which is too small for grass ops. This is a real shame, as it would be perfect for the job. I have never seen a set of Jet1A legs close up, so dont know how much they weigh, but I am sure they could be lightened. At the moment I am carrying an extra 100 gms approx, with my legs, to put it into perspective, I can reduce my fuel load by 100 gms and fly for say 30 secs less, but have a better chance of leaving the retract mounts in the wing when I land. Cheers Tim |
RE: Bob Cat Copy Falcon 120 Jet
Hi All,
I had planned to use the 50oz DuBro fuel tank in my Falcon as a lot of others had. I re-shaped the formers to accomidate this tank but found that I had to move the tank slightly forward to allow access to the wing bolts. Also, because of the forward spar, I was not able to get the tank to sit level. I have recently discovered that a 64oz Gulf Lite charcoal lighter fluid bottle will fit completely reward to the rear wing tube and allow access to the bolt holes. It also sits level in the fuse. I will be installing a Super Bee and may or may not need a little extra fuel but I figure i can always leave some off. My question is: This fuel tank will not be transparent as it is white. Do you think it would be a disadvantage to not be able to visually check the fuel level after a flight to get some idea of fuel consumption without defueling and measuring fuel remaining? Thanks, Grodus |
RE: Bob Cat Copy Falcon 120 Jet
If you cannot see through the tank to see the fuel level, just fit a right angled festo in the top front face of the tank & another at the bottom. Connect them with 4mm clear festo tubing & you have a sight level indicator.
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RE: Bob Cat Copy Falcon 120 Jet
ORIGINAL: Grodus Hi All, I had planned to use the 50oz DuBro fuel tank in my Falcon as a lot of others had. I re-shaped the formers to accomidate this tank but found that I had to move the tank slightly forward to allow access to the wing bolts. Also, because of the forward spar, I was not able to get the tank to sit level. I have recently discovered that a 64oz Gulf Lite charcoal lighter fluid bottle will fit completely reward to the rear wing tube and allow access to the bolt holes. It also sits level in the fuse. I will be installing a Super Bee and may or may not need a little extra fuel but I figure i can always leave some off. My question is: This fuel tank will not be transparent as it is white. Do you think it would be a disadvantage to not be able to visually check the fuel level after a flight to get some idea of fuel consumption without defueling and measuring fuel remaining? Thanks, Grodus Dave |
RE: Bob Cat Copy Falcon 120 Jet
Guys,
i would like to use Dubro 50 OZ + another tank at least 16oz - any recommendations on how to do ths ? |
RE: Bob Cat Copy Falcon 120 Jet
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ok guys, i spent some time checking how much residual fuel i had in the tank after the last flight. I had 175 ml left and the UAT was bubble free. I cheched how much fuel i actually uplifted, i left it a bit light, to aid the take off, it was 1750 mls uplift.
I then checked my cg, with UAt full, smack on. Then I filled the tank to the 1750ml mark and checked how much more nose heavy it was. It is quite a lot more, it took a weight of 275 gms placed on the tailplane, just before the elevator to balance. I then emptied the tank 1/2 way and checked again. This time it took @ 180 gms to balance. I loooked at the fuse again to see if I could make a shorter stumpier tank to help the take off with full fuel. I then found the wifes Persil washing machine fluid. I have test fitted this bottle, it is a lot shorter, so cg should be better. It has a hand grip moulded in the bottle, which reduces the fuel capacity, but although it states 1.5 liters, it actually holds @ 1700 mls, so pretty much what I fill up with. The cap is really strong and good fit on the threads, It was bought from Sainsburys, it is called, Persil Perform, liquid gel. I have cleaned it out, applied PTFE tape to the threads, and filled with Jet A1 to test for compatability of the plastic. When installed in the model, there is a noticable difference in the length it extends fwd, will check cg change if i fit it, pending fuel compatability test. The bottle is curved on the top, which matchs better the fuselarge shape, and the curve at the bottom, should allow just enough room for the fitment of the wing attach bolts. I have just received a Jet-1A nose leg for Als Hobbies, to replace my Euro kit leg. What a beautifull piece of kit smooth action should help the nose stick, instead of bouncing. Ali will send on to me a lighter spring, when he gets them in to compare performance, but I think the one supplied should be ok. I ordered the big Boomerang not the Intro leg, as the Intro leg can only go up 2.25 inch wheel. I have a 2.75 inch wheel for the grass. Will let you know how it perfroms. Euro kit leg weighs, 100 gms ( lightened) the Jet 1a, weighs 90 gms, but can be machind down to reduce weight, but it would be a shame to touch it. I added a few extra yellow trims to the plane. |
RE: Bob Cat Copy Falcon 120 Jet
ORIGINAL: angelrcdesign Yes I had three flights on sunday. on the ali. a little trim , on the elevator, little trim up. On the ele. make sure that the top of the stab is even with the ele. NOT THE BOTTOM. The C/G is perfect at 13 inches. I even had one deadstick. and it like to glide. I did not use flaps. The Byron fan system works great at 4-1/4 outlet. I will try 4 inch outlet next , after that some props. I use spring/air Robarts. Angel Interested in your ducted fan setup. Any chance of a few closer shots around the rear end? What is the diameter of your fan? Have you compared Props to the Fan yet? Im thinking of setting up ducted a fan comprising OS91 with ducted fan rated @ 11.5 Lb's (pounds). But I dont want to invest in all that kit if a decent prop on a OS 160 is going to do the same job. Im more likely to use a prop engine again rather than a ducted fan. Can you remember the approximate weight of your aircraft with the ducted fan. Im wondering how marginal it is for performance @ 11.5 Lb's thrust or thereabouts. Im guessing that if the Wren 44 flies it at 10 Lb's then a ducted fan would be similar if not better with the potential less weight. What is your experience or any others out there of the ducted fan set up. Any videos of these Falcons with 120, 140, 160 engine & prop combinations out there? There seems to be a shortage of info on these combinations? All info appreciated and great thread |
RE: Bob Cat Copy Falcon 120 Jet
ORIGINAL: angelrcdesign Yes I had three flights on sunday. on the ali. a little trim , on the elevator, little trim up. On the ele. make sure that the top of the stab is even with the ele. NOT THE BOTTOM. The C/G is perfect at 13 inches. I even had one deadstick. and it like to glide. I did not use flaps. The Byron fan system works great at 4-1/4 outlet. I will try 4 inch outlet next , after that some props. I use spring/air Robarts. Angel Interested in your ducted fan setup. Any chance of a few closer shots around the rear end? What is the diameter of your fan? Have you compared Props to the Fan yet? Im thinking of setting up ducted a fan comprising OS91 with ducted fan rated @ 11.5 Lb's (pounds). But I dont want to invest in all that kit if a decent prop on a OS 160 is going to do the same job. Im more likely to use a prop engine again rather than a ducted fan. Can you remember the approximate weight of your aircraft with the ducted fan. Im wondering how marginal it is for performance @ 11.5 Lb's thrust or thereabouts. Im guessing that if the Wren 44 flies it at 10 Lb's then a ducted fan would be similar if not better with the potential less weight. What is your experience or any others out there of the ducted fan set up. Any videos of these Falcons with 120, 140, 160 engine & prop combinations out there? There seems to be a shortage of info on these combinations? All info appreciated and great thread |
RE: Bob Cat Copy Falcon 120 Jet
tim777jet can you post a pic of the plane with the tank inside ?
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RE: Bob Cat Copy Falcon 120 Jet
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Guys,
First, i think we found the perfect tank - 1.9L for the falcon - made from a juice container ! What do you guys think ? plenty (!) of room left for smoke or even more fuel ! |
RE: Bob Cat Copy Falcon 120 Jet
ORIGINAL: i3dm Guys, First, i think we found the perfect tank - 1.9L for the falcon - made from a juice container ! What do you guys think ? plenty (!) of room left for smoke or even more fuel ! See post #438! Dave |
RE: Bob Cat Copy Falcon 120 Jet
Someone flew it with an OS160 and 16x10 pusher. dont know how well. There is a shortage of good pusher sizes.
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RE: Bob Cat Copy Falcon 120 Jet
Lior and all others,
If you cut off the front wing tube inside of the fuselage, you can put a Dubro 50 oz tank on the bottom, and a 32 oz tank on top of the 50 oz. The rotation rod (front tube) is not needed to go from side to side. If you do not believe me check the new Bobcat 50 models, no rotation rod, only wing bolt in its old position. Johnny |
RE: Bob Cat Copy Falcon 120 Jet
Johnny,there is quite a lot of difference between a Bobcat 50 and a 120 due to the power used.I don't think I would trust the wings from not folding up when pulling out of a split S at over 100mph plus.You have to realize you have over 13" of wing in front of that rear wing tube with the only support being from that smaller tube.You cut that portion off in the fuse and you loose all that support to the front of the wing:eek:
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RE: Bob Cat Copy Falcon 120 Jet
He is not saying to cut out the tube or remove it. Just cut enough of the tube that protrudes into the fuse. It will still do it's job as it will still be in the fuse, just not past the inside part. Just do not need it to go to both wings. It's purpose is for a anti-rotation pin and that is it. If I am wrong, then I stand corrected.
hope this helps. |
RE: Bob Cat Copy Falcon 120 Jet
The whole point of having the tube go through the fuse from one side to the other is so it has strength. Cut the middle out & you might as well not use it at all. You could hysol the outer parts of the tube to the fuse sides, but I would not trust it. The forces would probably be to great.
I suppose a better idea would be to hysol the tube in the wing, leaving about a quarter of an inch to locate in the fuse. |
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