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  1. #2751
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    RE: Bob Cat Copy Falcon 120 Jet

    if you ,think or, feel a front spar is need ,by all means use.. safer is always better.as far as the tank i made,you could put a tube through the tank seal the ends ,at the front ,,thingy,,{so called srar} location..m.a.c.- is the mean lift area of the wing..were c/g is figure from.. must be an important area ..huh..??its never at the wing tip.a prop should nead a spar ,,,,,,, if,, i understand your wing theory.. only a hole in the center .super cantalever affect....ribs are supported by .foam core,sheeting.leading edge,trailing edge..

  2. #2752
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    RE: Bob Cat Copy Falcon 120 Jet

    Rapptor

    You are getting yourself very confused, MAC in aerodynamics stands for "mean aerodynamic cord" and is nothing to do with mean lift area or were C of G is figured from, I still do not understand your reference to a prop needing a spar, please explain? "only a hole in the center. super cantalever affect"?????? the foam core, sheeting, leading edge, and trailing edge are all spars, the main spar is tapered towards the tip as the load decreases it no longer needs as much support, therefore the loading can be transfered into a lesser structure.

    If you are refering to the disscusion between Harry C and I on the Aerodynamic Center in another thread, you have not grasped the basics of the disscusion or the basics of fluid dynamics.

    Please see below:

    Harry

    Wikipedia is not an authoritive sourse of information anyone can go on there and put forward anything they like, however from the NASA web site:

    As an object moves through a fluid, the velocity of the fluid varies around the surface of the object. The variation of velocity produces a variation of pressure on the surface of the object. Integrating the pressure times the surface area around the body determines the aerodynamic force on the object. We can consider this force to act through the average location of the pressure on the surface of the object. We call the average location of the pressure variation the center of pressure in the same way that we call the average location of the weight of an object the center of gravity. In general, the pressure distribution around the object also imparts a torque, or moment, on the object. If a flying airfoil is not controlled in some way it will tumble as it moves through the air.

    If we consider an airfoil at angle of attack, we can (theoretically) determine the pressure variation around the airfoil, and calculate the aerodynamic force and the center of pressure. But if we change the angle of attack, the pressure distribution changes and therefore the aerodynamic force and the location of the center of pressure and the moment all change. So determining the aerodynamic behavior of an airfoil is very complicated if we use the center of pressure to analyze the forces. We can compute the moment about any point on the airfoil if we know the pressure distribution. The aerodynamic force will be the same, but the value of the moment depends on the point where that force is applied. It has been found both experimentally and theoretically that, if the aerodynamic force is applied at a location 1/4 chord back from the leading edge on most low speed airfoils, the magnitude of the aerodynamic moment remains nearly constant with angle of attack. Engineers call the location where the aerodynamic moment remains constant the aerodynamic center (ac) of the airfoil. Using the aerodynamic center as the location where the aerodynamic force is applied eliminates the problem of the movement of the center of pressure with angle of attack in aerodynamic analysis. (For supersonic airfoils, the aerodynamic center is nearer the 1/2 chord location.)

    Therefore the Aerodynamic center is a theoreticall center and far from being an outmoded concept the Center of Pressure is the more accurate means of establishing what happens to an airfoil section, just more complicated, the suggestion that the C of P can be infinatly behind the section is not one I subscribe to and can find no authority explanation for it happening, once an airfoil gets to AOA that no longer supports differential pressure the pressure bubble moves off the TE and collapses.

    If you can guide me to an authoritive explanasion I would be keen to see it.

    Thanks
    Mike
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  3. #2753
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    RE: Bob Cat Copy Falcon 120 Jet

    sheeting and trailing edge are all spars, the main spar is tapered towards the tip as the load decreases it no longer needs as much support, therefore the loading can be transfered into a lesser structure.
    - THIS IS YOUR REPLY - THE ABOVE STATEMENT,,........how many sprars does a wing need?????????? on a non tapered .non swept.wing, lift is, "almost", even root to tip.i work with results, not therory.i do understand your replys, and respect all your info.. math is ,not, a sceince,its an ,estamation, for the phyisical world..if not you would not need constants like ..3.14 ect.. c.f.d is the best . i use it, for cylinder head porting..volicity,pressure,cross sections..we are using this kit .turbined powered. it really was not intented for that power without .some.mods..sorry i stired up the mud..put a windex bottle in it for fuel.. add titaium spars.8 of them,go fly..

  4. #2754
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    RE: Bob Cat Copy Falcon 120 Jet

    Oh Rapptor you are funny, I needed a good laugh, but don't shout its not nice, the sheeting, trailing and leading edges will all take over the longitudinal loads from the main spar as it tapers towards the tip even the ribs act as spars in essence to stop the wing from twisting, Maths not a sceince that is funny, you are quite correct in that the Falcon 120 is not designed for the power of a turbine and all I pointed out in the first place is, that if you are going to remove the front spar, then reinforce the rear one, the Falcon has a highly tapered wing so the lift and loading dimminsh quite rappidly towards the tip and most of the load is taken at the fist third of the wing adjacent to the fus where the front and rear spars are supposed to be.

    Mike
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  5. #2755
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    RE: Bob Cat Copy Falcon 120 Jet

    THANK YOU !!!!!!!!!!!!!!!!!!!!!! AN ELECTRIC MOTOR MAKES ITS MOST TOUQRE AT ZERO RPM.. PUT THAN IN A HORSRPOWER FORMULA.. SEE WHAT YOU GET.. T-X- RPM,DIVIDED BY 5250. }THERES THAT CONSTANT AGAIN}-SO MUCH FOR MATH . DIVIED 10 BY 3 ,, SEE WHAT YOU GET.. {AN ESTAMATION GOOD ENOUGTH FOR THE REAL WORLD} BY THE WAY, THERE IS NO SUCH THING AS ,HORSEPOWER,,.DYNOS DONT MEASURE HORSEPOWER,,,,,,, BE COOL RALPH

  6. #2756

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    RE: Bob Cat Copy Falcon 120 Jet

    Hi Rapptor, just got in from work and what a lot of posts. I did not mean to upset anyone, i was just trying to explain that both my models have front spars and as designed, these spars extends into, i think 3 ribs, (my plane is about 4000 miles away from me at present so cant confirm).
    My point abount the spar being 1 inch too short, is that it wont meet up with the last, say, (3rd) rib on either one wing, or possibly both, depending on how the front spar is positioned during assembly. In essence, in the later example, you could cut the front spar down and have it extend to just the second, because until the end of spar reaches the last rib it was supposed too, it is effectively doing absolutly nothing.
    I appreciate your point that it does not extend all the way to the tip, but if the designer wanted it to extend say 6 inches and support three ribs in the root area, then I will go with his judgement and make sure it reaches all ribs it was inteneded to. I was originally going to extend both my spars by an extra 1 rib, but after having no problems with my first falcon with about 140 flights on it, I stuck with the same design.
    With your install, I assume your front spar is pushed right in, up to the last (3rd) rib and just enough left, to protrude into the fuse. This is fine, as you are supporting all the intended inboard section of wing. The only question now, is how much extra strength does the wing gain, with a full span, spar across the fuse. I am an old engineer, belts and braces, so i prefer to leave my spar all in one, others choose not too, thats fine, but either way, if your spar does not reach the end rib it was intended too, it will be a weak spot. Mid position between the ribs is thin air.
    We are all tying to achieve the same goal and enjoy our flying and assist others in getting airbourne as fast and safe as possible, there is more than one way to skin a cat and that is why it is good to post up on here, I have learnt a lot and any new guys, please dont be put off and post up no matter how silly you think your question may be.

    Hope that clears my point up a bit. cheers Tim

  7. #2757

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    RE: Bob Cat Copy Falcon 120 Jet

    Can "O" worms anyone!..lovely juicy worms!..warm sweet worms anyone!

    when you look at this little plane carefully you will notice many very good things that the designers put in place..but hey EVERBODY is an engineer and a proffesor and a rocket scientist..Im happy with the theory that 3 chopsticks are harder to break than 1

    Works for me!

    gotta love all the big fancy words and meaningless explanations when most of us have never been trained in aerodynamics and rocket science,way to much information for the little guy whos having fun at the field with his little plane...I mean info is good and usefull but...

    PLEASE DONT FORGET TO HAVE FUN!

    cheers

    Haydn

    oh yes enjoy the worms the can is still warm!

    he he he

  8. #2758
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    RE: Bob Cat Copy Falcon 120 Jet

    all things are built by the lowest bidder,and installed by a doper.. :word: dont ever think an engineer cares about quailty,just bottom line.he was trained that way

  9. #2759
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    RE: Bob Cat Copy Falcon 120 Jet

    Everybody is entitled to their opinion, no matter how wrong they are.

    Engineers are trained to design for safety, it's only after they become corporate that the bottom line symptom starts.

    Mike
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  10. #2760
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    RE: Bob Cat Copy Falcon 120 Jet

    maybe" the trained pros."can find away to keep styrofoam from wrecking the space shuttle.. get real!! they burnt up 15 astronaughts,,there "not sure" ,so we need test pilots and wind tunnels..they,{pros} desiged the "o" rings on the shuttle. killed all thoes people.not enougth insulation on the ,twin towers,killed all those people.automotive recalls are a daily news event for ,fires,tires,steering,brakes,wiring.get my drift??mechanicaly mined people are born that way.like art and music. kelly johson was the best aircraft designer {sr 71} ,,ever,, no books,, no bull!! and yes ,you are intitled to be, wrong.

  11. #2761

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    RE: Bob Cat Copy Falcon 120 Jet

    Too bad you are completely unaware of any pesky facts!

    The External Tank does not use and "styrofoam" (styrene). Most of the TPS (Thermal Protection System) is made up of BX-265, PDL 1034, and NCFI 24-124. These are polyurethane based products. Are you implying that there was a previously unknown 8th astronaut on the Columbia when she was incinerated in the skies over the USA in '03? WOW!! You know some stuff!!!!

    As expected, your description of the Challenger accident "they,{pros} desiged the "o" rings on the shuttle" demonstrates a complete "non-understanding" of the event. Yes, the SRB field joint O-rings were where the booster failed, but it was far, far more complicated that that. Remember: complex systems fail in complex ways. The temperature that night was extremely low for the Cape, the leak check pressure used to check the seals had been being ratcheted up for years leading to blow-holes in the insulating putty allowing high temp gas access to the seal interiors, etc.

    When dealing with human spaceflight, you are ALWAYS talking about the very limits of performance. Taking materials and technology to the very edge of what is even possible. Therefore you can certainly expect failure once in a while. It is all a game of risk reduction and management.

  12. #2762
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    RE: Bob Cat Copy Falcon 120 Jet

    Never mind your not worth the effort.

    Mike
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  13. #2763

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    RE: Bob Cat Copy Falcon 120 Jet

    I thought this was a thread about the Falcon 120? Why don't you guys get a hold of Obama and go argue in the Whitehouse over a beer, while the rest of us build model airplanes? I'm just saying.....
    Nosen Cessna 310 Club Number 12

  14. #2764
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    RE: Bob Cat Copy Falcon 120 Jet

    Point taken.

    Mike
    My Gast is Flabered.
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  15. #2765

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    RE: Bob Cat Copy Falcon 120 Jet

    Yes guys this a Falacon website and some guys have made sterling progress making some components to enhance the basic model, like canopies undercarriages and fuel tanks. Regarding fuel tanks, it is sensible to try to postion the tank as close to the CofG as poss, but this is awkward, due to the shape of fuse and the two spars.
    I originally flew with a 2 liter coke bottle, which is longer and thinner than my prefered tank now, which is a persil bottle, shorter and taller. There is a slight difference in the models feel when full of fuel, with the two different tanks, but the model flys so well that it is not appreciable. I also have a smoke tank, which i could only fit in front of the fuel tank, so again, a large shift in C/G when this is full, again the model takes it in its stride. There are a lot of differnet configurations of Falcon out there and as long as we keep posting our results, then we can all learn. Some guys have modified spars, which is great, post up your findings, my engine (home made) is heavier than comercial so my plane will be slightly more loaded than others, but i have not modded the internal structure of the wing. I use a carbon rear spar and the ally front one, both extended by 1 inch for correct fitment. I have not experienced any fluuter or deforation of the wing structure, but i do not push the model to extremes. I have around 200 flights on the same spars.
    The booms on the later model, did not quite fit up snuggly against the Trailing Edge of the wing, as the old model booms did, so i filled the gap with scrap balsa and also fitted a thin strengthening plate of balsa in this area. I posted quite some time ago, the differences betwwen the models. If you are just starting out on your new jet adventure, rest assured the model is a pleasure to fly, will fly on relatively modest power and is very forgiving. Do the basics and get her in the air, the best tips here, are keep a nose high attitude when she is sitting on the ground (no slip stream air with a jet) to get her off the ground, or you will driving around the field at a fast rate of knots and not flying. I made this mistake as have others. The fuel tank postion is not a major issue, fit a pop bottle, get some air time then play with it to tune it as you like. A trailing link U/C is a really good mod, but i flew mine first with just spring wire and foam wheels. I actually found a video of my very frist flight yesterday, made me laugh. I had so many years work in the engine alone, i would have been heart broken if she didnt fly. Even if it did, woould the engine flame out in flight with different angles attack, how long would the fuel last. In fact i set the throttle at about 1/2 way and flew for about 7 mins hardly touching the throttle, in case she stopped. 90 degree stiff cross wind as well, but got her down. Typing this i still have a grin on my face, its what it is all about, Get Em Up There!

    Cheers Tim

  16. #2766
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    RE: Bob Cat Copy Falcon 120 Jet

    worketman- you are ,for sure ,,trained.. you guys allways have a back door excuse for all the trouble you cause.!!!im not sure but i would hope, an alloy metal, would be impact safe, from any kind o foam..over paid, semi skilled." you" must be incharge ..the facts stand, piss poor design killed people.. ps, nice useless numbers of a plastic that doesnt work- psu 349- ffh 50- kk-200-9 what a joke..

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    RE: Bob Cat Copy Falcon 120 Jet

    thank you for useable information.. tim 7777 .. you have made the aircraft fly ,in its original design ,better.and safer.thanks to all who have taken there valuable time to make this aircraft fun to fly.. my head hurts...

  18. #2768

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    RE: Bob Cat Copy Falcon 120 Jet


    ORIGINAL: RAPPTOR

    worketman- you are ,for sure ,,trained.. you guys allways have a back door excuse for all the trouble you cause.!!!im not sure but i would hope, an alloy metal, would be impact safe, from any kind o foam..over paid, semi skilled.'' you'' must be incharge ..the facts stand, piss poor design killed people.. ps, nice useless numbers of a plastic that doesnt work- psu 349- ffh 50- kk-200-9 what a joke..
    Huh? Stop smoking crack.

  19. #2769
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    RE: Bob Cat Copy Falcon 120 Jet


    ORIGINAL: joeflyer

    Of all the Falcon color schemes I've seen to date. Yours is by far the best yet for me. Nice job once again on it. I wish I had the motivation to do mine up like that.
    Thanks, Jeff. Since this is my second Falcon I didn't want orange and white again. Ten guys (no kidding) in my club so far have bought these. I'm sure a few will never be converted but we all had to come up with different schemes so we'll be able to tell them apart. Right now there are two flying and two about to maiden. It should be an interesting summer.

    Joe

    Joe,

    Ten, no nine guys. I sold the NIB one I had with Artes Bee.

    I may have composite version to fly if the Artes Rabbit comes in as promised.
    Could be up late Thursday on the turbine install.

    bob

  20. #2770

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    RE: Bob Cat Copy Falcon 120 Jet

    Hurry up Bob, Michigan Jets starts Friday.

    Finally back on topic!

    Joe

  21. #2771
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    RE: Bob Cat Copy Falcon 120 Jet

    Well I cant fly it untill the Artes Rabbit turbine gets here...
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  22. #2772
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    RE: Bob Cat Copy Falcon 120 Jet

    I DIDNT GO TO COLLEGE,SO I DONT HAVE A DRUG PROBLEM,..HOW DO YOU KNOW ABOUT CRACK????????????????

  23. #2773
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    RE: Bob Cat Copy Falcon 120 Jet

    Derrick still have not seen your fuel cells in the Buy and Sell section just checking up to see what is going on.
    Team Airtronics and 42% Products Factory Pilot
    AMA District X AVP for Norcal

  24. #2774

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    RE: Bob Cat Copy Falcon 120 Jet

    I ordered the wing fuel cells direct from Derrick using a PM. I received them the other day and I can say they are excellent!!
    Galen



  25. #2775

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    RE: Bob Cat Copy Falcon 120 Jet


    ORIGINAL: RAPPTOR

    I DIDNT GO TO COLLEGE,SO I DONT HAVE A DRUG PROBLEM,..HOW DO YOU KNOW ABOUT CRACK????????????????
    Cause I read your bizarre writings!!


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