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brinesharks

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Posts posted by brinesharks

  1. Hi,

     

    very interesting, i am thinking about this for some time, and did not find a reason yet on why a canard or flaps on the main wing should not be possible, given that the canard could be equipped with a trim. I understand that this would require a compensation, which I would expect can be addressed by a controller or auto-pilot.

     

    Thinking back to the time I was still flying gliders, it is not unusual that some pitch is required when using the air brakes or flaps in the final, and it is not of any concern. What would be so different with a canard-plane?

     

    I am very well missing something, any thoughts?

     

    Regards

    From my understanding, the main concern with adding flaps to a canard with such a forward CoG is that the flaps will produce an unacceptable pitch change (nose down?). This occurs because the moment is so long between the CoG and the Wing TE. A belly board style air brake might work if you just want to increase drag on finals/landing....

     

    As for speed - the weight of the aircraft determines maximum potential speed. The drag affects how close you get to this potential speed. So, build light and make it 'smooth'. That's why just adding a bigger engine doesn't necessarily work - the added weight can negate any real benefit of more thrust. Think 'light is right' :cool:

  2. Brine,

    the Airjeep is REALLY ugly....:D

     

    thjakits

    Yup - a case of function over form! It was apparently designed for agricultural work (don't know if that means spraying) - would have had an exceptionally short take off run with all those lifting surfaces. The undercarriage is the trailing link type so it would have coped well with outback airstrips. Unfortunately I think people would still tease you about how ugly your plane is...:scared:

  3.  

    The Avanti has a traditional elevator. The canard and the main wing provide the lift.

    All three surfaces could be lifting surface depending on the CoG. Modern (conventional layout) fighters like the BAe Hawk have a rearward CoG for manoeuvrability so the horizontal stabiliser actually produces and up-force during level cruising flight. Technically the Long Eze could have a much smaller canard (and hence more 'efficient' - the wing actually picks up the slack) if the CoG were moved way back. The trouble is the aircraft would become more and more unstable as the CoG moved rearward. The main reason on the Long Eze that the CoG is so far forward (and everyone struggles with balancing it) is to produce safe 'unstallable' handling characteristics. It does mean the wing isn't flying at full efficiency though...but don't go changing a good design on my say-so!:D

  4. The Atlantica looks great - not surprised they reduced the sweep - would have been quite inefficient at the high angle of sweep they originally had. The fins will make it a bit more predictable than a wing-only design. I wish them every success - it would be great to see flying wings gain some popularity - remember that canards were frowned upon 40 years ago! No one in their right mind would build one.... :rolleyes:

     

    You're right about the price - outside my budget before I even start! My concern with building a pure flying wing is that no one really has a good explanation of the spin characteristics. Even though I don't intend to go about spinning my homebuilt, I would like to know that I can recover if it accidentally happens.

     

    Hey - here's a canard, three surface (or more?) prototype built back in the 1960s in Australia. It never flew but the design work was used to build the Transavia Airtruk (weird looking thing itself). It's called the Airjeep by Pallerini:

     

    http://i132.photobucket.com/albums/q37/brinesharks/DSCN0023.jpg

    http://i132.photobucket.com/albums/q37/brinesharks/DSCN0031.jpg

    http://i132.photobucket.com/albums/q37/brinesharks/DSCN0026.jpg

    http://i132.photobucket.com/albums/q37/brinesharks/DSCN0028.jpg

  5. brinesharks!

    (How the hell did you make up this name? :)))

     

    Okay, I would say to "compare" the Long with a Eurofighter is a long shot, but definitely worth bragging rights!

     

     

    Hey - this is the "Canard" forum isn't it? I just like canards - big fan of Rutan but also like the canard in all it's forms! Also, love flying wings.....

     

     

    Actually I saw clips of a F-18 where one elevator goes up and the other down, so there might be "aileron" mixed in there too..

    The Tornado doesn't have ailerons (has spoilers though) and uses 'tailerons' like the F-18 for roll control. Must be an awfully strong pivot...

    There was one story of an F18 pilot in the gulf that had one entire side of the horizontal stabiliser shot away and didn't notice until his wingman told him! The stability system is that good :envy:

     

     

    In any way, this is NOT for the basic, lowtime sunday afternoon flier, but for the "experimenter" looking for the last pit of performance.

    If you are that kind of guy you probably use a check list anyway...

     

    My question is more about finding numbers and devices (mechanical) to do this safely...

     

    thjakits

    Sounds great - starting with a Long Eze is probably smart.:cool: I think if you started with the initial mission profile - deciding on what you want to achieve (ie. faster cruise, lower SFC, shorter landing t/o or landing run). Then calculate L/D for various configurations and you would soon know if it's worth it. You would have to factor in the additional weight of the variable incidence mechanism(s). Be careful though, if you keep going down this logic path you might be tempted to build a flying wing!

     

    I have briefly tried to find some theoretical stuff on a variable incidence canards. I'll keep searching but you might find it becomes focused on pitch-control canard rather than lifting canards (like the Eze's).

  6. Very nice - looks more like the Q2 with the cowl cheeks. The colour scheme should add some interest - all white models can disappear pretty quick on a cloudy day!

     

    With homebuilts though, a lot of the scale detail will be totaly different on each machine. Did you manage to contact Tom? I'm keen to hear an experienced pilot talk about flying the Q1.

  7. Very nice - looks more like the Q2 with the cowl cheeks. The colour scheme should add some interest - all white models can disappear pretty quick on a cloudy day!

     

    With homebulits though, a lot of the scale detail will be totaly different on each machine. Did you manage to contact Tom? I'm keen to hear an experienced pilot talk about flying the Q1.

  8. Sorry to ask such basic questions, but I am a budding aerodynamicist and would like to do a few calculations on the Long Eze design. Could anyone help me with the following dimensions? (purely for mathematical calculations - not to build anything):

     

    1. Wing span

    2. Sweep back angle of LE

    3. Chord (Root)

    4. Chord (Tip)

     

    I have access to a friend's plans but won't see him for a while - I'm keen to get started on the calcs. :banana:

  9. Thanks for the reply!

     

    My idea to build a Vari or Long is not to get a cheap and fast airplane fast, but to enjoy the building "the best/slickest/fastest" I can.

    I make a living flying, so this is not the concern for me....

     

    So if laminar would bring a few kts I would try it, however the goal is not loosing any low speed properties...

     

    To the canard:

    Why should a trimable canard be unstable??

    The canard itself is stable, isn't it??

    So my rational (..which may not be rational after all :)) is -

    If high CL at max speed is not trimmable by elevator only, why not change the incidence angle (?).

    IU the max CL causes a high AOA that is not trimmable by elevator any more and needs excessive stick-forces....

     

    This would probably be a rather small amount (3-8º ??), It also can be a slow electric-motor or a long (manual) handle with little effective movement on the canard.

    If the canard is stable it should not become unstable by changing the incidence.

    To protect against "un-intended" stalls on the mainwing one could limit the aft-stick movement with application of lower incidence. So pulling aft will only generate a faster minimum speed. Increase incidence (Return Canard to original setting) and one gets the full range back....

    I do understand that things get more complex here, but I wonder what the benefits regarding speed would be.

     

    Ever anyone tried a full flying canard?

     

    Best Regards,

     

    thjakits

    One thing that should be kept in mind is that with all-flying canards, particularly on high performance jets (Eurofighter, etc) it is theoretically possible to stall both the canard and wing. This leads to a 'deep' stall where none of the horizontal control surfaces function and therefore you cannot recover. This is avoided by stability enhancement systems which prevent the hazardous control inputs. It's a fairly unique area of aerodynamics that you are delving into...

  10. If you are still interested, try these plans:

     

    http://quickiebuilders.org/QBA05/qba_021.htm

     

    Building a model from them should be ok - they do include instrument panel drawings plus the building 'handbook' which includes a lot of dimensions.

     

    As for the 'Super Quickie' it's a bit of a concern that people would try to build a full-size homebuilt form these drawings, but for a model they should be ok:

     

    http://quickiesource.com/

  11. Can you define "efficient"? Payload, range, speed, etc?

     

    Here's a quote from "Aircraft Flight" (Barnard & Philpott , 1995)*:

     

    Since both surfaces on a canard produce positive lift, the overall area, total weight and drag can be lower than for the conventional arrangement.

     

    They go on to discuss the arguments for and against the view that canards are 'unstallable'. Also:

     

    The main problems with the canard configuration stem from interference effects between the fore-plane wake and the main wing. In particular, the down wash from the fore-plane tilts the main wing resultant force vector backwards, thus increasing drag. By careful design however, the advantages can be made to outweigh the disadvantages and highly successful designs by Burt Rutan such as the Vari-eze....provoked renewed interest in the concept.

     

    So, it comes back to efficiency for a given mission. The canard design is also "efficient" for fighter aircraft that need to do tight manoeuvring as the canard produces immediate lift (unlike a tailplane which usually produces a down force).

     

    An interesting thing to throw into the mix is that a lot of the canards discussed on this site have pusher engines. D Raymer in his book "Aircraft Design a Conceptual Approach" highlights that having the propeller too close to the trailing edge of the wing will significantly reduce it's efficiency and therefore overall performance will suffer and vibration problems may occur.

     

    *BTW this book is a great introduction to aerodynamics and stability - blows away a lot of myths about aircraft flight.

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