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Author Topic: Whats Eveyone Got Against Short Noses , ANYWAY .  (Read 1686 times)

Offline Matt Spencer

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Whats Eveyone Got Against Short Noses , ANYWAY .
« on: July 06, 2017, 09:55:44 PM »
Says He after reribing the fin & Swiss Cheesing the rudder posts of a semi scale Typhoon , The Props about 10 in from the Mainspar / Center of Gravity . 8)

One Assumes Light Motors came about due to long noses being required , for fuel space and suchlike , after all , you dont see long noses on Combat wings . S?P

If One Could Cut the Nose Length IN HALF , wouldnt the Aeroplane Fly Better . Less polar moment of inirtia there & half the  Moment for gyroscopic precession

ETC ETC .


Offline Matt Spencer

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #1 on: July 06, 2017, 10:00:07 PM »




Looks Like al rabes got a lot to anser for , here .  :## ;)

Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #2 on: July 06, 2017, 10:50:33 PM »
Less polar moment of inirtia there & half the  Moment for gyroscopic precession

   Yes on the first, no on the second - torque is torque, it doesn't matter where it is applied.

    The answer is that you make it whatever length is required to make it balance and to fit all the necessary parts inside. Mine is as short as it can be and have a conventional front end layout, with about a 6 1/2" space for the tank.

    Brett

Offline jim gilmore

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #3 on: July 09, 2017, 07:32:59 PM »
i would not consider combat wings as stable.
i myself think nose length in real planes had more to do with fit and function.


Offline Matt Spencer

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #4 on: July 09, 2017, 09:52:41 PM »
Quote
torque is torque, it doesn't matter where it is applied.

For every force theres an equal and opposite force , according to Pythagorus of hodini or somebody . If youll bear with me a miute .  :P

SO ; if we look at the EXTREMES , say the restraint was at a infinitely long , or infinitely short distance ( as in zero ) theyred be a differance
in MOMENT of Restraint ( to the tourgue reaction .)

At a guess , half the roll coulple is from the flying surfaces / aerodynamics . Half from restraint - as in lines and tip weight ( counter measure - at Times . At least an Inertial restraint .  >:( )

Then if we Define the Tourgue = Thered be the aerodynamic resultant due to the Revolving Propellor , The Translator or Transferer
of the rotational force . Being angled ( the blades ) the thrust is anoter resultant .

If THAT were a infinite distant Fwd or zero , its tracking around in holes and clumps in the atmosphere ( air ) would presumably be not the same leverage at either extreme .

Then theres drop off & acceleration .  >:( as when the loads off in a tail wind , or ' hole ' in the air . amongst other things , there less transferance from the prop .
and Conversly - Accleratng from there , if only relative to the atmosphere / air  - the Rotational Interaction is Stroger under heavy Load / Aceleration .

Assuming the Vert stab / Empenage are ' steering ' against this , and the wing restraining lateral rotation ; as weve said , at a guess 50 %
for the sake of a figure ,

one would assume say the prop distance to the C. G. / Aerodynamic Center would be of some relevance , due to ' p ' ,
 what Id call " Prop walk " -
where if say the load there is more about the bottom ( of the prop ) it tends to run to the right - like it was scuffing the deck - perhaps .

realise this is all rather non specific - but i think for visualising effects relevant , Then one 'd work out the relevant Maths Equations .  :o VD~




 
Quote
i would not consider combat wings as stable.

Flying one of Gibsons Cockroach Combat wings , with a Diesel in it , Fwd a tad , on 55 ft lines ; looks just like this :



Tho light on the lines and responsive to small handle movements , grooved superbly . Enough to recomend as a scedule ' learner '
economic masterpiece. Theyre called Cockroaches as theyre hard to kill , Mr Gibson related . ANYWAY , just saying . :-X

ANYWAY , regret I cant get further pictures on just now. New Ph Camera wont seem to load here direct .
All in silver apart from the new Fin , rubbed back , Layed out the rundels last night , underwing I D stripes earlier .
Primer over the ribs where sanded & ' gone thru ' corrected with balsa cement - primed ; it all looks good - or o.k.

Pre primer was a eyesoar at some places on the ribs. So mightilly releived there , So test flights may be in a week or two .
Fairly Convinced with the creeping weight / C. G. the next one / Tempest , will need to mould the Fuse - so means a Plug .
This ones largely by no means contest wood mostplaces . Hpe Camuflge wont weigh it down , after all the effort .
Maybe tryin get enough clear on to hold out the gloop , test fly - wash in meths 7 rub here'n ' there with acetone ,
then Camo ( Humbrol enamel sprayed ) and clear .

Out with the 320 to get the primer off , bar any hollows .

Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #5 on: July 10, 2017, 09:58:02 AM »
For every force theres an equal and opposite force , according to Pythagorus of hodini or somebody . If youll bear with me a miute .  :P

SO ; if we look at the EXTREMES , say the restraint was at a infinitely long , or infinitely short distance ( as in zero ) theyred be a differance
in MOMENT of Restraint ( to the tourgue reaction .)

At a guess , half the roll coulple is from the flying surfaces / aerodynamics . Half from restraint - as in lines and tip weight ( counter measure - at Times . At least an Inertial restraint .  >:( )

Then if we Define the Tourgue = Thered be the aerodynamic resultant due to the Revolving Propellor , The Translator or Transferer
of the rotational force . Being angled ( the blades ) the thrust is anoter resultant .

   The length of the nose would matter if the propellor applied a force to the nose. By definition, the gyroscopic precession is only a torque. The nose could be 20 feet long and the torque applied to the airplane as the result of precession would be the same. 

    The reason to have short noses is to reduce the moment of inertia, and the reason to make them any particular length is a tradeoff between the moment of inertia and the ability to balance the rest of the airplane without adding additional weight, and the necessary length to contain all the parts. Assuming the rest of the airplane aside from the nose requires a particular "balance moment" (i.e needs a fixed product of the CG and the mass of the nose to balance correctly), you will always have the lowest contribution to the moment of inertia by a short nose with a heavy weight as compared to a long nose with a light weight. But of course, the long nose with the light weight is lighter and has more space to put things.

      From a practical standpoint, you make the rest of the airplane however it needs to be for other considerations (primarily aerodynamic and structural). You have (or should have) a fixed mass for the parts in the nose since you have long since chosen a particular engine/tank/pipe system. Then you adjust it to try to balance without additional weight. If it all works out, you end up with a nose that is just long enough to contain the parts, which is the minimum product of inertia you can have for that situation, and the minimum weight that you could have and still carry everything.

    Brett
« Last Edit: July 11, 2017, 09:41:21 PM by Brett Buck »

Offline Chris Wilson

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #6 on: August 14, 2017, 04:26:28 AM »
If the plane of rotation is any distance from the centre of lift (the point of which any aircraft flies around) then it will have a lever or moment arm and because plane of procession has the same central point it will have the same moment.

Surely the length of that moment had an effect?
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Offline Howard Rush

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #7 on: August 14, 2017, 12:31:24 PM »
Huh?
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Offline RandySmith

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #8 on: August 14, 2017, 03:03:40 PM »
They  Main reason  is  just balance... people hate  adding  4 ounces of lead to the nose of a stuntship, all other reasons  for the most part are   not as important

Randy

Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #9 on: August 15, 2017, 10:06:38 AM »
If the plane of rotation is any distance from the centre of lift (the point of which any aircraft flies around) then it will have a lever or moment arm and because plane of procession has the same central point it will have the same moment.

Surely the length of that moment had an effect?

To be slightly more helpful/illuminating than Howard's apt comment,

Quote
If the plane of rotation is any distance from the centre of lift (the point of which any aircraft flies around)

    First and foremost, the airplane *rotates around the CG*, period, end of discussion. The net motion of the airplane in all 6 dimensions (3 rotation and 3 translation) is based on torques applied about the CG, and forces applied to the CG.

    The center of lift/center of pressure is the point through which all the forces applied by air act. Where that falls at any instant with respect to the CG applies a torque. Note that center of pressure moves around all over the place as you maneuver, in order to apply the necessary torque and force. In steady level flight, the CP is right at the CG, as evidenced by the fact that the airplane is not accelerating in rotation, and has a constant rate. Any motion the airplane makes in any of the 6 dimensions as the result of air can be explained by varying moving the CP and varying the force applied. The fact that is moving around so much makes any attempt or value of computing the CP at any set of conditions (which is a 12-degree of freedom problem even to first approximation) more-or-less pointless.
   

    At times, airplane will appear to rotate around points other than the CG. This is an optical illusion caused by unexpected angles of attack, a combination of rotation and translation that you didn't expect and interpret as rotating around some other place.

Quote
then it will have a lever or moment arm and because plane of procession has the same central point it will have the same moment.

   As Howard has pedantically noted, "moment" means torque in this context. You are talking about moment arm or lever arm and the "same moment" and those are internally inconsistent usage. Precession is a torque, period, how far it is from the CG doesn't matter at all.  If it had a net force, applied at the prop somehow, then you would have a point, if the force acted through a longer lever arm, it would apply a torque.

     The effect that causes P-factor torque also causes a net force (because the blade with more lift also has more drag), in which case, the nose length could conceivably matter. That is doesn't and 99.999999& of the people to ever look at the effect have never even realized that there is a net force is a function of it being so small that it is lost completely in other unaccounted forces.

     Brett

Offline Igor Burger

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #10 on: August 15, 2017, 11:46:31 AM »
    At times, airplane will appear to rotate around points other than the CG. This is an optical illusion caused by unexpected angles of attack, a combination of rotation and translation that you didn't expect and interpret as rotating around some other place.


I always expect airplane will rotate around center of loop / corner / flight path radius  VD~

Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #11 on: August 15, 2017, 02:12:24 PM »
I always expect airplane will rotate around center of loop / corner / flight path radius  VD~

  Build a Profile Cardinal straight from the plans, do a corner, and tell me where it *looks like* it rotates!

    Brett

Offline Brent Williams

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #12 on: August 15, 2017, 04:31:50 PM »
  Build a Profile Cardinal straight from the plans, do a corner, and tell me where it *looks like* it rotates!

    Brett

For those of us following along (just trying to interpret the discussion and gain understanding), could you elaborate on this statement? 
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Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #13 on: August 15, 2017, 08:36:58 PM »

Quote
Build a Profile Cardinal straight from the plans, do a corner, and tell me where it *looks like* it rotates!

For those of us following along (just trying to interpret the discussion and gain understanding), could you elaborate on this statement?

    The airplane appears to rotate about a point 5-10 feet behind the tail. It's an illusion caused by the fact that the flaps are so large, that the angle of attack of the airplane looks like it is aimed "outside" the radiu of the turn. Effectively, it looks like it is pitched in the wrong direction compared to the track of the airplane.

     This is the result of trying to take a aerodynamic design intended for a much heavier airplane and keeping all the ratios and areas, but building it arbitrarily lighter. It's designed to have a pretty high wing loading, and making it heavier would reduce the effect. The Nobler, particularly a really light one, has the same problem. The size of the flaps and the rest of the design was about right for 45-50 ounces. Just changing it to be 36 ounces creates this problem and makes it much more obvious. The solution would be to reduce the flap area or reduce the flap travel.

    We did this to Paul Ferrell's Profile Cardinal right before the 2006 NATs, carving 3/4" off the trailing edge of the flap to prevent this issue. A week and a half later, he was Senior National Champion.


    Igor's airplane is properly trimmed and looks like it turns right around the corner like it was held in place by a rigid mounting with a pivot at the radius.

     Brett

   

Offline RandySmith

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #14 on: August 16, 2017, 03:10:33 PM »
I was about to say, I have seen, very light airplanes, and airplanes with the flaps too large , or moving TOO  much  that rise at the same time the rotate around a inside loop, , looks funny, as the plane looks like it would be harder for the Pilot to points, other funny stuff happens on outside loops :'-)

Randy

Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #15 on: August 16, 2017, 05:56:08 PM »
I was about to say, I have seen, very light airplanes, and airplanes with the flaps too large , or moving TOO  much  that rise at the same time the rotate around a inside loop, , looks funny,

   That's the effect I was discussing above.

    Brett

Offline Brent Williams

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #16 on: August 17, 2017, 03:46:15 PM »
Interesting that the loss of around 40 squares on the Cardinal wing was less problematic than the over-large flaps.  That 3/4" reduction in flap chord is pretty dramatic when you look at the Cardinal plans.  See the attached animated gif.

Regarding Igor's plane and and the pivot-like corners, would you attribute that to trim, design, or flying style?  (or an effective combination of all of the above) 
In context to this thread title, comparatively, the MaxBee has a quite long nose at around 12" at the back of the prop. 
It has moderate to narrow sized flap chords.  Measuring as a percentage of total wing including the flap I am getting around ~13% tip and 20%root, ~17% avg of total wing chord.  It has a very large stab/elevator at around 30%(ish) of wing area.  ( forgive me as these are approximate, very quick, measurements)
« Last Edit: August 17, 2017, 06:38:50 PM by Brent Williams »
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Offline Matt Spencer

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #17 on: August 17, 2017, 07:54:24 PM »
Its ( the Max Bee ) also got a unusual flap Horn set up in there - will have to anyalise force distribution .

Looks Like a RABE ' High Lift ' Airfoil on there , and a ' Dead Zone ' Tailplane set up , and Hes fitted the Electric Starter instead of an engine ! .

Bleedy Typhoons getting there - so we shall see , inside a month I should think .
Should have cut nose ribs to dimension , rather than thrown in 7 mm deep ones then block sanded .
How many times can you go thru sanding the covering . A coat or two of silver to go , then clear .

Offline Matt Spencer

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #18 on: August 17, 2017, 08:06:43 PM »
I KNOW !

Quote
Horizontal tail

Tselnobalzovoe plumage. Vyshkurivaetsya stabilizer of two plates glued to the "points". After the surface treatment of the workpiece separate, carefully hollow out half and glued together again, now on the entire surface of the joint. The central part of the stabilizer before installing it in the fuselage tied up to a width of 50 mm thin fiberglass. Elevators vyshkurivayutsya NZ plates 10 mm thick. Since the regulator has collected on its trailing edge thickness of 14 mm, produced a pronounced step in the transition to the handlebars. It provides low efficiency rudders at small angles of deviation, which is beneficial to the implementation of the rounded shapes of the complex. At large angles of the same performance rudders restored, and the model performs well abrupt evolution.

 :-X


Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #19 on: August 17, 2017, 08:54:00 PM »
Interesting that the loss of around 40 squares on the Cardinal wing was less problematic than the over-large flaps.  That 3/4" reduction in flap chord is pretty dramatic when you look at the Cardinal plans.  See the attached animated gif.

   Here's a picture of the airplane in question:



  Actually, it helped in three ways. Reducing the wing area increased the wing loading, which requires more AoA for the corner. Reducing the flap chord reduced the camber for a given flap (and thus elevator), which also requires more AoA for the corner. Reducing the flap area also reduced the flap hinge moment, permitting more elevator control deflection for a given line tension/speed/weight.

 An alternative fix was to add weight at the CG as ballast, to require more AoA for a given pitch rate/turn radius. This puts the airplane back closer to the design conditions, but also has drastic effects on the vertical performance. I would guess, based on the Tucker experiment (were we added 8 ounces to a pretty down-the-middle design) that to get rid of the odd look, and to match the lift characteristics to the wing and tail, it might take *a pound* or more. That would likely get you in the ballpark, but now you are trying to carry 30-40% more weight to the top of the circle. Modern engines are pretty good, if you used an Aero-Tiger, 46LA, or something really good like that, you *might* be OK, but anything less, forget it.

    Cutting down on the flap area fixes the issue (very nicely, the kid won the NATs a week later with legitimate quality flights...) and has no ill effects on the vertical performance at all.

This problem was the result of taking a design that was originally intended for a large 60-sized airplane with a much higher wing loading and mediocre speed control from a 4-2 break engine, that already had radically large flap area (probably too large in the first place, seemingly required to compensate for a shape mistake in the LE of the airfoil),  scaling it down in a fixed ratio (reducing the wing loading just by virtue of scaling effect) and reducing the wing loading  still further by removing the front-row paint job and the extremely beefy fuselage. Then, put on an effective modern engine. So you end up with vastly more flap area than necessary or desirable for an airplane of this weight.

   Point being, you can't just take any design, cut 8 ounces off the weight, scale it up or down, put in a different type of engine, and expect it to work correctly without changing something else.

   Note that the Nobler has the same issue to a lesser degree, the flaps are very famously *really big* for the airplane, designed that way because *with appearance point rules, it was going to weigh more than others were going to with minimal design and paint job*. It also used extremely weak engines compared to what you would use today, and fly at relatively low speeds, all of which tend to increase the corner AoA and mitigate the problem. The flaps are reasonable for a 45 ounce airplane with a Fox 35 and a 10-6 prop, and relatively slow laps (5.2-5.3, forget what was claimed).     If you build it with an Aero-Tiger or 46LA, use *really good wood* and get it down to 36 ounces, you are going to have problems and want to do something different.

 
Quote
Regarding Igor's plane and and the pivot-like corners, would you attribute that to trim, design, or flying style?  (or an effective combination of all of the above) 
In context to this thread title, comparatively, the MaxBee has a quite long nose at around 12" at the back of the prop. 
It has moderate to narrow sized flap chords.  Measuring as a percentage of total wing including the flap I am getting around ~13% tip and 20%root, ~17% avg of total wing chord.  It has a very large stab/elevator at around 30%(ish) of wing area.  ( forgive me as these are approximate, very quick, measurements)

     An effect experimented with an expounded on at great length in the Imitation article from 1979 (an airplane with flaps of about 17% of chord):

http://library.modelaviation.com/ma/1979/10/designing-imitation

 You might also check out the dimensions in the same way for the Thundergazer, it's probably around 17% or even smaller.

    Igor's airplane seems to fly pretty well, but he does not hold a monopoly in those sorts of corners:

https://store.flying-models.com/catalog/product_info.php?products_id=324

His one consequential change is the logarithmic flap movement, which has the effect of making the flap move less relative to the elevator as it moves away from neutral, meaning it works kind of like the Imitation with all flap segments active at low deflections, and like the Imitation with fewer or none of the flap segments moving at higher deflections. Or like you have all the flap of the Cardinal around neutral and half of the flap area in a hard corner.

  I think that the logarithmic flap movement might solve one of the compromises I had to make on the Infinity. The first Infinity was more-or-less scaled up from an Imitation, with a slightly thicker (proportionally) wing and an even longer tail moment (arm, Howard), but the same 17% flaps. It could do *blinding* corners but had to be carefully flown to not "hop" at corner exit, which is a common complaint with these type models, and  small corrections there and elsewhere required substantial (and obvious) AoA changes. After experimenting with different combinations of flap area and flap/elevator ratio, I came to the conclusion that it was going to work the best with slightly larger flaps and 1:1 ratio. and that that was the best compromise I could come up with.  I had even built and painted these flaps for the first airplane, when it had a flameout and crashed right before the 1996 NATs. I ended up with the prior airplane (with which I had done the same sort of things and the largest of the flaps I built for it).

   When it came time to build the second Infinity, I just used the larger flaps I had already built, with a few other changes, and that proved to be the right decision, it (and the third airplane which is as near a clone as I can make it with one minor change) flew/flies great.

   But I am intrigued with the possibility of removing the compromise between bigger flaps for better feel and control around neutral, and smaller flaps for improved cornering (or at least reduced control loads). Igor's system appears to accomplish this goal, Paul seems to agree, so I am looking seriously at a similar system or at least a system that permits the same thing (but is more adjustable).

Note also that this topic (like most) has come up before:
http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=2302&mesg_id=2302&listing_type=search#2306

   But Igor came up with a practical and workable system for doing it, which no one else did (and frankly, I never even seriously considered). Ideas are swell, but worthless without doing something about it.

    Brett
« Last Edit: August 17, 2017, 09:36:21 PM by Brett Buck »

Offline Brent Williams

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #20 on: August 17, 2017, 11:43:26 PM »
Thanks for the informative post Brett.  That's some great info to consider.
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Offline Igor Burger

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #21 on: August 18, 2017, 09:10:34 AM »

In context to this thread title, comparatively, the MaxBee has a quite long nose at around 12" at the back of the prop. 
It has moderate to narrow sized flap chords.  Measuring as a percentage of total wing including the flap I am getting around ~13% tip and 20%root, ~17% avg of total wing chord.  It has a very large stab/elevator at around 30%(ish) of wing area.  ( forgive me as these are approximate, very quick, measurements)

Yes, those numbers are accurate. Remember, Max Bee was designed from its begin to be electric model, so battery (400g) can be placed where I want it to be. It is only few mm from wing LE, shimmed by 2 pices of 3mm balsa, so main weight is relative close to CG. Only light (180g) motor is in the nose. It allowed me to make nose length as I needed it.

Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #22 on: August 18, 2017, 10:35:14 AM »
Thanks for the informative post Brett.  That's some great info to consider.

   While the flap discussion is interesting and relatively easy to explain/understand, the yaw axis of the Max Bee is far more interesting and intriguing to me. Particularly so because it is *diametrically opposed* to what I and most others are doing, and pretty close to the Brian Eather "Firecracker" in concept.

    Brett

Offline Igor Burger

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #23 on: September 07, 2017, 02:35:16 AM »
   While the flap discussion is interesting and relatively easy to explain/understand, the yaw axis of the Max Bee is far more interesting and intriguing to me. Particularly so because it is *diametrically opposed* to what I and most others are doing, and pretty close to the Brian Eather "Firecracker" in concept.

    Brett

I do not think there is any magic about that, I wrote small article on SSW back in 2004 I think as a reaction to some other Ted's article abou something similar - I thing CG position or so. Unfortunately when I tried to search for it some years ago, I found that pictures (showing forces, moments etc) are already away, may be I can look to my backups, they could be there ... but who knows where are my backups :- ))

Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #24 on: September 07, 2017, 11:03:14 AM »
I do not think there is any magic about that, I wrote small article on SSW back in 2004 I think as a reaction to some other Ted's article abou something similar - I thing CG position or so. Unfortunately when I tried to search for it some years ago, I found that pictures (showing forces, moments etc) are already away, may be I can look to my backups, they could be there ... but who knows where are my backups :- ))


   Yes, I recall that well. Most people here do no realize that all this stuff (electronic feedback control turning electric motors into Fox 35s, non-linear controls, active stability enhancement) was floating in the air at least 15 years ago and sometimes much longer. Most of it was unrealizable or impractical at the time, but it obviously can be done now.

     I am still not sure how you manage the yaw angle, I have tried the same approach and so have many others, almost all with spectacular lack of success.

     Brett

Offline Matt Spencer

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #25 on: September 07, 2017, 11:48:13 AM »
Quote
In steady level flight, the CP is right at the CG, as evidenced by the fact that the airplane is not accelerating in rotation, and has a constant rate.

his would be if the tailplane was at Zero / Neutral Loading .

I was actually looking for another artical , which as it tuns out , Explains -

In Turns ( In the Vertical or Hemishereical Plane ) That There is a NEGATIVE Lift at the Tailplane ( on Insides  ),
whh tecnicals Subtracted from the Lift provided  , therefore a overall lift capeability is reduced ( at the wing ) a small percentage .
Unless you have a Canard , where both ' Planes ' Are in POSITIVE LIFT .  :##



Just after the ' TED ' , there , it mentions the similar concept in LEVEL FLIGHT , a Negative Lift Tail Moment .

This is as the Center of Gravity is FORWARD of the Center of lift. Albeit Marginally .
More Discernable with say 15 % area Tailplanes than 30 % , to the pilot . >:(

Offline Matt Spencer

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #26 on: September 07, 2017, 12:04:40 PM »
The ' center of pressure ' on a souped up volkswagen ( read porshe ) as in Center of Resistance , along with the center of mass , can in some cases be behind the center of adhesion .

The Action is at 11:30 odd  >:D



Center of Pressure , would normally ? refer to the center of resistance ( longitudeinal Drag ) of the' body ' in this case ' airframe ',

The C.G. the Central Point of MASS ,

( if you had say a 1 foot sq cone , blunt end fwd, for a fuselage , the ' center of pressure ' would be somewhat forward .)

In our Case , both the 'Center of Lift '- Due to Flap Deflection altering the efective airfoil / airflow- and thus as well as the A.o.A. reletive to airstream , the center of ' resistance/ drag '
and also the center of lift relitive ( moment ) to the Center of Gravity .

Thus , if through the airfoil the center of lifts transiion ( of movement ) is osscillation , rapid , or erratic , even if the Tailplane ( & elevator ) efficiency is Stable ,
the rate of turn & A.o.A. may not be .
But thats perhaps not n ececerally relevant here .

The point being that the Center of Gravity & the CENTER Of LIFT  of the WING are not neccesarilly Co Whatsit- In The Same ( Exact ) Place . Tho Center of Lift of the AIRFRAME ( whole ) May Be .

 %^@

I suppose it does come down to If we are talking of the C o L of the Wing Alone , or the Airframe ( of which some component ( the Tail ) may be negative , and which the Fuselage
and ' any other bits ' are a component .
( Flat sided narrow fuselages negating this there , to a degree )
« Last Edit: September 07, 2017, 12:22:15 PM by Matt Spencer »

Offline Matt Spencer

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #27 on: September 07, 2017, 12:27:12 PM »
postulation at the time had it that the undulating road surface had the tyres snatching , and say a front caught - thus diverging from path .
Unlike wot yd get with a 440 dodge with all that weight in the front ,on methanol with a drop of nitro ( an easy 1000 Hp ) , to do the same job for a tenth of the cost .  S?P S?P

the complimentary pages; much clearer Here http://library.modelaviation.com/ma/1985/6/control-line-aerobatics-0 if its difficult to read .




Co Incidently ,  ^-^ the Kinked Flap rear edge , if you discern it - utilises the enhanced airflow from the airscrew ( o.k. Prop )  for a more even efficency level along them .
Cant see to many people being keen on kinked back flaps , tho .  :-\
The fact that the tailplane , as a whole doesnt all dwell in the wingwash  ( Flap Wash ? ) on occasion , as may happen with a horizontal stab ,
even if the only perception is of a ' thump ' as it goes though it - there this ' transitions ' through ( thru ) it less violently .
Perhaps this ' efficiency whilst in wingwash ' is one of the causes of people useing these ginormous tailplane/ elevators .

Look at the Horizontal Stabilizor area of a aerobatic competition Glider ( full Size ) and you Wonder How Much is Neccesary .



SO the Center of Lift of the WING moves, to a degree - with flap deflection AND Angle of attack .

Flap Deflectioncan be considered akin TO altering A o A also , As the Exit is deflected ( moved ) which would well alter the entry seperation hight , thus vertical center of resistance ( Vert Drag )

( mw~ oh dear . it does appear to be not entirely to straightforwad .  VD~
« Last Edit: September 07, 2017, 12:55:59 PM by Matt Spencer »

Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #28 on: September 07, 2017, 08:47:55 PM »
his would be if the tailplane was at Zero / Neutral Loading .

    True if you are looking only at the CP of the wing. I was talking about the CP of the entire airplane - which IS the CP. That's the part that people have missed time and again.

     Brett

Offline Matt Spencer

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #29 on: September 08, 2017, 01:26:33 AM »
Thats the problem with the English Languge , its open to missinterpretation , less so if you use lots of long pertanant specific definative words ,
Where the latin derived european languages with the automatic inclusion of tense and gender are more easilly understood .

For Instance , the French for LIFT is ' Portance ' far more suggestive & romantic .It dosnt go into Italian Easilly Via the Computor  ???

Apparently youve got a choice in German ,
Quote
erheben; heben; aufheben; anheben; ausheben; herausziehen; hinaufbringen; hochnehmen; zu Vorschein holen; aufholen; aufziehen; aufbringen; hochheben; emporheben; schaffen; fertigbringen; hochziehen; takeln; Fahrstuhlkabine; Aufzug; Stimulans

I hesitate to try ' DRAG ' wot with boy george & his predisessor Shirl from Skyhooks , you might never know where you end up .

So in future I suggest we undertake these discussions in the French Languge , to aviod any confusions .  ;D :##


The previous ' issue ' got me thinking on obvious differances in force variations ( Dynamic ) in level flight . With the ' Ridgid Elevator control Conection ' of the Bob Hunt line of thought ,
Vs the ' Dead Zone ' Floppy Elevator or Blanketed, where the ' trim ' in level flight is ' adjusted ' Via Flap initially rather than ' feathered via Elevator & Flap ' on the Above .

Surely to a degree divergant design criteria .
=============================================

Thinking , after having V recently found a M A Artical stateing Al Rabe has ALWAYS used a dead zone set up , after his Mustunt Experiments , I should be out the shed
reaming the elevator bush on my P 51 , Contemplated for some time ( 1/2 in. flat plate Stab, 1/2 L E Elev. ) PITY I didnt last week while I had the Stab. off . :(

Possable combinations now are the drooped lifting L E @ the center - shifting ' pressure point ' on the curve / sheeting there . non stable airfl;ow there .

Perhaps Similar irregularities on the ( Now Modified ) Hornier ish tips .

Diheadraled Wings Ive found to be a iota more toeie inverted . If you wander down the field as you swing thru to inverted , you wake up quick & ' tune In when ' the weave '
catches your eye . Thinking this is as the underside of the tips ( when Inverted ) are where the ' support ' starts , anyway - they all seem a trifle more responsive INVERTED with Diheadral .

Should be doing a New test Tank , too. While the Soldering Irons Out .

Offline Matt Spencer

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #30 on: September 08, 2017, 01:44:52 AM »
Apparently the bumble bee was right ,according to this .

What he is on about , is the Flow over & under DOSNT meet where it seperated , after going ' past ' the wing . Thus Lift isnt what we thought it was .
Unless its a conspiracy , these englishmen usually have an agenda              to their eccentricity .

https://www.youtube.com/watch?v=UqBmdZ-BNig&feature=youtu.be

Best one I can find , at the moment , of virtual ' flow reversal - due to A o A , at the leading edge .



My thinking is Blunter Leading edges have center of drag further foward ( Or Greater Drag at a point Fwd of the C G .

Thus a Shaper Leading Edge , theres less ' wind resistance ' on the leading edge ( Like a F104 for one extreme ).
Therefore a sharper L E Wing will fly stably with a more rearward C G than a blunt one . Presumeably . The Center of resistance being further aft .

i.e. same relationship of C G & C D , C D being further rearward . One or two other factors come into acount ,
 such as more sudden increase in Lift with the more defined ' sharply ' L E airflow Seperation .

( less Vertical Variation in seperation of flow over & under Wing .

Further out along the line of thought tho - one would assume a more CONSTANT level of ' resistance ' ( Drag ) in Rough Air , Higher Winds ( say 20 moh as an example )
than the presumably more resistant Blunter Airfoil Airflow Entry .


Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #31 on: September 08, 2017, 10:25:07 AM »
Apparently the bumble bee was right ,according to this .

What he is on about , is the Flow over & under DOSNT meet where it seperated , after going ' past ' the wing . Thus Lift isnt what we thought it was .
Unless its a conspiracy , these englishmen usually have an agenda              to their eccentricity .

https://www.youtube.com/watch?v=UqBmdZ-BNig&feature=youtu.be

Best one I can find , at the moment , of virtual ' flow reversal - due to A o A , at the leading edge .



My thinking is Blunter Leading edges have center of drag further foward ( Or Greater Drag at a point Fwd of the C G .

Thus a Shaper Leading Edge , theres less ' wind resistance ' on the leading edge ( Like a F104 for one extreme ).
Therefore a sharper L E Wing will fly stably with a more rearward C G than a blunt one . Presumeably . The Center of resistance being further aft .

i.e. same relationship of C G & C D , C D being further rearward . One or two other factors come into acount ,
 such as more sudden increase in Lift with the more defined ' sharply ' L E airflow Seperation .

( less Vertical Variation in seperation of flow over & under Wing .

Further out along the line of thought tho - one would assume a more CONSTANT level of ' resistance ' ( Drag ) in Rough Air , Higher Winds ( say 20 moh as an example )
than the presumably more resistant Blunter Airfoil Airflow Entry .

      For a bare wing, where does the Center of Drag fall with respect to the Center of Pressure?

     Brett

Offline Matt Spencer

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #32 on: September 09, 2017, 05:18:53 AM »
Quote
      For a bare wing, where does the Center of Drag fall with respect to the Center of Pressure?

Now THAT is why you cut the Flaps Down .  VD~ ;D ( took me two hours and a stroll in the chill outdoors for a smart assed answer to come to me , sorry  :) )

If by BARE ' WE ' mean flapless , perhaps theyd be pretty much co-incident . . ;D Assuming its ' turning ' . ( 'Turning' in relationship being  control line , pretty save to assume in the Vertical )

BUT , ( Jaws Theme ) ,

On a Flapped ship , theyred be THREE pretty much ' stable ' conditions , mid  level flight , mid round , & Mid Square Turn . With Transitions to evaluate between .  >:( A bit of work  * )

* std aussie expressions , That sounds like a bit of work . I think I'll Have a Beer . Id Better ask the Missus . 

The Forces magnitude I would assume , would vary in multiples , one to the other . NOT the Aussie ONES !  LL~:-[

BACK to the Question , the variation one would pressume would be in vectors of load & angle from the Empenage / rear Stabilizer . But unlikly to be outside 3/4 in variance. More Likely 1/2.
Less on these modern Blunt Aifoils .
Unless its a Sky Dancer .



Id expect these flat reflex airfoils to have a less transitory * C. P. & C. of  L. and softer flap action in the open ( Round ) manouvers ,  :P ( * less Transition OF . )

A sharp L E Plate Wing start acting like a  Ridgid Sheet ( hopefully . if it acted like a sheet of cardboard , it'd have to be top of the line , or itd fold back ). So Sheet of Plywood
is likely the analogy . As you didnt specify the airfoil . >:D

If being a flat sheet , the airflow had broken off from the L E at the top , assuming a incidance , say 10 on up .  Getting Steeper center of pressure would tend toward the center ,

And the Wake Behind would assume aft , at 50 % efficiecy that might be up 5 Deg, and likely Fwd of center a way . Thered likely even be reverse airflow fwd up over the rear surface .

SO , if we introduced a Airfoil , It'd Vary . But the Pointier ( than these new ones ) Old N A S A series , in say a 20 % if were agreeable to a " Standard ' , dosnt stall Easilly ,

So the C L will be aft of 20 % Chord . While the C D is likely Fwd of 30 % chord . If its not acting like a sheet of Plywood . Bob Hunt could put somme foam on it tho . >:D

Bobs Airfoils have been traditionally very N A C A ish , in entry , curve , etc . If not exactitude ( To N A S A ) , which I havnt checked as I hadnt considered the might , try to .

But the FLAPS are the Crux of the matter , for F2b / P.A. , unless somebody left them OFF two thirds of the Wing , and gave N A S A  considerations more than a passing glance .

Note Beringer ; naff all Flap , the Flat Egress of the Sky Dancer , but the Modern Entry : that more applicable to Rate of Roll than Vertical Turn Rate , unless Im Mistaken .& with a 2:1 Taper Ratio

So While Some flap is usefull , almost as a force divergance to induce stability in turns , If we ARE talking FLAPS , the Ultimate Extreme would be a Variable Incedance Wing . Whoops .
This might require hydraulics, electrickery , or pnematics . Unless you can think of something else . ( Well Get IGOR on to it .  S?P) Structurally itd be simple . And should turn good . VD~

A Double Action Crusader  ;). ( Just a carbon Heli Boom Spar , a few washers & Circlips and a few other things . 
if it was Neutral,  Plus Two Positive & Two Negative settings , It'd likely be simplist .

AND we could aim for 3 Ft Radius SQUARE CORNERS . LL~ Dead Serious Tho . >:(

Offline Ted Fancher

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #33 on: September 09, 2017, 11:07:27 PM »
?

Online Brett Buck

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Re: Whats Eveyone Got Against Short Noses , ANYWAY .
« Reply #34 on: September 09, 2017, 11:31:22 PM »
?

Fair dinkum.  It may be brilliantly insightful or complete hokum but I have no idea what I just read. 

   It's a trick question, of course. The (not trick) answer, of course, that the "center of drag" is exactly the same as the "center of pressure", by definition of the center of pressure, defined as the point through which all aerodynamic forces are applied, lift, drag, etc. - for the entire airplane. The fact that it moves all over the place is why it's close to pointless to try to use directly. For instance, in an inside corner, the CP first moves ahead of the CG, then moves to be coincident with the CG, then aft of the CG, then back to the CG again.

      Brett


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