Aero Ex - Valkyrie 1 Design

[skippydiesel]

On 16/02/2023 at 2:10 PM, onetrack said:

I always wondered why light aircraft manufacturers didn't come up with a "two halves fuselage shell" 

 

ATEC aircraft fuselage is made in two (1/2) fuselage molds (shells) and then joined - I suspect that most other composite fuselages are made the same way,  along with wing, horizontal stabilisers, and control surfaces.

[Peasant_Pilot]

1 minute ago, skippydiesel said:

ATEC aircraft fuselage is made in two (1/2) fuselage molds (shells) and then joined - I suspect that most other composite fuselages are made the same way,  along with wing, horizontal stabilisers, and control surfaces.

I think its the way to do it. 

[facthunter]

Cockpit cut outs spoil the top half strength wise.  Most of the larger stressed bits are in the front four feet and you need to guarantee exit in an inverted situation on the ground with Low wing. The Laid back tail is only a styling exercise when used and doesn't perform as well as a vertical one does.     Nev

[LoonyBob]

On 17/01/2024 at 9:30 PM, Litespeed said:

Bob,

 

Great comments borne from experience and the fundamentals of aircraft design.

 

That Falco just is sexy, a timeless beauty. If it looks right, it flys right.

Yes, today a better aircraft might be designed but damn it's hard to beat an Italian master. No CAD, no CATIA or fluid dynamics programs just pure design.

 

This provides an Italian lesson "form follows function, but beautiful form gives beautiful function".

 

Not only does this provide a wonderful flying machine but makes the pilot and bystander want it. It's an emotional thing when you purchase or lust after a personal aircraft. Same goes for cars and bikes for fun, you don't pay top dollar for the fugly one that lumps along. No we want a machine that attracts the eye, commands the heart and satisfaction in high engineering.

 

If you can make a baby Falco as good as the original or better, you have a winner.

The Falco ticks quite a lot of boxes from aerodynamic and structural textbooks; but it gave away nothing in the looks department! A creative tour de force...

 

I'm a bit wary of DeHavilland's comment on looks; he had a penchant for using undersize fins - have a geek at the Mosquito VMC vs stall speed through the series...

 

It's funny how we get used to "conventional" looks, but our tastes vary with time... but I don't know anyone who thinks the Falco is ugly! I've had the pleasure of a close look at the Toowoomba one (Lynette's), and I have room for one in my hangar!

 

[facthunter]

For ground handling and some aeros  a LARGER fin and rudder are good to have. The DH Chipmunk one was too small and some were fitted with larger ones. The swept back tail is a styling exercise only on anything that doesn't go over M.6.. Nev

[skippydiesel]

No engineer but isn't the fin (& rudder) size , relative to the fuselage length (principle of moments) ie an aircraft can have a small effective fin if its set a relatively long (tail cone) way back ???

Edited January 30 by skippydiesel

[Geoff_H]

Yes.  Gliders have a very short relative tail to aileron distance so much more rudder is needed to counteract adverse aileron yaw.  It's as you said a matter of rudder force times distance of the rudder to the centre of gravity creating a moment on the aircraft.

[facthunter]

Gliders are a sophisticated design all over and don't have to handle the effects of a propeller OR a disgusting square sectioned fuselage to much up the rudder effectiveness.  Nev

[spacesailor]

Doesn't the ' rudder hight '  get effected by the hight of the 'canopy ' , if they are the same , a ' blanketing ' effect will have an adverse effect on that rudder .

spacesailor

[facthunter]

Possibly. If there's any decent airflow it would be better than having something like a phone box.as as cockpit. A Round or oval fuselage cross section aft of the wing helps good flow over the fin and rudder.  Nev

[LoonyBob]

11 hours ago, skippydiesel said:

No engineer but isn't the fin (& rudder) size , relative to the fuselage length (principle of moments) ie an aircraft can have a small effective fin if its set a relatively long (tail cone) way back ???

Yes, depending upon the degree of destabilisation from a tractor propellor...

The Thorp T-18 and Fletcher FU-24 are examples of aeroplanes with VS size reduced because of the long rear fuselage, as is the Lancaster... it's called "tail volume coefficient", and is expressed as: (wing area / VS [or HS] area) * distance between wing 0.25C and stabiliser 0.25C. If you are concerned about spin recovery, that distance is often squared.

The higher the aspect ratio of the stabiliser in question, the "stiffer" it is - that is, the greater the rise in corrective force for a given angular displacement.

For non-all-moving stabiliser light aircraft, a useful rule of thumb is that the HS wants to be about 20~25% of the wing area, and the HS ~15%; and stick then back as far as the propellor requires (then watch out for the wing wake with flap!).

Cessna mostly burke the issue, by limiting the rearwards extent of the CG range such that they never need spin damping from the VS, and the pendulum stability of the high-wing layout removes the need for a powerful HS. Do NOT exceed the rearward CG limit!

The V-tailed Bonanza is just bloody dubious; the early, lower-powered ones unquestionably showed adequate stability, except for the slight dutch roll syndrome; but the higher powered ones don't stack up for spin recovery, at least on paper...

The majority of gliders (all single-seaters) are built with the knowledge that the pilot is wearing a parachute, and their airworthiness requirements don't require demonstration of a recovery from a 3-turn fully developed spin (neither do RAAus aircraft... - unless the term "developed spin" has crept into the ASTM recently!).

The Navion is probably the best basis for figuring sizes for the empennage, as Piper caught Thorp's all-moving HS disease (the maths for setting up the anti-balance tab to achieve positive stick-fixed AND stick-free stability is quite complex), and Cessna cheated. The cruciform tail Bonanzai are also pretty good.

Note that, whilst positive stability is the prime desideratum, it is possible to have a HS too small to rotate the aeroplane into the stalling attitude on landing, as the HS enters the ground effect; most high-wing aircraft push this issue, as the pendulum stability term becomes too great for, say, a Piper Cub HS. The Cub solved this by having an immensly powerful trim - more powerful than the elevator; which was made illegal for new designs after it caused  fatalities. The Maule M5 is an interesting study.

[LoonyBob]

2 minutes ago, LoonyBob said:

Yes, depending upon the degree of destabilisation from a tractor propellor...

The Thorp T-18 and Fletcher FU-24 are examples of aeroplanes with VS size reduced because of the long rear fuselage, as is the Lancaster... it's called "tail volume coefficient", and is expressed as: (wing area / VS [or HS] area) * distance between wing 0.25C and stabiliser 0.25C. If you are concerned about spin recovery, that distance is often squared.

The higher the aspect ratio of the stabiliser in question, the "stiffer" it is - that is, the greater the rise in corrective force for a given angular displacement.

For non-all-moving stabiliser light aircraft, a useful rule of thumb is that the HS wants to be about 20~25% of the wing area, and the HS ~15%; and stick then back as far as the propellor requires (then watch out for the wing wake with flap!).

Cessna mostly burke the issue, by limiting the rearwards extent of the CG range such that they never need spin damping from the VS, and the pendulum stability of the high-wing layout removes the need for a powerful HS. Do NOT exceed the rearward CG limit!

The V-tailed Bonanza is just bloody dubious; the early, lower-powered ones unquestionably showed adequate stability, except for the slight dutch roll syndrome; but the higher powered ones don't stack up for spin recovery, at least on paper...

The majority of gliders (all single-seaters) are built with the knowledge that the pilot is wearing a parachute, and their airworthiness requirements don't require demonstration of a recovery from a 3-turn fully developed spin (neither do RAAus aircraft... - unless the term "developed spin" has crept into the ASTM recently!).

The Navion is probably the best basis for figuring sizes for the empennage, as Piper caught Thorp's all-moving HS disease (the maths for setting up the anti-balance tab to achieve positive stick-fixed AND stick-free stability is quite complex), and Cessna cheated. The cruciform tail Bonanzai are also pretty good.

Note that, whilst positive stability is the prime desideratum, it is possible to have a HS too small to rotate the aeroplane into the stalling attitude on landing, as the HS enters the ground effect; most high-wing aircraft push this issue, as the pendulum stability term becomes too great for, say, a Piper Cub HS. The Cub solved this by having an immensly powerful trim - more powerful than the elevator; which was made illegal for new designs after it caused  fatalities. The Maule M5 is an interesting study.

Cessna singles are normally set up so that the landing flap reduces the stalling AoA enough to lift the HS out of most of the ground effect.

[LoonyBob]

7 hours ago, spacesailor said:

Doesn't the ' rudder hight '  get effected by the hight of the 'canopy ' , if they are the same , a ' blanketing ' effect will have an adverse effect on that rudder .

spacesailor

Only if you've got a separation trigger at he rear edge of the canopy! A badly rigged Traumahawk does, and it costs a couplea hundred fpm in climb to boot; straight-back Cessnas, Cherokee relatives, and most gliders do not. Notchback Cessnas may, depending also upon flap setting... light aircraft that get "on the step" - that is, you have to exceed the desired cruise speed/height, then push it down and set power, to get an economical cruise - are aircraft that have separation from the top of the rear fuselage; by exceeding the desired cruise speed briefly, the rear fuse sticks up into the breeze ("favourable pressure gradient"), and the flow reattaches...

 

Re gliders, Nev was alluding to the way the downwash behind the wing is taken into consideration, in order that they can thermal on the point of stall without separation, and zoom between thermals at insane speeds, also sans separation... they give NOTHING away from performance.

[Marty_d]

19 hours ago, facthunter said:

Gliders are a sophisticated design all over and don't have to handle the effects of a propeller OR a disgusting square sectioned fuselage to much up the rudder effectiveness.  Nev

Oi, as the owner of a square sectioned fuselage.... I resemble that remark!

[Garfly]

20 hours ago, facthunter said:

Gliders are a sophisticated design all over and don't have to handle the effects of a propeller OR a disgusting square sectioned fuselage to much up the rudder effectiveness.  Nev

29 minutes ago, Marty_d said:

Oi, as the owner of a square sectioned fuselage.... I resemble that remark!

Oi, oi, me too!

 

[Garfly]

It could be worse ... (but then you might need to do something with the VS ;- )

 

[BrendAn]

49 minutes ago, Garfly said:

It could be worse ... (but then you might need to do something with the VS ;- )

 

That's how good my taste is. I actually quite like this one.  Sleeker than my xair

 

[BrendAn]

[BrendAn]

18 minutes ago, Arron25 said:

Need to uplink the pic .. not the link to it🫣

yes, i don't know why it did that. will try again.

Edited January 31 by BrendAn

[facthunter]

  Put a nice turtle deck behind the wings to help better flow to the fin and rudder it will stop the oil canning too on the boxy ones. IF the fin and rudder protrude below the fuselage that's good too...  Rearward CofG is extremely risky. The horiz. tail feathers can STALL so just think what that does and I DON"T like full flying tails at all.    Nev

[LoonyBob]

5 hours ago, facthunter said:

  Put a nice turtle deck behind the wings to help better flow to the fin and rudder it will stop the oil canning too on the boxy ones. IF the fin and rudder protrude below the fuselage that's good too...  Rearward CofG is extremely risky. The horiz. tail feathers can STALL so just think what that does and I DON"T like full flying tails at all.    Nev

The HS is meant to be of sufficiently less aspect ratio than the wing, that the wing always stalls first. Not all designers make sufficient allowance for reynolds Number effects...

 

Hey, Thorpe HSs are great, structurally and aerodynamically - and, with a properly set up tab, stable too; just not forgiving of poor execution... I personally don't like the birdstrike resistance...

[Marty_d]

12 hours ago, Garfly said:

It could be worse ... (but then you might need to do something with the VS ;- )

 

Short Skyvan isn't it... I made a R/C model of this when I was about 18, with 2x .25 OS motors I think.  Never actually flew it for some reason.

8 hours ago, facthunter said:

... and I DON"T like full flying tails at all.    Nev

You must hate my plane then!

 

 

[RFguy]

that's what happens when you taxi in and dont cut the engine early enough.