News:


Advertise Here

  • June 25, 2022, 04:33:11 AM

Login with username, password and session length

Author Topic: Fuselage cross section  (Read 12834 times)

Offline Luis Strufaldi

  • Trade Count: (0)
  • Ensign
  • **
  • Posts: 34
Fuselage cross section
« on: November 19, 2015, 04:43:39 AM »
My question today is about the influence of the fuselage cross section regarding wind. Let me explain

There's basically two types of fuselage cross section: Square (like many tradition planes - a nobler, for instance) and Round (like the molded shell type planes, say a Yatsenko Shark).

Does the round cross section improve wind penetration or cross wind handling any better then a squarish fuse?

Considering that putting a round fuse together requires use of a special jig (Al Rabe's videos comes to mind), is it worth the hassle form the engineering/handling standpoint or is it just a cosmetic feature?
Luis Strufa

--------------------
After 30 years in this hobby, I think I'm finally moving up to "Beginners class"!

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12512
Re: Fuselage cross section
« Reply #1 on: November 19, 2015, 10:21:02 AM »
Hey Luis:

I suspect that a fuselage with rounded top & bottom and straight sides is going to be very similar aerodynamically than an elliptical fuselage.  So I don't think there's a great advantage to a fully round fuselage in that regard.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Lauri Malila

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1517
Re: Fuselage cross section
« Reply #2 on: November 20, 2015, 04:47:30 PM »
I'd say that aerodynamical  difference is too small to be noticed.
But structurewise, round cross section, and especially molded structures with double curvature, manage with less material for same stiffness. And less material equals less weight, low weight of components far from cg is allways good.
I have seen this many times when people have duplicated Yatsenko designs but with classsical construction methods, they just don't perform as well.

L

Offline Chris Wilson

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1704
Re: Fuselage cross section
« Reply #3 on: November 23, 2015, 06:52:37 PM »
Would have thought that a more square cross section would knife edge better in the overheads since the air can't slip around the section as easily
MAAA AUS 73427

You have enemies? Good. That means you've stood up for something, sometime in your life.
 Nothing in life is so exhilarating as to be shot at without result.  It's not enough that we do our best; sometimes we have to do what's required

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12512
Re: Fuselage cross section
« Reply #4 on: November 23, 2015, 07:28:57 PM »
Would have thought that a more square cross section would knife edge better in the overheads since the air can't slip around the section as easily

If you do the math on the centripetal acceleration you'll find that it provides all the lift you need.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Igor Burger

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 2098
Re: Fuselage cross section
« Reply #5 on: November 24, 2015, 12:47:30 AM »
round cross section, and especially molded structures with double curvature, manage with less material for same stiffness.

sure? depends how you define "stiffness" ... speaking about bending stiffness, I would say that square is much better ... speaking about torsion, round will be better, but I saw broken fuselage in flight because of bending forces, never torsional.

Offline Igor Burger

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 2098
Re: Fuselage cross section
« Reply #6 on: November 24, 2015, 12:50:30 AM »
If you do the math on the centripetal acceleration you'll find that it provides all the lift you need.

sure? :- )))))


Offline Luis Strufaldi

  • Trade Count: (0)
  • Ensign
  • **
  • Posts: 34
Re: Fuselage cross section
« Reply #7 on: November 25, 2015, 04:07:49 AM »
Basically what I can take is that the shape of the fuse does not influence (or minimally influences) how a plane handle wind, either headwind or crosswind. The major gain would be in torsional "inertia", or simply put, it would handle torsional stress better.

But only if the fuse is moulded, right? I mean, to have this gain, we are talking about a fuse made from a single piece of wood "bent" to a near "tubular" (or an elliptical) shape.

Would a "planked" fuse have the same torsional rigidity?
Luis Strufa

--------------------
After 30 years in this hobby, I think I'm finally moving up to "Beginners class"!

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12512
Re: Fuselage cross section
« Reply #8 on: November 25, 2015, 10:01:21 AM »
Basically what I can take is that the shape of the fuse does not influence (or minimally influences) how a plane handle wind, either headwind or crosswind. The major gain would be in torsional "inertia", or simply put, it would handle torsional stress better.

Yes, except for the indoor stunt class that Igor refers to, where you fly 5 second or longer laps on really short lines, and use side force generators to make up the difference.  I assume that these planes would not handle wind very well.  I'm pretty sure that Igor was just tossing that out for the humor of it.

But only if the fuse is moulded, right? I mean, to have this gain, we are talking about a fuse made from a single piece of wood "bent" to a near "tubular" (or an elliptical) shape.

Would a "planked" fuse have the same torsional rigidity?

A molded fuselage is going to have the greatest rigidity/weight, a "planked" fuselage or even a rectangular "box" fuselage will come in second, and a profile fuselage would come in last.  That's kind of a sweeping statement that's subject to all sorts of modification depending on what materials people are using, but given the same materials it holds.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Air Ministry .

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 4450
Re: Fuselage cross section
« Reply #9 on: November 25, 2015, 04:28:57 PM »
Its important on a box / flat sided fuse , not to have it to narrow at the tailplane .
A good 3/4 at the leading edge , maybe an inch . Aft of the hinge ( at ) it can taper in more .

The ' box ' type fuse can still form a cone. A Square one ! .

its a pity it isnt the underside .


Probly the most important thingo is the vertical stabaliser , for consistant line tension.
Mr Compostellas ' Airfoiled ' set up is pretty hot , Almost symetrical Finwith outside of rudder flat .
Though he uses a curve on the inside face .

You can see on this Spitfire underside view the aft fuse. taper set up . This gives a broad Stabilizer Mount and better ?? torsional ridgidity ,
Wing to stab . Or keeps the Flying Surfaces true !



You need to glue the things togeter fairly well if your flying in good sailing weather , an Silk is good on an I beam type , as
you can put the fuse over your knee and pull the tips up and down a few inchs without breaking it . A D tube might snap
if you test the beam strength that way .

Heres a PLANK Spit Fuse , the formers and plank edges are beveled .


I started one of these SQUARE  ( split at shoulder hight , built inverted ) then cut the lower rear edge and Beveled formers under
to a std. angle through . so its pretty simple . After youve figured it out on paper . And That ones Not Fat aft , a straight side
to sternpost . Was good in the wind , to twang .018 laystrate in square bottoms , and pulled like Eck in 20 Knots, downwind/ manouvreing.

Offline EddyR

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 2539
Re: Fuselage cross section
« Reply #10 on: December 20, 2015, 06:48:56 PM »
Having built two Bearcats with round fuselages I have seen no difference how they fly compared to the more conventional body design. Things that do effect them are low wings and dihedral. Once these are trimmed  they fly the same.
Ed
Locust NC 40 miles from the Huntersville field

Offline Chuck_Smith

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 682
Re: Fuselage cross section
« Reply #11 on: December 26, 2015, 05:17:38 AM »
To he original question, YMMV but I think the pilot's flying skill and ability to trim the ship trumps the fuse shape.

Aerodynamically? Unless the wing is mounted significantly above or below the fuselage centerline I (again, YMMV) doubt it would make a difference, and it might not in any case.

I believe one could, theoretically, make a case that a square cross section might ever so slightly increase pitch response ( at the cost of drag ) but it's an esoteric argument at best.

All of the above is IHMO and opposing viewpoints will be welcomed, lol!
AMA 76478

Offline Air Ministry .

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 4450
Re: Fuselage cross section
« Reply #12 on: December 26, 2015, 08:30:34 PM »
If We explore outside parameters to establish principles , we have a better understanding of the subject .  %^@ LL~ LL~. S?P H^^

Did a scale profile Meteor NF11 , with the Oriental Wing , back 1999 . Stupid enough to part with it as it weighed 60Oz.
Now find they fly fine at 60 Oz. on 70 ft. of .018. HOWEVER on 60 ft. of .015 stainless . a 58 In long 7 in deep profile fuselage
has a ' slight ' tendancy to stretch the lines , and in the gusts. In fact a vertical eight has a 90 degree ' hesitation ' in responce on the
reversal of movement . Which is disconcerting .



Looking at the Fuselage , 58 in overall length , 1/2 in width , we can deduce it has a 116 to 1 aspect ratio . Longitudeinally .
Nother pitcher to rub the point in .



Itchin to replace the sucker for ' some time ' now . Line tesion , at least the lack of it , isnt really an issue . LL~ . . . .  S?P. H^^

VERTICALLY , the Width / Breadth must be around 1/14th !

NOW an OPPOSITE evaluation Might Be Thus .



Aint No Fuselage !

« Last Edit: December 26, 2015, 09:07:37 PM by Matt Spencer »

Offline Air Ministry .

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 4450
Re: Fuselage cross section
« Reply #13 on: December 26, 2015, 09:30:26 PM »
If we look at a UNRESTRAINED object in WIND , traveling , either it moves with the wind, restrained by INERTIA & Gravity and suchlike .
Cross Wind ( lateral ) being present only twice per lap , in level flight. Manouvres get trickier !

The Dreaded Airship maybe gravity isn't the issue , with its anti gravity !.  :o But Figured Helium / hydrogen filled wheels ( tyres ) still have say 3 Oz. inertia even if filled with Neg. 3 Oz. of Gas . :P >:( >:(

[img][/https://c2.staticflickr.com/2/1295/4675196173_3939939f34_b.jpgimg]

A FLAT ( vertically) ARROW can be more efficient . or theyed be MADE like that !

[img][/https://s-media-cache-ak0.pinimg.com/736x/30/1c/f5/301cf5bd0eb8b663392b4428b032b3ed.jpgimg]

Bullets apparently , the rifleings a bit awkward if theyre SQUARE .  ;D





Thus we can deduce a flat plate will have significant cross wind resistance , and a ROUND fuselage the Minimum , for the cross sectional area ,
If we are utilisinf Fixed Dimensions due to structural / strength considerations . Preumeably a Flater Round fuselage would be better still at ingnoring X Winds.




Offline Air Ministry .

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 4450
Re: Fuselage cross section
« Reply #14 on: January 02, 2016, 09:28:09 PM »
Hyrumph



Advertise Here
Tags:
 


Advertise Here