Some Real Aerodynamic Questions

[Daryl J.]

The plan:  put fully enclosed fixed landing gear on a Hurricane.
The problem:  I can't make heavily curved fairings (yet) where the strut meets the wing.

The questions:

Do 90 degree angles create drag?  IE:  If an aerofoil shaped strut simply butt joined the bottom of the wing, would there be an area of unnecessary drag?

If yes, would vortex generators placed in front of the strut on the wing's undersides help?

Thanks again,
Daryl J.

[Shasper]

The front end of the strut? No I dont think so.


Shas B)

[elmayerle]

A ninety-degree butt joint between the strut and the underside of the wing would create interference drag (though less than any other angle).  You could probably put a decent small fillet fairing (it doesn't need to be extravagant or large) around the base by contouring putty and then applying PSR as needed.

[grayman]

To go a touch further: one of the reasons for the cranked wing on the F-4U corsair was to try and get a 90% fitting to the fuselage and avoid the need for large fairings (witness the Spitfire, although done very successfully). I find the Corsair and interesting aircraft, not only because it looks great, but it is a fantastic example of the choices and comprises taken during design.

Perhaps the design of the spats of the Stuka or Fokker D.XXI (hope I've got the right one- the pre-war monoplane developed by the Dutch???) might be a guide?

[Jennings]

Actually, the reason for the cranked wing on a Corsair was the requirement for a large prop to absorb the power of the R-2800, coupled with the concurrent need for long landing gear legs.  By cranking the wing and mounting the struts at the lowest point, they got shorter (and thus stronger) gear struts.

As for vortex generators, their purpose is to excite the airflow (that's what engineers say - their lives are so mundane) and keep it attached to the wing surface.  When airflow separates from a wing surface, it creates drag.  The small amount of parasite drag created by the vortex generators themselves is more than offset by the drag that's eliminated by keeping the airflow where it's supposed to be.

J

[elmayerle]

As for vortex generators, their purpose is to excite the airflow (that's what engineers say - their lives are so mundane) and keep it attached to the wing surface.  When airflow separates from a wing surface, it creates drag.  The small amount of parasite drag created by the vortex generators themselves is more than offset by the drag that's eliminated by keeping the airflow where it's supposed to be.

*chuckle* Fair jab, there, Jennings.  I'd have said "energized" rather than "excite", but that'll do. If you want a lower-drag approach than vortex generators, you could use BLE's (Boundary Layer Energizers), as were fitted to Leajets starting in the early 1980s, to keep the flow attached over the entire surface.

[jcf]

Hi Daryl,
if you look at the PZL.23 and 46 you'll note that the wing to strut interface does not use heavily curved fairings, or even a fillet.





PZL P.46 Sum

Ryan STA.




As Evan said a small fillet of filler is all you'd need to do something like the Ryan.

The Avia B.35 is also very simple.






Cheers, Jon

[kitnut617]

To replicate something like this, I've used thick (slow) superglue,  I cut the nozzle so there's a larger hole in the end. I then place the parts to be glued so you get a 'V' and then squeeze and drag at the same time making a thick bead of glue in the V. The glue then forms into a radius in the bottom of the V all by itself. But don't use eccelerator to quicken the drying, let it dry by itself.

[Daryl J.]

Thanks to all for the information; it should be a reasonable project.


Daryl J.

[Tojo633]

Hi
Only a small suggestion but why not use the shape of the Hurricane undercarriage leg/door as a pattern for the spat. Then at least the shape and design could be said to be of a hawker design, sort of.
Another passing thought having looked at the White Ryan STA, why not invert the undercarriage legs instead so they taper down to the spat.

Mmm Oshkosh pics, hope to be there next year was over in 2005, like the 2 Ryan pics.
Cheers
Sandy

[wagnersm]

Take a look at some of the Camm designed Hawker biplane aircraft.  

Some looked like they had a bit of fairing where the undercarrage struts met the airframe, but others, the Hawker Hart for example, appear to have streamlined the struts, but left the connection between the strut and airframe unfaired.

Steve

[gooberliberation]

Didn't mention the S word in the original post. Worried about a certain spatman chiming in?  

[Daryl J.]

Goobs, nope...not worried a bit.   ^_^  It just is involved enough that it best be done outside the GB's time frame.   I'd really like for it to turn out well and I'll be building spats 'til the cows come home.    

Daryl J.

[Brian da Basher]

<snip>

I'll be building spats 'til the cows come home.    

Daryl J.

Good on ya, Daryl!

I've been enjoying lurking on this thread. While I love spats, I'd be the last person to give an educated reply on aerodynamics.

Brian da Basher