Rebel #637 Mods - leading edge
Posted: Sat Feb 18, 2012 9:58 am
Hi Steve !
I certainly hope not, or I wouldn't have been able to fly all my
Rebels all these years !!! ;-) :-)
Seriously, according to several Globe Swift modifiers, who produce
some beautiful restoration/modification aircraft, flush rivetting makes
"No significant difference unless you are flying above 300 mph. !" - an
exact quote ! In as much as some of these guys had spent over $300K
on rebuilding their Swifts, I have to believe their experiences !!
Certainly, there are some airfoils that NEED a bit of surface roughness
to maintain flow adhesion - I once owned a glider that, if you polished the
top surface of the wings, it would increase the stall speed, and decrease
the handling & gliding performance !!! I didn't believe the other builders -
until I polished mine .... once !
This effect has been noted on the Rebel/Moose airfoil - at least some
examples actually cruised slower with a countersunk & filled leading edge !!
A turbulent airflow, from VG's, will actually adhere tighter to the
wing than a smooth airflow, in many cases. There is always a boundary
layer - With some aircraft with laminar flow airfoils - some Cherokees,
the Yankee, and others, if you raise the nose too early on the takeoff
roll, the laminar flow will separate from the back of the wing, and you can
roll for MILES without climbing !!! (It is effectively stalled !)
.........bobp
-------------------------------orig.-------------------------
On Sunday 09 January 2005 01:15 pm, steve whitenect wrote:
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I certainly hope not, or I wouldn't have been able to fly all my
Rebels all these years !!! ;-) :-)
Seriously, according to several Globe Swift modifiers, who produce
some beautiful restoration/modification aircraft, flush rivetting makes
"No significant difference unless you are flying above 300 mph. !" - an
exact quote ! In as much as some of these guys had spent over $300K
on rebuilding their Swifts, I have to believe their experiences !!
Certainly, there are some airfoils that NEED a bit of surface roughness
to maintain flow adhesion - I once owned a glider that, if you polished the
top surface of the wings, it would increase the stall speed, and decrease
the handling & gliding performance !!! I didn't believe the other builders -
until I polished mine .... once !
This effect has been noted on the Rebel/Moose airfoil - at least some
examples actually cruised slower with a countersunk & filled leading edge !!
A turbulent airflow, from VG's, will actually adhere tighter to the
wing than a smooth airflow, in many cases. There is always a boundary
layer - With some aircraft with laminar flow airfoils - some Cherokees,
the Yankee, and others, if you raise the nose too early on the takeoff
roll, the laminar flow will separate from the back of the wing, and you can
roll for MILES without climbing !!! (It is effectively stalled !)
.........bobp
-------------------------------orig.-------------------------
On Sunday 09 January 2005 01:15 pm, steve whitenect wrote:
Hi Bob
Correct me if I'm wrong but I thought a clean leading edge from the top of
the large spar around to a foot or so under the front of the wing was
desireable for undestirbed air flow. If trying to create an air flow tight
to the wing with generators ahead of the large spar, haven't you already
stalled!?
Steve
From: Bob Patterson <beep@sympatico.ca>
Reply-To: <rebel-builders@dcsol.com>
To: <rebel-builders@dcsol.com>
Subject: Re: Rebel #637 Mods
Date: Sat, 8 Jan 2005 13:34:35 -0500
Hi Steve !
For anyone who doesn't want to do all this work, you <could> just order
a set of Elite leading edge skins (they are .032, and pre-formed &
punched, ready to install). Apparently, the only reason for making
them .032 was so they couldn't be as easily dented while refuelling !!!
Never had that problem with a Rebel, but .....
As for the countersinking - to each his own, but I've always contended
that the raised rivet heads are built-in vortex generators... ;-^)
:-)
(The turbulator tape applied to glider wings (& propellor leading edges)
has
bumps that are less than 1/8" high, and that seems to work for some !)
............bobp
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