The Murphy Builders Site

Posted: **Fri Feb 17, 2012 5:26 pm**

RJ I believe the reason for not flush rivetting all the way back is
because there is a boundry layer of still air all around a moving wing
which grows thicker towards the rear of the wing. The rivet heads at the
back are completly in the boundry layer so there is no advantage to flush
rivetting
Drew

At 01:36 PM 1/4/01 -0600, you wrote:

Folks,

MAM offers flush rivets as an option for the leading edges of the
stabilizers and wing. Brian at MAM suggests that the flush rivets be used
on the horizontal stabilizer only as far back as the leading edge spar. Is
it a good idea to extend the use of flush rivets all the way back to the
rear spar for drag reduction? Any good reasons not to do so ( other than
the extra work) ?

I would appreciate anyone's input.

Cheers, rj

R J Thomas
Lafayette, LA
rj.thomas@halliburton.com

Super Rebel #140

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Posted: **Fri Feb 17, 2012 8:39 pm**

Folks,

MAM offers flush rivets as an option for the leading edges of the
stabilizers and wing. Brian at MAM suggests that the flush rivets be used
on the horizontal stabilizer only as far back as the leading edge spar. Is
it a good idea to extend the use of flush rivets all the way back to the
rear spar for drag reduction? Any good reasons not to do so ( other than
the extra work) ?

I would appreciate anyone's input.

Cheers, rj

R J Thomas
Lafayette, LA
rj.thomas@halliburton.com

Super Rebel #140

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Posted: **Fri Feb 17, 2012 8:39 pm**

Hi RJ !

If you haven't already started the flush rivets - wouldn't
bother !! If you talk to the Globe Swift restorers, who've tried
flush rivetting the whole airplane, they say that it really makes
NO difference until you get over 300 mph !! They are offered
purely as a cosmetic improvement, for those who want them. If the
factory do not recommend more of them, there is likely a good reason.
Possibly something structural, OR perhaps tuft-testing showed that
the rivet heads helped maintain correct airflow - and therefore,
proper functioning of the elevator ! (Definitely "A GOOD THING"(tm) :-) )

<My> pet contention is that the rivets are built-in vortex
generators, improving performance and saving money !! (Tongue firmly
in cheek ! ;-`) ) Seriously, though, EVERY Murphy aircraft
that I've flown with flush rivets OR vortex generators was 3 to 5 MPH ++
SLOWER than those with regular rivets, even with a bit more power.
There may have been other contributing factors, but that's <my>
observation ....

The flush rivets ARE a lot of work, and, unless the dimpling
and drilling is done properly, MAY result in a weaker structure. Done
properly, it IS slightly stronger.

 would save the effort and get flying sooner - you'll LOVE
your Super Rebel !!! :-)

(ALL of the above is just MHO, please don't shoot me !! )

.....bobp

Just a thought - you'd probably have much more of a performance gain
from cleaning up fairings and streamlining the main gear leading AND
trailing edges !!

There IS some information in the archives on one Rebel builder
who gained over 15 mph cruise from detail cleanups, and he might
volunteer more information soon ....

-----------------------------orig.-------------------------------------------
At 01:36 PM 1/4/01 -0600, you wrote:

Folks,

MAM offers flush rivets as an option for the leading edges of the
stabilizers and wing. Brian at MAM suggests that the flush rivets be used
on the horizontal stabilizer only as far back as the leading edge spar. Is
it a good idea to extend the use of flush rivets all the way back to the
rear spar for drag reduction? Any good reasons not to do so ( other than
the extra work) ?

I would appreciate anyone's input.

Cheers, rj

R J Thomas
Lafayette, LA
rj.thomas@halliburton.com

Super Rebel #140

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Posted: **Fri Feb 17, 2012 8:39 pm**

Bob,

Thanks for the clear and concise insight. Over the past few months of
perusing Mike's archives, I have come to regard your "humble opinion" with a
great deal of respect.

Cheers, rj

============================================================================
===

-----Original Message-----
From: Bob Patterson [mailto:bob.patterson@canrem.com]
Sent: Thursday, January 04,2001 10:04 PM
To: murphy-rebel@dcsol.com
Subject: Re: Flush rivets

Hi RJ !

If you haven't already started the flush rivets - wouldn't
bother !! If you talk to the Globe Swift restorers, who've tried
flush rivetting the whole airplane, they say that it really makes
NO difference until you get over 300 mph !! They are offered
purely as a cosmetic improvement, for those who want them. If the
factory do not recommend more of them, there is likely a good reason.
Possibly something structural, OR perhaps tuft-testing showed that
the rivet heads helped maintain correct airflow - and therefore,
proper functioning of the elevator ! (Definitely "A GOOD THING"(tm) :-) )

<My> pet contention is that the rivets are built-in vortex
generators, improving performance and saving money !! (Tongue firmly
in cheek ! ;-`) ) Seriously, though, EVERY Murphy aircraft
that I've flown with flush rivets OR vortex generators was 3 to 5 MPH ++
SLOWER than those with regular rivets, even with a bit more power.
There may have been other contributing factors, but that's <my>
observation ....

The flush rivets ARE a lot of work, and, unless the dimpling
and drilling is done properly, MAY result in a weaker structure. Done
properly, it IS slightly stronger.

 would save the effort and get flying sooner - you'll LOVE
your Super Rebel !!! :-)

(ALL of the above is just MHO, please don't shoot me !! )

.....bobp

Just a thought - you'd probably have much more of a performance gain
from cleaning up fairings and streamlining the main gear leading AND
trailing edges !!

There IS some information in the archives on one Rebel builder
who gained over 15 mph cruise from detail cleanups, and he might
volunteer more information soon ....

-----------------------------orig.------------------------------------------
-
At 01:36 PM 1/4/01 -0600, you wrote:

Folks,

MAM offers flush rivets as an option for the leading edges of the
stabilizers and wing. Brian at MAM suggests that the flush rivets be used
on the horizontal stabilizer only as far back as the leading edge spar.

Is

it a good idea to extend the use of flush rivets all the way back to the
rear spar for drag reduction? Any good reasons not to do so ( other than
the extra work) ?

I would appreciate anyone's input.

Cheers, rj

R J Thomas
Lafayette, LA
rj.thomas@halliburton.com

Super Rebel #140

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Posted: **Fri Feb 17, 2012 8:39 pm**

RJ,

Blush ! Blush ! Hope I didn't discourage you TOO much !

The aircraft I mentioned had flush rivetted leading edges on
the WINGS - I don't imagine it makes too much difference to the tail,
either...

Keep on building - THE JOY OF FLYING <IS> WORTH IT !!! :-)

....bobp

---------------------------------orig.-------------------------------------
At 07:59 AM 1/5/01 -0600, you wrote:

Bob,

Thanks for the clear and concise insight. Over the past few months of
perusing Mike's archives, I have come to regard your "humble opinion" with a
great deal of respect.

Cheers, rj

============================================================================
===

-----Original Message-----
From: Bob Patterson [mailto:bob.patterson@canrem.com]
Sent: Thursday, January 04,2001 10:04 PM
To: murphy-rebel@dcsol.com
Subject: Re: Flush rivets

Hi RJ !

If you haven't already started the flush rivets - wouldn't
bother !! If you talk to the Globe Swift restorers, who've tried
flush rivetting the whole airplane, they say that it really makes
NO difference until you get over 300 mph !! They are offered
purely as a cosmetic improvement, for those who want them. If the
factory do not recommend more of them, there is likely a good reason.
Possibly something structural, OR perhaps tuft-testing showed that
the rivet heads helped maintain correct airflow - and therefore,
proper functioning of the elevator ! (Definitely "A GOOD THING"(tm) :-) )

<My> pet contention is that the rivets are built-in vortex
generators, improving performance and saving money !! (Tongue firmly
in cheek ! ;-`) ) Seriously, though, EVERY Murphy aircraft
that I've flown with flush rivets OR vortex generators was 3 to 5 MPH ++
SLOWER than those with regular rivets, even with a bit more power.
There may have been other contributing factors, but that's <my>
observation ....

The flush rivets ARE a lot of work, and, unless the dimpling
and drilling is done properly, MAY result in a weaker structure. Done
properly, it IS slightly stronger.

 would save the effort and get flying sooner - you'll LOVE
your Super Rebel !!! :-)

(ALL of the above is just MHO, please don't shoot me !! )

.....bobp

Just a thought - you'd probably have much more of a performance gain
from cleaning up fairings and streamlining the main gear leading AND
trailing edges !!

There IS some information in the archives on one Rebel builder
who gained over 15 mph cruise from detail cleanups, and he might
volunteer more information soon ....

-----------------------------orig.------------------------------------------
-
At 01:36 PM 1/4/01 -0600, you wrote:
Folks,

MAM offers flush rivets as an option for the leading edges of the
stabilizers and wing. Brian at MAM suggests that the flush rivets be used
on the horizontal stabilizer only as far back as the leading edge spar.
Is
it a good idea to extend the use of flush rivets all the way back to the
rear spar for drag reduction? Any good reasons not to do so ( other than
the extra work) ?

I would appreciate anyone's input.

Cheers, rj

R J Thomas
Lafayette, LA
rj.thomas@halliburton.com

Super Rebel #140

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Posted: **Fri Feb 17, 2012 8:39 pm**

Ditto Bob! I think we all appreciate YHO. Keep it up.

Bruce G 357 R

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Posted: **Fri Feb 17, 2012 8:39 pm**

Warren

If you've got any pictures of your wing I'd like too see them.
The thoughts of a clean wing on a Rebel sounds good.

Rick Ford
436R

----- Original Message -----
From: Warren T. Montgomery <monty@emirates.net.ae>
To: Murphy Rebel Builders List <murphy-rebel@dcsol.com>
Sent: Saturday, January 06, 2001 8:22 AM
Subject: Re: Flush rivets

RJ,
I've flush riveted the entire wing (less fuel cell), flaps, ailerons,
cabin, tail cone, fin.
I used mushroom rivets only on the stab and elev as I hadn't planned on
flush at the time. I hate looking at all those bumps and I'm tempted to
pull the stab and elev skins off and dimple those as well.

Yes looking back it's a lot of work, but like anything else not so bad
if done one piece at a time. How many extra hours I don't know. I've
kept a running total but would have to try and break it down (or am
afraid to add up). It actually goes quite fast when you've got it all
worked out.
It does take planning due to the different thickness of skin. some need
to have the under skin countersunk or pre-dimpled. I've also made
different sized female cups for the various skin combination thickness'.
Also cups with a side ground flat for tight radiuses such as flanges.
(learned that the hard way after cutting clean through a tight radius).
And it does take an extra person for the most part as I've dimpled all
parts clecoed in place for an exact form. You'll need a proper
micro-stop re-ground to 110 degrees if doing any CS, however up to .040
may be dimpled, any less shouldn't be CS.

In order to get the male to mate to the pneu riveter, wrap the 1/8" ID
sized riveter head with tape until the same OD dia as the dimpler. Cut
excess flush. Place dimpler on head and further wrap both with tape and
again trim excess flush. I find that it stays on nicely and pulls off
easily as well when head is needed to pull 3/16" rivets. Buy lots of
penny nails and don't use concrete nails, they last forever but at the
price of the riveter jaws.

Yes BobP is correct in that it takes a lot of time and I'm also
concerned about the change to boundary layer and what the stall
characteristics may be. But it sure looks clean and that's why I've done
it. If I built another one the only thing I'd consider doing differently
is countersinking the thicker skins such as MAM did on the leading edge
of there Mark II SR (at least it appears CS as opposed to dimpled) and
CSing the .040 tank skins and using solid CS rivets.

I don't regret it 12,000 dimples later!!! We'll see after I fly it.

RJ Wrote
Folks,
Is it a good idea to extend the use of flush rivets all the way back to
the
rear spar for drag reduction? Any good reasons not to do so ( other
than
the extra work) ?
rj

--
Warren T. Montgomery
<monty@emirates.net.ae>
Dubai, United Arab Emirates

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Posted: **Fri Feb 17, 2012 8:39 pm**

Drew

The whole wing etc. is always in the boundary area. The question is whether
or not the flow is attached at the particular point in question. In the
area where the flow is detached i.e. fully turbulent, then the rivet type is
of no concern.

Brian #328R

-----Original Message-----
From: Drew and Jan [mailto:drewjan@execulink.com]
Sent: Wednesday, January 08, 1997 5:01 PM
To: Murphy Rebel Builders List
Subject: Re: Flush rivets

RJ I believe the reason for not flush rivetting all the way back is
because there is a boundry layer of still air all around a moving wing
which grows thicker towards the rear of the wing. The rivet heads at the
back are completly in the boundry layer so there is no advantage to flush
rivetting
Drew

At 01:36 PM 1/4/01 -0600, you wrote:

Folks,

MAM offers flush rivets as an option for the leading edges of the
stabilizers and wing. Brian at MAM suggests that the flush rivets be used
on the horizontal stabilizer only as far back as the leading edge spar.

Is

it a good idea to extend the use of flush rivets all the way back to the
rear spar for drag reduction? Any good reasons not to do so ( other than
the extra work) ?

I would appreciate anyone's input.

Cheers, rj

R J Thomas
Lafayette, LA
rj.thomas@halliburton.com

Super Rebel #140

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Posted: **Fri Feb 17, 2012 8:39 pm**

RJ,
I've flush riveted the entire wing (less fuel cell), flaps, ailerons,
cabin, tail cone, fin.
I used mushroom rivets only on the stab and elev as I hadn't planned on
flush at the time. I hate looking at all those bumps and I'm tempted to
pull the stab and elev skins off and dimple those as well.

Yes looking back it's a lot of work, but like anything else not so bad
if done one piece at a time. How many extra hours I don't know. I've
kept a running total but would have to try and break it down (or am
afraid to add up). It actually goes quite fast when you've got it all
worked out.
It does take planning due to the different thickness of skin. some need
to have the under skin countersunk or pre-dimpled. I've also made
different sized female cups for the various skin combination thickness'.
Also cups with a side ground flat for tight radiuses such as flanges.
(learned that the hard way after cutting clean through a tight radius).
And it does take an extra person for the most part as I've dimpled all
parts clecoed in place for an exact form. You'll need a proper
micro-stop re-ground to 110 degrees if doing any CS, however up to .040
may be dimpled, any less shouldn't be CS.

In order to get the male to mate to the pneu riveter, wrap the 1/8" ID
sized riveter head with tape until the same OD dia as the dimpler. Cut
excess flush. Place dimpler on head and further wrap both with tape and
again trim excess flush. I find that it stays on nicely and pulls off
easily as well when head is needed to pull 3/16" rivets. Buy lots of
penny nails and don't use concrete nails, they last forever but at the
price of the riveter jaws.

Yes BobP is correct in that it takes a lot of time and I'm also
concerned about the change to boundary layer and what the stall
characteristics may be. But it sure looks clean and that's why I've done
it. If I built another one the only thing I'd consider doing differently
is countersinking the thicker skins such as MAM did on the leading edge
of there Mark II SR (at least it appears CS as opposed to dimpled) and
CSing the .040 tank skins and using solid CS rivets.

I don't regret it 12,000 dimples later!!! We'll see after I fly it.

RJ Wrote
Folks,
Is it a good idea to extend the use of flush rivets all the way back to
the
rear spar for drag reduction? Any good reasons not to do so ( other
than
the extra work) ?
rj

--
Warren T. Montgomery
<monty@emirates.net.ae>
Dubai, United Arab Emirates
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