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AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Fri Dec 15, 2006 8:10 pm Post subject: Smokin Rivets

Now that builders have painted the landscape with why and why not to drill, then deburr, then dimple vs. deburr, dimple then drill or just skip it all together and just pop rivet.  Let’s move the discussion to the next level.  I don’t know if any RV-10s that have enough time on them yet but no one has addressed the cause for them, where they are likely to occur (so you can be watching), what corrective action can be taken or more importantly which of the two or three techniques being used is less likely to contribute to them.  We are all prideful of our selected technique but a lot of builders might find the discussion enlightening. – not to be confused with Lightning and the need for static suppression wicks.  

Deems, you referenced Dan Checkoway’s advise (the self promoted high guru on Sheetmetal).  What say Dan?  

Let’s hear discussion about tensile vs. shear, wet rivets, use of reams vs. drill bits, fitment of the rivet to the opening and proper prep, or rivets in composite.  VAN’s says “forgetaboutit” cause the RV-12 is going to skip steps in the effort to find a faster build and lazy group of builders.  How about the advantages and applications of Icebox rivets, Monel or the common 1100 rivets?  

Come on Kelly – let’s play.  During last night’s Pacific NW storm we were hit by a rash of lightning strikes and smoking rivets all over the NW (scores of aircraft).  

Anyone remember Honest Abe’s math on Four Score?  We are building the finest High Speed, IFR cruisers at low cost out there right?  

  

John Cox  

#40600  

    [quote][b]

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VHMUM(at)bigpond.com
Guest

Posted: Fri Dec 15, 2006 9:48 pm Post subject: Smokin Rivets

maaate WHO CARES JUST BUILD!!!!

 [quote]   ---

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noel(at)blueskyaviation.n
Guest

Posted: Sat Dec 16, 2006 11:36 am Post subject: Smokin Rivets

The anatomy of the smokin’ rivet.  

   

What is smoke?  The black residue that streams down wind of a rivet is Aluminum oxide, the second hardest substance on earth with the first being diamonds.  Aluminum oxide is a by product of corrosion that naturally occurs.  Aluminums is considered to be self lubricating, meaning it will continue to sluff, and the aluminum oxide being harder than the base metal will exponentially carve more aluminum oxide out of the base metal,  

   

  A rivet that has been properly set will eventually smoke given a structure subjected to vibration that has been under engineered, meaning not enough rivets per inch.  I have seen, and repaired these structures (again and again), mostly engine nacelles on jets, fortunately or unfortunately how every you want to look at the subject, Van’s aircraft does not have any under engineered structures that would qualify for the under engineered place to look for smoking rivets.  Yes all rivet joints move to one degree or another so a rivet can be set in such a way that it will smoke.  In conclusion smoking rivets on RV is a builder flaw.      

   

How to set rivets that will smoke.    

   

First let us look at the parts that Van’s sends us.  The Punching process is extremely actuate, Fin Power CNC punch press have a tolerance of .004 in 8 linear feet.  Van’s has CAD people that really know their system and can tell the punch press exactly where to put holes.  Given the .004 tolerance there are some places on the aircraft that have the same hole in 4 sheets of aluminum that each have this tolerance so you will see holes that are a little hard to put a reamer through, but is still very accurate.  

   

The punching action causes aluminum to “flow”.  That is the cause of the volcano on the exit side of the sheet.  This flow is not like the burr created from using a drill bit.  You must remove the volcano completely with out countersinking the base metal.    

   

Below is how to cause voids and entrap, well let’s call it ‘Stuff’ for lack of better words, which promote the corrosive environment to create copious amounts of SMOKE.  

     Use a drill bit      instead of a reamer.      Just for giggles take       a ¼” drill bit and begin drilling a hole in a piece of .032 sheet       metal.  You will see that the hole that begins to develop is triangular,       and as the drill bit finally passes the hole is not truly round.  This       is obviously a start of voids in the rivet joint.    
USE a Reamer they       turn triangular holes into properly sized round ones.  Reamers       should be used everywhere on the van’s pre-punched holes   
   

     Don’t deburr/ deburr      to deeply     The punching       process causes a volcano like structure on the punch exit.  Not only       will this cause a void but will chip the rim of the volcano into the       joint acting like grist in a roller mill.   
The head and or       shop head will sit up on the volcano and will not properly clamp the       rivet joint.   
Deburring to deeply       is a very, very common mistake RV builder’s make due to the       punching process.   
Look at some of the       heavier aluminum that has been punched with 1/8” holes.  You       will see one side that is pressed in and the other side will be coned out       like a volcano.  If you take a 100 degree countersink or some of the       other rotary deburring tools and cut this volcano off to the point that       there is no aluminum that protrudes above the base metal you will have a shallow       countersink.  This shallow countersink WILL NOT be completely filled       by the expansion of a rivet.  This is the stating point of corrosion   
We use sand paper to       deburr.  The sand paper will remove the volcano with out causing a       shallow countersink.  Two notes WE PRIME, WE don’t build       polished aircraft.  
   

     Dimpling /      countersinking the sub structure with the same dimple as the skin.       Easy test, take two       small pieces of scrap aluminum and drill #30 holes, Deburr.    
Dimple each with       your #30 dimple dies.   
Mate the two pieces       and you will see that they don’t fit very well.  This cause       lots of voids and is the primary thing that RV builders do to cause       smoke.   
Take those same two       pieces of aluminum and dimple them together using your #30 dimple dies.    
   

<![if !supportLists]>                                                              i.      <![endif]>Better fit isn’t it!  They don’t rock like a bobble head doll       Point here is that       most people don’t dimple the substructures (ribs) to “receive”       the overlaying dimple.   
We take a small ½”X       1/2” scrap and attach it to the male dimple die to dimple all the       sub structure.  This eliminates the rocking caused by having two       improperly formed dimples pinched together by a rivet.   
I have seen people dimpling       with the plastic sill in place, bad idea.   
I have seen people       afraid of over dimpling so they hit the dimplier once instead of twice       (real hard).  Dimpling is a forming process that must be complete; a       half dimple will cause the skin to warp, bad idea.   
   

   

Sorry if this is a little anal, I have spent many years trying to get the best looking rivets I can.  I have piles of scrap that I drill holes in and look at with a magnifying glass. Rivet and inspect, change the technique a little here and there then drill and rivet inspect until ,In my opinion we do some of the finest riveting on RV’s.  Every airplane we do get’s a little better and a little faster.     

   

   

Noel Simmons  

Blue Sky Aviation, Inc.  

www.blueskyaviation.net         

   

   

   

   

   

         

  

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John W. Cox

 Sent: Friday, December 15, 2006 9:09 PM

 To: rv10-list(at)matronics.com

 Subject: Smokin Rivets  

  

   

Now that builders have painted the landscape with why and why not to drill, then deburr, then dimple vs. deburr, dimple then drill or just skip it all together and just pop rivet.  Let’s move the discussion to the next level.  I don’t know if any RV-10s that have enough time on them yet but no one has addressed the cause for them, where they are likely to occur (so you can be watching), what corrective action can be taken or more importantly which of the two or three techniques being used is less likely to contribute to them.  We are all prideful of our selected technique but a lot of builders might find the discussion enlightening. – not to be confused with Lightning and the need for static suppression wicks.  

Deems, you referenced Dan Checkoway’s advise (the self promoted high guru on Sheetmetal).  What say Dan?  

Let’s hear discussion about tensile vs. shear, wet rivets, use of reams vs. drill bits, fitment of the rivet to the opening and proper prep, or rivets in composite.  VAN’s says “forgetaboutit” cause the RV-12 is going to skip steps in the effort to find a faster build and lazy group of builders.  How about the advantages and applications of Icebox rivets, Monel or the common 1100 rivets?  

Come on Kelly – let’s play.  During last night’s Pacific NW storm we were hit by a rash of lightning strikes and smoking rivets all over the NW (scores of aircraft).  

Anyone remember Honest Abe’s math on Four Score?  We are building the finest High Speed, IFR cruisers at low cost out there right?  

John Cox  

#40600   	  Quote: 	
		    www.aeroelectric.com 	
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       [quote][b]

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AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Sat Dec 16, 2006 9:55 pm Post subject: Smokin Rivets

Noel –   

   

Noelle to you too.  You were the first to help pull the list off of the VNE dive on the subject of Garmin vs. Garmin.  Much like the movie Kramer v. Kramer.  I will let the reader figure out which was Dustin and which was Meryl. Remember no one won in the end and the kid took the beating.  

   

You hit on why reamers are of value.  Why the tightest fit of hole to rivet dimension is important.  Why it is a matter of perspective a blind builder vs. one with a magnifying glass can see imperfections which will result in sloppier work.  Sloppier work might just mean corrective action after final assembly.  The topic of attachment technique of four dynamically moving elements being correctly aligned and fastened prior to rivet set is another subject.  

   

My guess is most readers like the conflict rather than the detail of build.  

   

Now back to the fur fly contest.    

     

John Cox   

Do not Archive as content is too G in an R market

 

   

        

  

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Noel & Yoshie Simmons

 Sent: Saturday, December 16, 2006 11:35 AM

 To: rv10-list(at)matronics.com

 Subject: RE: Smokin Rivets  

  

   

The anatomy of the smokin’ rivet.  

   

What is smoke?  The black residue that streams down wind of a rivet is Aluminum oxide, the second hardest substance on earth with the first being diamonds.  Aluminum oxide is a by product of corrosion that naturally occurs.  Aluminums is considered to be self lubricating, meaning it will continue to sluff, and the aluminum oxide being harder than the base metal will exponentially carve more aluminum oxide out of the base metal,  

   

  A rivet that has been properly set will eventually smoke given a structure subjected to vibration that has been under engineered, meaning not enough rivets per inch.  I have seen, and repaired these structures (again and again), mostly engine nacelles on jets, fortunately or unfortunately how every you want to look at the subject, Van’s aircraft does not have any under engineered structures that would qualify for the under engineered place to look for smoking rivets.  Yes all rivet joints move to one degree or another so a rivet can be set in such a way that it will smoke.  In conclusion smoking rivets on RV is a builder flaw.      

   

How to set rivets that will smoke.    

   

First let us look at the parts that Van’s sends us.  The Punching process is extremely actuate, Fin Power CNC punch press have a tolerance of .004 in 8 linear feet.  Van’s has CAD people that really know their system and can tell the punch press exactly where to put holes.  Given the .004 tolerance there are some places on the aircraft that have the same hole in 4 sheets of aluminum that each have this tolerance so you will see holes that are a little hard to put a reamer through, but is still very accurate.  

   

The punching action causes aluminum to “flow”.  That is the cause of the volcano on the exit side of the sheet.  This flow is not like the burr created from using a drill bit.  You must remove the volcano completely with out countersinking the base metal.    

   

Below is how to cause voids and entrap, well let’s call it ‘Stuff’ for lack of better words, which promote the corrosive environment to create copious amounts of SMOKE.  

   

1.      Use a drill bit instead of a reamer.   

a.       Just for giggles take a ¼” drill bit and begin drilling a hole in a piece of .032 sheet metal.  You will see that the hole that begins to develop is triangular, and as the drill bit finally passes the hole is not truly round.  This is obviously a start of voids in the rivet joint.   

b.      USE a Reamer they turn triangular holes into properly sized round ones.  Reamers should be used everywhere on the van’s pre-punched holes   

   

2.      Don’t deburr/ deburr to deeply  

a.       The punching process causes a volcano like structure on the punch exit.  Not only will this cause a void but will chip the rim of the volcano into the joint acting like grist in a roller mill.  

b.      The head and or shop head will sit up on the volcano and will not properly clamp the rivet joint.  

c.       Deburring to deeply is a very, very common mistake RV builder’s make due to the punching process.  

d.      Look at some of the heavier aluminum that has been punched with 1/8” holes.  You will see one side that is pressed in and the other side will be coned out like a volcano.  If you take a 100 degree countersink or some of the other rotary deburring tools and cut this volcano off to the point that there is no aluminum that protrudes above the base metal you will have a shallow countersink.  This shallow countersink WILL NOT be completely filled by the expansion of a rivet.  This is the stating point of corrosion  

e.       We use sand paper to deburr.  The sand paper will remove the volcano with out causing a shallow countersink.  Two notes WE PRIME, WE don’t build polished aircraft.  

   

3.      Dimpling / countersinking the sub structure with the same dimple as the skin.    

a.       Easy test, take two small pieces of scrap aluminum and drill #30 holes, Deburr.   

b.      Dimple each with your #30 dimple dies.  

c.       Mate the two pieces and you will see that they don’t fit very well.  This cause lots of voids and is the primary thing that RV builders do to cause smoke.  

d.      Take those same two pieces of aluminum and dimple them together using your #30 dimple dies.    

                                                                                       i.      Better fit isn’t it!  They don’t rock like a bobble head doll  

e.       Point here is that most people don’t dimple the substructures (ribs) to “receive” the overlaying dimple.  

f.        We take a small ½”X 1/2” scrap and attach it to the male dimple die to dimple all the sub structure.  This eliminates the rocking caused by having two improperly formed dimples pinched together by a rivet.  

g.       I have seen people dimpling with the plastic sill in place, bad idea.  

h.       I have seen people afraid of over dimpling so they hit the dimplier once instead of twice (real hard).  Dimpling is a forming process that must be complete; a half dimple will cause the skin to warp, bad idea.   

   

Sorry if this is a little anal, I have spent many years trying to get the best looking rivets I can.  I have piles of scrap that I drill holes in and look at with a magnifying glass. Rivet and inspect, change the technique a little here and there then drill and rivet inspect until ,In my opinion we do some of the finest riveting on RV’s.  Every airplane we do get’s a little better and a little faster.     

   

   

Noel Simmons  

Blue Sky Aviation, Inc.  

www.blueskyaviation.net         

      [quote][b]

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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jjessen

Joined: 22 Apr 2006
Posts: 285
Location: OR

Posted: Tue Dec 19, 2006 10:22 am Post subject: Smokin Rivets

Noel, thanks for the informative post.  Can you  enlighten me about point number 3f, below?  I'm not getting the mental  image of what you're saying.  

  

 Thanks, 

  

 John Jessen

  

 do not archive

  	  Quote: 	
		                 

   

From:    owner-rv10-list-server(at)matronics.com    [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Noel & Yoshie    Simmons

Sent: Saturday,    December 16, 2006 11:35 AM

To: rv10-list(at)matronics.com

Subject: RE: Smokin    Rivets

   

    

The anatomy of the smokin’    rivet.   

    

What is smoke?  The black residue    that streams down wind of a rivet is Aluminum oxide, the second hardest    substance on earth with the first being diamonds.  Aluminum oxide is a by    product of corrosion that naturally occurs.  Aluminums is considered to    be self lubricating, meaning it will continue to sluff, and the aluminum oxide    being harder than the base metal will exponentially carve more aluminum oxide    out of the base metal,   

    

  A rivet that has been properly set    will eventually smoke given a structure subjected to vibration that has been    under engineered, meaning not enough rivets per inch.  I have seen, and    repaired these structures (again and again), mostly engine nacelles on jets,    fortunately or unfortunately how every you want to look at the subject, Van’s    aircraft does not have any under engineered structures that would qualify for    the under engineered place to look for smoking rivets.  Yes all rivet    joints move to one degree or another so a rivet can be set in such a way that    it will smoke.  In conclusion smoking rivets on RV is a builder    flaw.       

    

How to set rivets that will smoke.        

    

First let us look at the parts that Van’s    sends us.  The Punching process is extremely actuate, Fin Power CNC punch    press have a tolerance of .004 in 8 linear feet.  Van’s has CAD people    that really know their system and can tell the punch press exactly where to    put holes.  Given the .004 tolerance there are some places on the    aircraft that have the same hole in 4 sheets of aluminum that each have this    tolerance so you will see holes that are a little hard to put a reamer    through, but is still very accurate.   

    

The punching action causes aluminum to    “flow”.  That is the cause of the volcano on the exit side of the sheet.     This flow is not like the burr created from using a drill bit.  You    must remove the volcano completely with out countersinking the base    metal.     

    

Below is how to    cause voids and entrap, well let’s call it ‘Stuff’ for lack of better words,    which promote the corrosive environment to create copious amounts of    SMOKE.   

    

1.         Use a drill bit instead of a reamer.    

a.          Just for giggles take a ¼” drill bit and begin    drilling a hole in a piece of .032 sheet metal.  You will see that the    hole that begins to develop is triangular, and as the drill bit finally passes    the hole is not truly round.  This is obviously a start of voids in the    rivet joint.    

b.         USE a Reamer they turn triangular holes into    properly sized round ones.  Reamers should be used everywhere on the    van’s pre-punched holes    

    

2.         Don’t deburr/ deburr to deeply   

a.          The punching process causes a volcano like    structure on the punch exit.  Not only will this cause a void but will    chip the rim of the volcano into the joint acting like grist in a roller    mill.   

b.         The head and or shop head will sit up on the    volcano and will not properly clamp the rivet joint.   

c.          Deburring to deeply is a very, very common mistake    RV builder’s make due to the punching process.   

d.         Look at some of the heavier aluminum that has been    punched with 1/8” holes.  You will see one side that is pressed in and    the other side will be coned out like a volcano.  If you take a 100    degree countersink or some of the other rotary deburring tools and cut this    volcano off to the point that there is no aluminum that protrudes above the    base metal you will have a shallow countersink.  This shallow countersink    WILL NOT be completely filled by the expansion of a rivet.  This is the    stating point of corrosion   

e.          We use sand paper to deburr.  The sand paper    will remove the volcano with out causing a shallow countersink.  Two    notes WE PRIME, WE don’t build polished aircraft.   

    

3.         Dimpling / countersinking the sub structure with    the same dimple as the skin.     

a.          Easy test, take two small pieces of scrap aluminum    and drill #30 holes, Deburr.    

b.         Dimple each with your #30 dimple dies.   

c.          Mate the two pieces and you will see that they    don’t fit very well.  This cause lots of voids and is the primary thing    that RV builders do to cause smoke.   

d.         Take those same two pieces of aluminum and dimple    them together using your #30 dimple dies.     

                                                                                          i.         Better fit isn’t it!  They don’t rock like a    bobble head doll   

e.          Point here is that most people don’t dimple the    substructures (ribs) to “receive” the overlaying dimple.   

f.           We take a small ½”X 1/2” scrap and attach it to    the male dimple die to dimple all the sub structure.  This eliminates the    rocking caused by having two improperly formed dimples pinched together by a    rivet.   

g.          I have seen people dimpling with the plastic sill    in place, bad idea.   

h.          I have seen people afraid of over dimpling so they    hit the dimplier once instead of twice (real hard).  Dimpling is a    forming process that must be complete; a half dimple will cause the skin to    warp, bad idea.    

    

Sorry if this is a little anal, I have    spent many years trying to get the best looking rivets I can.  I have    piles of scrap that I drill holes in and look at with a magnifying glass.    Rivet and inspect, change the technique a little here and there then drill and    rivet inspect until ,In my opinion we do some of the finest riveting on    RV’s.  Every airplane we do get’s a little better and a little    faster.      

    

    

Noel Simmons   

Blue Sky Aviation, Inc.   

www.blueskyaviation.net          

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noel(at)blueskyaviation.n
Guest

Posted: Tue Dec 19, 2006 4:07 pm Post subject: Smokin Rivets

One more picture of the shim itself  

   

         

  

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John Jessen

 Sent: Tuesday, December 19, 2006 11:21 AM

 To: rv10-list(at)matronics.com

 Subject: RE: Smokin Rivets  

  

   

Noel, thanks for the informative post.  Can you enlighten me about point number 3f, below?  I'm not getting the mental image of what you're saying.    

   

Thanks,   

   

John Jessen  

   

do not archive   	  Quote: 	
		            

  

  

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Noel & Yoshie Simmons

 Sent: Saturday, December 16, 2006 11:35 AM

 To: rv10-list(at)matronics.com

 Subject: RE: Smokin Rivets  

  

   

The anatomy of the smokin’ rivet.  

   

What is smoke?  The black residue that streams down wind of a rivet is Aluminum oxide, the second hardest substance on earth with the first being diamonds.  Aluminum oxide is a by product of corrosion that naturally occurs.  Aluminums is considered to be self lubricating, meaning it will continue to sluff, and the aluminum oxide being harder than the base metal will exponentially carve more aluminum oxide out of the base metal,  

   

  A rivet that has been properly set will eventually smoke given a structure subjected to vibration that has been under engineered, meaning not enough rivets per inch.  I have seen, and repaired these structures (again and again), mostly engine nacelles on jets, fortunately or unfortunately how every you want to look at the subject, Van’s aircraft does not have any under engineered structures that would qualify for the under engineered place to look for smoking rivets.  Yes all rivet joints move to one degree or another so a rivet can be set in such a way that it will smoke.  In conclusion smoking rivets on RV is a builder flaw.      

   

How to set rivets that will smoke.    

   

First let us look at the parts that Van’s sends us.  The Punching process is extremely actuate, Fin Power CNC punch press have a tolerance of .004 in 8 linear feet.  Van’s has CAD people that really know their system and can tell the punch press exactly where to put holes.  Given the .004 tolerance there are some places on the aircraft that have the same hole in 4 sheets of aluminum that each have this tolerance so you will see holes that are a little hard to put a reamer through, but is still very accurate.  

   

The punching action causes aluminum to “flow”.  That is the cause of the volcano on the exit side of the sheet.  This flow is not like the burr created from using a drill bit.  You must remove the volcano completely with out countersinking the base metal.    

   

Below is how to cause voids and entrap, well let’s call it ‘Stuff’ for lack of better words, which promote the corrosive environment to create copious amounts of SMOKE.  

   

1.      Use a drill bit instead of a reamer.   

a.       Just for giggles take a ¼” drill bit and begin drilling a hole in a piece of .032 sheet metal.  You will see that the hole that begins to develop is triangular, and as the drill bit finally passes the hole is not truly round.  This is obviously a start of voids in the rivet joint.   

b.      USE a Reamer they turn triangular holes into properly sized round ones.  Reamers should be used everywhere on the van’s pre-punched holes   

   

2.      Don’t deburr/ deburr to deeply  

a.       The punching process causes a volcano like structure on the punch exit.  Not only will this cause a void but will chip the rim of the volcano into the joint acting like grist in a roller mill.  

b.      The head and or shop head will sit up on the volcano and will not properly clamp the rivet joint.  

c.       Deburring to deeply is a very, very common mistake RV builder’s make due to the punching process.  

d.      Look at some of the heavier aluminum that has been punched with 1/8” holes.  You will see one side that is pressed in and the other side will be coned out like a volcano.  If you take a 100 degree countersink or some of the other rotary deburring tools and cut this volcano off to the point that there is no aluminum that protrudes above the base metal you will have a shallow countersink.  This shallow countersink WILL NOT be completely filled by the expansion of a rivet.  This is the stating point of corrosion  

e.       We use sand paper to deburr.  The sand paper will remove the volcano with out causing a shallow countersink.  Two notes WE PRIME, WE don’t build polished aircraft.  

   

3.      Dimpling / countersinking the sub structure with the same dimple as the skin.    

a.       Easy test, take two small pieces of scrap aluminum and drill #30 holes, Deburr.   

b.      Dimple each with your #30 dimple dies.  

c.       Mate the two pieces and you will see that they don’t fit very well.  This cause lots of voids and is the primary thing that RV builders do to cause smoke.  

d.      Take those same two pieces of aluminum and dimple them together using your #30 dimple dies.    

                                                                                       i.      Better fit isn’t it!  They don’t rock like a bobble head doll  

e.       Point here is that most people don’t dimple the substructures (ribs) to “receive” the overlaying dimple.  

f.        We take a small ½”X 1/2” scrap and attach it to the male dimple die to dimple all the sub structure.  This eliminates the rocking caused by having two improperly formed dimples pinched together by a rivet.  

g.       I have seen people dimpling with the plastic sill in place, bad idea.  

h.       I have seen people afraid of over dimpling so they hit the dimplier once instead of twice (real hard).  Dimpling is a forming process that must be complete; a half dimple will cause the skin to warp, bad idea.   

   

Sorry if this is a little anal, I have spent many years trying to get the best looking rivets I can.  I have piles of scrap that I drill holes in and look at with a magnifying glass. Rivet and inspect, change the technique a little here and there then drill and rivet inspect until ,In my opinion we do some of the finest riveting on RV’s.  Every airplane we do get’s a little better and a little faster.     

   

   

Noel Simmons  

Blue Sky Aviation, Inc.  

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