In response to Tony Spicer's post
Here's a workaround (maybe):
By Tony Spicer 8/10/2014
http://tinypic.com/r/wjduzp/8
http://i58.tinypic.com/1zpmznr.jpg
http://i62.tinypic.com/s1osn9.jpg
Updrilling for flush blind rivets
Forum rules
A forum for Panther aircraft builders and Enthusiasts. Two simple rules: Play nice and use a real name
A forum for Panther aircraft builders and Enthusiasts. Two simple rules: Play nice and use a real name
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rlweseman
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rlweseman
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Re: Updrilling for flush blind rivets
Posted by Tony Spicer 8/10/2014
Yep, testing is a good thing. Back in Feb of 2013 I did a bunch.
Probably had 25-30 samples just like the ones in the photos.
http://tinypic.com/r/wjduzp/8
Modified a dimple die so it could be used in a #40 hole. Worked just fine. No evidence of tearing around the dimple when examined with 10x magnification.
Used quite a few flush -41 rivets in the first set of wings and they worked just fine. In the end, I just used a rivet length one size longer than called for by the stack height. And they all went in #30 holes with no issues.
Tony
Yep, testing is a good thing. Back in Feb of 2013 I did a bunch.
Probably had 25-30 samples just like the ones in the photos.
http://tinypic.com/r/wjduzp/8
Modified a dimple die so it could be used in a #40 hole. Worked just fine. No evidence of tearing around the dimple when examined with 10x magnification.
Used quite a few flush -41 rivets in the first set of wings and they worked just fine. In the end, I just used a rivet length one size longer than called for by the stack height. And they all went in #30 holes with no issues.
Tony
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rlweseman
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Re: Updrilling for flush blind rivets
Posted by Paul Salter 8/9/2014
Dan,
Well said about inventing your own way. Once you make a change, you are not only a builder, but also become the design engineer. Every change has consequences, some more than others. Once you push that snowball down the hill, it grows. You just don't want to be caught under an avalanche. That is what engineering is all about, figuring out all possible ramifications of a change all the way to the finish product. And let me tell you, as a professional aerospace engineer, no one ever gets everything correct the first time through. That is what prototypes, beta builders, and kit verification builds are all about.
You may have to high of expectations of exactness. Nothing in building is ever 100% exact, there are always tolerences. Typical sheet metal (bends, cuts, hole placement) in the Navy is about +-0.030", when machining it is typically +-.010". For matched holes, like on the Panther kit, the tolerance is even lower, probably in the +-.003 range. Even on a 60,000 lb carrier based electronic warfare aircraft, you can see the rivets through the paint, some are more proud or deeper than others because countersinks are never exactly the same. A little variation can cause unexpected consequences when pulling a fastener.
Holes for tight fit fasteners are typically in the +-0.003" range for the Navy, and let me tell you, that is hard to achieve consistently. Variations in rpm, bit straightness and quality, holding the drill straight all contribute to poor holes.
You are also correct that any deburring device removes material, in a thin sheet it doesn't take much to enlarge a hole. I have certainly had the burr-away enlarge holes in thin material more than I like. Slow speeds helps minimize the problem. High speeds, the burr-away can act like a drill.
I sanded the stems down with a dremel tool or die grinder carefully. Others have pushed the stems back in, but I don't care for that method personally
Dan,
Well said about inventing your own way. Once you make a change, you are not only a builder, but also become the design engineer. Every change has consequences, some more than others. Once you push that snowball down the hill, it grows. You just don't want to be caught under an avalanche. That is what engineering is all about, figuring out all possible ramifications of a change all the way to the finish product. And let me tell you, as a professional aerospace engineer, no one ever gets everything correct the first time through. That is what prototypes, beta builders, and kit verification builds are all about.
You may have to high of expectations of exactness. Nothing in building is ever 100% exact, there are always tolerences. Typical sheet metal (bends, cuts, hole placement) in the Navy is about +-0.030", when machining it is typically +-.010". For matched holes, like on the Panther kit, the tolerance is even lower, probably in the +-.003 range. Even on a 60,000 lb carrier based electronic warfare aircraft, you can see the rivets through the paint, some are more proud or deeper than others because countersinks are never exactly the same. A little variation can cause unexpected consequences when pulling a fastener.
Holes for tight fit fasteners are typically in the +-0.003" range for the Navy, and let me tell you, that is hard to achieve consistently. Variations in rpm, bit straightness and quality, holding the drill straight all contribute to poor holes.
You are also correct that any deburring device removes material, in a thin sheet it doesn't take much to enlarge a hole. I have certainly had the burr-away enlarge holes in thin material more than I like. Slow speeds helps minimize the problem. High speeds, the burr-away can act like a drill.
I sanded the stems down with a dremel tool or die grinder carefully. Others have pushed the stems back in, but I don't care for that method personally
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rlweseman
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Re: Updrilling for flush blind rivets
Posted by Dan Heath 8/9/2014
I just re-read Dan's post. I am thinking that the reference to a -41 is that it is the rivet that "should" be used to mate two .025 pieces, but that a -41 is not produced. You know, one of the reasons that I went to a "metal" plane is because I was under the impression that metal gives more opportunity for "exactness", un-like composites. I like repeatable processes. So, if something works for one, it should work for all, and I still have not come to grips with why that is not true in this case.
One thing that I want to caution builders on, is that if you are going to "invent" your own way, or take someone elses' way of doing things that contradicts the builders manual, you NEED to do your testing and investigate what the results of doing it this way, may be. Dan knows what he is doing and he has proven that it works, so by doing it some other way, puts the results on you and you must take the responsibility for doing so. Forums like these are for "sharing" of experiences and asking questions, but if the responder, like me, only knows what he is talking about because he stayed in a Holiday Inn Express last night, be wary.
I just re-read Dan's post. I am thinking that the reference to a -41 is that it is the rivet that "should" be used to mate two .025 pieces, but that a -41 is not produced. You know, one of the reasons that I went to a "metal" plane is because I was under the impression that metal gives more opportunity for "exactness", un-like composites. I like repeatable processes. So, if something works for one, it should work for all, and I still have not come to grips with why that is not true in this case.
One thing that I want to caution builders on, is that if you are going to "invent" your own way, or take someone elses' way of doing things that contradicts the builders manual, you NEED to do your testing and investigate what the results of doing it this way, may be. Dan knows what he is doing and he has proven that it works, so by doing it some other way, puts the results on you and you must take the responsibility for doing so. Forums like these are for "sharing" of experiences and asking questions, but if the responder, like me, only knows what he is talking about because he stayed in a Holiday Inn Express last night, be wary.
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rlweseman
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Re: Updrilling for flush blind rivets
Posted by Dan Heath 8/10/2014
Is it a -41 or a -42 for skins? What is your process for cleaning up the proud stems?
I am thinking that my problem with the proud stems on the -42 flush may be the use of the burraway. I noticed when working on another part, that it may be enlarging the hole enough to be the cause of the proud stems. I have not had a chance to test this yet, but will post my results when I do
Is it a -41 or a -42 for skins? What is your process for cleaning up the proud stems?
I am thinking that my problem with the proud stems on the -42 flush may be the use of the burraway. I noticed when working on another part, that it may be enlarging the hole enough to be the cause of the proud stems. I have not had a chance to test this yet, but will post my results when I do
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rlweseman
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Re: Updrilling for flush blind rivets
Posted by Dan Weseman 8/8/2014
HI Guys , I'm doing a little catch up on the cave.
FYI it is noted in the "rivet" section of builders manual that we used -43s on all the skins on the prototype panther and test structures. Notice the "correct" grip rivet isn't even made in the flush type (41 for skins). I also used a # 31 drill and it produced the very best joints with maybe 5 prod stems on the entire aircraft (except tanks which are different) Some of my clecos are worn from years of airplane build but i also have at least 200 new ones mixed in and I had no problem with any of them. Yes they were tighter,..... but that is the entire point. Hmm I bet the rivet is also a bit tighter in the hole also....Some may criticize our choice to let builder choose how they rivet, but post like this prove that in the end Builders will do as they wish in many case!
Dan Weseman
HI Guys , I'm doing a little catch up on the cave.
FYI it is noted in the "rivet" section of builders manual that we used -43s on all the skins on the prototype panther and test structures. Notice the "correct" grip rivet isn't even made in the flush type (41 for skins). I also used a # 31 drill and it produced the very best joints with maybe 5 prod stems on the entire aircraft (except tanks which are different) Some of my clecos are worn from years of airplane build but i also have at least 200 new ones mixed in and I had no problem with any of them. Yes they were tighter,..... but that is the entire point. Hmm I bet the rivet is also a bit tighter in the hole also....Some may criticize our choice to let builder choose how they rivet, but post like this prove that in the end Builders will do as they wish in many case!
Dan Weseman
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rlweseman
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Re: Updrilling for flush blind rivets
Posted by Dan Heath 8/3/2014
Not sure how you get a #30 cleco in a #31 hole. Upon seeing this, since I was having problems with rivet stems protruding, I tried it, and found it almost impossible to the the cleco in the hole. I know the plans now call for #31 drill bit to be used, but I have decided not to do that. I also think I may have found the problem for my "protruding rivet" problem, which I will be doing some tests on this coming week and will post the results. What I do know so far, is that the -42 rivet gives me a problem, while the -43 does not. Take this with a grain of salt as I don't think substituting -43 for -42 is approved. The reason that I even tried it is because I read or heard that the prototype was built using -43 in the beginning. I have no confirmation on that, however.
Not sure how you get a #30 cleco in a #31 hole. Upon seeing this, since I was having problems with rivet stems protruding, I tried it, and found it almost impossible to the the cleco in the hole. I know the plans now call for #31 drill bit to be used, but I have decided not to do that. I also think I may have found the problem for my "protruding rivet" problem, which I will be doing some tests on this coming week and will post the results. What I do know so far, is that the -42 rivet gives me a problem, while the -43 does not. Take this with a grain of salt as I don't think substituting -43 for -42 is approved. The reason that I even tried it is because I read or heard that the prototype was built using -43 in the beginning. I have no confirmation on that, however.
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rlweseman
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Re: Updrilling for flush blind rivets
Posted by Rick Holland 7/15/2014
Thanks, if #30 worked for you that's good enough for me.
Thanks, if #30 worked for you that's good enough for me.
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rlweseman
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Re: Updrilling for flush blind rivets
Posted by Tony Spicer on 7/15/2014
Rick,
That would be your call.
Take two pieces of .025 and drill a #31 hole in each. Insert and remove cleco. Repeat 100 times. If that was easy for you to do, go with the #31.
I'm guessing the switch from #30 to #31 was to reduce proud stems.
Every dimpled hole on my Panther was drilled #30. Tail, wings and aft fuselage and maybe 4 proud stems.
And my right hand is toast.
Tony
Rick,
That would be your call.
Take two pieces of .025 and drill a #31 hole in each. Insert and remove cleco. Repeat 100 times. If that was easy for you to do, go with the #31.
I'm guessing the switch from #30 to #31 was to reduce proud stems.
Every dimpled hole on my Panther was drilled #30. Tail, wings and aft fuselage and maybe 4 proud stems.
And my right hand is toast.
Tony
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rlweseman
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Re: Updrilling for flush blind rivets
Posted by Rick Holland on 7/14/2014
Still confused, so should I ignore the the #31 updrill recommendation in the manual?
Still confused, so should I ignore the the #31 updrill recommendation in the manual?