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  #1  
Old 02-02-2018, 12:42 PM
StuBob StuBob is offline
 
Join Date: Oct 2015
Location: Indianapolis, IN
Posts: 248
Default Questions on my Workmanship

I know what "perfect" looks like, but don't have a handle on "good enough." Two quick questions:

1) Scratches. These were caused by the squeezer while, if I recall correctly, I was standing on my head. Are these scratches something to fix when prepping to paint, something to buff out and prime over now, or absolute death to the part?


2) Gaps. There are places where my ribs weren't absolutely stuck down to the spar, resulting in gaps like this. Is this merely an aesthetic insult, or a threat to airworthiness? I've heard there's a guideline for allowable gap size, but can't find it.
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  #2  
Old 02-02-2018, 04:34 PM
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wirejock wirejock is offline
 
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Default Scratches and gaps

The old rule of thumb is any scratch you can catch a finger nail on is too deep and should be smoothed out. I think the rule is not to remove more than 10% of the thickness.

The gaps are a concern. I don't remember the two but it's not much. Maybe a few thousandth. I would drill out and try again. You can use a slice off some windshield washer rubber hose. Cut a section slightly thicker than the rivet tail. As you drive it, it squishes down and holds the parts tight.
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  #3  
Old 02-02-2018, 05:26 PM
DaveO DaveO is offline
 
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Location: Greenfield, IN
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Stu,
What RV are you building I live East of Greenfield, not too far from you. I built a 7A and sold it and now planning the 14. Be glad to look some time if you wish.
Dave
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  #4  
Old 02-02-2018, 05:27 PM
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JonJay JonJay is offline
 
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Your fingernail will catch almost any depth of scratch, so I wouldn't judge off of that. Take a Scotchbrite pad, maroon, and take the scratch out in an oval pattern along the length of the scratch. If you sand through the Alclad, that is a pretty deep scratch, nominally about 5% of the sheet thickness. That doesn't mean it is ruined.
Although there is no specific standard called out by Vans, as Larry says, 10% is generally accepted as the maximum allowable reduction of thickness. This can be found in many airframe manuals for certified aircraft.

For the gaps between skins or flanges, a gap is allowed as long as a .002" feeler gage can not be inserted into the gap far enough to touch the rivet shank.

Go to Vans site and download the Mil specs from the FAQ page. It will help you with identifying what is acceptable and what is not with your riveting.
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  #5  
Old 02-03-2018, 07:46 AM
StuBob StuBob is offline
 
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Quote:
Originally Posted by JonJay View Post
Go to Vans site and download the Mil specs from the FAQ page. It will help you with identifying what is acceptable and what is not with your riveting.
Thanks, Jay. I hadn't seen that before. It's absolute gold for the insecure builder who struggles with identifying not-perfect-but-adequte.
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  #6  
Old 02-03-2018, 08:12 AM
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maniago maniago is offline
 
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Location: Bowie MD
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Quote:
Originally Posted by JonJay View Post
Your fingernail will catch almost any depth of scratch, so I wouldn't judge off of that. Take a Scotchbrite pad, maroon, and take the scratch out in an oval pattern along the length of the scratch. If you sand through the Alclad, that is a pretty deep scratch, nominally about 5% of the sheet thickness. That doesn't mean it is ruined.
Although there is no specific standard called out by Vans, as Larry says, 10% is generally accepted as the maximum allowable reduction of thickness. This can be found in many airframe manuals for certified aircraft.

For the gaps between skins or flanges, a gap is allowed as long as a .002" feeler gage can not be inserted into the gap far enough to touch the rivet shank.

Go to Vans site and download the Mil specs from the FAQ page. It will help you with identifying what is acceptable and what is not with your riveting.
This is good info. Recommend the thread be moved to General vs temp for posterity.
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  #7  
Old 02-03-2018, 10:42 AM
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JonJay JonJay is offline
 
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Quote:
Originally Posted by maniago View Post
This is good info. Recommend the thread be moved to General vs temp for posterity.
Thanks Mani. There are several other very good resources that us early builders relied on before VAF was a thing.

Vans Build Manual - used to have basic technique, workmanship, hardware guides, and some standards. Not sure about the new manuals.

Ac-43-1b - although "obsolete", still an excellent resource.

Mil specs now found on Vans site.

Airframe manuals. I had a copy of a Cessna 152, King Air 90, and '42 Army Grumman Widgeon (most similar to RV). All have recommended repair procedures and references that are very helpful especially if you make a mistake.

General Aircraft Hardware Reference Guide available from General Aircraft Hardware company, or similar reference.

I am sure others can chime in on the resources they use. VAF is a wonderful resource but "trust and verify"....
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Last edited by JonJay : 02-03-2018 at 10:44 AM.
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  #8  
Old 02-03-2018, 10:49 AM
StuBob StuBob is offline
 
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Quote:
Originally Posted by maniago View Post
This is good info. Recommend the thread be moved to General vs temp for posterity.
I'd just as soon my scratches weren't preserved for posterity!
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  #9  
Old 02-03-2018, 10:53 AM
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JonJay JonJay is offline
 
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Quote:
Originally Posted by StuBob View Post
I'd just as soon my scratches weren't preserved for posterity!
Those are badges of honor. Anyone who claims they didn't make a mistake on their build didn't build.
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  #10  
Old 02-03-2018, 03:28 PM
StuBob StuBob is offline
 
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Ok, it's done. Sanded out all of those scratches and primed them. Stuck a 0.002" feeler gauge between those pieces and it didn't go, so that's done too.

Thanks, VAF!
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