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  #1  
Old 06-12-2020, 02:08 PM
Harley_Pilot Harley_Pilot is offline
 
Join Date: Aug 2016
Location: Granite Bay, CA
Posts: 34
Default Removing material thickness 16-02 Step 6

I'm working on Section 16 - Top Wing Skins and step 6 says to remove material at the joint of W-00002 & W-00003. Before I start grinding away, does anyone have suggestions on how I should proceed?
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John House
RV-14A Empennage done
Wings: Starting upper skins 6/2020
Flying: 73 Bellanca 7ECA
Dues Paid 2021
Roseville, CA
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  #2  
Old 06-12-2020, 05:05 PM
Ralph Inkster Ralph Inkster is offline
 
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 1,288
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Option 1 - This process that has worked for me;
-Mark the top surface of each skin "NOT THIS SIDE!". You want to sand the under side of the skins.
-Glue sand paper to a flat piece of wood (preferably 3/4" or thicker). Make a couple sanding blocks.
-Secure skin to workbench so the area you plan to sand down is on a corner of the bench.
-Protect the area you will not be sanding with a diagonal strip of tape.
-Use some pieces of aluminum the same thickness as the skin for spacers (.032 for the inboard skin, .025 for outboard skins most RV models), if for example the taper area is 1" x 1", clamp the spacer sheet 1.5" x 1.5" diagonally from the corner.
-The idea is to sand both the spacer piece and skin in the same motion. This establishes the taper angle. Light even pressure.
-Don't take too much material out, ideally about 1/2 normal thickness along the edges, avoid sanding down to a knife edge.
Of course all this happens before you dimple these skins & should be noted that care most be applied when finally dimpling these thin portions.

Option 2 -
-mark & protect skin as above
-use a big flat file & SLOWLY work towards desired taper
-finish off with fine grit sand paper block
Not as much control with this process but what ever works for you.
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Ralph
built a few RVs, rebuilt a few more, hot rodded more, & maintained/updated a big bunch more

Last edited by Ralph Inkster : 06-12-2020 at 05:08 PM.
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  #3  
Old 06-12-2020, 06:49 PM
avatty avatty is offline
 
Join Date: Sep 2015
Location: Walnut Creek, CA
Posts: 47
Default

After researching this site, I used a 2-inch Roloc pad with good results. Agree you should tape off the area to be worked but disagree about removing material from the underside of each skin (16-02 says to remove material from the top of the inboard skin and the bottom of the outboard).

This definitely is something to try first on some scrap material but isn't that hard once you practice a bit and if you take your time.
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Tom
Walnut Creek, CA
RV-14 slow-build - finishing kit in progress
1949 Cessna 140A - IRAN'd 2017
Dues paid for 2021
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  #4  
Old 06-12-2020, 07:03 PM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 4,391
Default Scarf joint

RV7 has a similar scarf joint. I did as mentioned. I used shims to keep from cutting too much. I actually used a Vixen file to get close then various grits of sand paper on blocks to finish. Top of one skin, bottom of the other.
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Larry Larson
Estes Park, CO
http://wirejockrv7a.blogspot.com
wirejock at yahoo dot com
Donated 01/01/2021, plus a little extra.
RV-7A #73391, N511RV reserved (2,000+ hours)
Empennage, wings, fuse, finishing kit, now FWF
Disclaimer
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #5  
Old 06-13-2020, 09:02 AM
Harley_Pilot Harley_Pilot is offline
 
Join Date: Aug 2016
Location: Granite Bay, CA
Posts: 34
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Your suggestions all sound good but I'm not sure about sanding the bottoms of both skins. The instructions say to remove material from the bottom of the top skin and the top of the bottom skin. Is there a reason for sanding the bottom of both skins?
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John House
RV-14A Empennage done
Wings: Starting upper skins 6/2020
Flying: 73 Bellanca 7ECA
Dues Paid 2021
Roseville, CA
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  #6  
Old 06-18-2020, 12:08 PM
Ralph Inkster Ralph Inkster is offline
 
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 1,288
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My suggestion for tapering bottoms was for the plan to polish crowd. Have done this method on a number of wings with great results. Just requires a very slight bend introduced along the diagonal taper line on the underlying skin.
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Ralph
built a few RVs, rebuilt a few more, hot rodded more, & maintained/updated a big bunch more
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  #7  
Old 06-18-2020, 06:22 PM
Harley_Pilot Harley_Pilot is offline
 
Join Date: Aug 2016
Location: Granite Bay, CA
Posts: 34
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I'm sorry. I'm not sure what you mean. Polish crowd?
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John House
RV-14A Empennage done
Wings: Starting upper skins 6/2020
Flying: 73 Bellanca 7ECA
Dues Paid 2021
Roseville, CA
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  #8  
Old 06-18-2020, 06:55 PM
Harley_Pilot Harley_Pilot is offline
 
Join Date: Aug 2016
Location: Granite Bay, CA
Posts: 34
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Okay, I understand what you mean. Thanks!
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John House
RV-14A Empennage done
Wings: Starting upper skins 6/2020
Flying: 73 Bellanca 7ECA
Dues Paid 2021
Roseville, CA
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  #9  
Old 06-18-2020, 07:13 PM
Ralph Inkster Ralph Inkster is offline
 
Join Date: Feb 2008
Location: Calgary, Alberta
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As in folks that like using products like Rolite, Met—All, Blue Magic, Maas, AP or similar to make shiny mirror like planes without having different results in shine between the 2024T3 top pure aluminum layer compared what can be achieved in the alloy layer in the core of the sheet.
So read it as referenced to polish (aircraft finish), not Polish (friends)
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Ralph
built a few RVs, rebuilt a few more, hot rodded more, & maintained/updated a big bunch more
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  #10  
Old 06-18-2020, 10:27 PM
Thierry A Thierry A is offline
 
Join Date: Oct 2015
Location: Casa Grande, AZ
Posts: 21
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I clamped the skin to the corner of the work bench using a piece of angle aluminum at the diagonal I wanted. Used a combination of file and hardwood sanding block. Go slow and check the edge frequently to avoid getting it too thin. I also used a caliper to check thickness on the first go at it but ditched that afterwords. I did as the plans state top of the bottom skin and bottom of the top skin.
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RV-9
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