VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-14
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 02-10-2018, 12:12 PM
Eztroller Eztroller is offline
 
Join Date: Dec 2012
Location: West Linn,Or
Posts: 66
Default AD3 & #40 countersinks

Howdy,

Page 8-04, Step 6: Machine countersink the middle nine holes (shown in Figure 1) in the top and bottom flanges of the HS-00902-1 Front Spar for AN426AD3 flush rivets.

Page 8-08, Step 4: Machine countersink, for dimples in .025 thick skin, the #40 holes in the flanges of the HS-00902-1 Front Spar and HS-00903-1 Rear Spar that correspond to the HS-00901-1 Skins

The bold underlined directions are confusing to me..... What is the difference between a countersink for an AD3, and a #40? Wouldn't these be the same?
Reply With Quote
  #2  
Old 02-10-2018, 12:33 PM
salto salto is offline
 
Join Date: Apr 2015
Location: Wee Waa Australia
Posts: 257
Default

AD3 hole size is #40. In the first instance the rivet will be flush so set up your countersink accordingly, in the second instance a dimpled skin will need to be accommodated so the countersink will need to be slightly deeper to allow for the skin thickness so it lays flat.
Info in section 5 on this.
__________________
Kit 140241
Tail Feathers done
Fuselage kit completed.
wings almost complete.
Flaps and ailerons done.
Canopy next. Phew!
Reply With Quote
  #3  
Old 02-10-2018, 05:26 PM
Eztroller Eztroller is offline
 
Join Date: Dec 2012
Location: West Linn,Or
Posts: 66
Default

Thank you!
Reply With Quote
  #4  
Old 02-12-2018, 08:37 AM
Marc Bourget Marc Bourget is offline
 
Join Date: Apr 2009
Location: Stockton, California
Posts: 178
Default

Keep in mind, "so it lays flat" means no more than .002" between the countersunk member and the dimpled skin."
Reply With Quote
  #5  
Old 02-12-2018, 09:09 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 7,651
Default

Quote:
Originally Posted by Marc Bourget View Post
Keep in mind, "so it lays flat" means no more than .002" between the countersunk member and the dimpled skin."
Not necessarily...... It depends on where you are measuring.

Section 5 gives a specific recommendation for countersink depth for a dimple regardless of the thickness of the skin that is dimpled.

Different skin thicknesses can result in differing amounts of gap between the sub structure and dimpled skin, in the areas between the rivets. From a strength consideration a small gap here is not of concern.

The strength comes in tight joints at the rivet locations. This is where no more than .002" is acceptable. It is also why the .007" deeper for a dimple rule is used. It will assure that in all situations, the dimple fits tightly in the countersink with no compromise in finished appearance.
__________________
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #6  
Old 02-12-2018, 11:17 AM
OrenAir OrenAir is offline
 
Join Date: Jan 2017
Location: Chantilly, VA
Posts: 80
Default

I'm constantly impressed by the knowledge shared by Scott on this forum on a huge variety of topics.
Reply With Quote
  #7  
Old 02-12-2018, 11:35 AM
krw5927 krw5927 is offline
 
Join Date: Aug 2010
Location: Wichita, KS
Posts: 1,849
Default

Quote:
Originally Posted by OrenAir View Post
I'm constantly impressed by the knowledge shared by Scott on this forum on a huge variety of topics.
No kidding! You'd think he WORKS for Van's or something!
__________________
Kurt W.
RV9A
FLYING!!!
Reply With Quote
  #8  
Old 02-12-2018, 02:26 PM
Bavafa Bavafa is offline
 
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 2,347
Default

Another one that got me, not remembering the section, it ask to drill 1/8" drill bit and later on asked to drill #30. I always took #30 as 1/8 size, only to learn that there is about a three thou difference. Now that is precision.
__________________
Mehrdad
RV7A - IO360M1B - SOLD
Dues paid
Reply With Quote
  #9  
Old 02-12-2018, 02:45 PM
swisseagle's Avatar
swisseagle swisseagle is offline
 
Join Date: Feb 2005
Location: 20km outside of Zurich, Switzerland
Posts: 410
Default How does it looks when you countersink to deep?

This is the most building error that builders do, countersinking far to deep to nest a dimpeld sheet onto aluminum structure.

Look at this picture:


This is a piece of aluminium angle, drilled and countersunk to accept a sheet aluminium which is dimpled. Then immersed in epoxy, cured, cut and grinded. So that the desaster gets visible ...

From left to right:
1. The aluminium angle is countersunk until a AN426AD-3-X rivet sits flush.
2. Countersunk until a AN426AD-3-X sits 0.01" deeper than flush.
3. 0.018" deeper than flush.
4. 0.02" deeper than flush.

The picture is not perfect, nor the samples are ... but it shows clearly what will happen. Where metal to metal is in contact and where are gaps. The gap between the angle and the sheet material, between the rivets doesent matter at all, but the gap of the two materials inside the countersunk hole and the dimple let me feel unconfortable!

For sure this got measured with a rivet ... which has also its tolerances.
The measurements are done by a caliper ...

Stay strong with Vans instructions, chapter 5 ! as Scott mentioned (he was working many years for Vans Aircraft btw ):


The clicks may be not the same on all brands of countersunk cages! Test on scrap first.
__________________
Dominik

RV-7A, TMX-IO-320, FM-150, Sensenich FP
Flying since 28. April 2016
Reply With Quote
  #10  
Old 02-12-2018, 02:58 PM
Eztroller Eztroller is offline
 
Join Date: Dec 2012
Location: West Linn,Or
Posts: 66
Default

How do you measure “deeper than flush,” after the countersink has been completed?
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 06:39 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.