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Fuel tank dimpling/ countersink question

Jskyking

Well Known Member
I?m preparing tank attachment points and it appears the plans come to a dead end in respect on how to treat the #19 holes along the tank edges ( pg 18-09 fig. 1- green circle) and the nutplate screw holes (Pg 18-06 fig 1, blue arrows and 18-09 orange dots) along the inboard edge attachment points

My thoughts are to dimple the tank edges to a #8 screw dimple and Countersink the #19 holes for the nutplate screws once the nutplates are riveted in place.

The deletion of specific instructions may be where Vans has intentionally omitted a production step because they think you should be able to figure it out for yourself.

Has anyone else came to this pause in the plans or am I missing something?
Thanks
Jt

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I don't know about the -14, but on the RV-10, there are no instructions in the wing section, but at the end of the fuselage section, during the wing root fairing attachment, the plans specify what to do here. Read ahead in the -14 plans and see if they are similar.
 
Page 18-03

Its a note vs. a step ;)

Step 10: Remove the T-00001-L Fuel Tank Skin from the Leading Edge Assembly Cradle.

NOTE: Dimple the screw holes in the fuel tank skins using the C-frame tool and a hammer rather than
forming them with a rivet squeezer. This will result in "crisper", better looking skin dimples.



Step 11: Dimple the T-00001-L Fuel Tank Skin as shown on Page 18-05, Figure
 
Dang- missed that note, or it just didn’t resonate with me. Since my ribs are already pro-sealed, I guess my screw holes aren’t going to be as crisp had I used a dimpler.
Thanks for pointing that out.....next time, I’ll read the notes more carefully.
 
One last thought-In theory- would a hand squeezer or a pneumatic squeezer provide a more crisp dimple. I may be able to slide the trailing edge screw holes through the DDRT-2.
I’ll run a test piece using all 3 methods and see if I can discern if one method is better than the other.
 
One last thought-In theory- would a hand squeezer or a pneumatic squeezer provide a more crisp dimple. I may be able to slide the trailing edge screw holes through the DDRT-2.
I?ll run a test piece using all 3 methods and see if I can discern if one method is better than the other.

The main issue with squeezer dimpling is deflection of the yoke: at the end of the stroke all the force ends up applied to the inside half of the die. A "standard" squeezer at 90-100 psi, or a hand-squeezer with mechanical advantage can both generate enough force to produce a crisp enough dimple, if one had a very rigid yoke.

One way to get a crisper dimple on skin edges with standard yokes is to dimple three or four times from different orientations: first have the yoke touch the skin edge on one side, then the other, repeat. Adjust the plunger to the longest setting that still allows the squeezer to complete the stroke without bogging down.

[Random question for today: why doesn't anyone sell tungsten yokes? Nearly double the Young's modulus of steel, and one could buck with it in a pinch. :cool:]
 
The main issue with squeezer dimpling is deflection of the yoke: at the end of the stroke all the force ends up applied to the inside half of the die. A "standard" squeezer at 90-100 psi, or a hand-squeezer with mechanical advantage can both generate enough force to produce a crisp enough dimple, if one had a very rigid yoke.

One way to get a crisper dimple on skin edges with standard yokes is to dimple three or four times from different orientations: first have the yoke touch the skin edge on one side, then the other, repeat. Adjust the plunger to the longest setting that still allows the squeezer to complete the stroke without bogging down.

[Random question for today: why doesn't anyone sell tungsten yokes? Nearly double the Young's modulus of steel, and one could buck with it in a pinch. :cool:]

I wonder if one could drill the top and bottom parts of the yoke and insert a bolt to act as a tie rod to reduce this deflection in cases where it would make sense.

Of course, such drilling would weaken the yoke and so it might not be usable in other cases, where the bolt could not be installed for clearance issues. The shorter and heavier the yoke, the better for dimpling. Can't see why someone with a water jet cutter couldn't make especially heavy yokes for dimpling.
 
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