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Countersinking VS-1003: How deep?

Aiki_Aviator

Aiki_Aviator

Well Known Member
I am up to the point of countersinking the VS-1003 spar and given that it is sandwiched between 2 pieces of aluminium, what is the countersking depth meant to be. Vans states that it should fit the skin, however as a test, is that BEFORE?? Obviously it needs to be flush AFTER riveting. The skin is dimpled, fitting into VS-1003 (countersunk), and laying on the spar doubler (i.e. niether countersunk or dimpled).

My belief that there can be some clearance before as the riveting will 'squash' the pieces together. Is this correct??

My question is, relative to a setting a 426-3 rivet flush with the countersink, is the countersking more/less and by how much (i.e. microstops if available)??

I have been testing various combinations, however I do not have scraps of the same thicknesses, So I am just fumbling about. Any help welcome. Thanks in advance.
 
Aiki_Aviator said:
I am up to the point of countersinking the VS-1003 spar and given that it is sandwiched between 2 pieces of aluminium, what is the countersking depth meant to be. Vans states that it should fit the skin, however as a test, is that BEFORE?? Obviously it needs to be flush AFTER riveting. The skin is dimpled, fitting into VS-1003 (countersunk), and laying on the spar doubler (i.e. niether countersunk or dimpled).
Click to expand...

I started off by creating some test pieces and trying to get a setting where it sits flush. It always seemed like my countersinks were too deep, but that is what it took to get a dimpled skin to lie flat.

Someone recently pointed out that the Van's instructions actually give a spec for how deep to countersink, in section 5. They say you should countersink deep enough to hold a rivet flush, "plus a few clicks deeper on the countersink".

Please look it up to be sure my memory of the instructions is correct. :)

Chris
 
Well what do you know.......good old Section 5 eh!

Well, you know I have looked at the build instructions for a number of weeks and noticed that ref to Section 5C, Section 5E etc.. and basically did not even click that it refered to the 'other' book of general instructions. :eek:

I reviewed the Red covered book long ago and subsequently put it to one side.

Thanks for the jolt. I appreciate it. :D
 
Andrew, I've recently posted to another thread about this very issue, where my advice was to use some scrap and see what works after driving some rivets. If you countersink enough that the parts sit gapless before riveting, you'd gone too deep, but if they aren't gapless after riveting, you've not gone deep enough. 'A few clicks' is inexact and you have to take into account the thickness of the dimpled material, the radius from your dimple dies, etc. The reason to test on scrap is to help you gain experience; you quickly get a feel for the correct setting and thereafter it goes quickly.

However, if you lack the scrap to work with, another way to get experience is to borrow someone else's. The best way is to get another builder who's somewhat farther along to come by and show you. These forums are terrific but sometimes nothing beats a hands-on demonstration both to give you a complete answer and confidence in the results. Some things, like torque values, can be read from a chart. Other things, like riveting technique or deburring or your question are somewhat of an art and best learned in person. If you can't locate another builder, an airframe mechanic would also be useful. Just yesterday I commented in another thread about the value of connecting with your local aviation community.

Good luck with your build; from your build log it looks like you're off to a good start.
 
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