Using MK319BS blind rivets on bottom of HS skin

[N5916R]

My (RV8) plans have a note on the middle rib of the HS that says optional MK319BS on bottom.

-Assuming you would do this since it is pretty tight to buck rivets in that area, especially on the top row when you are closing it up?

-If you use them, what size holes do you drill to?

-Assuming if you use the blind rivets, you do not dimple the skin nor the rib?

Has anyone done this?

Thanks in advance.

[rvbuilder2002]

MK319BS rivets are countersunk so you would dimple the same as you normally would for the AN426 rivets.
A good hole size is #34. You can final drill to that size after dimpling.

[N5916R]

Why final drill after dimpling? Because there aren't dimple dies to #34?

[rvbuilder2002]

Originally Posted by N5916R

Why final drill after dimpling? Because there aren't dimple dies to #34?

No

The MK319 diam. does not match standard aviation rivet diameters.
We typically use -3 (#40 hole) and -4 (#30 hole) on RV's. The proper size hole for the MK rivet falls in between, so you start with the smaller and then final drill up to where it needs to be. The 3/32 dimple isn't a perfect fit but it is close, and the 1/8" dimple would be way too big (besides the hole being too big also).

You can improve the fit of the MK rivet head by machine countersinking the dimple very slightly after final drilling. I suggest you do a test on scrap first.

[N5916R]

I was going to do another airfoil practice kit for practice before beginning riveting on the HS, so I will experiment with that. Thanks.

[David Paule]

I've used those blind rivets in a few places on my RV-3, and the installation is exactly as rvbuilder2002 described. Be careful on the additional countersinking - I use a single-flute bit in a very slow-turning screw gun (a deburring tool setup) and it takes very little. In fact, some dimples don't need it.

Dave