Rivnut Tests

Rivnuts

A follow up on my post about Rivnuts.  The idea behind a Rivnut is if you don't have backside access you can effectively dill a hole, and similar to a pulled rivet, get it set in.  The difference between a pull rivet which is used as a fastener, a Rivnut is threaded and used much like a nutplate.   These things come in various sizes and materials and have a multitude of application uses.

For the RV-10 Project these are used to attach the Condenser Scoop. The plans mentioned using these to connect the intersect pieces and since I had a few extra's I decided to give it a go.  In doing those I stripped a few of them out... well let me rephrase that, out of the 6 I installed I stripped 5 of them out.  Bill with Airflow Systems was kind enough to send me a few more.

I decided to do some tests to see if I could get an approximate torque value of when these strip out.  Taking some left over skin metal I drilled 3 holes and decided to start with 30 in lbs torque and move up.

The install tool

Set Rivnut

 So what did my tests show me on the value?  What I found is it was fully set around 150-160 in lbs.  Fully set is not distorted and not slipping with the flange part flat against the skin.  Below is a side profile picture of a full set Rivnut (Left) and a Rivnut that stripped at 210 in lbs (Right).

So that was my testing, how did I do in execution?  Well there are a number variables in the works when you're actually driving these things.  I found that the 160 was a good rule of thumb but you sometimes would need a bit more pressure to get it to fully seat.  If there's a gap between the flange and the skin then you know you need to go a bit more.  So Saturday out of the 30 I drove for the scoop attachments points I had 0 strip out.  Fantastic learning experience and another building skill to use down the line.

Not easy to take a picture of

There's the scoop mounted