Load test rig design

Among other tasks, which I'll get to in a minute, I finally made motions toward a load testing rig.  The Airchair group didn't have any input, so I'm heading into this without others' experience.

I pulled the Goat drawing profiles to make a low-fidelity model of the wing and nose sections.  Flipping this upside down and with an angle of attack, this let me design a loading rig.  I happened to have a pressure-treated 2x10 that is going to be the main beam.  Beyond that, it was a matter of figuring out how to transfer all the load to the ground in the simplest assembly using 2x4's and screws.

Here's what I have...

The legs are made from 10ft 2x4's.  The supports look good enough to me on paper, but I might make adjustments when building the real thing.  There should be zero doubt that it's sturdy enough before getting a green light.

With the 10ft legs and even leaving on the wheel, that leaves about 2ft of clearance from the ground for adding weights.  In my attic are a few hundred empty gallon milk jugs that are about a foot tall, so is a foot of clearance enough?  From previous finite element analysis, the shape of the wing under load should actually lift the tips away from the ground.

Another funny is how to distribute the load to the ground.  I don't have a large enough concrete/asphalt pad, so this rig will be resting on grass.  It's almost 1500lb sitting on the feet.  Adding another brace to help distribute along more surface area might be prudent, or a piece of plywood under either end.

What else?  A bit of work on the nose that started with fabricating the nose skid from some soft Home Depot aluminum.  This is a full 1" width instead of 3/4" called out in the drawings, because it seemed to fit nicely and was what I already had.

After making the nose skid, I really wanted to rivet it, which couldn't be done before covering the nose.  So I covered the nose...

I thought there would be enough material to cover the nose section with one piece, but ended up having to slice off the back and do that separately.

It ended up nice in the end though.  Obviously it's not painted, and still needs to have reinforcement tapes applied.  I was worried the nose would be the most difficult part to cover given how many edges and bolt heads are involved.  It was really not that bad.

It did claim one casualty though ... my trusty old covering iron gave up and broke where the handle attached to the shoe.

Friends who can weld to the rescue!

Wish I could say it was as good as new, but the weld held long enough to finish off the first layer of covering and the handle broke just next to the weld, doh.  It was the right fix at the right schedule though, and I want to say thanks to Trent!

So next up is the load testing rig, sorting out the math for the distributed loading, and then having a load-test party with several close friends.  Assuming it passes, it'll be off to the races for final preps prior to covering the wings.