N3471
Section IV
Build Log
Jury Strut Installations

Laid out location of left side jury struts. Half the distance from the bolt connecting the wing to the root tube brackets to the first bolt connecting the lift struts to the wing came to 57 inches. This became the center line on where the struts were to be placed. Using a string through a small socket, I marked the points where the lift struts were directly under that mid point.

I verified vertical using a try square with a built-in level as well as visually verifying that the strings were in the same plane.

Where each string met the strut was marked with a pencil.

Using a long piece of 1/2 inch Al6061-T6 tube, the wife and I carefully drilled holes to mount the ST-16L brackets for the left front jury strut. Note that we also put the ST-16F brackets inside the ST-16L brackets. The pictures in the electronic Challenger Manual from Quad City Ultralight do not show this. They show one F bracket between the L brackets and another on the outside. The F brackets are needed for the left N jury strut to be attached later. If one does not put both F brackets inside the L brackets, they will not fit onto the N strut without some unnecessary bending. Doing it this way from the start makes for better fitting brackets and struts with less hassle for the builder. Note the lack of an AN365 nut on the AN525-10R16 bolt. This is just to let the clecos fill all the drilled holes and to make moving the strut easier. We cut the left front jury strut later after the left middle strut is in.

We then repeated the process, sans ST-16F brackets, for the left rear jury strut. Note wife frustrated with husband wasting time taking so many pictures...

Now the rear lift strut does not meet the middle strut at right angles. This leads to hard choices. I decided to use the ST16-L brackets mounted longitudinally along the left rear lift strut with enough gap that I can use a longer than kit provided AN525 bolt. I figured this was better than trying to bend the ST-16L brackets or mount them flush to the left middle strut and bend them around the left rear lift strut. The bolt is basically a pin to hold the middle jury strut to the rear lift strut and it is far more robust than the bracket. An extra 1/4 inch (tops) of gap seemed safe. Wag Aero sells a variety of AN525 bolts, but none are the right length! Eventually found AN525-10R18 bolts at Aircraft Spruce that were the right size.

In order to drill through the left middle strut in the right place with minimal complications, I riveted the ST-16L brackets in place on the left rear lift strut using the ABS-62 rivets. This let me drill the correct hole without so much work or inaccuracies. As the front part of the left middle jury strut is already clecoed in place, we also used the hole placement to take out the horizontal component of a small bow between the left front and rear lift struts.

Similarly, we mounted the front jury strut to the left middle jury strut in a way to take out a small bow in the left front lift strut. Note that the left front jury strut is connected behind the brackets that connect the left middle jury strut to the left front lift strut.

We checked to see if there was a real need to take any bow out of the left rear lift strut with the left rear jury strut, but none was noticeable at the time. Note I did not trim the left middle jury strut until the entire left jury strut system was in place and ready to be painted.

Next, I put in the left N strut. I started with the front.

Drilling the rear portion is more complicated. The N strut meets as a shallow angle and all of the brackets are oblique to one structure or another. One has to make sure there is some gap between where all the brackets meet the middle jury strut to minimize stress concentrations and overlapping brackets.

It looks like this N strut is a long distance away from the others, but it really is not. I had to cut another 1/8 inch off from this point to keep the ST-16 backets from overlapping and still drill through the center of the left middle jury strut.

Using a small half-round file, I removed some metal where the top of the left N strut met the left middle strut. This resulted in a much closer fit, wrapping around the middle strut, and more metal between the first rivet holes and the end of the left N strut.

The final fit sans ST-16F brackets.

The final fit with all brackets clecoed and bolted in place.

The entire left jury strut assembly before trimming the left middle jury strut.

Note that the jury struts are aligned in the direction of normal flight perpendicular to the wing.

The right jury strut followed similarly. Pictures are for documentation purposes and just in case they reveal something unclear in the left jury strut pictures.