Franks LSA

[Frank]

Assembled the center structure of the wings horizontally on the table. Then mounted them in a vertical jig for the addition of nose and back ribs. This will soon lead to welding of the steel parts which go into the wings. Here's a short slideshow/video which shows some details. https://youtu.be/tl4iSH3ONI8

[Bcone1381]

One builder years ago was a mill wright. He used string going thru the jig holes at the front of the nose rib to align them prior to match drilling them to the attach angles.

[davzLSA]

Great progress Frank. The wings look great. I have started working on my ribs. I am putting the stiffener angels on the flange side of the ribs. I dont know if the makes any difference which side they go on? Frank I am going to send your space back to you. Thanks for sending them. I will not be able to use the as I have decided to make my spar caps in one piece. I also plan to sell 2 more sets of one piece spar caps ill be making along with my set of spar caps. I look forward to seeing your progress.

[Frank]

After assembling just the center wing (both spars and center ribs) I discovered this partial structure has a lot of flexibility. In the vertical jig it wants to sag, even between floor supports. Sighting along string lines, I found that adding even more floor supports helps to straighten it out. As far as getting to a straight and flat wing, without twist: it is fixed in the jig at three points and the fourth point is adjustable. In my case, the two root points are fixed, the tip is fixed at the main spar, and the tip at the back spar is free to move. Plumb bobs at the root, middle and tip were used to measure and make sure. Even with all the ribs now fastened the wings are still flexible. It's only when the skin is fastened that a rigid box structure will be achieved.

The nose and back ribs were originally cut to the nominal spar lines of the mylar drawing. I trimmed them according to the various spar cap thicknesses plus 1/32. I made sure the final ribs were not in actual contact with the spar web or cap strips.

I used various string lines to help guide the nose ribs into position. In the end, a string all the way trough the nose jig hole was useful. Also used a curve made from the master template the check the rib curvature and also a straight edge was useful.

Working with the back ribs in the vertical jig is an ergonomic challenge, being down on the floor. Raising the entire structure another 6 inches or more would have made it easier. Crouching on knees and getting the rivet gun into a good position is not easy. And typically, I only discover, late, that double-offset rivet sets are very helpful.

Here's a quick video:
https://youtu.be/ckJtSumW0fc

[sjt]

When you go to buy sheets for wing skin order 12 foot lengths and split in two to save money.

[davzLSA]

Hey Frank, great progress man! On my RV when I did the tip ribs, I used all-thread through the tooling holes to keep all the tip ribs in alignment. I used 1/4 20 all-thread and nuts. I had the same sag in the middle problem as well I did as you have done with that.. Another way I found to maintain the vertical alignment of the front and rear spar was to drill a small hole in each spar in alignment with the wing cord line and drop a string through it, as long as the string does not touch the sides of the holes the 2 spars will be in alignment.