Building An Airplane From Plans
Dan cranked out two new aft ribs and since we knew they we for the root positions he did not have to make the front and back flanges. He trimmed them a little longer so we would have plenty of edge distance from the first row of rivets:
Positioning the root ribs with the others:
Put the aft wing skin on to see how it fit, Looking Good
After we trimmed the aft root ribs per the dimensions on the plans and got them positioned with clamps it looked really good. (We were working on the left wing aft root rib.) When Dan match drilled through the bracket to the rib the hole at the edge of the rib the hole was really close to the edge, a little too close. Really fustrating. All the dimensions seemed right on. We think that perhaps the holes in the bracket were a 1/32″ off and the rib position was a 1/32″ off and the tilt of the root rib doesn’t help either. Perhaps all these little dimensions add up to the hole being off. Dan claculated the theoritical drawing distances and there is only an 1/8″ from the hole to the edge. Reviewing the plans there is no reason why the rib couldn’t be a little longer on both ends to give adequate edge distance. The rib just overlaps the attach brackets. So we discussed a doubler but decided to remake the ribs and trim them a little longer. One advantage of scratch building is that remaking parts is not imtimidating.
This was an interesting episode, if we had looked ahead in the plans we might have noticed the rib trim dimension was not critical and could be changed. However it would take a lot of time to research every part dimension to see what it’s function is.
Dan & I worked on the wing root ribs. These start are standard ribs but trimmed shorter so you can rivet them to some aluminum angle mounted on the spars. We read on a few websites that on the front rib one can cut out the material between the lightening holes. This makes reaching into the wong easier for rigging. One can see a picture of this in the Sonex website under Support – Instruction Sheets – Wing Installation/Removal Instructions . You can see the oval in the forward root rib. We made the root rib gussets, they are different than the rib gussets.
Dan match drilled the gussets on the left wing ribs. One wants to make sure the gusset flange is mated tights against the rib flange when match drilling the rivet holes with the rib. You don’t want a gap between the gusset flnage and the rib flange when you go to rivet the assembly to the spar.
We primed the rib gussets (and the rib corners they will cover) and riveted them to the ribs. Man, there are a lot of holes in those gussets. Lots of clecos on and off as you are riveting. Some of the rivets are close to the flanges so we used collars of different heights to raise the rivet gun nose while riveting. Of course we drop them on the floor or bench and spend 5 minutes finding them.
Here are some more pictures of the ribs cleco-ed to the spar. Note that the spar is not riveted yet.
Looking Good!
We located the gussets to the ribs. There are a lot of holes on those parts
Match drilling the ribs to the spars took some thought. Since we are scratch building, the pilot holes are located in the spar and the rib flanges are blank. The basic process for the right wing was:
1) Lay out spar for wing station locations
2) Align and clamp the FWD ribs to align with the upper and lower spar caps using procedure described in plans for overlap of wing skin.
3) Match drill the FWD rib then remove.
4) After all FWD ribs have been matchdrilled, clamp spacers (Wxx-x and Wxx-x) in correct location at each wing station for AFT ribs and then match drill.
5) Tape spacers in place and then remove clecoes.
6) Clamp AFT ribs at proper alignment with top and bottom of spar cap and match drill.
Ribs to rear spar
Dan located the forward ribs for the right spar. The method on the plans uses sheetmetal strips of the skin thickness to get the tangency between the spar cap and the ribs. Sometimes the flange of the ribs were a tiny bit under bent but we are sure the rivets will pull everything tight. The ribs lined up really nice.
Dan & I have been cleaning up the wing ribs. Have been working on them on and off since mid January. The outsides have a “ever so slight bumpy” (that’s a technical term) edge after the router. The process we have been using is:
The real time sink is in the radiused corners bewteen the flanges. I want a nice transition for the straight edge of the flange to the radius. Looking at the light reflection on the edge you can really see the quality of the surface.
The lightening holes also need to be de-burred and smoothed.
So all this take a bit of time.
After cutting out the gussets had to clean them up. This includes filing and sanding all the edges smooth especially in the radius between to flange bends. This is a detail where one can be really picky since the radius should be tangent where it meets the straight edge of the flange. Here is a picture of the completed parts:
With a stack of “identical” parts you can see how consistant your flange bending is. There were a couple that were off just a little. I think it happened becasue I had a really small height flange clamped in the bake while the main body was being bent. There isn’t a lot od surface area for the clamping on the little flange. After I added an additional clamp the bending brake it was a little better. That’s my excuse and Dan seemed to buy it…
