Aileron Lightening Holes

[Weldingiron]

Good Evening!

Working on the aileron ribs tonight, I realized that somehow the forward lightening hole got moved up a bit of where it should be on everything. This will cause the lightening hole flange to start about 3/16" from the rib flange at it's nearest. I searched AC 43.13 and can't find anything about minimum distances for that type of thing. I already have all of the rib blanks cut out but am wondering if I need to scrap them in the name of structural integrity. I've attached a picture of my form block for a visual if you guys can weigh in. Thanks in advance!

[geraldmorrissey]

Thats a Bob question. However if it keeps you up at night, you already know the answer.
Gerry
Patrol #30

[kilohotel]

Todd,

I bent the lightening holes flanges first using the rubber press method on my first batch of aileron ribs...when I went to bend the edge flanges, the lightning hole flange for the big hole intersected with edge flange. I had to scrap the whole batch... (luckily it preventing me from making the same mistake for the flap ribs)

The reason the flanges intersected for mine was not the location, but that I had flanged the lightning hole with a 3/8" flange. I would think that as long as you can bend both flanges without them intersection, then they should be okay as-cut...

[Weldingiron]

Thanks, guys! Looking at some of the clearances on the plans for other areas and pictures of other builds, I suspect it isn't an issue. I will get with Bob and report back when I have an answer.

[Weldingiron]

I spoke with Bob today and he said that he would want to see 3/8" between where the lightening hole flange ends and the rib flange begins. So it's the 'self education' pile for my aileron ribs and associated jigs. Back to the shop!

[kilohotel]

Make sure you are basing the distance between the flange edges on a 1/4-inch lightning hole flange and that only the two front holes get flanged (see note on the plans). I made the mistake of flanging all three holes with a 3/8-inch flange (as needed for the wing ribs)....and they were not only too close but they actually intersected...

[Weldingiron]

Were you able to get 3/8" between the edge of the flange and lightening hole flange when you changed the size to 1/4"? It still isn't coming out for me.

[kilohotel]

As drawn on the plans, there is not enough space for 3/8". As you can see in the attached photo, there is only 1/2 inch between the edge of the hole and the outside edge of the rib. Accounting for a 1/4 lightning hole flange, with ramp in for the radius on each flange, the separation (flat area) is closer to 1/8 inch...

[geraldmorrissey]

Don't know if this will help because the dims are for a Patrol. Fwd lightening hole dia 2.125, flange width .1875, distance from inside of upr flange to edge of hole flange upr .312, lwr .225. Distance from outside of upr flange to outside of lwr flange 3.30. This a factory rib. Somebody with a factory 4 place rib, please jump in and help this guy out.
Gerry
Pagrol #30

[Weldingiron]

I had the time to go back and redo all measurements and like Kilohotel said, the flat space is closer to 1/8" or 3/16". Perhaps I didn't effectively communicate to Bob what I was talking about when he said it needed to be at least 3/8. The 4-place lightening holes call for a 1/4" flange so may be different from the Patrol's ailerons. I've attached a picture of a rib I formed on the block in question. It looks similar to others I've seen. I have no qualms about remaking everything, I just want to make sure I understand where and how improvements can be made. I really appreciate everyone's help so far in this.

[Weldingiron]

Update! I sent Bob pictures of the ribs in the mail and spoke with him today. He clarified that the 3/8" he was referring to includes the lightening hole flange which is where the confusion arose.

He also said that flanging the lightening holes on the aileron ribs wasn't a necessity given their proximity to the rib flange, but I still intend to since it provides additional stiffness with no weight penalty.