Non Destructive Attachments

[doctornigel]

I still wonder about all the random holes I see drilled in ribs and skins on many people's planes. (Wings in particular) Any concerns with weakening the ribs and skins and changing the wing without engineering input? (I am NOT an engineer)
Any non-destructive ways to attach things? Would a doubler negate any ill effect or is that just more untested engineering?
From my limited engineering background I understand that long pieces of metal, when they flex or resonate, do so with a specific frequency and have one or more nodes. These are kinda like a fulcrum for the flexing movement, where on one side there is movement in one direction and on the other side movement in the other direction. This would be a critical area to not only have strength (no untested, random holes) but also flexibility (no untested, random doublers).
Or are these things soooo over engineered that I don't have to be concerned about it? Should I be more concerned about the random meteorite strike? Paranoid minds want to know.

 

[Webb]

Drill and move on

I think you are being paronoid. Drill and move on (pretty funny to tell a dentist that).

There are right and wrong ways of doing things such as proper spacing/location and deburring of the holes to prevent weakening or fracture of the metal. For example, you mentioned ribs. Notice the BIG hole known as a lightening hole. A small hole for a rivet or grommet will not weaken or cause failure if you ensure sufficient metal around it and the hole is deburred.

Perhaps the best answer to your question is....it's not that there is a hole there, it's where the hole is.

Other than than, be sure to wear your hardhat just in case its your day for a meteorite strike directly to the top of your noodle.

 

[doctornigel]

Playing devil's advocate, the lightening hole was DESIGNED to be in the rib, it's generally centered, and the edges are rolled to increase strength.

I see a bunch of holes being drilled randomly for convenience in a designed structural part. I'm sure the parts have a safety factor built in but how is that effected? Makes me wonder. I'm sure there are numerous structural failures in history due to some random altercation of a structural part. Hey there's failures of structural parts that were not altered! Paranoid food for thought.

 

[az_gila]

Vans does give...

Playing devil's advocate, the lightening hole was DESIGNED to be in the rib, it's generally centered, and the edges are rolled to increase strength.

I see a bunch of holes being drilled randomly for convenience in a designed structural part. I'm sure the parts have a safety factor built in but how is that effected? Makes me wonder. I'm sure there are numerous structural failures in history due to some random altercation of a structural part. Hey there's failures of structural parts that were not altered! Paranoid food for thought.

...guidance for holes in wing ribs.

http://www.vansaircraft.com/pdf/Wing_Wiring.pdf

In general, the center of a web takes little or no load, so if you must drill a hole, that would be the best place.... as shown in the location of an extra 3/4 inch wing rib hole in the above document.

Small holes, correctly de-burred and filled with a rivet are regarded as little or no structural loss - examples can be read in the metal repair section of AC43.13 - but pay regard to the minimum rivet spacing specifications, or you could create a "tear along the perforated line" scenario....

 

[johngoodman]

Playing devil's advocate, the lightening hole was DESIGNED to be in the rib, it's generally centered, and the edges are rolled to increase strength.

I see a bunch of holes being drilled randomly for convenience in a designed structural part. I'm sure the parts have a safety factor built in but how is that effected? Makes me wonder. I'm sure there are numerous structural failures in history due to some random altercation of a structural part. Hey there's failures of structural parts that were not altered! Paranoid food for thought.

The holes you are probably referring to are the small alignment holes. I have heard that they are there for the super-duper laser machine to line up on, or to hold on to the work piece. I can't imagine that enlarging them for wires or conduit would threaten the structure. If that were the case the plans would have some bold print saying not to.

John

 

[doctornigel]

The holes I am talking about are the holes people drill for accesssories and conduit, holes to screw clamps to, holes that are for stuff that wasn't on the plans. Some of the holes are quite large (1/2inch). I'll try and post links to some of the stuff I've seen that concerns me.

 

[JDanno]

holes...

Try plugging them with amalgam unless you are into composites only. (a little inside joke)

The holes I am talking about are the holes people drill for accesssories and conduit, holes to screw clamps to, holes that are for stuff that wasn't on the plans. Some of the holes are quite large (1/2inch). I'll try and post links to some of the stuff I've seen that concerns me.

 

[kentb]

It's OK

See Van's doc on rib conduit holes. On holes that will have a screw/bolt through them will be strengthened by the presence of the screw/bolt.
If you are going to attach something heavy or that can flex like a full sized pitot tube, then it is common practice to use a double to distribute the load. I don't know of a formula to judge the size of the doubler, but I would recommend doing what others have successfully done before (curse this site).

I would probably be easier to find out the proper way to do something if you had a more specific question.

Ask up, there is a lot of knowledge here. And you can always call Vans for answers.

I drive by Vans each day on the way to work and have stopped by to many time to ask, "Did I do this correct"? I have been told more then once that the plane would fly fine if you left out half the rivets. Not that I did that, but there is a lot of safety engineered into these planes.

Kent