Wing Ribs - Aaargh!

[paul330]

I have made extra holes below the tooling holes that are planned to be enlarged for the pitot in the left wing ribs - page 14-4. These are for the Dynon AoA tube. Unfortunately, I now see that the rear of spar/rib bolts (page 14-6) will interfere with the tube. I will contact VANS tomorrow but for extra confidence, is there any reason why I cannot fit the bolts the other way round with the head on the rear of the spar against the rib front flange and the nut/washer on the front? It would save me re-ordering and re-doing a dozen ribs....

 

[Kahuna]

No reason at all.

 

[penguin]

Its just convention that says bolt heads forward, so if there's a reason to reverse the bolt I can't see a problem. BTW, you could just drill another hole in the rib, and additional 1/4" hole is not going to affect anything. Pete

 

[paul330]

BTW, you could just drill another hole in the rib, and additional 1/4" hole is not going to affect anything. Pete

Actually, the hole is 7/16 to take the bushing. 2 holes have slightly less area than the max 5/8 that VANS suggest in their wing wire routing bulletin. I would not be comfortable with a third hole in the area - nor, I suspect, would my UK LAA inspector!

Anyway, thanks for the input - looks like I have dodged the bullet. The thought of having to re-prep all those ribs..............

 

[penguin]

Paul, its LAA Eng rather than your inspector that you should apply to if the holes are not on the drawings - you are unlikely to be able to measure the reduction in strength because of the holes, or of a 2nd set if you need to drill them. The whole mod/concession thing is in a state of disarray at the moment so I would just carry with the easiest method.

BTW why not just make the hole the size that Van's recommends, insert some plastic water pipe and use flexible plastic tubing as sold by SafeAir1 for the P-S and AoA connections? The wiring will also fit in the water pipe. Pete

 

[1:1 Scale]

Actually, the hole is 7/16 to take the bushing.

Double check that. As I found out last night (after my holes have been drilled), Van's bushings are 1/16" larger than the ones supplied by Safe Air, so for the Safe Air bushings, you'll want a 3/8" hole, or an order for more of the bushings used by Van's. I'm thinking some proseal may be in order to either hold the smaller bushings in place, or hold the tubing in place in the larger bushings. Thoughts? Comments?

 

[paul330]

All is well - I think.....

The bolt direction seems to be a non-issue so no problems there.

As for the loss of strength due to the extra hole, VANS had no issue when I asked them. Secondly, they have a bulletin approving holes in the ribs for wiring etc. They allow the front tooling hole to be up to 5/8. 2x7/16 comes out at just slightly less area (yes, I did work it out!) so I guess (practically if not technically) it is in accordance with the plans. In any case, I will need a mod application for the whole heated AoA pitot thing so I will include the tube routing in that. So, Pete, I guess this new improved mod system involving 2 lots of forms instead of one isn't working out so well........

The size of the hole is as specced by VANS to take 437 bushings for the tube. I didn't realise the OD of the SafeAir bushings was less but I already have a stack of various size bushings from VANS. At a few cents each it seemed silly not to have a good stock!

Thanks for the input.

 

[Mike S]

I already have a stack of various size bushings from VANS. At a few cents each it seemed silly not to have a good stock!

Thanks for the input.

Just wait till you get to the fuse wiring

It takes 4 or 5 bushings for each front to back run of wires. And that is just to go from the panel, to the conduit under the baggage floor.

I probably used 30 .750" bushings, and a big handful of other sizes.

I truly am amazed at the amount of wiring these planes eat up, when using a glass panel, remote AHRS, autopilot, dual batt, etc.

As you said, the bushings are cheap------