Got the rear bottom skin riveted in place, fuel tank installed and the top rear skin clecoed on. I want to put wing tip strobes on but don’t have them yet or any wire but I can’t wait to rivet the top skin on. I am thinking about running some ½ inch plastic tubing through the wing, (with a wire or string already in it so I can just attach the “real” wire to it and pull it through). That way I can carry on with the riveting. Anybody have any comments about this?
Thanks,
Bob

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Would just running the actual wires through and let them hang out of the wing tip be ok? I am sure you could get a footprint of the lights you want to use and drill a small hole for the wires to go through.

Run the wires now and put an access panel on the rear side of the spar at the wing tip

This panel would be required  with a strobe set up later anyway.

Eric and Chris, you both have good ideas but at this time I don't know what kind of lights I'm going to use or what size wire they will take. 18 ga. 20 ga. 22 ga. etc. or how many wires will be needed for each light. I will probably go with some sort of LED. The reason for using the tubing would be so I can go ahead and rivet the rear top skin on, it's all set ready to go, clecos in every other hole and rivets just waiting to be pulled in the other holes. I would like to get this wing finished before I put the other wing on the table.

Thanks,

Bob

think about the attachment points and anti-fretting issues!
I made a conduit out of 3/8 aluminum tubing and ran it in the lightening holes in the nose ribs.
Attachments:
Incidentally the entire weight of this was 10 ounces per side including conduit, brackets, grommets and rivets.

The exact size wire you need is probably best determined by which strobe you use. I used one from Kuntzleman, which came with shielded cables of the correct size.

 

The strobe wires aren't all that large, because the average current consumption is not all that high. An advantage a metal conduit would give is that it would shield the wires, and might obviate the need for shielded cables.

 

I seriously considered a conduit, but I just could not justify the additional weight, particularly when I already had shielded cables. However, if the cable is not inside a conduit, there is a real danger of the wires rubbing against a metal edge, and shorting out. I used adel clamps to hold the cable in place, and rubber u-channel wherever the cable was near a metal edge.

 

I would not advise leaving a string to pull the wires through the wing, unless the string is inside a conduit. Otherwise, the wires will almost certainly get scraped or cut when pulling them through the wing.

Thanks for all the input guys. Jim, when I mentioned pulling the wires with a string I meant pulling it through some kind of tubing, like the conduit Ken mentioned. I still have to fabricate the wing tip so I have time to purchase the strobes and wire before closing the wing up completely.

I'll be glad to do so, although I may tell you more than you wanted to know. :)  One of the things I really like about experimentals is that we can tailor the aircraft to our individual wants and desires. However, that means that what one person does may or may not be the right answer for someone else.

 

I was concerned about weight, cost, ease of installation, and field experience/track record. The first two are, I think, self explanatory.The Kuntzleman dual magnum smart units are $248, which is comparable to, or less than, similar units. I, too, installed them when I was building the wings.

 

I have entirely too many cables running to the aft of the fuselage. I really didn't want to have a tail-mounted obstruction light. The Kuntzleman unit solves this by having aft-facing white leds in the wing tip units, so I did not need to either mount a lamp in the rudder, come up with a flexible wire connection between the fuselage and the rudder, nor run an extra wire back there.

 

I also had less weight, since I didn't need another cable, mounting hardware, or lamp assembly. Since Kuntzleman integrates the strobe with the position lights, I also saved weight and complexity there.

 

I liked the fact that Kuntzleman's cable was color coded and shielded. The former meant less chance of error, and the latter, that rfi should be less of a problem.

 

The Kuntzleman units supposedly came with everything you'd need to do the installation. The mounting plates did not quite do what I wanted, so I fabricated others. But the basic stuff was there, and my mounts are just an adaptation or variation of what they did: I borrowed their ideas.

 

I spent a lot of my career managing modifications to large aircraft. One thing that was beat into my head by both my superiors, and by my own experience, was to never buy anything that hasn't already been proven in the field for a while. It's almost guaranteed that you'll find - and probably fix at your expense - some problem in the unit design. That costs money, eats up schedule, and sometimes increases weight and complexity in unexpected ways. I won't buy anything that doesn't have a track record, unless there is absolutely no other way to do it, or the unit has some really important major advantage.

 

The Kuntzleman units have several years of field experience, so I knew I probably wouldn't get bitten by unproven technology. They pretty much did what I wanted. I bought the Kuntzleman units two or more years ago. At that time, they were the best match to my criteria. They might or might not be today; I haven't rechecked what is out there.

 

You may have some needs or wants which differ from my own, so you might arrive at a different conclusion.

 

 

 

The plates are easier to build than describe. They were just sheet aluminum, built by tracing the outline of the strobe on the sheet. I cut the plates with tin snips, and filed to match the strobe outline. There are two plates per strobe. One mounts inside the wing tip; one outside.

 

The plates are riveted together through the wingtip. This helps reinforce the mounting, so the strobe doesn't just pull away from the tip. That was the thing I did not like about the manufacturer's approach.

 

The mounting holes for the strobe are drilled through the plates, and the interior plate has either rivnuts or nutplates installed on it. Machine screws go through the strobe base and the outside plate into the rivnuts or nutplates on the inside.

 

If it isn't clear from the above what I did, holler, and I'll sketch up a drawing of the plates. They really aren't hard or expensive to build.

I bought the DDM-SLC, which runs on 12 VDC, and has the position lights built in. It's the third from the bottom on this page:

 

http://www.kestrobes.com/cat2.htm

 

The smart unit is more expensive. The difference is that the smart unit will run on a wider range of voltages, which shouldn't be necessary.

 

I was thinking this unit was $208 when I looked at the page the other day. That's the unit without the position lights. The one with position lights is $388. I don't know how much this may impact your thinking, but my apologies for the error.

Hi Robert,

 

I did just that and it worked great! I installed a 1 inch plastic tube (white) right in front of the front spar. it is held to the front ribs using tie wraps around it and it holds very well. I also attached a string inside the tube to pass my wires. I got 3 wires in there since I bought a combo wingtip lightning system that has a white light, a position (red/green) and the strobe.

Works real good and if you have a problem, you can pull everything out and put it back in no time.

Even tough you're supposed to be thru with those wires after installing them, you never know when and if you won't have to fix something there. Buy yourself some maintenance EASE and just do it !

Doesn't weight anything and saves TIME and hassle !

By the way, I bought the AEROFLASH NAV/STROBE/POSITION (double flash) light kit from Aircraft Spruce at around 450$.

Good deal and works well.

 

Regards,

Normand

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