Flying wire options

[schu]

Group,

I'm at the point were I need to get some flying wires. The options I know of are:

Use 5/32 1x19 SS cable with swaged ends
Use 1/4 round wires
Use 1/4 streamlined wires

Then I have an option of how to terminate them:

Use AN665 fitings
Use Bob Style 7/16x.120 tubing with formed ends, and threaded for 1/4 28t.

For me price and durability are the important factors. I figured I would just use use 5/32 cable with Bob ends because it's cheap and strong, but if the AN665 ends are significantly safer I may go that route. What about cable vs round vs streamlined? What will hold up against rocks and general bush flying the best?

Thoughts?

schu

[marcusofcotton]

5/32 cable has less drag than 1/4" round, is lighter, cheaper, and easier to make and remake than either of the others. Less likely to have stress fractures as well. I'd prefer galvanized but it's not rolling over pulleys so maybe the stainless steel brittle qualities won't surface (could with repeated rock hits though). Other than those points, it's a close call .

[whee]

I bought streamline wires for the top and round wires for the bottom. If I were to do it again I'd use 5/32 cable.

[Battson]

Why do almost all aircraft use flying wires instead of cable? (I know there are examples, but the vast majority use wire)

[whee]

Tradition? I don't know. I asked Bob about using cable and he told me it didn't really make a difference.

[Mark Goldberg]

There would be some drag penalty for using 5/32 cable as opposed to streamline wires. How much? I don't know. As well as the round shape of cable, you have a turnbuckle, thimbles etc in the breeze. Would for sure save a few hundred dollars though. Mark

[Chris In Milwaukee]

There's a technical description of the difference in an old NSF video that you may have seen before:

https://www.youtube.com/watch?v=ftq8jTQ8ANE

But I think that common opinion is that it isn't going to make a lot of difference in this use case. I'll be using cable, myself.

[schu]

I wouldn't use turnbuckle/thimbles, I would thread it to the correct length then bolt/pin it on, but that bolt does add a lot of drag.

I think what I may do is use 5/32 1x19 cable, then use Bob ends like http://www.airbum.com/pireps/Bearhawk260-11.jpg . While the cable is more draggy than the streamlined wires, the Bob mounts are probably way less drag than the AN665 forks with hardware. It's probably not a wash, but it's probably $500 cheaper.

So what do I need to know about building the Bob mounts? Looks like just heat up the tubing a bit, crush it in a vice, and bend. Make sure that there aren't any stress fractures or sharp bends, thread and enjoy.

[schu]

I just talked to Bob, and know what I'm going to do.

I'm going to have some 5/32 1x9 cable with threaded sweged ends made up.

For the mounts I'm going to build the links according to plans, but instead of using AN665 hardware to go from the cable to the links, I'm going to make them a little longer and cut a 7/16x3/4 notch in the wire end and weld in a piece of 7/16x.120 tubing in place and thread it to accept the threaded ends.

This will be easy to make, retains the ease of bending since the bend is in the links according to the plans, gives me some thick material to weld to, plenty of welding surface, and will be just as strong as Bob's solution. This will be very cheap and very strong.

[whee]

Sounds like a reasonable plan. Why not just use the $11 AN665 ends from ACS?

[Battson]

There would be some drag penalty for using 5/32 cable as opposed to streamline wires. How much? I don't know. As well as the round shape of cable, you have a turnbuckle, thimbles etc in the breeze. Would for sure save a few hundred dollars though. Mark

This is an interesting question...

The Cessna 172 and 180 appear to be far less draggy than a Bearhawk. With both aircraft cruising at exactly the same speed, if you enter a very gentle formation dive, the Bearhawk always gets left behind in the wake turbulence. So - what are the main differences between the two?

One of the most obvious differences is all the extra draggy stuff around the tail. I figure that has to be worth at least a couple of knots at cruise speed.

Of course you also have a different wing, fabric covered body shape, different landing gear design, etc...
I want to do some more formation work with a Maule, and see which one of those two has more drag. One of the few differences is they use struts instead of flying wires.

[schu]

Battson, I would bet that using the airfoiled stab will make up some of that difference as the stabs on a bearhawk are very draggy compared to cessna.

Whee, the ends are 22.75: http://www.aircraftspruce.com/catalo...5terminals.php

At any rate, if I use 5/32 1x9 SS, then a AN665-34R threaded onto a MS21259-5RH, with a MS20667-5 on the other end then cables end up being around $200 if I swage them myself, which I can since I know at least 3 people with the needed tools. If I want to save $100 I could make the links like I mentioned above and omit the AN665 terminals, but I'm not sure that building 4 of those is worth $100 of my time as it will take 1-2 hours to get everything perfect.

I need to call Mark and get my stab airfoil strips
schu

[Battson]

I am already using the profiled stabs, so that isn't a factor in the test flights I've conducted.

[Bcone1381]

We want pictures.

[JimParker256]

Or at least a drawing, showing what you mean...

[DRLPatrol]

Or at least a drawing, showing what you mean...

Ditto......