control cable

[wb2754]

Hello,
I have a couple of questions for the experienced builders, and engineering folks concerning flight control cables.

In a LSA size aircraft, (AMF-14H Maranda) with a gross weight of 1,300 lb or so, would it be safe to use 3/32 in. galvanized control cable in place of 1/8 in.? The galvanized 3/32 cable has a min tensile strength of 1000 lb compared to 2000 lb for the 1/8 in..

I have noticed that push-pull cables are becoming popular. Has anyone used them? What is your impression, results?

Does the fact that it is an all wood design make a difference?

The -14H is a light weight version of the Falconaravia S-14 Maranda.

Is anyone else building a -14H Maranda?

Thanks,
William

[rwanttaja]

It might help if we knew *why* you wanted to use 3/32", vice 1/8". Is there a problem going around a corner? Do you have a big 'ol spool of it that you want to use?

I know the original Fly Baby had 3/32" control cables, but the designer specified 1/8" in the plans. Of course, with the bracing wires and all, a Fly Baby builder ends up buying a lot of 1/8" anyway.

One difference it will make is in durability; if there's a spot where the cable wears, the 1/8" will do better.

I doubt the strength difference will really matter, but the weight penalty isn't significant. 3/32" cable weighs about 2 pounds per hundred feet, and 1/8" is about 3 pounds per 100 feet. If it's just controls you're hooking up, you've probably got no more than half that. So the weight penalty is about a half pound. Plus a bit extra for heavier turnbuckles, shackles, etc.

Ron Wanttaja

[wb2754]

Thanks,
I was just curious because I have enough of the smaller turnbuckle barrels to do the aircraft. I also have the larger barrels, but none of the clevises.
Looks like it's going to be 1/8in.