Rudder Cables

[P Johnson]

Morning,


I believe the SS7 rudder cables are 1/8 stainless steel could some one confirm this as mine are slightly magnetic and I need to buy some more Nicopress sleeves. The Nicopress sleeves Kitfox supplies are part number MS51844-24 they are zinc plated and according to aircraft spruce are to be used on galvanised steel but in the Q&A they state can be used on stainless steel cable? My reason for asking is that the zinc coated sleeves are not stocked by the supplier I use in the UK but they do have the tin plated ones (MS51844-84) that are specified for stainless steel cable.

[Benbell4140]

I believe these are stainless but that’s just going off of memory. But I can confirm that certain stainless alloys are ferrous or magnetic. Depends on the iron content.


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[jrevens]

I believe this has been brought up here before. The cable I got from Kitfox is stainless steel. The sleeves were galvanized. To my knowledge galvanized sleeves are not recommended for stainless steel. Tin plated is, but it is less corrosion resistant than galvanized. The best are stainless steel alloy - 18-8 (300 series - 304, etc.).

[P Johnson]

I have a friend who had some MS51844-84 sleeves they look identical to the ones that I got from Kitfox he also had some of the zinc plated MS51844-24 that are supposed to be in the Kitfox kit they are a silver blue colour and look different. The Kitfox web site states that the rudder cables are stainless so I think that the part number may be wrong for the sleeves and that they are now suppling MS51844-84 sleeves which are tin plated.

[Delta Whisky]

Since the subject has come up with some frequency - as stated previously, some stainless steels are magnetic. Some by need (e.g., cookware), some by application (e.g., work hardening), some because the environment it will be used in (temperature, salt, acidic, etc.) makes for a selection of SS that could be magnetic (the internet says you have over 120 types to choose from). The takeaway here is - if your sample isn't magnetic, it probably is SS. If it is and you really need to know - well, there's a bit of calling, studying, or forum time in your future.

[t j]

I tested quite a lot of steel when I was hauling scrap iron to the scrap yard. They gave me a light weight magnet on a key chain. Their standard was to dangle the magnet close to something I suspected to be stainless steel and if the magnet would swing out and touch the material, it wasn't pure enough to get stainless price for it. He said you couldn't tell by holding a magnet in your hand to test it.

When I tested my rudder cables years ago due to a service bulletin, a shop magnet grabbed on hard to the iron cables.

SERVICE BULLETIN #52
DATE: August 11, 1998
SUBJECT: Nicopress sleeves
APPLICABILITY: All Kitfox™ Aircraft
COMPLIANCE: Mandatory
FROM: SkyStar Aircraft Engineering
A variety of Kitfox™ aircraft kits were upgraded to stainless steel rudder cables over the years. We have discovered that in some cases the original un-plated Nicopress sleeves continued to be shipped despite the change to stainless cables. This combination of stainless cables and un-plated sleeves can lead to accelerated corrosion between the differing metals.
Determine if the rudder cables on your aircraft have the affected combination of stainless cables and un-plated sleeves. A magnet can be used to determine of your cables are galvanized or stainless; the galvanized cables are strongly magnetic, whereas the stainless cables are only slightly magnetic, if at all. The un-plated sleeves are copper-colored, while the plated sleeves are zinc-colored.
If your aircraft has the stainless cables and un-plated sleeves, before the next flight, and at intervals not greater than every six months, inspect your cables at every cable/sleeve junction for corrosion. Should any evidence of corrosion be encountered, the cables and sleeves must be replaced before the next flight.
Regardless of the apparent visual condition of the cables, the affected aircraft must have the proper combination of stainless cables and plated sleeves installed within three years from the date the cables were assembled.
Parts orders and requests for further information can be directed to Customer Service at 208 454 2444.

[Eric Page]

As S.B. 52 suggests, my 1995 Series 5 kit was shipped with stainless cables and unplated sleeves. Due to the first builder's terrifying workmanship...

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...I had to remove the installed cables and buy new. I replaced them with 1/8" stainless cable and tin-plated (-84) sleeves from Spruce.

[Jez]

Fantastic info here guys thanks

[Dave S]

Just out of curiosity a few years back, I checked out what failure records I could find of nicopress cable assemblies. I did not find any due to corrosion; however, I found a considerable number due to bad crimping where the cable simply pulled out of the sleeve.

There are a couple ways to check the crimp - simple method is to use a go-no gauge. Another method is to use a micrometer/caliper and compare the reading to the specification.

FWIW - inadequate crimp failures were as common (or more so) with standard airworthiness aircraft as with experimentals.

It is possible that checking the crimp after it is done is fairly important.