cable swage

[vixenrookie]

i saw this service buletin on rudder cables, my question has anybody done this with everthing covered? i see pulling the cables out but putting them back might be a little tricky. specially in the tail section.







Cable sizes of less than 1/8" require only one swage crimp. However, cables 1/8" diameter and larger require MULTIPLE crimps for the swage joint to achieve full strength. Use of 1/8" diameter cable has been standard on Kitfox's since early 1993, and it is the intent of this service bulletin to urge you to inspect all nicopress sleeves on your aircraft for proper installation and to complete any unfinished cable swaging.

[HighWing]

I will give an opinion here that might not be universally agreed upon but here it is anyway. The breaking strength of the cable used in the early Kitfoxes - 3/32" SS 7X19 is 920 lbs. The cable strength of the 1/8" SS 7X19 cable on the bigger Kitfoxes is 2100 lbs. The only stress on the cables is foot pressure plus maybe a 30% multiplier due to the cable attachment location vs the pedal location on the rudder pedal arm. If you can squat at anything close to 1400 lbs., I would worry about the double crimps, otherwise, if it were my airplane (and I was comfortable with the crimps), I would just go fly unless someone could give me a compelling reason for the need of the whole 2100 lb. breaking strength.

Then again if the crimps were improperly done, a double crimp would add some measure of safety.

I wonder why the increase in size from the IV to the V on up unless it was for an added measure of safety in the case of fraying due to rubbing somewhere. If that is the case, then the double crimp in a non issue - again my opinion. Has anyone experienced or heard of a properly applied crimp failure. I have heard of fraying resulting in a broken cable.
Lowell

[jtpitkin06]

Vix,

The smaller cable is certainly strong enough. Perhaps it was changed to give a more solid feel on the rudders with less cable stretch.

The reason for multiple crimping is to prevent the cable from pulling through the swage fitting. A proper multiple swage will look like the rudder cable strands are imbedded in the inner wall of the Nicopress fitting with no gap. On the other hand, a single crimp will often look like it is blossomed on the ends and you have only a small area of actual cable grip.

Many builders elect to use the hand bolting type swaging tools. Frankly, I don’t think they don’t have the mechanical ability to properly crimp 1/8 and larger Nicopress sleeves. The hand bolting type tool can bottom out and the cable may look tight but is still able to slip. You just can’t get the pressure like a bolt cutter style or hydraulic swaging tool. It’s also difficult to position the hand bolting type after the first crimp.

Multiple crimping can make up for some of the shortcomings of the hand bolting type tool; but, for a quality crimp, use the larger bolt cutter style. You can often borrow them from boat yards that work on sailboats.

Crimp the center of a sleeve first. The sleeve will elongate in both directions. Next crimp on terminal end, then crimp the working end.

If you do have to re-crimp the cable junctions in the tailcone it could be tough getting in there with a proper tool. I might be tempted to make a new set of rudder cables where I could join the two lefts and two rights on the workbench. Then thread the cables through the guides and install the ends at the pedals and rudder.

John Pitkin Greenville, TX.

[MotReklaw]

also use a quality Go-No Go gauge to check the crimps....

[HighWing]

I rethought this. I checked the swager I have and the single crimp for the 1/8" cable has approximately 75% the surface area of the 3/32 cable. With this in mind, I might want to add at least one more crimp. With the Vixen, I doubt it would be much of a problem because, as recall, it doesn't have the complex adjustable rudder pedal configuration. Simply disconnect both ends of the rudder cable and pull each end out a bit for better access. Tom's advice is a definite must. It will prove either swage method.
Lowell

[vixenrookie]

the swage look fine to me ,done neatly and correctly.i guess what im after is if i get airworthy inspection will they require me to double swag these cables because of the service bulletin? if i do decide to do this i have to cut a inspection hole in the cloth in the bottom of tail section. other wise a will not be able to get into the tail and swage the cables. unless you know someone 3'2" and can swage cables.

[jtpitkin06]

Vix,



Your aircraft is experimental. You don’t have to follow any service bulletin, though is it advisable to do so. Both the initial airworthiness inspection and the annual condition inspection are only concerning the airworthiness. If the inspector judges the single crimps as satisfactory, then you are good to go. However, a check of your own comfort level is in order. If you would like the security of multiple crimps; then, by all means do so.


If you disconnect the rudder cables at both ends, you should get enough slack to re-crimp the junctions in the tail cone without cutting an inspection hole in your fuselage. I can reach the crimps with my turtle deck removed and dropping the baggage sack. Your’s may also be accessible through the turtle deck. If not, then a new inspection hole and cover on the fuselage bottom is not too objectionable. It turns out I can also reach the cables through my ELT access hole on the side of the tailcone.


John Pitkin
Greenville, TX

[vixenrookie]

love this site, you answered every question needed. thank you very much for my your time.