Suitable steel for all brackets etc.

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Dan Thomas

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I saw a stainless tube engine mount in a display area at Airventure 2021. Of course, stainless flying wires and cables are common. Some stainless is very high strength, just depends on the alloy. I don't have much experience with the various alloys other than offered at Aircraft Spruce.
Stainless control cables have about a quarter of the life of galvanized steel cables. The stainless is softer and wears away quickly. It's used in floatplanes and amphibs for obvious reasons. Cessna has been putting it in all their singles since 1996 and I've had to replace some of them as early as 600 hours. Stainless doesn't tolerate being dragged over fairleads or rub strips, and in the 600-hour case Cessna had to come up with a much softer fairlead material to get at least some reasonable life out of the cable.

600 hours. Shot.

1632676788304.jpeg
 

BBerson

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Stainless should not be in contact with aluminum if used in salt water, such as seaplanes. It will corrode the aluminum.
 

proppastie

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but try cutting and welding at home with a wife and one-year old baby boy getting under your feet… not to mention what my dear wife might have to say about it… and the landlord! :)
Some places here have what is called "maker space " usually near universities. One can join and use the tools after training or checkout. Lots of stuff needs to be cut before welding or glued.
 

TFF

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I don’t think your supposed to weld in the house next to the kid. Outside in the garage where they don’t want to be, is the place.
 

Dan Thomas

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Stainless should not be in contact with aluminum if used in salt water, such as seaplanes. It will corrode the aluminum.
They are required to use stainless, IIRC. The cable runs between steel control inputs, across fiber pulleys and rub strips, to steel fittings in the aluminum elevator and rudder bellcranks and to steel aileron bellcranks. It doesn't touch aluminum anywhere.
 

misterpeter

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If I had a garage, it would indeed be a lot simpler! I’m going to ‘do the rounds’ with all the farms ands factories close by to see if any can spare me a few square metres of dry space with electricity, preferably 380v :) Then I can start looking to replace my machinery that was stolen a few years ago and get on with the project at last. With the baby there won’t be that much time available to start with anyway! As time goes on, that should improve, hopefully :)
 

Dan Thomas

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With the baby there won’t be that much time available to start with anyway! As time goes on, that should improve, hopefully :)
Experience tells me that babies get older and bigger and want Daddy to play with them when he gets home from work. Then there might be more babies. Believe me, as an old guy, that little kid is worth more than any homebuilt, and you won't have him or her all that long. I am always reminded of the old Harry Chapin song "Cat's in the Cradle." Time is short and regret really hurts. I've seen it in other people.

 

BBerson

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They are required to use stainless, IIRC. The cable runs between steel control inputs, across fiber pulleys and rub strips, to steel fittings in the aluminum elevator and rudder bellcranks and to steel aileron bellcranks. It doesn't touch aluminum anywhere.
Yes, the seaplane cables are stainless. But Thurston said the fittings and bolts in aluminum structures should be cad plated steel not stainless for fittings or bolts.
 

misterpeter

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Yes, Dan, my experience tells me the same: However, I am 65 and am not thinking of having any more babies at this time and have four other children to keep me occupied and vice-versa :) The home built is a family project for ‘spare time’ and not anything done under the pressure of a finish-by-date.
 

Dan Thomas

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Yes, the seaplane cables are stainless. But Thurston said the fittings and bolts in aluminum structures should be cad plated steel not stainless for fittings or bolts.
All the fittings in the Cessna seaplanes are cad-plated steel or aluminum. And the cad sacrifices itself and galvanic corrosion sets in anyway, just later than it would with stainless. None of this stuff lasts for long around saltwater.
 

dino

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And then there is the need to back purge while welding stainless steel.
 

misterpeter

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Hey Dino, that’s what I do all the time, but I’ll not be welding any stainless tubing, so it will not be necessary. Actually makes more sense to do it with 4130, as rust is more prone to start in non-stainless, though I have never heard of anyone doing it…
 

misterpeter

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Aha, and what use is that? Oil on the inside of a tube where you are welding is not ‘helpful’ for penetration of the weld or flow of the molten metal and considering the heat at that spot, would after ruining the weld, evaporate anyway, so that you not only get a potentially bad/weak weld but the intended ‘protection’ from rust at the weld would also be nonexistent? Correct me if I’m wrong, but that sounds like a crazy idea, or an airman’s joke… :)
 

PMD

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No joke and not done before welding. If you hang around airplanes long enough you will find that the imperfect welds of most welded tube airframes allow moisture to enter the tubes with air and condense on the inner walls. On taildraggers I have seen the lower longerons all turned to nothing but rust. Usually discovered in a hard landing where the tailwheel rips off the bottom of the rudder post and a section of both lower longerons. Oil unless it is heated to a temperature that no airplane will see AFTER welding will not evaporate, but it will settle to the bottom of tubes and eventually provide little corrosion protection. In some (usually rotorcraft) welds are made to be 100% sealed and inert gas or just nitrogen is pressurized in the tube and a pressure gauge installed to indicate failure of a weld or development of a permeable crack. The usual belief is that nitrogen will prevent corrosion but unless you evacuate the tube to a fairly low absolute pressure ("high" vacuum) the oxygen and moisture that was in there when welded is still there. Not sure what is done to solve that issue, so hopefully someone who works on helos will chime in.
 

Dan Thomas

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There are fluids that "creep" into everything. Stuff like ACF50, for example. If put into the tubing after welding, and the tubes are sealed up, creeping fluids will continue to coat the surfaces.

The old guys used linseed oil, IIRC. It's the same stuff used in oil paints artists use, and it dries. Once it coats the inside of the tubing it will stiffen up and stay put.

Mouse Milk is a penetrating lubricant. It creeps so much that the outside of the bottle is usually damp with it.
 

TFF

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Oiling tubes is done about half and half. There is arguments both ways to oiling tubes. My opinion is both sides are right at the same time, so you halve to pick a team and stick with it.
 

PMD

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Since we are on the topic, I will re-post link from Kitplanes:

 
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