J

jim miller

Well Known Member
I am having to take the tanks off my RV3 to replace sending units. Is putting
them back on with SS screws advisable? I will grease them as they go on
but was wondering if they might be a problem getting off in future.

Thanks
Jim Miller
 
SS screws

In the past, i have had stainless steel screws lock up in softer aluminum threads. But it really depends on if the screws are rolled threads or cut. Screws that have cut threads seem to have more problems. Stainless screws into heli-coils seem to be OK, just not bare aluminum. JMO
 
stainless screws

I would not use stainless screws as stainless material is softer alloy and will deform easier at the driver end. A&P's that I have talked to have said that they hate when owners switch to stainless screws.
 
The softer head and tendancy to strip the philipps X grooves when trying
to remove is what I was concerned about. I will just stick with the Cad
plated.

Thanks
Jim Miller
 
Corrosion

I know that lots of folks like using SS hardware, because it stays shiny. The reason that cadmium plated steel is the industry standard, is that the cadmium plating will corrode BEFORE the aluminum skins that they attach to. Cadmium is more "noble" than the aluminum alloys used in our RVs. SS will cause the skin to corrode first, as the aluminum is more "noble" than SS. More info can be found below.

http://www.eaa1000.av.org/technicl/corrosion/galvanic.htm

http://www.eaa1000.av.org/technicl/corrosion/where.htm

The screws you refer to are flush items. That means that any skin corrosion would be hidden in the dimples. By the time you find it, it may be to late to polish it out of the skins. Even if you catch it in time, it sure will not be easy to get into all those dimples.
The paint will only protect the skins, IF it is not damaged by the screws as they rotate going in. Just another issue to consider.
Charlie
PS Jim, After re-reading your post, my comments are in reference to using SS screws to attach the fuel tanks to the wing. I doubt that SS screws to attach either the sending units or the access plates would be an issue, due to the considerable increase in material thickness on those items.
 
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Now that we are on the subject of Stainless how about stainless screws holding on Wing-tips? Seen a few. Is this a acceptable attachment method?

Ron in Oregon 9A
 
Stainless screws

I have been following this thread with interest because I am using SS screws in areas such as inspection covers, wingtips, and any area where the screws have to come out at least every year.

My reference point is the fact that my Cessna has had stainless screws for the last 30 years. I have owned it for the last 8 or so and have never had any type of problem. One final consideration, the screws go into nutplates, not aluminum.

Let me know if I am making a big mistake and I will change back to cad.
 
Chakuss is right.
Aluminium and SS are not good friends (at least near the coast). There are a lot of LSA planes where I live that show corrosion when using SS hardware. Without considering the strength of the SS vs the NAS, if you want to put SS screw, I would paint the plane and put tinnermans under the screw to be sure not to damage the paint and to delay/limit (not avoid) the corrosion.
 
Magnify the threads of an SS screw removed from a nutplate and you will see why I will not use any SS screws anywhere. Cad screws work just fine and get replaced at the first sign of a grip problem with the driver.
 
uh oh, guess we are all going to have to replace all those aluminum rivets holding our stainless steel fire wall on.

erich
 
erich weaver said:
uh oh, guess we are all going to have to replace all those aluminum rivets holding our stainless steel fire wall on.

erich
Click to expand...

Nah.. With all the oil spooge coming out of a lycoming, there's no way air and water will ever make it to those rivets. :D
 
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