one for the tech guys ,what thickness-strenth is lost if any by anodising,is it worth the trouble ?[?]

I have had my own dies struck for two different spars and anodizing is an electrolytic process that does not affect strength or weight.
All it does it is provide a protective coating that helps prevent oxidation.

Is it worth it, well... depends on what you are going to do with it. If it was out in the weather all the time, it would have more value than if it is kept inside.[:o)]

Larry, you forgot to mention that it is the pretty gold color on many of the masts. If I remember my old aircraft days at Douglas, they did blue, red, and you name it. I think with airplanes out in the weather most everything was anodized, with clear that leaves it with the aluminum color.

Most of the time it is clear. John Reynolds chose Gold for his when he has his die made 25 years ago, and the name "Goldspar" was created.

All of my old "friends" are either on pylons in front of VFW Posts or Guard Units, or scrapped out in AZ. I sure am glad you can't recycle fiberglass. [:D]

perhaps i am jumping to the wrong conclusion re anodising i thought
it the process changed the thickness of the alli ?

Powdercoating... yes... painting... yes, anodizing? I would not not how to measure it if it does.

larry recently broke a main boom(anodised)in strong winds,relaced the boom with a non anodised boom same source and noticed the anodised boom was a lot thinner than the non anodised boom,hence the
? re anodising jus wondered if the process was the cause.

Tosh,

that is *not* supposed to happen, and I understand your concern. Every now and then the extruder can screw up... we all do I guess... but I would notify the supplier and ask about it. I would want to know if it came from me because that means:

#1 The extruded screwed the pooch and their QC missed it.
#2 I missed it.

I am not too high on the bandwagon of having them anodized because the guys that do mine "rack" the spars, and when they do... the clamped down on some of them and put dents... small.. annoying dents in about 10% of my spars. They were good about it and worked with me on the problem, and I am sure that the guy that you were dealing with would want to know because when you get a 1000 of them at a time it's hard to inspect them all upon taking delivery.[xx(]

Somewhere in the back of my brain (yes, I have one) a little (unsubstantiated) fact that anodizing a mast slightly increases it's stiffness without adding weight keeps poping up. I can't find the research to back up this statement, but (until someone proves me wrong) I will continue to believe it to be true. Maybe one of you techies can quote chapter and verse to prove it one way or the other. --Jim Linville

Anodizing covers a lot of ground. Some anodizing is done to add color to the item. Some anodizing is done to improve corrosion protection. Some anodizing is done to increase the strength properties of the material.

If you go to the ASTM handbooks and look at anodizing, the book is about 3" thick, much more than can be covered here.

We would need to know the material the mast is made of (there are a bazillion different types of aluminum) and we would need to know the anodizing process used to determine what affect it has on the mast.

You typically, do not lose any strength with anodizing but in some cases, strength properties are improved. Also, some aluminums are specifically formulated to be anodized after forming and machining. Until they are, they have very poor properties.

Paul P

Hi Tosh, Anodizing Alloy is an electrical process of effectively fizzing Lead or tin foil through a corrosive reaction. The item being anodized is coated with the particles fizzed from the anode.

So in effect the anodized item increases in thickness by between 0.2 or 0.10 microns. Against most beliefs the surface of the Alloy is coated not corroded.

The surface is porous and will soak up dye. Which when is colored to the correct shade, is dropped into boiling water. This seals the porous surface, hardening off, providing a durable protective coat.

PS it took me 6 months to perfect this process in my anodising units, frustrating but seams so simple now.

For those of you keeping score at home 1 WHOLE micron is .000039"



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Extrusions necessarily have dimensional tolerances. A section such as a Goldspar is asking a lot of the extruder. They are not usually accustomed to maintaining the kind of tolerance demanded by such an item.
An extruded part is squeezed through a die in the molten state. Sort of like hot tothpaste. When the part emerges from the die it has been chilled but is still pretty hot. It comes out of the die and is carried downstream by a conveyor. The extruded part is then cut to some length. A gripper takes hold of both ends of the tube and stretches it. The stretching process does two things. One: it makes the part straight. Two; it decreases the wall thickness in some proportion to the amount of elongation. Variation in wall thickness from part to part is inevitable. Temperature of the melt and rate of discharge also affects the wall thicknesses.
If one of our mast or boom sections is dimensionally different from a similar section from a different batch, do not be surprised.

Other factors can diminish the strength of an extruded part. There are sometimes "inclusions" in the metal. That means there may be a particle of material other than aluminum imbedded in the part that is not fused to the parent metal. On top of that, the 6061 alloy that was specified may not actually be that particular alloy. I do not mean to discredit extruders here. But stuff happens.

How come I know all this stuff ? 'Cause I have bought tons and tons of extruded aluminum that had some pretty tight specifications. It did not always meet spec.

Measure carefully, worry a lot.