"Paul Ott" <aerohard1@worldnet.att.net> wrote in message
news:tUe89.619$NZ.34732@bgtnsc05-news.ops.worldnet.att.net...
> You are absolutely correct, Peter. I would not want anyone to replace
> any existing bolts in the wing structure with aluminum. I should have
> been clear and stated that these bolts would be good for additions like
> camera or accessory mounts because of their strength to weight ratio.
> Never mess with the factory structural hardware unless your going to
> use a stronger fastener. These bolt are used heavily in the Stearman
> aircraft, but that design usage is entirely different than that of a
> hang-glider. I have to check in on these newsgroups more than once a
> month.
> Paul Ott(aerohard)

Hi paul, I'm no fastener expert but question your comments here.
Although 7070 aircraft aluminum IS very strong (and wears out cutting
tools very rapidly) there is more to fasteners than brute hardness. I.e.,
if the bolt was made from high-carbon steel (which would be MUCH harder
than any aluminum bolt out there) that does not mean it would make a
better fastener! Carbon steel would shatter very easily, and pose a
critical subsequent danger, even though it is a harder substance.

Bolts, as I understand it, are a compromise between hardness and
malleability. Too much malleability, and the bolt will bend. Too much
hardness, and it becomes brittle and shatters. So often (especially with
tools and bolts) they are case-hardened which adds carbon atoms to the
exterior of the metal. This creates a hard and long-wearing surface, but
doesn't make the item totally brittle.

THEREFORE... unless we know more about bolts than just their hardness,
I'd not reccomend using anything besides OEM parts. Keep in mind there
are other factors to consider too, such as temperature range and
corrosion ability. Some metals have dissimilar molecular charges, and
will cause corrosion when in contact with each other (such as mild steel
and certain aluminum alloys- hence another reason for the cadmium-coated
AN bolts.) But beware of AN, a lot of people have the tendency of putting
bolts in their mouth while working on something. I do it all the time.
The pretty goldish cadmium coating on AN bolts is extremely toxic
however. Like lead, it is treated like calcium in the body and not
metabolized but stored in the bones. However, unlike calcium, lead and
cadmium destroy billions of brain cells in the process. (Google for
"Chelation" to learn more...)

Well that's the science lesson for today... heh.


> "Peter Allen" <pallen1@ozemail.com.au> wrote in message
> news:XZK%8.5933$Cq.261758@ozemail.com.au...
> >
> > > I have recently come into possession of a large quantity of "AN"
> > > structural aluminum bolts in various sizes.
> >
> > !!!!!please note!!!!! - most bolts on your hang glider are probably
> > made of steel!
> >
> > Replacing a steel bolt with an aluminium one, will compromise the
> > safety of your wing! -
> >
>

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