[TowerTalk] [Antennas] Carbon Fiber Boom

[Roger (K8RI)]

>
> Google Carbon Fiber Tubing, and you will get a lot of vendors who can 
> probably deliver
> carbon fiber tubing from stock.
>
> However, thinking it through, I bet you open whole new tricky 
> materials/design problem.  Carbon fiber
> probably demands special methods of attachment, drilling, fittings, UV 
> resistance, etc,  different from aluminum,
> in the boom/ antenna application.

Carbon fiber composit is quite easy to work with.  In general you treat it 
like working with fiberglass composits except it's dirtier<:-)) (a LOT 
dirtier). Typical construction depends on both individual and cloth fiber 
orientation plus resin.  It's light and strong, but *usually* is laid up in 
conjunction with either fiberglass, Kevlar (TM), or both. Like fiberglass 
composits you can easily drill  and machine it, but I've never seen it 
drilled and tapped. Like fiberglass it's easy to shape in construction, but 
remember it is composed of carbon fibers and resin which means every time 
you sand it you end up with graphite all over the place so cleanliness is 
important.

As for constructing a boom it could be individually constructed for strength 
with the majority of the fibers laid out linearly along the length of the 
tube with a layer(s) wound to add structural ingegrity. The radial lay-up 
can also be replaced with carbon cloth with the fibers oriented on the 45 
degree bias. At any rate the boom would be constructed much the same as the 
main spar in a wing be it fiberglass or carbon fiber and resin.

The horizontal stabilizer on the plane I'm building (Glasair III) is mainly 
carbon fiber and resin with a high density fiberglass cloth overlay using 
Vinylester resin for both the carbon and fiberglass bonding.

I fly the forerunner of a Beech F-33 Bonanza (top speed 225 MPH and gross 
weight = 3100#.)  The strenght of the stab I'm building is so much stronger 
than the F-33's horizontal stab it's difficult to compare them.  I've seen a 
240# man bring his fist down on the stab I'm building and barely even shake 
the plane.  If you did that on the F-33 it'd demolish the stabilizer and 
possibly do damage to the entire empenage.  Until you've spent time working 
with both materials from a comparative approach it's difficult to grasp the 
difference in both strength and weight.

If I had the funds and access to the proper size tubing, I'd not hesitate to 
go with a carbon fiber boom. Actually I'd like to find the stuff at a price 
I could afford so I could build a number of antennas using it.

One thing to remember though: Both fiberglass and carbon fiber composits 
must be protected from UV as both are quite susceptible to damage from it. 
Another is something hitting an aluminum boom hard enough to dent it leaves 
a dent. Something hitting a carbon fiber boom hard enough to leave a dent 
will leave a crushed spot with little or no structural integrity which is 
why you often find Kevlar and or fiberglass in the mix.

BTW if we are going to talk about these esoteric materials, there is a new 
composit being talked about that consists of  aluminum fibers and resin. IOW 
a new advanced composit using Aluminum fibers. I've never seen it, but there 
was a recent thread on rec.aviation.homebuilt that had some links to 
information.  Those are no longer on the server, but should be in the 
archives or available on a Google search.

Of course going one step farther there are the carbon nano-tubes but I think 
that material is a long way from becoming comercially viable and affordable.

Another interesting material is filaments made of Tungsten Carbide and what 
kind of a composit you'd end up with there. <:-)) I've worked with the 
equipment for making them but never seen them used in a composit.

73

Roger (K8RI)
>
> All the Best, 73
> Pat Barthelow     aa6eg at hotmail.com
> http://www.jamesburgdish.org
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> Jamesburg Earth Station  Moon Bounce Team
>
>> Jeffrey Okamitsu wrote:
>>> Has anyone ever thought about using carbon fiber
>>> composite as boom material for a really big array?
>>>
>>> Strength to weight ratio of the material is, of
>>> course, fantastic.  However...it would be very
>>> expensive.
>>>
>>> I'm interested to hear if anyone has attempted
>>> something like this.
>>>
>>> 73, Jeff W3KL
>>>
>>>
>>>
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