Why Belite loves carbon fibre

This is a guest post from James Wiebe from Belite Aircraft.

We manufacture ‘FAR Part 103’ ultralights. On the English side of the pond, they are called ‘SSDR’ aircraft. (That’s ‘Single Seat DeRegulated’).

The common denominator of these aircraft is that they are simple own, operate, and enjoy!

I thought I’d try and show you how we are able to innovate, in order to produce a superior product.

At Belite, we incorporate state of the art technology into our aircraft – carbon fiber provides the ability to decrease weight while increasing strength. That’s important – especially if you are trying to hit an all up weight of 254 pounds in the U.S, or 10KG/SM wing loading in the UK.

One of the really nifty things about the ultralight aircraft is the regulatory freedom to explore innovative aircraft structures. As an example, Belite has recently been working on improved tail feathers for our aircraft. Our old design used conventional, trusty, 4130 chromalloy steel.

We’ve been using carbon fiber spars in our most advanced ultralight aircraft, for instance, our Belite Superlite. We are now incorporating carbon fiber into some of our tail feathers.

I’d like to show you the old fashioned way of doing tail feathers, which is steel. Have a look at some steel tail feathers:

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Chromalloy steel can be welded into a thing of beauty, as shown in the photograph. The problem is that welding takes time and also takes the skill of a true steel artist. (Fortunately, we have such a welder on our staff.)

But carbon fiber has some very interesting properties.

First of all, Carbon Fiber is unbelievably strong.

In order to appreciate Carbon Fiber, it’s useful to understand steel. Let’s consider the strength of steel, so that we can understand how strong carbon fiber is. Steel has a tensile yield strength of about 63,000 pounds per square inch. That means that a one inch square steel rod can lift 63,000 pounds off the ground, without suffering structural damage to the steel.

Steel is pretty good stuff.

(Hey, we’re not considering anything but tensile strength here. There’s lots of other engineering considerations… but let’s keep it simple.)

Now – let’s take a look at Carbon Fiber. Carbon Fiber has a tensile strength of around five or 600,000 pounds per square inch. This means that the same small 1 inch square rod, when made out of pure carbon fiber, could lift 250 or 300 tons off the ground!

It seems like Carbon Fiber might make a pretty good material to manufacture aircraft parts with.

It also is a great material to make tail feathers out of! Take a look at this carbon fiber horizontal stabilizer structure:

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This is a direct replacement for our steel tail feather. It has attachment points in the same spots, and can be used interchangeably with the original steel tail feather.

The benefits are as follows:

  1. This structure weights just 4 pounds, or 1.82 KG in KiloSpeak.
  2. This structure’s strength is considerably greater than the steel structure that it replaces.
  3. Due to the increased ‘thickness’ of this structure, this improved tail feather can incorporate a slightly more aerodynamic airfoil.

In other words, it’s just better. And of course, the downside is that it’s more expensive to manufacture. Oh well. Can’t have everything!

If you have any questions on carbon fiber, ultralights, or SSDRs, drop me a line. I’d enjoy talking with you. I also maintain a blog about ultralight aircraft. Please have a look.

Until next time, cheers from Wichita, KS (the Air Capital of the World),

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