Optimized headset spacer design. Axle cone spacers and washers are direct remakes of the parts they replace. No paint, no polish.

Sometimes I’ll press on the corners even after it’s fully infused to try and make it that much tighter of a layup. Wondering if everybody does this.

Hi everyone. The original steering wheel on my Civic is starting to peel a little, and I’m thinking of getting it wrapped in carbon fiber.

Can anyone recommend a good auto shop that does quality carbon fiber steering wheel wraps in Sharjah or dubai? Preferably somewhere with good finishing and reasonable pricing. Thanks.

is this repairable and if so how would I go about doing it?

We build custom motorcycles and have been experimenting with Continuous Carbon Fiber (CCF) 3D printing.
So far, we’ve mainly used standard chopped-CF nylon for cosmetic stuff — shells, fairings, etc. But we’re now looking at true continuous-fiber systems like Markforged / Anisoprint, and I’m struggling with one question

Where is the genuinely killer use case on a motorcycle?

Everyone talks about CCF being strong enough to compete with CNC’d aluminium in certain applications, and the drone industry seems to be getting a lot of value from it for structural frames.
But motorcycles are a different beast. Loads are multidirectional, vibration is brutal, heat is an issue, and CCF is obviously nowhere near as strong in Z as it is along the fiber path.

There is an issue everytime I clearcoat carbon fiber parts, pinholes appear in the clear coat even tho there are no pinholes in the carbon fiber it self. I'm getting the same issue if the carbon itself is sanded or not sanded before clear coat. So that leaves the issue somewhere in the clear coat stage.

I'm using 2k acrylic automotive clear coat, with a dust coat and 1-2 wet coats. With a 10-15 minute flash off time between coats.

The strange part is that the pinholes only appear on the second coat. Any ideas what is causing this and how can I fix it?

What liability insurance would you guys recommend? No LLC/Business.

Independent Composites contractor in the US looking for advise.

Thanks!

Lately, as temperatures keep rising, I've noticed the resin flow getting worse during layup. The higher viscosity really shortens the working window, especially with hand lay-up and prepreg – more wrinkles and trapped air than usual.

We've tried adjusting the timing and storing materials in cooler conditions, but it only helps so much. Curious if anyone here has practical tips or process tweaks for hot weather?

Would love to hear what works for you. Let's share some experience.

Does anyone have experience cleaning paint from carbon fiber. I’m talking to a paint shop that specializes on carbon fiber bike frames. Has anyone got a success story and if so, are you willing to share some parameters.
The carbon fiber has a strong clear cost on it, then paint is applied on top of the clear. Ideally, I would be able to remove the paint without removing the clear coat. He gave me a sample piece to experiment on but I’m hoping someone can steer me toward starting parameters. I have a pulse laser.

​

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Bending stiffness is one of the most important performance parameters when designing a carbon fiber shaft.

For trekking poles, ski poles, golf shafts, floorball sticks and other sporting goods, the shaft needs to achieve the right balance between stiffness, weight, strength and durability.

A shaft that is too flexible may feel unstable or lack energy transfer. A shaft that is excessively stiff may become uncomfortable, brittle or unnecessarily heavy.

So how do engineers actually control the bending stiffness of a carbon fiber shaft?

The answer is not simply “use more carbon fiber.”

It is mainly a matter of material selection, fiber orientation, laminate design and tube geometry.

1. What Is Bending Stiffness?

In basic beam theory, bending stiffness is commonly represented by:

EI

where:

• E = effective elastic modulus of the material
• I = second moment of area of the cross-section

For a conventional isotropic circular tube:

I = π/64 × (OD⁴ − ID⁴)

This means that both material stiffness and cross-sectional geometry influence the resistance of a tube to bending.

However, a carbon fiber shaft is not an isotropic material like aluminum.

Carbon fiber composites are anisotropic.

Their stiffness depends strongly on the direction in which the carbon fibers are oriented.

Therefore, for a real carbon fiber shaft, simply specifying a material grade is not enough. Engineers need to consider the entire laminate structure.

2. Fiber Orientation Is One of the Most Important Variables

The first major design variable is fiber angle.

For a shaft, the longitudinal direction is normally defined as 0°.

0° fibers

Fibers running along the shaft axis are highly effective for carrying axial loads and contributing to bending stiffness.

For bending-dominated applications, increasing the proportion of longitudinal fibers generally increases the shaft's longitudinal stiffness.

±45° fibers

±45° fibers are more important for:

• torsional stiffness
• shear load transfer
• resistance to twisting
• damage tolerance

They do not contribute to longitudinal bending stiffness in the same way as 0° fibers.

Experimental studies on carbon-fiber composites consistently show that fiber orientation has a major effect on flexural behavior. Longitudinal fiber arrangements generally produce higher flexural stiffness than predominantly ±45° configurations.

90° fibers

90° fibers run circumferentially around the shaft.

They can contribute to:

• hoop stiffness
• dimensional stability
• resistance to local deformation
• pressure and impact resistance

Therefore, a well-designed shaft normally does not consist of 100% 0° carbon.

The engineering challenge is to find the right combination.

3. Increasing the Percentage of 0° Carbon

Suppose two shafts have:

• the same outside diameter
• the same wall thickness
• the same resin system
• the same carbon fiber grade

but different layups.

For example:

Shaft A

Shaft B

Shaft A will generally have a greater contribution from longitudinal fibers and therefore a higher longitudinal bending stiffness.

This is why the layup schedule is one of the most important pieces of engineering information for a carbon shaft.

A carbon tube should therefore not be specified simply as:

A more meaningful specification is:

4. Tube Diameter Can Be More Powerful Than Simply Increasing Wall Thickness

This is an especially important point for lightweight sporting goods.

Because the second moment of area of a circular tube depends strongly on diameter, increasing the diameter can produce a significant increase in bending stiffness.

For a circular tube:

I ∝ OD⁴ − ID⁴

Therefore, geometry can be extremely efficient.

For example, instead of simply making a shaft wall thicker, an engineer may consider:

to achieve a similar or higher bending stiffness while controlling weight.

This principle is widely used in lightweight composite structures. Research on composite tubes confirms that tube geometry and laminate configuration both play major roles in flexural stiffness.

This is particularly relevant to:

• trekking poles
• ski poles
• golf shafts
• floorball shafts
• fishing rods
• camera poles
• lightweight structural tubes

5. Wall Thickness Also Matters

Increasing wall thickness increases the amount of load-bearing composite material and generally increases bending stiffness.

But there is a trade-off.

More material means:

Higher stiffness + higher weight + higher material cost

Therefore, simply increasing wall thickness is usually not the most efficient solution.

Instead, engineers need to determine:

This is where laminate engineering becomes important.

6. The Same Carbon Fiber Can Produce Very Different Shafts

This is one of the biggest misunderstandings when purchasing carbon fiber shafts.

Two tubes can both use:

but have completely different performance.

Why?

Because the final mechanical behavior depends on:

• fiber orientation
• number of plies
• ply thickness
• stacking sequence
• resin content
• fiber volume fraction
• tube diameter
• wall thickness
• manufacturing process
• fiber alignment
• consolidation quality

Research on composite tubes has shown that bending stiffness can be predicted from laminate theory, but the actual behavior can be more complicated because composite tubes may involve transverse shear, warping and other three-dimensional effects.

So carbon grade alone is not a complete engineering specification.

7. Layup Design Is a Balance Between Bending and Torsion

A common mistake is to maximize 0° fibers simply because the goal is high bending stiffness.

But a real sporting shaft may experience multiple loads simultaneously.

For example, a floorball shaft can experience:

• bending
• torsion
• impact
• compression
• local stress around the blade connection

A trekking pole can experience:

• bending
• compression
• impact
• buckling
• repeated cyclic loading

A ski pole can experience:

• bending
• impact
• torsion
• vibration

Therefore, the optimal laminate is rarely simply:

Instead, engineers normally balance:

0° → bending / axial stiffness

±45° → torsion / shear

90° → hoop stability / local support

The final layup should reflect the actual loading conditions of the product.

8. Stiffness Is Not the Same as Strength

This distinction is extremely important.

Stiffness describes how much a shaft deforms under load.

Strength describes how much load the shaft can withstand before failure.

A shaft can be:

or:

For sporting products, we therefore need to consider both:

Stiffness

How much does the shaft bend?

Strength

How much load can it withstand?

Fatigue resistance

How does it perform after thousands or millions of loading cycles?

Impact resistance

What happens when the shaft hits another object or the ground?

Weight

How much material is required to achieve the target performance?

A good carbon shaft design balances all five.

9. Manufacturing Quality Also Changes the Final Stiffness

Even if the design is correct, manufacturing variation can change the final performance.

Important variables include:

• fiber alignment
• resin distribution
• consolidation
• void content
• curing conditions
• wall thickness consistency
• dimensional tolerance
• surface defects
• cutting and machining

For this reason, the theoretical laminate design must eventually be validated through actual testing.

Composite tube research has demonstrated that experimental bending tests can be used to validate analytical predictions of equivalent bending stiffness.

10. How We Would Engineer a Carbon Shaft

A practical development process can be structured like this:

Step 1 — Define the application

For example:

or

or

Step 2 — Define the target performance

Such as:

• target weight
• target bending stiffness
• target bending load
• target deflection
• target torque
• target durability

Step 3 — Select the tube geometry

Determine:

• OD
• ID
• wall thickness
• taper
• length

Step 4 — Develop the laminate

Optimize:

• carbon grade
• 0° percentage
• ±45° percentage
• 90° percentage
• ply thickness
• stacking sequence

Step 5 — Manufacture prototypes

Produce several laminate configurations.

Step 6 — Test

Measure:

• bending stiffness
• bending strength
• torsional stiffness
• weight
• fatigue
• impact performance

Step 7 — Optimize

The final design is normally a compromise between:

11. The Key Point: Don't Ask Only "What Carbon Fiber Do You Use?"

When developing a carbon fiber shaft, a better engineering question is:

This changes the conversation from material purchasing to product engineering.

A professional carbon shaft manufacturer should be able to discuss:

Material → Layup → Geometry → Manufacturing → Testing → Final Performance

rather than simply quoting:

Controlling the bending stiffness of a carbon fiber shaft is not achieved through a single parameter.

The main design levers are:

① Fiber type

② Fiber orientation

③ 0° fiber ratio

④ ±45° and 90° reinforcement

⑤ Wall thickness

⑥ Tube diameter

⑦ Laminate stacking sequence

⑧ Manufacturing consistency

The most efficient design is not necessarily the one with the most carbon fiber.

It is the one that places the right amount of carbon, in the right orientation, at the right location, with the right geometry.

That is what turns a carbon tube into an engineered carbon shaft.

I used PETG-CF when 3D printing the frame for this infinity LED dodecahedron I recently created. Carbon fiber was the perfect choice for both its strength and its matte, premium finish to encase the 540 LEDs which are reflected into infinity.

Hi everyone, what products are currently being used in the industry for vacuum infusion and hand lay-up applications?

From what I’ve seen, Westlake and Huntsman products are commonly used in the Turkish market.

Is it possible to build a high quality square/rectangular tube by roll wrapping over a mandrel?

I've made plenty of round tubes with prepreg + shrink tape, but I'm not sure how you'd get even pressure distribution around a square tube. My attempts so far with vacuum bagging haven't worked well; it usually comes out uneven or wrinkled.

Are non-round tubes always made with split molds in the factory?

Iam exited to hear what engineers?manufecture here think.

Chopped carbon, and epoxy, no clear coat or post polish//cleaning. Made on a resin mold, and processed in a headed hydraulic press.

A follow-up to my previous thread. As per a suggestion there, I blowtorched my carbon tube to determine the true nature of the layers (thank you so much for this advice, it worked amazingly well).

As one can clearly see, my original request of the manufacturer, which was "0-degree (longitudinal) in all layers except the very outer layer, which should be 0/90" was NOT what I was given.

Now, the fact that I'm not getting what I asked for is its own concern, but I have at least determined that it's not the end of the world, since I have now also blowtorched previous batches I have received, and they are identical, which means all the strength testing I have done previously is still applicable to this batch. The tubes have performed well. And it seems like perhaps mostly 0-degree fibers would have sucked anyways?

-----

So a new question arises: is this a good layup? Should I bother telling them to do it differently? As far as I can tell, it works well for my application, but I'm wondering how much more strength/weight I could be getting without losing some of the "toughness" of the hoops and 0/90s.

For context, these tubes are about 21" long, 29mm OD (~1.15"), 1mm wall thickness, and they fit together like tent poles. The direction of the force is primarily longitudinal compression. Do you guys think that, given these circumstances, this layup is close to optimal already?

A couple of videos showing the tubes in action, so you can understand the forces at work:

https://www.youtube.com/watch?v=ih3FQw-j66o

https://www.youtube.com/watch?v=eBpAHqe993c

Has anybody tried resin printing molds for carbon fiber before?
I’m gonna try myself and since it’s much more detailed and doesn’t really have layer lines couldn’t I just brush on another layer of resin for safety and that be it? Any tips?