If you're building RC planes, drones, helicopters, or even FPV frames, you've probably wondered what size carbon fiber tube you actually need. It's one of those things where there's a lot of conflicting advice online, and honestly, not all of it is helpful.

I've been on both sides of this — building my own RC stuff as a hobby and then helping customers pick the right parts at Carbonpipe. So here's what I've learned about choosing carbon fiber tubes for RC projects, without the marketing fluff.

Start With the Load, Not the Size

A mistake I see a lot: people pick a tube diameter first and then try to make it work. It's better to start with what kind of forces your part will see. A wing spar on a 2-meter glider experiences totally different stresses than a drone arm or a helicopter tail boom.

For RC helicopter tail booms — one of the most common uses — our 3K Roll Wrapped Carbon Fiber Tubes from 5mm to 20mm are usually what you need. The roll wrapped construction handles the torsional loads from the tail rotor really well. A pultruded tube would be stiffer lengthwise but more likely to twist under those loads.

For multirotor drone arms, I typically point people toward tubes in the 10mm to 16mm range depending on the frame size and motor power. A 5-inch racing quad needs something different from a heavy-lift hexacopter, obviously.

Wall Thickness Matters More Than You Think

This is something people overlook all the time. Two tubes with the same outer diameter can have very different properties depending on wall thickness. A thinner wall means lighter weight but less strength, and vice versa.

Most of our roll wrapped tubes use a 1mm wall thickness for standard sizes, and honestly for 90 percent of RC applications that's the sweet spot. But if you're building something really light — like an indoor micro drone or a small fixed-wing — a thinner wall could save you grams that matter.

For heavy-duty stuff like large-scale RC helicopters or long-reach camera drone arms, you might want to go up a size in both diameter and wall thickness rather than pushing a smaller tube to its limit. I've seen too many people try to save weight and end up replacing broken parts.

Length and Stiffness

Here's a rule of thumb I use: for every 100mm of unsupported tube length, you need about 2mm of diameter increase to maintain the same stiffness. It's not exact science, but it gets you in the ballpark.

This is especially important for plane spars and long booms. A tube that feels plenty stiff at 500mm might feel floppy at 1000mm. If you need a long tube, go up in diameter rather than just hoping it'll work.

Our 21-30mm roll wrapped tubes in 1000mm length are popular for larger builds exactly for this reason — they give you the stiffness you need without having to double up tubes or add bracing.

Practical Tips From Real Builds

One thing I always mention to RC builders: leave a little extra length when you cut. It's way easier to trim a tube that's slightly too long than to deal with one that's too short. And believe me, I learned that one the hard way.

For mounting, avoid clamping carbon fiber tubes directly with metal set screws if you can. The pressure creates stress points. Use rubber grommets or nylon spacers — they absorb vibration and distribute the load better. This is standard practice in competitive RC helicopters and there's a reason for it.

Also, if you're drilling holes in carbon fiber tubes for mounting bolts (common in multirotor builds), use a sharp carbide drill bit and back up the inside of the tube with something solid. Go slow, don't force it. A cracked tube is a failed tube.

Quick Reference

• 5-10mm OD: Light RC planes, small quadcopters, control linkages
• 11-20mm OD: Medium helicopters, 5-7 inch drone arms, plane spars
• 21-30mm OD: Large heli booms, heavy-lift drones, long wing spars
• 32mm+ OD: Industrial RC applications, custom builds

If you're not sure where your project fits, just ask. I answer customer questions like this every day and I'm happy to help figure out what works for your specific build.