Carbon Fiber Tube for RC Aircraft and Gliders

What a model airframe actually asks of a tube

Light, mostly. That's the loudest demand — every gram in a wing or a fuselage is a gram you carry for the whole flight, and model builders get ruthless about it in a way that surprises people coming from other hobbies.

Then stiffness, which matters more than the weight conversation suggests. A fuselage that flexes under control input makes the model feel vague, and a vague model is one you're always a beat behind. Flying by hand, that's the difference between a plane that goes where you point it and one that argues with you.

Handling comes third and gets ignored until something breaks. A model spends most of its life in a car and a shed, and the rest of it being flown by someone who is occasionally going to get it wrong. Tubes that survive the flying and fail in transit are more common than you'd think.

Carbon handles all of it better than anything else at the price. The question is which tube does which job.

Spars: the wing's backbone

The spar carries the bending load from the wing, and it's the single most structurally important piece of carbon in most models.

Diameter matters most here. Stiffness in bending rises steeply with diameter and only linearly with wall, so the same weight spent on a larger diameter buys far more stiffness than the same weight spent on a thicker wall. A 10mm tube with a 1mm wall will out-perform an 8mm tube with a 2mm wall in bending, for similar weight, and that gap only gets wider as you go up.

That's why glider spars are thick and thin-walled rather than narrow and solid. It looks counter-intuitive if you're used to thinking of solid as strong, but a hollow tube of larger diameter is almost always the better use of the material.

Where the spar joins the fuselage is where the load concentrates. That's the point to reinforce, not the middle of the span.

Joiners. A multi-panel wing needs tubes that slide together. This is the telescoping problem in a different outfit, and it has the same answer: the inner tube's outside diameter needs to be about 1mm smaller than the outer tube's bore, and carbon on carbon will abrade unless you put something between them. There's a fuller treatment in our telescoping guide.

A common mistake with joiners is making them too short. A joiner that goes 30mm into each panel is doing far less than one that goes 100mm, even though it weighs almost the same.

Fuselage: stiffness beats everything

A tubular fuselage is a much simpler structure than a wing, and the requirement is mostly one thing: it shouldn't bend when you push the elevator.

Roll-wrapped tube in the 10mm to 20mm range covers most sport models. Below that the tail moment arm gets long enough that a 8mm tube starts whipping; above 25mm you're carrying weight you don't need unless the model is large.

Length is the enemy. A 900mm fuselage boom will flex visibly at the tail even if the same tube felt rigid at 300mm. If you're long, go up in diameter rather than up in wall — it's the cheaper fix in weight terms, and it's the one that actually works.

Tail surfaces are usually built on a smaller tube or a flat strip, and they're the lightest part of the airframe. Don't over-build them; a heavy tail is worse than a slightly flexible one because it moves the centre of gravity backwards.

Pushrods: where pultruded wins

Worth a specific note, because the right answer here is different from everywhere else on this page.

A pushrod needs to be stiff along its length and takes almost no bending load across it. That's exactly what pultruded tube does well: unidirectional fibres running the length, smooth surface, low cost at small diameters.

Our pultruded tube starts at 1.8mm outside and covers the sizes pushrods live in. It's cheaper than roll-wrapped at these diameters and the surface is smooth, which matters if the rod runs through a guide.

One caution: pultruded is a budget part and it's not strong across its section. If your pushrod is going to get knocked, or if it has to bend round a curve and be held in a guide under load, consider roll-wrapped instead. The T300 versus T700 guide covers why the pultruded range sits where it does.

Pushrod ends. Whatever you use, the ends are where it fails — the glue joint or the clevis. Bond properly (abrade, clean, structural epoxy, 24 hours) and remember the wall, not the adhesive, is usually the limit.

Landing gear and hard points

This is where thin-wall tubes die.

Landing gear takes impact loads in a direction the tube wasn't designed for, and the loads are concentrated at the attachment points. What works, in order of how much difference it makes:

Don't drill the gear leg. Every hole in a loaded tube is a stress concentration, and on a hard landing the crack starts at the hole.

Clamp instead. A clamp spreads the load around the circumference rather than cutting fibres. Our clamps run 10mm to 40mm and are the right answer here.

Sleeve the clamped section. Thin walls crush under a clamp, and a crushed gear leg is a cracked gear leg. A reinforced sleeve inside the tube end gives the clamp something to bite on.

If the gear is going to take real abuse — and it will — consider accepting a slightly heavier wall at that location and saving weight elsewhere. It's usually the tail you can afford to make lighter, not the gear.

Choosing by model type

Model	Typical span	Tube for spar	Tube for fuselage
Indoor / micro	Under 500mm	3mm to 5mm, 0.5mm wall	3mm to 5mm
Small electric sport	500mm to 900mm	6mm to 8mm, 1mm wall	8mm to 10mm
Mid-size glider	900mm to 1500mm	8mm to 12mm, 1mm wall, or a joiner assembly	10mm to 14mm
Large glider	1500mm to 2500mm	14mm to 20mm, 1.5mm wall	16mm to 20mm
Large scale	Over 2500mm	20mm and up, often multiple spars	20mm to 25mm

The wall column barely changes. That's the point — once you're at 1mm to 1.5mm, adding wall is a poor way to buy stiffness, and the diameter is doing the work.

Cutting and finishing

A few things specific to model work.

Cut on the long side and trim. You'll be fitting the tube to a structure you've already built, and structures never come out exactly the length you drew.

Support both sides of the cut. A thin-wall tube will pinch shut if the blade has nothing behind it. Two blocks of wood with a gap, tube across the gap, cut in the gap. The workshop guide covers this and the dust precautions properly.

Seal the cut ends. A dab of thin cyanoacrylate or epoxy on the exposed fibre stops it fraying and keeps moisture out. It's a 10-second job that noticeably extends the life of the part.

Butt joints between panels need a joiner, not glue. Gluing two tube ends together end-to-end gives you a joint in pure tension and almost no bending strength. Any real load will snap it.

What we see people get wrong

A short list of the ones that come up most often.

Buying 2mm wall because it sounds safer. It's heavier, and at these diameters the extra wall isn't buying the stiffness you think. Go up a diameter instead.

Undersizing the joiner overlap. A wing joiner that goes 30mm into each panel is the weak point in an otherwise sound wing.

Drilling a loaded tube. Especially at landing gear and wing attachment points. Clamp or sleeve it.

Pultruded in the wrong place. Great for pushrods, poor for anything taking bending across the section. Match the material to the load, not to the price.

Frequently asked

What size carbon fiber tube for a model aircraft spar?

The diameter scales with span. Under 500mm span, 3mm to 5mm at a 0.5mm wall. Around 1m, 8mm to 12mm at 1mm. At 2m and above, 14mm to 20mm at 1.5mm. Because stiffness rises so steeply with diameter, a larger thin-walled tube beats a smaller thick-walled one at almost any weight you care to pick.

Is a 1mm wall strong enough for a fuselage?

For models up to about 1.5m with a fuselage boom under 900mm, yes, and it's what most people use. Longer than that and the tail starts whipping under control input — the answer is a bigger diameter rather than a thicker wall.

Roll wrapped or pultruded for a model aircraft?

Roll wrapped for spars, fuselages and anything taking bending loads, because the fibres run in multiple directions and it resists loads across the tube as well as along it. Pultruded for pushrods and linkages, where you only need stiffness along the length and the smooth surface and lower cost are advantages.

How long should a wing joiner be?

Longer than you think. A joiner that penetrates 30mm into each panel is doing very little structurally; 100mm into each panel weighs barely more and behaves much closer to a continuous spar.

Can I drill carbon fiber tube for a landing gear mount?

You can, but a clamp is better in every way — it doesn't cut fibres, it spreads the load around the circumference, and it lets you adjust alignment. If you must drill, back the hole with a dowel, use a carbide bit and light pressure, and expect that hole to be where the part eventually fails.