Some of you might remember my everlasting battle with manufacturing of the carbon fiber arms. There is a reason why most companies I’ve approached have declined to even try making them. 10x10mm woven square tubes are really difficult to make. Extruded tubes this size is no problem, but they really suck. The arms we sell now are fantastic when it comes to strength, weigh, stiffness and have no warp.
The problem is that the surface finish is almost impossible to get perfect. So far we’ve discarded large parts of batches due to these imperfections and it’s really not sustainable. We at least need to break even on the arms. That would mean either almost doubling the price or lowering the standards, or stop selling them altogether.
Right now the most reasonable thing seems to be lowering the cosmetic standards in our quality checks. To be clear; only the surface finish is effected. The structural integrity and function is unaffected and the arms will be just as strong as before. The difference is that you might get arms that are scratched, have small dimples, have a visible edge of the carbon or other cosmetic impurities. Again, this will not effect the function or performance of the arms.
Since you will now receive a lower quality product we have lowered the prices.
These woven carbon fiber square tube arms are incredible stiff, strong and lightweight. The torsion (twisting) strength is unparalleled which results in a crisp and precise flying experience, even with high power setups. Unlike extruded carbon fiber arms, these arms can take abuse without cracking. They are also lighter, have more room inside to run wires and are stiffer in all aspects.
Most other carbon fiber square tubes on the market are made using a process called extrusion. Basically at one end there is a huge container of carbon fiber. These fibers are mixed with resin and then gets pushed through a die that has the shape of the tube you want to produce. This process is quick and inexpensive. However as the carbon fibers only run along the length of the tube and are not interwoven. This means that torsion strength and durability is low. These tubes can’t withstand compression nor twisting motion without cracking. Once cracked the tubes lose most of their torsion strength and get so soft that they twist during flight, often causing catastrophic in air failures (don’t ask me how I know). They are also difficult to drill as the force required to cut the carbon strands using a normal drill bit is really close to the compression strength of the tube. More often than not you end up with a cracked tube. Tired of changing arms after a small crash, or even a hard landing, I set out on a quest to find a better alternative. Square aluminium profiles worked but they were heavy and tended to bend in a crash. Wood work great on less powerful setups and during the learning stages of flying, but it lacks the fine control and precision achieved with stiff and high torsion strenght booms. It’s also difficult to hide the wiring.
So I decided to find a manufacturer and make my own woven carbon fiber square tubes. These arms are made using a technique called bladder molding. This means that you start out with a woven carbon fiber cloth, which you wet with epoxy and then place into the bottom part of a two part mould. Multiple layers are laid down at a 45° offset. A balloon is placed in the middle and the carbon fiber cloth wrapped around the balloon. Then the top part of the mould is placed on top and screwed down. The balloon is then inflated at very high pressure pressing the carbon fiber out against the mould. The mould is then placed in a heated chamber to activate the epoxy resin. The pressure in the balloon is maintained for the whole curing time. This process creates incredible strong and nice looking parts. The carbon fiber cloth has fibers woven together at 90° angles and the different layers are placed at a 45° offset to achieve the highest possible torsion, compression and tensile strength.
The wall thickness is 1mm, which leaves 8x8mm of space inside the tube. This makes running wires inside a breeze. Since these arms uses less material than its extruded counterpart, they are 33% lighter. That is 8 grams lighter on a 325mm long arm.
These arms also comes with a 3mm hole pre drilled at 18mm from one end, to fit the tricopter.
Since each boom is hand laid the wall thickness may vary a bit, meaning that the inside dimensions might differ a bit. The outside dimensions however are always the same. Also being hand made there might be small imperfections in the finish of the part.
Use the “circle motor mount” for mounting the motors straight to the arm.
- Material: 3K Carbon Fiber twill weave
- Length: 325mm
- Outside dimensions: 10x10mm
- Inside dimensions: 8x8mm
- Wall thickness: 1 mm
- Weight: ~16.5 grams
Price includes one 325mm long arm.