Frozen in Carbonite

Wooo!  My parcel of carbon fibre bits arrived from HobbyKing yesterday so I shot out to the garage straight after dinner to start playing.

Inspired by “The Firegoat” I decided to knock up a quad frame.  I have just enough motors to have a quad and a tricopter in service at the same time and I’m interested to play with the “H-copter” design that popped up on FliteTest recently.

Stability and high capacity are the plan for this one.  The design more or less mirrors the H copter Josh built.  The only difference is that I have used carbon and he used wood.

One thing I learned pretty quickly is that carbon fibre - especially the 10mm square bar  - can’t cope with compression very well at all.  I used washers and didn’t tighten anything up too far.  The next picture shows what happened when I tried to bolt on the motor mount…

The motors have to be pretty tight to keep them from spinning round or wobbling but as the photo shows, they can’t be bolted down.  So, I made up four “plugs” which poke 20mm into the end of the legs and prevent the nut and bolt compressing things too far.  They should add some strength around the joint too.

One obvious annoyance with a quad as opposed to a tricopter is that you need to make four of everything!  The plugs weren’t hard as such, but it took about 15 minutes to get them made up and got quite boring.  Well worth the effort though - they do a good job.

It was midnight before I shut up shop and I had a basic frame made up.  Four motors with 11x4.7 props with mounts stolen from the now-dead double tricopter.  No electronics yet, so tonight there’ll be much soldering in the garage I should think.

Complete with a 2.2Ah battery and with motors and props fitted the new Carbon Copter weighs just 800g!  With the GoPro on the scales it’s just under 1kg.  The lightest tricopter I ever managed was about 1.1kg without a GoPro and had (obviously) less thrust.  So I have high hopes for this little puppy.

It’s traditional to end on a low, so I’ll do just that.  Carbon fibre is brittle.  I decided to do a little crash test with the motors attached - dropped the frame sideways onto the concrete floor of the garage from about 18" up.  There was a sickening crunch.  No visible damage, but one of the legs now twists much more easily than the others.  I can only assume that some of the fibres within the leg have come unstuck.

I think I’ll have to make up some spare legs for the first test flight, and work on some landing gear too.

Very excited to get this thing off the ground!