Hey there, I skrewed up in a big way and lost about 8" of carbide drill bit inside of my carbon foil mast.
I was trying to drill a cable channel and it snapped off.
Any ideas how to extract it?
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Oooh that isn’t good😀but you already know that.
Only thing that comes to my mind is to use a router bit to remove the material on the side of the mast where the bit is. Get the bit out and then fix the groove with appropriate material that match’s the original construction.
This approach makes me wonder if that is an alternative to drilling. More affordable/easier to create a wire channel in a solid mast. Machine a groove, lay in a conduit for wire(s) and seal it back up. 
Can you use a magnet to move It out?
Could you go from the mast plate down and see how much of a foam core is in there? Dig out as much as you can, and hopefully the tip of the bit is exposed. If it is you should be able to use a thin rod and tap it out.
Why didn’t you go from the mast plate down initially?
Personally I would have used a different mast and made an adaptor for the Armstrong fuse…
The only way to save the mast is to drill from the top and hope you don’t stall on the stuck bit and then snap another…
If you route through the side it pretty much defeats the purpose of using an off the shelf mast.
I’m not saying you are wrong, just curious why you feel that through the side isn’t a viable approach assuming the repair is done carefully.
Feather the groove to 45 degree angle and lay several layers of CF cloth to fill void. If bonded properly to original shouldn’t it be strong?
How much does a long enough drill bit for this purpose cost?
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The Armstrong mast is about 16mm thick at the bottom, phase cables are 6mm, so you will end up cutting a lot of the strength out if you go up the side.
That mast isn’t that stiff at the best of times either!
I’ve seen posts and stories of people trying the add stiffness to masts by adding hi mod carbon to the outside. It works for a few sessions but eventually delams because it is only has mechanical adhesion.
@Manufoil has drilled a carbon mast down the center - he might have some tips!
It doesn’t seem like the mast has a foam core but a multi-material solid layup. Drilling out some of the integrated layers might also weaken this particular mast.
From the Armstrong FB page today - a 95kg kit surfer landed on a winger from a great height….
Might give you some insights!
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That must have left a mark on whomever or whatever it landed on to snap it like that. 
I’m guessing the light coloured cloth material is the Aramid fibre, don’t see any wood but that doesn’t mean it’s not there. I’ve worked some with Kevlar and it is really challenging to cut or likely drill as the little fibres tend to pull but not break.
Have you tried using an easy out, if you can access and drill a hole in the center of your seized bit at the top of it. They screw in with a reverse thread on a tapered shaft, sometimes used to remove broken bolts. Also don’t know how silicon works on carbon fiber but it was an excellent lubricant for pulling wires through long lengths of heat shrink.
Accessibility for a screw extractor: how far from the surface is the broken part?