I was also thinking there’s no way it would be solid, but it feels solid to me. Those two places I drilled in were solid too, and I’m hesitant to drill anywhere else.
Maybe someone here has an approximate weight for an 85cm mast only that I could compare to?
I was planning to route the internally but I may be stuck on this one…
Do you have a link to 145mm prop?
Not sure about the link, looks fine for me.
This is the error I get on the link.
The mast doesn’t “look” carbon to me which doesn’t mean it isn’t. If a component is marketed as “carbon” it’s common to be able to see the carbon weave fiber in the layup.
I would look at prices online of brand name carbon masts and compare that to what you paid. That might be clue. Your idea of weight has merit as well.
I didn’t buy a 145 prop I removed material from the original aluminum prop. Some people here have extensive metal working tooling and expertise. I did mine with hand tools and it works fine for me.
Try this link:
Thanks - This link works but the detail in the add isn’t claer whether a component is aluminum, carbon or some weird combination of the two materials.
At one point they say All carbon is $X or All aluminum is also $X which is a clue as manufacturing costs would logically be different.
If you compare the $ in the add to say the Gong products often used here it’s a clue to what All carbon retails for.
@SanguineDrone That doesn’t mean that your mast is bad but certainly harder to determine what it’s made from or if there are usable voids inside.
This is a post here where it looked like they used a really long drill bit to make channels in their mast. Also search “carbon mast” here for other ideas.
I messaged them and they say it’s carbon, waiting to hear back if it’s hollow.
It looks, sounds feels, and weighs like (soild) carbon to me. It’s definitely not metal. On the edge I can see what looks like layers. Maybe it’s black fiberglass 
?
Regardless, I think I will try my best to drill it out with a long drill bit.
I have a similar set up - I think you need to change the propeller too as the stock one from Flipsky is too big. I use a 3d printed one of 140mm diameter and around 6in pitch.
It’s pretty typical to do “sandwich layup” in fibreglassing. Light inexpensive core material like foam and then layers of glass around it. The “sandwich” is often stiffer and lighter than solid. I haven’t worked with CF but I think the principle is the same.
Maybe you will luck out and find the centre core is foam and the drilling is really easy!!
To start with I used the Pacific Meister parametric prop and duct which worked fine even if not the most efficient.
I have since designed my own with the online tool here :
Thanks guys, sounds like I’ll have to do something about the prop too.
It worth it and really not that hard to accomplish. Carefully measure and mark each blade using the center hole as the starting point to get the desired diameter or slightly larger. The material of the blade is thin aluminum (I cut mine using a dremel with a cutoff blade) and then finished the rough blade ends with a grinder (I can hear the master metal workers grinding their teeth already 
)
Mark each blade differently and then spin the prop horizontally on a piece of rod. If a blade ends up at the bottom repeatedly then take a tiny bit more off. Repeat until there is no more bias of a blade down and the prop is balanced
And when cutting and balancing, try to maintain an even shape on the blades as well. This helps with thrust balance.
Another question (sorry to hijack thread), are you guys running 12s and recommending to cut down the prop?
I’m running 18s, do you think that would fit better on power/torque curve for the stock prop?
Voltage has very little to do with motor start torque after a certain point. Reason is motors like these aren’t run in short circuit condition, there’s enough voltage to drive motor to burning at 12S.
An example:
A 65161 (or any type of motor) with phase-phase resistance of 60mohm at 50V has a short circuit current of more than 800A. Motor is therefore driven at a lower voltage by the ESC to keep current within the set limits.
So I did try to drill, and I can only conclude that it is solid carbon fiber as it dulls my HSS bit very quickly.
I’ve only been able to drill about 2-3 inches (7.5cm) even after repeated sharpening of the drill bit.
I guess that I would need a carbide or diamond drill bit, but I’m having trouble sourcing one long enough…
Maybe cheaper to buy a new mast than the long drill bit😳
Indeed, and the hassle of trying to drill a 24inch hole straight down.
Anyone have suggestions for something hollow?
My fuselage has two 6mm bolt holes 55mm apart. Trying to be around 85cm tall.
My two cents for what it’s worth😀
If you go back to your original approach you can get out on the water rather than being in your workshop.
External wiring isn’t ideal but that doesn’t mean you can’t foil.
Either cut down your existing 7.25” prop or buy a Flite prop or alternative and get out foiling.
Spend some time looking at all the incredible builds here on the forum and decide from there what your next rig will be.
Thanks for your help. I did order a flite prop as I don’t believe in myself to shave down the prop.
Certainly I’ll give it a go and see what the results are first!
The manufacture did confirm it’s solid 3k carbon fiber, so I guess that’s that.
You will still have to mod the Flite prop a little.
See this thread
I did see that, enlarging hole to 12mm and printing sleeves should be light work I think.
