Cut a small groove on the front to fit the dart. I actually just had mine out today, showing my new neighbor

Wrap the end in strin to stop to wood grain from splitting

Rub it down with cooking oil to stop it from cracking.  Vegetable or animal based is fine.

Do you have access to river cane or bamboo?

I do have easy access to bamboo: I could probably even be paid to take it out :p

I did wrap the ends in jute to keep it from splitting. I’ve got to do some more detail work and to really get off two little knobs of dry rot where old branches were attached (the rot hasn’t progressed at all, though). I’m then going to finish those details, then finish it — probably with mineral oil — then rebind the ends.

I went out today to do some preliminary testing — the first “dart” was the stem of something called frostweed. It broke immediately — the force was far too much. I then walked out to a bamboo grove and scouted for a skinny, standing piece that was dead. I didn’t want to bring out a saw if it didn’t work, which is why I was looking for a dead one. Unfortunately, most were too big (2” around), but I did find a few dead stalks about 7’ long of the right width and cleaned off the branches.

I threw them a couple times and holy cow! Even without a point or flights, they flew beautifully straight and fast. IDK how far they would’ve gone (because of stuff around me), but even without much effort, they were going 15m or so before hitting stuff. It was also way easier to aim than I thought it’d be. I’m not all that good at throwing stuff, so I’m also impressed with how far they went. I also really like the little knob at the handle end — it helps line the thing up. It makes a perfect pocket for my thumb.

I’m really, really excited to finish this and make some quality darts for it.

This is getting annoying. I've now snapped 3 pieces of bamboo while trying to tune them. 2 were alive and dried until they were light, and one was the dead one I mentioned. Any idea why? I  attached a frame from a video I took showing the issue -- see the break?

Also, I think the bamboo I'm using is too wide for the spur on this atlatl -- from my iPhone videos, it seems to be slipping off early.

Either too thin or not actually bamboo. Bamboo is used in arrows which have a much greater degree of acceleration. I can't understand how you could be breaking it. A too thick dart won't flex enough based on my limited understanding and should fly upwards I believe. If it's extremely narrow it might flex too much and break but it would have to be really, really weak for bamboo to break.

Someone put an APB out for Bill.

There's lots of different species of bamboo and cane. Maybe it's a mechanical issue but it could also very well be an issue with that species. Either it naturally grows very thin sidewalls or some other issues.

Bamboo can be bent with heat or tempered without losing a serious amount of strength and that is a much higher heat than 100 degrees so I would say it's unlikely heat is the culprit.