I would be a little leary of a printed av-bay. The bay is also the coupler holding the two halves of the rocket together and there can be a lot of stress on that coupler. I've seen rocket fold in half from failed couplers and the way the 3D printing is done, the weak area is in the direction that would break with the rocket folding.
We had a guy 3D print a whole rocket. It only survived to about 100 ft. and then turned into confetti. Some of that was because he was doing a worst case stress test with an I1299N motor. But even so, almost every part failed, the nose cone, the BT, the av-bay, and the fin can.
Keeping the 3D printed parts in compression gets around the problem of z-axis weakness.
I don't know much about 3D printed materials except I know they are weakest on the z-axis when they bend. I also know stiffy tubes came about because some av-bays, even though under compression with end caps and threaded rods, still allowed the rocket to fold in half under the stress of flight. Since that is the weakest part of a 3D printed part, that would be my biggest worry and what I would suspect would be the first type of failure.
Bending puts one side in compression and one in tension. It will fail on the tension side first usually, for a 3D printed part.I don't know much about 3D printed materials except I know they are weakest on the z-axis when they bend.
Following along here. You've posted lots of good information. Over the winter I printed a fincan for a 38mm OD rocket with a 29mm MMT. It also has a printed nosecone. Only been able to get one flight in so far. I plan to ramp from 29mm hobbyline motors up thru H. I constructed it so that I can replace the fincan and try different designs as I learn.
From what I have learned so far I'd have zero concerns about the strength of your fincan. If it were me I'd reduce the infill. You have tapered fins so geometry is on your side for flutter. I'd bet you could easily go under 50% infill.
I suspect the same for your coupler as well. Wouldn't be too difficult to print some test coupons and get some material strength data. Then you'd be able to design to your anticipated max flight loads.
I really commend the OP for sharing his build. I hope this thread and the handful of others like it will begin to show how all the naysayers are/were wrong about the sufficiency of 3D printed parts.
Just a word on the charge building: You've placed the match under the blackpowder. Despite taping over the charge, this can result in inconplete combustion as the flane front and pressure wave displaces the powder in front of the match.
In future charges, consider placing the match on top of the powder, then taping over.
Regarding ematch placement, couldn't you vary the height of the head by feeding more or less charge wire into the well before applying hot glue?
This is big advantage of 3D printing, you can iterate the design as you learn. If you do the end result is a part that is perfectly suited for your application. At least that's been my experience.That's exactly what I did, lol. The picture I showed was probably the deepest one I had.
Learned I can close up the wire hole some, it was big enough that I could insert the ematch through the bottom.
Also discovered that if I need to go over 1.75g, I need to make it taller.
This is big advantage of 3D printing, you can iterate the design as you learn. If you do the end result is a part that is perfectly suited for your application. At least that's been my experience.
Fingers crossed that you don't have any power interruptions today and your print finishes without issue.
True story. It's great for initial runs but crap for volume production.
Where I work, I turned our 3D printer farm loose on making faceshields for healthcare workers for Covid stuff. Had 250 after a few weeks. The rest of the company was still getting organized. Then, in the span of a week, they cranked out something like 40k faceshields on CNC laser cutters. 3D printers are great for initial runs, prototyping, etc but if you want things in bulk, there are better ways.
So true. I used to work in high volume manufacturing and it's amazing what a purpose built machine can do. Where I work now there are a lot of senior managers who think 3D printers are some kind of magical solution to all our problems. 3D printing is well suited for low volume and one off type parts OR something that has very complex geometry and cannot be made through traditional means. Unless I really crank up my output of rockets it fits into both of those categories for my personal use. I find it very helpful for producing jigs and fixtures to make assembly of rockets much easier.
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