Bare Minimum: M2245 to 50,000 feet

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I finally bit the bullet and ordered the nosecone tip and fin can. I ended up deciding against the tapered fins, since I wasn't very confident in any fin flutter calculations for them. I want to experiment with them in the future, but not when I'm flying a nearly irreplaceable motor.

I also got the two nosecone coupler parts laid up. The piece that will connect the two halves came out alright, but I ran into some difficulties on the part that'll attach the nose to the motor. It'll probably be fine, but I'm going to remake it just in case.
 
I did a final recovery test flight with my tubefin at NSL. I ended up ditching the idea of attaching the drogue to the apex of the main and reverted to what I've used in the past on my previous 75mm min diameter, with the drogue on the shock cord, and the main attached directly to the avbay. It worked perfectly, @Valkyrie Recovery Systems makes great parachutes.

When I got home from NSL this evening, there was a package from China waiting for me with the nosecone tip. JLC knocked it out of the park, it's dimensionally perfect, arrived a bit more than a week after ordering it, and was about $30 shipped. Next up is painting a layer of resin on the nosecone parts to fill in the outside weave, then I'll post cure them this weekend. Things are coming together fast for Mudroc.
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Progress has been made.

I remade the nosecone coupler and the joiner part with a new technique. The sacrificial female mold worked fine, but the balloons did not, I didn't have much compression, and the balloon for the coupler seeped air to the point of pulling the inner layer away from the rest of the layers at one end. My new method was to simply print a tapered male plug longer than the female mold. I laid up the fiberglass sleeves on it the same way as with the nosecone parts, but then shoved the female mold over it. The two parts taper locked together, and produced coupler parts with a consistent wall thickness, good inside finish, and a precisely controlled outer contour.
PXL_20240531_042650531.MP.jpg

I also painted a layer of epoxy onto the main nosecone parts to fill the weave a bit and leave a better surface for sanding.

Then it was time for probably the most stressful part of the build. The heated post cure of the fiberglass parts. The oven I had access to doesn't have a super accurate dial, so I spent a ton of time yesterday tweaking the dial and then coming back 10 minutes later to see what the thermocouples read. The System 3000 resin has a very slow, gradual post cure regimen, I assume to ensure the parts don't warp. I finished up around 1 in the morning, and then pulled the parts out when I woke up this morning. I wasn't expecting the resin to change color this dramatically, but the parts are all exactly the same dimensions as when they went in, so I'm calling it a win. The drips are from the layer I painted on.
PXL_20240603_180946750.MP.jpg

The printed fin can, and waterjet bulkhead parts also arrived today.
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Overall the fin can is pretty good. The fit is very tight on the motor, but it does fit, so that shouldn't require too much sanding to adjust the fit. The surface finish is somewhat rough, but I think some wet sanding will smooth it up a lot. My one concern is that it looks like there was some warping of the fin tips. It looks like the fins are all in plane, and I just need to file the tips till the tip chord is flat, but the fin can does require a deeper inspection to make sure the fins aren't warped in a way that makes them crooked. If they are, then this won't be flying at Mudroc. If the fin can is good, then I'm still on track to fly on the 14th.

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I do think that this fin can shape, with the swept fins and scalloped leading edges is somewhat uniquely susceptible to warping. If the fins weren't swept back, or there was a more conventional front end I think it could be printed with less risk of warping.
 
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Bare Minimum is Real!
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It's all structurally complete, but I still have a bit of work to clean up a few surface imperfections on the nosecone, and sand the fin can smooth. I also need to finish the upgrades to my tower. I'm planning on publishing plans and a description of the tower soon.
 
Bare Minimum is Real!
View attachment 649944

It's all structurally complete, but I still have a bit of work to clean up a few surface imperfections on the nosecone, and sand the fin can smooth. I also need to finish the upgrades to my tower. I'm planning on publishing plans and a description of the tower soon.
Good luck!!!
 
Bare Minimum is Real!
View attachment 649944

It's all structurally complete, but I still have a bit of work to clean up a few surface imperfections on the nosecone, and sand the fin can smooth. I also need to finish the upgrades to my tower. I'm planning on publishing plans and a description of the tower soon.
This looks incredible, looking forward to seeing the flight.
 
Opted not to go with the gen 2 casing and a tailcone aft closure?

Curious as to how much altitude you could gain
Beggars can't be choosers. I'm borrowing this casing from a friend, and he only had a Gen 1.

Besides, the Pro 75 tailcone has a very sharp taper. I suspect you'd just see instant flow separation and get no significant benefit from it.

I did kick around various ways to try to integrate a tailcone into the design, but never came up with anything that I liked and that would keep the motor certified. If this flight is successful, I'm going to move towards doing high performance flights with experimental motors, just so I don't have to work around all of the obstacles commercial motors put in the way of performance.
 
I've been a bit of a nervous wreck lately, largely due to this build. I'm so glad to finally see the light at the end of the tunnel.

I remembered to check the mass and CG today, with pretty much everything for flight loaded. It came out to 21.2 pounds on the bathroom scale, which is a smidge more than what I had in the sims. Fortunately it's not super sensitive to mass and it only lost a few hundred feet. Since all of the extra mass is in the nose, the stability was also improved a bit, with a minimum stability of 3 cals (15% of body length), when my hard limit in the design was 12% of body length.

I'm still doing a lot of finish sanding, trying to correct every possible surface defect, but I'm still on track.
 
Besides, the Pro 75 tailcone has a very sharp taper. I suspect you'd just see instant flow separation and get no significant benefit from it.
Now that I look back at the CTI drawing for the tailcone, I agree, it is a pretty sudden transition from the body tube:
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Good luck on the flight!
 
I'm at the launch site. Did a ground test this evening, with the @tfish style high altitude ejection charge design. 1.5 grams worked perfectly to sever all four shear pins.

I'm not going to fly tomorrow, unfortunately. There are just a few too many small details to finish addressing, and I'd much prefer to do the work when I'm well rested and have plenty of light.
 
Things are coming together for a launch tomorrow morning. The charges and cable cutters are prepped, the tower is adjusted, and the batteries are charging. All that's left is to spend the evening sanding, chasing small defects in the surface finish on the nose and fins.
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I'm hoping to launch at 8 tomorrow morning. Here's hoping that I can get everything together in time. I usually blow right past my intended launch times...
 

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Things are coming together for a launch tomorrow morning. The charges and cable cutters are prepped, the tower is adjusted, and the batteries are charging. All that's left is to spend the evening sanding, chasing small defects in the surface finish on the nose and fins.
View attachment 650637


I'm hoping to launch at 8 tomorrow morning. Here's hoping that I can get everything together in time. I usually blow right past my intended launch times...
Watching from afar - such a cool project. Very best of luck with the flight!
 
End of the burn is max velocity - Sounds like you lost a fin.
The printed fincan wasn't as strong as hoped.
Hope the rest is found so you can know for sure.
Thanks for sharing the build/attempt.
 
End of the burn is max velocity - Sounds like you lost a fin.
The printed fincan wasn't as strong as hoped.
Hope the rest is found so you can know for sure.
Thanks for sharing the build/attempt.
Or maybe not as stiff as required for its moments of inertia.
 
What does the bottom side of the cone look like? It looks like from the pictures there is only 2ish inches of coupler the noes engages on. Is it possible the cone tipped a degree or two to the side under full load and pulled the rocket sideways?
 
End of the burn is max velocity - Sounds like you lost a fin.
The printed fincan wasn't as strong as hoped.
Hope the rest is found so you can know for sure.
Thanks for sharing the build/attempt.
I really hope that the motor case with the electronics turn up and that there is maybe some data to recover.

And I wasn't sure whether or not to post before @Neutronium95 had a chance to reply about the integrity of the fins ... here goes anyway ...

One thing I wondered when I saw Daniel's fin can on the table in Tony's photo was how was the one-poundish fin can attached to the CTI Pro-6GXL motor case ?

I am guessing that there were around 15 -or- 20 G's of deceleration at burnout and that fincan would certainly have wanted to slide forward along the hot, slippery motor case at burnout ...

Anyhow not piling on, just wondering about it ...

-- kjh
 
The motor was still burning when it turned - not a drag related issue.

One of two things make a rocket do a hard turn - loss of fin or loss of the NC.
The short shoulder doesn't add confidence that wasn't the problem, but the condition of the [short] coupler looks OK so I'm not thinking that was the issue here.

No Tracking???
 
The motor was still burning when it turned - not a drag related issue.

One of two things make a rocket do a hard turn - loss of fin or loss of the NC.
The short shoulder doesn't add confidence that wasn't the problem, but the condition of the [short] coupler looks OK so I'm not thinking that was the issue here.

No Tracking???

The coupler, unless I'm looking at his drawing wrong is attached to the airframe in a traditional HED setup. That I'd why I asked about the other side of the cone we cannot see. One heck of a good attemp though.

I agree , tracking on all parts on a attempt like this is almost needed. But I guess if it cored in , the electronics are toast
 
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