Fisher Research K3800

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I will post some pictures and video when I can (tomorrow or Monday) but I am away from home posting from my phone. Short story, it flew great. Three small bits of blue/violet-burning grains did get ejected (no surprise to us) but it just added to the visual appeal of the flight :)

The altitude was right around 800' (G-wiz said 789', RRC3 #1 said 799', and RRC3 #2 said 811'). The booster landed upright, true to its Falcon-9 heritage (the BT was formed on the mandrel used to build the leg-tips) and everything was recovered with barely a scratch.

As Mike and I walked out to pick up the rocket a couple hundred feet from the pad we both agreed that this thing screams for an M!
 
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Word up. Binder worked his magic. Give him the reins and send that bird up next on a big M. Obviously he knows his $h!t. That thing is a beast. Work it Binder, make next months' burn epic. Blast that thing into the tropo.

Congrats to all and Binder. Your student class has an exceptional teacher/s. Kids these days are seriously devoid of all practical hands-on real life experience. You have provided a great service to them. Wouldn't be surprised if one or more of them ends up working for Elon. This is exactly what this country/society needs.

Mad props.
 
Well it certainly wasn't even half as fast as I had anticipated, but it only ejected a few chunks right at the end, so we'll call it good. It was a weird motor I've always wanted to try. As best I can ascertain, the burn was slowed by keeping the grains tight together with no free play. I had to put a lot of pressure on the forward bulkhead to compress the grains a bit to get the snap ring in. I did that deliberately to keep the grains from eroding as much. As such, I think the "as fired" kn was really low on this thing.

It was a very pretty flight with special effects at the top. I probably won't be making any more of these short grain motors in the future. For performance I think we may have been better off with one of my 38mm K's and a motor adapter. It really underperformed in the altitude department. But with the square airfoil on the fins and the huge frontal area, that's not real surprising.

It was a neat test, but we really need to put an M in it. After seeing how well it was built, I have full confidence in it.
 
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As an observation, Dan is a great teacher. We should have more like him. Seeing how well his students interacted with him was inspiring. Congrats to the Silver Crest Rocket Club on such a great project and flight!
 
Happy to hear it went well!
Thank you!

Thanks, it really was.

Word up. Binder worked his magic. Give him the reins and send that bird up next on a big M. Obviously he knows his $h!t. That thing is a beast. Work it Binder, make next months' burn epic. Blast that thing into the tropo.

Congrats to all and Binder. Your student class has an exceptional teacher/s. Kids these days are seriously devoid of all practical hands-on real life experience. You have provided a great service to them. Wouldn't be surprised if one or more of them ends up working for Elon. This is exactly what this country/society needs.

Mad props.
Thank you for your kind words. We had a great team of girls, some great donors, and an incredibly skilled craftsman that built our motor.

"This is going to be cool or it's going to be REALLY cool."
And it was!

As an observation, Dan is a great teacher. We should have more like him. Seeing how well his students interacted with him was inspiring. Congrats to the Silver Crest Rocket Club on such a great project and flight!
Thanks, Mike. It has been an awesome experience for all involved. I'm glad you convinced me to do this. Okay, it might not have taken much convincing, but thanks for the crazy offer last summer that tarted the craziness!
 
98/1G would be a fun East Coast motor! Well done.

edit: gotta love when JUST your motor's mass fraction is 42%. Those 98 cases are thick, and those nozzles and bulkheads are heavy!
 
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edit: gotta love when JUST your motor's mass fraction is 42%. Those 98 cases are thick, and those nozzles and bulkheads are heavy!

Thanks for noticing!

I used about 1/2" thick pancake bulkhead with single o-ring. Nozzle was a bit short to keep the weight down, so underexpanded. Tried to keep it as light as possible. Looks like the bulk of the burn was about .75 seconds, but it had quite a bit of tail off. It did have plenty of initial thrust. I think the tail off and spit grain chunks was caused by my liberal coating of grease on the nozzle and bulkhead must have inhibited the top and bottom grain.

I disassembled the motor, liner looks almost unused and there were three casting tube rings still inside. I didn't glue anything in, just wanted to see what it would do and didn't want to take a chance of accidentally inhibiting the grain faces. So careful application of glue would probably be a good idea if I ever try it again.

It looks pretty wimpy in the video because of the sheer size of this Dragonfly, but I think this motor would be really cool in a minimum diameter short kit like a Jackhammer. I might give that a shot someday.

The only video posted so far is on Facebook.
 
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Not to distract from this thread, but here's another flight with one of your 98mm cases:

Cool, thanks for sharing! I've moved the Dragonfly vid to youtube.
[video=youtube;jT22zmQCE4s]https://www.youtube.com/watch?v=jT22zmQCE4s&feature=youtu.be[/video]
 
If I try this again, I'll go with matching grain thickness and web thickness, leave 1/2" slop in the stack for full propagation, and a more conservative throat to port ratio. Ideally it will be instant on/instant off. This first one was a bit sloppy but the main thing is it didn't destroy a nice rocket. :)

Jackhammer motor.jpg
 
There was an accelerometer onboard, right? Let's see that thrust curve...

I'm inspired enough that I intend to make up a 76-1G motor this week. Logical geometry is a pair of half grains, each 2.5" long. Assuming I can get it to burn fast enough, it's essentially the perfect motor for 4" FG or Canvas rockets at small East Coast fields.
 
Dan - you are exactly the kind of teacher that we need!

Mike - you are exactly the kind of enabler that was needed for this to happen!

To both of you, and all involved in this project - major Kudos!
 
I need to find the G-wiz software, probably should be available somewhere online.

There was an accelerometer onboard, right? Let's see that thrust curve...

I'm inspired enough that I intend to make up a 76-1G motor this week. Logical geometry is a pair of half grains, each 2.5" long. Assuming I can get it to burn fast enough, it's essentially the perfect motor for 4" FG or Canvas rockets at small East Coast fields.
 
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