Scratch Build - Excalibur Artillery Round

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mccordmw

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Been thinking about this for a while. I love building military replicas from scratch. I've mostly stuck to slow liftoffs, because I love watching them fly.
Now, I'm thinking of a 1:1 replica of the guided 155 mm Excalibur Artillery she'll. Since it's a replica, I fell I need to be as close to a shell launch as possible. Therefore, I'd build this for Vmax motors. The shell needs to take off as quickly as possible.
When I get home, I'll post up the ork files and diagram. Should be fun.
 
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How did you draw up your .ork file?
Do you have dimensional drawings?
I downloaded some pics a few months ago but couldn't find dimensional drawings.
Was going to use Eyesim (and a ruler). ;)
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For those not familiar with it the M982 Excalibur is a GPS guided extended range artillery shell. The extended range comes from fold out glide fins.
Looking forward to seeing your build.
 

Sandy H.

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Make it tube-launched with spring out canards!

Does anybody use a sabot when doing tube launches? I know they can be a valid method to solve other round vs odd-shape issues, but I don't know that I have ever seen that at a launch. I recall piston launchers and other odd launch methods, but I can't say I've seen a sabot. . . seems like with modern 3D printing options, it would be pretty trivial and act a bit like a piston launcher for performance as well if designed correctly.

Sandy.
 

Sooner Boomer

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A sabot typically goes *around* a projectile. I've used what I call "slippers" that fit around a fin, and go down the length of the rocket.

 

amiles

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Does anybody use a sabot when doing tube launches? I know they can be a valid method to solve other round vs odd-shape issues, but I don't know that I have ever seen that at a launch. I recall piston launchers and other odd launch methods, but I can't say I've seen a sabot. . . seems like with modern 3D printing options, it would be pretty trivial and act a bit like a piston launcher for performance as well if designed correctly.

Sandy.
I have used sabots with two tube-launched high power rockets. The white Minuteman II used a single set of foam sabots and was launched from a 12"-diameter sono tube. The green/black/yellow SS-25 used two sets of sabots made from 3D-printed mounts and sono tube sleeve segments, and was launched from a 10"-diameter PVC tube.
 

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mccordmw

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I think I'll skip launching from a tube or using a sabot since this is a pretty potent Vmax engine. I'd rather not blast any debris around. Anyway, here's the ork file and imagery. This needs a significant amount of nose weight to be safely stable. I also shrunk the fore canards by 1" to help with stability.

I'm targeting a 98mm L3150 vMax for this. The tube is going to be a pretty tight pack to fit the chute and recovery hardware. I have chute bags that I might use to protect the chute from the deployment blast. For dual deploy, I'll probably go with a JLCR to save on the space needed if I had a drogue plus main.

Flight parameters:
Velocity off the rod: 22.7 m/s (51 mph)
Max velocity: 316 m/s (707 mph, mach 0.9)
Max acceleration: 249 m/s2 (25.4 G)
Apogee: 2143 m (7,030 ft)

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BigMacDaddy

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Before I saw that big honkin' motor you were putting in there, I was thinking that there might be a way to use GDS to stabilize this model -- recess engine, leave holes around fins (for air intake), mount fins to inner body tube (depending on design). May not be necessary given the stability you are showing and might not even work with that huge engine but might be relevant for a smaller engine or something.

EDIT: Thinking of something like this (again likely not relevant for your larger version but maybe for a BT-80 version or something (this is mocked up BT-80 w/ 24mm E engine) --

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mccordmw

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Now the question... Do I roll my own fiberglass? Do I fiberglass a 6 inch cardboard tube like I did with my 8 inch PAC3 Patriot? Or do I buy any inch fiberglass tube from a commercial source?
 

BigMacDaddy

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I like the find in the second version, but it's moving the center of pressure more foreward. I'd need to add a ridiculous amount of nose weight. It's already kind of ridiculous.

You may want to simulate the two fin options -- I thought the same at first glance but the 1b are distributed backwards a bit and are a bit taller so it may be a trade-off. Anyway, either way it will be cool but thought I would share. Your thread inspired me to build my own w/ a BT80 tube and 24mm motor recessed some to try to get some GDS benefits (and CG shift forward).
 

mccordmw

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You may want to simulate the two fin options -- I thought the same at first glance but the 1b are distributed backwards a bit and are a bit taller so it may be a trade-off. Anyway, either way it will be cool but thought I would share. Your thread inspired me to build my own w/ a BT80 tube and 24mm motor recessed some to try to get some GDS benefits (and CG shift forward).

You going to go for a short burst, punchy motor?
 

teepot

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I did a tube launch and used foam sabots. Worked ok. I launched a rocket that looked like a 60mm mortar round out of a tube that was just a little bit larger that the rocket. I have seen a couple of pictures of a guy that used flexible wire whiskers. 4 whiskers closer to the front than the back. Might have been in Sport Rocketry.
 

StreuB1

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Now the question... Do I roll my own fiberglass? Do I fiberglass a 6 inch cardboard tube like I did with my 8 inch PAC3 Patriot? Or do I buy any inch fiberglass tube from a commercial source?

155mm = 6.1"

Wildman 6" airframe is 6-3/16" OD.

Damn near dead on. I would go that route.

Have you thought about the L2500 super thunder for the 98/5120 case? ST propellant is about as close as you will come to Warp9 for a big motor. Unless you want to run the K1999 Warp9 for the 98/2560 case...... Both have significant punch.
 

Neutron95

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I thought I could get a hold of one, but no luck. I'm looking at some Warp9 alternatives or some fast burn Aerotechs running two motors.
Aerotech Super Thunder is pretty similar to Vmax in terms of performance. The M4500 or M6000 would probably be a good fit for what you want.
 

mrwalsh85

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I thought I could get a hold of one, but no luck. I'm looking at some Warp9 alternatives or some fast burn Aerotechs running two motors.

Loki M3464... Yeahhhh.

Then there is the AT Super Thunder formula.

Are you still around STL?
 

mccordmw

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Loki M3464... Yeahhhh.

Then there is the AT Super Thunder formula.

Are you still around STL?

Been looking at the Super Thunder engines. They might fit the bill. I usually check Loki first since I like to support him. I didn't see any L to M motors that are short enough to fit in my airframe or had sub second punchy thrust.

Yup! Still in the stl area. Been stupidly busy as a director at Merck with this covid pandemic.
 

mccordmw

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155mm = 6.1"

Wildman 6" airframe is 6-3/16" OD.

Damn near dead on. I would go that route.

Have you thought about the L2500 super thunder for the 98/5120 case? ST propellant is about as close as you will come to Warp9 for a big motor. Unless you want to run the K1999 Warp9 for the 98/2560 case...... Both have significant punch.

Yep. Looking at composites warehouse. They have 6" fiberglass and a 4:1 nose that are nice. Leaning that route, but I do love the challenge of fully scratch building.
 

mrwalsh85

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Been looking at the Super Thunder engines. They might fit the bill. I usually check Loki first since I like to support him. I didn't see any L to M motors that are short enough to fit in my airframe or had sub second punchy thrust.

Yup! Still in the stl area. Been stupidly busy as a director at Merck with this covid pandemic.

Gotcha. Should join us sometime. We had a -really- nice launch in November. I flew my Screech on a K2050ST and broke the 3d printed tracker bay... AGAIN. I need to mount the tracker, period. Oh well. The WAC Corporal landed in the middle of a 75 foot clearing between the creek and a flooded duck blind. YIKES.

We're hoping to reinvigorate the launch environment. The November launch had about 40 vehicles at one point per the landowner!
 

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