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  #1  
Old 06-30-2005, 01:51 AM
Tau Zero's Avatar
Tau Zero Tau Zero is offline
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Join Date: Mar 2005
Location: Twin Falls, Idaho, USA
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Exclamation Estes "Prime Number Explorer" #0891

I picked up this model last year at a hobby shop here in town ("Aero-Tronics Model Supply Co.") where I used to buy plenty of Centuri kits "back in the day" (read "1970's") to contribute the fin patterns to Ye Olde Rocket Plans (YORP), only to discover the patterns were already printed in the instruction sheet posted at JimZ.

I found it odd that this BT-55 kit had a mini-engine mount with a 9" long stuffer tube, and I thought it was an awfully heavy rocket for 13mm engines. So today I finally got my money's worth out of RockSim and worked up the attached files below.

My suspicions were confirmed with "wimpy" 13mm engines, so I just upgraded this kit to an 18mm mount (which I will probably end up using). However, in the spirit of Bill Eichelberger, who seems to have a hankering for engines labled D, E, and up -- I couldn't seem to leave well enough alone, and did a 24mm version, as well.

Here are the general numbers for those of us who don't have RockSim:

Motor -- Max. Alt. (feet) -- Deployment (feet) -- Speed (feet per second)


13mm

A3-4T -- 176 -- 143 -- 41
A10-3T -- 170 -- 165 -- 18


18mm

A8-3 -- 153 -- 150 -- 15
B4-4 -- 365 -- 363 -- 11
B6-4 -- 371 -- 370 -- 6
C6-5 -- 794 -- 791 -- 13


24mm

C11-5 -- 706 -- 705 -- 4
D12-5 -- 1254 -- 1250 -- 21


Cheers,

--Jay

(who discovered the main body tubes for his "Thunder-Awk" and pre-release Semroc "Aphelion" clone were crushed in the post-flood... "rearranging")
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  #2  
Old 06-30-2005, 12:36 PM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by CenturiGuy
I found it odd that this BT-55 kit had a mini-engine mount with a 9" long stuffer tube, and I thought it was an awfully heavy rocket for 13mm engines.

Here are the general numbers for those of us who don't have RockSim:

Motor -- Max. Alt. (feet) -- Deployment (feet) -- Speed (feet per second)


13mm

A3-4T -- 176 -- 143 -- 41
A10-3T -- 170 -- 165 -- 18


18mm

A8-3 -- 153 -- 150 -- 15
B4-4 -- 365 -- 363 -- 11
B6-4 -- 371 -- 370 -- 6
C6-5 -- 794 -- 791 -- 13


Sorry to hear about the damaged models, Jay.

Concerning this model...

I thought it was interesting, nonetheless, to see the performance difference between the A3, the A10, and the A8. You still gotta admit, 170' on a tiny 13mm motor, for a BT-55 body tube, is still a lot of performance! The A10 is the 13mm motor for this brute, notice the deployment V, compared to the A3. The A3 is allowing the model to drop quite a bit before blowing the parachute. The A10 is deploying near apogee.

For the 18mm motor range, the B6-4 is the motor of choice, for the same reason. Deployment V of 6 fps. The C6-5 and D12-5 both get about what I would expect for a model with this tube.

Craig McGraw
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  #3  
Old 06-30-2005, 02:05 PM
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A Fish Named Wallyum A Fish Named Wallyum is offline
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Quote:
Originally Posted by CenturiGuy
I picked up this model last year at a hobby shop here in town ("Aero-Tronics Model Supply Co.") where I used to buy plenty of Centuri kits "back in the day" (read "1970's") to contribute the fin patterns to Ye Olde Rocket Plans (YORP), only to discover the patterns were already printed in the instruction sheet posted at JimZ.

I found it odd that this BT-55 kit had a mini-engine mount with a 9" long stuffer tube, and I thought it was an awfully heavy rocket for 13mm engines. So today I finally got my money's worth out of RockSim and worked up the attached files below.

My suspicions were confirmed with "wimpy" 13mm engines, so I just upgraded this kit to an 18mm mount (which I will probably end up using). However, in the spirit of Bill Eichelberger, who seems to have a hankering for engines labled D, E, and up -- I couldn't seem to leave well enough alone, and did a 24mm version, as well.

Here are the general numbers for those of us who don't have RockSim:

Motor -- Max. Alt. (feet) -- Deployment (feet) -- Speed (feet per second)


13mm

A3-4T -- 176 -- 143 -- 41
A10-3T -- 170 -- 165 -- 18


18mm

A8-3 -- 153 -- 150 -- 15
B4-4 -- 365 -- 363 -- 11
B6-4 -- 371 -- 370 -- 6
C6-5 -- 794 -- 791 -- 13


24mm

C11-5 -- 706 -- 705 -- 4
D12-5 -- 1254 -- 1250 -- 21


Cheers,

--Jay

(who discovered the main body tubes for his "Thunder-Awk" and pre-release Semroc "Aphelion" clone were crushed in the post-flood... "rearranging")


I didn't realize that the PNE was a 13mm powered bird. And I thought the Condor was wimpy!
Still, it's a cool kit to find still on the rack at this point. I saw one on Ebay recently.
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http://wallyum.blogspot.com/

I miss being SAM 0058

On the build floor: Centuri Stellar Hercules, Semroc SLS Scorpion, Semroc Squire, RDC V-Max

Ready to fly: Estes Astron Farside X, Estes Astron Apogee, FRW Marauder XL, FRW Star Jart, Semroc Cherokee D
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  #4  
Old 07-02-2005, 09:59 PM
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EchoVictor EchoVictor is offline
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Location: Metro Detroit, MI
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I was shopping at a couple of hobby stores today in the Milwaukee area, and saw this bird at 2 of them. However, at an asking price of $18 and $20 dollars each, I most definitely passed.

Later,
EV
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  #5  
Old 07-03-2005, 12:56 AM
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Tau Zero Tau Zero is offline
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Location: Twin Falls, Idaho, USA
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Talking YAPMV: "Your Asking Price May Vary"

Quote:
Originally Posted by EchoVictor
I was shopping at a couple of hobby stores today in the Milwaukee area, and saw this bird at 2 of them. However, at an asking price of $18 and $20 dollars each, I most definitely passed.
EV,

That's usually the case with me and any interesting Centuri stuff on eBay.

But I figured I could afford popping $8.55 for this one.


Cheers,

--Jay
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  #6  
Old 07-03-2005, 01:08 AM
Tau Zero's Avatar
Tau Zero Tau Zero is offline
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Join Date: Mar 2005
Location: Twin Falls, Idaho, USA
Posts: 2,034
Thumbs up BT-55 Rockets on 13mm Motors

Quote:
Originally Posted by CPMcGraw
Sorry to hear about the damaged models, Jay.
"Eez okay, Craig." (I'm just thankful my rocketry building supplies were *well* above the waterline.)

Quote:
Concerning this model... I thought it was interesting, nonetheless, to see the performance difference between the A3, the A10, and the A8.
And to be honest, that surprised me as well.

Quote:
You still gotta admit, 170' on a tiny 13mm motor, for a BT-55 body tube, is still a lot of performance! The A10 is the 13mm motor for this brute [snip] deploying near apogee.

For the 18mm motor range, the B6-4 is the motor of choice, for the same reason. Deployment V of 6 fps.
The B6-4 is also just about perfect for my BT-55 1.36X Estes Wolverine upscale, as well, with deployment of 10 fps at an altitude of 313 feet.

http://home.earthlink.net/~gomero/wolverine.html

(heavy sigh) Gotta rebuild that one. Maybe I can finish throwing my Thunder Awk together and paint it for this month's Tripoli Idaho launch.


Cheers,

--Jay
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