4 inch Polecat Goblin Replica - Build Thread

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DabCat

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I have 2 videos of it. The video file attached is the video I recorded. My video follows my rocket. The YouTube link is @UPscaler 's video. He has a better video of all the Goblins.

- 19:07
 

DabCat

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I believe the original is the same length as mine. It just has a slightly different shape nose cone.
 

hobie1dog

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I was wondering about contacting mad cow to see if they would have the nose cones that were used on the polecat goblin.
 

DabCat

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Madcow might have some. If you can get a hold of the new polecat team, they probably have some...
 

hobie1dog

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the original nose cone looks pretty similar to the one that I have on my Apogee components level 2 kit, Which was made by Mad Cow for them. When you look at the level two kit from Apogee, It is a four inch fiberglass kit with 4 fins and the fins on it look almost exactly Like the Goblin fins from polecat
 

DabCat

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The madcow fiberglass nose cones I have use much thicker fiberglass cloth than the polecat ones.
 

DabCat

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Sorry, responded too quickly. It does look pretty simular to the Goblin. I'll bet madcow parts would work pretty well.
 

hobie1dog

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Sorry, responded too quickly. It does look pretty similar to the Goblin. I'll bet madcow parts would work pretty well.
Well, I have the 4" fiberglass bottom section of the Apogee/Madcow Level 2 kit and fins, as they replaced the off centered fin slots section and the fins which were different lengths. I could get another MM tube and centering rings, cut down the tube, and just need to find a nose cone like Polecat used originally and come really close to the fiberglass version of the original kit. That's going to be my initial plan, or make new fins and use the bottom section for making a Public Enemy Fat Boy (the orange one), or a combination of the two which would be the easiest by using the Nike Smoke style fins that came with the Level 2 kit and make it a little longer than the Polecat Goblin so that there's almost no modifications needing to be done to the bottom section I already have. The bottom section I have looks almost exactly like the Fat Boy bottom tube.
 
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kramer714

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IMG_20211106_173811.png
IMG_20211026_201046.png


The "Goblin Event" was fun up at Lucene. I ended up scratch building a 3" and 4" goblin, plus had a stock Madcow Lil-goblin and a OG Polecat 5.5 inch one. There were 17 Goblins launched. Fun!
 

kramer714

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June 2022 ROCstock... Goblin Event Deux! Yes...?

BTW anyone have the group shot?
 

hobie1dog

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View attachment 492424 View attachment 492425

The "Goblin Event" was fun up at Lucene. I ended up scratch building a 3" and 4" goblin, plus had a stock Madcow Lil-goblin and a OG Polecat 5.5 inch one. There were 17 Goblins launched. Fun!
Thanks for taking that picture of all 4 sizes for us, I appreciate it.
1. How long was your body tube on the 4-in model?
2. Also where did you the nose cone for it?
3. On the 2.6 "model, what is the smallest single-use motor it will fly on?
 
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kramer714

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The 3" and 4 " are scratch built fibergoblins, all fiberglass with a really short av bay for dual deploy. The 5.5 is a stock Polecat, and the 2.6 is a madcow Lil-goblin
1) the body tube on my 4" is 16" The 'real goblin was 14.5 - 15" depending on how they cut it.
2) Composite Warehouse 3/1 ogive
3) it is pretty light, would be fine on an F, could get away with a high average thrust E I bet. having said that a G or H is more fun, just saying....

What difference is there between my scratch built and the 'original goblins?

a) same fin planform, really close to the Madcow Nike - same as the old polecat Nike and Goblin.
b) fiberglass fins - 1/8 thick G-10 - this is thicker than the typical fiberglass kit fins for a rocket this size. The 4" 'kit' I made for my kid has resin transfer molded graphite fins. The original goblin had plywood fins. Fins were cut using a hand router and a 3d printed fin jig.
c) fiberglass body tube - standard wall not thin wall - bullet proof, stretched slightly to fit a 54-1706 case in the 4" with the dual deploy I wanted to make it K2050 capable....
d) filament wound fiberglass nosecone 3/1 ogive (standard wall)
e) Optional Dual Deploy, Goblins are fun, Goblins with really large motors in them are really fun, walking / driving to recover small rocket far away not so fun.....
I made a really short av bay with a 1" switch band, the avbay sits entirely over the bodytube and extend less than 1 inch into the nose for head end main chute. I made a side mount for the shock cord that doent use an eye-bolt or U-bolt. I wanted to let the motor come all the way up to the bulkhead, no room for an eye bolt or u bolt in the middle. Holds a single RRC2 and a screw switch.
 

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hobie1dog

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Thanks so much for all of that information, Well those last pictures are some serious rocket building, You are the man
 

hobie1dog

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The 2.6" Lil' Goblin kit has this listing:
Recommended Motors:
Single Use
F25W-6 1400 ft
F26FJ-6 1230’
F50T-6 1320’
G40W-7 1770’

RMS
E16W-4 690 ft
E23T-5 645'
F40W-7 1470
what are my other single use engines to keep the altitudes in the sub-1000 ft range? I don't want to do reloadable motors in the E range.
 
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