I couldn't throw away the tube...

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Elapid

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that came with the AT Initiator starter kit, so i bought a hunk of balsa wood and carved a nose cone. the MMT is made from some heavy-walled tubing that fits a 38mm casing easily...actually, i'll want to use a bit of tape to snug things up a little. better to have it a little loose than too tight tho!

it's a shame to cover the NC with paint...
:(

fins are from a sandhawk that never materialized...maybe i can get another Initiator kit (spare parts are always good) or two and make it into one...

:D

here's the bits and pieces
 

Fore Check

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How long is the tube? How long is the nose cone (not including the shoulder?)

You might have the makings for a 38mm Goblin upscale here, if you were willing to cut different fins.... The nose cone looks like a pretty darn close approximation for a Goblin..........
 

Elapid

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that's a great idea!
it's not like i'm that far in...

NC is 11 7/8" total length, shoulder is 1 1/4"
Tube is 25 1/4"
 

sandman

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Actually the nose cone is closer to the shape of a BNC-50X

Astron Constellation/Astron Sprint cone.

Good job!

sandman
 

Elapid

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might be better for a Der Red Max 1.8x upscale since it uses a parabolic NC

DRM is too short...

sprint is an old fave'
i have an E-powered upscale, i guess a normal sized and a big one to round out the group...

i like the goblin idea best...
maybe i'll get out the 80-grit and take the cone down a tad...put a point on it...i can see it...
hmmm...

decisions, decisions...
 

Fore Check

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Well, don't put a point on it yet - the BNC55AO (Goblin cone) is rounded - I'd call it "Elliptical" in RSim.

Anyway, it's 5" long and 1.325" diameter, which gives it an aspect ratio of 3.77:1

Not knowing the diameter of your tube, you could go with that ratio (3.77 x tube diameter) for the cone length (above the shoulder)

Now for the tube length. In the original or clone, the nose cone (as stated above) is 5" long. The body tube is 9". Which means the tube is 1.8 x the length of the cone.

If you bother trimming your cone (if necessary) to acheive a true upscale, you could trim your tube to 1.8x the length of your trimmed cone.


For the fins, well - you'd have to ratio the diameter of your tube against 1.325 to know the upscale factor for your fin templates.



Sandman is correct - it is pretty close to an upscaled 50x cone too. He *is* the expert, after all... :p
 

Elapid

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i thought i remembered the goblin having an elliptical nc...
the rsim files show pointy...

the body tube is 3.0" od, so the nc should be 11.32" if i calculated properly, and the body tube should be 20.4"
 

Fore Check

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That's good news on the cone! By my math, a true upscaled 55AO would be 11.31" above the shoulder then, which is only 1/2" less than what you have. It would take a keen eye and probably a ruler to ever notice if you left it as-is!

You would have to trim your tube to be about 20 3/8" long, though.

A 3" tube would give you a 226% upscale on the fins.



Must..... build.... Goblins...... :kill:
 

Fore Check

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BTW: if you decide to go with the Goblin, and aren't in to making your own decals, send a PM to Astronboy. He does *great* work, and I highly recommend him.
 

Fore Check

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I should also note that while the 55AO cone is rounded, it isn't *as* rounded or "fat" at the tip as the 50x cone. As Sandman noted by stating the resemblance, the 50x cone leans more to being "fatter" at the tip than the AO does. You could sand it down some, but don't put a point on the tip.

Heck, if it sounds like trouble to modify it, I'd leave it alone.
 

Elapid

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I'm SOLD
:D

i have finished filling in the spiral and the dents in the nc from where i dropped it...last coats of sanding sealer have been applied. i'm thinking of sanding down the shoulder abit and putting on a wrap or two of 'glass for durability, and probably a 1/8" aircraft plywood bulkhead glued to the base to boot!

due to the weight of the finished rocket, i'll drill a 1/2" core out of the NC and put in a couple oz of lead and seal it in with a section of 1/2" hardwood dowel, which will give a nice place to attatch a screw eye...

sound ok so far?

i like to wing it when i build these things...
i'm going to use this bad baby for my L1 Cert flight!
fitting that it is a scratch-built!
 

jetra2

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I think it would be unneccessary to do all those modifications to the nose cone. Instead of wrapping the shoulder in a layer of 'glass, just leave it as is. If you're concerned with the strength of it, soak it in CyA or something, then sand it down. That'll strengthen it without adding thickness that you would probably have to sand down. Think about it. When you sand your fiberglass, what happens to that epoxy that strengthens the glass? Right! It goes away, and you lose your strength! (Thanks to daveyfire for this tip)

For nose weight, I would drill out the 1/2 hole as far as you feel necessary, fill it with BB's, cover those in epoxy, and then insert a 1/2" or 7/16" dowel to plug it, then cover the base of the nosecone with a layer of fiberglass. When Eugene (eugenefl) and myself were building the Tour de Deuce's, we used a similar method, but did not add noseweight.

I hope this helps!

GOBLINS ARE KING! :) :) :D

Jason
 

Elapid

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for safety (structural integrity), any day of the week.

the epoxy in a fiberglass/composite laminate really only holds together the glass/carbon fibers, as long as you don't sand through the glass/carbon fibers themselves, strength is not compromised.

thanks for the info!
 

Fore Check

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NOW yer talkin'!

You can see by comparing the nose cone in your build pic and the one you posted of the yellow/white clone that the original/actual cone is rounded at the tip, just not as "fat" at the top. But yours looks close enough to me!
 

Elapid

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that's an original, ca. 1970

here's another



here's MINE
:D

 
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