Astron Cobra Upscale

I'm not sure if this actually fits in the LPR category but since it's based on a LPW model...... I'm 1/2 way done with an upscale of the old Astron Cobra using BT 80 reduced to a BT 60 sporting a motor mount for 3 - D motors. Has anyone built one on this scale? Pics?

No, but

Gary Byrum said:

I'm not sure if this actually fits in the LPR category but since it's based on a LPW model...... I'm 1/2 way done with an upscale of the old Astron Cobra using BT 80 reduced to a BT 60 sporting a motor mount for 3 - D motors. Has anyone built one on this scale? Pics?

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Well, somebody must have 'cause i found two files for a BT-80 to BT-60 upscale in my decal files.

Both Damon era and pre Damon. So maybe there have been at least 2.:wink:

I don't think it matters if it has been done before, this is still a cool rocket. More pictures please!

I've built the Rocket Pad Mega Cobra but haven't flown it yet. At the next CMASS launch maybe...

https://www.rocketreviews.com/rocket-pad---mega-cobra.html

An upscale project...I like that. Thats exactly what I'm satrting on now. I like my Plasma Probe so much I'm scaling it up for a D engine.

Gary Byrum said:

I'm not sure if this actually fits in the LPR category but since it's based on a LPW model...... I'm 1/2 way done with an upscale of the old Astron Cobra using BT 80 reduced to a BT 60 sporting a motor mount for 3 - D motors. Has anyone built one on this scale? Pics?

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No, but naturally, I have thought about it. Your combination of BT80 and BT60 is pretty close to proportional, but for an even more exact upscale, you could use Semroc BT-58 for the payload section. For a nose cone you would use Semroc BNC-58G4. You would need to create a custom BT-58/BT-80 transition, 3.16" long, though. But that's not hard to do.

This is all hypothetical though. You have gone a step further, have actually built an upscale, and will be flying it soon. This is a very cool idea! I am so looking forward to seeing a launch photo.

What material did you use for the fins, and did you airfoil them as in the original?

MarkII said:

No, but naturally, I have thought about it. Your combination of BT80 and BT60 is pretty close to proportional, but for an even more exact upscale, you could use Semroc BT-58 for the payload section. For a nose cone you would use Semroc BNC-58G4. You would need to create a custom BT-58/BT-80 transition, 3.16" long, though. But that's not hard to do.

What material did you use for the fins, and did you airfoil them as in the original?

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I wasn't going to make a big fuss over a near 1/16" difference in tube sizes and since I already had the tubes and the 60 NA nose cone I knew it would be a rather easy build. It might have been a more important issue with me had it been a scale design like a Nike Hercules or something, but it's only a kit design. I don't think the rocket gods will send me to rocket hell for that. The fins are 3/16" balsa and I opted to just round them off rather than the airfoil. It's just a preference.

I have had one of these sitting in my storage shed unpainted for 3 yearsit is bt 80 to 60 with a 3 x 24 mm motor mount.
I shoud finish it and my upsacle Farside X

jazzviper1 said:

I have had one of these sitting in my storage shed unpainted for 3 yearsit is bt 80 to 60 with a 3 x 24 mm motor mount.
I shoud finish it and my upsacle Farside X

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I'm not much of a kit builder these days but there are some fond memories of some I built and flew when I was way younger. I find myself rebuilding these old models sometimes but I have to scale them up. Farside X huh! I haven't built a staged rocket in years. Maybe I need one on the drawing board (aka my computer )

Gary Byrum said:

Farside X huh! I haven't built a staged rocket in years. Maybe I need one on the drawing board (aka my computer )

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Especially with the new Estes E12-0 hitting the racks.

Fishhead said:

Especially with the new Estes E12-0 hitting the racks.

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Careful....I can feel my horns growing.....

OK! It's near ready for Freedom Launch. Just a few touch ups and it's a go. The Duplicolor paint color made it a little difficult to to decide how to trim this one out but I'm reasonably happy with it. Yall just wish me luck getting 3 D motors to to fire all at once when I take this bish to Orangeburg.

Very nice. I which I could see it fly.

cwbullet said:

Very nice. I which I could see it fly.

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I just hope it doesn't do what my last Cobra did. As a teen I didn't have the skills I do today and my clip whips were.....uh.....not up to speed? 1 motor lit, at apogee apparently some hot debris spewed from the motor and lit another motor, power housing it into the ground. My 1st real core sample. Can't wait to see it fly. Hope it doesn't do a repeat. It was an awesome ground gobbler experience to say the least.

Gary Byrum said:

I just hope it doesn't do what my last Cobra did. As a teen I didn't have the skills I do today and my clip whips were.....uh.....not up to speed? 1 motor lit, at apogee apparently some hot debris spewed from the motor and lit another motor, power housing it into the ground. My 1st real core sample. Can't wait to see it fly. Hope it doesn't do a repeat. It was an awesome ground gobbler experience to say the least.

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Stuff dog barf wadding into the top of each engine. Just in case one or two don't light. Then the ejection charge from the burning engine won't ignite the other motors from the top.

She's a real beauty, ought to be a real pretty sight rising into the air on three BP 24mm. Three F12s would be really cool.

Gary Byrum said:

I wasn't going to make a big fuss over a near 1/16" difference in tube sizes and since I already had the tubes and the 60 NA nose cone I knew it would be a rather easy build. It might have been a more important issue with me had it been a scale design like a Nike Hercules or something, but it's only a kit design. I don't think the rocket gods will send me to rocket hell for that. The fins are 3/16" balsa and I opted to just round them off rather than the airfoil. It's just a preference.

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All valid points. I tend to get a little anal about such things, but that's just me. I wouldn't recommend becoming as obsessive as me when building upscales. It might suck all of the fun out of it.

Gary Byrum said:

OK! It's near ready for Freedom Launch. Just a few touch ups and it's a go. The Duplicolor paint color made it a little difficult to to decide how to trim this one out but I'm reasonably happy with it. Yall just wish me luck getting 3 D motors to to fire all at once when I take this bish to Orangeburg.

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It looks great. The only problem I see is that it is not in the gallery. May I copy it?

Man - I have GOT to build one of those! That is just too cool!

sandman said:

Stuff dog barf wadding into the top of each engine. Just in case one or two don't light. Then the ejection charge from the burning engine won't ignite the other motors from the top.

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Mark,

Gary's childhood Cobra didn't do the "traditional" ignition from the top of the motors. Instead, and inexplicably, as the underpowered model arced over, one of the previously unlit motors suddenly ignited from the NOZZLE end. It subsequently power pranged the model before the first motor fired the ejection charge.

That "flight" was legendary among us young smoke-n-flame enthusiasts. An "APRO Classic"!

JAL3 said:

It looks great. The only problem I see is that it is not in the gallery. May I copy it?

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Thank you for asking and YES. Copy away my friend.

LW Bercini said:

Mark,

Gary's childhood Cobra didn't do the "traditional" ignition from the top of the motors. Instead, and inexplicably, as the underpowered model arced over, one of the previously unlit motors suddenly ignited from the NOZZLE end. It subsequently power pranged the model before the first motor fired the ejection charge.

That "flight" was legendary among us young smoke-n-flame enthusiasts. An "APRO Classic"!

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Well put old friend and it is indeed a memory that has me shakin" in my boots. I been skeert of doing clusters for way too long because of that bit. YOU are gonna make sure I get this one right, eh?

Gary Byrum said:

OK! It's near ready for Freedom Launch. Just a few touch ups and it's a go. The Duplicolor paint color made it a little difficult to to decide how to trim this one out but I'm reasonably happy with it. Yall just wish me luck getting 3 D motors to to fire all at once when I take this bish to Orangeburg.

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Use flashpan ignition. Someone on the field will have some BP they will assist you with to get them all lit.

Gary Byrum said:

YOU are gonna make sure I get this one right, eh?

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I'm here for ya, little buddy.

Rocketlady said:

Use flashpan ignition. Someone on the field will have some BP they will assist you with to get them all lit.

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Thanks Kathy. My problem with the earlier model was probably due to the haphazard whip clips I made with inadequate power to boot. I have better skills these days and I expect my whips are far more efficient this time around. I prolly could bring my own homemade BP but I don't think that'll be necessary.

LW Bercini said:

I'm here for ya, little buddy.

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You makin' fun of my height Mr. 3 times taller than me? How's the air up there? Watch out for low flying planes! You could be a candidate for picking rockets outta trees that eat them....LMFAO!

LW Bercini said:

Mark,

Gary's childhood Cobra didn't do the "traditional" ignition from the top of the motors...

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"Mark?" You mean "Gordy" (aka Sandman), right?

I have successfully launched my Cobra using both Quest Q2G2 and Estes Solar igniters using the twisted leads method. The important thing is to make sure that all three leads are well incorporated into each twisted pigtail so that they all have good contact, and then once you have done that, to make sure that all three igniters are still well-seated in their respective nozzles and are touching propellant.

As an aside, here is a summary of my experiences using Estes and Quest igniters and plugs in each other's motors:

Estes igniters and plugs in Estes motors: The plugs hold the igniters in place very solidly, so it is difficult to accidentally pull them loose while you are twisting the leads. (Always recheck to verify, though.)
Quest's original Q2 igniters (now OOP) and Tiger Tacks (plugs) in Quest motors: Also held in well and difficult to pull out accidentally.
Quest Q2G2 igniters and tube "plugs" in Quest motors: You have to be a little bit more careful and handle things a bit more gently because the tubes don't hold the igniters in quite as solidly as plugs would do.
Quest Q2G2 igniters and tube "plugs" in Estes motors: Due to differences in nozzles sizes between the two brands, you may have a hard time using the tubes to keep Q2G2 igniters in place in some Estes motors, such as the B6. (They seem to work in Estes C6 motor nozzles, though.)
Quest Q2G2 igniter and Estes igniter plug in an Estes motor: Won't work -- the correct plug (or any other Estes plug for that matter) will not fit in an Estes nozzle when a Quest igniter (Q2G2) is installed. (Use a ball of paper wadding instead and cover with tape.)

MarkII said:

All valid points. I tend to get a little anal about such things, but that's just me. I wouldn't recommend becoming as obsessive as me when building upscales. It might suck all of the fun out of it.

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Mark,

I usually go thru the exercises like you did, but when the rubber meets the road, when push comes to shove, and I finally build it, I tend to make lots of tradeoffs in the interest of practicality. Don't get me wrong, I've made and/or ordered my share of custom and odd-sized parts, but I've found more often than not that it still looks about right when I make those tradeoffs

I think it's good you go thru the exercise of trying to make it exact scale - it's a good engineering exercise. The next step then is to punch in the numbers for available parts and then see how close to scale you can get. That 1/16" difference tends to not be so noticeable.

Doug

.

plano-doug said:

Mark,

I usually go thru the exercises like you did, but when the rubber meets the road, when push comes to shove, and I finally build it, I tend to make lots of tradeoffs in the interest of practicality. Don't get me wrong, I've made and/or ordered my share of custom and odd-sized parts, but I've found more often than not that it still looks about right when I make those tradeoffs

I think it's good you go thru the exercise of trying to make it exact scale - it's a good engineering exercise. The next step then is to punch in the numbers for available parts and then see how close to scale you can get. That 1/16" difference tends to not be so noticeable.

Doug

.

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Quite right. That's essentially what I am saying in the post you quoted. (You could summarized it as, "This is what I do, but don't become like me and obsess over every dimension if you want to actually enjoy the hobby.")