Cobra 1500

[Mopower71]

I ordered all the parts to start this project yesterday.

Before I get started I have a few questions, and recommendations.

The Cobra is three 18" BT55 tubes, should I have a friction fit center with a chute for each piece, or do it like the original and have one chute out the top?
If splitting in the middle, at which joint?
What size parachutes?

I probably should build a baffle for this. Where in the body tube should it be?
What type to build. one with offset holes, half moon alternating pieces, Or?

[Mopower71]

This is the plans for the Cobra 1500 (http://www.oldrocketplans.com/estes/est1294/est1294.htm)

I had one as a kid, and never launched it, tore it apart and made other rockets from it.

[sandman]

I ordered all the parts to start this project yesterday.

Before I get started I have a few questions, and recommendations.

The Cobra is three 18" BT55 tubes, should I have a friction fit center with a chute for each piece, or do it like the original and have one chute out the top?
If splitting in the middle, at which joint?
What size parachutes?

I probably should build a baffle for this. Where in the body tube should it be?
What type to build. one with offset holes, half moon alternating pieces, Or?

Put the baffle at the lowest BT-55 joint (BTW SEMROC has the baffles) and have it separate at the second joint.

Make the upper section a payload bay to separate it with a solid coupler. (SEMROC has those too!)

Oh, yea, I have the decals. ;)

So, really, you don't have ALL of the parts. :rolleyes:

[tbzep]

I ordered all the parts to start this project yesterday.

Before I get started I have a few questions, and recommendations.

The Cobra is three 18" BT55 tubes, should I have a friction fit center with a chute for each piece, or do it like the original and have one chute out the top?
If splitting in the middle, at which joint?
What size parachutes?

I probably should build a baffle for this. Where in the body tube should it be?
What type to build. one with offset holes, half moon alternating pieces, Or?

It will be easier to transport if it separates in the middle.

The original recovered with a single 18" chute. Splitting in the middle will let you recover with a 12" on each section. SEMROC and Fliskits have 16" chutes that would work good with fairly large spill holes.

Half moon baffles work just fine and are easy to make yourself, especially with the extra 18" over the top. Some folks have scorching issues, but I never have. Just make the plates a little larger than 1/2 way across. Build it into the coupler of the lower section. The SEMROC type can't be used as a tube coupler, so you would still need a tube coupler to connect the body tubes.

[Mopower71]

Will there be enough umph in the ejection charge to blow the chutes out on such a long rocket?

[tbzep]

Will there be enough umph in the ejection charge to blow the chutes out on such a long rocket?
Yes, it's always worked on mine. However, if you modify it to separate in the middle, it will only be filling 1/2 the volume.

[chrism]

This is a rocket that my brother built way back in the late 70s when we were teens. I am thinking about cloning this one as you pointed out Semroc does have all the parts. I was thinking of putting a "D" engine mount in it as the 18 mm engines seems a bit weak. Custom Rocketry Equinox is a similar rocket and uses a D engine mount.

[Mopower71]

Thanks for the info guys.
I am impatiently waiting for the mail to arrive.
want to put the three tunes together and nose come and see how tall it is.
What launch rod would you use?

[mwtoelle]

A regular 1/8" rod works just fine. However, you might need to weight or stake down the launch pad if there is much wind. It flies best on B6-4s and C6-5s. I have not tried my Cobra 1500 of an Aerotech D yet.

[mwtoelle]

This is a rocket that my brother built way back in the late 70s when we were teens. I am thinking about cloning this one as you pointed out Semroc does have all the parts. I was thinking of putting a "D" engine mount in it as the 18 mm engines seems a bit weak. Custom Rocketry Equinox is a similar rocket and uses a D engine mount.

The Custom Rocketry Equinox is Custom's version of the Estes Mean Machine. The OOP Custom Engage was their answer to the Cobra 1500. The Engage also used an 18mm motor mount. I never bought an Engage, but I believe that its flight characteristics would be similar to the Cobra 1500. There are reviews of both the Engage and Equinox on http://www.rocketreviews.com

[tbzep]

Thanks for the info guys.
I am impatiently waiting for the mail to arrive.
want to put the three tunes together and nose come and see how tall it is.
What launch rod would you use?
A 1/8" steel rod is good enough for fairly calm weather. I'd move up to 3/16" if your 1/8" rod is aluminum. I'd definitely move up if you fly in breezy conditions.

[chrism]

The Custom Rocketry Equinox is Custom's version of the Estes Mean Machine. The OOP Custom Engage was their answer to the Cobra 1500. The Engage also used an 18mm motor mount. I never bought an Engage, but I believe that its flight characteristics would be similar to the Cobra 1500. There are reviews of both the Engage and Equinox on http://www.rocketreviews.com


Thanks for the info, I forgot what their other tall rocket was called.

[Mopower71]

Woo Hoo. My Rocket showed up today. Well, ok, the parts to recreate it.
Everything came in one very well packed box from Semroc.

Also my Kevlar cord showed up today from Brs.
Now to find time to do some Rocketry..

Today was out as I had to change the starter on my truck. and tomorrow I have to drop off kitchen cabinets and cut grass.

I did put together the three tubes. going to be interesting to launch. I am not sure what size the standard rod is on the launch pad, but I am sure I will have to find something longer.

To those that launch these, is it a slower take off like a Big Bertha?

[ghrocketman]

Make the motor mount a MINIMUM of 24mm if not 29mm like I did for mine.
18mm engines are too weak for a 5' BT55 rocket unless one wants to fly it exclusively on Aerotech D10/D21/D24 18mm engines.
With the 24mm mount one can fly it fairly low on C11's and can also punch it way up there on a F24 or F39 reload.

[Earl]

Make the motor mount a MINIMUM of 24mm if not 29mm like I did for mine.
18mm engines are too weak for a 5' BT55 rocket unless one wants to fly it exclusively on Aerotech D10/D21/D24 18mm engines.
With the 24mm mount one can fly it fairly low on C11's and can also punch it way up there on a F24 or F39 reload.

His field size and personal aspirations for this rocket may not match up with or warrant that recommended mount size.

[sandman]

with a 24mm motor mount you can always adapt down to 18mm or use a C11.

29mm may be a bit much for the airframe.

Too late now but you could have gone with the heavy duty series 125 body tubes used for the SLS kits. They are twice as thick but a bit bigger than a BT-55 (1.325" O.D.). They actually match the BT-56 (1.34" O.D.)

I'm just saying. :rolleyes:

[ghrocketman]

I actually used to fly mine on FSI F100's with no problems....then again they were really only F70's with 50 nsec. Same total impulse as a 24mm F39 with more kick. It was eventually destroyed on the 5th or so F100 flight by the infamous F100 cato.
The Cobra 1500 only hits like 325' on a C motor and maybe something like 800' on a D12.
I flew mine once on a B6-4 in an adapter just to see what would happen;
got to maybe 125' and the chute opened MAYBE 40' above the ground. A B6-2 would be more sensible if one likes lackluster flights to pump-up water-rocket heights.

[Mopower71]

What parts are required to make the 24mm mount, and a 24mm to 18mm adapter?

[sandman]

What parts are required to make the 24mm mount, and a 24mm to 18mm adapter?

You will need a length of BT-50 body tube (3 or 4". More if you want it longer), BT-55 to BT-50 centering rings, 24mm motor block if you are just staying with BP motors and a longer engine hook if you want to use the BP E's plus and spacer so you can use the shorter "D's".

You can clean out an old "D" motor and an 18mm motor will fit inside. That's your adapter.

I can list the parts if you want.

[Mopower71]

Why put the BT50 inside the BT55? I saw at the LHS a D engine mount the would work with a BT55 but I didn't get it, as I didn't know how to adapt the B/C engines to the D size.

[ghrocketman]

The BT50 is the size of tube that holds 24mm D/E (and small F reloads in the RMS24 case)size engines, hence the need for the BT50 mounted in the BT55. Make the mount 4" long so one can use the Estes E engines as well which are 1" longer than the Estes D's, Aerotech E's and the RMS 24 D/E/F reload case.
The Cobra 1500 is one example of few rockets that fly really well on an Estes E9-6 engine.
To be safe, I added 2 oz of clay in the nose of mine, but it flew on the really heavy FSI F100 engines. Tried it once on the 9sec burn FSI F7 engine and got a major land-shark. Those engines were a total joke. Many skyrocket motors had more thrust.
With engines up to the weight of an Estes E9 in the tail, there is no need for noseweight; the E9 weighs more than any of the reloads in the RMS24 case including the F24 and F39. If you intend on using the F39, I would at least fillet the fins with epoxy. Some will say this is overkill, but better safe than sorry.

[Mopower71]

The fins are mounted and it is time to do some filling and sanding and filleting.
Comparison photo of Cobra 1500 and the Guardian.

[ghrocketman]

Please tell me you used a motor mount larger than the IDIOTIC 18mm mount Estes supplied in the stock kit.

[Mopower71]

I haven' t put a engine mount in it yet.

[ghrocketman]

Go 24mm; you won't be sorry.

[Mopower71]

The Upper body tubes are assembled, primered and two coats of white paint have been applied. I sanded down the original nose cone, cleaning up the mess of years of being in the box. It is now painted and looks good. just want to give the paint time to dry before clear coating the pieces.
The lower section I have been using the Aero Gloss on the fins, I put two coats on the fins and when I sanded them, it appears to have just removed all the Aero gloss. I was using 400 grit paper on a block. So I stirred the jar up good again, and this time applied two heavy coats. It looks decent now, but I wonder how it will be after I sand it?

[Mopower71]

I still haven't put the engine mount in, and don't have the parts to do the 24mm mount or an empty D casing so I can adapt it down.

[tbzep]

I still haven't put the engine mount in, and don't have the parts to do the 24mm mount or an empty D casing so I can adapt it down.
It's ok to put in an 18mm mount. The Cobra flies just fine on a C6-5 motor and I've flown it on a B6-4 without issue. Some folks think you aren't a real man unless you use a big enough motor to lose visual contact with the rocket. :rolleyes:

[Mopower71]

I loose visual contact with the wizards every time we launch them. And that's on an A8-3. I can't see using a C6-5 on it. It would never come home.

[A Fish Named Wallyum]

I loose visual contact with the wizards every time we launch them. And that's on an A8-3. I can't see using a C6-5 on it. It would never come home.
C6-7. And make sure it's calm. Dead calm.

[tbzep]

I loose visual contact with the wizards every time we launch them. And that's on an A8-3. I can't see using a C6-5 on it. It would never come home.
Estes makes a 1/2A6-2 in 18mm and a 1/2A3-2T and 1/2A3-4T in 13mm (stuffed in old hollowed out 18mm casing) that you could use to keep it in sight.

BTW, the Wizard needs an A8-5 instead of an A8-3. The 3 second delay is closer to 2 seconds. I use A8-5's in the Generic E2X rocket for schools and it is considerably larger than the Wizard.

[ghrocketman]

If you want LAME-O flights on every 18mm motor but the Aerotech D21/D24 then by all means go 18mm.
Otherwise, correctly wait and get the parts to make it 24mm powered.
All it takes is a 4" piece of BT50 tubing, two RA5055 rings and a RA 2050 engine block.
About $3 woth of parts.

In other words, wait until you have the parts to do it RIGHT, and NO, a Cobra 1500 in 18mm is NOT RIGHT even though the "stock kit" came with that IDIOTICALLY SMALL mount.
MAN UP and at least go 24mm.
Mine had a 29mm and was just about RIGHT.

[tbzep]

If you want LAME-O flights on every 18mm motor but the Aerotech D21/D24 then by all means go 18mm.
Otherwise, correctly wait and get the parts to make it 24mm powered.
All it takes is a 4" piece of BT50 tubing, two RA5055 rings and a RA 2050 engine block.
About $3 woth of parts.

In other words, wait until you have the parts to do it RIGHT, and NO, a Cobra 1500 in 18mm is NOT RIGHT even though the "stock kit" came with that IDIOTICALLY SMALL mount.
MAN UP and at least go 24mm.
Mine had a 29mm and was just about RIGHT.

GH, just stop that crap...enough is enough. Not everybody has a billion acre field to launch from. Less experienced people will have a terrible experience if they follow your advise. MoPower71, I promise that big motors will not compensate for the size of your package. :mad:

[Initiator001]

How did I miss this thread?

I just finished a Cobra 1500 clone using Semroc & BMS parts along with Excelsior Rocketry (Gordy/Sandman) decals.

I built it stock except for 3/16" launch lugs and having the rocket separate at the junction between the yellow and white painter body tube sections. This was necessary in order to get the rocket to fit in my car.

I used an original late 70s-early 80s Estes parachute for the model.

Finished weight/mass without motor was 4.4 oz. Yikes! Maybe I should have put a 24mm motor mount in it.

I flew the Cobra 1500 up in Los Angeles at the SCRA NAR Section sport launch last Saturday (March 7).

Propulsion was provided by an Estes C6-3 motor.

Good flight and recovery. :)

[Royatl]

How did I miss this thread?

I just finished a Cobra 1500 clone using Semroc & BMS parts along with Excelsior Rocketry (Gordy/Sandman) decals.

I built it stock except for 3/16" launch lugs and having the rocket separate at the junction between the yellow and white painter body tube sections. This was necessary in order to get the rocket to fit in my car.

I used an original late 70s-early 80s Estes parachute for the model.

Finished weight/mass without motor was 4.4 oz. Yikes! Maybe I should have put a 24mm motor mount in it.

I flew the Cobra 1500 up in Los Angeles at the SCRA NAR Section sport launch last Saturday (March 7).

Propulsion was provided by an Estes C6-3 motor.

Good flight and recovery. :)

I have a half-painted Cobra 1500 in my garage. It spent the good part of 35 years in my mom's storage shed, and it survived the shed's partial destruction from a tree limb falling that wasn't noticed until rain had ruined most everything in it. The rocket survived because it was suspended above everything else in the shed between a couple of beams that held up one side of the shed while the other side collapsed slowly from water damage and humidity. Why the rocket doesn't show any humidity damage, I have no clue.