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  #21  
Old 05-22-2019, 06:58 PM
A Fish Named Wallyum's Avatar
A Fish Named Wallyum A Fish Named Wallyum is offline
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I cloned one last year. On the day I flew it, it was the only rocket to fly back over the pads with the wind. All I can do now is remember it.
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  #22  
Old 05-23-2019, 01:05 AM
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SEL SEL is offline
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Quote:
Originally Posted by jetlag
I have to ask, what is the incredible attraction so many of you nice folks have for these rockets? My guess is that it must be nostalgia? They are so simple 3 or 4fnc rockets.
Happy for you, though!😁

Allen



For me, anyway, it's 'the look'. A well designed rocket, no matter how simple, will maintain it's appeal and every one of the Enerjet SR series has that. Of all the rockets I bring to launches both with clubs and on my own, the SR1340, 1340/20 and SR2650' and the down-scaled variants I've built are the rockets that get the 'Wow!' comments - the ones I get the most questions about.
Another example is the Crown/SSRS Lasor 134 -very simple, sleek design
(though notice the similar fins to the SR2650...)


Estes take note: The down-scaled SR2650 for 13mm motors would make a great kit!
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  #23  
Old 05-23-2019, 09:28 AM
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I've seen photos of the SR1340, 1340/20 and SR2650 kits, but I've never seen literature on them. Where can I find the advertising literature? The 72 Enerjet catalog only has the Nike Ram, Athena, etc. I know we have plans on YORS, but I don't ever run across it in old catalogs, mailings, etc.
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Last edited by tbzep : 05-23-2019 at 09:56 AM.
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  #24  
Old 05-23-2019, 01:21 PM
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Quote:
Originally Posted by tbzep
I've seen photos of the SR1340, 1340/20 and SR2650 kits, but I've never seen literature on them. Where can I find the advertising literature? The 72 Enerjet catalog only has the Nike Ram, Athena, etc. I know we have plans on YORS, but I don't ever run across it in old catalogs, mailings, etc.


I think what you are looking for is here in the plans section:

http://www.oldrocketplans.com/enerjet.htm

On the 2650 plans, what is not obvious is that the full brochure opens when one clicks the line drawing.

This is the only advertising literature I've seen on these kits, other than originals of the same I have in my personal collection.

Hope this helps.


Earl
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  #25  
Old 05-23-2019, 02:06 PM
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Jerry Irvine Jerry Irvine is offline
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Quote:
Originally Posted by Earl
I think what you are looking for is here in the plans section:
http://www.oldrocketplans.com/enerjet.htm
On those brochures reference is made to 29mm motors from 9-40 pound seconds

The E24 was 40 N-s 9 lb-sec. 1.7s burn
The F52 was 52 N-s 11.7 lb-sec. 1.0 sec burn
The F67 was 80 N-s 18 lb-sec. 1.2 sec burn
the G76 was 120 N-s 27 lb-sec 1.6 sec burn
Unobtanium H111 was 178 N-s 40 lb-sec. 1.6 sec burn

Put that in your rocket and fly it.

Just Jerry
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Last edited by Jerry Irvine : 05-24-2019 at 08:22 AM.
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  #26  
Old 05-23-2019, 03:36 PM
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Quote:
Originally Posted by A Fish Named Wallyum
I cloned one last year. On the day I flew it, it was the only rocket to fly back over the pads with the wind. All I can do now is remember it.


Was this a clone of the 1340/20? The same thing happened in the final flight of mine.
Pointed it into the wind -admittedly it was a pretty stiff breeze out on the beach at Neskowin - and as soon as it left the rod it cruised off with the wind. Wonder if it has anything to do with the size of the payload section? Pretty large, light weight area ...

S.
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  #27  
Old 05-24-2019, 12:14 AM
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There is some new data about the aerodynamics of fins below a wider transition section. Check out the article titled "Increasing Rocket Aerodynamic Performance" by Thomas Salverson on page 42 in the May/June 2019 edition of Sport Rocketry. Essentially (on the right side of page 48) the portion of the fin inside the turbulent wake of the airflow behind a reducing transition doesn't do anything for the rockets stability. It is suggested that while a transition section below a wider payload section decreases the aerodynamic drag on a rocket, it induces a wake that interferes with and decreases the effectiveness of the rockets fins, and these fins should extend out beyond the rockets body until they are in the laminar airflow region beyond the diameter of the transition. I am working on a RockSim fix for this effect.

Also mentioned is that rail buttons create an asymmetric wake behind the rocket causing it to fly in an arc. Did you use launch lugs on your design that might have a similar effect? The original 1340/20 used a thin loops of wire for launch lugs visit: http://plans.rocketshoppe.com/enerj.../enj1340-20.pdf
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  #28  
Old 05-24-2019, 01:21 AM
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Quote:
Originally Posted by teflonrocketry1
There is some new data about the aerodynamics of fins below a wider transition section. Check out the article titled "Increasing Rocket Aerodynamic Performance" by Thomas Salverson on page 42 in the May/June 2019 edition of Sport Rocketry. Essentially (on the right side of page 48) the portion of the fin inside the turbulent wake of the airflow behind a reducing transition doesn't do anything for the rockets stability. It is suggested that while a transition section below a wider payload section decreases the aerodynamic drag on a rocket, it induces a wake that interferes with and decreases the effectiveness of the rockets fins, and these fins should extend out beyond the rockets body until they are in the laminar airflow region beyond the diameter of the transition. I am working on a RockSim fix for this effect.

Also mentioned is that rail buttons create an asymmetric wake behind the rocket causing it to fly in an arc. Did you use launch lugs on your design that might have a similar effect? The original 1340/20 used a thin loops of wire for launch lugs visit: http://plans.rocketshoppe.com/enerj.../enj1340-20.pdf



Interesting - I'll pick up the magazine tomorrow. While the fins do extend somewhat beyond the payload diameter, it may not be enough if the wind is up. I used stand-off's for ( 2 ) lugs to fit a 1/4'' rod (see photo's below). I didn't know about the loop-lugs until long after I built mine (back in '96/'97) and rail buttons weren't common, so I just assumed the stock kit used the same style lug as the SR2250/2650.

I'd logged many flights on this model - I'm guessing upwards of 25 - in all kinds of weather, more than a few launches at the beach in similar winds. All were flown off a 4 foot 1/4'' stainless rod and as far as I can recall, all went where I aimed them. I had to go back to my original thread for this ( http://forums.rocketshoppe.com/show...&highlight=1340 ) to remind myself what motor I used and it may just have been the combination of stiff winds and the (relatively) long burn E9, but I still would have expected it to weathercock into the wind rather than with.


S.
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  #29  
Old 05-24-2019, 03:11 PM
stefanj stefanj is offline
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Wow, I love that shot of the launch in front of the ocean!

All of those models are nicely finished. The Crown model is a real "back in the day" type finish design; it reminds me of pictures in late-80s vintage catalogs.
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  #30  
Old 05-24-2019, 03:57 PM
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Quote:
Originally Posted by stefanj
Wow, I love that shot of the launch in front of the ocean!

All of those models are nicely finished. The Crown model is a real "back in the day" type finish design; it reminds me of pictures in late-80s vintage catalogs.


Thanks Stephan.
That day at the beach was no Day At The Beach; in addition to losing the 1340/20,
the upscaled Sprint landed in the ocean. That one dated back to the 96/97 time frame as well.
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