Alpha III with d-12???

Alpha III with d-12???

Post by Stephen Vo » Tue, 21 Nov 1995 04:00:00



Has anyone tried launching the alpha III(the one with the plastic fin
assembly) with a D12 engine. I know d12 engine fits although you could
not use it again once launched. I wonder how it would fly?

--

Stephen Voss

 
 
 

Alpha III with d-12???

Post by Jonathan Sivie » Tue, 21 Nov 1995 04:00:00


Quote:

>Has anyone tried launching the alpha III(the one with the plastic fin
>assembly) with a D12 engine. I know d12 engine fits although you could
>not use it again once launched. I wonder how it would fly?

   A better idea is to fly an unmodified Alpha-III on an Aerotech D21 (or
an E25 or D13, D24 or E28 reload).  These are 18mm motors and so should fit.
At a launch here a couple of months ago one of our member, Greg Smith, flew
an Alpha-III he had built as the demo kit at a workshop we had for kids on
a D21.  The fins vibrated with a very audible buzz.  They didn't flutter off
though.  I don't think he got it back.

Jonathan

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Alpha III with d-12???

Post by The Silent Observ » Tue, 21 Nov 1995 04:00:00




Quote:

>Has anyone tried launching the alpha III(the one with the plastic fin
>assembly) with a D12 engine. I know d12 engine fits although you could
>not use it again once launched. I wonder how it would fly?

If you were to replace the motor mount that comes with the Alpha III,
with a simple "engine block" unit (basically, a ring glued into the body
tube to transmit the thrust of the motor), and install the motor latch
on the outside of the plastic fin unit, you could probably fly the Alpha
III on a D12-7 -- note that the D12 is a 24mm motor, as opposed to the
18mm A-B-C Estes motors.

Also, note that the Alpha and Alpha III both fly very high on a C6
motor; they'd go a good bit higher on a D12; in fact, a lost rocket (due
to out-of-sight ejection) is a very strong possibility.

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Alpha III with d-12???

Post by Larr » Wed, 22 Nov 1995 04:00:00


Quote:

> Has anyone tried launching the alpha III(the one with the plastic fin
> assembly) with a D12 engine. I know d12 engine fits although you could
> not use it again once launched. I wonder how it would fly?
> --
> Stephen Voss


On a D21, an Alpha III would be naturally near its optimal mass of 73 grams.
DIGITRAK estimates about 1840 feet and mach 0.53 - if the Cd remains around
.544, my empirical value for the model. As Mark points out, however, those
flexible fins are going to buzz. Expect high acceleration (31 g's), and hence
difficulty in following the rocket by eye. An Alpha with balsa or bass fins
is more suitable. You will likely see performance like that predicted with
a reasonably well-finished model - except that the delay is a little short.
You may lose as much as 50 feet that way.

I once launched an Alpha with balsa fins on an E-25. The optimal mass of that
configuration is about 82 grams. Since I wanted no trouble tracking it, I
weighed it down with tracking powder to about 90 grams - the predicted
altitude penalty was modest. Well, I could follow it by eye, but the ~40 grams
of tracking powder was ill advised. Some of it shifted forward at cutoff and
pushed out the nose cone, and displayed a red puff in the process. At
ejection, the hot Aerotech charge blew out the walls, rather than pushing out
the remaining powder. :-( The fins, however, stayed on and did not buzz. (It
wasn't clear what was happening just then, but I saw the same effect with a
small rocket on an A8 - I needed a low flight for a measurement and went
overboard with the tracking powder. To confirm, I wasted a similar rocket.)
Predicted altitude for the optimal configuration is 2300 feet at a maximum
of mach 0.66. At 50 grams, a more natural mass, expect 2077 feet and mach 0.9.
At optimal mass, expect 39 g's. At 50 grams, expect 64 g's - so glue those
fins tight!

A D21 should deliver 2125 feet at mach 0.64 at an optimal mass of 75 grams.
At 50 grams, expect 2000 feet and mach .83.

You *can* follow these things at optimal mass - but in the case of the Aerotech
motors, you may miss them at natural mass.  The E25 configuration at natural
mass burns out at 651 feet - that's 651 feet in less than a second. You may
find that the smoke trail disperses once it gets up to speed. By contrast, the
D12 durns out at 522 feet - and this takes about 1.6 seconds.

So use bass wood fins, choose a clear, calm day, use a nice bright streamer
instead of a chute, aim for optimal mass, and have plenty of trackers on a
big field. You *can* get it back.  

Luck and Regards,
-Larry Curcio

 
 
 

Alpha III with d-12???

Post by Matthew S Greenl » Wed, 22 Nov 1995 04:00:00


Quote:

>I once launched an Alpha with balsa fins on an E-25. The optimal mass of that
>configuration is about 82 grams. Since I wanted no trouble tracking it, I
>weighed it down with tracking powder to about 90 grams - the predicted
>altitude penalty was modest. Well, I could follow it by eye, but the ~40 grams
>of tracking powder was ill advised. Some of it shifted forward at cutoff and
>pushed out the nose cone, and displayed a red puff in the process. At
>ejection, the hot Aerotech charge blew out the walls, rather than pushing out
>the remaining powder. :-( The fins, however, stayed on and did not buzz. (It
>wasn't clear what was happening just then, but I saw the same effect with a
>small rocket on an A8 - I needed a low flight for a measurement and went
>overboard with the tracking powder. To confirm, I wasted a similar rocket.)
>Predicted altitude for the optimal configuration is 2300 feet at a maximum
>of mach 0.66. At 50 grams, a more natural mass, expect 2077 feet and mach 0.9.
>At optimal mass, expect 39 g's. At 50 grams, expect 64 g's - so glue those
>fins tight!

  I once flew my Estes mega-Sizz on an Aerotech E50 (crunch the numbers on that
for me, would you?) It was a smoker!  I have never seen acceleration like that
before. Remember boys and girls, that is 40 N-s in less that one second. I think I
put a 7 second delay on it and it was still going up quite fast when the ejection
charge fired.  I am not sure of the g-force acceleration on liftoff, but I know it
was a lot.  Just an interesting tid-bit!

--
Matthew Greenlaw           |  Is 40:31 - "They shall mount up with wings


Mechanical Engineering     |  http://Hubcap.Clemson.Edu/~mgreenl  

 
 
 

Alpha III with d-12???

Post by Larr » Wed, 22 Nov 1995 04:00:00


Quote:

> On a D21, an Alpha III would be naturally near its optimal mass of 73 grams.
       ^^^
> DIGITRAK estimates about 1840 feet and mach 0.53 - if the Cd remains around
> .544, my empirical value for the model. As Mark points out, however, those
> flexible fins are going to buzz. Expect high acceleration (31 g's), and hence

Whoops! That's D12

Sorry!
-Larry C.

 
 
 

Alpha III with d-12???

Post by kaplo.. » Wed, 22 Nov 1995 04:00:00



Quote:

>>Has anyone tried launching the alpha III(the one with the plastic fin
>>assembly) with a D12 engine. I know d12 engine fits although you could
>>not use it again once launched. I wonder how it would fly?

>    A better idea is to fly an unmodified Alpha-III on an Aerotech D21 (or
> an E25 or D13, D24 or E28 reload).  These are 18mm motors and so should fit.

Try E27. The E28 is a 24mm full E reload... Unfortunately, the 18mm E27 only
comes in a short delay, hardly appropriate for an Alpha-III.


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Alpha III with d-12???

Post by Helen Rapo » Wed, 22 Nov 1995 04:00:00



Quote:

>>Has anyone tried launching the alpha III(the one with the plastic fin
>>assembly) with a D12 engine. I know d12 engine fits although you could
>>not use it again once launched. I wonder how it would fly?

>   A better idea is to fly an unmodified Alpha-III on an Aerotech D21 (or
>an E25 or D13, D24 or E28 reload).  These are 18mm motors and so should fit.
>At a launch here a couple of months ago one of our member, Greg Smith, flew
>an Alpha-III he had built as the demo kit at a workshop we had for kids on
>a D21.  The fins vibrated with a very audible buzz.  They didn't flutter off
>though.  I don't think he got it back.

**********
I did a few runs of RASP on a Alpha III with Cd of .75 and got the following:

C6  - 1009 ft
D12 - 1492 ft
D21 - 1627 ft
E25 - 1714 ft

Also did a C6/C6 combo and I got 1638 feet.

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Alpha III with d-12???

Post by Roger Iv » Mon, 27 Nov 1995 04:00:00



Quote:
> Have you considered praying with your rocket before launch?

Yeah, but then I'd have to pick a god. And how do I know whether I've picked
one actually willing to go out of his/her/its way just make sure I recover
my rockets?
--
-------------------------+---------------------------------------------
Roger Ivie               | "Once again we see that clowning and anarchy

http://cc.usu.edu/~ivie/ |
 
 
 

Alpha III with d-12???

Post by Kevin Nola » Tue, 28 Nov 1995 04:00:00


     There's only one way to find out which god to pray to; ask. If you
*really* want to know, he *really* wants you to know Him. He is interested
in all the seemingly insignificant details of life too, like getting our
rockets back, or having all the motors in a cluster ignite together. How
much more the weightier matters!

Quote:


> > Have you considered praying with your rocket before launch?

> Yeah, but then I'd have to pick a god. And how do I know whether I've picked
> one actually willing to go out of his/her/its way just make sure I recover
> my rockets?
> --
> -------------------------+---------------------------------------------
> Roger Ivie               | "Once again we see that clowning and anarchy

> http://www.FoundCollection.com/~ivie/ |

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Alpha III with d-12???

Post by kingr » Sat, 02 Dec 1995 04:00:00


:      There's only one way to find out which god to pray to; ask. If you
: *really* want to know, he *really* wants you to know Him. He is interested
: in all the seemingly insignificant details of life too, like getting our
: rockets back, or having all the motors in a cluster ignite together. How
: much more the weightier matters!

: > Yeah, but then I'd have to pick a god. And how do I know whether I've picked
: > one actually willing to go out of his/her/its way just make sure I recover
: > my rockets?

For cluster flights, I always pray to the almighty Allatonceplease, the
legendary god of simultaneous ignition.

Eric Specht at the Dayton Network Access Company

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