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NAR Competition Question Thread
#11
(11-09-2015, 11:24 AM)kjohnson Wrote: Personally in any high performance design for this event, I would go with some powder to show the ejection point, and a very visible streamer. 

The attachment point per the rules need to be at one point on the streamer, and it needs to handle the expected loads and then some. I have seen music wire stiffeners used on the leading edge of the streamer in competitions in the past, but the tape and cord method works fine in most of the lower impulse classes.  As long as it's sized appropriately I don't see why that wouldn't work at G impulse.

If you are looking to use Mylar for your streamer, I wouldn't go any thinner than 1mil.  2mil might be better.

kj

I think our 8" Silver Dura-lar material/kits should be a good choice for that event this year... 2 mil thick, shiny and takes a nice crease!  :-)

http://www.asp-rocketry.com/ecommerce/Si...?cat_id=47

Andy/ASP
Andy Jackson
NAR #14575
TRA #1191
Aerospace Speciality Products
http://www.asp-rocketry.com

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#12
(11-10-2015, 10:51 AM)ASP Wrote:
(11-09-2015, 11:24 AM)kjohnson Wrote: Personally in any high performance design for this event, I would go with some powder to show the ejection point, and a very visible streamer. 

The attachment point per the rules need to be at one point on the streamer, and it needs to handle the expected loads and then some. I have seen music wire stiffeners used on the leading edge of the streamer in competitions in the past, but the tape and cord method works fine in most of the lower impulse classes.  As long as it's sized appropriately I don't see why that wouldn't work at G impulse.

If you are looking to use Mylar for your streamer, I wouldn't go any thinner than 1mil.  2mil might be better.

kj

I think our 8" Silver Dura-lar material/kits should be a good choice for that event this year... 2 mil thick, shiny and takes a nice crease!  :-)

http://www.asp-rocketry.com/ecommerce/Si...?cat_id=47

Andy/ASP
Meh - my first reply didn't show.
Andy, can you get the Dura-Lar in wider widths?
Bill Cooper
NAR #97213
L1: NARAM 56, 2x Upscale Fliskits Corona
L2: Oct. 2015, Wildman Interceptor A.A.D. 98
Member of UROC, former member of NOVAAR and NARHAMS
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#13
(11-10-2015, 11:03 AM)75Grandville Wrote:
(11-10-2015, 10:51 AM)ASP Wrote:
(11-09-2015, 11:24 AM)kjohnson Wrote: Personally in any high performance design for this event, I would go with some powder to show the ejection point, and a very visible streamer. 

The attachment point per the rules need to be at one point on the streamer, and it needs to handle the expected loads and then some. I have seen music wire stiffeners used on the leading edge of the streamer in competitions in the past, but the tape and cord method works fine in most of the lower impulse classes.  As long as it's sized appropriately I don't see why that wouldn't work at G impulse.

If you are looking to use Mylar for your streamer, I wouldn't go any thinner than 1mil.  2mil might be better.

kj

I think our 8" Silver Dura-lar material/kits should be a good choice for that event this year... 2 mil thick, shiny and takes a nice crease!  :-)

http://www.asp-rocketry.com/ecommerce/Si...?cat_id=47

Andy/ASP
Meh - my first reply didn't show.
Andy, can you get the Dura-Lar in wider widths?

I can have it cut wider, but it's a pretty big minimum order I have to place (and the retail cost per piece I'm afraid would get prohibitive in wider widths), so I don't think wider pieces will likely happen. Occasionally I can get off-cuts at a decent cost, so I will keep my eyes out in case something happens to show up in a size that might be useful, but that would just be luck...

Andy/ASP
Andy Jackson
NAR #14575
TRA #1191
Aerospace Speciality Products
http://www.asp-rocketry.com

Reply
#14
ASP Wrote:I think our 8" Silver Dura-lar material/kits should be a good choice for that event this year... 2 mil thick, shiny and takes a nice crease!  :-)

http://www.asp-rocketry.com/ecommerce/Si...?cat_id=47

Andy/ASP

I had that material in mind, Andy. Smile

kj
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#15
Some sources for wider 2mil aluminized mylar (polyester):

I just found a small vendor called Nielsen Enterprises http://nielsen-enterprises.myshopify.com/ selling 1 and 2mil x 54" double-side coated mylar in 25, 50, 100 ft lengths for just over $1/ft in the 2 mil 50 ft size.

Also in San Diego you can buy 2mil x 27.5" wide aluminized mylar at our local plastics supplier (Ridout Plastics, online as eplastics.com) in any length for something like $3.50/ft. VERY expensive by the foot but OTC and no minimum length.
Dave Cook 
NAR 21953 L2    TRA 1108
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#16
(11-06-2015, 05:58 PM)caveduck Wrote: I've been in competition for decades and attended over a dozen NARAMS.. I've never seen G SD flown since it was added to the Pink Book a number of years ago.  For smaller motors SD is somewhat of an altitude contest, but with G motors I think it will be essential to keep the altitude down and use a large (10x100", maybe more) 1 mil reflective Mylar streamer.

Dave,

You missed all the crazy NAR competition launches we had outside Las Vegas in 1990-1992.

One event we flew was G SD.

Scott Pierce designed a rocket using a 24mm AeroTech G55 core motor and three side pods with Estes C5-3 motors.
I think it won. Big Grin
The model was recovered.
It had a big mylar streamer.
Bob
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#17
A BP/composite cluster? wow...especially since the C5's weren't really needed...but I suppose it was OK if some of them didn't light. Recipe for a big prang though if the G55 lights up late.
Dave Cook 
NAR 21953 L2    TRA 1108
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#18
caveduck Wrote:A BP/composite cluster?  wow...especially since the C5's weren't really needed...but I suppose it was OK if some of them didn't light.  Recipe for a big prang though if the G55 lights up late.

In NAR competition if the event is G powered you are allowed to use 80.1 - 160.0 Ns.  While most folks will use a single motor in the allowable range, some folks like to use every scrap of N-sec they are allowed. It's a risk/reward strategy.

The model described above would have had total installed impulse of 146.9 Ns as opposed to 119.6 Ns for the G55 alone.

kj
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#19
Fun discussion...Given that it isn't very hard for competition people to fly away a C powered SD model with 10 N-s, you really don't need the extra power, especially if you can pick air. Another factor is that the extra motor casings and pods add quite a bit of descent mass, which you totally do not want in SD. The extra descent rate could easily overwhelm the additional altitude, which itself might not be too large since side pods are very draggy. Overall I'd favor the reliability of a single motor solution every time for a duration event, and to increase performance I'd focus on making the descent mass lower.
Dave Cook 
NAR 21953 L2    TRA 1108
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#20
OK, just got my latest shipment of parts (thanks Andy!). On to my next question(s).

1) For SuperRoc, does canting the fins ~1-2 degrees for spin stability make any difference? I am thinking about the propensity that over-stable models have to weathercock.
2) For 1/2 A models, will .011 FG serve for fins, or is it too flexible? What about for A models? Yes I can and will test this myself at some point, but I hate wasted effort, and it's pretty darn cold right now in Utah, with more cold in the forecast for the next couple months.
Bill Cooper
NAR #97213
L1: NARAM 56, 2x Upscale Fliskits Corona
L2: Oct. 2015, Wildman Interceptor A.A.D. 98
Member of UROC, former member of NOVAAR and NARHAMS
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