Streamer duration question...

[KermieD]

Got a Cougar 660 that I'm building, with the hopes of getting it ready for a regional 1/2A Streamer Duration Multi-Round contest. I have a couple of questions:

1) The kit instructions advise folding the entire streamer into pleats. I read somewhere in SpRocketry that the current trend is to leave the last 6" or so of the streamer flat to create a flutter at the end. Anyone have any thoughts on this?

2) What on earth is Multi-Round?

 

[jflis]

Kermie,

I've heard of that too, but don't fully support it, here's why:

- The pleat folding pattern, as designed into the Cougar models is backed by MIT wind tunnel data.

- This data didn't show any advantage to having a section of flat at the end of the streamer

- Personal observation showing a good deal of flutter in the end of a streamer pleated all the way to the end.

That said, I have no field data on keeping the end of the streamer flat, but I doubt you would gain or loose more than a percent or two of total performance.

jim

 

[shockwaveriderz]

15.12 Multi-Round Events
Any duration event listing a multi-round maximum may be flown as a multi-round event. This must be indicated on the
contest sanction. The weighting factor for the event shall be increased by 4 (four) in this case.
15.12.1 Number of Flights
Each contestant is initially allowed three official flights in a multi-round event. The Contest Director may designate
that each flight must be flown in the time interval (round) designated by the Contest Director. Any model not flown in
its designated round shall receive a zero score.
15.12.2 Number of Models
A contestant may enter no more than two models in a multi-round event for the purpose of making all official flights,
including any necessary additional flights, except as stated in Rule 11.5.
15.12.3 Maximum Time
The official duration of each flight shall be calculated as follows: if the duration achieved exceeds the maximum time
limit defined for that flight, the entry shall be awarded the maximum time limit; otherwise the entry shall be awarded
its achieved duration in seconds. Timers may stop timing the flight after it has achieved the maximum time.
15.12.4 Scoring
Multi-round events shall be scored as follows: the official durations achieved by the contestant on the initial three
official flights in the event shall be summed. If there is no tie for first place, then the contestant achieving the highest
score is the winner. If there is a tie, contenders for first place shall be given the opportunity to make additional official
flights (flyoffs) to determine the winner. The maximum time limit for a contestant’s first additional flight shall be
computed by adding a one minute increment (or, at the discretion of the Contest Director, a greater increment) to the
maximum time limit for the event. For each subsequent additional flight made by a contestant, one additional increment
shall be added to the previous maximum time limit. Additional flights shall be held in this manner until a winner is
determined. Second through fourth places shall be distributed first among the other contenders in the flyoffs, and then
among any other contestants having made qualified flights, on the basis of total computed score.
15.12.5 Return
The models in multi-round duration events need not be returned to the officials except as required by Rules 9.10 and
15.12.2.
15.12.6 Reduced Maximum Time
If unusual weather or field conditions are encountered, the Contest Director, with the concurrence of a majority of the
contestants entered in the event, may lower the maximum time to a more reasonable value. The Contest Director must
advise the Regional Contest Board that this has been done and the reasons for doing so.

The MAX is 60 seconds for 1/2 A SD (MR).....

shockie B)

 

[KermieD]

Thanks guys!

I had no idea that MIT would be that interested in streamer duration. Cool!!

 

[jflis]

MIT had one of the most sophisticated rocket clubs on the planet at one point. They held an annual convention (MIT-CON) wherein they would publish their MIT-CON reports which were mainly technical journals about what they've been doing in their lab.

The conventional pleat fold that is so common can be attributed to them during wind tunnel testing. Also the 10:1 ratio can be attributed to MIT

jim

 

[Fore Check]

Originally posted by jflis
MIT had one of the most sophisticated rocket clubs on the planet at one point. They held an annual convention (MIT-CON) wherein they would publish their MIT-CON reports which were mainly technical journals about what they've been doing in their lab.

The conventional pleat fold that is so common can be attributed to them during wind tunnel testing. Also the 10:1 ratio can be attributed to MIT

jim

What do you mean by 10:1 ratio? ( )

 

[jetra2]

The 10:1 ratio.

Basically all it is is when your streamer exceeds its width times 10, it becomes less and less effective. Instead of flpping around and creating a buncha drag, it will actually start "streaming" and not be flopping around.

HTH,
Jason

 

[jflis]

yep.

For example, a streamer that is 10" long and 1" wide will provide higher drag (eg: slow the rocket more) than a streamer that is 15" long and 1" wide.

meaning, making it longer doesn't really do any good, and in fact does harm (falls faster)

jim