Jeff,
I think that the standard Duration Equation might be of use to you. In case you are not familiar with it I have it on an ‘Excel’ spreadsheet and you are welcome to a copy, just let me have your email address. I have attached a screen shot and the actual equation is at the top left corner. I entered the following figures: rubber energy 4000ft, prop efficiency 50%, wing area 70 sq.in. (I added a bit for the tail), lift coefficient 0.65, L/D 5, rubber weight 2g, airframe weight 7g. and this gave me a duration of 5:05 (five minutes and 5 seconds).
I then checked the duration with airframe weights from 8 to 13g in 1gram steps and the times were: 4:21, 3:46, 3:18, 2:56, 2:37, 2:22.
John Barker - England
From: Indoor_Construction_at_yahoogroups.com [mailto:Indoor_Construction_at_yahoogroups.com]
Sent: 19 May 2015 03:13
To: Indoor_Construction_at_yahoogroups.com
Subject: [Indoor_Construction] Mass vs flight time
For next year's Science Olympiad Wright Stuff rules we're considering a payload bonus. To size it appropriately, we'd like to have a good estimate of flight time penalty for adding mass to a plane without changing much else.
Example. 7 gm airplane, 50 by 8 cm wing, tail 24 by 5 cm, prop 20 cm, 2 gm rubber (purely hypothetical, please don't report that this will be next year's dimensions, it won't)
Let's say it has a max capability of 5 minutes properly trimmed in a 60 ft site (pretty close to the winning time and ceiling ht this year).
Assume you can modify prop/rubber combination and trim to carry the extra mass (say 1-6 gm) to max possible time, is there a formula or program available to estimate the flight time penalty?
If yes, can you please point me to it?
And again, this is all purely hypothetical at this point, please don't get students working on this yet, we may not use this as a bonus.
Thanks,
Jeff Anderson
Livonia, MI
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Received on Tue May 19 2015 - 03:54:56 CEST