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Model Forum / General / Rockets / January 2007F-Altitude Question
F-Altitude requires less than or equal to 80Ns total impulse. It that manufacturer's published impulse or tested total impulse? I did a quick check of the NAR PinkBook and did not see clarification. Curious because I was contemplating a 2 D12 to D12 to E9. Published impulse would be 90Ns, tested impulse is about 78Ns. Or does this fail because of the clustered staged combination before it even gets to the impulse question?  SignatureTom Koszuta Western New York Sailplane and Electric Flyers Buffalo, NY > Curious because I was contemplating a 2 D12 to D12 to E9. Published impulse > would be 90Ns, tested impulse is about 78Ns. > Or does this fail because of the clustered staged combination before it even > gets to the impulse question? > Tom Koszuta Tested impulse. Estes says their D12's are 20ns, which they are not; they are more like 17ns. You can get there any way you want as long as total impulse is 40.01-80.00 ns. The best way would be a min diameter long burning F motor that is a full 80 ns. Like an old F25 or F10. A F32 would be even better as it's 24mm in diameter. I don't know if they are still certified though. AT's new motors are wimpier now, unfortunately. Daniel > F-Altitude requires less than or equal to 80Ns total impulse. It that > manufacturer's published impulse or tested total impulse? Tested impulse--as tested by the NAR S&T, and as reported on the main web page, NOT the value reported on the pdf pages. (I've asked that this be changed and it may be, but not yet.) > I did a quick check of the NAR PinkBook and did not see clarification. See section 4.7. > Curious because I was contemplating a 2 D12 to D12 to E9. Published > impulse would be 90Ns, tested impulse is about 78Ns. Tested impulse would be 79.5, per the values on the main motor page. (78.39 per the values on the pdf's.) Either way you are OK. > Or does this fail because of the clustered staged combination before > it even gets to the impulse question? Clusters and stages are allowed in this event. Steve Humphrey > Tested impulse would be 79.5, per the values on the main motor page. > (78.39 per the values on the pdf's.) Either way you are OK. Could you point out where the differences are between the two sources, and send a note to NAR S&T? -John D. > Could you point out where the differences are between the two > sources, and send a note to NAR S&T? Heh ... I did, about a year ago. :-( http://groups.yahoo.com/group/contestRoc/message/14179 (The links in my message in the above link are now defunct as I removed the files a few months later.) To be fair, there is an issue about which total impulse value to use for contests. An argument for the status quo is that the "over stated" total impulses cover the 3-sigmas (or whatever the interval is) of statistical variation. SignatureSteve Humphrey (replace "spambait" with "merlinus" to respond directly to me) At a contest years ago there was an E altitude event. Everyone used min diameter single stage rockets with composite E engines except for one guy who used a stage D12-0/D12-7 rocket. He won by over 200 feet over mine which used a Crown E45. Every altitude contest since then that I participated in was won by staged rockets. Admittedly I ahve not participated in any since the late 1980's. Joe W > F-Altitude requires less than or equal to 80Ns total impulse. It that > manufacturer's published impulse or tested total impulse? [quoted text clipped - 11 lines] > Western New York Sailplane and Electric Flyers > Buffalo, NY >F-Altitude requires less than or equal to 80Ns total impulse. It that >manufacturer's published impulse or tested total impulse? [quoted text clipped - 5 lines] >Or does this fail because of the clustered staged combination before it even >gets to the impulse question? Specifically you use the "tested" the acutal term you should use is the certified value, which is published in the NAR certification list. The NAR switched to this value largely becuse some manufacturers were and still are publishing incorrect infomation about their motors. Not just Estes. the problem was really accute with FSI motors at one time. The problem was not with FSI, but with the motor manufacturer Lonie Reese contracted to make his motors. He had known fo years that the manufactirer was skimping, in fact he was skimping so bad, that E5's were no longer 22Ns E's but D's. Lonnie took over his engine manufacturing and re-upped the total impulse to 22Ns. But the E5 was still certified as a "D". For NARAM-24 some people realised this and brought a bunch of his new E5's to fly in D SuperRoc. Luckily Lonnie was there with a bunch of his new E5's. Even though I had built my superroc for the 24mm Estes D's I put one of Lonnie 21mm E5's in the model and was in first place for most of the day. On the last flight of the day Tom Pastrick put up a model he had built for 21mm and beat me. Dan Dan Winings dan.winings@novaar.org |
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