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#11 Gap staging vent hole size

Posted: Sun, 12 Jun 16, 21:58 pm
by Commander
Much like TMacklin, I am also retrofitting my Renegade to a 24 mm engine booster. Mine was the recent Renegade D 2410 that I had built to the 2109 multi-stage version. Needless to say, I now see the error of my ways in trying to launch this rocket using a C engine making it woefully under-powered (at least with a C6, We'll see what a 24 mm C11 can do). Video of the first flight two years ago can be seen here https://www.youtube.com/watch?v=XSeQ2FDClKM, I don't have a video of the second flight, but it was much the same thing, only in the other direction (meaning south) and so stuck in the grass and dirt.

Well, now the question is, since I am using gap staging, even if it is a very small gap, (okay not really, the engines will be butted together, just not taped) is there information out there relating to the size of the vent hole compared to the total impulse of the engine in the booster? The only thing I have found is in Tim Van Mulligan's Model Rocket Design and Construction which just states that the vent hole should be 6.35mm in dia. or smaller if more than one vent. There is no mention of the total impulse of the engine for this size hole or even if it should be adjusted for larger engines.

Also, would it be more prudent to create two vent holes on either side of the body tube to prevent any unwanted pitching of the upper stage?

Thanks for your input.

#12 Re: Gap staging vent hole size

Posted: Tue, 20 Jun 17, 18:37 pm
by Rocket Babe
:lol:

#13 Re: Gap staging vent hole size

Posted: Wed, 21 Jun 17, 00:14 am
by bernomatic
May you have to rely on a 56k modem for a month.

#14 Re: Gap staging vent hole size

Posted: Wed, 21 Jun 17, 01:41 am
by tmacklin
Commander wrote:Much like TMacklin, I am also retrofitting my Renegade to a 24 mm engine booster. Mine was the recent Renegade D 2410 that I had built to the 2109 multi-stage version. Needless to say, I now see the error of my ways in trying to launch this rocket using a C engine making it woefully under-powered (at least with a C6, We'll see what a 24 mm C11 can do). Video of the first flight two years ago can be seen here https://www.youtube.com/watch?v=XSeQ2FDClKM, I don't have a video of the second flight, but it was much the same thing, only in the other direction (meaning south) and so stuck in the grass and dirt.

Well, now the question is, since I am using gap staging, even if it is a very small gap, (okay not really, the engines will be butted together, just not taped) is there information out there relating to the size of the vent hole compared to the total impulse of the engine in the booster? The only thing I have found is in Tim Van Mulligan's Model Rocket Design and Construction which just states that the vent hole should be 6.35mm in dia. or smaller if more than one vent. There is no mention of the total impulse of the engine for this size hole or even if it should be adjusted for larger engines.

Also, would it be more prudent to create two vent holes on either side of the body tube to prevent any unwanted pitching of the upper stage?

Thanks for your input.
I think you will find that either a C11-0 or D12-0 booster will give all the punch you need to achieve a stable high flight. In your video, the winds appeared to be quite stiff as indicated by the flags as well as the sound. Personally, I wouldn't fly the Renegade with anything much more than a 5 MPH wind. My Renegade is once again in dry dock and awaiting fin repairs due on the booster due to a hard landing on the last flight. And I have yet to apply the canopy form you sent me. I'm about through working on my son's building project but this shingles business makes detailed work like modeling unpleasant.

#15 Re: Gap staging vent hole size

Posted: Wed, 21 Jun 17, 17:36 pm
by Rocket Babe
bernomatic wrote:May you have to rely on a 56k modem for a month.


:lol: :lol: :lol: :lol: :lol: :lol: :lol: