Talk me out of this idea... Or into it o_O

[FlyingMonkey]

Due to a failed attempt at using Kevlar for a shock cord (it wasn't Kevlar) my Der Red Max landed tube first into the ground. I'm pretty sure I could get away with cutting an inch off the end of the tube and it still fly but then I had an idea.
I was thinking I could cut off the 1" and with the help of a coupler add a clear BT-60 payload tube maybe 3-4 inches long.

But I've never built a payload rocket and I have no idea how to determine how it will fly on the recommend engines. The rocket isn't a high flyer as it is.

Hoping someone can talk some sense into me or point me in the right direction. Thanks!

 

[K'Tesh]

Due to a failed attempt at using Kevlar for a shock cord (it wasn't Kevlar) my Der Red Max landed tube first into the ground. I'm pretty sure I could get away with cutting an inch off the end of the tube and it still fly but then I had an idea.
I was thinking I could cut off the 1" and with the help of a coupler add a clear BT-60 payload tube maybe 3-4 inches long.

But I've never built a payload rocket and I have no idea how to determine how it will fly on the recommend engines. The rocket isn't a high flyer as it is.

Hoping someone can talk some sense into me or point me in the right direction. Thanks!

It should work...

You could modify a .ork file of the DRM to reflect the changes you are thinking of, then check stability and motor selection.

View attachment Estes Der Red Max (unfinished).ork

 

[FlyingMonkey]

Ok, umm, did I mention this is like my 2nd rocket? Lol I have no idea what to do with an .ork file or how that allows me to check stability.

Looks like I better get the google-ing

 

[K'Tesh]

You can download it here... https://openrocket.sourceforge.net/

Once you download it, open the .jar file (the program), and from there you can open downloaded RocSim (.rkt) and OpenRocket/OR (.ork) files.

I have tutorials on how to use it, but I've just gotten back to Yantai after spending two weeks touring China (and 9 hours in Pudong International Airport (Shanghai). I'm too beat to do much right now other than eat, sleep, and get ready for work on Saturday.

https://www.rocketryforum.com/showthread.php?123564-K-Tesh-s-OpenRocket-files

https://www.rocketryforum.com/showthread.php?62884-K-Tesh-s-OpenRocket-Tutorials

 

[Scott_650]

An inch off DRM shouldn't cause any stability problems - play around with the simulation per K'tesh's suggestion and I think you'll see that. if you're really concerned add a little weight to the nose - wouldn't take much - and do your first post-repair flight on day with as little wind as possible. DRM is a very forgiving design for a "short-ish, fat-ish" rocket.

 

[Scott_650]

Oops! I just re-read your original post - ADDING some length to DRM shouldn't cause any problems, as long as you're not talking about a couple of feet or something, with the stock nose weight. I think you'll enjoy fiddling around with OpenRocket - it's addicting! - and see that a longer DRM will simulate just fine.

 

[Woody's Workshop]

Go for I'd say. It would be nice if you could get some opaque red plastic tubing for the payload section.
But you will need a solid balsa or plastic coupler as you don't want ejection charge gasses going into the payload section.
The thing with kevlar or other not stretching (or even stretching) shock cords is the length.
Stock shock cords are way too short. There are many thread here that show the where's, if's, when's & especially the why's of using a much long shock cord.
But experience is also a great teacher.
Good luck with your mod!

 

[dford]

Rocketry became a bazillion times more fun once I began playing with openrocket. So much I'm considering purchasing rocsim or something similar.
Your own creation on computer, constructing it in real life is so so much more rewarding. The learning curve becomes much broader as well.

 

[Forever_Metal]

OR is pretty good... for free!

I like doing it so much (Thanks KT :wink:, well maybe I should curse at you too.. :kill, that I do all of my builds in OR using the original weights and dimensions before i lay glue; now if i could only figure out the decal thing...

Once i finish it, I update the overall weight and re-run the sims to see how overbuilt it is... But it should get you close...

fm

 

[K'Tesh]

OR is pretty good... for free!

I like doing it so much (Thanks KT :wink:, well maybe I should curse at you too.. :kill, that I do all of my builds in OR using the original weights and dimensions before i lay glue; now if i could only figure out the decal thing...

Once i finish it, I update the overall weight and re-run the sims to see how overbuilt it is... But it should get you close...

fm

Decal thing? You need neal_w's help for that...

https://www.rocketryforum.com/showt...t-a-not-so-quick-and-fairly-complete-tutorial

 

[FlyingMonkey]

This program exceeds what my tiny lil brain can handle. From what I can tell on the C6-5 I would lose up to 100 ft when adding about 4" of payload tube and misc items.

What I cant figure out is how to gain that back. Maybe someone smarter than I can tell me which motor I can use that will fit, increase altitude back to the 650-800ft mark, and have the correct delay. I entered in various motors and get over 1k ft and I dont know how to choose delay time.

 

[dhbarr]

This program exceeds what my tiny lil brain can handle. From what I can tell on the C6-5 I would lose up to 100 ft when adding about 4" of payload tube and misc items.

What I cant figure out is how to gain that back. Maybe someone smarter than I can tell me which motor I can use that will fit, increase altitude back to the 650-800ft mark, and have the correct delay. I entered in various motors and get over 1k ft and I dont know how to choose delay time.

Switch over to the simulation tab, run all of them. There should be a column which gives you an optimal delay estimate. Go back and pick the closest appropriate delay.