View Full Version : Help with DV's

05-18-2009, 02:08 AM
Any suggestions or techniques to reduce deployment velocity (DV) numbers?

... Bill

05-18-2009, 07:10 AM
Depends upon where the rocket is in flight in relationship to the ejection charge event..Is the rocket still cooking along in the upward motion when the event happens to get the high number? If so, try a longer delay, if that doesn't work, then adding nose weight might help..Is the rocket in the downward phase, try a shorter delay, if that doesn't work, work on trying to make the rocket lighter so it can coast some more but making sure it is still stable..

Sometimes, there will be some designs that just will NOT work with some motors no matter what you do..

These are just a couple of 'SWAGs' but we could really use some more information to make more valid suggestions..

James Pierson
05-18-2009, 07:23 PM
Any suggestions or techniques to reduce deployment velocity (DV) numbers?

... Bill

Bill you do have a few choices and Jon is on the money too.

-Make it heavier or make it lighter with fin thickness, BNC size, CR thickness,
-More drag of less drag with fin side etc..
Usually making the design just a little longer helps the CG-CP ratio and then adjust things.
-Change engine size, 13mm-18mm-24mm etc..

Without seeing the design its hard to tell. If it is build you still can adjust the Dv's usaually by adding more drag like mid or tip fins.

I have notice a large difference with Rocksim if the launch conditions are adjusted. Rod angle to wind and increasing the wind play a role with the DV's much more than I ever thought :confused: .

Hope this helps, JP.

James Pierson
NAR# 77907

05-19-2009, 05:04 PM
Jon and James,

Thanks for the suggestions. I have been recently working up some designs in Rocksim to submit to Craig for Barclone, but I seem to consistently run into the problem of high DV's. I'm going to try some of your suggestions and see if I can get the numbers looking better.


... Bill

05-19-2009, 07:43 PM

What I'll add here first is an observation. As you work with RockSim more and more, you will slowly get a feel for what works and what doesn't. As you watch the Dv numbers on your designs get better, you'll start noticing proportions, or ratios of how much of this works with how long of that, and your designs will begin reflecting it.

It never gets 'easy', in the sense that you'll never reach a point where you never get one wrong; but it will get 'easier', in that you'll have more designs that fall into the ranges you want them to than designs that don't.

As for advice, the only thing I can offer of value is "Practice, practice, practice". You have to come up with something each day, like a writer has to write a few pages each day, to understand this process. Even if the design you create is pure garbage, you still have to 'get it out of your system' in order to move on to something that works. Trust me on that one -- I've got reams of designs that will never fly because the proportions are totally whacked, but I had to put them into a RKT file just to be able to set them aside.

Some may think I'm kidding about my challenges to the BARCLONE core team, trying to get them into designing at least one model each day, but I'm not. It's a tough challenge at times, and I don't always follow my own counsel. But when I get 'on a roll' with designing, it really seems to flow more freely when I'm consistent with the process. And the good designs wil far outnumber the bad ones.