Decent rates for dual deploy?

[BsSmith]

I'm starting look at my options for parachutes for my Talon 3. I will be using dual deploy with a 24" parasheet as a drouge. I'm looking at weight charts to get the right size chute for a 15-20fps decent rate. How much does the drouge chute effect the decent rate? Do I add the size of the drouge to the size of the main on the chart? I am clueless.

 

[FROB]

In my limited experience, the drogue drag is relatively insignificant once the main chute is inflated.

 

[droopy]

Having done quite a few DD's with several, umm, learning opportunities, I'd say don't count the drogue at all when trying to figure the descent rate while under the main. I mean, is it gonna hurt if you're a few fps SLOWER than you intended?

just my $0.01 worth. (hate the deflationary pressures during recessions...)

John
TRA Lvl 3

 

[kandsrockets]

Do not count the drogue for sizing your main. Also make sure your drogue is not to big. I had a rocket that I had a drogue chute that was larger than I needed (wrong chute packed in the wrong bag) and when the main came out it never inflated because the rocket was dropping to slow. I like to keep my drogue descent rate over 60 fps. Also if you have the space use a deployment bag for your main.

 

[kramer714]

On my larger rockets, I have begun using an over sized drogue, still a good clip but some chance of survival on a single chute. For example on a 50 lb rocket I used a 6 foot drogue and a 12 foot main.

To calculate the main size, I figure out what weight of rocket will the drogue only support at a good final speed, and then size the main for the remaining weight of the rocket (total weight minus weight of 'drouge support').

Funny thing, on smaller rockets (10 lb or lower) I have gone drouge-less and just put in a healthy length of TN shock cord.

 

[JDcluster]

I really don't use drogue anymore. I haven't had any good luck using them other than maybe once or twice. I do believe ( in some cases) your rocket will fall faster with a drogue than without one. Most of my rockets fall drogueless around 60-80fps.

On most of my rockets, I pop the chute around 800 ft.


JD

 

[Pantherjon]

I am also another in the drogueless camp..Has worked fine so far on all my DD launches..Can't discount having a LONG cord between the 2 sections and good weight distribution..You will want the aft section to be a bit heavier then the front section so when the main deploys the bottom section doesn't fall thru the chute and ruin your day..

 

[MarkM]

I'm in the "mostly drogueless" camp. Only two rockets do I fly with a drogue. One is my 4" fiberglass Talon because of the large weight difference between the aft section and the rest of the rocket (the long tube and large G10 main fins are responsible...not much I could do about that). Most of my other rockets have very even weight distribution and I've had no problems flying without a drogue on these.

The other rocket I fly with a drogue is my 6" L3 Bandit upscale. Again, a heavy rocket with a fairly heavy fin can. I use a small drogue just for a little stability.

Most of my flights I pop the main at 600 ft. Even at this altitude, there's still enough time for the chute to inflate fully and safely recover the rocket not to mention less drift. I pop the chute on my L3 rocket at 1200ft just to be sure the large main has enough time to inflate. I could probably pop it at 1000ft but a rocket this large I like erroring on the conservative side.

 

[BsSmith]

One is my 4" fiberglass Talon because of the large weight difference between the aft section and the rest of the rocket (the long tube and large G10 main fins are responsible...not much I could do about that).

I am guessing that the same would apply for a 3" Talon too? The fin can is very heavy and I am using the stock 15' kevlar cords with the 5' cord to parachutes. I put the Fireball in the booster tube.

 

[FROB]

Up to now i've always used a drogue when doing dual deploy- and successfully except once i miswired my apogee charges and the drogue never fired.
I'll probably try drogue-less this season at least once, to save some weight on an altitude record attempt or similar launch.
I always use a very small drogue for the airframe. More than any other reason, its purpose is to pull the main chute compartment above the booster and pointing in a safe direction so it deploys in a predictable and tangle-free manner when its time. It also help a spinning rocket to stop spinning by the time the main is ready to deploy, even if the drogue get a bit twisted up in the process.