Dual deploy

[RocketMonkey]

Just curious as to how you set up your DD's
Drouge on top or bottom?

 

[DAllen]

I put the drogue in the lower section so I have the option of using motor deploy at/near apogee. Plus, if the drogue is in the lower section then it's easier to get the forward and aft sections to fall evenly. I like to the have the forward section a touch higher or the same height as the aft section when the main is deployed to avoid a chute tangle.

-Dave

 

[troj]

Something to consider, if you put the drogue on top and the main underneath...

With the drogue putting load on the separation point where the main is, if you get a hard opening of the drogue, you're much more likely to dump the main earlier than you want to.

Loads generated by opening shock can be tremendous -- just ask a skydiver who's had a hard deployment what it's like. It leaves bruises.

On rockets, it can lead to damaged recovery systems or rockets, or if the drogue puts the load on the main separation point, it can cause the main to come out early.

-Kevin

 

[Diosces]

I put the drogue in the lower section so I have the option of using motor deploy at/near apogee. Plus, if the drogue is in the lower section then it's easier to get the forward and aft sections to fall evenly. I like to the have the forward section a touch higher or the same height as the aft section when the main is deployed to avoid a chute tangle.

-Dave

Something to consider, if you put the drogue on top and the main underneath...

With the drogue putting load on the separation point where the main is, if you get a hard opening of the drogue, you're much more likely to dump the main earlier than you want to.

Loads generated by opening shock can be tremendous -- just ask a skydiver who's had a hard deployment what it's like. It leaves bruises.

On rockets, it can lead to damaged recovery systems or rockets, or if the drogue puts the load on the main separation point, it can cause the main to come out early.

-Kevin

What they both said. Main forward for my DD rockets.

 

[sylvie369]

I don't know that I've ever seen consensus on TRF before.
I'll take 20 votes before the first dissenter.

 

[TWRackers]

Both on top; I have an ARRD, so mine only separates at one point.

 

[stickershock23]

I always put main on top. then you can use motor eject as a back up for your drogue, use an extra long delay. If for some reason electronics fail. at least you get the drogue out. much better than a lakestake.

Both on top; I have an ARRD, so mine only separates at one point.

I use my "tether" (similar to an AARD) on my main to release 1/2 of the shroud lines about 2 seconds after reaching the ground. that way the wind does not drag your rocket across the lakebed.

 

[BB-ROCK]

I would agreed with stickershock, use your motor ejection as a back up just in case your altimeter fails to deploy. You want to see rocket deploy at apogee and if it start to come nose down at least you have a motor ejection. Just remember put in your BP when your build motor.

 

[Rocketjunkie]

I would agreed with stickershock, use your motor ejection as a back up just in case your altimeter fails to deploy. You want to see rocket deploy at apogee and if it start to come nose down at least you have a motor ejection. Just remember put in your BP when your build motor.

Once you're used to electronics, you are much more likely to have a premature ejection or blowby than electronics failure. Use a plugged closure and eliminate this failure mode. If you want a backup, use a second electronic deployment unit.

 

[troj]

then you can use motor eject as a back up for your drogue, use an extra long delay. If for some reason electronics fail. at least you get the drogue out. much better than a lakestake.

There's a risk that goes along with motor backup -- what happens if you get an early ejection or blowby?

Plugged forward closures don't have this; I know several folks who've had failures on dual-deploy flights because the motor misbehaved.

At the same time, if the electronics fail and you don't have things setup for motor ejection, you've got a problem.

Pros and cons....

-Kevin

 

[rocketcrazee]

Niether I always use main on the top,with chute at the top and nose cone a third way down shock cord. Do not use a drogue on the bottom I just let it tumble after apogee

 

[BB-ROCK]

Once you're used to electronics, you are much more likely to have a premature ejection or blowby than electronics failure. Use a plugged closure and eliminate this failure mode. If you want a backup, use a second electronic deployment unit.

what is the difference with between electronics and non electronics?

First time started to use altimeter and old rocketeer told me use a motor ejection as a back up just make sure put it on a longest delay. I just wanna to learn how it works and all do's and don't. Now I fly 2 or 3 altimeters and timers in my larger rockects no motor ejection. I could see all the pro's and cons about motor ejection but I never had problem with premature or blowby. But at the end it all depends on the person how they want to set it up they will learn how to use it.

 

[stickershock23]

There's a risk that goes along with motor backup -- what happens if you get an early ejection or blowby?

Plugged forward closures don't have this; I know several folks who've had failures on dual-deploy flights because the motor misbehaved.

At the same time, if the electronics fail and you don't have things setup for motor ejection, you've got a problem.

Pros and cons....

-Kevin

I agree, BUT I also have to say, If you assemble your motor correct, Blowby will never happen. When I use motor back up I use the longest delay that will fit. this is typically 15+ seconds. so early deploy is pretty rare too.
again thats just my opinion.

Edit: Honestly, I have had more electronics failures because I forgot to arm them! (DOH) thank god for motor back up... You say how does that happen? Last time, I had a missfire, went to the pad put in a second igniter... still nothing (motor had been assembled for weeks prior) went out disarmed, pulled it, dissassembled the motor, scratched the grains. reset it on the pad. about apogee my mind said "DOH ELECTRONICS" I use remove before flight tags, but when I pulled it off the pad I never put the tag back on... once again, thank god for motor backup.

 

[troj]

I agree, BUT I also have to say, If you assemble your motor correct, Blowby will never happen. When I use motor back up I use the longest delay that will fit. this is typically 15+ seconds. so early deploy is pretty rare too.
again thats just my opinion.

I'd say a significant percentage of the blowbly problems are due to incorrect motor assembly. But not always.

Edit: Honestly, I have had more electronics failures because I forgot to arm them!

You're not the first person, and you certainly won't be the last.

-Kevin

 

[stickershock23]

I'd say a significant percentage of the blowbly problems are due to incorrect motor assembly. But not always.

-Kevin

Yeah, thats what I was trying to say. Other failures can damaged o-rings, voids in delay grains, delamination of a delay grain. and the most common, putting the spacer and delay in backwards (thats a guaranteed fail!) and acts of God. (those failures that you never can figure out why).. LOL

I will say that forward closures failures, have to be the one I see more than any other failure.

All in All when I duel deploy, and I dont use motor back up, thats when it seems I mess up the electronics...That Murphy guy is a S.O.B.

 

[Pantherjon]

.That Murphy guy is a S.O.B.

Yeah he sure can be a pain in the backside! Like when you get REAL comfortable and almost always fly dual deploy and then decide to fly a rocket single deploy with motor ejection- better remember to load the BP!

 

[stickershock23]

I think the dumbest mistake I have made is not connecting the quick link to the electronics bay... there are just to many things that can go wrong.

 

[mattvd]

Related question . . . with the main in the top . . .

Do you keep the e-bay connected to the payload tube and pop the main chute out the nosecone? Booster--drogue--ebay with payload airframe--main--nosecone.

Or, do you separate at both ends of the e-bay? Booster--drogue--ebay only--main--payload airframe with nosecone fixed.

I have seen both . . . is one better than the other?

 

[madmax]

I have seen both, however I don't like drilling into my ebay to put in shear pins. Something about it just doesn't seem right.

Personally I fly with zipperless fin cans when I can so my ebay is housed inside the upper airframe at all times.

 

[Pantherjon]

Related question . . . with the main in the top . . .

Do you keep the e-bay connected to the payload tube and pop the main chute out the nosecone? Booster--drogue--ebay with payload airframe--main--nosecone.

Or, do you separate at both ends of the e-bay? Booster--drogue--ebay only--main--payload airframe with nosecone fixed.

I have seen both . . . is one better than the other?

The first way is how I do it..How I was taught/shown when I first got into high power..I use the coupler as my e-bay, and use nylon pop rivets to attach the e-bay to the payload tube..

 

[mattvd]

The first way is how I do it..How I was taught/shown when I first got into high power..I use the coupler as my e-bay, and use nylon pop rivets to attach the e-bay to the payload tube..

Thanks. That's how I have it set up.

 

[Mike Di Venti]

I put the drogue in the lower section so I have the option of using motor deploy at/near apogee. Plus, if the drogue is in the lower section then it's easier to get the forward and aft sections to fall evenly. I like to the have the forward section a touch higher or the same height as the aft section when the main is deployed to avoid a chute tangle.

-Dave

What he said!
Lesser chance of the motor can falling through the 'chute when it opens.

 

[SpartaChris]

I do main in top and drogue lower for the reason that you also increase the risk of getting tangled or preventing the main from inflating the other way.

I connect my drogue relatively close to the separation point so the two halves of the rocket will be spread apart as it descends. This also helps keep the main section higher than the booster section, so when the main blows, it's blowing higher than the booster.

If you have the drogue up top at the nose, when the main opens, you increase the risk of it wrapping around the rocket as it tries to inflate.