HED vs Traditional Dual Deploy

[bad_idea]

I'm really interested in the electronic side of this hobby. I'd like to be able to port as much into the LPR/small field area as possible, as it increases accessibility to the "tech-ier" stuff for the kids, and the better we can keep rockets on the field and out of the trees. But I'm a ways off from doing anything substantial in that area. Criminee, just having to loft the battery needed to do this stuff might take a fellow right out of LPR!

Check out the Eggtimer Apogee. It's not dual deploy, but it's light and uses a lightweight battery, and it will at least free you from the tyranny of motor ejection. Assembly required, but there are folks who will solder it for you for a small fee if you like. Even smaller, though more expensive, is Adrel's DeployMax. And there are a few other tiny deployment altimeters out there.

 

[Blast it Tom!]

Check out the Eggtimer Apogee. It's not dual deploy, but it's light and uses a lightweight battery, and it will at least free you from the tyranny of motor ejection. Assembly required, but there are folks who will solder it for you for a small fee if you like. Even smaller, though more expensive, is Adrel's DeployMax. And there are a few other tiny deployment altimeters out there.

Oh, okay. So as usual the community has been there already!
So that got me to thinking... if you aren't going to rely on motor ejection, uh... what sort of motors do you use? There's not a great variety of plugged motors out there.

Then I'll stop derailing!

 

[Titan II]

Oh, okay. So as usual the community has been there already!
So that got me to thinking... if you aren't going to rely on motor ejection, uh... what sort of motors do you use? There's mot a great variety of plugged motors out there.

Then I'll stop derailing!

If I understand your question right...you do not need a plugged motor. You just have the motor delay set longer than the time you are using for electronic ejection. That also gives you another layer of protection.

 

[jmasterj]

Oh, okay. So as usual the community has been there already!
So that got me to thinking... if you aren't going to rely on motor ejection, uh... what sort of motors do you use? There's mot a great variety of plugged motors out there.

Then I'll stop derailing!

You just don't add the BP for reloads or remove it for DMS/CTI motors.

 

[bad_idea]

if you aren't going to rely on motor ejection, uh... what sort of motors do you use? There's mot a great variety of plugged motors out there.

Then I'll stop derailing!

Many reload cases have plugged forward closures (either standard or optional), but for those which don't or for disposable composite motors, you can dump the ejection charge and plug the ejection well with wadding and tape it over. Many experienced flyers swear by plugging -0 blackpowder motors with wadding and tape too, but I've had problems with that and figure to do some ground testing before I try it again. You can also vent an ejection charge, either out of the side of the rocket or out the back, which is useful for blackpowder motors without a -0 or -P variant.

As @Titan II says, you can fly electronics with a motor delay backup if you like. That doesn't address chuffs or other causes of short-burning delays, but with newer motors - especially "instant-on" propellants like Blue Thunder - and reliable starters, the former may be of less concern. As with many things in rocketry, it's a tradeoff of risks.

As you say, this is a derail. Would be good as a new topic though.

 

[Adrian A]

Chuffing motors is something I'm just learning about, so believe me I'm keeping my little Aerotech RMS 18/20 reloads sealed and sealed again until I might have a chance to use them! Your scenario makes 'way too much sense.

I'm really interested in the electronic side of this hobby. I'd like to be able to port as much into the LPR/small field area as possible, as it increases accessibility to the "tech-ier" stuff for the kids, and the better we can keep rockets on the field and out of the trees. But I'm a ways off from doing anything substantial in that area. Criminee, just having to loft the battery needed to do this stuff might take a fellow right out of LPR!

The Featherweight electronics products are designed to be used with small, lightweight batteries. A Blue Raven plus its battery together weigh 11 grams and fits into a 24mm (BT50) tube. Compare that to a typical 9V battery which is about 45 grams.

 

[jmasterj]

I would love to see some examples of the main-side recovery setup. I'm finally getting to that portion of my first HED build and I'm not sure I understand the best practices.

 

[86mustang408w]

Why do you want any of that? More stuff to go wrong.

Do you want the main chute to come out 42,000 feet? It goes 17 miles....

 

[David Schwantz]

I would love to see some examples of the main-side recovery setup. I'm finally getting to that portion of my first HED build and I'm not sure I understand the best practices.

For the most part it is just like DD in the payload section. You attach the shock cord to a mount in the NC, eye bolt in the tip, and the other end attached to the Avbay u bolt. With the chute attached nearer the NC than the Avbay. I do not use a switch band on mine, so the pull pin switch is in the joint between the NC and main body tube. And you stuff the chute in the NC.

 

[jmasterj]

For the most part it is just like DD in the payload section. You attach the shock cord to a mount in the NC, eye bolt in the tip, and the other end attached to the Avbay u bolt. With the chute attached nearer the NC than the Avbay. I do not use a switch band on mine, so the pull pin switch is in the joint between the NC and main body tube. And you stuff the chute in the NC.

So you use a third loop in your main harness?

 

[David Schwantz]

I do. Just like I do in normal DD. It is a couple feet down from the NC. That way the NC dangles above the booster section.