Dual deploy question

[Kevin Huddleston]

I'm a newbie when it comes to dual deploy, but I have a bird (Hyperloc 835) dual deploy ready with all the electronics, etc. I have 2 questions:

(1) I'm using the Aerotech hardware with an H268R motor (not too high, but high enough to test the dual system). Should I just include the delay in the motor build (with no bp charge) or include some kind of cap I need to include to prevent motor thrust up into the rocket resulting in a cato?

(2) I am using shear pins. Two for the nosecone and 3 for the body section for the main. Though I have measured the appropriate amount of black power (about 1.5 grams each) for the respective volumes, should I add a bit more for shear pins?

Thanks!
(Having a hard time finding internet answers for all this...)

[chadrog]

If the delay is longer than your expected time to apogee, it's a good idea to use your motor eject as backup. If you need a longer delay, let me know. I'm a bit confused by the description of your shear pin setup, but that's irrellevant to the idea of ground testing - this is the best way to know your charges are the right volume. How do you have your pins set up for cardboard? What size shear pins are you using?

[Kevin Huddleston]

I have 2 shear pins (the tiny nylon screws that Tim sells) for the nosecone -- rogue chute. I have three of the same for the lower section for the main. I thought that since I'm using a dual deploy altimeter for the charges, I would not need to put the charge into the Aerotech motor build (except maybe the delay to plug the hole between the motor and the airframe?). Do I need to plug that Aerotech motor build with something else?

[Rex R]

well, if I'm reading this right...your setup is nose cone, forward chute bay(with drogue), av bay, rear chute bay(main), motor and fins...right?
use the delay element to 'plug' the motor case or get a plugged forward closure(think aerotech still wants you to use the delay grain).
rex

[chadrog]

Your setup is backwards from traditional. typically your drogue is in the lower section with the main under your cone - this makes it possible to use your motor as backup deployment. Your arrangement makes that impossible. Still curious what size pins your using and how you plan to cut them - cardboard alone will not.

[Kevin Huddleston]

Yes, it's backwards. Realized it too late. That said, I'm sure it's still workable (and have the altimeter wired accordingly). I was thinking that the delay should just be used as usual without the charge, of course. Just wanted to check. Thanks, guys!

[Kevin Huddleston]

Chad, I have thin brass plates inside the housing and nosecone to help with the cut. I had read that using CA would be enough, but I added the brass plates for good measure.

[chadrog]

Sounds like you're good to go, when are you planning to fly it?

[Kevin Huddleston]

Soon, I hope! Been rainy or too windy here for me to launch her. The field I use is compliant with HP guidelines, but just so. Can't have a day with 15 MPH winds and fly too high!

One of my original questions was about black powder. I have 1.5 grams for each charge (maybe .2 grams more than suggested for the volume). There are three shear pins for the main, two for the nose cone. Should I add any more black powder to ensure they will be cut?

[MadHatter]

The field I use is compliant with HP guidelines,

Do you have a FAA waiver for that location? The FAA requires a waiver if:

1). The fully assembled and loaded rocket weighs more than 3.3 lbs (1500 grams)

or...

2). The total propellent weight weighs more than 4.4 oz (125 grams) .

So if you exceed either of these values you must have a waiver, If you need one I can help you with the application process.

Mark
WOOSH Prez

[chadrog]

Zactly what I was thinking, bring it to Bong!

[Kevin Huddleston]

I'm thinking I should. This is the first 80 ounce rocket I've launched... and to my chagrin, I didn't think about the weight limit. I could apply for an FAA waver, but I'd rather just take her to Bong.

That brings up another question I have. When the regulation says that you must have 5 MILES of horizontal visual clearance for Class 2 birds, does that mean 5 miles of GROUND horizontal clearance (impossible for a significant percentage of the country), or just-above-horizon visibility (i.e., the sky just above horizon for the sake of lower flying aircraft)?

[MadHatter]

I'm thinking I should. This is the first 80 ounce rocket I've launched... and to my chagrin, I didn't think about the weight limit. I could apply for an FAA waver, but I'd rather just take her to Bong.

That brings up another question I have. When the regulation says that you must have 5 MILES of horizontal visual clearance for Class 2 birds, does that mean 5 miles of GROUND horizontal clearance (impossible for a significant percentage of the country), or just-above-horizon visibility (i.e., the sky just above horizon for the sake of lower flying aircraft)?

My understanding is straight line 5 miles from your launch area to the closest point of the airport.

[mwtoelle]

Also, you need to note that 5 miles means 5 Nautical miles (6076.12'), not 5 statute miles (5280'). The distances are reckoned as the crow files.

[chadrog]

Soon, I hope! Been rainy or too windy here for me to launch her. The field I use is compliant with HP guidelines, but just so. Can't have a day with 15 MPH winds and fly too high!

One of my original questions was about black powder. I have 1.5 grams for each charge (maybe .2 grams more than suggested for the volume). There are three shear pins for the main, two for the nose cone. Should I add any more black powder to ensure they will be cut?

Ground testing your charges in full flight configuration is the best way to confirm that your charges are adequate. It's a PITA, but it's worth the time in the end. Make sure you let your neighbors know what you're up to.

[Kevin Huddleston]

Ground testing your charges in full flight configuration is the best way to confirm that your charges are adequate. It's a PITA, but it's worth the time in the end. Make sure you let your neighbors know what you're up to.

You're right about the PITA. I have tested this without the shear pins, but not with. Dread rigging everything up, but maybe I should. As for the Class 2 requirements, #2 point just says "At any altitude where the horizontal visibility is less than five miles" so I wasn't sure exactly what that meant.

[chadrog]

Ever been to the Johnson Creek field? We have a launch there tomorrow, pack up your rockets and come on out!

[Kevin Huddleston]

Nope, never been tot he Johnson Creek launch. I have some medium-powered rockets aching to be launched! Maybe I will make it out there... depends on things at home. Wife and one of the kids are sick. Wish I could come to more launches. Bong is quite a ways from where we live. Wish there was a HP launch closer.

[chadrog]

That sucks. Happy fathers day anyway!