HPR noob trying to get a handle on dual deployment.

Yes they are needed if you want to make sure you don't do any looooong walks due to chute shake out at the top.

2 shearpins....# 2-256 are required.


By the way, sleds cut correctly for a 3in, don't need any tubes etc. They will self-lock into place when cut right. Then it can be easily attached to a 4 in sled for flying in that size rocket.

blackjack2564 said:

Yes they are needed if you want to make sure you don't do any looooong walks due to chute shake out at the top.

2 shearpins....# 2-256 are required.

Click to expand...

Just for the nose cone where the drogue chute is, or for the main tube section as well?

You are going to get many different answers to the same question. It will be up to you, to decide whom you are going to use for the answer. You will find 100 ways to do the same thing in rocketry.......all will work....some better.....some simple.....but all will work. There in lies the rub.

I use the K.I.S.S. principle. Less is always Mo better. Less glass, less glue,less hardware, less stress, less powder, less connections to go wrong = higher safer flights, on smaller motors. Or more altitude on same motor flown in a chopped version than stock.

In my case, shearpins just for the NC. I have never had drag separation because every rocket I have built has a heavier fincan than payload.

Trust me when I say, once I start the build on the 3in DS, every possible question you could come up with.....will be covered.

That is all. [M.A.S.H.] lol

Green Jello said:

Just for the nose cone where the drogue chute is, or for the main tube section as well?

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Just the nose cone I think.....basically you don't want the nose cone coming out and pulling the chute at apogee when you only want the drogue to come out.

Green Jello said:

Just smear it all on the outside of the tube? I'd love to see some pics on this.

Click to expand...

I just used 3/16" launch lugs from BMS on mine. They sell launch lug stock in 34" lengths. I did sand the glassine off of them before I applied the epoxy.

https://www.rocketryforum.com/showthread.php?44764-Mile-High-build-thread&p=429861#post429861

Green Jello said:

Just for the nose cone where the drogue chute is, or for the main tube section as well?

Click to expand...

I think the main chute is typicaly stored between the Avionics bay, and the nose cone... "payload bay". Yes, you want atleast 2 #2-256 nylon shear pins. I would use 2 grams of BP. and 15' -20' of kevlar cord.

The drouge separation occurs from "fincan" and the motor tube fin assembly, and coupler at the avionics bay. I use shear pins on my sons 2.1" darkstar, but my wife does not use shear pins on her Extreme. She flew her extreme for her L2 certificaiton on an AT L2200. Hit mach 1.3 nearish, and no drag separation...
it makes sense for me because her extreme fits to gether better than the 2.1 does. if they fall apart by holding them up by the part on top. shear pin them. You want them to be snugg fit, and I dont like tape. I trust a nylon pin way before I do masking tape. the 2.1" rocket is fat tubbed where the coupler fits, and is loosy-goosey so i just use 1 pin to "hold them togheter"

Green Jello said:

Just for the nose cone where the drogue chute is, or for the main tube section as well?

Click to expand...

With my Milestone, I won't use shear pins in the lower drogue section. They're not necessary. What you don't want to happen is the main chute deploying too soon. So I'll use three 2-56 nylon screws through the upper body tube into the av-bay. During ground testing, I'll determine how much black powder is necessary to break the pins and blow out the laundry.

As for shear pin alternatives, I've heard of pieces of styrene rod, push in plastic rivets, and even pieces of masking tape.

qquake2k said:

You can put the main in either section. I'll be putting my main in the upper section and the drogue in the lower section, because I'll be using motor eject as backup for the apogee (drogue) charge.

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you can, however, i wouldnt advise that.
(take that for what its worth...)

but, the drouge comming from the nose cone end, means you have a higher probabilty of a ballistic shaped recovery... whereas separating in the center where the sections are much closer matched mass wise, you will tend to flat spin more. By placing the drouge near the main payload, at the avbay, you assure your rocket doesnt come down through your main as it deploys as well.

Drouge deploy is very much "to each his own" but some tumble when they fail, and others come in ballistic... separating in the center at apogee, leans toward tumble, and at the nose leans toward ballistic.

ClayD said:

you can, however, i wouldnt advise that.
(take that for what its worth...)

but, the drouge comming from the nose cone end, means you have a higher probabilty of a ballistic shaped recovery... whereas separating in the center where the sections are much closer matched mass wise, you will tend to flat spin more. By placing the drouge near the main payload, at the avbay, you assure your rocket doesnt come down through your main as it deploys as well.

Drouge deploy is very much "to each his own" but some tumble when they fail, and others come in ballistic... separating in the center at apogee, leans toward tumble, and at the nose leans toward ballistic.

Click to expand...

Mine will be separating at the center. Both sections will separate at the av-bay.

qquake2k said:

Mine will be separating at the center. Both sections will separate at the av-bay.

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that should work.

just remember, when its coming down, you want your main paracute falling above the rocket. that way when it is deployed the rocket doesnt fall through the main. it parachute is ejected out away from the rocket.

qquake2k said:

As for shear pin alternatives, I've heard of pieces of styrene rod, push in plastic rivets, and even pieces of masking tape.

Click to expand...

if you use nylon in your rocket, and have it sized for nylon, styrene wont be sufficient. its weaker. also, hard to find where fits well in holes sized for screws. I shook a main once when i substituted styrene for nylon.

I have a question about seperation(not from my wife, rockets): What is the rule for when you want to drop drogueless, both parts weigh nearly the same so that they fall about the same rate, and flat(hope that makes sense). I don't want the nose to fall below the rocket, and wouldn't either to fall nose or tail down, but more or less in a flat free fall.
Really want to get Mark Canepa's book High Power Rocketry(2)....I'm sure it explains alot of this stuff to a great deal as well.

Green Jello said:

I was out killing time at lunch and ended up buying some stuff.

From Home Depot, I got some 1/4" threaded rod and nuts. I also picked up a couple 1/2" copper pipe couplers that looked like they might be perfect for the charges.

Then I was at Radio Shack and I picked up a switch and the Euro Terminals.

Now I just placed an order at Aerocon for the following:

https://aeroconsystems.com/cart/flight-avionics/nylon-9-volt-battery-holder/
https://aeroconsystems.com/cart/electronics/black-powder-ejection-charge-holders/
https://aeroconsystems.com/cart/switches/through-mount-slotted-switch/
https://aeroconsystems.com/cart/lau...2-56-nylon-screws-for-shear-pin-applications/

On top of that, I just got a text from my father in law saying he has a can of FFFFG in his possession for me. Weeeee!

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Depending how large your av bay is 1/4-20 threaded rod might be a bit overkill. My 1.6 and 2.1 av bays use much smaller threaded rod which I find at HD or Lowes or the local RC hobby shop. 8-32 or 10-24 should be fine for most applications 3" in diameter or less.

Ounces make pounds.

Green Jello said:

I was out killing time at lunch and ended up buying some stuff.

From Home Depot, I got some 1/4" threaded rod and nuts. I also picked up a couple 1/2" copper pipe couplers that looked like they might be perfect for the charges.

Then I was at Radio Shack and I picked up a switch and the Euro Terminals.

Now I just placed an order at Aerocon for the following:

https://aeroconsystems.com/cart/flight-avionics/nylon-9-volt-battery-holder/
https://aeroconsystems.com/cart/electronics/black-powder-ejection-charge-holders/
https://aeroconsystems.com/cart/switches/through-mount-slotted-switch/
https://aeroconsystems.com/cart/lau...2-56-nylon-screws-for-shear-pin-applications/

On top of that, I just got a text from my father in law saying he has a can of FFFFG in his possession for me. Weeeee!

Click to expand...

Sounds like fun! I love hardware! Question though - why did you get copper pipe couplers instead of caps? With a cap, you can attach it to the end of av-bay, and you only have to seal one end of it.

o1d_dude said:

Depending how large your av bay is 1/4-20 threaded rod might be a bit overkill. My 1.6 and 2.1 av bays use much smaller threaded rod which I find at HD or Lowes or the local RC hobby shop. 8-32 or 10-24 should be fine for most applications 3" in diameter or less.

Ounces make pounds.

Click to expand...

I used 10-24 rod in my Milestone's av-bay.

qquake2k said:

I used 10-24 rod in my Milestone's av-bay.

Click to expand...

Yeah, I'll get smaller ones. Thanks.

qquake2k said:

Sounds like fun! I love hardware! Question though - why did you get copper pipe couplers instead of caps? With a cap, you can attach it to the end of av-bay, and you only have to seal one end of it.

Click to expand...

Oh....I was going to use the centerfuge things like you showed. I just picked up the couplers because they were $0.45 each and I thought they might be a good holder for the caps and direct the blast charge.

I wish you good luck on your first Dual Deployment.

Green Jello said:

Oh....I was going to use the centerfuge things like you showed. I just picked up the couplers because they were $0.45 each and I thought they might be a good holder for the caps and direct the blast charge.

Click to expand...

I'm going to mount some brass strips on mine sticking up from each end of the av-bay, then zip tie the charge tubes to them. That way they'll be pointed in the right direction (not sure that matters), but mostly they won't be flopping around during the flight.

Green Jello said:

How are the forged eye bolts at Rocketry Warehouse? What sort of lb. rating is necessary for a 3" glass rocket?

https://rocketrywarehouse.com/index.php?cPath=32_50

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The forged eyebolts from McMaster-Carr and Rocketry Warehouse both have a 500lb working load. I don't know what the working load of bent eyebolts is, but it has to be much less. There is a website somewhere with breaking tests of a lot of high power components, but I don't know where it is. Maybe someone will chime in with it.

How heavy will your 3" glass rocket be? I think if it were me, I'd used forged eyebolts just to be on the safe side. Or if you have room, you could use u-bolts. Home Depot has some fairly compact 1/4", like the one I used on Milestone. Of course, it's only an issue on the forward motor mount centering ring. You should have plenty of room for u-bolts in the end caps of a 3" av-bay.

https://www.rocketryforum.com/showthread.php?44764-Mile-High-build-thread&p=436039#post436039

https://www.rocketryforum.com/showthread.php?44764-Mile-High-build-thread&p=432308#post432308

Green Jello said:

I'm just gonna keep dumping questions here as they come to me....

When making the AV bay....is it common to glue one of the bulk plates on and leave the other removable, or leave them both removable?

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Keep on asking! I don't know about other people, but I wouldn't glue the plate to the av-bay. I want to have access to both sides of it, in case I need to replace or change something, like the eyebolt, terminal strip, etc.

I test mine by using xmas tree lights instead of BP charges.

bill2654 said:

I test mine by using xmas tree lights instead of BP charges.

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No, I get that....I mean, how do you simulate the altitude triggers? Is the only way with a vacuum chamber?

I completley assemble my av-bay (with the Xmas lights) and then turn on the altimeter and when it beeps out continuity then plug all but one of the vent holes and suck real hard on the open vent hole. Your apogee light will blink first then your main will blink.