Where to split my dual deploy

[Nick Hutton]

I’ve built a Loc High-Tec I got off Big_Red_Daddy on a package and I’m going to make it a dual deploy capable rocket. I’ve built the stock payload section and drilled it for rivets to hold the nose come on the payload section. I’ve also tip to tip glassed the fin can to make it Level 2 capable hopefully.

I’ve cut another section of Loc 2.56 Tube as a longer payload tube to contain a main and put together an AV bay with a switch band. It’s got an egg timer quantum I built on Sunday (shout out to the awesome kits at egg timer - in two weeks I’ve made a quark, an LCD receiver and GPS upgrade and a Tracker as well as the Quantum, and they all work perfectly!).

My question is, do I construct it so that the payload tube is riveted to the nose cone and when fully deployed the AV bay is supended between the two;

Or do I drill the AV bay so that it’s riveted to the payload tube and the nose blows off to release the main?

Any major advantages/disadvantages of either. Just realised I can fit a 1080 Aerotech case in this and put it up on a J570 to hit Mach 1.4. Does standard LOC tubing cope with that?

 

[tim cubbedge]

I’ve seen it done both ways. Me personally, I prefer to attach rivets to AV bay & pop the NC. That’s probably more common too.

 

[Eric]

I always rivet, screw or friction fit the payload tube to the coupler and blow the nose cone off. Not sure if there is an advantage either way.

And I have seen LOC tube handle a J825r just fine. I would only worry about strong enough fin connection. LOC tubes are strong.

 

[David Schwantz]

I also blow the NC off. Only difference is that I do not use rivets. I use 2-56 steel screws with a ply backer and blind nut in the tube.

 

[SammyD]

I use plastic reusable rivets to secure my payload section to my AV Bay. At apogee, the apogee charge separates the AV Bay, Payload Section, and the Nosecone (as a unit) from the Booster section. They remain tethered together in freefall until the main Parachute is deployed by ejecting the Nosecone at a set altitude near the ground.

To secure the Nosecone to the Payload section (where the chute is located), I use 2-56 nylon screws. To secure the Payload Section to the AV Bay, I use, as mentioned above, nylon rivets, the type that can be found here:
https://www.apogeerockets.com/Building_Supplies/Misc_Hardware/Removable_Plastic_Rivets

2-56 nylon screws can be found here:
https://www.mcmaster.com/nylon-screws

NOTE: There is a great deal of information on these forums regarding correct charge sizing and the number of 2-56 screws to use for proper separation of components (find it, read it, understand it, then test it). Ground test everything AS IT WILL FLY (chute packed, shock cord in place, an empty motor casing with proper closures installed, avionics in the AV BAy, etc), and if things separate as they should (just enough to separate them completely but without firing the forward section/nosecone across the yard like a missile), you're ready for flight.

 

[SammyD]

Interestingly, your post's title mentioned "where to split your dual-deploy", but I didn't see that asked in the body of your post..................

FWIW, I try to get the AV Bay as far forward as possible, but still leaving room for the parachute. This accomplishes two things: 1) it pushes CG forward (usually always a good thing), leading to a rocket that's more stable, and 2) it makes more room in the booster section for larger motor casings (more options for motor selection).

Last, but not least, 2.6" LOC paper might not be the best material to use for flights beyond mach, but you'll have to figure that out by searching the forums and talking to folks more experienced with mach+ flights.

 

[Nathan]

The av bay should be bolted or riveted to the payload tube, with the main deployed out the nose. With that configuration:
1) the main is more likely to be deployed in a direction away from the booster section
2) the deployment charge will help blow out the chute, instead of just depending on it being pulled out of the payload tube by the harness.

 

[Zeus-cat]

LOC tubing is pretty solid stuff. I haven't hit Mach with any of mine, but I would say fin issues are a more likely problem at those speeds. Structurally, columns are very, very strong. Fin attachment, fin flutter, fin alignment, motor mount, etc. should be more of a concern than the tubes.

 

[Nick Hutton]

Thanks for replies. Realised I used some incorrect terminology in my original post that may have irked some traditionalists so I’ve tried to fix it a bit.

I’m fixed on the length of the booster as it’s part of the original kit. I guess I should have specified what arrangement to deploy my main.

I’ll go with securing the AV bay to the payload bay and use some shear pins on the nose.

Was clearly planning on ground testing it first. Have already built one dual deploy from SBR, but it came as a kit, so no real choice on setup.