Good starting point for building a first av-bay?

[ActingLikeAKid]

Some rocket-related googling last night brought me - once again - to ogling the MAC performance Rayzor. I started thinking - maybe this is next winter's project, particularly if Black Friday is as tempting as usual. That said, this would be my first foray into dual deploy.

I have a general idea of what's necessary for an av-bay and what all the parts do, but is there a good hand-holding reference for a first-timer? I know Modern High Powered Rocketry comes highly recommended for a lot of topics; does it get into electronics much? If I do a DD build over the winter, I probably should get that anyway....

thanks!

 

[Bat-mite]

There really isn't much to it. A MAC kit comes with a bay, sled, and rod mounts. It comes with all the hardware.

Put a charge well at each end. Put an altimeter and battery on the sled. Altimeter needs to be on standoffs to allow air to pass under and over it. Wire it up according to instructions. Make sure any holes you drill in the lids for wires are sealed. You'll need some sort of switch. Lots of threads on that. Drill static ports in the switch band. You're done.

 

[ActingLikeAKid]

OK, that actually sounds ... pretty reasonable. Now to start stuffing dollars away in the Rocket Fund jar...

 

[mpitfield]

Bat-mite is correct, it is relatively routine in most cases but it can get tricky and require some imagination when you deal with restricted spaces.

I will share with you the mistake I made on my first AV bay. I decided to take the 3" Pinnacle nosecone on my PML Bull Puppy and use John Coker's nosecone AV bay method, by adding a sled attached to the removable bulkhead. All of that was relatively simple, as was laying out the components and wiring it up, space was not an issue. I followed up the AV bay build with a bunch of bench tests, then deployment charges tests, and all was well.

However on my first flight the main failed. Luckily the deployment method was a burrito wrap with a cable cutter and I also experimented with a small pilot attached to the top loop of the main in the burrito, so enough laundry was deployed to slow it down for a relatively soft landing. No damage, but now to figure out what went wrong.

To shortcut the story, all of my bench and ground tests were done with e-matches that were trimmed. However when I set up the burrito wrap/cable cutter, I added some loops in the e-match lead for slack. This added just enough length to increase the resistance preventing the battery from delivering enough amps to the e-match. To resolve this I removed my 24 or 26 gauge (can't recall) wiring in the AV bay, and replaced it with the largest gauge wire that would easily fit into the terminals, 20 gauge. I also swapped batteries from a 9V Alkaline to a Li-Po.

Some of the lessons learned. When ground testing simulate all of the in-flight set-up as close as you can. Confirm your testing equipment is up to the task; my ohm meter was a very basic cheap tester that was not sensitive enough to accurately see the problem, so I invested in much more sensitive bench meter.

Good luck and you picked a great manufacturer to work on this project; Mike @ Mac has most of everything you need and that Rayzor is a great flyer!

 

[Exactimator]

Apogee has some pretty good resources to get you going:

Basic overview: https://www.apogeerockets.com/Intro-to-Dual-Deployment

Video series on dual deployment: https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_26

This series of videos on the Torrent has two segments on building an AV Bay https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_61

There's also a series on the Apogee Level 2 that has a few videos on the Av bay. Here's one of them: https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_111

 

[djs]

If building the sled intimidates you, you might want to look into the sleds that Landru makes- it does simplify some of the attachment points for the altimeters:

general sled:
https://additive-aerospace.myshopify.com/collections/altimeter-sleds

missileworks specialized ones:

https://www.missileworks.com/store/#!/3D-Printed-Modular-Sled-Systems/c/8599330/offset=0&sort=normal

Not sure where you're located, but I'm sure there are people nearby at your local club(s) that would be willing to go over a design with you and offer help.

 

[ActingLikeAKid]

Apogee has some pretty good resources to get you going:

Basic overview: https://www.apogeerockets.com/Intro-to-Dual-Deployment

Video series on dual deployment: https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_26

This series of videos on the Torrent has two segments on building an AV Bay https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_61

There's also a series on the Apogee Level 2 that has a few videos on the Av bay. Here's one of them: https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_111

Thanks!!

 

[boatgeek]

I think my biggest mistake was getting seduced by having the switches on the outside of the airframe as opposed to hard mounted on the sled and accessed through the vent holes. If they are on the sled, you have a solid object that is easy to take in and out of your rocket, inspect, keep wires tied down, etc. If they are on the airframe, there is typically more wiring floating around to give you enough space to slide the sled in and also there is a connection that has to be made halfway through assembly.

 

[Banzai88]

I think my biggest mistake was getting seduced by having the switches on the outside of the airframe as opposed to hard mounted on the sled and accessed through the vent holes. If they are on the sled, you have a solid object that is easy to take in and out of your rocket, inspect, keep wires tied down, etc. If they are on the airframe, there is typically more wiring floating around to give you enough space to slide the sled in and also there is a connection that has to be made halfway through assembly.

Completely agree. I initially put my schurter switches on the outside, but the smaller the rocket, the more difficult this is. I've almost totally switched over to MW screw switches with the screw replaced with one that requires an allen wrench. I use their black little tool funnels, too. 100% much happier with the wiring.

 

[Handeman]

Completely agree. I initially put my schurter switches on the outside, but the smaller the rocket, the more difficult this is. I've almost totally switched over to MW screw switches with the screw replaced with one that requires an allen wrench. I use their black little tool funnels, too. 100% much happier with the wiring.

I kind of went the same route. My L1 av-bay had the micro-switch on the sled and a pin that had to "Remove Before Flight". I moved to screw switches that were mounted inside the switch band and had to be connected and disconnected every time the altimeter was removed from the bay. For my L3 and everything since then, I've gone back to the micro-switch on the sled and pull pin with the "Remove Before Flight" ribbons. The one addition I've included was a screw switch as a master on/off switch that is accessible through the coupler part of the av-bay that is covered by the booster. That way I can turn off the altimeters without having the pins and ribbons in place. When I get ready for final assembly, I put the pins and ribbons in place, turn on the master screw switches and do the final assembly of the rocket. The altimeters stay off until I pull the pins on the pad.

 

[blackjack2564]

That said, this would be my first foray into dual deploy.

I have a general idea of what's necessary for an av-bay and what all the parts do, but is there a good hand-holding reference for a first-timer?
thanks!

Yes right here: https://www.rocketryforum.com/showt...x-quot-build-starts-now!!&p=448129#post448129

AT top of HIGH POWER sticky called...how to build a DarkStar. There are several pages related to just av-bay design and mounting. All of it holds true for paper rockets also and can be scaled up & down..... 3in diameter is a nice entry point. Easy to work in & not to big.