Estes Prowler mod for an EggTimer Apogee

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SecondRow

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One of my goals this year is to learn to fly a rocket with traditional dual deployment. I don’t have any experience with electronic deployment. I’ve been looking at a couple different 4” kits to fly, but I haven’t decided on what I want just yet.

In the meantime, I bought two EggTimer Apogees and built them over the holidays. The Apogee is a single deploy flight controller that EggTimer introduced last fall. Like all EggTimer products, you put the board together yourself, but it’s nearly all through-hole soldering. Very easy to build, and only $15. With it, you get a small altimeter that will pop your nose at apogee. Pair it with a Jolly Logic chute release (which I’m comfortable using), and you get deployment of the parachute bundle at apogee, followed by the chute opening at the height you select for the JLCR. For about $12 more, EggTimer sells the EasyMount, a mount for the Apogee made by LabRat rocketry. I picked up one of those, too.

I thought I’d try to use my Apogee in something small. So I’m in the middle of modifying my Estes Prowler. Since the Prowler doesn’t have a payload bay, I decided to mount it in the nose. This thread documents the mod I made to the Prowler to fit the Apogee, shown here mounted to the EasyMount.
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SecondRow

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First up was deciding whether to attach the mount to the nose cone or make a bulkhead to insert into the nose. The EasyMount needs 1”. The nose cone base did not provide enough flat space to mount the altimeter, because of the shock cord anchor. So, I decided to cut off the base and ordered a coupler and bulkhead from Erockets. Cutting the base off left me with 5/8” for the shoulder. The original shoulder was 2”.
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SecondRow

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Choosing the right coupler was trickier than I thought it would be, because at 2” the Prowler is not a standard rocketry tube size. I picked two couplers that that were close to 2” and used the one that fit best in the nose. It ended up being the longer 4” coupler.
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Heres a dry fit of the coupler and bulkhead.
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SecondRow

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Drilling out a 1” hole for the mount and dry fit. I did not center the hole, because I didn’t think I’d have space for the shock cord mount.
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SecondRow

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I then epoxied the mounting ring to the bulkhead, using the mount to make sure everything was lined up.
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SecondRow

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Epoxied the shock cord mount and glued the bulkhead into the coupler. I also punched a hole in the coupler (you can’t see it in the pic) for access to the screw switch. Next up is to epoxy the coupler into the nose cone and punch a hole in the body tube for access to the screw. I’ll probably do that tonight. I also just realized I’ll need some type of protection for the shock cord since it will be so close to the ejection charge, and I won’t be able to put dog barf at the top of the rocket.
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SecondRow

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The coupler is epoxied into the nose cone. I put the coupler in deep enough so the total shoulder length is 2”, the length of the original shoulder. Because the coupler fits inside the shoulder, it’s not wide enough to really help keep the nose cone in the body tube. I’ll need to wrap a lot of tape around it.

Here are a couple last pictures of the coupler in the nose and the Apogee inserted. The Apogee is held to the mounting ring by the two mounting screws and can be easily removed for battery charging, repair or whatever.

Now I just need to order some ematches, test the Apogee and I’ll be ready to try electronic deployment.
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SecondRow

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Ematches arrived today, and the Apogee works as advertised. As soon as the vacuum was shut off, the ematch lit. I can’t wait to try it at the next launch.

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Update: I flew the Prowler last weekend. After hearing from a fellow club member about how his Apogee did not fire (he hadn't yet figured out why), I decided to first use motor recovery with an e-match along for the ride to see if the e-match would fire. I insulated the e-match from the motor ejection charge as best I could. The first flight was on an AT E-16. Upon recovery, I saw the e-match had fired and the altimeter was chirping the altitude - 829 ft.

Satisfied the Apogee worked as advertised, the second flight was on an F22 without backup ejection. Ejection occurred just after apogee for a successful recovery. Altitude was 1222 ft. I would have expected a little higher given the first flight's altitude, but I haven't looked into it yet.
 

tOD

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Your thread is a big help to me. I just finished and tested my first Apogee. I plan to mount it to a plywood bulkhead in the nosecone of a LOC MicroMag. Since the stock nosecone doesn't have a flat base I ordered a bulkhead and will saw the base off and glue on the new bulkhead. I'll post a few pictures after I receive the bulkhead and get started on the mounting. I also ordered a new Chute Release (mmmy third). I'm terrible at holding on to those things. The MicroMag seems like it's custom made for this setup.
 
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