Ken,

Since you are still doing construction, I recommend running small tubes from the forward compartment to the aft of the motors. There are several different ways to airstart motors but if you have a tube to pass ignitors through, it increases your options later on. I use a small diameter carbon or fiberglass tube from CST but even a straw will do.

I recommend the PET2 from Missile Works. It allows use of a pull wire to trigger the timer. I have used a single channel to ignite 4 matches so three per channel should be no problem. You may also wish to mount a momentary switch on the bottom centering ring (if there is room) to trigger the timer and run the wires to the electronics bay.

Doug

If the timer is in the front ebay, how do you get the connection between the main airframe (with wire conduits) and the bay?

-Ken

There's a couple ways: one i have done 2/2 tmes, the other I have heard mentioned.

First the way I know it will work:

Use copper foil--can be adhesively backed or not. Locally i have seen it at McGuckens, but McMaster-Carr stocks it. There are many ways to skin a cat, but basically what you want is a 3/8 inch or larger copper diametricaly opposed strips on the outside of the coupler and the inside of the airframe in which it inserts. Realy 30 degerees apart would be plenty, but why risk a leaning couple.

You gotta figure out where the wires get soldered to the copper foil, needs to be a robust joint, and contiinuity checks will let you know whether it is a go. Seems to me this is a good method of jumping coupled pieces. But in that pre launch faze, make sure that whatever needs to be sent downstream does so before the coupler is separated.

JS

Since you're dealing with a 38 main and 29 outboards, do you really need to do DD? if not we built the timer (PET of course) into the coupler area of the VV2 (civil air patrol project) which ran a central L on initial boost, lit 3 more motors and when they were done lit three more.

So in short, I'd plumb a line into the lower section for a timer as it's all gonna happen before it separates anyways. Well at least you hope so.

Just my two cents.

Dave2

My original plan was to put the timer (PET2 or Perfectflite Minitimer3) in a small bay above the outboards, but below the fwd centering ring. I've got a space between the 38mm motor tube and 4" airframe about 7" long. This would make short routing of ematches through conduits directly to the terminal block of the timer(s). The recovery altimeter would stay by itself in the upper ebay.

I don't need DD, but would like to have a vehicle to practice it in before getting too high. For the drogue charge, do you just run long leads on it and drop it below the laundry? I've seen some with the charge just mounted to the aft end of the ebay coupler, but that seems bass ackwards. I don't want to mod the kit to zipperless, as the sustainer motor tube is about 12-14" long.

It seems that if I want to run either motor deploy or altimeter deploy, the charge would be blowing opposite directions. Anyone got a brief tutorial on this? I was expecting a copy of Modern High Power Rocketry 2 for Christmas, but my wife forgot that I asked for it. 🙄

Thanks,
Ken

Ken,
There is a discusiion on info central I remember reading when I had the same thoughts, and the perfect flight manuals, eg the MAWD, have a brief tutorial that can be downloaded from the site. Generally, I don't think it matters much which way you push, provided it's a vigorous push. So while it may make more sense intuitively to use long leads and push from below, unless you have a situation where the recovery device could be wedged into something, the pressure from the BP will drive the part at a decent enough velocity to pull out the laundry. But I must admit, I still am a bit of a chicken so I build zipperless, but in a manner that allows a long motor to protrude into the drogue compartment--either I use the motor itself for retention, or squeeze in U bolts between the AF and mmt, and hang onto these.With big motors its both. Not sure I answered your question, but yes for me I have opposing charges mounted to the e-bay which is screwed to both recovery comartments and separate at the can and NC.
JS

As John said, you really don't need to push it from the bottom. All of my DD rockets push from the E-bay, and work fine. My deuce pushes the drogue from the e-bay, and separates at the same point, relying on the momentum to pull it apart. Works great. I wouldn't mess with the long leads - seems like it adds unnecessary wiring. Just make sure to ground test, and all will work out just fine.

I'm going to get some small fiberglass tubing at the local kite store. Can someone who's done airstarts let me know what size (ID) I need to fit a pair of ematch wire pairs through (4 conductors per conduit)? I'm running 3 separate small conduits so they aren't flapping in the breeze below the sustainer. Remember this is for 6 24mm airstarts. Recommendations on ematches? How about availability? They need to be small for fitting 24mm reloads or Estes D/E motors.

Thanks,
Ken

Hurry, so I can start epoxying this puppy!

It sort of depends on how long the runs are but I have used about 1/4" ID tube for 30" long runs for a single e-match wires with no problems. I would think for short runs (I guessing you have no longer than 10") that 1/4" would be fine for two pair. You may be able to go even smaller but go as large as you can to make it easier to feed them through. I have been using Quickburst lately until they stopped selling, so I can't recommend e-matches.

Doug