Arreaux with Aero Pack

Howdy, I'm building my first mid-powered rocket and I decided to build an Arreaux. I have the kit, a 29L Aero Pack retainer, and a RMS 29/40-120 motor housing. I've been reading through the instructions and the forum before I get started and I have what I think is a fairly simple question, but I wanted to make sure. I understand I will need to leave out the metal retainer clip, but do I also leave out the thrust ring? I assume the Aero Pack acts to transfer the thrust from the motor into the motor tube by means of the aluminum flange that the motor rests on? Is that correct? Also, what is the prevailing wisdom on the baffle and steel wool? I thought I might get a nomex chute protector and leave out the steel wool. If I go that route do I still put in the plastic baffle and if not, whats the best way to attach the shock cord to the motor tube. Thanks in advance for any suggestions you all may have.

If you plan on using only the 29/40-120 motor, then the stock engine hook and engine block are fine. The Aeropack is overkill. For longer motors, remove the engine hook, remove the engine block, and use the Aeropack if you please. In all cases, the rear closure on RMS motors acts as the thrust ring against the motor tube.

I like the baffle and steel wool - works great and easy packing of the recovery gear. Again, a longer motor may interfere or be too close to the baffle, so you will need to remove it and go the nomex route. At this point, you will need an alternative shock cord mount (not the nylon) attached to the centering ring/motor tube in some fashion.

...do I still put in the plastic baffle and if not, whats the best way to attach the shock cord to the motor tube. Thanks in advance for any suggestions you all may have.[/QUOTE]
Hey KDA!- Weldome to TRF! You have some valid questions and excellent observations. I have extensive experience (some say too much!) with Aerotech products (it helps to know the guy who designed the Initiator) and over the years have done several mods and changes to most all the kits. Long story short-I killed my Mirage (with 97 flites) using a 360 case with too much dog barf-but learned a few lessons along the way. First-ditch the thrust ring and metal clip. I have a build thread coming where the clip comes in handy ( on a Wild Child!) and yes- ditch the Chore Boy/metal mesh/steel wool/whatever. It may serve to catch the plastic ejection plug or clog up and eentually core sample your bird. You are accurate in going with the nomex and you CAN use the plastic screw eye mounting with no ill effects. I also prefer to use ACME rail guides or buttons, but that is your choice if you can fly off rails. Ditch the old lady underware elastic-it's only purpose is to have you buy another kit when it fails and it will. Kevlar works well and you can live with the 750# stuff just fine. One of the hardest things when you transistion to MPR is losing some habits you got with the smaller birds. Mass is less a factor because now you can really tailor your motor to the flight envelope you wish to see, as the selection is much greater than just a "A-B-C" motor. ThrustCurve.org has files on most common (certified) motors and you can use your finished bird as a starting point to see what results you can get from AP vs the BP motors you have ben used to. Enjoy your new rocket and post pics-the crowd loves 'em! Again, welcome and ask any questions (PM if you need to) and jump in the deep end of the insanity pool. Peace, Love and Rockets-dave

Thanks to both of you for taking the time to respond. As for overkill, yeah the Aero Pack is probably excessive, but I saw one at the local launch and decided it's pretty cool, so I ordered one. I also ordered several ft of kevlar cord and I was planning on using that. It looks like filling the spirals will be easier before assembly so I guess I'll get started on that first. The other thing most folks seem to recommend is to leave out the rear fin-lock and apply internal fillets. Are these typically placed between the fins and the motor tube, on the inside of the main tube and the fin (kind of opposite of the external fillets), or in both places?

I did a similar modification on my Arreaux. you can see the thread here: https://www.rocketryforum.com/showt...previously-A-few-Aerotech-Arreaux-questions-)

I have made hundreds of flights with AeroTech kits.

My Arreaux kit has 50+ flights on it. I am a fan of the stainless steel cooling mesh and have fitted it into seval scratch-built models and other manufacturer's kits.

Kevlar is not needed.

When AeroTech kits are built and flown as designed they will perform reliably.

Have fun building/flying your Arreaux kit.