LOC "Park Flyer" Sandhawk Motor Retention

[n3tjm]

I used to think Aeropack retainers were to expensive. That was until I started using them. I "inherited" a couple rockets that had them on them and wow, color me impressed. So next few builds I incorporated them in the build and have plans to upgrade my current flying fleet that can be upgraded. Their adapter system is AMAZING. Simple. Strong. Reliable. Doesn't rely on an epoxy bond that if let's go will send a burning rocket motor loose inside your rocket. That alone to me is worth the cost and js exactly why I went with a Aeropack retainer on my 7.6" Patriot rather than using the included stock 54mm adapter. Furthermore, to save cost, you can buy the components separately. So for example if you already have 3 or 4 caps, you can save money by just buying the bases and share caps between the rockets.

 

[ep29030]

If you want cheap motor retention, go with the old Z clips, or attach a piece of all thread on motor tube during construction. Make it stand about 1/4" taller than the inserted RMS case, then use a washer and nut to secure the case. I've done that for several of my old MPR kits and it works fine.

 

[bad_idea]

Yes, exactly. 6061-T6 I believe. Nearly the same weight as the plastic Estes but vastly stronger. I've had a rocket land aft first on concrete and while the Aeropack was dinged and scuffed up bad, it was still usable. If the same happened with an Estes retainer, it would shatter and become a mess.

Should be pretty easy to grind the Estes retainer off and JB Weld a new one on though (or just replace the cap if that's all that was damaged). You'll likely have a spare or two already anyway since they come two to a pack, are practically free at AC Supply, and are included in nearly every Estes kit I see on a decent sale.

I was a little shocked in doing inventory tonight to discover that I'd overbought on these retainers to the point that I have 11 unused which I'd bought as standalone products, and 9 more that came as part of kits.

I have plans for two of them, but I'm going to have to design a SPEV to kit up for some sort of outreach program simply to use up more of these 18 spare retainers.

I think people mostly cluster because they think it's cool. With modern motor availability, it doesn't really make sense if you're optimizing performance in hobby rocketry.

I got into clusters as a safe way to test composite airstarts. My notion was that a ring of blackpowder motors could be very reliably and safely ignited on the ground, such that whether or not a composite motor in the middle lighted later wasn't of as much consequence to safety, as it would never itself be off-axis.

What I discovered was that clusters in themselves are just absurdly fun for some reason. Later, when I began working on clustering composites, I also came to find clustering to be good practice. As you are the master of ignition (it's your dip formula that I use for my clusters, for which I thank you!), you don't really need that practice of course.

Edit: Had left the word "as" out in front of "much consequence." You still have to make sure you don't light the airstart when you're weathercocked or arcing over. But I see many people launching on a central motor and trying to light a cluster in the air, often with mixed success resulting in off-axis thrust.

 

[Art Upton]

Some should read the 1970s NAR mag "The Power of masking tape" years Later an old guy proved at black rock that masking tape on an O motor works OK