Ye Olde Rocket Forum - View Single Post - BT-55 based Black Brant III

You might try my technique for constructing a very inconspicuous engine hook. Here is the text of my blog post on the subject. The method works very well and is a good way to eliminate the big commercial engine hook while providing reliable engine casing retention.To see the accompanying pix, visit the post at my blog site listed below.

Internal Engine Hook For The Hornet

Last week I posted the woeful story about the messed-up engine tube in the ol' Hornet.
Here's the re-build I came up with: a new engine tube featuring an internal engine retaining hook.
I ran across this neat little technique back sometime in the mid 1970s. I believe it was published as a contest building tip in an issue of 'Model Rocketeer' or 'American Space Modeling'.
Sadly, I no longer have my old issues of those publications, but if there are any of you out there who might be able to cite the reference, I invite you to post a reply. For this build, I will be relying solely on memory of something I did 35+ years ago....
I recall using this engine retention method in all of my minimum-diameter contest birds and glider pods back in the day, and never once suffered a DQ due to engine ejection. Very reliable system that beats friction-taping hands down.
The heart of this system consists of a length of .020 music wire that is formed and mounted inside the engine tube. This size wire is thin enough that it will fit inside the tube alongside the engine casing.

To mount the wire, a slot is cut on the outside of the engine block (here a section of 13mm engine casing). This provides clearance for the wire between the block and the inner body tube wall.
The fore end of the wire is bent to form over the top of the engine block.
The whole assembly is then glued into place inside the engine tube.

Once the glue is dry, an engine casing can be inserted to mark for the bend at the aft end of the wire.
Because the wire is designed to hook over the engine at its strongest point right next to the bend, there are no real worries about using such a thin diameter wire. Music wire is tough stuff.
The excess wire is then cut off, and, voila.... a nice little engine hook!
When prepping a model for flight with this system, a small pair of needle nose pliers or tweezers are required to grab the end of the hook and secure it over the end of the engine casing.

The only aspect of this system I haven't tested is its endurance. The contest models I used it in back in the day were never flown more that half a dozen times.
Since I still have 65 flights left to go on the Hornet to reach that magic 100 mark, this bird will be a good test platform for the technique.
If the system proves reliable over time, I may start incorporating it into more of my future clone and custom designed birds. Music wire is way less expensive than manufactured engine hooks.
Stay tuned....