steel fishing line leader as shock cord mount

I've flown an Estes Phoenix that uses a picture wire "lanyard" for the shock cord attachment well over 100 times, primarily with composite motors, and I've noticed no corrosion on the wire whatsoever. The lanyard runs down, parallel to the MMT, through all three centering rings, and wraps around the MMT once at the bottom.

Again, no corrosion on the picture wire, but busted fins? Yep, we've definitely got those. They've been repaired many times.

It's still the Energizer Bunny of my fleet though, with the highest number of flights of all my rockets.

GREAT flier on E18-4W RMS's...

tah

I stopped using the fine steel cable for shock cord after one broke on the first flight. The slightest kink will weaken it so that it will break. And it is damaged by the ejection, especially from bigger motors.

Not to mention they make the best body tube zipper cutters :-(

The heavier steel cable such as what NCR used for their gorilla mounts seems to be big enough to not have these problems. But I'd avoid fishing leader or control line cable for modrocs.

Thanks. That's just what I was looking for, someone else to have the pain-in-the-a, er, ah, "experience", so I don't have to. I'll substitute a more traditional shock cord mount.

Jonathan

----- Jonathan Sivier Secretary, Central Illinois Aerospace jsivier AT uiuc.edu NAR #56437 Tripoli #1906 CIA Web Site:

IMHO using steel fishing line or similar material is great if nice, clean zippers are what you're shooting for. A much better choice for a shock cord mount is braided Kevlar cord. It's cheap, easy to use, heat and flame resistant, and less abrasive. You can get it from Apogee or Pratt Hobbies.

=AF

Geez guys... just keep the wire about an inch below the end of the body tube. No zippers. Handle the rest with Kevlar, with which I've had many zippers anyway. I have a Cosmodrome BB II, and AT Strongarm, and and Estes Phoenix all with the stainless, and/or picture wire, and have never had a zipper.

No corrosion either...

Tod "Did I mention no corrosion?" Hilty

I think whether it's steel or kevlar, as long as it's a small cord, it will be prone to causing a zipper.

Without a wide, flat section of ribbon at the rocket's throat, any high speed deployment, wherein the chute opens while the rocket is moving fast and then jerks it backward, will concentrate lots of force on a small arc of the BT opening, trying mightily to dent or tear the tube.

And this applies whether it's a BT-50 or a glassed 6" tube.

Like Tod, I stop the kevlar short of the tube opening. But I transition thru the opening with some sort of ribbon suitable for the rocket size. I take a short length - ~2" in MRs - of 1/4" or 1/2" wide braided nylon ribbon and sew loops in each end. The kevlar leader from the motor mount is tied thru one loop, then another length of (usually lighter) kevlar is used to connect from the ribbon to the NC.

No elastic is used, but tape is wrapped around loops formed into the kevalr near the nosecone (ie, near where the chute is connected). A hard deployment tears the tape thus dampening the jerk.

Anyway, with the ribbon, I've been very fortunate in reducing dents and zippers from the occasional high speed deployment as occurs with weathercocking, bonus or short delays, and errant 3rd stages :)

Not to pick on Quest, but while their combination of kevlar and round elastic is often touted as being superior to Estes' elastic and trifold mount, my take is that it's still lacking for zipper protection. A short length of ribbon or even flat elastic thru the opening would surely be less prone to zippering.

I guess one (I) can get carried away with anti-zipper efforts, but you only have to zipper a 30yo cherished rocket one time to develop a tendency toward caution :)

Doug

of conformity?

:)

Ted Novak TRA#5512 IEAS#75