Recovery Harness Attachment

[Kenneth ReillyParticipant]

I’m in Longmont as well and don’t mind shating at all.

[John A. WilkeParticipant]

For a rocket like the Nike, you have more options – in the case above, the centering ring centers a 54mm motor in a 4″ tube, so there is nearly 2″ of ring to tie into. I’d probably put an eyebolt or two into that ring and consider tying into that. I didn’t mention that as an option earlier, because Bret has a much larger rocket and a much smaller ring (centering a 4″ tube in a 5″ tube, so 1″ of area to work with vs. nearly 2″ for the Nike). With the Nike, you have enough room to put a washer on the backside, etc.

As far as putting anchors into CTI fwd closures… remove the delay and put a blind nut in there and lay some epoxy in there and call it good. The 54mm delays are epoxied in, so you can’t remove and replace them.

[Tim Thomas]

8) I have a 4in. nike from John. So does Fonz down in Pueblo. We up- graded ours to 75mm and both of us have had bad ass flights with them. I used a L585 Imax that went to 11,965 at Chili Balster. If you leave it stock and build it right, your L2 should be in the bag. And a ton of other flights later. I would seek out MotoJoe for your motor selection. Maybe a large Pro 54 J or a small K. Then you can ‘let-er-eat’ and folks will be asking you for advise. 😛 The 4in. Nike makes it easy to HAVE FUN! I would fly that if I were you! 😀 😀 😀

[Warren B. MusselmanModerator]

I’ll stand by my statement – don’t glue in webbing as your shock cord anchor – regardless of the material. In a 4″ bird with a 54mm motor mount you can easily use a forged eyebolt and washer or a u-bolt for the anchor point and reach in to connect the shock cord with a quick link.

Lots of options for motors as Joe, John and Tim indicate. Just remember to make sure you can reach down in to connect the shock cord. If your arm doesn’t reach, put in a longer motor mount that you CAN reach – besides, it’ll give you far more motor options.

[John A. WilkeParticipant]

I’ll stand by my statement – don’t glue in webbing as your shock cord anchor – regardless of the material. In a 4″ bird with a 54mm motor mount you can easily use a forged eyebolt and washer or a u-bolt for the anchor point and reach in to connect the shock cord with a quick link.

Lots of options for motors as Joe, John and Tim indicate. Just remember to make sure you can reach down in to connect the shock cord. If your arm doesn’t reach, put in a longer motor mount that you CAN reach – besides, it’ll give you far more motor options.

To clarify – I’m not suggesting that you epoxy Kevlar – ever. In fact, I was the first one in this string to suggest it be avoided at all costs. My suggestion for an alternate attachment was to anchor an eyebolt into the upper centering ring (big washer on the back) and tie into that. In a 4″ airframe, you can reach it easily.

I don’t epoxy my knots, my piston strap, nuthin – epoxy + Kevlar or Nylon will fail. It becomes far too brittle and it totally changes the physical properties of the underlying fabric.

[Bruce R. Schaefer]

What Warren and JW are saying is that even Kevlar can be cut. Not easy when you WANT to cut it. But, if you send a rocket up with epoxied Kevlar, you’ve added a knife to it… by the time it gets down with all the stress and spinning, etc., or waaaaaay before, it will be cut and separate. Do not go there, Batman. I have a few 1/4-20 eyebolts you can have/use.

[Bret PackardParticipant]

Again, thanks for all the suggestions guys. Just to redirect back to the originl post, I was looking for methods that work with 1/2″ or less space between motor tube and airframe. Certainly if you have a full inch or more for a welded eyebolt and washer that’s easy. Eyebolt in threaded closure certainly seems to be the best for what I am looking to do, I was just under the impression that when you got to L3 caliber motors having multiple attachment points was preferred.

I’m curious if anyone has actually had a failure on an epoxied webbing anchor. I only ask because I have at least a dozen PML kits that’ I have built over the years that were done that way per the instructions. I never really worry about flying them, but maybe I should. To date, I have never had one fail. On the more recently built rockets, I used tubular kevlar for the piston strap so I didn’t have to worry about frying the nylon one.

[John A. WilkeParticipant]

The epoxy can (and does) also change the physical properties of the Kevlar. I’ll bet if you soaked the flat Kevlar in epoxy and took it out later you could actually break it in two – it becomes very brittle.

Kevlar is – far and away – the most superb material there is for shock cords… but like anything else, it just needs to be handled appropriately. I’d never dream of using anything else for a shock cord – but I’d never saturate it with epoxy.

[pmscientist]

I think you might be surprised what you can fit in a 1/2″ gap between motor and body tubes. A 38mm tube in a 3″ rocket is just over 1/2″. Split the distance for the mounting, and at 1/4″ in from the inside of the body tube you get a chord of 2 7/8″, leaving plenty of room for a good 1/4″ eye bolt/nut. For a 3″ motor in a 4″ rocket, the chord is 3 7/8″. That might even give enough room for a U bolt on either side. I’ve personally done this with a 3″ body and 38mm motor tube.

There are many good options. I have to agree that epoxy and kevlar shouldn’t be one of them. I did it once for a mid-power bird, never again.

[greywolves]

Hi everyone,

How about….. Beef up your most forward centering rings (group of 3 for great surface contact), set two 1/4-40 eye-bolts, one on each side of the motor tube. Dead center, should leave room for the 7/16th nut. Then you can do your shock cord, doesn’t anchor the motor though….hmmmm. Guess I’ll stop there then, 2-cents.

Very tricky to get to later, trick fishin.

[Author]

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