Good for you Conway. I won't use them. I can't see any advantage to the eyenut method, other than a slight weight savings, but you have to admit there is the possibility of them backing out in flight. Even if it is one in a million chance there is still the possibility and using the U-bolt is zero chance. Like you said, to each his own. Maybe it's the payloads I put up that make me more paranoid about trying to get them back unharmed.

Doug

I like the eye nut concept because it puts the load straight into the threaded rod, which is the only thing typically holding the ends of the av bay together. Otherwise, the offset of the u-bolt from the threaded rod(s) means that the bulkhead has to resist the torque from the harness pulling one way and the threaded rod pulling the other. Without that torque, then the bulkhead can be made much lighter because it's only there to seal off the av bay and take in-plane loads to keep the rod centered. You could even do it with something like a fiberglass/balsa sandwich.

Conway mentioned the key to eliminating the unscrewing problem: the locking nut. If you have a 1/4" nut backed up against the eyenut with a wrench, consider how much torque would be required to back those away from each other. Way more torque that would be possible to impart with harness attached to the eyenut even in the worst-case windup of the shock cord.

Now, if someone can just find a #6 (as in, less than 1/4") eyenut for me, for my itty-bitty av-bay, I'll be all set. What I have been doing instead is using a #6 wingnut, then a washer, then another wingnut to serve the eyenut function. The washer closes off the opening without crushing the loop of shock cord that goes in there.

My eye nuts and threaded rod are drilled and pinned to prevent unthreading. One is fixed and uses either a roll pin or cotter pin, the other uses something much like a safety pin. I had some fears about unthreading when I first considered using eye-nuts, but by drilling and pinning them that issue is completely moot.

That said, with the larger birds Doug flies, I would most definitely be using U bolts and dual threaded rods instead of a single rod and eye nuts.

Warren

More questions, diving into this as the noob: Has anyone ever seen a front closure unthread from the casing due to recovery harness attachment? It's pretty straightforward to put a jamnut between the eyebolt and closure, but what about the closure itself?

And then, on the bay, if you have multiple rods with eyenuts, how do you do the multiple attachment with your harness? Or do you just attach to one?

My next build will be zipperless with room for an "all motor" booster section, so I'm still debating the attachment. With the long motor, it's obvious to use the eyebolt in closure. But with the short motors, you're back to a regular zipper-prone configuration. Ideas?

Ken

My eye nuts and threaded rod are drilled and pinned to prevent unthreading. One is fixed and uses either a roll pin or cotter pin, the other uses something much like a safety pin. I had some fears about unthreading when I first considered using eye-nuts, but by drilling and pinning them that issue is completely moot.

That said, with the larger birds Doug flies, I would most definitely be using U bolts and dual threaded rods instead of a single rod and eye nuts.

Warren

For my smaller/lighter projects for the Ebay I use only one stainless steel threaded rod. (depends on the weight and size). I always chose a more then sufficent size and strength rate to hold. In bigger projects like my L3 or other bigger projects I use 2 threaded rods minimum. (could be more depending on the size and weight of the project. I always attach my harness to the threaded rods via locked in place forged eyenuts. The nuts will not back off ever. Not even a chance. By attaching to the rods on each end with the eynuts the stresses of the yanking and pulling from the harness is on the strongest material as well as the directions of pull through the center of what actually holds the ebay together. So you have stronger material, the direction of the pull on that material is through its strongest capabillity as its hard to pull the rod apart by pulling on the length of it.

There is always more then one way to skin a cat... Doesnt make my way more right or wrong just different and what I believe is stronger then a ubolt in a bulk head as the materials are different and you will have to drill and cut the bulk head and that can add weak spots. I have seen a ubolt pull through. Even with washers on them. But it would be about impossible to pull the whole rod or rods through as the force exerted is different.

Conway

More questions, diving into this as the noob: Has anyone ever seen a front closure unthread from the casing due to recovery harness attachment? It's pretty straightforward to put a jamnut between the eyebolt and closure, but what about the closure itself?

And then, on the bay, if you have multiple rods with eyenuts, how do you do the multiple attachment with your harness? Or do you just attach to one?

My next build will be zipperless with room for an "all motor" booster section, so I'm still debating the attachment. With the long motor, it's obvious to use the eyebolt in closure. But with the short motors, you're back to a regular zipper-prone configuration. Ideas?

Ken

Well, I cant say Ive ever seen that happen. I dont fly to many threaded closures much, as most of what I do is all snap ring stuff. But I bet it would be pretty hard to do.. John Wilke has flown many AT cases in that mannor. (Tony A. Has flown his like that many times all the way to 35K in altitude without an issue.) Im also pretty sure that if that was an issue Manufactures wouldnt make them for that purpose... I think I will shoot an email To RouseTech and see what they say... Makes me curious.

With Multiple rods Ive used a Y harness that I made or you can do 2 full length shock cords. I used 2 Y harnesses on my L3 rocket Full Throttle on both the Apogee and Mains. Works very well and plent strong.

As far as Zipperless... What you are describing is not zipperless. having an open end with the motor attached to the harness doesnt make it zipperless design. True zipperless is not even what it says it is. In fact its kind of a poor name as it still can zipper but is alot less of a chance that it will. Most of the time the booster never is the zipper issue. Its the body tubes above that. But in true ziperless deployment what makes the booster zipperless is that you will have a coupler installed in the booster glued in place making the top of the booster double wall and much harder to zipper. as well as the way that the body tubes will now contact the harness it makes the apogee deployment less likley to zipper. Hope that makes some sense... The motor length wont make a difference. The contact point on a zipper is at the top of the tube where the harness exits and again thats double wall via a coupler stick out. You might damage the coupler but it probably would stop at the double wall.

I follow what you're saying, Conway. I'm just trying to decide whether to top the booster with an open coupler and use the eyebolt closure, or to put the bulkhead in the coupler with a U-bolt. BTW, this is a 3" PR Competitor with 54mm mount. I'm making the booster long enough for 29" of motor. I think that should cover all (non-hybrid) cases commercially available.

Thanks,
Ken

the booster long enough for 29" of motor. I think that should cover all (non-hybrid) cases commercially available.

Thanks,
Ken

Maybe...... 😉 I keep hearing of some new stuff.... Can you say MUCH longer motors possibly/probably on the way... 😀

Correction. It will hold more motor than I can afford. 😛

Ken

Adrian,

Regarding the #6 eye nut request- head to the hobby store. I've made a couple small simple ebays using a RC Plane wheel collet for the eye nut.

I usually add a locking nut as well, just to make sure it does not back off during the often winding descent.

Regarding the whole eyebolts "backing off" issue, I'll say that this concerned me greatly earlier on. Then one day I was flying minimum diameter everything and I had no other choices. I tried it, and it worked great.

I've never once had an eyebolt even start to think about coming off. I do use lock washers, blue Loctite, and some serious elbow grease putting them on.

So you know, most of my rockets fly with three of these each flight... one above the motor, and one on each side of the ebay. So I have a chance for three to unwind on every flight. So far, so good. If I had a bit more room and all, I would probably do things more conventionally. In many cases, I have little or no choice.

True JW that many times it is unavoidable especially with minimum diameter rockets. You have to use they eyebolts and it sounds like you are taking appropriate precautions. But I have seen them un-thread and since I have the room in my rockets, I prefer the U-bolts. As far as a U-bolt pulling through a bulkplate is a failure of the bulkplate and not the U-bolt. Of course for my last couple of projects my bulkplate the U-bolt runs though is 1/4 inch thick aluminum...

Doug

Given that I now have the tools to do the same, machined aluminum bulkheads and rings seem like the only way to go.

Doug, saw the parts for the bird you and Art are working on - impressive.

Warren

Lets just hope it gets done in time for MHM.

Doug

I've got the very same problem. Looks like construction should be done in another 3 weeks - another week for testing - then 2-3 weeks for paint and finish... of course that's optional. I'll fly the thing naked if it comes down to that.

Warren