Using small eyebolts as launch lugs

[COrocket]

I'm just finishing up my first MPR build, a 2.6" Wildman Patriot with a 29MM motor mount. I built it with 1010 rail buttons in case I wanted to launch it on H and I motors. However I've been thinking it would be fun to also launch on F motors from the mid power pads, which could require the use of a rod. Instead of gluing a pair of launch lugs to the rocket, I saw these nylon Eyebolts on McMaster that might work well. 8-32 threads and 1/4" eye should work perfect with the anchors installed in the rocket. Has anyone ever used eyebolts like this or see a reason why it wouldn't work?

 

[waltr]

If you put on two of them like you do the Buttons then I don't see why they wouldn't work.
Just check that they slide easily over the launch rod.

With threaded inserts in the rocket body easy to install or remove as needed.

 

[David Schwantz]

lI might lean toward steel instead of nylon. But other than that, should work fine. Just make sure they do not twist, otherwise they may jam.

 

[BigMacDaddy]

I do not have any experience with MPR/HPR but one thing I did for LPR was 3D print an adapter that slid onto a rail lug to allow a rod launch. This was for much smaller rail (Makerbeam) so I would likely design something different for your application -- I am thinking something that snaps onto the 1010 rail lug from either direction to basically put a rod lug right next to the existing lugs.


Just a thought so TIFWIW...

 

[heada]

Why not just launch from the rail but using an F motor?

 

[Scott_650]

Why not just launch from the rail but using an F motor?

FWIW, when we have a busy club launch, like last weekend with over 20 flyers and 88 launches, the rails can be full while the 1/4” rod is available - I have buttons/guides and lugs on several MPR rockets.

Considering that scale modelers have used small wire loops for years I can’t see any reason why small eye bolts won’t work - probably a bit easier than adding lugs with less chance of marring the finish. Interesting…

 

[OverTheTop]

Nice idea. They do look a little dragy though. Maybe put them on the belt linisher and skinny them up a little?

 

[COrocket]

FWIW, when we have a busy club launch, like last weekend with over 20 flyers and 88 launches, the rails can be full while the 1/4” rod is available - I have buttons/guides and lugs on several MPR rockets.

Considering that scale modelers have used small wire loops for years I can’t see any reason why small eye bolts won’t work - probably a bit easier than adding lugs with less chance of marring the finish. Interesting…

This was my primary goal with having flexibility depending on what pad is open at the time

 

[waltr]

We have one guy in our club that puts 3/16 and 1/4 lugs and 1010 buttons on his MPR's.

 

[lakeroadster]

I used to work with a guy that built custom fishing rods.

Fishing rod guides would be much lighter weight.

 

[JSW]

I had the same idea!

I have a fairly heavy MPR that I preferred to launch from rails, but in case the club didn't have a rail set up,... I also bought small eyebolts to swap with the rail button.

One of the mount points was in the area where the parachute would be stored. I cut down the eye bolt shank so that it didn't protrude into the rocket body (and potentially snag the parachute).

I haven't had to use this setup yet, so can't say how well it works.

I bought steel eye bolts ("Routing Eyebolt with Nut - Not for Lifting, Zinc-Plated with Bent-Closed Eye, 6-32 Thread, 3/4" Shank" from
McMaster-Carr). I do worry there might be too much friction metal-to-metal. Might need to consider the nylon version.

 

[Woody's Workshop]

Using weighty thingys on one side of the rocket would require a large fin selection mounted in slightly spiral arrangement.
It would make for a dandy sightful flight and record breaking loopy smoke trail.
But what the hay, if it's fun, safe and you can afford it, why not?
Or, you could 3D print (or have printed) something that resembles a metallic eye bolt. Is launching an exterior metallic object legal?
That rule is getting vaguer every year with metal fin cans and interior E-bay mounting hardware and metal tipped nose cones.

 

[JSW]

Using weighty thingys on one side of the rocket would require a large fin selection mounted in slightly spiral arrangement.
It would make for a dandy sightful flight and record breaking loopy smoke trail.
But what the hay, if it's fun, safe and you can afford it, why not?
Or, you could 3D print (or have printed) something that resembles a metallic eye bolt. Is launching an exterior metallic object legal?
That rule is getting vaguer every year with metal fin cans and interior E-bay mounting hardware and metal tipped nose cones.

Good feedback about the additional metal.

Bad feedback about off balance/drag. Makes no practical sense given a small eye bolt would be less drag/weight than the cameras people are attaching to the side of the rocket.

Still. I figured there must be a reason why I’ve never heard of this approach. Hence,… thats why people post to the forum - to brainstorm and get constructive feedback. They don’t expect someone to give this kind of [email protected] pompous reply.

 

[COrocket]

Quick update - I decided to order the eyebolts and give them a try. A few quick modifications were necessary, primarily cutting the eyebolts to length and reaming the holes with a 17/64" drill bit so they slid over a 1/4" rod nicely. Optionally, i also used a die to cut the 8-32 threads a bit closer to the eye so the eye sat closer to the body tube (although it would have worked fine without). Overall I'm pretty happy, they feel really solid and strong enough for anything that I'd feel comfortable launching off a 1/4" rod. Perfect for the 2.6" patriot that can fly on anything from high thrust F motors to I motors, so now I can switch between 1/4" rod and 1010 rail easily.

 

[neil_w]

Nice.

Just curious: what is the advantage of these nylon pieces vs. metal? The loops in those look very thick compared to the metal ones I'm used to seeing, seems like they would be more draggy. Although they're obviously going to be lighter, but I wouldn't thing the weight of a couple of small eyebolts would be noticeable in decent-sized MPR.

 

[COrocket]

Nice.

Just curious: what is the advantage of these nylon pieces vs. metal? The loops in those look very thick compared to the metal ones I'm used to seeing, seems like they would be more draggy. Although they're obviously going to be lighter, but I wouldn't thing the weight of a couple of small eyebolts would be noticeable in decent-sized MPR.

I don't think there'd be an advantage over metal, I just chose them because they seemed a little easier to work with in terms of the mods I had to do. Some of the 8-32 metal eyes I saw had a longer shoulder and would have stood off further than the nylon ones. I'm sure metal ones would work fine trading marginally higher weight for lower drag. Also it seems like most rail buttons are plastic so I was wondering if the nylon ones would be less likely to bind (since they can rotate in the holes). The nylon ones seem to slide pretty easy on a metal rod once I opened them up to 17/64" diameter.

 

[jrap330]

Quick update - I decided to order the eyebolts and give them a try. A few quick modifications were necessary, primarily cutting the eyebolts to length and reaming the holes with a 17/64" drill bit so they slid over a 1/4" rod nicely. Optionally, i also used a die to cut the 8-32 threads a bit closer to the eye so the eye sat closer to the body tube (although it would have worked fine without). Overall I'm pretty happy, they feel really solid and strong enough for anything that I'd feel comfortable launching off a 1/4" rod. Perfect for the 2.6" patriot that can fly on anything from high thrust F motors to I motors, so now I can switch between 1/4" rod and 1010 rail easily.

Did you just glue them in, threaded into something or using a nut to secure them?

 

[COrocket]

Did you just glue them in, threaded into something or using a nut to secure them?

They are threaded into a PEM nut that is secured to a fiberglass airframe, although a T-nut or anything threaded would probably work fine. I screwed them in until they were snug but not tight to prevent the plastic threads from stripping.