G tolerance // 3” LOC Iris

Question for the more experienced crowd after a little Background...

Nearing the tail end of my L1 rocket build and it’s getting time to start considering motor choices. I purposefully build this rocket to one day be able to withstand 38mm Js when I feel I’m ready for level 2 in a year or two. With that being said, she was ended up being a little Heavier then I wanted it to be ( fully loaded with redundant avionics bay and nose cone gps sled ) roughly 75 oz before paint and I suspect it will land around 80oz. I was hoping to be able to use an H for the cert and then move up to I motors after that, and hit somewhere around 1700-2k ft. The only suitable H motor apparent to me to fulfill those criteria right now is a H550. It has plenty of go for a H, and sims tell me it’s going to gen about 24g’s on liftoff.

My question is will a overbuilt LOC bird take 24g’s without issues?

If so, does anyone know the “line” of speed and G’s that they will Tolerate before having issues?

Thanks in advance

Josh

I seen a 3" LOC rocket fly on a J825r. Built with wood glue and it was fine. I think yours will be fine.

bone stock vulconate on a J600, built with wood glue (2.6 inches)
bone stock mega magg on J1799, built with wood glue (7.5 inches)

don't need to overbuild anything....

Josh, I am sure your rocket will fly fine. LOC's are great kits. But on a cert flight you might consider keeping it as simple as possible, no electronics, use motor eject and keeping it in sight the whole flight. A small H might be just perfect then. Don't get me wrong what you have done is a good thing. But I feel the less to go wrong on a cert flight, the better. Good luck, let us know how it went.

Thanks all, I guess I will do as Richard Rawlings and let her rip taterchip

I've flown a pure stock Estes PS II Partizon kit built only with wood glue (well, JB Weld on the motor retainer). It took 21g actual max acceleration without so much as a whimper. That PS II kit is 56" long and way skimpier than the LOC kit you're building so I wouldn't think twice about 24g if I were you.

~Dave~

Thanks for the confidence. I’m getting back into this trying to grasp the boundaries and strength of material and probably overthinking things

Take the peak thrust of the motor, put the tube on a scale and press till you hit the number.
In flight, you'll experience less force than that since the rocket is being accelerated instead of pushed against a scale/wall/ground.

But even then it's not the tube's compression that's the issue, it's bending. To prevent bending, make sure your coupler joints are strong (a little over a diameter of length on the freesliding side), and make sure the fins are on straight (and are sufficiently sized to stabilize the rocket), so they don't cause big lateral loads along the body.

Mine was 70oz. without motor. I used it for both L1 and L2, but without redundant electronics and no GPS. I used single altimeter with motor-eject as backup. For L1, you shouldn't have a problem keeping it in sight.
See my signature.

Makes perfect sense and a frame of ref. I def have good coupler set up so I think I’m way good thx all again

Nice looking bird rich. Iris has a special place in my heart as it was my first L1 in 1999. Obviously a lot has changed since then lol. Keeping it in sight for sure for L1 but someday I want to stick a 1080 case J in there and let it go out of sight. Future plans .

Jay Dub 4009 said:

Nice looking bird rich. Iris has a special place in my heart as it was my first L1 in 1999. Obviously a lot has changed since then lol. Keeping it in sight for sure for L1 but someday I want to stick a 1080 case J in there and let it go out of sight. Future plans .

Click to expand...

Thanks. I was concerned (unwarranted) with strength/weight too, and did a few things a little differently.
1. I Epoxied the payload tube to the coupler. A little more work assembling, but bending at that joint is now a non-issue.
2. I used a u-bolts instead of eye bolts all around. Compensated with aluminum all-thread in the coupler, for weight saving.
3. I brushed some thin epoxy on the inside end of the airframe tube and coupler, as per LOC web page. This should help with bending too.
4. I used a dino chutes shock cord bumper (to help against zippers).


Not saying that anything I did was necessary or correct, but it worked for me.

I also did ubolts on the motor mount and avionics bay. Nose cone got a welded eyebolt. The standard LOC avionics bay is very strong and honestly it weighs a lot (16oz without electronics) ...that’s what I attribute most of the weight gain to. Oh well, at least it’s strong I suppose. Lastly for zipper protection I installed a y harness on the motor mount ubolts.