Risking a Hi-Flyer build, for my Nartrek Bronze bird

I know, I should have just gone with a Wizard or Yankee, but something about the fins on them just set me off.... so I picked up a hi-flier instead.
My target is a successful pair of NARTREK Bronze duration flights on streamer and parachute.

I'm well aware of the reputation of the Hi-Flier for, well, creative flight profiles. The kit I picked up has the nose weight clay of course. But I am considering some different ways of handling this flight to make it stable.

One is swapping over to friction fit on the motor, which should eliminate some bottom end weight and drag inducing components. Another is swapping nose cones as I'm led to believe that this nose cone is part of the stability issue, and rocksim confirms this with a big stability change in the margin just going to an eliptical nose. But since I don't HAVE more nose cones for 18mm body tubes, I'll probably end up printing one instead. Otherwise this is going to be a quickie build for the most part without extensive filling of seams and things like that.

Also I did make a promise to my daughter. She wanted me to paint my QCC Explorer in pink and purple, but I was able to compromise and she agreed that my NEXT rocket could be in her colors. Well, this is that rocket.

A bit of a math-y post before the meat and potatoes. I only have the trial version of rocksim right now, so can't plot the descent stage.

Since the target on this is for my Nartrek Bronze flights, the limit is of course a B motor. Problem #1 on this rocket is stability, I don't think altitude is going to be any issue at all. As stock, without the nose weight, Rocksim gives a margin of .77 for marginal stability. Best altitude for a B is off a B6-6 at 1003.87 ft at almost a perfect apogee deployment. Adding the nose weight clay helps stability quite a lot with a margin of 2.28, only reduces the altitude by about 5-10ft. B4-4's deploy on ascent in every simulation I've run, sometimes at a fairly good velocity of 50-75ft/sec depending on configuration.

So, here's the different plan. Removing the motor hook and ring, and switching to a 2x20 ripstop streamer, gives me 1034ft and a margin of 1.14 with no nose weight, due to the CG shift.
Swap to an eliptical nose cone? Oddly enough doesn't make much difference at this point. A hair better margin but no real change in altitude. So it looks like I'll keep the stock cone.
Looks like I have a plan. No motor hook or nose weight, bigger streamer, and off she goes. I can probably get slower descents with a crepe or mylar streamer, but I have ripstop fabric and may want to try some different motor sizes, so I want a bit more durability on higher speed deployment.

Now, what about the parachute duration? I have a TLP thin-mill 9" chute sitting here. Swap the streamer for a chute and still hits 1000ft, again looking like a B6-6 is the top performer with a near perfect apogee deployment. Sure, a bigger chute will probably get me a better duration, but I won't know until I fly it..... though right now I think it's going to be real close on time unless I get lucky with wind. It all depends on what side of 20ft/sec this specs out at.

Time to get building!

-Hans

As I said, I'm not putting a huge effort into a rocket that may get lost 15 seconds after the first time I hit the button.... doesn't mean I can't have some fun though!

Recovery gear is pretty standard fare, other than swapping in the chute for the streamer (I don't have the 2x20 streamer yet). So here's the 9" thin mill chute from Top Flight Recovery. I don't think I'd be able to get any larger in the body tube without swapping to a lighter weight material. Then we're back at the stability issues if the CG starts shifting aft again.



Since fin alignment is critical on this one, I'll go with a fun gizmo I saw on thingiverse if you have a 3D printer. A customizable fin alignment jig. I probably should have gone the full height on the fins, but that would have taken another two hours or more on the printer and I was impatient. Worked fine at this height though as long as I used a bit of CA to hold the front tips of the fins from shifting laterally.

Ok, so the basic rocket is done for the most part. Only some quickie fillets, and filled in the gaps in the fins with CWF. But I did decide to try something new for this bird, and I set up a pop lug instead of gluing the launch lug into the body tube. Surprisingly simple once I found some sketches on what they consist of. According to rocksim this is good for another 50ft or so.

Now just to wait for the glue to dry and give it a basecoat. With all the light colors, this would get lost too easy, so I do need SOME paint before flight.

Love this little rocket. There can definitely be some interesting moments flying this one. I will be following and watching the results with great interest.

This is the first time I have heard of a pop lug. I think that I like this idea for small rockets. Can you point me in the right direction?

Originally discovered them when I was looking into a Fliskit Cougar 660, and later found some threads on other rocket forums. The basic idea is that you wrap some tape around the top of your launch rod, and the lug will then stay on the rod while the rocket enjoys its flight with a nice drag reduction. Apparently it used to be the hot rigging in competition a few years back. Here's some plans I found that describes how to make and use them
https://www.oldrocketplans.com/pubs/CMR/pop_lug.pdf

Waiting for the first coat of pink to dry before I mask it off and move to purple. I was going to wait to paint until after the first flight, but the white body tube and nose cone would have made spotting too difficult.

I was toying around with OpenRocket a bit ago, and if I'm reading things correct I should be seeing a 75 second flight with the parachute, even with the B6-4's I currently have (made a best guess in the shop before running rocksim. Won't make that mistake again, got the wrong motors).

-Hans

Thanks Hans! This is a great idea for small rockets and could also be useful as I am starting to move a bit toward MPR builds. Using the pop off lug would be awesome for launching small rockets off of bigger rods.

First flight..... nice and stable, almost lost visual on it due to the altitude. Then it came down without the chute and lawn darted.

I didn't have enough tape on the motor for the friction fit, so it blew it out the back when the charge went off. Didn't deploy the chute fully. Nose cone was popped out, but the chute was only partly out of the top of the body. The good news is that it was light enough and had enough drag that it came back un-damaged.

Probably for the better, wind was higher than I expected and the rocket carried enough as it was. I likely would have lost the rocket otherwise.

-Hans

Do you have enough of the nozzle exposed to put a wrap on the outside? That may be all that you need to keep the motor from spitting.

Not very much exposed, only about 1/4" or so. Still, should be enough to get something around it. Either that, or when the back of my head says 'I'm not sure this is tight enough'.... I should listen to it.

-Hans

2nd flight appears to have been the final. Saw it on ascent for a while, but lost visual before apogee and never saw it again. Too small, too fast, and on a bright overcast day the Estes motors don't smoke enough (or in the right color). Some tracking powder may have helped but who knows. This rocket is a real screamer for sure even on a B motor, I can only imagine it on a C.

I know the chute wasn't packed in too tight, and the motor was a very tight fit, but I suspect it kicked the motor again instead of the chute. IF I build another one, I'm going to keep the hook on it. I'm also going to keep doing pop lugs for light rockets, they are so easy to set up and use.

Paintjob was cute though, my daughter loved the way it looked. She was upset when we couldn't find it.... perfect timing for the Estes labor day sale to start.

That's a sharp paint job!

I'm taking advantage of the sale to replace my Flutter Bye-Bye. Launched it on a B motor a couple of weeks ago.