LOC 4" Iris build for L2 Certification Attempt

[jqavins]

This thread will pick up where this one left off, since I got the advice on kit choice I asked for (and then some) and the kit arrived two days ago.

Day 1

I downloaded the RockSim file from LOC, and found that it was missing two parts, the middle centering ring and coupler bulkhead. The file, that is, is missing them, not the kit. So I corrected the file, also renaming the parts to be descriptive of their positions and ordered them in the parts tree likewise. I've attached it below, and also sent it to LOC.

Then I added the things I intend to add that are not in the kit, a screw-on retainer and a small payload capsule, and an extra 2.5% on the total mass to account for glue, paint, small hardware, etc. That, too, is attached below.

I then ran a bunch of sims with both 54 mm and 38 mm motors, and learned that there a bunch of CTI 38 mm 6 grain loads, for which I have the case, that fit me needs and desires better than any of the 54 mm motors I checked. So, I'll be using a 54 to 38 mm adapter. I have an Aero Pack adapter, which I initially thought meant I would want to buy an Aero Pack retainer and not use the LOC retainer I've already bought along with the kit. But, I gave the Aero Pack adapter in the LOC retainer, and it seems like that's going to work just fine. So there's a stroke of luck.

I ordered a J381 from Chris Rocket Supplies for pickup on site at LDRS. Yes, I plan to launch this puppy just three weeks from now at LDRS.

I also have some stuff I want to get done for NYPOWER, which is next week, so that's all for now in the Iris.

 

[Upsrocketman]

Double check the fin dimensions on that file. I went through and found that the rocksim file I had was very far off for the fins.

 

[NTP2]

Yes, I plan to launch this puppy just three weeks from now at LDRS.

 

[jqavins]

Double check the fin dimensions on that file. I went through and found that the rocksim file I had was very far off for the fins.

One, thanks, I'll check.
Two, HOLY CRAP!


It looks like I'll be OK. The static margin with motor installed is 2.04. I like percent of rocket length better than caliber, and I think 10% is a minimum, and 10.0% is what I've got. So I might add a bit of nose weight; It'll take 125 g to get to 12%.

 

[boatgeek]

One, thanks, I'll check.
Two, HOLY CRAP!
View attachment 645947

It looks like I'll be OK. The static margin with motor installed is 2.04. I like percent of rocket length better than caliber, and I think 10% is a minimum, and 10.0% is what I've got. So I might add a bit of nose weight; It'll take 125 g to get to 12%.

Wait, wasn't this going to be the one with the half-heart fins? Maybe I missed something.

 

[kjhambrick]

Whew !

Thanks @Upsrocketman

I loaded the Rocksim file into OR and those default fins from LOC were messing with my OCD

Even when the fins were fixed and I loaded a Loki 54-2800 L-1040-LR in the tail, the rocket should be plenty stable ( 1.5 Cal ) on the way to 10k feet at Mach 1.46 or so

I am curious about the Electronics Capsule near the forward end of the upper tube, @jqavins ...

It looks like an interesting idea.

What do you have in mind ?

Thanks for the build thread !

-- kjh



EDIT: p.s. I'll be happy to share the iris.ork I came up with if you want it ...

 

[jqavins]

Wait, wasn't this going to be the one with the half-heart fins? Maybe I missed something.

This is the one that was going to be, and I considered reconsidering and sat on the fence. Then the kit arrived and I held a half heard up against a fin from the kit, and it looked at least a third smaller. So stock it is. I'll use the half hearts for something else. Stay tuned for another build thread starting tonight.

 

[jqavins]

The electronics capsule is built into a section of 29 mm brue tube with a bulkhead glued in at one end and a pair of threaded rods to secure a bulkhead on the other. It was built by a friend for an old project, and I'm repurposing it with my GPS tracker.

I will suspend it by a piece of paracord from the bottom of the nose cone, and the one CR keeps it from swinging.

 

[kjhambrick]

The electronics capsule is built into a section of 29 mm brue tube with a bulkhead glued in at one end and a pair of threaded rods to secure a bulkhead on the other. It was built by a friend for an old project, and I'm repurposing it with my GPS tracker.

I will suspend it by a piece of paracord from the bottom of the nose cone, and the one CR keeps it from swinging.

Interesting !

I will stop distracting you but I look forward to your build thread

NSL West is sooner than we think ... better get to work !

-- kjh

 

[-Slick-Ice]

There are a bunch of great 38/54mm loads for the 4" IRIS. Straightest flying rocket I have.

 

[conneryc]

There are a bunch of great 38/54mm loads for the 4" IRIS. Straightest flying rocket I have.

I concur. I'm putting mine up on a K550 this weekend. Rocksim says 11,000'.

 

[kjhambrick]

I concur. I'm putting mine up on a K550 this weekend. Rocksim says 11,000'.

View attachment 646548

Rocket Envy !

My old 4-inch Iris only got about 9,000 ft on a K550.

But it was a BEAUTIFUL flight with that majestic pillar of white smoke and long, loud flame

-- kjh

 

[jqavins]

MUCH belatedly starting to build. First thing was cleaning my work surface. No pictures.

The instructions advise that some "light sanding" might be needed for a good fit of parts. A test for showed that the fin locking notches in the CRs would need more than light sanding, so I got out what I consider to be an underused tool in rocketry.

One notch is done, nice and easy, seven to go. A ham and cheese sandwich, a Mexican Coke, and some music are at my elbow, and we're off to the races.

 

[NTP2]

MUCH belatedly starting to build. First thing was cleaning my work surface. No pictures.

The instructions advise that some "light sanding" might be needed for a good fit of parts. A test for showed that the fin locking notches in the CRs would more than light sanding, so I got out what I consider to be an underused tool in rocketry.
View attachment 648476
One notch is done, nice and easy, seven to go. A ham and cheese sandwich, a Mexican Coke, and some music are at my elbow, and we're off to the races.

Ohhh my, this is truly a speed run. 5 days! Or less!

 

[jqavins]

It will help that I have no expectation of doing any finishing; it will fly as naked as naked gets. And there's no glassing needed.

Well, very nearly as naked as naked gets. One fin has a crushed dent that was just too much for me. I'm all out of wood filler. But I do have some wood meal that I got as a freebie from Skylighter many years ago, so I mixed some with Tightbond to the proverbial peanut butter constituency and filled the dent with that.


After corrective filing to the fin locking slots, the centering ring's IDs, the middle CR's OD, and the coupler bulkhead diameter, here is the full up dry fit. (I'm not impressed with the "Precision" part of LOC Precision's name.)


Now it's read the directions again (I did read all the way through a couple of hours age) and start putting this puppy together.

 

[jqavins]

After my last experience with my current bottles of BSI 30 Minute epoxy, I placed the bottles in the refrigerador. Today is not as hot a day. Nevertheless, I had my doubts about its working time, and a good thing it is that I did. I didn't get ten minutes (I'm not sure I got five) before it was rubbery. But I had planned for that.

It took two mixes with about 20 or 30 minutes in between to get the motor mount assembled. Here it is.

The shock cord is also installed at both ends, the forward CR and the coupler bulkhead. The instructions say to epoxy the eye bolts, and I'm not sure what that's intended to mean. I used the provided washers in the obvious manner, sandwiching the wood, then wiped some epoxy into the bolt's thread before putting the nut on, like Loctite; that's not going anywhere.

I think I'll relabel the bottles as five minute, and buy some new 30 minute. The five minute certainly has its advantages.

I think I can finish this puppy tomorrow. And maybe I'll even be able to get the IO done in time for next weekend too.

 

[jqavins]

Well, ain't is always the way?

I used the fin tabs to ensure perfect spacing between the CRs, and the interlocking notches guarantee everything is straight, right? Well, no. The centering rings have a slight angular offset, so now I'll have to widen the notches. Which lessens their effectiveness somewhat.

Damn!

 

[jqavins]

I've been poking a bit at fixing the fin fitment, and I'm out of steam for the night. I'll go to bed a little early and hit it after work tomorrow. Details tomorrow.

 

[jqavins]

I forgot that I have a commitment tonight, so I'll get very little if anything done today.

Back to yesterday, I got the notches widened, one with a file and the other three with a coping saw. Test fit showed that a little more filing was needed. Then started removing fillet epoxy from directly beneath the notches so that it doesn't interfere with the fin roots. Chip and cut a little here, stop for supper, chip and cut a little more, stop for a break, chip and cut a little more, take another break. When that was done I did another test fit, and discovered that one notch on on CR was a tiny smidge too close to the other ring, so did another tiny bit of filing on one fin tab, and marked both the fin and the aft CR at that notch so I'll know where to put the special fin when the time comes.

And that's when I decided I'd had enough for the day. I had thought I might get the motor mount installed, but thought better of it. I had thought that tonight I would 1) do yet another fit check of the motor mount and fins, 2) install the motor mount, and 3) install the fins today. Now I know I won't have time for that until tomorrow, and maybe I'll get the bulkhead epoxied into the coupler. Wednesday night for that stuff and get the fins installed if I'm quick, but I will avoid rushing.

It won't be ready to launch Thursday, opening day, but I'm still confident that it'll be ready by Saturday.

To be clear, all fitment problems after those in post #15 were corrected, the rest have been all my own fault. That stuff was on LOC, the rest is on me.

 

[loopy]

Personally, I like things to be a bit tight and needing to be sanded down a bit. Wood/cardboard will keep changing with conditions like humidity and what not. What fits perfectly at the factory then shipped to the other side of the continent might now be a sloppy loose fit, or could be tight. Err on the side of too small since that can be easily fixed, I say.

I'm glad I'm not the only one that had issues with the fin slots in the rings shifting and needed to be...um...adjusted...lol

 

[jqavins]

To the contrary, I'm not glad at all that I'm not the only one. I'm sorry anyone else has had to experience the same frustration that I've inflicted on myself.

 

[loopy]

To the contrary, I'm not glad at all that I'm not the only one. I'm sorry anyone else has had to experience the same frustration that I've inflicted on myself.

Everything is a learning experience.

 

[jqavins]

No progress yesterday. Got home at 6:00, got dinner on the table at 7:00, virtual tabletop RPG from 7:30 to 10:30, lights out at 11:00.

LDRS looks like an at least partial wash-out. I'm still determined to get this done on time, but there may not be any opportunity to fly it.

 

[jqavins]

Marked rail button locations last night. (The farthest aft mark I won't use.)

Backed the tube up with the coupler and drilled. I managed to make dimples in the coupler without going through. I gave the holes a light sanding inside and out to remove the fuzzy burs. No exciting picture of holes in cardboard.

Next I put the T-nuts in with CA; It was going to be a while before I got to a step beyond this, and mixing up one or two grams of epoxy did not seem worth doing, as this is a low stress situation. Two opposed drops of thick around each flange, then a drip of thin from the outside to harden the cardboard where it was drilled.


The hole in one of the buttons was undersize, so I drilled it out with the same bit that I had in place for the holes in the tube, and put the buttons on.


So, you may ask, why did I install the buttons now? Mainly because I won't be able to after the motor mount is installed. Second, the T-nut flanges infringe on the inside of the tube, so the CRs need help getting past them, and I need to take care of that before I mix epoxy for the next big step, putting the motor mount in.

I filed depressions into the outer edge of each ring, just deep enough to slip the ring past the flange easily, testing as I went so I'd know when to stop.


Next came one last and final fit check before proceeding, and then dinner. I've been typing through dinner, will now have a drink and desert, then get back to it.

 

[jqavins]

After my two prior fiasci with my old BSI 30 minute epoxy, I bought some new. It's a hot evening here in the corner of the three season porch that serves as my workshop, so I'm cooling the bottles in a pot of cold water. Please stand by...

 

[jqavins]

OK. Here we go.

I taped over the threads of the retainer, made sure my space was clear and pieces at hand, and stripped to my underwear; epoxy on my skin will come off eventually, but it will never come out of my nice shirt and pants. I bundled up the shock cord and stashed in inside the motor tube to keep it out of my way and out of harm's way.

I didn't know how much epoxy to mix up, so I erred on the side of planty. 20 grams. With a long stick, I smeared a ring of epoxy well forward of the fin slots, a little short of where I measured the forward CR would sit, so it would be wetted by passing through the ring on the way in. I inserted the motor mount enough for the middle CR to be inside, then put a ring of epoxy at the opening, and pushed the motor mount the rest of the way in. Then immediately started on the fins, doing the specially fit one first, buttering up all the segments of the root edge then working it into place.

Well, I should have put the mixing cup into the cold water bath between applications, because it started to thicken up while I was buttering up the second fin. I got that one done, then tossed the rest of that batch. 20 grams would have been enough had I kept it cool.

I quick mixed up 10 more grams, got the other two fins in, filleted the back end, and got the bulkhead into the coupler.

That's the big hurdle cleared. I now declare this rocket mostly done. I still have fin root fillets to do, and the various odds and ends, but the hard part is done.

 

[NTP2]

OK. Here we go.

I taped over the threads of the retainer, made sure my space was clear and pieces at hand, and stripped to my underwear; epoxy on my skin will come off eventually, but it will never come out of my nice shirt and pants. I bundled up the shock cord and stashed in inside the motor tube to keep it out of my way and out of harm's way.

I didn't know how much epoxy to mix up, so I erred on the side of planty. 20 grams. With a long stick, I smeared a ring of epoxy well forward of the fin slots, a little short of where I measured the forward CR would sit, so it would be wetted by passing through the ring on the way in. I inserted the motor mount enough for the middle CR to be inside, then put a ring of epoxy at the opening, and pushed the motor mount the rest of the way in. Then immediately started on the fins, doing the specially fit one first, buttering up all the segments of the root edge then working it into place.

Well, I should have put the mixing cup into the cold water bath between applications, because it started to thicken up while I was buttering up the second fin. I got that one done, then tossed the rest of that batch. 20 grams would have been enough had I kept it cool.

I quick mixed up 10 more grams, got the other two fins in, filleted the back end, and got the bulkhead into the coupler.

That's the big hurdle cleared. I now declare this rocket mostly done. I still have fin root fillets to do, and the various odds and ends, but the hard part is done.
View attachment 648935

When do you leave for LDRS?

 

[jqavins]

Thursday morning. And I head home Thursday evening. And I go back Friday morning. And so on. (It's less than an hour drive each way.)

 

[-Slick-Ice]

This might end up getting built at LDRS

 

[jqavins]

The plan for tonight is to do the fin fillets. I'll use more of the fresh 30 minute epoxy, thickened with chopped glass fibers, and kept cool in the cup. I also hope to glass the IO and/or repair Slava Ukraini, and repair some very minor damage on my Bid Daddy.

The four flights I really want to get in during LDRS are:

1. Big Daddy on an F motor to get plenty of altitude, using it as a practice run with the JL Chute Release.
2. IO on an H motor to affirm my L1 status in my own mind. I haven't flown any high power since I got the L1 many years ago, and that flight did not go perfectly. Frankly, the witness made a mistake in signing off on the it. I'm not giving the pin back, but I want one good L1 flight before the L2 attempt, just so I feel legitimate.
3. The Iris for the L2.
4. Slava Ukraini, because it's been a long time coming and it'd be great to launch in front of a good crowd.

They're all close to ready. They won't all be ready tomorrow, but I think that getting them all in by Sunday is realistic, weather permitting.

This might end up getting built at LDRS

No, this will end up getting finished during LDRS, at home in the evenings. I'm actually right on schedule, though I could have finished tonight, ahead of schedule, had I not taken last Saturday off.