4" LOC IRIS - Build Thread

[noahapiraino]

So I've been reading a bunch of the build threads here and finally decided to try and write my own, the only issue is that I've already built most of the rocket so this will mostly be a build summary after the fact.
Also, I am currently a university student and living in a dorm where I'm a bit short on working space as you can imagine, so please excuse any background messes I might have forgotten in photos.

I'd been eyeing this kit for a couple months since I started working on my Zephyr for my level 1 certification. I finally bought it, along with a 38mm LOC-n-ring motor adapter, and an electronics bay to convert it to dual deploy. After flying a bunch of smaller kits and certifying with motor eject, and putting together my own flight data logger, I wanted to finally fly a rocket that used electronics for deployment. My original intent was to fly this for a level 2 certification, but after building it and seeing more motor prices (college student budget), I'll probably be sticking to some I motors for now and use it to learn more about electronics and dual deploy, though it could still fly a certification flight eventually!



It's one thing to read dimensions on a website, but everything always looks bigger in person!
Here's the first dry fit of all the parts, standing next to my Zephyr. Over 6 and a half feet tall! With a 4" diameter, it works out to 1/3 scale of the real thing.



There's barely enough floor space for me to open up the parachute...



and the motors keep getting bigger.

I started off by sanding down all the centering rings and bulkplates, and epoxying the electronics bay together.



The electronics bay (without any actual electronics yet!) came out heavier than all my other rockets except for the Zephyr. I guess that's what all the metal and extra wood will do for you.



Then we epoxy the switchband onto the electronics bay



I was debating for a while about whether or not to use the switchband because it does technically bring it out of scale, but I ended up deciding touse it because I felt it would be a little more convenient to work on to have the rocket easily split on either side of the bay, rather than have to remove screws to take the bay out of one of the body sections.

 

[noahapiraino]

I didn't realize we're only allowed up to 10 attachments per post so I'll have to continue this in multiple parts.

Next up we put the motor adapter together, as well as epoxied the main motor mount centering rings in place. I did remove the outer glassine paper layer from both tubes before epoxying. I really like how the LOC-n-ring adapters get bolted into place using the motor retention already built into the rocket itself, it's very convenient. I was also able to use the adapters centering rings as spacers to keep the aft centering ring(s) nice and level while the epoxy cured.



And then another test fit of the fins before the centering rings cure fully to ensure everything is still aligned well.



Next up we expanded the hole on the bottom of the nosecone enough to screw and epoxy in an eye bolt to attach the shock cord.



On all my previous rockets I've tried to round the leading edge of the fins, but I've always struggled to get a good radius so it's more like they have rounded corners rather than rounding the entire edge down to a circle. This time I decided to sand the leading edges down to a point both because I felt like it may be easier to do consistently, and I felt like it would match the look and feel of the rocket better.
I measured and marked a line on both sides/faces of each fin, then also marked a triangle on the edges to connect those lines with the center of the leading edge. These were good enough guides I could hold the angle relatively well with a sanding block and get a nice symmetric point on all the fins.



After some issues laying internal fillets on the Zephyr, I decided this time I would try building the fin can first and then installing it into the body tube.
There was enough play with the fins even with the slots in the centering rings that I wanted to use an alignment jig, but I couldn't easily make one big enough for these fins. I ended up using a small cardboard one at the top, but then the bottoms of the fins I taped down to the table and used a metal ruler to square and align opposing fins.

 

[waltr]

Looking forward to the rest of your build.

I am currently building a 4" LOC Goblin for my L1 and do like the Fin lock system.

It takes some time but it is not hard to put a proper taper on the fin's leading edge. Having a nice flat bevel and crisp change does look great.

I did the 2.6" LOC IRIS with full Dual Deploy.
To keep length in scale I reduced to length of a BT by the length of the Switch band. Also needed to cut one of the BTs and do a couple to get the correct size of the Main Chute bay. Study and measure how much BT you need to get the main chute and cords into the upper section.

LOC's Decals for this are poor. I bought a set from StickerShock23 to have both the "IRIS" and "Atlantic Research" markings.
https://stickershock23.com/product/atlantic-research-corp-iris/

 

[noahapiraino]

Next up were vent holes for the altimeters, shear pins, rail buttons, and screws to fix the nosecone to the body tube since we're splitting in the center.



Followed by epoxying the motor mount/fin assembly into the body tube, and capping it off with a piece of coupler tube per suggestion on a different build thread I read here. I don't have any clamps at school with me so I ended up just using tape to hold the body tube pieces against the aft centering ring, but it worked great in the end.



Then we balance the whole thing precariously to lay down fillets on each of the fins.

 

[noahapiraino]

Looking forward to the rest of your build.

I am currently building a 4" LOC Goblin for my L1 and do like the Fin lock system.

It takes some time but it is not hard to put a proper taper on the fin's leading edge. Having a nice flat bevel and crisp change does look great.

I did the 2.6" LOC IRIS with full Dual Deploy.
To keep length in scale I reduced to length of a BT by the length of the Switch band. Also needed to cut one of the BTs and do a couple to get the correct size of the Main Chute bay. Study and measure how much BT you need to get the main chute and cords into the upper section.

LOC's Decals for this are poor. I bought a set from StickerShock23 to have both the "IRIS" and "Atlantic Research" markings.
https://stickershock23.com/product/atlantic-research-corp-iris/

Thanks for the decal link! I'll definitely have to get those before I'm finished. Do you find that it's necessary to keep the main chute payload bay as small as possible? I was planning to just have the electronics bay split the rocket right in the center. I've had issues cutting tubes and thought it would work just fine to leave the upper section as is.

 

[waltr]

The original IRIS had bolt on fins so the fin to BT has no fillets. Guess you are going for way back scale... nothing wrong with this and good to build to fly.

What are you using for fillets? Since most epoxies even with fillers tend to run until start to set, it is good to position the fin at 45° and do two fillets at a time. This way the epoxy settles into the fin/BT joint.

My go to fillet compound is RocketPoxy.

Do you find that it's necessary to keep the main chute payload bay as small as possible? I was planning to just have the electronics bay split the rocket right in the center. I've had issues cutting tubes and thought it would work just fine to leave the upper section as is.

After I see you putting rivets on the Nose I am not sure how you are doing Dual Deploy...

Main chute bay needs to be large (long) enough to fit chute, Nomex blanket and shock cord. So my comment is to ensure it is large enough to hold all this.

Typical DD is split the rocket below Ebay (middle) to eject Drogue chute at apogee. Then at pre-set altitude, eject nose with main chute.

Is this what you are planning?

If you are doing 'stand back scale' then an added inch of length will not be noticed.

 

[noahapiraino]

The original IRIS had bolt on fins so the fin to BT has no fillets. Guess you are going for way back scale... nothing wrong with this and good to build to fly.

What are you using for fillets? Since most epoxies even with fillers tend to run until start to set, it is good to position the fin at 45° and do two fillets at a time. This way the epoxy settles into the fin/BT joint.

My go to fillet compound is RocketPoxy.



After I see you putting rivets on the Nose I am not sure how you are doing Dual Deploy...

Main chute bay needs to be large (long) enough to fit chute, Nomex blanket and shock cord. So my comment is to ensure it is large enough to hold all this.

Typical DD is split the rocket below Ebay (middle) to eject Drogue chute at apogee. Then at pre-set altitude, eject nose with main chute.

Is this what you are planning?

If you are doing 'stand back scale' then an added inch of length will not be noticed.

For fillets I'm only using BSI epoxy since it's all I have easily accessible for now and I haven't built quite enough to justify the higher entry cost for other epoxy systems, though I do plan to eventually. My thinking with having the fins up and doing a whole fin at a time was that it would allow me to get the fillets even/symmetric wrapping around the leading edge of each fin since I felt that would be noticeable if they weren't quite the same. I know a thicker epoxy would be better here to hold a nicer shape and they definitely flatten into the body tube a tiny bit, but they feel plenty sturdy still.

For dual deploy, I'm using the entire upper of the two body tubes as a payload bay so it is more than large enough to hold the main chute, shock cord, and chute protector. What I had planned on doing was to split below the electronics bay for drogue, then above the electronics bay for main, with the nosecone fixed in the upper body tube section. I could change that to fix the electronics bay in the upper body section and have the nose cone eject if that would be better? From a few examples I found while researching it seemed as though either of those options would work so I opted to fix at the nosecone because I thought it would be easier/more convenient to be able to full open the electronics bay without having to unbolt it from a body section.

Trying to draw it out what you're describing would be something like this then:
>== ----- []== ----- >
while what I was planning would be more like this:
>== ----- [] ----- ==>
where square brackets are the electronics bay, equals are body tube, and hyphens are shock cord.

edit
Looking again if needed I can very easily just flip around the upper body tube section and reuse the holes I've already drilled for shear pins and bolts so no issues either way.

 

[MidOH]

I'm added an extra coupler inside my booster. Will have a ply wall with my eyelet for the shock cord. I can't fit my arm down the tube to reach the motor mount IIRC. With the eyelet up higher, easier to service the cord, and less powder needed.

 

[waltr]

For fillets I'm only using BSI epoxy since it's all I have easily accessible for now and I haven't built quite enough to justify the higher entry cost for other epoxy systems, though I do plan to eventually. My thinking with having the fins up and doing a whole fin at a time was that it would allow me to get the fillets even/symmetric wrapping around the leading edge of each fin since I felt that would be noticeable if they weren't quite the same. I know a thicker epoxy would be better here to hold a nicer shape and they definitely flatten into the body tube a tiny bit, but they feel plenty sturdy still.

For dual deploy, I'm using the entire upper of the two body tubes as a payload bay so it is more than large enough to hold the main chute, shock cord, and chute protector. What I had planned on doing was to split below the electronics bay for drogue, then above the electronics bay for main, with the nosecone fixed in the upper body tube section. I could change that to fix the electronics bay in the upper body section and have the nose cone eject if that would be better? From a few examples I found while researching it seemed as though either of those options would work so I opted to fix at the nosecone because I thought it would be easier/more convenient to be able to full open the electronics bay without having to unbolt it from a body section.

Trying to draw it out what you're describing would be something like this then:
>== ----- []== ----- >
while what I was planning would be more like this:
>== ----- [] ----- ==>
where square brackets are the electronics bay, equals are body tube, and hyphens are shock cord.

edit
Looking again if needed I can very easily just flip around the upper body tube section and reuse the holes I've already drilled for shear pins and bolts so no issues either way.

Ok, As I said, if way stand back scale then fin to BT fillets ar fine.

Now understand how you plan DD. That should work to pull the chute out of the upper BT.
Most Mains in DD are deployed by blowing off the nose, leaving the BT riveted to the Ebay.

Here is a pic of my 2.6" LOC IRIS. Note that the decal text is a bit too large for scale but ok.
If you want closer to scale calculate the height of the letters in "IRIS" from a photo and state that in your order to Stickershock23. He will scale the artwork to what you want.

 

[noahapiraino]

Ok, As I said, if way stand back scale then fin to BT fillets ar fine.

Now understand how you plan DD. That should work to pull the chute out of the upper BT.
Most Mains in DD are deployed by blowing off the nose, leaving the BT riveted to the Ebay.

Here is a pic of my 2.6" LOC IRIS. Note that the decal text is a bit too large for scale but ok.
If you want closer to scale calculate the height of the letters in "IRIS" from a photo and state that in your order to Stickershock23. He will scale the artwork to what you want.

I'm not super concerned about scale, appearing scale at a distance is fine for me here and I've already done the fillets so I'll stick with them, that would be a bit tough to change at this point anyway.
After talking to some other people a bit I am going to switch the dual deploy setup around to how you described, riveting the payload tube to the electronics instead of the nosecone.
That's a good idea about scaling the artwork, I'll be sure to do that. Your IRIS looks really nice! What did you use to build up those bands around the fins and near the silver paint transition?

 

[waltr]

The fin bands are strips of paper card (100#) stock glued (white glue) together.
There are about 4-6 strips to build up to correct thickness.

The Aluminum nose & tail section is Createx Quick Silver over their Gloss black. The Quick Silver paint is pricy and both require an airbrush to apply. But is one of the better paints to obtain a polished aluminum look.

Ok on changing the DD main deployment to nose eject. As you probably know from reading the forum, TEST, TEST, TEST the deployment. Even then I find things do fail to work.

 

[noahapiraino]

Absolutely, I'm hoping to be able to ground test ejection charges sometime this weekend and will try to have ejection as reliable as I can get it before even considering flying.

Back on the build, after comparing available altimeters I ended up settling on an Eggtimer Classic, with an Eggtimer Quark as a backup. Both of these were kits that had to be assembled. The Quark was actually my first surface mount solder project, so the joints aren't the prettiest, but it started right up and both deployment channels are working as expected.



The Classic I did actually have some issues with, after assembling it, it wouldn't boot up. All the solder joints looked good but I decided to reflow most of them just in case and it started working, but only intermittently. Occasionally it would chirp or a light would flash, sometimes it would turn on fully and start beeping, and other times it would be silent. I'd worked with bare atmega chips before and had issues with them expecting external clocks when I was trying to run them on the internal oscillator, so as a lucky guess the issues I had felt like they were clock related, as if it would get some clock cycles in and then stop halfway through starting, explaining the random beeps and flashes.
What I ended up doing to try and troubleshoot was connect an external clock from another microcontroller to the clock pin of the processor on the eggtimer, and it began booting reliable every time. After seeing that I decided to replace the resonator on the board, and now it works perfectly.

For the electronics bay, I have 3 vent holes equally spaced around the switchband. In order to turn the electronics on and off I wanted to use screw switches through these vent holes. After reading through another thread with people showing off what switches they use, I ended up modeling my own 3D printed bracket to hold some screws in alignment with the vent holes, which could then close a circuit between two brass nuts on either side of the bracket.



I then secured both altimeters to the sled with some nylon standoffs.



And that's where we're currently at. Next up I'll have to switch around the payload bay tube for the better recommended dual deploy configuration, and I'll also be adding brass shims to the body tubes for the shear pins to help prevent any tearing.

 

[waltr]

Looking good.

I also use Eggtimers but since I have been doing electronics for over 50 years building them is easy.
Good troubleshooting the oscillator issue.

Interesting screw switches, like them. I also make my own screw switches from a piece of double sided PCB and a brass nut.

Shear plates are a good idea. I haven't used them yet. In LOC cardboard tubes I drill and tap for 2-56 nylon screws then harden the tube with thin CA and re-tap. So far has worked.

 

[noahapiraino]

It's been a few weeks but I finally got the chance to get some more work done.

I don't have pictures of them, but I did make some small brass shear plates and epoxied them inside the body tubes, as well as on the paper walls of the coupler tube. I also got some plastic rivets to fix the electronics bay to the payload tube. That was a little tricky, the walls of the coupler are so thick the rivets wouldn't expand at first. What I ended up having to do was use a countersink bit by hand on the inside of the coupler tube to create space for the rivets to open up. They're a tight fit, but it works. I was also able to attach some PVC caps to use as ejection wells, and do ejection testing.



For the drogue, I started with 0.75g from calculators, and it worked perfect first try. I did do a second test just to make sure it was repeatable.

View attachment drogue.mp4















Then for the main, I started with 1g, but the parachute got hung up on the edge of the tube. I tried bumping it up to 1.1g, then 1.2, but the same thing kept happening - the nosecone would pop off very forcefully then get pulled taught by the stuck parachute. I backed down to 1.1g and changed how I packed the chute, making it longer and narrower than before. After changing how it was packed, it ejected nicely and repeatably.

View attachment main.mp4















Now that that's definitely working, all that should be left to do is paint! We're in the middle of finals at school right now, so I'll hopefully be able to start that in a couple weeks (weather dependent, since I only have spray paint and have to work outdoors).

 

[waltr]

Good work on the ejection tests. I have found that the chute needs to easily slide out of the tube. Then the Nose cone momentum will pull out the chute.

Also have found that either doing taped shock bundles or braid the cord is helpful to reduce the stress when the cord to pulled to fully extended.

 

[noahapiraino]

It's a few months later than I'd originally planned, but the IRIS has finally flown!

Painting and decals (from stickershock) were completed back in mid June, but due to various issues ranging from covid to launch cancellations, it took until September to make it to a launch.





The flight was a Level 2 certification flight on an Aerotech J250 motor at Rocketry South Carolina's launch site in Dalzell, SC. It was a great flight up, all the ejection charges went off and parachutes deployed smoothly, and it landed just a few minutes walk from the pad. The drogue did deploy much earlier than intended, but after reviewing the footage and altimeter data, it seemed to be caused by the motor ejecting early. The motor delay was set to 12 seconds, but went off only 4 seconds after burnout. Thankfully the drogue was small enough and there was enough shock cord length that no damage was caused to the rocket, despite it still moving very fast when it split.



View attachment vid2.mp4

And thanks to Wes from the launch site Facebook page for these next few photos:

 

[waltr]

Goods good with the stickshock decals and very nice flight.
Congrats on your L2.