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Build Thread: LOC/Precision 3" Iris 38mm. "The Comeback Kit". First build in 20 years!

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Mach_Seven

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The situation: I was into rockets after receiving my first Estes kit at age 10, which I launched in the back yard and never saw again. I progressed with mixed success until my early 20's when I discovered HPR and Certified L1 with a nice 4" kit called "Falcon" (manufacturer escapes me). Then I never launched another rocket since. Why? Because life comes at you fast! Now I am ready to re-enter the hobby thanks to the wealth of information out there like this forum and many YouTube channels. I intend to be patient, methodical, and to learn best practices as I go. Please feel free to make suggestions or give advice! This is a "training" build!

Why the Iris?
I love the look of a four-fin rocket with classic styling. It is also very stable, not too big, easily modified, and very capable of good performance. It can take anything from an H to a J. Plus LOC has a great reputation.

Goals:
1. Join nearest Tripoli Prefect.
2. Hone construction techniques.
3. Learn best practices for everything from construction to recovery.
4. Certify Level 1 on maiden flight.
5. On-board video.
6. Document build and launch on Rocketry Forum.
7. Be patient. Enjoy the journey. No rushing to launch.

Modifications planned:
Aeropack 38mm to 3" aluminum finish tailcone retainer.
Avionics bay. (first time with any on-board electronics)
Dual-deploy and single-deploy capable.
Camera mounting.

Paint scheme:
As pictured but with a chrome paint for forward airframe and nose cone to match tailcone.

Planned motor hardware:
Cessaroni Pro38 Full Kit

Planned First Motor:
Cessaroni I-216 (I'm thinking a nice kick in the pants off the pad will help make for a stable flight)

Planned electronics:
Altimeters(s), tracker, camera.

Planned construction methods:
Fin can built outside airframe, seal avionics bay coupler with epoxy or CA, quality paint and finish.

01/31/2021 UPDATE: Still waiting on rocket and parts to be delivered.
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Mach_Seven

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Not pictured: various hand tools, drill, angle, long metal straight edge, fin alignment guide.
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AeroAggie

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What kind of mad man buys all the tools and supplies before starting a build? You're supposed to buy those as you go on 37 separate trips to Home Depot because "just need one more thing".
 

Mach_Seven

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What kind of mad man buys all the tools and supplies before starting a build? You're supposed to buy those as you go on 37 separate trips to Home Depot because "just need one more thing".
😂 A couple things about this statement:
1. This represents several trips already (also to Lowe's and Walmart and Dollar Tree and Big Lots....)
2. I'm trying to prevent making shady compromises and substitutions in lieu of an HD trip in the middle of a build. "Sanding sealer?!? The hell is that? I'll just put extra paint on it..."
3. It was a way to do "rocket stuff" while waiting for the kit and parts to show up.
 

Theory

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looks like you have thought this one through!

one piece to keep in mind, those aeropack tail cones can add a fair amount of weight to the aft end of your rocket, so be sure to check your CP / CG, especially considering that this is a cardbaord rocket and wont have a nice and robust FG nosecone to help offset the additional wight in the back,.
 

Mach_Seven

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looks like you have thought this one through!

one piece to keep in mind, those aeropack tail cones can add a fair amount of weight to the aft end of your rocket, so be sure to check your CP / CG, especially considering that this is a cardbaord rocket and wont have a nice and robust FG nosecone to help offset the additional wight in the back,.
I agree and I thought of that. I'm thinking the Av bay and whatever camera contraption I come up with in the forward section will help keep the CG forward, but I will be very mindful of that. I want straight, true flights!
 

Mach_Seven

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Fin Prep: I figured this would be a good project to get done while I'm waiting for the tailcone. After carefully sanding the leading edges down, I masked off a 1/4" strip around the three outer edges. Then I applied a generous amount of Gorilla Super Glue "Tough Impact Formula" and ran my pinched fingers down them to remove excess and smooth it out. I decided not to sand the trailing edge. Being 1/8" plywood, that needs strength for landing more than aerodynamics.
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I then masked off the root edge and about 1/4" along the base of the fin where fillets will be and filled with DAP Plastic Wood filler. It was quite thick, but I just dipped my finger in a cup of water and was able to thin it enough to get full coverage.

Sanded uniform and baby-bottom smooth with 250 and 800 grit. Ready for primer:
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Mach_Seven

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38mm fin alignment guide and body tube marking tool on it’s way from BadAss Rocketry!
 

Tractionengines

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Watch landing descent rate. With those big fins right at the back they are vulnerable. My Loc IRIS 2.25" maiden flight came down on the farm road for our launch site. Cracked a fin. Now fixed, but I increased parachute size from the LOC supplied one quite a bit.
Landing:
2_26_IRIS_E.jpg
Damage:
2_26_IRIS_F.jpg
 

Mach_Seven

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Watch landing descent rate. With those big fins right at the back they are vulnerable. My Loc IRIS 2.25" maiden flight came down on the farm road for our launch site. Cracked a fin. Now fixed, but I increased parachute size from the LOC supplied one quite a bit.
Landing:
View attachment 449088
Damage:
View attachment 449078
Good to know. Maybe I'll get a bigger one too. How's it fly otherwise?
 

Tractionengines

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I built and flew the 1", 1.6" and 2.25" LOC IRIS last summer. Great flights. They WILL weathercock because of being "overstable" from those 4- big fins. Speed off the rail, keeps them straight. Do some SIMs in OpenRocket and look at flight side profile.

Override the weights in OpenRocket as you build and keep checking CP / CG. With AV bay, Camera, Tracker etc. you will be shifting CG even more forward. Your tailcone will offset that but how much....need to SIM with accurate "as built" information.

[ I plan on building the whole IRIS fleet. 3in will be sometime this spring. ]
 

Mach_Seven

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I built and flew the 1", 1.6" and 2.25" LOC IRIS last summer. Great flights. They WILL weathercock because of being "overstable" from those 4- big fins. Speed off the rail, keeps them straight. Do some SIMs in OpenRocket and look at flight side profile.

Override the weights in OpenRocket as you build and keep checking CP / CG. With AV bay, Camera, Tracker etc. you will be shifting CG even more forward. Your tailcone will offset that but how much....need to SIM with accurate "as built" information.

[ I plan on building the whole IRIS fleet. 3in will be sometime this spring. ]
Thanks for the info. I figured she'd need a good kick off the pad. I'll look into OpenRocket. Haven't used it before. But It's on the list.
 

Mach_Seven

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Finally finished the fin prep. Pretty happy with the results. These baby's are SMOOTH!image_50376449.JPG
 

Mach_Seven

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The first permanent bond! I can't do much assembly right now as I am waiting on the tailcone and fin jig/body tube marking guide from Badass to get here. But I can do the forward centering ring. I just wanted to put something together...

Hey guys! I don't know if you're aware of this, but 5 minute epoxy is a sticky #&%*@ mess! And JB Weld is a runny, sticky #&%*@ mess! Make a note of it.
 

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neil_w

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Looks good so far.

You will find it easier to apply the wood filler to your fins if you thin some with water before applying. In the past I kept a small container around for this purpose, but now I just have a 4 oz tub of the stuff that I thinned out right in the tub, ready to go.
 

Mach_Seven

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Looks good so far.

You will find it easier to apply the wood filler to your fins if you thin some with water before applying. In the past I kept a small container around for this purpose, but now I just have a 4 oz tub of the stuff that I thinned out right in the tub, ready to go.
But if I did that, I wouldn't put on nearly as much and experience the joys of excessive sanding and that wonderful flour-like dust filling the entire house.
 

neil_w

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But if I did that, I wouldn't put on nearly as much and experience the joys of excessive sanding and that wonderful flour-like dust filling the entire house.
Don't worry, you'll still get plenty of that dust. :)

When I can hand-hold it, I sand that stuff while holding it in a garbage can, so most of the dust never escapes. It is nasty.
 
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richP

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Good choice for you kit. I have the same, and built it as a dual-deploy from the onset. It's flown on everything from H123 to J330s without any issues.
 
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Mach_Seven

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Good choice for you kit. I have the same, and built it as a dual-deploy from the onset. It's flown on everything from H123 to J330s without any issues.
Hell yeah! It's so versatile! I am making mine with a removable coupler and Av bay so it can be flown either way. Check the updates below! (posting now)
 

Mach_Seven

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Check out how versatile this rocket can be made with this simple mod. Thanks again to Jason at Loc/Precision for the great advice!
 

Tractionengines

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As an option to screws, you can use reusable plastic rivets. Just find one with a grip range that matches the thickness of what you are holding together.

rivet.png
The pin pushes in to expand the back side and hold together the items. Then you pry up the head to release it.

I have lots of sizes and get from McMasterCarr. But lots of vendors have some sizes...(can scratch paint around them depending how you pry them up to remove, or if tool slips.)
 

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Removable Coupler and Av Bay Project: After applying so much CA that I'd had enough of that smell thank you very much, I got started on making the removable coupler so I can swap it out for the Av bay and vice versa. Basically just made simple, careful measurements and used the switch band as a marking guide

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To mark the lines that align the screws and fins, I went old school! (Ya damn kids these days with your fancy alignment tools and your rap music)
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And we now have made this a very versatile rocket!
 

Mach_Seven

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So what did we really accomplish just now? And what's next?

 

Mach_Seven

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Tried to get the av bay assembled, but I didn't get very far. I think the threads are damaged as the nuts keep binding up. Any suggestions?
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Probably the most crucial measurement and mark of the project: motor mount fin guides. I used the Bad Ass Rocketry marking tool and fin alignment guide to get the truest possible lines.
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Mock-up of the fin can:
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