IRIS Project

This is my latest build, 1/4scale IRIS. Sorry no build pics, I really suck at that; Once I get on a build roll I don't stop...For pics or other needed breaks. Anyway... Fins are G10 as are the bands. Airframe and MMT are phenolic. Bulkheads are Carbon Fiber with Honeycomb core. Plastic nose cone. Power is 38mm with DD recovery. Pics are a full shot and some detail (as much as an IRIS has ignore the dates )

Nice looking model with good detail! So, it's about 5 feet tall and about 3 inches in diameter. I'm wondering where you got your bulkheads and what is honeycomb core?

One of my all-time favorites.

Looks like you took time to put some scale detailing in there, too.

It looks really good and I bet you're proud of the result.

A few questions:

• What did you use for your reference data
• Who/how did you do the graphics
• How did you do the silver parts

Greg

Thanks! The bulkheads are scratched by me, I'm a composite tech by trade so dumpster diving at work is like a trip to the hardware store. In a nutshell, The core is an aramid fiber honeycomb sheet about 3/16" thick with 1/8" hex cell structure, laminated on each side by 2 plies each of 3K Carbon Fiber pre-preg, 8 harness twill, and cured in a vac bag in an autoclave at 250degF and 100psi. Makes for an incredibly strong and light sheet.
Reference data was a combination of Drawings from ROTW, a couple of color photos I pulled off of the web and a quick trip down the road to the visitors center at Goddard Space Flight. They have, what I've been told, is the last remaining IRIS round on display so I took some measurements. Sad as it's outside and in terrible shape. I heard there was talk of doing a refurb.
Graphics are by Mark at StickerShock. His quality, service and prices are hard to beat.
Aluminum on the nose cone is paint and Aluminum foil tape (2"wide) went on the tail end and was burnished down with a balsa strip.
I also have an Aero Pack Motor retainer. DD will be handled by an Adept 22.

Beautiful!

What did you use for the dummy bolts holding the fins in?

BigBlueDart said:

What did you use for the dummy bolts holding the fins in?

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Actually they're not dummies. From the measurements I took off of the round at Godard, I scaled down and found Du-Bro 2-56 hex socket head bolts were spot on diameter and just a hair tall (close enough!). I had debated on actually drilling & taping the airframe and hard bolting the fins but experience has taught me that perfectly aligning 32 little holes on fins with 32 little holes on the airframe would be a PITA. So the tabs in the fin base are drilled for a clean slip fit and the bolts are cut to 1/8" and CA'd in place. Fin construction was TTW and bonded to the motor tube so the extra mount strength of the bolts, though cool, would have been unneeded. I was going for the look anyway. The IRIS has so little surface detail to begin with that every little bit I can add to the model is worth it.
With all of that said I get many small bolts and hardware from here https://www.scalehardware.com/ .

Troy,
What size motor are you going to fly on?

Sounds cool! I'm already planning on using #0 flat head screws for the bolt pattern on the nosecone. I guess I might just calculate what size screw would be closest to a 1:3 scale for the fins. Probably take the same approach as you and just cut the heads off and glue in place.

aerostadt said:

Troy,
What size motor are you going to fly on?

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38mm, High "I" to low "J". This thing is coming in a little heavier than I hoped (something in the neighborhood of 4.5-5.0lb). First flight on an I216 or maybe an I540.

You should build the Booster for it, too, even if it's only for display !

Ez2cDave said:

You should build the Booster for it, too, even if it's only for display !

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I've been thinking about that actually. I have a 3" Aerobee 150 I'm building a booster for. I've a number of flights on it and decided it'd be a good candidate for my first 2 stage HPR. When I built the IRIS I did so with this option in mind. I just don't want to have clear fins on the booster. I've seen it done without but they were significantly larger (around 7.5"-8.0"). We'll see.

Here's a 3.25" diameter IRIS flying on 7 C6 motors stage to an Aerotech F. It it certainly possible to do an IRIS this size with no fins.

Model by John Brohm, photo by Chris Taylor of NARAMLive.com.

TheAviator said:

Here's a 3.25" diameter IRIS flying on 7 C6 motors stage to an Aerotech F. It it certainly possible to do an IRIS this size with no fins.

Model by John Brohm, photo by Chris Taylor of NARAMLive.com.

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Now thats awesome too! Anybody got the dimensions or a good OR/Rocksim file they want to share, this rocket is definitely one to add to my build pile.

rharshberger said:

Now thats awesome too! Anybody got the dimensions or a good OR/Rocksim file they want to share, this rocket is definitely one to add to my build pile.

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Check out Rockets of the World, page 137 for Peter Alway's scale data. Additionally, NARTS has a small data packet on the IRIS including two B-size drawings and a color print available for $4. Or just get all of the small scale data packs for $20.

My 4" Iris is being built with the booster being a possibility down the road. Just a little unsure about weight distribution if I have to add enough battery in the lower section of the sustainer to ignite the stage. I figure I'd have a cluster of 6 or 7 29mm motors in the booster. But this is all a pipe dream until I finish building and then fly the main stage.

Btw, I've resurrected my build thread from over a year ago over in the HPR forum:

https://www.rocketryforum.com/showthread.php?63598-4-quot-custom-Iris-build

View attachment 3in IRIS.ork

rharshberger said:

Now thats awesome too! Anybody got the dimensions or a good OR/Rocksim file they want to share, this rocket is definitely one to add to my build pile.

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This is the open rocket file I worked up for mine. May need some tweaking.

Very nice looking model Troy. You definitely went for more detail than I did on mine.

I've got the rotw drawings but no dimensions for the widths of the motor reinforcing bands and fin bands (there are three on the real ones photo) and their STA locagkons. Does anyone have this info?

rharshberger said:

I've got the rotw drawings but no dimensions for the widths of the motor reinforcing bands and fin bands (there are three on the real ones photo) and their STA locagkons. Does anyone have this info?

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Get the NARTs small rocket data pack or just the IRIS pack. Everything you need to know is inside.

This is a good source: https://meatballrocketry.com/iris-scale-data/

stantonjtroy said:

This is a good source: https://meatballrocketry.com/iris-scale-data/

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Thank you for the link. I have been looking for some of that data forever.

Great Looking IRIS Troy.

Sorry to dredge up an old thread. Just had some questions about the fin bolts, again. Do you still have the size of the originals? Using some backwards calculations I figure if you are using 2-56 screws for a 1:4 scale, I should use 4-40's for a 1:3 scale. Any idea if that sounds right? Also, I see that on your rocket you only have the screws going into the rocket body at the base of the fins. On the drawings I have it appears that there are also screws going into the fins (and more of them). Is this true on the display model at Goddard? Thanks in advance.

I don't have my data digitized but Josh at MeatBall Rocketry did. Has measurements pictured as well: https://meatballrocketry.com/iris-scale-data/ . 4-40 sounds right. based on the round at GSFC, the tabs are molded/welded to the fins and the only bolts are through the tab into the airframe. With that said, I don't know if this round, like many display rounds, is representative of actual flight rounds. A lot of piecing together spare parts with little regard for design accuracy. Based on the other photos I've seen, it seems to accurate.