4" custom Iris build

Hey, all. I'm starting this thread after already being halfway through my build. And most of that was started a couple years ago, too, so not too many pictures available, yet. Anyway, the premise is to build a 1/3rd scale Iris. You know, that rocket that nobody outside of the model rocketry community knows exists. So I ordered the scale drawings online and started drawing up plans.

I'm planning on doing a dual deploy setup. Currently I'm thinking a booster section followed by a main section with altimeter bay in the middle. The nosecone acts as a payload bay for whatever the heck I end up putting in it. The fins are through the wall. I've got a 54mm motor mount. Probably leaving out important details, but I'm sure I'll get to them down the road.

Anyway, here is a quick pick of all/most of my parts so far:




I had another thread awhile back looking for advice on how to secure my bulkhead to my nosecone. This is what I ended up with:




I had assembled my motor mount with centering rings two years ago, so I don't have pics of that process. I also neglected any detailed pics of installing the threaded rod for the booster forward bulkhead, which did happen recently. But today I started tacking on the fins with fillets coming later. Here is the last fin being set up:




I mounted the fins one at a time by propping them up on blocks (with sheets of paper to shim to the right height). For this last fin I had to put these two tables together so one fin could pass between them while the last one is mounted.


Well, sorry for the skipped steps and lack of detail. I'm really bad at documenting. I've certainly benefited from the experience of a few here on the board and plan to look to you guys more as this project slowly progresses. Down the line I am even considering doing a 6 or 7 motor booster (again to scale). But that decision probably won't come until after I've flown this bird solo. Anyway, just wanting to share. I'll keep the thread updated as I'm able.

Oh, yeah. And here is my OpenRocket file for the project, in case you're interested.

View attachment Iris4.ork

With the fins attached I could add fillets:



Some might say I went overboard, but Christopher Walken disagrees:

BigBlueDart said:

Some might say I went overboard, but Christopher Walken disagrees:

View attachment 164964

Click to expand...

You know, I think every niche forum such as this ought to have a database of memes specific to their hobby.

The question for me now is to glass or not to glass. I'm considering doing tip-to-tip fiberglassing on the fins before putting the body tube over it all. The fins are 1/4" birch plywood and I plan on eventually flying this thing with a K motor, possibly even staged down the road. Any thoughts?

BigBlueDart said:

You know, I think every niche forum such as this ought to have a database of memes specific to their hobby.

The question for me now is to glass or not to glass. I'm considering doing tip-to-tip fiberglassing on the fins before putting the body tube over it all. The fins are 1/4" birch plywood and I plan on eventually flying this thing with a K motor, possibly even staged down the road. Any thoughts?

Click to expand...

I built a Yank Ent 4" Iris with their flexible phenolic and did smaller fillets than yours and then foamed the fincan. It has flown on a AT K805 to over 5600' with no problems. It weighs ~7lbs w/o motors. As a matter of fact there isn't an ounce of glass on the whole rocket. I did however mess up the booster and can only fit 6 grain motors in it. The 6XL is a little too long... :sigh:
Oh well. Next rocket...

Adrian

Thanks for your experience! Not glassing would definitely simplify the build for me. And expedite it, considering I don't have the materials and would have to buy them with money I don't have yet. My rocket might end up being a bit heavier, so I probably don't need to worry about the fins splitting open in flight. I may coat the leading edge with some epoxy clay or something, just to be safe.

Okay, so this has been dormant for a bit. I think my next step is to put the body tube over the booster section and fins. Unfortunately, I've already epoxied my rear centering ring in place. This is only my second HPR rocket with TTW fins, and I did this both times. So, I'm wondering if anyone has some other trick to doing internal fillets between the fin and body tube. And if I've already got pretty sturdy fillets to the MMT, just how necessary are the BT internal fillets?

Injection?

Yeah, I was thinking of something along those lines. Just get some of that epoxy that comes in two tubes and basically squirt some rivets on the inside along the length.

Well, it's time I blew the dust off this project and got it moving again.

I'll get some more pictures up soon, but there honestly isn't all that much progress since I was last working on this, apparently well over a year ago. I'm setting a harder goal to have this bird finished and flying by Spring. Main thing that is going to hold me up is being able to afford the parachutes and motor hardware, but in the meantime there is a good amount of finishing I can do on the body, especially with scale details.

The biggest change that I don't have a picture posted of, yet, is that the fincan section has the body tube on it, now. And that happened last year, too. Since then I've done some small amount of work filling in gaps around fins as well as some body tube spirals with epoxy clay. Just the past few days I've started working on some scale details, such as the bands around the fin area and the slight bulged section near the top where the nosecone is attached. I'll likely get some pictures posted tomorrow night when I get a chance to work on it a bit more.

The nosecone is nearly ready to paint. The only thing I need to do on that before moving forward is drill the bolt pattern holes around the base. I plan on using #0 size flat head screws, which are roughly to scale with the size screw used in the original (I had no idea until this project that there was such a thing as a #0 screw!). I'll drill the holes and countersink them slightly for the screws. Then I'll paint with some sort of aluminum metallic spray paint. And then the #0 screws will be glued in place.

The fin can will continue to get some false bands installed, including dummy bolts and brackets by the fins. The central tube just needs some filler material above and below the upper band on the lip to achieve the taper down to the body tube size. Once these are all done those sections will also be ready for painting and finishing.

One thing I'm still unsure about is how I'm going to configure my dual deploy avionics bay and exactly where it will be positioned in the central tube. I'll probably come back to this and get some advice from folks here as well as from my local club.

"just how necessary are the BT internal fillets?"

The pic of your motor tube internal fillets shows them to be massive. I would skip body tube internal fillets (glue on glue) and go with external fillets.

Nosecone coupler nuts, "dummy rings", etc. - I sense a hardware theme. It may be time for a rocket modelled after threaded rod.

Igotnothing said:

"just how necessary are the BT internal fillets?"

The pic of your motor tube internal fillets shows them to be massive. I would skip body tube internal fillets (glue on glue) and go with external fillets.

Nosecone coupler nuts, "dummy rings", etc. - I sense a hardware theme. It may be time for a rocket modelled after threaded rod.

Click to expand...

I've already done the body tube around the fin section. If I remember correctly I just tried to get a little epoxy through the crack to the inside. I'm sure it wasn't enough to call a fillet, but should be enough to keep the body tube in place. I filleted the external fin joints, too, but then sanded most of it down. That was mostly to just fill in gaps and seams.

Not sure I understand the threaded rod comment, but if you're saying my rocket is going to be heavy, you're probably right. I haven't weighed things yet, but probably will soon to get a better idea of how much my recovery system is going to have to handle. I'm inexperienced and this is all a learning process for me. A lot of things that I'll probably do differently the next go around to be more efficient. But for now I'm going to just keep pressing on so I can finish this project.

Just a few updated pictures:

Here is the motor mount section with the body tube installed.


A look at the bottom of the rocket to show some finishing around fins and body tube.


A look inside the top of the lower section with the bulkhead removed. (And yes, that is my gut at the bottom of the picture.)


Starting to add the bands around the fins. First the larger band, as I need to fill in above and below to taper. The other bands will come later.


A similar band at the top of the central section where the nosecone goes on. Also waiting for a taper to be added.


All sections of the rocket as they are today.

Testing out different mixtures of epoxy and microballoons. This is a departure for me, as I usually just bowl through and try new techniques directly on the rocket. The first attempt on the left was very pitted and the mixture was likely too thick. The next try on the right came out much smoother.

Hmm... maybe I need to update this thread?

Okay, so first I painted my nosecone almost a year ago (Feb, 2016):




Then I epoxied in the screws for the nosecone bolt pattern (I used #0 screws, which I didn't know existed until this project):

I finished adding the fin straps, making sure to keep them held down while the epoxy cured with some weights:




I also finally used the technique I was practicing earlier to add the bulges near the top of the body and down between the fins:






I also made some tabs to model the fin mount locations:





And these are the 4-40 screws that would go in after painting:

I had some rail guides that were the kind you attach using JB Weld. The problem was that the fin strap features I had added got in the way a bit, so I had to make the rail guides stand off more. I decided to add some extra layers of body tube:





After cutting them out and shaping them some more I attached them to the rocket:

The joint between my main body tube and the fin can section had a bit of a gap due to unevenly cutting the body tube. I decided to try fixing this by filling it in a bit with epoxy and filler. I wrapped the coupler in plastic wrap and then slid the body tube over it. Then I pulled the plastic back up and filled in the gap. The plastic protected the main body tube and kept the pieces from getting stuck. The result wasn't perfect, but it was much improved:

Main body tube primed, sanded, and painted white:

Those little tabs I made for the fins? Those were a pain in the butt, by the way. After initially gluing them on with super glue I filled in under them with epoxy and microballoons. A lot of work with sanding and a small file set and they were looking pretty good.

After all this I was ready to start preping the fin can for painting. First I filled the fins and sanded:




Next, I masked off the rail guides, coupler, and motor mount. That was followed by I don't remember how many cycles of priming and sanding:

Four different colors would eventually end up on the lower section. I started off with some metallic paint for the base:




Next I masked that off and got the red paint for the fins:

All this was going on over the course of the Spring. After that I entered another phase where I got busy in life and/or the weather wasn't good for painting. But at some point in the middle of everything posted above I also started working on my avionics bay:






And yes, I know that last picture of the back of my sled is hideous. This is my first avionics bay, so I'll likely look at some other designs and work on something more elegant for future builds.

Looking nice!

Thanks for sharing this with us.

So, it was last May when I first started with the red paint for the fins. I actually ran out of red and ended up with a poor finish. It wasn't until all the into November that I finally started getting back on top of things. I sanded down the red a bit to get a smooth surface again and then added a new coat which turned out well. Then I started masking it up, more sanding, and then white for the body:

I installed some 2-56 nylon screws up at the nosecone and down near the fin can as shear pins:

Masking for the final black paint, including lettering and logos. I cut the "IRIS" logo out by hand through the masking tape. After a friend saw me post that he offered his vinyl cutter, which worked great for the smaller lettering and logo: