The Cheese-It Thread

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BuiltFromTrash

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So a couple years ago I had a crazy desire to see a cheese-it box fly. Not a little box mind you, but one of those BIG boxes like the ones you get at Costco that hold two bags. So I started building it but I never finished it. A couple weeks ago I started rounding up all the unfinished rockets I had laying around and came across it. I finally finished it... I hope. Here are some pictures of the finished rocket:
DSC_0746 - Copy (2000x3000).jpg This is the rocket from the side. The papered foam fins are on square hardwood dowels.

DSC_0752 (3000x2000).jpg This is the bottom of the rocket. Notice the engine mounts, 2 X 18mm, 1 X 24mm which are meant to be filled with two C6-5|7 and one D12-5. The engine mounts are glued to the box on the inside and outside.

DSC_0758 (3000x2000).jpg This is the interior, the walls of the box are connected to the center tube by 1/4 X 1/16 in balsa sticks and is very rigid. The Kevlar leader is looped around the center tube and is not glued in place.

DSC_0762 (2000x3000).jpg This is the layout of the recovery system, and because the rocket is quite heavy, there are two 18 in. parachutes. Starting at the leader line you will notice the two 1/4 in. by 18 in. shock cords, next to them and connected to the leader line is a 'envelope' to hold and protect the parachutes. Connected at the other end of the shock cords is the nose cone (HA! Not really..), and two 36 in. Kevlar lines which are connected to the parachutes by a swivel.

I did a couple test swings. Unfortunately, it is stable ONLY in the plane 90 degrees from the plane of the fins about the center-line. In building it I made as sure that it would be stable as I could make it, hence the fins on dowels. But the fins are mounted on the corners and to arrange them so that there would be one on each side would make it look bad, not to mention how much space it take up. I decided to put the fins on the way they are not thinking that it could have potentially dire consequences later.

My questions are as follows:
Will it fly?
Or will it prove itself unstable and tear itself apart?

(This post was not just to ask for help, I will be posting pictures of the flight(s) when it flys.:))
 
I'm not going to weigh in on thee questions posed, however to prevent a shred, I'd use some super thin CA to reinforce the leading and trailing edges of the box. Another option would be to glue in reinforcements along the LE and TE of the box.

I want to see a video of this if it goes up.

Now, where did I set that dip?
 
I was thinking it might come apart if it started spinning head over heels, never even thought that it could do it in stable flight. The cardboard is pretty thick though, I don't think it would shred per se, especially since this would be a low and slow flight.
 
My questions are as follows:
Will it fly?
Or will it prove itself unstable and tear itself apart?

Just a guess based on my own scratch build cup rocket experience, but I''m thinking it'll do cheesy power loops. :wink:

I'd add some nose weight, add some flare or something to the bottom of the box and bigger motor. Again, just a guess, but the big flat top surface is a lot of drag (moving the CP forward) and the fins may not be able to compensate and can even bring the CG back. Still, these types of builds are for fun, so usually you get two boxes...one to see funny/cheesy stuff and the next to actually try to make it fly reasonably straight up. YOLO! :grin:
 
I think it would be stable if there was a fin on each side, but there are two fins on two sides making it stable only when swung with the line on that side. It is heavy already, I do not think adding nose weight would work. Hmm.. Did a quick test in OR with a basic rocket, two fins 90 degrees from each other could make for a stable rocket.:y: In the test the CP only moved about a caliber of course making it unstable, but still in the realm of possibility.
 
Having built a "box finned" rocket (many really) I had great success when the motor was more forward than your design. Never built one like yours, but I have to agree with KenE that there's just not enough forward CG going on. Fiddle Faddle was designed back in the late 70's and it incorporated long strake fins to put the motor forward. This was based on boost glider concepts. Bottom line, if you want to insure a stable flight, get that center tube a lot longer, and rely on the drag to stabilize the flight. Get some nose weight going on also.

I like your "out of the box" thinking.....so-to-speak. Here's a snap of my boxed fin concept. Won a designers contest, back in the day. This is the bigger one.

DSCF2025.JPG
 
Well its looking like I'm going to have to change the design one way or another. I really do not want to go with more nose weight as the rocket weighs 12 1/8oz loaded. Based on the swing tests I think if I add four more fins, two on each side that doesn't have any, it should be stable. I'll have to upload a picture of the CG of the rocket. Neat rocket, feel like I have seen a kit like this somewhere, like fliskits.
 
Well its looking like I'm going to have to change the design one way or another. I really do not want to go with more nose weight as the rocket weighs 12 1/8oz loaded. Based on the swing tests I think if I add four more fins, two on each side that doesn't have any, it should be stable. I'll have to upload a picture of the CG of the rocket. Neat rocket, feel like I have seen a kit like this somewhere, like fliskits.

How about adding flaps flared out 30-45 degrees to the bottom? You can even make the longer side flaps shorter to even things out and it should move the CG forward and CP back. Only issue may be too much drag; however it'll look like the box is open and still look like a box. :)

Or just try and fly - yolo! :grin:

BTW - Love the internal bracing structure...looks great!
 
Sniff.. Sniff.. I smell a rat, err, coyote!:y:

Think I'm just going to add 4 more fins and hope this thing straight.:facepalm:

WileECoyote should wear a YOLO shirt with all the crazy things he does. lol

Have you considered just moving the current fins 30-45 degrees so they come out from the corners rather than in-line with the sides? Some unstable rockets use add-on fins this way for stability (ex. Estes R2D2).
 
Here's an idea (too late for this version, but maybe worth trying). Instead of installing a full length body tube (which puts the motor at the very bottom of the rocket) you build one with a short body tube that is mounted up inside the box with only enough room for the motor, the thrust ring, some wadding and the parachute. This way it's dragging the rocket up, rather than pushing it.
 
I really do not want to go with more nose weight as the rocket weighs 12 1/8oz loaded. Based on the swing tests I think if I add four more fins, two on each side that doesn't have any, it should be stable. I'll have to upload a picture of the CG of the rocket.
All right, here is the photo:
DSC_0005 (3000x2000).jpg
As you can see the CG is about ~3 in. from the bottom.

Have you considered just moving the current fins 30-45 degrees so they come out from the corners rather than in-line with the sides?
Now there is a good idea! I could cut the existing fins off, then re-glue them on at a 45 degree angle! I never would've thought about doing that, problem solved.
 
Sounds familiar ;)

Yeah... It never occurred to me that I could cut it off and re-glue it. Seeing as I wanted to save space, I only briefly thought of doing that. Now that I can see how strong they are now, I don't think that would be a problem.

Phew, working on two threads is tough!:blush:
 
Come to think of it, I don't see any reason why didn't do this earlier, other than saving space, but I am going to stop beating that dead cat now.:)
 
This is sort of some "inside the box" thinking.

can sort of do this as a modified saucer
Put two D-12 motor mounts up front, right against the front end of your box but inside the box, centered. This will keep your CG forward. Plug the forward ends of the motor mounts, they will eject the engines out the back. Need to cut some air flow holes around the engines in the front to allow some air to go through to avoid Krushnic effect.
Put BT 50 tubes next to these, running the length of your box. Put BT 5 mounts at the tail end of each, these will use A3-4t engines, function is simply to eject your chutes forward. So the BT 50s in front of these will hold your wadding and chutes.
You are flying 4 engine cluster. The d12-3s forward will keep your CG WAAAAAAY forward, which is good. Your A4-3Ts won't mess your CG too much.

All engines light. The D12-3s burn out first and eject the engines out the back. About a second later your A4-3Ts eject your laundry out the front.

Again you will need some holes in your nose plate to allow some air flow around your D12s up front.
 
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Bump for the contest. I will try to continue the work in these wintry months. Got some ideas for bettering the recovery system.

Woody, I got you covered. Videoing my rocketry stuff is a growing obsession of mine. :D
 
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