Here's another design that might be worth playing around with.

[Senior Space Cadet]

 

[dr wogz]

Love the 'out of the ordinary'!!

And I do get a kick out of what you are producing thru OR!!

Start thinking "R/C airplane or boat" and that can open a world of possibilities!

Start with a traditional minimum dia tube & motor mount. then, add formers at various points up the tube. these formers can be a triangle, square, hex or even octo-deca-hedron! at each point / vertex of these 'formers' you will have notch, and you will run a stringer the length of the rocket. a stick of 1/8" square balsa. You should then have a stick & former frame on a tube base. Then skin the stringers & formers with thin balsa sheet, cardboard, or to get fancy, 1/32" ply!

The nosecone.. right. Easy! a round balsa 'plug' that fits the BT. And a balsa block glued on top of that. Then just sand to match the body!

Of course, this will lead you to using a proper CAD program, as I seriously doubt OR can do "formers & stringers"


You initial example should fit this quite well. a tube & MMT, and a series of progressively smaller 'centering rings' up the outside (like the formers) then just roll a cone (frustum actually) of paper and affix in place. (you can download 'cone patter' apps that'll do a proper "flat' of a cone or frustum..


Next little tid-bit for your noodle: Cone as a fin; a cone stabilized rocket!

https://www.rocketryforum.com/threa...gn-ram-air-intake-stabilization.131572/page-6post 179!

 

[Senior Space Cadet]

I was thinking of rolling something like posterboard into a cone shape, with some sort of balsa framework for support.
For the nosecone, I was thinking I could leave the main cone short, so it doesn't come all the way to a point, put a short section of cone inside the main cone, also not coming to a point, and then a small cone would act as a cap. I'm going to need to brush up on my geometry.
If I wanted to go the Mylar over a frame route, washer shaped balsa frames with notches around the outside, for thin strips of balsa, might be good.
The simpler I make it the more likely it's going to get built. On the other hand, winter is coming and I'm going to be stuck indoors.

 

[Funkworks]

I like it because it looks heavy in the back but you can probably move CG forward without it being obvious. Rear-ejection or normal?

 

[Jay Rairigh]

So you've taken 3 fins and a nose cone quite literally!

 

[dhbarr]

If you keep it going you could easily end up with a caltrop.

 

[cwbullet]

View attachment 433316

If you share the Open rocket fIle, I will test it out this week. I might 3d Print a test bed.

 

[Senior Space Cadet]

If you share the Open rocket fIle, I will test it out this week. I might 3d Print a test bed.

I didn't make a file, only a screen shot.
I'm working on a slightly different design. See next post.

 

[Senior Space Cadet]

The purely conical shape is looking like a tough nut to crack. I've come up with a similar design that uses parts that are not only in existence, I currently have them on hand. Here is a screen shot. I'll work up a more finished file today or tomorrow. I could go with a shorter transition on the back, but this one might be more practical.

 

[GlenP]

I like the boat tail on that one.

Kind of similar to the Pemberton 29mm powered "3FNC"

https://www.pembertontechnologies.com/3fnc/

 

[Senior Space Cadet]

I know this doesn't quite have the same flavor as the original design, but taking into consideration my current skill set and other practical matters, here is a completely doable, functional design. And it's nearly a finished design, not just a rough draft for a screen shot. About the only thing missing is centering rings.

 

[Senior Space Cadet]

I haven't given up on the original design, but I've pretty much decided that I'd have to make my own nosecone.
I see two ways of doing it and making it look right.
Buy a lathe and drill press and make it out of balsa. Probably won't happen.
Or, make it out of fiberglass. In order to make it look really nice, this probably involves make a female mold. I'll probably have to make a male mold first and I was thinking of using Styrofoam cones. I'll have to start looking at older posts on making fiberglass nose cones.
https://www.amazon.com/Happyyami-St...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

[Alan R]

I haven't given up on the original design, but I've pretty much decided that I'd have to make my own nosecone.
I see two ways of doing it and making it look right.

3D print your nose cone. I do it all the time. Takes a few hours. And cheap. I take it you don't have a printer.
Not overly difficult to design/create the .stl file (3d print) from your .ork file
If you have an .stl file, you can have it printed from a commercial service for about $25 I think. Or easy enough to find someone here to do it for you. Me included.

 

[Alan R]

Also ... it looks to me like you have very little room in there for a streamer/chute. That one piece of body tube looks to be only a couple inches long.
stuffing the recovery into the nc won't work....
2 piece NC?

 

[Senior Space Cadet]

Also ... it looks to me like you have very little room in there for a streamer/chute. That one piece of body tube looks to be only a couple inches long.
stuffing the recovery into the nc won't work....
2 piece NC?

I did intend to stuff the chute and shock chord in the nose cone. Why won't that work?
I'm going to glue a screw-eye in the tip of the nosecone. Plenty of room in there for the chute and shock-chord. It's 41.6 mm in diameter. I'll use my usual method of attaching the shock chord to the motor mount.

 

[Senior Space Cadet]

3D print your nose cone. I do it all the time. Takes a few hours. And cheap. I take it you don't have a printer.
Not overly difficult to design/create the .stl file (3d print) from your .ork file
If you have an .stl file, you can have it printed from a commercial service for about $25 I think. Or easy enough to find someone here to do it for you. Me included.

No, I don't have a 3D printer, but I will look into the option of having someone else do it. I'm pretty tech challenged, but maybe I can get it all figured out. Probably for a future build. I'm pretty far along on this one.

 

[Senior Space Cadet]

The revised design is coming together nicely. I just made a fin template and everything is fitting together.
If I put my nose to the grindstone, I could have it ready for paint in a day or two.
The nose is ogive and the boat tail I have is cone shaped. An ogive tailcone would look nicer.
Before I glue everything together, I could wait till my shipment from Balsa Machining Service comes. There might be something in there that will look better, or, since I've already got this one pretty well sorted out, I could just build another rocket entirely.

 

[BABAR]

I did intend to stuff the chute and shock chord in the nose cone. Why won't that work?
I'm going to glue a screw-eye in the tip of the nosecone. Plenty of room in there for the chute and shock-chord. It's 41.6 mm in diameter.

Stuffing the nose cone WILL WORK, but will require some ingenuity. Definitely need a hollow plastic cone.

Run a stiffer tube (aka “chimney”) one size down from the motor tube, from the front of the motor tube (note this will also function as your motor block.) Put a piece of rolled up aluminum can, about the length of the can and just a bit greater than the inside diameter of the stuffer tube, glued to the inside of th stuffer just in front of the motor (this will handle the concentrated heat of the ejection in the slightly constricted space. Yes, aluminum IS flammable, but that is mainly POWDERED aluminum and your thin aluminum tube here will handle it just find, while the unprotected paper tube will scorch.) Run the chimney tube (only the rear end needs the aluminum) as far as it will geometrically go into the nose cone. Spread some JB weld or other heat proof adhesive on the inside tip of the nose cone to protect the plastic from the concentrated blast.

Centering rings can easily be custom made with foam board. You will need two in your boat tail around the motor mount, one around the forward end of the chimney, say an inch back from the forward-most tip. (Which I’ll likely be about 1-2 inches from the actual inside tip.). Shock cord attachment is to the short round tube just forward of the boat tail. Nose cone shoulder fits into (and is Glued into) the short tube segment forward to the boat-tail. You may be able to wrap this around the nose cone shoulder before you glue the nose cone in, that would be pretty secure.

There is a coupler extending forward from the boat tail into the short tubular segment, it is GLUED to the boat tail, it is NOT GLUED TO THE SHORT TUBE SEGMENT. This is your separation point.

Wadding not technically required, but given the forward ring won’t seal (because of the divergent internal walls of the nose cone) a loose wadding burrito role of the chute would be wise.

When ejection fires, it is ducted through the chimney. The aluminum protects the first few cm of the chimney, as it will be VERY hot due to the confined space. The gas blows the nose cone and attached tube segment off the rear assembly (or, per Newton’s law, kicks the rear assembly back from the cone, tomAato, tomAHTo.). The rear assembly consists of the motor and motor mount, the chimney, the boat tail-fin can, the chute and shroud lines. The rear assembly is connected with the cone via the shock cord. Because the forward centering ring is SMALLER in diameter since it is inside the sloping nose cone, it shouldn’t hang up on the shock cord.

 

[Alan R]

I did intend to stuff the chute and shock chord in the nose cone. Why won't that work?

Because if your chute is in the NC, the ejection charge is going to pack it tighter into the NC. You need open space behind the laundry.

 

[Alan R]

Can you post your .ORK file ? I might give this one a try with balsa fins and then print the NC

 

[Senior Space Cadet]

I was a little concerned about burning up the chute, even though there is probably more volume, ahead of the ejection charge, than with a minimum diameter rocket, especially a short one. This is a big nose cone and an 18mm motor. My plan was to cover the chute with NOMEX. If you think burning up the tube is a danger, there is high temperature paint (stove paint) that I could spray the inside of the tubes with.
I haven't worked out the geometry, and not sure I could, but you have a 41.6mm (base) X 8.5 inch plastic ogive nose cone, with about a 2cm shoulder vs., say, 24mm X 8 inches of space ahead of my typical BT-50 build. Doesn't seem to me the volume is that much of an issue. I'll let you guys with the big brains do the calculations. For the last forty years, I've mostly had to work out multiples of a dozen (rolls, Danish, donuts) and how many pans of 15 or 18 I need to bake.
I'm more concerned with melting the nosecone. I might have to spray that too.

 

[Senior Space Cadet]

Another concern is gluing the fins on. Balsa fins, plastic tailcone. I'm going to use super glue to hold them in place initially, but I can't use yellow/white glue to make fillets. I guess the obvious solution is thickened epoxy. I'm not sure I still have any thickening agents left over from my boat build. I might have to order something before I can proceed.
Any other ideas besides thickened epoxy?

 

[Senior Space Cadet]

Here is the file, I hope. There are small parts missing, since I wasn't sure what was going to fit. I'm not very anal about my design process.
I'm also changing the way I mount the motor. I have 18mm body tubes and several sizes of centering rings. Instead of putting an 18mm motor mount inside a 24mm body tube, I'm going to just use a longer 18mm tube. I'm also planning on using screw on motor retainers. I haven't incorporated that into the design yet.

 

[dr wogz]

Another concern is gluing the fins on. Balsa fins, plastic tailcone. I'm going to use super glue to hold them in place initially, but I can't use yellow/white glue to make fillets. I guess the obvious solution is thickened epoxy. I'm not sure I still have any thickening agents left over from my boat build. I might have to order something before I can proceed.
Any other ideas besides thickened epoxy?

epoxy thickeners:
Balsa dust
Baby powder

some / most epoxies don't stick too well to plastics. Roughen the plastic up where you plan to put your fillets, so it has something to 'bite into'.. You might try a poly-urethane glue (gorilla glue) and sand / shape it once it foams up & cures..

Look up 'nomex blankets' (or just 'blanket') we use them in HPR for exactly that reason: to protect the chute.

Screw-on retainers add weight..

 

[Alan R]

i hacked out a 2 pc NC for 3D print.
created the long nose cone and then split it, added shoulders.
It has a crossbar on the nose for attachments. This would give you about 3" of space for a chute.
Nothing printed/tested. Made to fit your BT dimensions. (4.19/3.87cm). Tip might need supports because of the overhang. Base is upside down for printing.

 

[Senior Space Cadet]

Here's a photo of where I'm at right now.
Currently, if I stuck a D size motor in it, I think stability would be borderline.
I haven't glued the fins on yet. If I were to go to four, which I'm reluctant to do, there would be no question about stability.

 

[Senior Space Cadet]

FYI: I got the nosecone and tailcone from this Estes nosecone assortment.
https://estesrockets.com/product/003165-nc-60-long-nose-cone-asst-3-pk/

 

[jqavins]

Because if your chute is in the NC, the ejection charge is going to pack it tighter into the NC. You need open space behind the laundry.

There are successful designs with the laundry stuffed into the nose cone. It's not ideal. The nose cone needs to have some substantial mass. (From what you have said about stability, some nose weight may well be in order anyway.) As it and the rest of the rocket are moving apart, each with a decent amount of inertia, they pull the shock cord out straight with the parachute in the middle.

There's no argument that pushing the parachute out is better than pulling it out. Pulling it out is less reliable, and not a good idea when there's a push solution available. But don't let anyone tell you it can't be done. I've done it, as have many others.

 

[GlenP]

Kind of depends where on the shock cord you attach the chute, just make sure it is somewhere closer to the middle instead of all the way at the nose cone end.

 

[Senior Space Cadet]

Kind of depends where on the shock cord you attach the chute, just make sure it is somewhere closer to the middle instead of all the way at the nose cone end.

That's where it's at. I guess we'll see. As long as there is separation, and the rocket lands on grass, it'll probably survive.
If it doesn't, it's not the end of the world. It's not like I've crashed a real rocket with astronauts on board. I won't be happy, but far worse things have happened to me.