Bare Minimum: M2245 to 50,000 feet

[Neutronium95]

Say hello to Bare Minimum. This is a 75mm submin rocket intended to fly on a CTI M2245 to around 50,000 feet and exceed the current Tripoli M record. According to RASAero, it'll hit Mach 3.6, and will spend almost 5 seconds above Mach 2.5.



I originally intended to fly this at BALLS this year, but life happened, and the test rocket that I wanted to fly in April, ended up flying (mostly) successfully at BALLS this year.

In general, my philosophy with this design has been to optimize the design in areas that won't hurt the chances of flight success. I have a quite small volume for electronics and recovery, which will be challenging to work in, but after seeing numerous nosecone and airframe failures on other extreme performance flights, my nosecone and coupler are going to be a good bit thicker than might be strictly necessary. Similarly, I won't be going with the absolute minimum fin area. This rocket is going to be very stable. I'm very much a novice at dynamic stability analysis, but I'm hopeful that a large static margin will be enough to prevent the issues that have caused problems on previous extreme performance flights.

The nosecone will be made out of Soller Composites fiberglass sleeves, and Fibreglast System 3000 resin. It will fit onto a contoured coupler attached to the top of the motor that houses the electronics, just like on the test rocket. Recovery will be identical to my previous 75mm min diameter rocket, with cable cutter dual deploy, and a 36" BAMA parachute. Electronics will probably be a Blue Raven and EasyMini for deployment, along with a Featherweight GPS and RDF beacon for tracking.

I'm still not entirely certain how I want to build the fin can. The easy way would be to buy or lay up a tube, cut fins from carbon plate, and bond them on, like on the pathfinder rocket. The hard way would be to emulate the M3R fin can, and build up a fin profile with layers of prepreg carbon fiber. I'm attracted to the second, because it allows me to taper the fin thickness, and maintain a constant airfoil profile across the fin, but it'll require a lot more work, and would be something new for me. Either way, I'm going to have an Aluminum leading edge manufactured for the tube, to prevent the failure that I saw on the test rocket. Mach 3 is hard, and Mach 3.5 is even scarier. I also have a few different ideas about thermal protection for the fin can, but we'll come to those later.

I probably won't start on the fin can first. I'd like to build the entire nose section, and have a known mass for it before I settle on the final fin size.

The final concern I have is whether or not to attempt the Tripoli M record. If I go for the Tripoli record, I'll have to wait for a launch at Black Rock, whereas if I don't, I could just go to the next FAR launch date once it's built. Either way that final decision is a few months down the road.

This rocket is inspired by many high performance builds I've seen on here. Particularly Bare Necessities and the other N5800 record attempt builds that I followed as a teenager. I just hope it survives a bit better than them.

 

[Hobie1dog]

pictures as you make progress on it...WOW, just WOW.

 

[pugachu]

Do you have your reload yet? The M2245 is hard to find.

 

[Neutronium95]

Do you have your reload yet? The M2245 is hard to find.

I got it in January.

 

[3stoogesrocketry]

Oh geeze another Bare Necessity.... oh my bad lol ( poke at someone else lol ). You should look into the Loki M3400 blue. Slightly less total impulse but should get you the speed you need if you can get the optimal mass figured out.

 

[Neutronium95]

Oh geeze another Bare Necessity.... oh my bad lol ( poke at someone else lol ). You should look into the Loki M3400 blue. Slightly less total impulse but should get you the speed you need if you can get the optimal mass figured out.

I'll consider it for a possible flight after the M2245. It would certainly be a wild ride. Is the Loki 76/8000 the same as the AMW 75/7600? I have one of the latter on hand, but probably wouldn't shell out the cash for even more 75mm hardware of about the same length.

Speaking of crazy motors, before I secured a motor case, I considered making a carbon case for the M2245, a la Don't Debate This 2. I might still do something similar down the line, and reuse the nosecone and recovery parts on an even crazier flight with a composite cased motor with fins bonded directly to the motor case.


Edit: The name is very much an omage to Bare Necessities. I followed that thread daily when I was a teenager, and even though it ended poorly, it helped lay the seeds of my love of flying things high and fast. I just hope that I learned the right lessons from that project.

 

[3stoogesrocketry]

I'll consider it for a possible flight after the M2245. It would certainly be a wild ride. Is the Loki 76/8000 the same as the AMW 75/7600? I have one of the latter on hand, but probably wouldn't shell out the cash for even more 75mm hardware of about the same length.

Speaking of crazy motors, before I secured a motor case, I considered making a carbon case for the M2245, a la Don't Debate This 2. I might still do something similar down the line, and reuse the nosecone and recovery parts on an even crazier flight with a composite cased motor with fins bonded directly to the motor case.


Edit: The name is very much an omage to Bare Necessities. I followed that thread daily when I was a teenager, and even though it ended poorly, it helped lay the seeds of my love of flying things high and fast. I just hope that I learned the right lessons from that project.

Yes, same hardware as the 75/7600. I hope you the best of luck. Ask all the questions you need

 

[Cameron Anderson]

Oh geeze another Bare Necessity.... oh my bad lol ( poke at someone else lol ). You should look into the Loki M3400 blue. Slightly less total impulse but should get you the speed you need if you can get the optimal mass figured out.

 

[Neutronium95]

I've been playing around with simulations, trying out different surface finishes and launch sites in RASAero. I'm leaning towards just assuming the altitude for Rough Camouflage Paint for a realistic estimate, and Smooth Paint for how high a waiver I'll need, as an absolute best case scenario for performance. I also updated the sim with the actual nozzle exit diameter (1.95" if you were wondering) which resulted in a modest increase in simulated altitudes over previous iterations.

Keep in mind that these are very preliminary sim results. There's a lot that's not settled with this design yet, especially in the fin can. These sims reflect the fin can I want to build, representing a composite fin can with fins that taper in thickness from root to tip and a good airfoil. If that ends up being too much trouble, I might pivot to a less optimized design with a more normal fin can. These sims are just to put a rough bounding box on potential altitudes, and to help plan out launch site selection.

Launch site	Rough Camouflage Paint	Smooth Paint
FAR (2000 ft)	47,983 ft	55,889 ft
Black Rock (4000 ft)	54,587 ft	63,486 ft
Alamosa (7600 ft)	69,842 ft	80,298 ft

Ultimately, unless NSL West has a much higher waiver next year, this won't fly there. Although if it did have a 100k waiver, I think that this design could improve on the existing M record by a major amount.

Black Rock would be the best bet, but I'd prefer to launch this before BALLS. I've heard that there might be some other attempts at the record there next year, and I'd like to get my name on the board before then. I also have a few projects lined up for that launch as well, and would like to get this out of the way before then. Mudrock is an option I'm considering, but I'd prefer to not go to too many launches that are a long trip next year, and Mudrock would take me up to 3 for sure (NSL West and BALLS being the other two). Besides that factor, it's pretty much perfect. I'd prefer a launch a bit earlier in the year, but I'll take what I can get.

Then comes FAR, which is by far the most practical, with two launches a month and relatively close to me. It would also render the flight ineligible for a Tripoli Record, and is within a margin of error to not break the current record. I might go with this option if I just get fed up with the project and just decide to launch once it's ready to fly.

While my main goal with this project has been to break the current M record (45,554ft), it seems like breaking 50,000 feet might be within the realm of possibility, especially if I launch at Black Rock. That's why I'm tentatively planning on flying this at Mudrock, but that is far from set in stone.

In other news, I was playing around with the sim and found that a longer nosecone actually helps increase altitude a decent amount. I've learned my lesson from previous high performance rockets that trying to pack a big enough parachute into a tiny volume is a massive pain. A longer nosecone will make that a lot easier, which makes it a no brainer. The longer nosecone makes things a bit heavier, but I'm still a bit below optimum mass. As it is, this rocket is close enough to optimal mass that it's not very sensitive to changes in mass; going up to optimum mass results in a gain on the order of 0.1% more altitude. Not worth worrying about.

Finally, I ran some sims on the CTI tailcone. Earlier in the design process, I tried to figure out how to nicely integrate a tailcone into the design, and couldn't come up with anything that wouldn't count as modifying the motor. I've always believed that the CTI 75mm tailcone tapered down far too abruptly to provide any real benefit, and that the air stream would just separate, and that belief has been borne out by the sim, with it showing a very minor performance hit. Ultimately it's not worth using the 75mm CTI tailcone for a performance benefit.

Finally, just to see how high I could crank the altitude to I ran a sim with 3 fins, Smooth Paint, at Alamosa elevation and got an altitude of 91,421 ft. This is absolutely unrealistic for many reasons, not least of which is the reduced stability. It's within the margin for RASAero to not throw an error, but I'm being extra conservative with stability on this flight.

The next step for this design and build process will be to play around with some Soller sleeves for the nosecone. I want to characterize just how thick the sleeves are at various different diameters, so that I can compensate for that when designing the male mold plug. I also need to get around to designing and building a composite curing oven. The high temp laminating resins I'm planning on using for this build require a post cure to reach their maximum temperature resistance.

 

[Neutronium95]

I also want to share my annoyance at the fact that the Australian Rocketry Forum is gone. The build thread for the current M record holder is great, and I really wish I could share it here for people to see. Nic Lottering built one hell of a rocket, and while I think I've found a few places to improve upon his work, exceeding his record is by no means a sure thing. Hell, just having a fully successful flight isn't guaranteed. This will be my first flight in a truly extreme flight environment. I'm going to design and build this to the best of my knowledge and capability, but that very well might not be enough.

 

[Neutronium95]

Fin Frustrations​

The biggest obstacle on this build, and the main reason why it didn't fly at BALLS this year is my indecision with the fin construction. I'm still undecided, but my thoughts have congealed around a few different possibilities. This post will go over the general designs I'm considering, and then get into my thoughts on some other considerations, like aerodynamic heating.

The first, and most simple construction method is to simply cut the fins out of carbon fiber plate, bevel them and bond them to a fin can with large fillets made out of a good structural resin. I'm planning on doing some tests to figure out what exact resin and plate to use, but this is a method that I'm familiar and comfortable with, and if I choose the correct materials I'm confident that it will survive the flight.

Flat fins are cool, but what if we go with something that's more aerodynamically efficient? And what if we make the fin can out of prepreg a la M3R? That general thought process lead me to this idea. An airfoiled fin that tapers from root to tip is the holy grail of fin design. The problem is how the hell do you make it.

I ran some sims in RASAero, and the tapered airfoiled fins do provide a large drag benefit, so I would really like to use them. It's not just a vanity thing I swear.

My initial idea was to copy M3R and build up a fin can from layers of prepreg. Unfortunately, a lot of the more easily available prepregs don't have great high temperature performance (250F+) and I'm nervous about making the leading edge out of anything I lay up. I'd really like to find some way to make this a method I'm confident in since it's really cool, I'm just not certain about it.

The simplest solution would be to have someone else, either a friend or a company machine the fins out of a solid plate of carbon fiber. This allows me to use a plate of high temperature material, and makes things simple. The downside is that this could get expensive fast, and I want to build the whole rocket myself instead of contracting it out.

Some other options I've considered include:

• A hybrid approach like @watheyak used on his L2050 build, with a machined core that provides the heat resistant leading edges and prepreg reinforcement.
• Building up the fins like M3R, but use a more traditional wet layup with a high temp resin.
• Laying up prepreg over a CNC cut foam core, somewhat like this fin can that Tu Wein made a few years ago.
• Some people I know have had some success with using the methods in this video to make compression molded fins. Maybe throwing some actual fabric on the outside faces would make it stiffer. I am not very confident in this method though.

One of the big challenges with the composite fins is keeping the fins from being degraded by aerodynamic heating.

One option, used by Nic Lottering and Kip Daugirdas is to put metal end caps over the fin leading edges. I'm not sure exactly what thickness of material they've used, but I think that it would likely require tools that I don't have. I might be able to get away with a thinner metal foil, but am not sure.

A second option is to use a leading edge made out of high temp composites, like what @watheyak has used on several builds. I'm leaning towards just making the fins out of high temp Dragonplate if I go down this route. Unfortunately it's really expensive, and would limit me to either flat plate fins or machining the whole fin on a CNC mill.

Finally I'm considering just making the fins with a high temp resin, like Fibreglast System 3000, or a high temp prepreg and just sending it. A coating of Cerakote Glacier Black should do a lot to keep the heat from getting the fin material itself. Between the two of those that might be enough to make a fin can that can survive a brief jaunt to Mach 3.6 unscathed. It would also lead to commonality with the nosecone, which will be a wet layup with System 3000 and a high temp coating. Fortunately for that I can just get an Aluminum tip made to handle the brunt of the heating.

The really frustrating part with designing for the heating is figuring out just how hot things are going to get. It's quite easy to plug and chug an altitude and mach number to get a stagnation temperature that will scare the crap out of you. A bit more research says that what you actually want is the recovery temperature, which is a bit lower. But that only tells you how hot the air is. I'm at a loss trying to figure out how hot that will actually make the fins. I dropped out of college before I got anywhere near heat transfer, so I'll be working with my dad to try to characterize this a bit better. If anyone has any good resources on the subject, I'd love to see them.

Finally, after all this hemming and hawing about how to make a composite fin can is the nuclear option. Metal 3D printing services like CraftCloud are surprisingly affordable, and I could probably get the entire fin can printed out of Aluminum for about the same price as getting everything I need to make a fin can out of prepreg. And I wouldn't have any concerns about strength or temperature resistance. The only objection that I can raise with this is that I'm not building the fin can. This might be a bit vain, but I really want to build the whole rocket myself, and having someone else make such a critical part just rubs me the wrong way. But on pretty much any other criteria I can't find a problem with it.

I hope that this wall of text that encapsulates a year of my brain wandering about fins wasn't too incomprehensible. I'd love to hear what different forum members think of the various different fin construction methods I've considered. I haven't ruled anything out yet, but do have a few things I'm leaning towards.

 

[Neutronium95]

To show off what I'm talking about when I say tapered airfoiled fin, here are some screenshots of a rough CAD model I threw together. I just used a pair of circular arcs to form the airfoil for this. The precise fin profile is very likely to change before I build it.

Here's the side view, showing the relatively standard swept fin shape.

The front view shows the taper from root to tip. In this case 3/16" to 1/16", although this is still very much subject to change. I've played around with a few different thicknesses and haven't come to a firm decision yet.


Then there's the bottom view, showing the basic airfoil profile.


I also printed out a fin to play around with and get a feel for. It's one thing to talk about tapers and airfoils, it's another thing entirely to hold it in your hands.

 

[boatgeek]

Fin Frustrations​

The biggest obstacle on this build, and the main reason why it didn't fly at BALLS this year is my indecision with the fin construction. I'm still undecided, but my thoughts have congealed around a few different possibilities. This post will go over the general designs I'm considering, and then get into my thoughts on some other considerations, like aerodynamic heating.

The first, and most simple construction method is to simply cut the fins out of carbon fiber plate, bevel them and bond them to a fin can with large fillets made out of a good structural resin. I'm planning on doing some tests to figure out what exact resin and plate to use, but this is a method that I'm familiar and comfortable with, and if I choose the correct materials I'm confident that it will survive the flight.

Flat fins are cool, but what if we go with something that's more aerodynamically efficient? And what if we make the fin can out of prepreg a la M3R? That general thought process lead me to this idea. An airfoiled fin that tapers from root to tip is the holy grail of fin design. The problem is how the hell do you make it.

I ran some sims in RASAero, and the tapered airfoiled fins do provide a large drag benefit, so I would really like to use them. It's not just a vanity thing I swear.

My initial idea was to copy M3R and build up a fin can from layers of prepreg. Unfortunately, a lot of the more easily available prepregs don't have great high temperature performance (250F+) and I'm nervous about making the leading edge out of anything I lay up. I'd really like to find some way to make this a method I'm confident in since it's really cool, I'm just not certain about it.

The simplest solution would be to have someone else, either a friend or a company machine the fins out of a solid plate of carbon fiber. This allows me to use a plate of high temperature material, and makes things simple. The downside is that this could get expensive fast, and I want to build the whole rocket myself instead of contracting it out.

Some other options I've considered include:

• A hybrid approach like @watheyak used on his L2050 build, with a machined core that provides the heat resistant leading edges and prepreg reinforcement.
• Building up the fins like M3R, but use a more traditional wet layup with a high temp resin.
• Laying up prepreg over a CNC cut foam core, somewhat like this fin can that Tu Wein made a few years ago.
• Some people I know have had some success with using the methods in this video to make compression molded fins. Maybe throwing some actual fabric on the outside faces would make it stiffer. I am not very confident in this method though.

One of the big challenges with the composite fins is keeping the fins from being degraded by aerodynamic heating.

One option, used by Nic Lottering and Kip Daugirdas is to put metal end caps over the fin leading edges. I'm not sure exactly what thickness of material they've used, but I think that it would likely require tools that I don't have. I might be able to get away with a thinner metal foil, but am not sure.

A second option is to use a leading edge made out of high temp composites, like what @watheyak has used on several builds. I'm leaning towards just making the fins out of high temp Dragonplate if I go down this route. Unfortunately it's really expensive, and would limit me to either flat plate fins or machining the whole fin on a CNC mill.

Finally I'm considering just making the fins with a high temp resin, like Fibreglast System 3000, or a high temp prepreg and just sending it. A coating of Cerakote Glacier Black should do a lot to keep the heat from getting the fin material itself. Between the two of those that might be enough to make a fin can that can survive a brief jaunt to Mach 3.6 unscathed. It would also lead to commonality with the nosecone, which will be a wet layup with System 3000 and a high temp coating. Fortunately for that I can just get an Aluminum tip made to handle the brunt of the heating.

The really frustrating part with designing for the heating is figuring out just how hot things are going to get. It's quite easy to plug and chug an altitude and mach number to get a stagnation temperature that will scare the crap out of you. A bit more research says that what you actually want is the recovery temperature, which is a bit lower. But that only tells you how hot the air is. I'm at a loss trying to figure out how hot that will actually make the fins. I dropped out of college before I got anywhere near heat transfer, so I'll be working with my dad to try to characterize this a bit better. If anyone has any good resources on the subject, I'd love to see them.

Finally, after all this hemming and hawing about how to make a composite fin can is the nuclear option. Metal 3D printing services like CraftCloud are surprisingly affordable, and I could probably get the entire fin can printed out of Aluminum for about the same price as getting everything I need to make a fin can out of prepreg. And I wouldn't have any concerns about strength or temperature resistance. The only objection that I can raise with this is that I'm not building the fin can. This might be a bit vain, but I really want to build the whole rocket myself, and having someone else make such a critical part just rubs me the wrong way. But on pretty much any other criteria I can't find a problem with it.

I hope that this wall of text that encapsulates a year of my brain wandering about fins wasn't too incomprehensible. I'd love to hear what different forum members think of the various different fin construction methods I've considered. I haven't ruled anything out yet, but do have a few things I'm leaning towards.

Re: milling an air foiled fin out of a thicker flat plate. I think that if you do that, you’ll have fiber ends/edges exposed all the way down the shapes leading edge of the fin. It would only take the airflow getting under one of those to start pulling the fin layup apart. If you go that route, you might want to add a single layer of layup over the entire fin just to seal all of the cut edges.

Disclaimer: I don’t have personal experience with high Mach flights, I’ve just seen lots of postmortem pictures here.

 

[robopup]

Re: milling an air foiled fin out of a thicker flat plate. I think that if you do that, you’ll have fiber ends/edges exposed all the way down the shapes leading edge of the fin. It would only take the airflow getting under one of those to start pulling the fin layup apart. If you go that route, you might want to add a single layer of layup over the entire fin just to seal all of the cut edges.

Disclaimer: I don’t have personal experience with high Mach flights, I’ve just seen lots of postmortem pictures here.

Similarly, you don't even need aero loads to cause a delam with a stack like this; a bending load can also cause it. In general, that's why a stack which is "reverse wedding cake" where larger plies are on the outside is preferred. Not necessarily saying it will happen here with this fin and loads, but something I wish I saw less regularly.

 

[watheyak]

With my L2050 rocket the fins, while not airfoiled, had a large bevel with layers exposed to the relative wind. One of the lessons that I learned form previous, unsuccessful flights was that the density of the fin material had a large effect on its survivability.

Hence the Garolite or similar that I picked. Of the CF plates I saw, they were not as dense, and made me nervous. Sure, the green Garolite isn't as sexy, but it'll survive.

Also, I feel like Cerakote or other high temperature coatings should not be used to protect the underlying structure. While they may survive and keep the rocket nice and shiny, they aren't an insulator. I'd still use it, as shiny rockets fly higher.

 

[watheyak]

I edited my last post, as I left out an important "not".

Cerakote should not be used to protect the underlying structure.

That's just my hunch nim not an engineer or a thermodynamicist.

 

[Neutronium95]

With my L2050 rocket the fins, while not airfoiled, had a large bevel with layers exposed to the relative wind. One of the lessons that I learned form previous, unsuccessful flights was that the density of the fin material had a large effect on its survivability.

Do you have any experience with phenolic/carbon composites, like the high temp Dragonplate?

I am pretty hopeful that the Glacier Black Cerakote will actually provide a good insulating layer, since it seems to be designed for that purpose, but I need to actually get around to doing the heat transfer math to prove that to myself.

 

[watheyak]

It wasn't Dragon Plate. When I get home Tuesday I'll find the sample. It's got a sticker that says who it came from. It's pretty crappy.

 

[watheyak]

What leading edge radius are you using on your airfoiled fin? I'm using .06" on the one I'm working on.

 

[Neutronium95]

What leading edge radius are you using on your airfoiled fin? I'm using .06" on the one I'm working on.

I have not decided yet. That'll be a function of whatever fin construction and leading edge protection I settle on.

The printed one would have a radius of 0.4mm, since that's the nozzle size on my printer.

 

[OverTheTop]

I did some fins on my 1/2 scale Nike Apache that used a 3.2mm G10 core covered with 0.5mm CF plates. The core was routed in an isogrid structure, so really light. Leading edges had titanium strips protecting the edge of the composite structure. They were glued in place with JB Weld.

I could show you some details but it is on the Australian Rocketry forum.

It was flown on an O3400 to M2020. Sustainer reached M2.14 after a 15.5-second staging gap. Flight up was nominal but I lost telemetry at apogee, so I have not got the sustainer back.

So I wasn't up near M3.6, but you can consider the method.

Note that the stagnation temperature applies to a normal airflow (at right angles to the leading edge). If you resolve your velocity into two orthogonal vectors, parallel with and normal to the leading edge, you will see that the LE sees a lower velocity than the freestream speed. In fact, if you have sufficient sweepback, the LE can see subsonic velocities even when the vehicle is supersonic. For high-speed flights sweepback is your friend. If you keep it within the "Mach cone" then the normal velocity is subsonic!

https://www.grc.nasa.gov/www/k-12/airplane/machang.html

 

[charrington]

So with blue variable I did not use tip to tip and simply went with high modulus CF plate from mcmaster. It did hit its target altitude and up until GPS was lost during apogee deployment, it seemed like a normal flight profile. Im assuming the fins held up fine but cant confirm obviously. Speed should have been in the low mach 3. 1/16th inch fins with a very aggressive bevel on leading edge. I need to update my post but think mirrored knife edge wet sanded up to 3k grit. my flight was under conditions much less longer than you would be tho.

 

[Neutronium95]

I've seen several people I know choose 3D printed aluminum for fin cans on high performance projects. I've been aware that it is probably the best all around method of making a fin can available to me, but I've been avoiding it because I want to build the fin can myself. Tonight, I decided to throw together a quick CAD model of my planned fin can, and get a quote for it. It comes out to around $300 printed in Aluminum. That's a lot less than I'd need to spend if I went and acquired the prepreg and other supplies to make a fin can the way I want to. It's the most cost effective option, and it will save me a ton of stress about aerodynamic heating. I can probably optimize the design further with it as well, maybe by hollowing out the fins and fillets a bit, like on the printed fin cans that Tu Wein use on their rockets.



This is far from the finished design, but it's close enough to get a preliminary quote.

Right now from where I'm standing, the only reason to pursue a composite fin can is to be able to say that I made every part of the rocket myself. In all other aspects the aluminum fin can will probably be better. I need to do some more work on figuring out exactly what it'll take to make a prepreg fin can, and if there are any other options to consider.

While I chase my tail in endless circles about the fin can, I'm going to try to make actual progress on the nosecone soon. I'm planning on testing out the 3" Soller sleeves at several different diameters, so that I can characterize exactly how thick they'll be at various points on the nosecone, which will allow me to design a male plug that will lead to a perfect Von Karman profile. The practical minimum diameter of the sleeves will also determine just how big the aluminum nosecone tip will need to be.

 

[bad_idea]

I've seen several people I know choose 3D printed aluminum for fin cans on high performance projects. I've been aware that it is probably the best all around method of making a fin can available to me, but I've been avoiding it because I want to build the fin can myself. Tonight, I decided to throw together a quick CAD model of my planned fin can, and get a quote for it. It comes out to around $300 printed in Aluminum.

I'm shocked it's so inexpensive nowadays. We live in an age of wonders.

 

[FredA]

Where did you go for the 3D printed Aluminum fincan quote?

 

[StreuB1]

$300???

Where?

 

[pugachu]

$300 is a really really good price for that part 3d printed. Do note that to get a good fit, you will most likely need the ID of the bore machined. 3d printed aluminum has a rough finish.

 

[mrwalsh85]

Oh geeze another Bare Necessity.... oh my bad lol ( poke at someone else lol ). You should look into the Loki M3400 blue. Slightly less total impulse but should get you the speed you need if you can get the optimal mass figured out.

Just FYI, Anthony C. got his L3 on a minimum diameter M3464 at Argonia a few years back. He got about 31k altitude. Punched through Mach 3 without issue. Just as a comparison point for altitude.

 

[Neutronium95]

$300 is a really really good price for that part 3d printed. Do note that to get a good fit, you will most likely need the ID of the bore machined. 3d printed aluminum has a rough finish.

That was the cheapest quote on Craftcloud. That site lets you get quotes on partsfrom a bunch of different manufacturers, primarily in China. Looking at the finish options, I'll probably get it glassblasted.


Getting the ID correct is very important. A few weeks ago someone at FAR needed to use the lathe at the launch site to sand the ID of his printed metal fin can to fit onto the motor.

Edit: I am considering getting it made with a slightly undersized ID, so that it can be turned to the perfect diameter on a lathe. Of course that relies on having easy access to a lathe.

 

[Adrian A]

How much heavier is the Al fincsn than CF fins? Seems like I could add a lot weight at the wrong end of the rocket.