Aluminum parts are better then composites for the N5800 C-star

[ColumbiaNX01]

So everyone is saying the the best way to go for the 98mm diameter N5800 is build it with an all aluminum design. Thats great and all. If this is feasible where is the best place to start in pursuing an all aluminum fin can and nose cone. Most of us here do not have the tools to hand make these kind of parts.

 

[dixontj93060]

Remember that taking this step begins to limit your launch venues, e.g., metal rockets not allowed at Argonia.

 

[ColumbiaNX01]

That maybe so. I saw on their website that it says that the metal parts have to be proven to be necessary for the successfulness of the flight. They have to be painted nothing metalic showing. That is what I took from it, I could be wrong. I saw it on their Airfest 19 link.

 

[cavecentral]

Just make it 30ft long and heavy - might not need the metal parts if you slow it down a bit. LOL.

 

[troj]

That maybe so. I saw on their website that it says that the metal parts have to be proven to be necessary for the successfulness of the flight. They have to be painted nothing metalic showing. That is what I took from it, I could be wrong. I saw it on their Airfest 19 link.

I think you're going to have an uphill battle to get them to let you fly it there

 

[patelldp]

Please take a step back and consider what you are trying to accomplish.

Are you just trying to fly an N5800?
Are you just trying to fly an N5800 in an MD rocket assured to hold together?
Are you aiming for an altitude record?

Make a mission statement, and start thinking about how you plan to accomplish it. That should answer a lot of your questions about materials, location, etc.

More needs to be done on your end prior to asking these questions. We're talking an N5800, not an entry level rocket motor. I'm not expecting you to know everything, but let's say several people who know a hell of a lot have failed at what you are asking about.

 

[ColumbiaNX01]

No altitude record. Fly a N5800 in a Minimum Diameter rocket. I know people have failed at this attempt that know more about things than I do. What I do know is for the most part composites will not work. Of those who have failed haven't they used composite fin cans and those who succeeded used a metal fin can?

 

[CarVac]

The first successful N5800 flight was a flying motor case with a composite forward airframe and nosecone, and aluminum fins. It went 56,000 feet and Mach 3.5

The second successful N5800 flight was all-aluminum and went only 30,000 feet under Mach 3 because it was heavy and draggy.

Bare Necessities didn't fly successfully, but all of the composite parts survived the Mach 2.5-3-ish separation event without the slightest damage.

 

[BBrown]

That maybe so. I saw on their website that it says that the metal parts have to be proven to be necessary for the successfulness of the flight. They have to be painted nothing metalic showing. That is what I took from it, I could be wrong. I saw it on their Airfest 19 link.

Andrew,

Just to be clear, a rocket consisting of an aluminum fin can and an aluminum nose cone will not be allowed to fly at the rocket pasture at Argonia regardless of how it's painted. As the prefect of the Kloudbusters Rocket club, I have a responsibility to all of our members and an agreement in place with one of our landowners that we will not fly aluminum rockets at the rocket pasture. If you decide to build this rocket, you will need to find another venue.

Bob Brown

 

[ColumbiaNX01]

Andrew,

Just to be clear, a rocket consisting of an aluminum fin can and an aluminum nose cone will not be allowed to fly at the rocket pasture at Argonia regardless of how it's painted. As the prefect of the Kloudbusters Rocket club, I have a responsibility to all of our members and an agreement in place with one of our landowners that we will not fly aluminum rockets at the rocket pasture. If you decide to build this rocket, you will need to find another venue.

Bob Brown

okay

 

[CCotner]

Just make it 30ft long and heavy - might not need the metal parts if you slow it down a bit. LOL.

On the other hand, if you make the lightest possible composite airframe and an aluminum nose tip, you'll probably melt the nose tip... depending on launch altitude the nose tip exceeds the melting point of aluminum.

 

[ColumbiaNX01]

Melting point of aluminum is 1221 degrees F. Isnt regardless of the thickness of the aluminum its gonna melt at the same temperature at 1/4" thick or at 1' thick?

 

[daveyfire]

Isnt regardless of the thickness of the aluminum its gonna melt at the same temperature at 1/4" thick or at 1' thick?

Yes, but.

 

[G_T]

If you get real concerned about it, you could hollow it out and fill with water. Small holes in tip... Instant vapor layer and cooling via boiling water.

Sorry, it is getting late. Just a crazy, possibly workable idea I've had.

Gerald

 

[stantonjtroy]

I work aerospace composites for a living so I can offer a couple of sugestions. Most of the failures with composites occure for two reasons. First, for maximum strength get away from filiment wound tubes and switch to a multiply layup of Triaxial carbonfiber rotating the bias 30deg per ply. Number of plys is governed by strength requirements. Additionally you need to do a vac bag layup to achieve the proper density and strength. Second, and of equal importance, is get away from the hobby grade epoxies and go for a good aerospace grade, heat resistant system. Huntsman Araldite® MY 0510 is a good example but there many others. Fibraplex makes a great family of BMI (bismaleimide) epoxies that offer some of the best thermal resistant properties I've used. Website here: https://www.fibraplex.com/BMIResins.htm . Once the layup has cured a high temp post cure will allow the structure to handle max temperatute exposures.
One factor that is almost always overlooked is abrasion/erosion. Much of the composite breakdown experienced is due erosion at transonic and sonic velocities. A good Fluoroelastomer paint applied to the nosecone and leading edge of fins will take care of this. Total film thickness should be 11-14 mils.
As has been pointed out, your goal is a major step up. At this level the appraoch needs to be less hobby rocket and more spacecraft. FWIW

 

[dixontj93060]

Can you provide a pointer to the paint/coating you mention?

I work aerospace composites for a living so I can offer a couple of sugestions. Most of the failures with composites occure for two reasons. First, for maximum strength get away from filiment wound tubes and switch to a multiply layup of Triaxial carbonfiber rotating the bias 30deg per ply. Number of plys is governed by strength requirements. Additionally you need to do a vac bag layup to achieve the proper density and strength. Second, and of equal importance, is get away from the hobby grade epoxies and go for a good aerospace grade, heat resistant system. Huntsman Araldite® MY 0510 is a good example but there many others. Fibraplex makes a great family of BMI (bismaleimide) epoxies that offer some of the best thermal resistant properties I've used. Website here: https://www.fibraplex.com/BMIResins.htm . Once the layup has cured a high temp post cure will allow the structure to handle max temperatute exposures.
One factor that is almost always overlooked is abrasion/erosion. Much of the composite breakdown experienced is due erosion at transonic and sonic velocities. A good Fluoroelastomer paint applied to the nosecone and leading edge of fins will take care of this. Total film thickness should be 11-14 mils.
As has been pointed out, your goal is a major step up. At this level the appraoch needs to be less hobby rocket and more spacecraft. FWIW

 

[CCotner]

First, for maximum strength get away from filiment wound tubes and switch to a multiply layup of Triaxial carbonfiber rotating the bias 30deg per ply. Number of plys is governed by strength requirements. Additionally you need to do a vac bag layup to achieve the proper density and strength.

First of all, I am pleased to see someone other than me insist that without some form of compression, a layup isn't very strong-vacuum bagging is a start. Sailboat mast companies use a vacuum bag, then wrap that in heat-shrink tube, then put it in an autoclave and pressurize from the outside of the vacuum bag to get even higher compression. It's not about removing epoxy as much as it is about forcing fibers to lay together-right?

Second, I looked extensively for a place to buy triaxial CF for a project I worked on last year but was unable to find anything beyond sketchy and small remnants on e-bay, or minimum-order-is-multiple-100yd-rolls places (like actual manufacturers, like Hexcell.) Where should we look?

 

[BLKKROW]

First of all, I am pleased to see someone other than me insist that without some form of compression, a layup isn't very strong-vacuum bagging is a start. Sailboat mast companies use a vacuum bag, then wrap that in heat-shrink tube, then put it in an autoclave and pressurize from the outside of the vacuum bag to get even higher compression. It's not about removing epoxy as much as it is about forcing fibers to lay together-right?

Second, I looked extensively for a place to buy triaxial CF for a project I worked on last year but was unable to find anything beyond sketchy and small remnants on e-bay, or minimum-order-is-multiple-100yd-rolls places (like actual manufacturers, like Hexcell.) Where should we look?

https://www.solarcomposites.com/composites/compositecarbon.html#3KBiax

I don't know if this would work?

 

[stantonjtroy]

Can you provide a pointer to the paint/coating you mention?

The paint we use is by CAAP Co. ( https://caapco.com/ ). I think PPG has a formulation but I won't swear to it. Another company is Han Tech.

First of all, I am pleased to see someone other than me insist that without some form of compression, a layup isn't very strong-vacuum bagging is a start. Sailboat mast companies use a vacuum bag, then wrap that in heat-shrink tube, then put it in an autoclave and pressurize from the outside of the vacuum bag to get even higher compression. It's not about removing epoxy as much as it is about forcing fibers to lay together-right?

Second, I looked extensively for a place to buy triaxial CF for a project I worked on last year but was unable to find anything beyond sketchy and small remnants on e-bay, or minimum-order-is-multiple-100yd-rolls places (like actual manufacturers, like Hexcell.) Where should we look?

Correct, Compression is a big part of it. More specifically resin to fiber ratio. Many wet layups tend to be a bit resin rich. Vac bag with a N4 airweave useally gets good compression and a good ratio allthough clave cure offers the best strength. allthough autoclave cure is best, most people don't have access to that kind of equipment. Vac bag is a little more easy to come by.
Soller is actually the vendor I have for Triax Carbon. Triax Glass is available from Fibre Glast.

 

[CCotner]

The paint we use is by CAAP Co. ( https://caapco.com/ ). I think PPG has a formulation but I won't swear to it. Another company is Han Tech.



Correct, Compression is a big part of it. More specifically resin to fiber ratio. Many wet layups tend to be a bit resin rich. Vac bag with a N4 airweave useally gets good compression and a good ratio allthough clave cure offers the best strength. allthough autoclave cure is best, most people don't have access to that kind of equipment. Vac bag is a little more easy to come by.
Soller is actually the vendor I have for Triax Carbon. Triax Glass is available from Fibre Glast.

At the time I looked, Soller didn't have it in stock, and I was looking for more... options in terms of thickness and stuff.

Presumably, you roll a tube from it such that you have fibers in column, and then +- 60 degrees from column? Or fiber in hoop, and then +-60 from hoop (+-30 from the column)? The second might actually be stiffer in bending, even though there's no actual fibers along the axis of the column.


Also, if I may ask, why not filament winding? Assuming you can control the wind angle(s) on a custom tube (the wind angles on hobby tubing are generally not good), shouldn't it be stronger? The sailboat mast people use filament winding, or rather ribbon-wrapping (big, 1-2" wide spread tows wrapped on a 4-axis CNC winder).

 

[stantonjtroy]

At the time I looked, Soller didn't have it in stock, and I was looking for more... options in terms of thickness and stuff.

Presumably, you roll a tube from it such that you have fibers in column, and then +- 60 degrees from column? Or fiber in hoop, and then +-60 from hoop (+-30 from the column)? The second might actually be stiffer in bending, even though there's no actual fibers along the axis of the column.


Also, if I may ask, why not filament winding? Assuming you can control the wind angle(s) on a custom tube (the wind angles on hobby tubing are generally not good), shouldn't it be stronger? The sailboat mast people use filament winding, or rather ribbon-wrapping (big, 1-2" wide spread tows wrapped on a 4-axis CNC winder).

Fiber orientation depends a great deal on the number of plys and design needs. Sadly there is no "Rule of thumb" that I'm aware of (Doesn't mean there isn't one). Typically I see the outer ply oriented 0deg on the longitudinal axis of the structure. As for filament winding vs weave, the debate continues. If the tube is being custom wound for a specific strength, using an epoxy chosen specifically for the task they can be fine. Most commercially fabricated wound tubes used in hobby rocketry aren't made for the loads a massively powerfull rocket would deliver. Weaker epoxies, relatively speaking, are typically what's available at production prices and loads are tested statically not dynamically. My personal experience with filiment wound structures (F-16 nosecones) is they're plenty strong but when they break down under load they do so very rapidly. Woven fabrics tend to maintain structural integrity longer. We've made fwd facing, supersonic structures from woven (twill) fabrics only 6 plys thick and they're still going strong. As I say, it's a debate that will continue with commited opinions on each side. I guess the best answer I can give to the question posed is that a wound tube, PURPOSELY designed for the flight and thermal loads expected would be just fine.

 

[CCotner]

Fiber orientation depends a great deal on the number of plys and design needs. Sadly there is no "Rule of thumb" that I'm aware of (Doesn't mean there isn't one). Typically I see the outer ply oriented 0deg on the longitudinal axis of the structure. As for filament winding vs weave, the debate continues. If the tube is being custom wound for a specific strength, using an epoxy chosen specifically for the task they can be fine. Most commercially fabricated wound tubes used in hobby rocketry aren't made for the loads a massively powerfull rocket would deliver. Weaker epoxies, relatively speaking, are typically what's available at production prices and loads are tested statically not dynamically. My personal experience with filiment wound structures (F-16 nosecones) is they're plenty strong but when they break down under load they do so very rapidly. Woven fabrics tend to maintain structural integrity longer. We've made fwd facing, supersonic structures from woven (twill) fabrics only 6 plys thick and they're still going strong. As I say, it's a debate that will continue with commited opinions on each side. I guess the best answer I can give to the question posed is that a wound tube, PURPOSELY designed for the flight and thermal loads expected would be just fine.

Ok, yeah that makes sense.