Which material weighs less per foot: thin wall FG or standard wall CF?

Pretty much what it says in the title. I'm doing a build that needs to be ultra-light and really strong (hopefully breaking mach 1.5). I definitely need the strength of composite tube, so I was wondering which of the two would be a better option. Thanks!

Ummm......... thin wall is lighter.

blackjack2564 said:

Ummm......... thin wall is lighter.

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Do you have data for that? Nobody seems to publish any weight data for standard wall carbon fiber.

They should make thin wall CF.

You could build the tube you want.

That said- for a flight of that velocity you likely do not need CF.

What diameter airframe and what manufacturer?

I'm not sure what you are asking. What do you mean for standard wall carbon fiber? As far as I know there is no standard and it is the manufacturer who sets the standard. There are wall schedules for piping used in the oil and gas industry that are determined by ASME.

That said, CF is stronger than FG all things being equal. The grams/cm3 for CF is a little less than FG. So all things being equal, the same wall CF tube will be a little lighter than FG. All things being equal, CF tube will be 1.5 to 3 times the price of FG tube.

Greg

markkoelsch said:

They should make thin wall CF.

You could build the tube you want.

That said- for a flight of that velocity you likely do not need CF.

What diameter airframe and what manufacturer?

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29mm. It would be thin wall from Madcow or carbon from Wildman. To be entirely honest, I'm mostly interested for simulation purposes, since it seems that no manufacturers of filament wound carbon say how much it weighs. If someone could tell me the weight of a different diameter of carbon tube, I could probably math it out from there.

GregGleason said:

I'm not sure what you are asking. What do you mean for standard wall carbon fiber? As far as I know there is no standard and it is the manufacturer who sets the standard.

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Composite airframes have relatively standard inner/outer diameters. I know for a fact that a filament wound fiberglass nosecone from Wildman fits properly on fiberglass tubes from Wildman, Madcow (technically Rocketry Warehouse, but now that tube is from Madcow), and Apogee. I guess it might be different for carbon fiber tubes, but as far as I know, carbon fiber tubes are made the exact same way as fiberglass. It would make sense that they would also fit the standard inner and outer diameters.

If you need light weight, a cardboard tube will handle Mach 1.5 just fine. Especially in 29mm.

But as for your original question, I'd say the densities of both the CF and FG tubes are very similar, so the thin wall FG would be lighter.

I would think it all depends on the fiber to resin content in the laminate.

Glass has a higher density than carbon fiber, as for the resin's density, that remains constant.

I would still consider the glass to be heavier.


Alexander Solis - TRA Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

Maxwelljets said:

29mm. It would be thin wall from Madcow or carbon from Wildman. To be entirely honest, I'm mostly interested for simulation purposes, since it seems that no manufacturers of filament wound carbon say how much it weighs. If someone could tell me the weight of a different diameter of carbon tube, I could probably math it out from there.



Composite airframes have relatively standard inner/outer diameters. I know for a fact that a filament wound fiberglass nosecone from Wildman fits properly on fiberglass tubes from Wildman, Madcow (technically Rocketry Warehouse, but now that tube is from Madcow), and Apogee. I guess it might be different for carbon fiber tubes, but as far as I know, carbon fiber tubes are made the exact same way as fiberglass. It would make sense that theyalso fit the standard inner and outer diameters.

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Maybe, maybe not. Depending on the wind pattern and such, amount of epoxy etc you could get different densities.

Rocket Warehouse used to list the weight per foot.

After digging through the build heap at my college rocketry clubs workshop, I managed to find a small piece of 38mm standard wall carbon fiber (manufacturer unknown). I weighed it and extrapolated and found that this particular tube weighed almost exactly 3.0 oz/ft. Madcow's website says 38mm thin wall fiberglass weighs 2.6 oz/ft, and 38mm standard wall fiberglass weighs 4.0 oz/ft. So it appears that thin wall FG weighs about 5/6 what the standard carbon weighs. While there is some variance by manufacturer, I doubt that CF tube density could vary by almost 16%.