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-   -   Cardstock weight - lbs vs GSM? (http://www.oldrocketforum.com/showthread.php?t=21974)

SolarYellow 11-07-2023 11:08 PM

Cardstock weight - lbs vs GSM?
 
I see a lot of recommendations to use "110 lb" cardstock for rockets. However, when I go to shop for "110 lb" cardstock, I see some at ~200 grams/square meter (gsm) and some at ~300 gsm. Which gsm weight is the one I should be using?

If it's the 200, am I good to use the pack of 176 gsm cardstock I have on hand already?

I'll mostly be layering fins for @HCMbanjo's process of gluing the 110-lb printed wrap over a core of cereal box cardboard.

The worst case I think I'll be trying is Berthas in 13 and 18mm with those long fins. Maybe a BT-5 Alpha or three.

I suppose I could also find some heavier core material, especially white all the way through, which would allow me to color the edges more consistently.

Bill 11-08-2023 01:22 AM

Between 270 - 308

https://altenew.com/pages/cardstock...20270%20-%20308.


Bill

SolarYellow 11-08-2023 07:15 AM

Is that what you actually use, or did you Google for an answer? I read that whole article, and it's a random, rambling compilation of information that looks like it was computer-generated.

It includes conflicting statements:

"110 lb cardstock would have a GSM between 270 - 308"

"110 lb cardstock which weighs 360gms/m2"

It presents a range of different information about the topic, but without any real organization or any relating the different blocks of information to each other. The kind of "scrape and dump" of information from random sources that a dumb computer program would do, rather than an intelligent human who actually understands what s/he is writing about.

The entire article also fails to mention the 110 lb cardstock that comes in around 200 gsm, or to explain why there are multiple different systems in effect, what they mean, how they relate to each other, etc.

And I still don't have any confidence in picking a gsm value for the "110 lb" cardstock I'm supposed to use to build rockets. Because NOTHING in that article said anything about building rockets.

astronwolf 11-08-2023 10:47 AM

Quote:
Originally Posted by SolarYellow
If it's the 200, am I good to use the pack of 176 gsm cardstock I have on hand already?

You are good to go. I'd just use the stuff I have on hand.

BigRIJoe 11-08-2023 11:27 AM

Would cardstock fins be a good alternative to balsa in competition models?

SolarYellow 11-08-2023 11:32 AM

Quote:
Originally Posted by astronwolf
You are good to go. I'd just use the stuff I have on hand.


Thanks. I did a bunch of math and reached the same conclusion. Full details over on that other forum.

https://www.rocketryforum.com/threa...3/#post-2509978

Gus 11-08-2023 02:39 PM

I use a ton of paper for competition models.

Be aware that the paper weights listed for products is often inaccurate. No one actually polices this information so the companies are free to list whatever they like, and who knows how they come up with a number they choose.

Often times the numbers are wildly inaccurate. Paper listed at 30 pounds may actually weigh more than another paper listed at 40 pounds. Unfortunately, the only way around this is to actually purchase the papers and weigh them yourself.

As for using card stock for fins for competition models, no, that's a really bad idea. Unless you are talking about built up fins for scale models where weight really doesn't matter.

The issue in using paper for rocket models is always a trade-off between the weight of the paper and its stiffness. The less it weighs the less stiff it will be. The only way to tell if this is a critical issue for a particular model is to actually build it and fly it. Fortunately, paper is usually cheap.

SolarYellow 11-08-2023 03:55 PM

Quote:
Originally Posted by Gus
Be aware that the paper weights listed for products is often inaccurate. No one actually polices this information so the companies are free to list whatever they like, and who knows how they come up with a number they choose.

Often times the numbers are wildly inaccurate. Paper listed at 30 pounds may actually weigh more than another paper listed at 40 pounds. Unfortunately, the only way around this is to actually purchase the papers and weigh them yourself.


Click through to my link above. In the related discussion on the other forum, it is clear there are at least four different "basis" systems in use in the commercial advertising of products the participants actually have in their possession.

The bottom line is that stating the thickness/area density of paper in "lb" without stating which basis system was used to determine that weight is like stating a speed in miles, meters, feet, or inches. It's missing the denominator and doesn't actually tell anyone what they need to know.

On the other hand, grams and meters don't change, so the gsm number should be consistent. There may be no one policing it, but I am not aware of any evidence that manufacturers are cheating on their advertised gsm values.

Bill 11-08-2023 07:06 PM

Quote:
Originally Posted by SolarYellow
Is that what you actually use, or did you Google for an answer? I read that whole article, and it's a random, rambling compilation of information that looks like it was computer-generated.


I googled for "110 lb cardstock to gsm."

To get rid of the click-tracking gobbledygook, I clicked on the link, copied the page address and pasted it into my reply. It was late and I did not read it first. Just trying to be helpful...


Bill

PaulK 11-09-2023 06:53 PM

I use the OfficeMax brand, says 110 lb on the package. There are no other weight specs. It doesn't look like OfficeDepot has a house brand anymore. I can weigh some if it helps.


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