Where can I get weight info on Semroc balsa nosecones?

Discussion in 'Low Power Rocketry (LPR)' started by Bill S, Dec 9, 2019.

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  1. Dec 9, 2019 #1

    Bill S

    Bill S

    Bill S

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    I'm working up a build, and was wondering if there was a source of weight info for Semroc balsa nosecones? I"m using Rocksim, and entered what info I had, resulting in a weight of 1.61 oz, but I was hoping to have more accurate info before purchasing one.

    Neither E-Rocket's website, nor Semroc's website has such info, and it isn't entered into the Rocksim parts database.

    Can anyone help?
     
  2. Dec 9, 2019 #2

    rharshberger

    rharshberger

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    Balsa nosecones are highly variable in weight due to the fact that balsa has a fairly large range of densities (g/cm3), unlike plastic which is very uniform. One source I saw for balsa density gave a range of 40 to 340 kg/m3, with a median density of 160 kg/m3.
     
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  3. Dec 9, 2019 #3

    Bill S

    Bill S

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    Wow, I had no idea there was such a range of possible densities. I can see where that would complicate things greatly.
     
  4. Dec 9, 2019 #4

    kuririn

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  5. Dec 9, 2019 #5

    Bill S

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    Kuririn, that was really helpful, thanks. :)
     
  6. Dec 9, 2019 #6

    kitbasher99

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    Just be aware, as stated above, that the Balsa that we receive to make our nose cones come in in varying densities. Use the weights that you find on the old Semroc sight as a starting point in your simulations. Once you have purchased any or all balsa parts, be they nose cones, transitions, tail cones, or fins, your best bet is to weigh the actual parts you have and input the actual weights into your sims, for the most accurate results.
     
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  7. Dec 9, 2019 #7

    Bill S

    Bill S

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    Kitbasher99, that is good advice. Thanks.
     
  8. Dec 9, 2019 #8

    caveduck

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    In my OpenRocket parts database (which now contains all nose cones Semroc ever made) I've normalized the masses to a standard balsa density, and fixed a ton of dimensional errors. The implied densities from the manufacturer quoted weights are all over the place. https://github.com/dbcook/openrocket-database
     
  9. Dec 10, 2019 #9

    Sheryl@semroc

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    We ordered balsa in 2x2 and 4x4 32" long "sticks" for cones. Each one was weighted and we had a certain spread that we used. Some were too light, some too heavy and we had to send them back. The lighter they were, the harder it was to get a smooth finish. We did the same for the balsa and basswood planks. Not sure what procedure Randy uses.
     
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  10. Dec 10, 2019 #10

    Bill S

    Bill S

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    That's good to know; at least the density is within a certain range, rather than all over the place. :)
     
  11. Dec 10, 2019 #11

    caveduck

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    That's certainly true, the "contest balsa" that glider people love is too light to withstand nose cone making, even by hand! If you average the quoted nose cone weights and compute density from the dimensions, you get something around 7lb/ft3 for Estes and Semroc, but I don't have any detailed information about how the manufacturers generated the catalog specs (weighed actual samples seems likely due to scatter in data ??).
     
    Last edited: Dec 10, 2019
  12. Dec 10, 2019 #12

    BEC

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    The recent production balsa nose cones I've gotten from eRockets have tended to run towards the light end of the range, with the issues that Sheryl mentioned above. They are certainly usable, but not as smooth as the ones Carl and Sheryl and Bruce made.
     
  13. Dec 12, 2019 #13

    neil_w

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    I have gotten “rough” balsa cones but don’t really care; they’re all gonna get the same CA/filler treatment and end up glassy smooth. :)
     

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