PAPER-COVERED BALSA FINS

Discussion in 'Beginners & Educational Programs' started by Luzwingnut, Feb 9, 2019.

Help Support The Rocketry Forum by donating:

  1. Feb 9, 2019 #31

    GlenP

    GlenP

    GlenP

    Well-Known Member

    Joined:
    Oct 4, 2014
    Messages:
    1,257
    Likes Received:
    62
    330524E0-1DF4-4793-931E-995F76F00745.jpeg Another motivation, you can print a complex roll pattern and markings on cardstock paper, so that you don’t have to mask and paint the fins. Just clear coat. I did this on the Dr. Zooch Saturn 1b for example. He provided roll patterns for all the body tube wraps, so I decided to make my own fin wraps.
     
    Luzwingnut likes this.
  2. Feb 9, 2019 #32

    Luzwingnut

    Luzwingnut

    Luzwingnut

    "Everyday... a new adventure!" TRF Supporter

    Joined:
    Feb 2, 2019
    Messages:
    72
    Likes Received:
    9
    Gender:
    Male
    Location:
    Palestine, Texas
    ABSOLUTELY loving the interest that this thread has inspired! A LOT of great ideas!

    Using everyone's input and carefully reading through your directives and reasonings, I've learned some NEW ideas concerning the methods and techniques I sought to highlight. I am MOST sincere in graciously thanking everyone for their input! GOOD STUFF!

    THANK YOU!

    I did use the 400 grit to LIGHTLY smooth any surface imperfections on the FINISHED product; however, 400 grit "could be" too aggressive IF not being ABSOLUTELY careful... I'll try 800 or even 1200 grits on a future build, I think.

    NO WARPAGE!!! After just letting the FINS air dry, without any weightings... the FINS were ARROW STRAIGHT. (But these ARE smallish FINS... 1/10 scale Estes Patriot.) On a larger FIN than these, I WOULD HAVE ensured that they were weighted to prevent warpage.

    These are READY for primer and paint!
     
  3. Feb 9, 2019 #33

    Luzwingnut

    Luzwingnut

    Luzwingnut

    "Everyday... a new adventure!" TRF Supporter

    Joined:
    Feb 2, 2019
    Messages:
    72
    Likes Received:
    9
    Gender:
    Male
    Location:
    Palestine, Texas
    WOW! Very impressive, GlenP!! Those turned out VERY nice!

    What a GREAT idea... I've got to fire up my printer, now!
     
  4. Feb 10, 2019 #34

    BABAR

    BABAR

    BABAR

    Builds Rockets for NASA TRF Supporter TRF Lifetime Supporter

    Joined:
    Aug 27, 2011
    Messages:
    3,305
    Likes Received:
    143
    I have been building for a while now and I still have some difficulty with terms.


    Regarding terms for the fin edges.
    Leading/forward edge I get
    Trailing/rear edge I get
    To me, both Root and Base edge BOTH refer to the part that sticks to the rocket. I call this the Root edge.

    Is there a standard term for the Lateral Edge (maybe it IS just called “Lateral Edge”)?

    I did a search and found this
    https://www.rocketryforum.com/threads/fin-surface-nomenclature.10393/
    But still didnt answer my question
    Also the drawing post 3 has the sweep angle wrong, it should be from leading edge to root.
    Also not sure why #6 is labeled “Semi Span” instead of just span

    If you paper fins and the fins are perfect square or perfect diamond shapes, make sure to keep track of the grain direction, a few light pencil marks on the paper do the trick and are easily covered by paint. Don’t use pen, it may bleed through paint.

    Square edge fins (no rounding or tapering) are certainly not aerodynamic, but for sport rockets they work great and often look very stylish (see Estes FlutterBye). Papering is easy, just leave edges that fold over. Leaves you with no raw balsa edges to seal or finish or taper or round or anything.

    One trick for getting your paper clean to the root edge but not over it: Oversize the span/width of your fin when you cut it, so maybe 1/8 “ or 1/4” extra at the root. Paper all the way to the root. When dry put your normal (non-supersize) template on the fin and mark in pencil where the Root edge should be. Use knife and metal ruler and cut here. You will have a perfectly glued clean paper/balsa edge. As a plus, if you extend that edge 1/4”, after you paper it you have an extra bit of room you can put a couple of clothes pins on which won’t contact your final finished edge. You can use the pins as handles (keep those gluey fingers off the paper!), even use the pins as stands to allow the fin to dry. Again, once dry pull the clothes pins off and cut the Root Edge line at the correct spot.
     
  5. Feb 10, 2019 #35

    afadeev

    afadeev

    afadeev

    Well-Known Member

    Joined:
    Sep 21, 2017
    Messages:
    582
    Likes Received:
    78
    Neah, we just make things up as we go along.
    Clarity in communication is always helpful, and to me, "root" and "base" imply the same thing. Outboard edge is the "tip".
    That was one of the confusing references in OP's posts, but there were sooooo needlessly many, that I skipped reading half of them ;-)


    Good point.
    Another reason for leaving square edges is to induce "split fin whistle" between a pair of inline fins!

    a
     
  6. Feb 10, 2019 #36

    BABAR

    BABAR

    BABAR

    Builds Rockets for NASA TRF Supporter TRF Lifetime Supporter

    Joined:
    Aug 27, 2011
    Messages:
    3,305
    Likes Received:
    143
    Ooooh, I will have to try that!
     
  7. Feb 11, 2019 at 3:59 AM #37

    Knuckledragger

    Knuckledragger

    Knuckledragger

    TLAR Engineering hack

    Joined:
    May 23, 2017
    Messages:
    78
    Likes Received:
    4
    I pretty much always have a cup of coffee near by so after I make a cup, I'll pull a small bowl of hot water from the coffee maker and let my bottle of wood glue (Titebond) sit in it while I mark the paper grain and orient the fin on the paper; to me, warm glue flows a little easier and after the glue and paper are applied, I roll it out with a glass guitar slide a friend donated to the cause. I fold the paper pattern in half, run a small bead of glue in the trough and drop it over the leading edge then roll it out to the trailing edge, wipe off any excess and let them dry for a couple of days. I lay them on a piece of sheet metal and put magnets (not rare earth!) along the tops near the edges and have no warpage. I do have two questions though? Does anyone cut the paper longer at the root edge, say 1/2" or so and glue the fin in place, let it dry, then glue the extra paper to the BT? After seeing so many popped fins I was wondering if the extra surface would help secure the fin at the tube given how thin the wood to BT area is. The second question is using slightly thinned glue. Titebond gives the directions for thinning the glue so would the thinner glue wick in to the balsa/BT any better? I realize there is nominal strength degradation with thinned glue but I'm not building furniture joints. Any insights...
     
  8. Feb 11, 2019 at 4:27 AM #38

    Luzwingnut

    Luzwingnut

    Luzwingnut

    "Everyday... a new adventure!" TRF Supporter

    Joined:
    Feb 2, 2019
    Messages:
    72
    Likes Received:
    9
    Gender:
    Male
    Location:
    Palestine, Texas
    Uhm.. now that IS a really good consideration, Knuckledragger. I'll give it a try and see what happens.
     
  9. Feb 11, 2019 at 5:48 AM #39

    Rex R

    Rex R

    Rex R

    LV2

    Joined:
    Apr 21, 2010
    Messages:
    5,853
    Likes Received:
    68
    thinned glue shrinks more than unthinned glue and so pulls the paper into the grain, leaving an un smooth surface. for this reason I prefer white glue over the 'yellow wood glue' for applying paper skins.
    Rex
     
    Luzwingnut likes this.

Share This Page