Propeller Development, Did I Tell You It's Made Out of Paper?

Discussion in 'Gallery & Designs' started by Gil, Jan 11, 2007.

  1. Gil

    Gil Active Member

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    Number of Layers

    Eric,

    The cardstock is cut into fourths and laminated yielding lamination stock of around 1 mm (i.e. 20 layers of cardstock).

    I was just looking at a boolean subtraction of the stacked templates versus the lofted shape and realized that the template is not quite right due to a misguided assumption. I'll make a new template tonight and give it a try tomorrow.

    -Gil
  2. Gil

    Gil Active Member

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    Stack-up and Templates Render

    Had enough time to correct the layout error. The following render shows the results and the simulated stack-up.

    -Gil

    [​IMG]
  3. Gil

    Gil Active Member

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  4. Leif Oh

    Leif Oh Member

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    Another prop pattern...

    Gil (and Eric, and others),

    Many thanks, both of you, for bringing about a comparison of two methods in the same thread. I took the liberty of digesting the content of the thread over at Kartonbau.de (in English).

    In connection with that I also offered a download of a recent prop pattern from the Modele-Kartonowe 1:33 scale freeware download Thomas Morse S5 seaplane. It is eight-layered, and thus something of a compromise between your two approaches.

    Below a low-resolution illustration of the pattern. Download a 300 dpi pdf from the link above.

    Attached Files:

  5. Gil

    Gil Active Member

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    5 Layer Build

    Thanks Leif for the liaison work. As you noted the move amongst commercial producers is the layered prop design. It does provide a better prop than a hub with two blades glued onto it (as per the current build that stimulated this tangent path). There is one other alternative which doesn't require painting but consists of a prop armature covered by a printed wood grain cover. This would eliminate all the paint work and would, in many respects, be a more tenable solution. So that makes a third solution that will need to be looked into.

    The following stack-up was prepared from the new template set and does a good job matching the virtual build. The templates were bonded to the colored cardstock and cutout. A pin vise was used to punch a center hole through each layer the layers then stacked on the pin vise for glueing. PVA glue was liberally spread over the loosely separated parts and painted onto the parts with a brush effectively coating all surfaces. The plys were then carefully aligned and slowly pressed together. Clamping is not recommended as the stack resembles a circular staircase and will be deformed by conventional clamping methods. I found that using two vinyl erasers to compress the surfaces a section at a time worked fairly well. The hub area was compressed with a pair of flat surface duck bill pliers. Make sure that the overall prop remains straight in the transverse direction and that the spiral placement of each ply is correct. The assembly was then set aside to dry.

    Next comes sanding to shape and finishing...,

    -Gil

    [​IMG]
  6. Gil

    Gil Active Member

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    Finished 5 Layer

    Finished the 5 layer version. It turned out fairly well and has a natural wood look although it could use a CA soaking for added stiffness. One point to remember is that if you are using 3M 77 spray for layer adhesion you must avoid using any paint that has acetone or a like solvent which will debond the 3M contact cement.

    The shape was roughed in with a small Dremel sanding drum and finished with nail file sanding boards and sanding sponges (very handy items and worth going into the beauty supply store after). A final coat of Gloss Acrylic Medium flavored with some Burn Sienna finished the part that's pictured here. There's a little imperfection in the blade nearest the viewer but I'm not going to redo it (it will become the backside of course!).

    For appearence sake I think the top and bottom layers should be enlarged to give a larger ellipsoid shape for improved effect. Next version will be the armature wrapped version...,

    -Gil

    [​IMG]
  7. Bowdenja

    Bowdenja Active Member

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    Amazing Gil............. very realistic and the effect look great at this scale.


    Not to hijack.................... but how's the C-5 coming?

    john
  8. cgutzmer

    cgutzmer Guest

    this thread just keeps getting better!
    Chris
  9. Bengt F

    Bengt F Active Member

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    Laminated Card Propellor

    I second that, Chris,


    Gil, you´ve really got a wonderful finish on this propellor. It´s very nice to see an expert at work. It resembles an old laminated AXIAL prop for the WW I Fokkers:
    [​IMG]

    Best,
    Bengt :roll:
  10. silverw

    silverw Member

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    Great stuff Guys....

    Now I'm just going to have to build an airplane, just so I can try this out!

    .....:)
  11. Gil

    Gil Active Member

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    Surface Style Prop Experiment

    Started the last phase of this investigation with an experiment with the accepted method of prop building for cardmodels but with an advanced twist. The surfaces for a single blade were developed from the Helix prop data set. They were cutout and formed around a 0.25 inch diameter tube. They were then mounted on a flattened bamboo skewer, the edges glued together with PVA with the burnishing method. The results were then given a coat of tempera.

    Gluing the eges without a shaped form was a bit painful. The drawdown toward the hub means that the form can only support closure on one edge. This will probably be all right as the leading edge is the only edge which requires shaping, the trailing edge can easily be closed at an acute angle. Making up the form and trying that will be next step.

    -Gil

    [​IMG]
  12. cgutzmer

    cgutzmer Guest

    If you want you can build one for me as a test ;) I will send you my shipping address!
    Chris
  13. Gil

    Gil Active Member

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    Form Molded Single Surface Development

    A form was carved from MDF (Medium Density Fiberboard). I like this material for making jigs and forms as it is easily carved and sanded yet is hard enough to act as a form and can be polished to a high sheen. It's available at most all hardware and home improvement stores. Coating it with Bee's Wax disolved in Turpentine helps prevent the glue from sticking to it.

    Two propeller blanks were cut from 67# paper (that had been previously lacquer soaked) then dipped in water and aligned on the form such that the leading edges of both pieces touched when curved down on the form. A piece of 1/8 inch foam was then wrapped around the layup and then two vinyl erasers were used to clamp that. Wood clamps were used to apply force on the erasers and left to setup for an hour. Both formed halves were then arranged on the form so that theire leading edges touched and PVA glue was applied to the seam. The seam was then worked with a burnishing tool till the gap was no longer visible. The seam extends to the tip bow but not past it. The assembly was allowed to dry. PVA glue was then applied to the trailing edges and they were closed up and let dry. The edges were lightly sanded to remove fuzz and irregularities to finish.

    The next step is to perform the same operations but this time with printed blanks...,

    -Gil

    [​IMG]
  14. Bowdenja

    Bowdenja Active Member

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    Gil,

    Since the leading edge of a prop is slightly rounded, is it possible to create the prop from one piece, with the seam glued on the back edge?

    Another cool idea, but the way. Multiple uses.

    john
  15. Gil

    Gil Active Member

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    John,

    The camera angle makes it appear to be flat but it isn't. I thought about that as an option as it solves part of the positioning problem on the form. It will work "if" the prop has a straight section. The only problem is that the seam ends tend to curl out and are somewhat difficult to remove. Cutting the seams at an angle helps to remove it some.

    You're right about multiple uses but more on that later...,

    Best Regards,

    -Gil
  16. Gil

    Gil Active Member

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    Helix 82 mm Prop

    I tried out the form on a blank derived from a picture of a Helix prop from the web. It was too pixelated to turn out well but I went ahead and made it up just to see how everything worked. I've decided that you shouldn't see it as it's not exactly what I would call heartening. It does sort of, kinda look like a wooden prop if one squints hard enough...,

    I used the photo of the Helix prop as a source to draw one for the experiment the results are below. The hub barrel needs to be completed but that's fairly easy now that the prop blades and hub faces are finished. Even did the Helix logo decal for looks. Next step is to complete the conventional build with the new prop and the modified form.

    -Gil

    [​IMG]
  17. Gil

    Gil Active Member

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    Single Surface Helix 82 mm Prop Development

    The hub design was completed and a test model built (below).

    A self critique of the work shows that the blade width needs to be wider; shaft hole needs to be centered; prop hubs are dished-in; and the acrylic gloss finish was too thick and should have been thinned and sprayed instead of brushed.

    Despite these shortcomings the results are very encouraging. Next step is to build one more with the above issues corrected.

    -Gil

    [​IMG]
  18. Amazyah

    Amazyah Senior Member

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    Beautiful work Gil!

    Russell
  19. Gil

    Gil Active Member

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    Helix 1:33 Helix Prop Final

    This is the final installment of the World War I prop investigation. The prop built here is the standard single surface build common in most cardmodels of this genre. The twist is the use of two tools to aid in building the prop blades. The first tool is the leading edge forming tool which allows the two blade blanks to be mounted and spring clamped so that the seam can be glued and worked with a burnishing tool till the seam is no longer visible. The second tool is a holding tool which is useful in holding an individual blade while the trailing edge is glued. Each blade blank is rolled around a bamboo skewer to a half round shape which helps shape the blade surface prior to mounting it on the leading edge forming tool. Sand any rough spots on the finished blade edges with extra fine sandpaper and paint any white spots with brown watercolor paint. The hub is built up and the caps applied. Apply PVA to the end of each prop blank and allow it to dry till it's tacky before attaching the blades to the hub. Make sure one blade covers the hub seam. Fidget the blades till they are diametrically opposed and let the glue form a hard set. Apply water thinned PVA around the blade-hub joints with a small paintbrush to strengthen and allow to dry. Paint with Gloss Acrylic Medium with a drop of Burnt Sienna and it's done. One last note is that the card stock was prepped with Lacquer Sanding Sealer prior to construction (Nitrate Dope or Shellac will work as well). This is mandatory for the burnishing process.

    The second image is the engine which goes with the prop for the project which spawned this investigation...,

    -Gil
    [​IMG]
    [​IMG]
  20. Bengt F

    Bengt F Active Member

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    Gil,


    It´s a true joy to see such dedication and such a mastery in the craft of card model making. You are an example to us all.

    Thank you very much for this most interesting thread.

    Best,
    Bengt :D