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  1. #1
    green river rc's Avatar
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    Ribs for tapered wings

    My 15 year old son is scaleing a Peck-Polymers Prairie Bird x3 for electric RC. He has everything layed out very nicely except for the ribs in tapered wing end panels. He is planning on using a Clark Y airfoil. I also have a project I'm working on that the origional design has a tapered foam wing core which I do not like for this model, I want to make it a build up balsa wing but again the same problem of cutting ribs for a tapered wing. Any tips?
    With the parts left over, Im going to build a motorcycle.

  2. #2
    limeybob's Avatar
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    RE: Ribs for tapered wings

    well, one way is to make a root and tip rib, sandwich wood for the ribs in between and sand away.
    Bob
    Laser-Design-Services
    JetMach manufacturer

  3. #3
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    RE: Ribs for tapered wings

    Or get the Profili wing design program.

  4. #4
    limeybob's Avatar
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    RE: Ribs for tapered wings


    ORIGINAL: longdan

    Or get the Profili wing design program.
    yes, as well.I use it all the time.
    Bob
    Laser-Design-Services
    JetMach manufacturer

  5. #5

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    RE: Ribs for tapered wings

    I use Rhino 3D, but I'm sure this process works with other 3D cad packages as well. Draw the root and tip ribs. and separate them by 1/2 wing span or the length of the half wing. rotate the tip rib for wash out if desired. Now skin the wing. In Rhino it is "sweep two rails" Inow have what looks like the finished wing. Ithen make a series of slices at the desired rib positions. The edge curve for those slices is your finished airfoil at that point. Once you get the hang of this, go back to the two ribs and now draw in the spar location on them, 3D the spars. Ilike to make them a bit higher so they protrude from the skin. This makes it easy to delete them from the finished product. Ioffset the rib slices by the thickness of the LE sheeting and any cap strips so the drawing is the exact ribs to cut. If anyone is interested, I'll send them a copy of a glider wing I just did for a fellow club member. I can send it either as a Rhino 3DM file or as a DXF. I'm sure the layers will stay intact and youcan walk through it. process Just PMme for the file and I'll be happy to answer questions about it.

    Don

  6. #6

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    RE: Ribs for tapered wings

    Of course, any 2D or 3D drawing or modelling package can be used.
    But for a simpler approach:
    1. Draw one of the profiles on a sheet of paper.
    2. Put on photo copier, and use whatever scaling factor is required to give you the next rib, e.g. 110%
    3. Repeat with 120% etc.
    4. Cut ribs according to templates.

    Magne

  7. #7

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    RE: Ribs for tapered wings

    First, through all the software away.

    The only two ribs you have interest in is the root and tip rib. Just as if you were cutting foam wings.

    Make your root rib and make your tip rib.

    I'm guessing the main spar will be straight?

    Glue the LE, TE, to the two ribs.

    All the other ribs can be rectangles with no airfoil. They can actually be glued in place.

    Get a long sanding bar and have to it.

    The wing will be done before you can say 3D.

    You can, if you choose, draw a plan view of the wing, setback and all. Only a single line is needed for each rib spacing. The length can be determined, quite easily, this way.

    Wanna see some wings? look around, they are everywhere, and no 3D program was used for any of them!
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  8. #8

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    RE: Ribs for tapered wings

    Charles, there are many routes from New York to Los Angles and many transportation modes. All get you there, but some combinations may be faster, more comfortable, more scenic, etc. Your way works as well as mine. From the photos of your shop, you have more experience at building than I do and you are more sure of the outcome before you commit to cutting wood. My 3D drawing approach lets me make most of my mistakes on th PC vs in the wood. Besides, it makes me think of the build process as I"m making the drawings. And all I have to do is print off a new set of templates for the next time I need to build or repair a wing.. Either method will give you good results.

    From your photos, it looks as if you have a fondness for the Gee Bee. That plane has always been on my favorites list. My trouble is that my list is too long.

    Don






  9. #9

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    RE: Ribs for tapered wings

    Don,


    Sure, and I agree, you cannot do without CAD and 3D.

    I use CAD all the time.

    My graphics program allows me to draw and print. I can scale at the pressing of a key, but is any drawing program "really" necessary for building model airplanes?

    That's my only point.

    Here's my CAD at work. All the drawings of the gear was done in my program, right over these plans, which I scanned in. I actually drew the front fiew in minutes.
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  10. #10
    green river rc's Avatar
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    RE: Ribs for tapered wings

    Thanks for all of the advise so far, love the Gee Bee!
    With the parts left over, Im going to build a motorcycle.

  11. #11

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    RE: Ribs for tapered wings


    ORIGINAL: Avaiojet

    Don,


    My graphics program allows me to draw and print. I can scale at the pressing of a key, but is any drawing program "really" necessary for building model airplanes?

    Charles, no more necessary that a scroll saw, band saw and disk sander. Or the drawer full of small bar clamps, It is just a very useful tool. Now if I'm building a kit, it isn't much use, but when I'm able to scale my 4*60 wing down to fit a 40 size stick type plane, eliminate some of the spars and make some other mods andthen have a Sig quality set of parts templatesto work with, it becomes a very useful tool. Could I do it another way, of course I could. ButI like tools. The more the better. My Rhino is just another handy tool I have. Besides it gives my band saw, scroll saw and disk sander a lot more reason to take up shop space.

    Don

    Ijust had to adthis. We managed to win WW II with planes designed and built with slide rules and French curves. It was late into my apprenticeship in the early 60's that I first heard about this great milling machine that ran it's self and was so accurate that you could have it bore a hole, move aside and let the operator paint layout blue in the hole and then rerun the machine and it would come back and bore out the layout blue and not change the hole size. Even that was before CAD. When I serviced the Computers at Buick in the late 60's and early 70's, I saw how the tapes for those wonderful machines were made. The came off full sizedrawings on big sheets of aluminum, a TV camera that had a cross hair device and a big XY table that would hold the plan for the side of a car. Each point for the mill to use was located on the plan with the TV cross hairs and the XYreadoutof that coordinate was taken. All this information was stored on punch cards and they were then feed into a machine that punched the paper tape the milling machine read. They managed to make cars and planes and who knows what else using this method. Could we still do it that way, Of course we could. It's just that we have better tools at hand now and thank goodness we do. Iran across my old slide rule the other day. I need a refresher course in how to use it. Istill use my French curves for some work. and had I a lot of long strips of wood with different sandpapers on one side.


  12. #12
    Bigshark's Avatar
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    RE: Ribs for tapered wings


    ORIGINAL: Avaiojet

    Glue the LE, TE, to the two ribs.

    All the other ribs can be rectangles with no airfoil. They can actually be glued in place.

    Get a long sanding bar and have to it.

    The wing will be done before you can say 3D.


    Oh my god! That is so simple its brilliant! (and I'm ashamed to admit that I'd never have thought of it in a million tries......)
    When they outlaw flying model planes, I guess I'll be an outlaw.
    Randy M.

  13. #13

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    RE: Ribs for tapered wings

    Oh my god! That is so simple its brilliant! (and I'm ashamed to admit that I'd never have thought of it in a million tries......)
    Bigshark,

    Are you pulling my leg? I think you're pulling my leg.

    The only downside is the rib isn't 90 degrees on top. Works for any wing AND for adding fake ribs inbetween real ribs. As in this case.
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  14. #14
    Bigshark's Avatar
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    RE: Ribs for tapered wings

    I am absolutely 100% not pulling your leg. I would've fiddle-farted around with profili or modified each one individually by hand or not even have built that plane, before I'd have thought of contouring the ribs in place.


    Good looking Gee Bee by the way. I hope it flies as nice as it looks naked.....
    When they outlaw flying model planes, I guess I'll be an outlaw.
    Randy M.

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    RE: Ribs for tapered wings

    Bigshark,

    OK, I believe you.

    When I do a wing that way, I place one or two layers of masking tape on the end ribs. I also try not to get the sand paper on the outside ribs.

    Been doing it this way for years.
    Owner: CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder." cfcgraphics.com

  16. #16
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    RE: Ribs for tapered wings


    ORIGINAL: limeybob

    well, one way is to make a root and tip rib, sandwich wood for the ribs in between and sand away.
    Bob
    I've done this and it works quite well for a one off wing. You can cut the notches for the spars also and sand or cut them in with a razer saw.

    Ken

    Sent from my Dry-Erase-Board

  17. #17

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    RE: Ribs for tapered wings

    Here's what I do. I have some scraps of plastic laminate... formica if you want to call it that. I lay out the tip rib and the root rib on two pieces of this laminate. I then use sheet metal shears to 'rough' in the shape a bit and then go to my sander and sand them down to as perfect as I can make them. Rough cut your rib material oversize.

    Cut out any spar notches in the laminate parts which will help with aligning tip to root. Stack and align the tip and root patterns and drill a couple of alignment holes through them so you can clamp or pin the balsa in place.

    Now... the KEY to getting it right. Start at the root, (assuming the wing tapers to a smaller tip) and stack it all together. But, start your stack with the root rib, then the template, then all the rest of the ribs and then the tip template. Pin the whole group together. Clamp it in a vise and sand it down with your sanding block just until you hear it touch down on the laminate. It is a pretty loud difference. You can use a saw to cross cut down for your spar notches and clean out the bottoms after unclamping them all with an exacto.

    Why have the root rib outside of the template? Well, doing it this way leaves a fairly large angle on the tops of the ribs. Once you assemble the ribs to the spars, you'll need to sand it all down flat before doing any sheeting as the angles are just too great to get good glue joints. This reduction in size will make the root rib too small to match up to the tip rib of an inner section to a wing... (yes, please don't ask me how I know this but I really should just destroy that one wing outer and not be reminded anymore).

    You can do this faster than laying out and cutting/sizing each rib from plans. Having the whole group clamped together, lets you heavy hand it a bit instead of having to be so careful with individual pieces. To me, then only easier method would be if I owned a lazer cutter... and only then would I resort to CAD/CAM.
    Please, no more cuts to education. We need to get Congress out of the third grade!

  18. #18

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    RE: Ribs for tapered wings

    I always cut the root and end rib from 1/8" lite plywood and sandwich the required number of ribs between the plywood patterns. Push 3 large T-pins through, placing one at the front, one in the center and one at the rear to hold the "stack" together. Using a Great Planes flat sander or similiar sanding bar I sand everything down to match the patterns. Once the wing is framed up it's a simple matter of running the sanding bar over the ribs to knock off the small amount of bevel on the rib outlines. Lots of scratch built projects have been framed in my shop in this manner and it's fast with the added bonus that should you ever need to rebuild a wing panel you have the patterns ready for use. Good luck on your build and have fun!

    Soft landings,

    Joe
    AMA 57750 Waco Brotherhood #114
    Nosen Cessna 310 Club #22

  19. #19

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    RE: Ribs for tapered wings

    Hi Green River RC- I belong to that club and need to visit, soon. My mother's mother was a Bickett from Raywick. She married a Ward who used to own the rock quarry on Calvary Road. Here is a method to make wing ribs. I rough cut the parts and threaded them onto rods then wing nutted them together. I had one central and the end ribs cut very accurately. Their edges were blacked with a Sharpie pen as a sanding indicator. Once these are sanded to satisfaction mark where you want spars to pass. The ribs are evenly spaced with the blue foam so multiples of this spacing will be easily figured when laying out wing. The blue foam makes it easier to see the taper. Use these ribs as templates to cut your actual model's wing ribs. This wing is for an Israel 'Redhead' and needs to built on rods suspended off the board. Yours, if a straight taper, can be built right on the board. Hope it makes sense.
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