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Thread: Building a Scratch Built Cub

  1. #41
    stknrddr's Avatar
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    Project Update - Stabilizer Attachment to the Fuselage

    I'd like to share progress made attaching the stabilizer assembly to the fuselage.
    I built the stabilizer and elevators a while ago, so I'll begin with a quick review.

    IMG_0482.JPG
    A photo of the scratch built assemblies.
    Balanced elevators.

    DSCF3199.JPG
    We used some original parts to create the templates (fixtures) to make the stabilizers and elevators.
    Joe Norris (on this list) loaned us some parts. You'll notice the stabilizer in the photo is not balanced,
    so I simply made the stabilizer fixture to accommodate a balance elevator.

    d.JPG
    A photo of the stabilizer leading edge tube in the fixture.

    c.jpg
    Bending the heavy tube required making a bending fixture as shown.
    I inserted a coil spring into the tube, and using the cupped fixture, the tube bent nicely without kinking.
    Don't forget to remove the internal spring if you elect o do this.

    DSCF3435 - Copy.JPG
    A photo of Charlie welding up an elevator.


    e.jpg
    This is a length of hinge stock. We'll cut pieces off, and cut down the centerline to create
    hinges that kind of cup onto the elevator or stabilizer tubes.

    f.JPG
    When pieces of hinge stock are cut to length, they can be tack welded in place as shown.
    The cupped piece acts as an appropriate spacer for fabric and paint allowances.
    After final welding, oiliite bushings will be pressed in to obtain the final bushing diameter for 1/4" diameter pins.

    k.jpg
    The entire stabilizer and elevator assembly then gets placed onto the fuselage.
    I clamped tubing vertically to the stabilizer, from the floor up, to balance and "stabilize" the assembly
    where it needs to be located. This took a lot of time.

    13.jpg
    These brackets (saddles) need to be positioned carefully in place and tack welded.

    i.jpg
    I made and used this gage block to properly locate the stabilizer
    from the tail post prior to welding.

    h.jpg
    Using clamps and blocks to position the tail assembly just right.

    j.jpg
    Blocks and clamp on the front end. You'll notice that I am not using a jack screw. I'll use a trim tab on
    an elevator as I've seen others use. Again, I'm building a light sport plane (I think).

    l.jpg
    By the way, I used a set of trammel points to square up the stabilizer assembly
    to the fuselage. I located a center point on the fuselage about 4 or 5 feet ahead of the tail section,
    and trammed the tail feathers equal distance on both the left and right stabilizers.

    3.jpg
    I used a transfer punch first to locate the hole location in the fuselage tube.
    I then drilled a pilot hole, and ran a locating pin to ensure everything was aligned well,
    than I drilled the final hole diameter and added a bushing to the lower tube.
    Long bolts will eventually hold this assembly together.

    6.jpg
    This photo shows the stabilizer and elevators in place, with the vertical stabilizer and the rudder
    clamped in place. It turned out well.

    Thanks for looking.

    John
    Attached Images Attached Images
    Thanks tedwaltman1, marcusofcotton thanked for this post

  2. #42
    tedwaltman1's Avatar
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    Amazing. Very inspirational. Thank you for the pictures and detail explanations.

  3. #43
    WanaBNACub's Avatar
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    This is such an awesome project! Keep the pics coming, your an inspiration for my next build!

  4. #44
    stknrddr's Avatar
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    Lunch Time Aviation - Project Update

    It's lunch time which means a chance to post an update. Baggage Compartment Floor

    1.JPG
    My baggage compartment is basically to the plans, where
    I sheared and bent steel sheet for the rails, and positioned
    them onto the fuselage as shown using spring clamps.

    2.jpg
    The plans call for 0.032" thick mild steel (1025) sheet metal, while I used
    0.032" 4130 steel sheet. I dimensioned the pieces per plans, however I
    added a little return bend along the bottom edge to add a little
    more stiffness to the part. It's the little 1/8" or so bend I added
    as seen in the photo.

    3.jpg
    Here's a photo of the pieces welded in place.
    This is the area directly behind the rear seat.

    4.JPG
    This is better photo of how we welded up the parts.
    Charlie did a nice job welding the pieces.
    I used flange nuts riveted in place which will be used
    to hold the plywood, or composite floor sheet in place.

    5.jpg
    A photo of the underside of the floor rail with the
    flange nut riveted in place.

    6.JPG
    Here you see the rivets are countersunk onto the steel for a flat finish.
    Also shown here is how we welded the rail to the cross member
    for the rear seat. This is also a good photo of the additional bend
    along the bottom edge of the rail.

    7.JPG
    This is a rivet squeezer used to crimp the rivets. The distance between
    the jaws is adjustable to get the correct squeeze for a given rivet size.
    Also shown, is the counter sinking tool, to countersink the sheet metal.

    8.JPG
    A photo of a piece of scrap plywood in place just to see what it looks like.
    I have not decided what to do for the back of the baggage compartment.
    Maybe I'll install tabs to attach a similar plywood sheet, or install
    a canvas style back; or the lower half of the back may be plywood,
    while the upper half is canvas?
    Any thoughts and photos of options are appreciated.

    Thank you,
    John
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  5. #45

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    Good work!!

  6. #46
    stknrddr's Avatar
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    Builders Update - Scratch built Ribs Finished

    I finished building my ribs. Here are a couple of photos.
    IMG_1485.jpg

    IMG_1496.jpg
    It took me a long time to decide which style of rib to build. I made samples of different
    style ribs to learn which ribs were suitable for me to build. Due to the
    fact that I could make this style of rib with minimal shop tools,
    and at home, I decided on the single cap strip with intercostals. I basically
    fabricated and assembled all the parts using bulk materials.
    I also now have a new set of wing spars from Jay at Javron Inc. to keep my building.

    I will follow up with another post on the fabrication of these ribs in the near future.
    Thanks for looking,
    John
    Likes sophistical, jnorris, Larry G, akwing, wirsig liked this post

  7. #47
    tedwaltman1's Avatar
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    Those ribs look GREAT! How did you get the leading edge curve so nice (and consistent)?
    Thanks stknrddr thanked for this post

  8. #48
    jnorris's Avatar
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    Looks great John. Keep up the good work!!
    Joe

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  9. #49

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    Quote Originally Posted by stknrddr View Post
    Builders Update - Scratch built Ribs Finished

    I finished building my ribs. Here are a couple of photos.
    IMG_1485.jpg

    IMG_1496.jpg
    It took me a long time to decide which style of rib to build. I made samples of different
    style ribs to learn which ribs were suitable for me to build. Due to the
    fact that I could make this style of rib with minimal shop tools,
    and at home, I decided on the single cap strip with intercostals. I basically
    fabricated and assembled all the parts using bulk materials.
    I also now have a new set of wing spars from Jay at Javron Inc. to keep my building.

    I will follow up with another post on the fabrication of these ribs in the near future.
    Thanks for looking,
    John
    Hi,Stknrddr,I am a cub homebuilter in China,I want to know what is single cap strip?Could you show this material bya clearer picture?and tell me composition of aluminium alloy,2024-T3 or 6061T651?
    Likes mike mcs repair liked this post

  10. #50
    stknrddr's Avatar
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    To answer a couple of recent questions, I have the following to offer:

    1. Cap Strip Material used- I used cap strip material from Carlson Aircraft. According to their web site,
    the material is 6061-T6 aluminum. They provide both a "T" shape and an "L" shape, and I elected to use the "L" shape.
    They're web address is carlsonaircraft dot com.
    IMG_1565.JPG

    2. To create a consistent bend at the leading edge - I used a metal shrinker to bend the capstrip slightly into a curve.
    Place the cap strip into the jaws and squeeze, move the material accordingly, and shrink...
    I fabricated and used a continuous shape form to set the cap strip in to ensure the perimeter of the cap strip matched
    the entire profile of the form. Due to the stiffness of the cap strip material, the shrinker is needed to bend the material,
    as I found it to be very difficult to create a nice bend any other way.
    Mary at Carlson Aircraft advised me to use a shrinker, and I listened to her.
    IMG_4588.JPG
    I will follow up with additional posts on the entire rib building process.
    17.JPG

    Thank you for looking.
    john
    Thanks cubscout, Steve Pierce thanked for this post

  11. #51
    tedwaltman1's Avatar
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    Again, sincere congratulations for simply AWESOME fabrication work!
    Thanks stknrddr thanked for this post
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  12. #52
    Marty57's Avatar
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    The ribs are looking great! I recognize those basement pictures a few posts back ...... great work.
    Marty
    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com
    Thanks stknrddr thanked for this post
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  13. #53
    stknrddr's Avatar
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    Project Update - Fabricating my Scratch Built Ribs
    Step-By-Step Rib Building Process.

    IMG_1500.jpg
    Here's a photo of the final ribs.

    4.jpg
    Recall, that I am working with a building partner who is also scratch building
    a cub. I made a set of forms (template and die set) to experiment making a
    three piece hydro-formed rib which we pressed using a hydraulic press.
    Although the rib turned out very nice, I elected to build ribs using the single
    piece cap strip, and aluminum intercoastals (truss style), as I could more
    easily make these in my home shop with basic tools, and I liked the
    single piece rib.

    3.jpg
    The photo above shows our three piece stamped rib,
    my trussed rib, and an original Cub rib.

    6.JPG
    I drew the traditional USA35B cub rib profile, printed, and glued the print
    onto a smooth board (shelf board). I built both left (shown here) and right
    hand rib fixtures, as I am using the "L" shape cap strip material, so I wanted
    symmetry on each wing regarding the direction of the "L" in the ribs.

    9.jpg
    I then cut the rib profile from another shelf board and over layed it onto
    the print. I then cut a nailed the little blocks onto the board to locate the
    intercoastals. Here's a photo of the right hand rib form.

    15.JPG
    I bought 6061-T6 aluminum cap strip material from Carlson Aircraft (on the web).
    I elected to have Carlson machine the flange off at what would be the nose
    of the rib (they know where to cut it), so the material may be folded as shown for
    mail order delivery.

    16.JPG
    I used a metal shrinker to set the bends into the cap strips. Insert the material
    and squeeze to "set" the bend; keep moving along to bend where needed.
    Inexpensive shrinkers can be bought for non-industrial use.

    17.JPG
    Make sure the final rib fits nicely into the form. Cut the trailing
    end of the cap strips to final length. I over lapped the ends and
    married them together for a clean and tight fit.

    20.jpg
    Fabricating Intercoastals - I then sheared a bunch of aluminum to
    width, and cut pieces to the approximate required length. I then pressed
    a bead down the center of the part using a small arbor press. A friend of mine
    milled a slot into a piece of flat steel stock, and welded a piece of round
    stock onto a second piece of flat stock to fabricate a bead former. I
    did not have easy access to a roller style bead former, and this worked
    very well in my home shop.

    24.jpg
    I then bent flanges on the intercoastals as shown using a small bench top break.

    30.jpg
    Cut and sand parts to final shape. Place as shown into the fixture,
    mark and pre-drill the holes, then drill the final hole size, and add clecos as
    you go to hold everything in place.

    35.jpg
    Ensure the cap strip is always tight against the form when inserting
    the intercoastals, and make sure the intercoastals are tight against
    their form blocks to maintain consistency. Use clamps when needed.

    50.jpg
    Pop the rib out of the form, take the whole thing apart to de-burr all
    of the holes. Place it all back into the form for pre-assembly, again
    using clecos prior to riveting.

    54.jpg
    Pop the rib out of the form again, and replace a cleco with a rivet, and
    continue. You will notice that I drilled some holes in the wood form where
    the clecos extend into the form. This is done to allow the rib to set
    flat in the form when the clecos are in place. I used solid aluminum rivets
    and a rivet squeezer.

    47.jpg
    I fabricated all of the full length ribs first, then modified the form
    slightly to make the shorter ribs as shown.

    60.jpg
    Before I went too far, I wanted to make sure that the short ribs
    were matching up well enough, so I made a short sample of a
    false spar and placed it as shown. I was very happy to see
    how well everything fit up.

    80.jpg
    The final stacks of ribs. To reduce complexity and weight, and
    having the desire to build light, I will not have flaps, therefore
    I have more full length ribs than a cub with flaps has.

    I learned these processes by scouring the web, looking at kit plane designs,
    and from other builders on Supercub dot org. I hope others can
    benefit from my posts as well.

    Thank you for looking.

    John
    Thanks Fat Kid thanked for this post

  14. #54

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    Awesome,thank you for sharing!
    Thanks stknrddr thanked for this post

  15. #55
    tedwaltman1's Avatar
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    Hats off to you for the exceptional dedication and clearly outstanding craftsmanship!
    Thanks stknrddr thanked for this post

  16. #56
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by stknrddr View Post
    To answer a couple of recent questions, I have the following to offer:

    1. Cap Strip Material used- I used cap strip material from Carlson Aircraft. According to their web site,
    the material is 6061-T6 aluminum. They provide both a "T" shape and an "L" shape, and I elected to use the "L" shape.
    They're web address is carlsonaircraft dot com...
    john
    ah, thats probably where the backcountry gets their rib material is from? it's an L shape... but that website is not responding at the moment for me...

  17. #57

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    Quote Originally Posted by mike mcs repair View Post
    ah, thats probably where the backcountry gets their rib material is from? it's an L shape... but that website is not responding at the moment for me...
    I think this type cap strip more suitable,from Dokata

    IMG_4616.JPGIMG_4616.JPG
    Last edited by sageelite; 09-19-2017 at 07:10 PM.

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