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  • Model B ribs question(s)

    Greetings all! I'm building my templates that I will use to cut the rib blanks, and am cutting the templates all at once. I have Eric Newton's Bearhawk Builder's Manual for the wings, and have looked over his site pretty extensively. A few things I'd like to clarify...

    (1) All of the rib photos I see include a few extra holes that weren't placed on the Mylar drawing (#4 for Model B folks). For example, the very small (~3/16"?) holes in the upper right and lower left of this picture: http://www.mybearhawk.com/wings/centerib4.jpg

    I'm presuming those are placed on all ribs to help with alignment in the formblock. That seemingly presumes that the lightening holes are cut prior to forming the flanges, else one could simply use the 3/16" holes that center the lightening holes to hold the ribs in the formblock while forming the flanges. Is this assumption correct? If so, I'm assuming that, should I do it this way, the placement of the jig holes is not to any particular critical dimension, save that they (a) are consistent for all ribs of the same type, (b) are far enough apart that it helps with alignment, and (c) don't cause unusual stress concentrations (e.g., don't put one right on the edge of where a flange bend will be). I realize I'll only need one extra jig hole in the nose rib and aileron/flap ribs, since the drawing does have a fore/aft jig pin hole already.

    (2) Piggybacking on (1), what advantage is there to cutting the lightening holes prior to forming the flanges along the rib? Does this presume the router method of cutting the holes, and/or the press method for flanging the lightening holes? I ask because my current plan is to cut the lightening holes with a fly cutter, and to "Bob stick" the flanges for the lightening holes.

    (3) Everything I read seems to show folks flanging the two lightening holes on the nose ribs. My plans don't seem to indicate that this is required, if I'm reading them correctly. I'm okay with doing it, but wanted to make sure that this wasn't a change from the original 4-place to the Model B.

    (4) Eric's manual and website discuss "back ribs:" http://www.mybearhawk.com/wings/backribs2.jpg

    I'm presuming that they're referring to trailing edge at the wing root, which is seen in this picture on the end closest to the jeep: http://mybearhawk.com/wings/wingtrnsprt.jpg

    The Model B plans don't appear to have these ribs. Is my interpretation correct?

    Many thanks for any assistance!

    Nick
    4-Place Model 'B' Serial 1529B (with many years to go...)

  • #2
    I found it much faster to cut the ribs with the lightening holes then do all the forming. I actually cut the ribs 3 to 4 at a time.

    On the A model wings there is a jig pin hole in the leading edge of the nose ribs. This is used to align the ribs both for cutting and for riveting in place.

    Comment


    • #3
      Originally posted by nborer View Post
      Greetings all! I'm building my templates that I will use to cut the rib blanks, and am cutting the templates all at once. I have Eric Newton's Bearhawk Builder's Manual for the wings, and have looked over his site pretty extensively. A few things I'd like to clarify...

      (1) All of the rib photos I see include a few extra holes that weren't placed on the Mylar drawing (#4 for Model B folks). For example, the very small (~3/16"?) holes in the upper right and lower left of this picture: http://www.mybearhawk.com/wings/centerib4.jpg

      I'm presuming those are placed on all ribs to help with alignment in the formblock. That seemingly presumes that the lightening holes are cut prior to forming the flanges, else one could simply use the 3/16" holes that center the lightening holes to hold the ribs in the formblock while forming the flanges. Is this assumption correct? If so, I'm assuming that, should I do it this way, the placement of the jig holes is not to any particular critical dimension, save that they (a) are consistent for all ribs of the same type, (b) are far enough apart that it helps with alignment, and (c) don't cause unusual stress concentrations (e.g., don't put one right on the edge of where a flange bend will be). I realize I'll only need one extra jig hole in the nose rib and aileron/flap ribs, since the drawing does have a fore/aft jig pin hole already.

      (2) Piggybacking on (1), what advantage is there to cutting the lightening holes prior to forming the flanges along the rib? Does this presume the router method of cutting the holes, and/or the press method for flanging the lightening holes? I ask because my current plan is to cut the lightening holes with a fly cutter, and to "Bob stick" the flanges for the lightening holes.

      (3) Everything I read seems to show folks flanging the two lightening holes on the nose ribs. My plans don't seem to indicate that this is required, if I'm reading them correctly. I'm okay with doing it, but wanted to make sure that this wasn't a change from the original 4-place to the Model B.

      (4) Eric's manual and website discuss "back ribs:" http://www.mybearhawk.com/wings/backribs2.jpg

      I'm presuming that they're referring to trailing edge at the wing root, which is seen in this picture on the end closest to the jeep: http://mybearhawk.com/wings/wingtrnsprt.jpg

      The Model B plans don't appear to have these ribs. Is my interpretation correct?

      Many thanks for any assistance!

      Nick
      you are a man after my own heart...lots of questions...i love it...ill answer a few for you.....

      ill dive in ...any senior builders here please correct me if im not giving this fellow correct info..according to the Bearhawk way....

      I know you know this...but..... routers and fly cutters very dangerous...pls educate yourself on their safe operation if you choose that method



      question #2..from my experience...cut the rough rib out(bandsaw/snips)...router it out if you want with a form block to finished size...or cut it out with snips(more finishing to do but you can just use a cardboard template to trace your parts out on the sheet)..using a router gives you a better edges with less finish to do on the part..but you have to make wood templates for the router to follow...or use a fly cutter to make your holes(no template needed)..

      this video shows sonex ribs cut out with the all router method...but the concept is the same..the video does not discuss climbing cuts...desert bearhawk has a video on router usage and what the climbing cut on a router means...




      question #2.5..it depends how you are going to form your lightening hole flanges...if you are using a press then forming the hole flange first is easier with a flat rib to slide under the press...form your hole flange and then do the edge flange...if you are doing the bob stick method I dont think it matters what you do first...

      Chris from Milwaukee has a great rib party thread on here that shows his form blocks with cut outs to do the flange first on the press...maybe hell post a link if he sees this...or ill post it here when I come across it again...


      Last edited by way_up_north; 02-23-2019, 01:47 AM.

      Comment


      • #4
        As noted above, check out my post on rib cutting here:

        https://bearhawkforums.com/forum/bea...ng-a-rib-party

        Aside from the lightening holes, the only “critical” jig hole is the front one on the nose ribs. Those are used to align the leading edge so the nose skin is straight. If you read Eric’s manual, you’ll see that you can pass a string through it for alignment purposes. Also, Beartracks shows an alignment jig that Bob used when assembling the wing flag in the table top. Otherwise I placed my jig holes where I thought they were important for my forming process.

        Regarding the aft ribs, the flap on the non-B 4-place didn’t go all the way to the wing root. There’s a solid piece of wing between the root and where the flap starts. That’s what the aft ribs are for. The Patrol (and presumably the B, but I don’t have those plans) has flaps that go all the way to the root.

        The ribs that are made from .032” material don’t need the lightening holes flanged. All others are .025” and need to be flanged. I did my flanges before fluting the edges. Others have done it reverse of that. I cover my process here:

        https://bearhawkforums.com/forum/bea...-fluting-party

        Have fun either way!
        Christopher Owens
        Bearhawk 4-Place Scratch Built, Plans 991
        Bearhawk Patrol Scratch Built, Plans P313
        Germantown, Wisconsin, USA

        Comment


        • #5
          I made a set of ribs before aborting scratch building, and going with a kit. I flanged and fluted the edges then flanged the lightening hole using dies I made out of MDF. I don't describe my method as an industry best practice. The lightening hole flanging distortion from the lightening hole flanging took time to correct.

          I think Chris's video shows he flanged his lightening holes using a rubber press prior to flanging and fluting the edges. It looked to me like his banks were flat coming out fo the press. Impressive.....I thought that was ideal. There is also a video I think maybe fairchild posted that is also excellent.

          Cutting the lightening hole out of a flat blank seems like a big time savings as opposed to cutting them out from a three dimensional piece.
          Brooks Cone
          Southeast Michigan
          Patrol #303, Kit build

          Comment


          • #6
            If you’re on a budget ....Even thou everyone these days ....are using routers and power tools... you can still do the ribs old school and cut them out with snips ... using a cardboard template and marker(or use the magic washer against your rib former)...and pound them over with a mallet...fly cut the holes....then bob stick them...
            Last edited by way_up_north; 02-23-2019, 11:44 AM.

            Comment


            • #7
              Other folks have made similar recommendations. I’ve never been good enough with snips to make anything that wasn’t a crinkled mess afterward with raggedy edges. Ditto with the bob stick. I’ve never been able to make a bob stick that didn’t break when I used it. I personally found the power tool approach allows for absolute consistency and reproducibility. But that’s just my approach. Some folks find snips cathartic.
              Christopher Owens
              Bearhawk 4-Place Scratch Built, Plans 991
              Bearhawk Patrol Scratch Built, Plans P313
              Germantown, Wisconsin, USA

              Comment


              • #8
                Thanks all!

                Yes, I do ask a lot of questions... I hope that I can soon gather enough knowledge that I can start answering more than I ask. That may be a while!

                I think you have all convinced me to use the router method. I actually have a pretty nice router that I used all of a half-dozen times, and don't have a table for it. But, you inspired me to figure out how to incorporate a router table into my small shop, and still get light and hopefully some dust/chip collection. I had been shying away from the router because I didn't use it much, but after watching a few of the videos (thanks!), I think I'll give it a try. Besides, if I were to use the fly cutter I just bought, I'll need a new drill press... the cutter says no RPM over 250, and my little benchtop drill press can't go lower than 680. It seems that only the big stand-up models have enough pulley diameter to get down to that speed.

                I spent some time today finding a good spot for some additional jig holes for the formblocks and the router templates, since I'm now going to use the router to cut the lightening holes prior to forming the flanges on the formblock. If I can steal some time tomorrow, I'll make my router table and maybe start cutting the templates. My goal is to build all of the templates I need now, so I can switch the blade on my bandsaw to the metal-cutting blade I just purchased.

                I've been contemplating the bob stick for the lightening hole flanges because I don't currently have a press and a lathe. I suppose if I screw up enough flanges, I may change my tune. Who needs to keep cars in the garage?

                Thanks again!

                Nick
                4-Place Model 'B' Serial 1529B (with many years to go...)

                Comment


                • #9



                  Near the 2nd half of this video the builder shows how to router the ribs without a router table....but.....you have to keep the router flat to the surface...or you will put a groove into your rib template and your metal rib...

                  The router table makes messing up hard to do....but this can be done without a table if you are careful ......


                  Last edited by way_up_north; 02-23-2019, 11:58 PM.

                  Comment


                  • #10
                    You might consider a router circle jig for lightening holes over a fly cutter.
                    Brooks Cone
                    Southeast Michigan
                    Patrol #303, Kit build

                    Comment


                    • #11
                      Originally posted by Bcone1381 View Post
                      You might consider a router circle jig for lightening holes over a fly cutter.
                      Router circle jigs are nice for larger circles. Do you have any experience with small ones? Mine won’t go that small. Perhaps because it’s made for a larger router. There must be one for smaller, laminate type routers. Aside from fabbing your own fixture, I reckon.
                      Christopher Owens
                      Bearhawk 4-Place Scratch Built, Plans 991
                      Bearhawk Patrol Scratch Built, Plans P313
                      Germantown, Wisconsin, USA

                      Comment


                      • #12
                        Shop Woodworking Hand & Power Tools Collection on Lee Valley. Browse our selection of Reliable Tools for any Woodworking project.

                        This is the one that I used on my ribs. It goes from 1" to 7.5" The jig is installed in place of the router base plate.
                        Brooks Cone
                        Southeast Michigan
                        Patrol #303, Kit build

                        Comment


                        • nborer
                          nborer commented
                          Editing a comment
                          Thanks! Does this only work for plunge routers? I have a Porter Cable 690 series but only with the fixed base. Trying to figure out if I should just order jig or if I need to order a base as well.

                        • Bcone1381
                          Bcone1381 commented
                          Editing a comment
                          You'll need the plunge router base as well.

                        • nborer
                          nborer commented
                          Editing a comment
                          Thank you!

                      • #13
                        Very nice. Quite a bit different form factor from the one I have.
                        Christopher Owens
                        Bearhawk 4-Place Scratch Built, Plans 991
                        Bearhawk Patrol Scratch Built, Plans P313
                        Germantown, Wisconsin, USA

                        Comment


                        • #14
                          Originally posted by Chris In Milwaukee View Post
                          Very nice. Quite a bit different form factor from the one I have.
                          This thread has this tool featured in the build tips PDF..

                          https://bearhawkforums.com/forum/too...hawk-jigs-dies

                          This PDF is also a great trove of tips and techniques ROUTER METHODS FOR BEARHAWK.pdf
                          Attached Files

                          Comment


                          • nborer
                            nborer commented
                            Editing a comment
                            Looks like some reading for me tonight!

                        • #15
                          Anybody that completes a scratch built Bearhawk ...should be hired by Boeing or Airbus on the spot...you've mastered 3 completely different construction methods All metal wing, welded tube frame and fabric covering......its a PHD in aviation technologies...

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