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Q for those using router method for cutting rib blanks---

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  • Q for those using router method for cutting rib blanks---

    I have made 3/4 MDF plates to sandwitch my rib blanks in between. The plates bolt together to apply compression while the router bit does the edge cuts.
    I installed steel bushing into the bolt holes in the MDF. The bushings are made from steel brake tubing. When I put the bolts through-- there is still a tiny bit of
    relative movement between the MDF plates. (maybe 3 to 6/1000 inch-) This tiny bit of slack seems to allow the router bit to shave a very thin skim off whichever
    MDF plate is NOT in contact with the pilot bearing. I am concerned that this will eat down the perimeter of one of the plates. Wondering what the best solution here is-

    1-st solution------ sand down the outer edge of one of the plates slightly deeper than the amount of the slack- so the bit cant touch it. This means that the pilot bearing
    con only be used on the bigger plate--- not on either plate interchangeably anymore.

    2-nd solution----- when I first started project-- i had some surplus 1/4 OD chrome-molly tubing. It had a slightly thicker wall than the brake tubing. I had to file the ID
    of the chrome -molly to get the bolts to pass through. The brake tubing had about 3 or 4 1/1000 slack as is. I could order more chrome-molly and replace the
    brake line bushed with tighter fitting Cro-Mo and maybe eliminate the excess slack.

    Only drawback to solution 1------ cant use either MDF piece to guide on as one will be correct and other will be undersized for clearance. I could paint one green and one red
    to not confuse which one to guide off of.

    does anyone who has all ready done this see any drawbacks to just cutting one of the MDF pieces undersize ? There is no left or right ( yet) when cutting the blanks.
    on left or right till holes flanged and edges bent.

    Seems like solution 1 will be simpler if it wont cause any problems down stream that I cant now see........ But I COULD do solution 2 if I needed to ....just have to order tubing...

    Any wisdom shared will be consumed like a hot T-Bone steak ! (dang-- Im hungry now...)

    Thanks- Tim B.



  • #2
    It’s honestly not worth worrying about. If you were making hundreds of ribs, it might be different. But given the volume, I wouldn’t sweat it. You’re not cutting enough pieces for it to make a difference.

    This posts shows all of my ribs stacked up:

    BBQ ribs are great, but wing ribs are pretty cool, too. http://images.tapatalk-cdn.com/15/12/05/d3428b6c9b82131199d7085d5e61be25.jpg Getting the aft ribs


    ~Chris
    Christopher Owens
    Bearhawk 4-Place Scratch Built, Plans 991
    Bearhawk Patrol Scratch Built, Plans P313
    Germantown, Wisconsin, USA

    Comment


    • #3
      To add to what Chris said, I stacked my rib blanks 3 at a time on my MFD pattern. I located the blanks with 2 jig pins and only had a 1/4 plywood sheet to cover the blanks as I cut them with my router. I did clamp the ribs and pattern to the bench and I used a hand held router. Worked great. The one think I was careful about was to always use a climbing cut, one where the bit it pulling into the work.

      Comment


      • #4
        You could mark one side of the router templates as the master so that is the same template that the router bearing runs against all the time. This way the master remains the same & the other side may get a little wear but this will give you consistent parts.

        S Lathrop is telling you the correct way to cut but the cut is not a climb cut. The router bit should undercut the material against the template to cut outwards so the bit pulls toward the template. On a climb cut the work is fed in the wrong way so the cutter wants to climb out of the cut & gets traction to violently run away. I used a router table & have a pair of big marker arrows on the table so I know the feed direction from either side of the table.
        Last edited by Glenn Patterson; 02-07-2018, 09:59 AM.

        Comment


        • #5
          Glen (and others-)
          My two MDF plates are both now identical and both made off the master template. So if I just cut one down about .015 with the sander so the router bit wont touch it---
          sounds like that will do it. AND paint them so I DONT guide off the wrong one..... Just want to remove the minimum to keep support for sheets.

          Chris--- if I accidentally let the router but shave off .010 off the block every time I cut a rib blank- I would be 1/4 inch too small by 25 ribs. Thats why I think I need to guide
          off only ONE and let the other one be a little undersize. It only has to be undersize by the amount of lateral slack I have. (have to measure that with the micrometer to see
          just how bad it is-- and how much I have to remove from the other block.)

          If I did the TIGHT cro-mo tubing - it might get so tight I would have trouble getting the bolts through........

          I dont have an up or down spiral bit. Im using a non-spiral type bit. 1/4 with a tip bearing. (will see how that works)

          Tim

          Comment


          • #6
            Originally posted by fairchild View Post
            Chris--- if I accidentally let the router but shave off .010 off the block every time I cut a rib blank- I would be 1/4 inch too small by 25 ribs. Thats why I think I need to guide
            off only ONE and let the other one be a little undersize. It only has to be undersize by the amount of lateral slack I have. (have to measure that with the micrometer to see
            just how bad it is-- and how much I have to remove from the other block.)
            Sure, makes sense. But I was cutting 10 at a time.
            Christopher Owens
            Bearhawk 4-Place Scratch Built, Plans 991
            Bearhawk Patrol Scratch Built, Plans P313
            Germantown, Wisconsin, USA

            Comment


            • #7
              If you are using a straight flush cut router bit with a bearing guide then you are good. I like the carbide half inch flush cut router bits. They seem to cut with authority. If you have a little variance it is very minor and when you hammer over the flanges then the hammer form governs the final shape. The tip of the nose ribs have to consistent as they define the leading edge.
              Last edited by Glenn Patterson; 02-07-2018, 02:57 PM.

              Comment


              • #8
                I tried a 1/2 inch carbide flush cutter --- it cut the aluminum smoothly and easily --- the only problem was it was too big to fit into the 2 little corners at the front of the nose rib
                at the semi-circular 1/8 radius relief cuts are. I went to a 1/4 one so it could make those little cuts. The bigger one would work for the rest of the perimeter but I guess Im too
                lazy to change bits.
                Chris---- wow--- Id be afraid to do 10 at once. I thought Id try 3 or 4 in a stack. -- since im just a beginner ! :-)

                I will sand down one of my plates tonight ! Thanks to all ! (again)

                Tim

                Comment


                • #9
                  OK-- tried sanding down the non-guiding router form block. Guided on the other one. I did a stack of 3 blanks. Seemed to work fine. Dont see how it could be any better----
                  I will try 4 next time- The 1/4 inch straight carbide bit seems to work fine ! Rockler brand.
                  When you make the ribs--- would you make an extra one on each side ? or just wait till you slip and mess one up later down the road and make a replacement when its needed ?
                  Now I gotta get more sheet metal !
                  Tim

                  Comment


                  • #10
                    Extras are always good! I made two extras of each, so I could have one extra for left and right.

                    Go as fast as you’re comfortable with. No race to win. You’ll get ‘er done!

                    As for the corners, I left the 1/4” radius in place as the relief. It’s a smooth transition, so I chose to use it as-is.
                    Christopher Owens
                    Bearhawk 4-Place Scratch Built, Plans 991
                    Bearhawk Patrol Scratch Built, Plans P313
                    Germantown, Wisconsin, USA

                    Comment


                    • Chris In Milwaukee
                      Chris In Milwaukee commented
                      Editing a comment
                      Wait, do I talk too much?

                    • Bdflies
                      Bdflies commented
                      Editing a comment
                      No Chris. I look forward to your every post!

                      Bill

                    • Chris In Milwaukee
                      Chris In Milwaukee commented
                      Editing a comment
                      It’s too bad there’s not a sarcasm font :-). In that case, I say we have a BBQ at Oshkosh. Say maybe Tuesday?

                  • #11
                    I attached a photo of the router template to illustrate what we did. The inside corners were finished with a chainsaw file. The chainsaw file cuts quick and we filed a half round cut into the rib where the flat metal & flange meet so the flange folds over clean. That way there no point for a stress to accumulate in the corner. We used the template as a visual file guide.
                    Attached Files

                    Comment


                    • #12
                      Glenn - I think your doing the same thing I am except im using a bit (1/4) that can go in that little "corner pocket" as I run the bit around the perimeter. Ill see if I can post a pic.
                      Tim

                      Comment


                      • #13
                        Tim you definitely get smaller corners with the smaller radius which makes it simpler. You may be doing as I am recommending. The thing is to get the half round notch where the flange ends and the flat tip begins where there will be an 1/8" radius with your bit. Clean out the radius and end that corner with a notch. It will take 2 seconds with a chain saw file to put the notches in. The flange folds over nice and clean. That detail may even be in the plans but it has been a while since we did the wings. I was having trouble finding a picture with the notch. There are some notches visible in this snipit from our log. We used chainsaw files a during our build to get nice round inside radius. They are a nice file to have around even if there is no chainsaw.
                        Attached Files

                        Comment


                        • #14
                          riba.JPGribh.JPGribe.jpgribb.JPGribf.JPG Thanks Glenn--- I looked at your pics--- BOY all those parts going together sure looks sexy ! I hope I get there one day !
                          here are some pics of my rib blanks cut with the router after I trimmed back one of the 2 router form blocks. You can see the 1/4 inch bit JUST fits into the 2 notches. you can also
                          se a pic of the 2 test ribs I made to see how the notches and the bend line interacts. Did yours look something like mine there ? Im guessing they look somewhat the same. ?
                          Also included is the punch I have been using to rough-out the central holes before I finish cut them with the router. I a making an air cylinder to power it using less effort- and so
                          I dont have to stand on one foot. It roughs out the hole without distorting the sheet any.
                          Your wings look great ! Very inspiring. !
                          Tim

                          Comment


                          • #15
                            Your ribs are first class. The 1/4" notches are perfect.. If that is your standard of craftsmanship then you will have a great set of wings. The air punch is a nice touch. We made all our ribs full length and adjusted lengths where required. My belt sander has flat sides so I clamped it in a workmate and used it like a vertical belt sander to take the rib to a line. That way there is no worry about getting the lengths & qty correct. If your ribs curl with the lightening holes then pry the lightening hole flanges both sides of the holes on the center line and they will flatten nicely.
                            Pay a lot of attention to square & straight. We built our wings in the stands with the 3/8" offset. The wings mounted and holes aligned perfectly. We left our holes at 3/16" then drilled them in situ and reamed the holes for the final bolt up. I am not going to get into a protracted discussion over assembling the wings no offset or no offset. There is enough information that a builder can go with the method that suits them. I have been responsible for decades for lot of industrial work that required precision to thousands of an inch over sometimes long distances using precision instruments. Best instrument for accuracy with a wing is fine weighted string lines. The parts fit true and square with the offset and does not require any jigs to locate ribs to compensate for the aligned mounting holes. It physically is impossible to get holes aligned and have the ribs square. The reference line through the ribs go to the reference lines on the spar and it forms a Z so it takes the 3/8" offset to be square. It is easier to check line, level and square is my only point. (http://www.mykitlog.com/users/displa...g=36225&row=38). We kept the spars level and had a fine fishing line with a 15lb weight run over blocks that kept the string 40MM off the spar web. We checked the line frequently and adjusted the supports under the rear spar to hold the assembly level. The space between spars is a quick check with a tape measure. The inspector came to inspect our wings and started to scare me. The wings were in their assembly frames and he was bent over looking through the end of the wings for a long time. Finally I had to ask if there was anything wrong. He said no that he was just taking it all in. I said that we built the wings straight. He agreed that it was straight. The jig pin holes looked like one hole through all the ribs.
                            look forward to seeing your progress.
                            Here is a couple snipits to help get you excited.
                            Attached Files

                            Comment

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