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1:4 1928 RRG Professor

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  • #16
    Here are the wing rib patterns and center section balsa ribs. All the patterns have reference marks to locate spars. I have the CF wing tubes and sockets. They are 0.5" O.D. They will be doubled vertically between the spars. They will facilitate connecting the outer panels to the center section.

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    The elevator is an all moving 'pendulum' type. The mounting has to be robust and fluid with no slop. The stab will be built around a 0.25" CF tube pivot spar. The spar will be an interference fit in aluminum tubes within each stab half. This spar will be carried by a brass tube bushing in the fuselage. The tube ends were de-burred. The CF spar is removable for inspection. The elevator horn is built up from two micarta parts with balsa spacers. I drilled the large hole in each one first then fit them onto the brass bushing. Once satisfied with the fit they were cut to an 'L' shape on the band saw. The other two holes were drilled while the horn were stacked together on the bushing then they were sanded fair relative to each other. I epoxied balsa spacers between the two horns. The reason was I wanted the stab halves to not have any chance of becoming misaligned relative to each other. Probably overkill. I made two fuselage parts from 0.125" marine ply that carry the bushing. A pin from the horn will fit into tubes in the stab. This pin goes through an arc with elevator control input so I used the pin as a stylus via the horn to mark the masking tape on the ply. Then the arc slot was made using drills and small files. The pin will be epoxied in place, later. The pushrod end of the horn has a plastic bushing through which a small wire passes. The pushrod has a fiberglass tube on its end. The plastic bushing is an interference fit on its end. When these parts were assembled then the wire ends were epoxied to the horns.

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    • #17
      The fuselage construction has started. The forward 'bows' for the nose will be laminations of 1/16" balsa with CF tow epoxied between each lamination. The fuselage will get built inverted at first in order to make the 'basic box' to which everything else is attached. I used the side elevation on the plan to cut packing blocks to support the laminations at the proper heights. I cut the bows using patterns taken from the plan.
      This is fun stuff!

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      The first pair of laminations required a little 1/64" ply joiner. After this dried the first CF tow layer with another lamination of balsa was epoxied together. Two more layers to go! That's all for now!

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      • #18
        Making a great start Michael. If I don't stay focused on my own build you'll be finished before me!
        Member In Good Standing - "Builds Slower Than A Dead Turtle Nailed To A Fencepost" Club

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        • #19
          Great work on the stabilizer actuator Mike! I love your engineering!!

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          • ARUP
            ARUP commented
            Editing a comment
            Thanks, Pete!

        • #20
          Hi Michael, I'll be watching.

          Kevin

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          • ARUP
            ARUP commented
            Editing a comment
            Hi, Kevin! Glad you're here! How's the Weddell-Williams coming along? I haven't seen any posts lately on RCScalebuilder unless I'm just not very observant!

        • #21
          The forward bows are done so they were attached to the main longerons. A straight edge was used to keep things... straight! Cross members and diagonals were fitted. The lower portion of the fuse was done the same except the more forward cross members and diagonals are to be added later. This will, hopefully, allow the lower portion to be 'gracefully' curved according to the side elevation of the plans. Both fuselage 'crutches' were sanded as a pair.

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          The fuselage 'box' is getting built inverted. The upper crutch was put back onto the board. The stabilator mount section parts were fabricated and epoxied in place. A square and bubble level were used for alignment as the weights were placed. This has to be true in all axes or the model will fly crooked.

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          • #22
            Now that the rear of the fuselage box is built the lower crutch was added. BTW, medium balsa is being used to build the box. 1/64" ply was laminated onto the rear section of the longerons to help distribute stresses from the stabilator mount. The verticals' dimensions were obtained from the side elevation of plans, cut then glued in place. I use aliphatic wood glue. A straight edge holds the crutch straight as the verticals and diagonals are added. The rear section of the 'box' is done. Now I gotta get busy and build the front section! This has been fun!!!

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            That's all for now!

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            • #23
              Here's a pic of how the 1/64" ply is used as reinforcement. This is a spot where the longeron gets 'cracked' for it is a transition from curved forward to dead straight aft. The forward portion is mostly complete as far as uprights and diagonals are concerned. Some gussets were used in lieu of the sticks because whole formers will be fabricated and inserted into the box. The lower crutch (upper in pictures) is a little short at the nose end so balsa will get laminated onto it and sanded fair. A small balsa block will be let into the nose and, it too, will be sanded fair. Ain't balsa great?

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              Later!

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              • Tango Juliet
                Tango Juliet commented
                Editing a comment
                Michael, is it possible to use a slightly larger photo (file size)? The images in your thread are a bit small to really see the details of what you're describing.

            • #24
              TJ, if I try to go larger then my ISP won't deal with it. I'll get the spinning 'activity wheel of death' at the top of the page and it will just sit there... spinning... spinning... spinning. Plus, I'm not very computer savvy to overcome the problem if it is a 'user' problem. If there is some detail of interest then ask away! Maybe I can explain better or get another picture. If I try to insert 'large' as opposed to 'medium' pictures then it won't work.

              Balsa was laminated onto the nose then sanded back fair. I had put the lower fuse crutch on 'short of the mark'. Here is the end result with measurements. Last picture shows inside of nose. The release will get let into it, next.

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              That's all for now!
              Last edited by ARUP; 11-13-2017, 01:33 PM. Reason: Tried to insert 'Large' vs 'Medium' pictures. It didn't work.

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              • Tango Juliet
                Tango Juliet commented
                Editing a comment
                Well that's too bad. I'll just have to live with it I guess. If there's something specific I'd like to see in more detail, I'll let you know. Proceed!

              • ARUP
                ARUP commented
                Editing a comment
                TJ and Kevin (Melkezedek), JimD contacted me to see about helping getting bigger pics put up. We're working on it! Can't make any promises, though.

            • #25
              Here are the pictures again. For some reason they got put into the post as 'IMG' thingies after trying to alter them at TJ's request. Now you know why I don't 'cotton' to computers. Just ask Jeremy and Tom... they will vouch for me!.

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              • #26
                The release has been getting attention! 3/32" music wire 'massaged' to the contour of the nose to make the hoop. The Dremel was used to roughen it up a bit so the epoxy can grab better then the forward portion painted. The second picture shows the parts 'dry fitted'. A ply plate was fitted into the nose. It has CF tow epoxied to its lower surface. The hoop was epoxied in place next and the CF tow was wrapped over the hoop's legs. Another ply plate fits between the hoop's legs to hold the CF as the epoxy cures. All of this, along with the CF laminated into the nose bows, should be plenty stout for towing duties.

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                In the first picture is the release pin partially completed. It will fit into the brass tube which will get let into some ply. The pin will be articulated. I hammered one end flat and drilled a hole to fit a link from the servo. This has been done on previous models and works very nice without binding.

                Comment


                • Tango Juliet
                  Tango Juliet commented
                  Editing a comment
                  Either you're really moving pretty quickly on this build, or I'm moving really slowly on mine. I fear the latter. Great work so far!

                • ARUP
                  ARUP commented
                  Editing a comment
                  TJ, I move along pretty good but get slowed down, too. This build has been 'brewing' in my brain for a couple of years so I pretty much have the virtual build done! Fleshing it out is fun! Have yours ready for Horizon 2018!

              • #27
                Very nice work Michael! Bill

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                • ARUP
                  ARUP commented
                  Editing a comment
                  Hi Bill! Thanks very much!

              • #28
                Originally posted by BStaley View Post
                Very nice work Michael! Bill
                I'll second that - impressive level of usual craftsmanship.

                Michael - we need to dig out your frame jigs - I want to build a bike too.

                Comment


                • ARUP
                  ARUP commented
                  Editing a comment
                  Thanks, Dion! So many projects so little time!

              • #29
                Now that the release hoop is in place it's time to get the release pin assembly fitted. A properly angled platform was built with 1/16" marine grade ply. A 1/4" ply plate was grooved to receive the release pin's guide tube. This plate was glued onto the platform. Next, the servo mount was fabricated. It can be accessed by reaching into the cockpit opening. I try to get this functioning smoothly before putting the external ply skin on the framework. All of these parts tie the nose structure together pretty well so there shouldn't be any problem with the release assembly letting go under less than perfect tow.

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                While the epoxy cures holding the servo in its mount some one piece ply fuselage formers with integrated pylons will get fabricated then let into the fuselage. Stay tuned!

                Comment


                • Tango Juliet
                  Tango Juliet commented
                  Editing a comment
                  What servo do you use for the tow release?

                • ARUP
                  ARUP commented
                  Editing a comment
                  TJ, I'm using the Hitec HS-625MG. I set it up so that the release is closed when the horn is toward the nose. When the transmitter release switch is thrown the servo will get a little time to 'ramp up' in torque before any real movement of the release pin occurs. The pin only has to travel about 7mm so an even lesser servo would probably be plenty!.

              • #30
                That is such a lovely structure Mike.
                Regarding the WW, in the summer I was busy with gobs of overtime. When fall came I began remodeling my home.Hopefully I will get back to the WW in the new year.

                Comment


                • ARUP
                  ARUP commented
                  Editing a comment
                  Kevin, I went back through your thread, too. Good luck with the remodel. I did my house a while back and did much of the work myself so I know firsthand what that can entail!
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