Announcement

Collapse
No announcement yet.

Graupner Cirrus X 3

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Graupner Cirrus X 3

    Click image for larger version

Name:	Cirrus01.jpg
Views:	1199
Size:	9.5 KB
ID:	10353

    I'm starting my summer build project. I hole up in the summer the way most people do in the winter. This summer I'm building not one but three Graupner Cirrus. Don't ask. The kits are very rare now but demand is still high. Luckily there are individuals making parts and pieces that allowed us to put together enough for three planes. By us, I mean, my friend Larry, his friend Terry and myself.

    Terry found rib kits in the UK and the original Graupner elevator bellcranks somewhere. Click image for larger version

Name:	640IMG_4267resize.jpg
Views:	1136
Size:	123.9 KB
ID:	10268
    Click image for larger version

Name:	640IMG_4268resize.jpg
Views:	1122
Size:	129.1 KB
ID:	10269



    Larry found fiberglass fuselages in Florida. Click image for larger version

Name:	640IMG_4272resize.jpg
Views:	1118
Size:	142.5 KB
ID:	10270



    Terry scored a complete kit that is in excellent condition and copied the plans for me. He is keeping the kit for his collection though. I scored a truckload of balsa at an auction last year so the wood is mostly covered.
    The plans I'm working from are for a 1/6th scale version of the Open Class Cirrus which make it a 3 meter wingspan. We also have the building instructions. Click image for larger version

Name:	640IMG_4266resize.jpg
Views:	1007
Size:	110.2 KB
ID:	10271



    The first challenge is to translate all the building notes on the plans. Luckily there are numbers on each note and translation to English in the book. Click image for larger version

Name:	640IMG_4276resize.jpg
Views:	976
Size:	117.4 KB
ID:	10272



    Next I had to figure out the dimensions of all the various pieces of wood. There is a list of all the parts by number in the building instructions with approximate dimensions but you still have to make some judgments. For instance converting 13/64" to a common size. All the dimensions are oddball sizes. Click image for larger version

Name:	640IMG_4277resize.jpg
Views:	978
Size:	149.4 KB
ID:	10273



    Once I got that done I realized that the trailing edge stock was not a standard trailing edge that anyone makes. So I scrounged around and found some that could be cut and then thickness sanded to work.
    My plane is going to have ailerons and a tow release so it's going to be more complicated and is the one I'll document here. Besides adding ailerons I will decrease the dihedral from 6 deg. to 3 deg. Which is what the full scale plane has I believe. I will also modify the ribs and wing tubes to accept a straight wing rod instead of the bent ones in the original kit. Click image for larger version

Name:	640IMG_4275resize.jpg
Views:	1010
Size:	91.4 KB
ID:	10274



    That's it for now gotta go get some flying in. The first wing panel is well underway and I'll be back with an update shortly.
    Last edited by ingrahal; 06-01-2016, 05:57 AM.

  • #2
    Nice! Thanks for sharing!
    Team PowerBox Systems Americas... If flying were the language of men, soaring would be its poetry.

    Comment


    • #3
      Update time.

      The wing is your typical D tube construction with a cap and web main spar and a diagonal false spar. Click image for larger version

Name:	640IMG_4264resize.jpg
Views:	1022
Size:	126.2 KB
ID:	10279


      Top and bottom sheeting forms the D tube and 3/16" of washout is incorporated into the trailing edge at the tip. The planform has a symmetrical taper of both leading and trailing edges from about 2/3 of the length out to the tip. Actually the entire wing tapers but the taper increases at about 2/3. Click image for larger version

Name:	640IMG_4256resize.jpg
Views:	970
Size:	128.7 KB
ID:	10277


      One interesting thing, at least to me, is the angle of the aileron spar. They angled it forward toward the main spar so that it intersects each rib at a constant height. So even though the wing tapers toward the tip the spar is not tapered. This allows you to glue the ribs in flush with the top of the spar and get the built-in washout in the wing. Some pretty thoughtful engineering. Click image for larger version

Name:	640IMG_4269resize.jpg
Views:	892
Size:	86.5 KB
ID:	10278


      The root rib is set to a -3 deg. because I'm taking out 3 deg. of dihedral. Click image for larger version

Name:	640IMG_4258resize.jpg
Views:	912
Size:	77.8 KB
ID:	10280


      I stacked and drilled the ribs for the servo wires. Click image for larger version

Name:	640IMG_4259resize.jpg
Views:	906
Size:	141.0 KB
ID:	10281


      I followed the plan for the aileron option which was on a separate sheet that had no text translations. I had to use a online translator to figure out what was going on. Once I got my head around it, it was pretty straight forward. Click image for larger version

Name:	640IMG_4260resize.jpg
Views:	916
Size:	90.8 KB
ID:	10282
      Click image for larger version

Name:	640IMG_4261resize.jpg
Views:	923
Size:	87.4 KB
ID:	10283


      Next I'll pull the wing panel off the board to trim the false leading edge and to set the wing tube sleeves. This will involve joining the wing to the fuselage to insure a good fit and proper dihedral. Click image for larger version

Name:	640IMG_4271resize.jpg
Views:	898
Size:	138.5 KB
ID:	10284
      Last edited by ingrahal; 06-01-2016, 04:03 AM.

      Comment


      • #4
        Very cool. I'll be following with interest.

        Comment


        • #5
          Hey Steve, hope all is well with you. Thanks for joining along.

          Thanks to you too Slappy. hope you enjoy the build.

          Comment


          • #6
            Update.

            Here I have drilled the fuselage and inserted the wing rod tubes. Then I mounted the wing and supported it for a nice flush fit to the fuselage and CA glued the tubes in the wing temporarily.
            Click image for larger version

Name:	640IMG_4280resize.jpg
Views:	873
Size:	133.7 KB
ID:	10306
            Click image for larger version

Name:	640IMG_4282resize.jpg
Views:	899
Size:	113.5 KB
ID:	10307

            Now with the tubes in place I epoxied them in after filling all voids with scrap wood. You have to get a little creative on the diagonal false spar.
            Click image for larger version

Name:	640IMG_4283resize.jpg
Views:	957
Size:	127.7 KB
ID:	10308

            All of the shear webs have been glued in and it's ready for the top sheeting.
            Click image for larger version

Name:	640IMG_4284resize.jpg
Views:	912
Size:	127.8 KB
ID:	10309

            Top sheeting glued in place with Titebond II.
            Click image for larger version

Name:	640IMG_4286resize.jpg
Views:	857
Size:	98.8 KB
ID:	10310

            That's it for now. Next will be the rest of the top sheeting and the leading edge. Then I'll tackle the aileron and spoiler.

            Comment


            • #7
              Nice! That Cirrus is a good looking sailplane!

              Comment


              • #8
                Art,
                Tell me when you're done and I'll ship my next project to you to build. Beautiful work, very clean and thought out.
                Len Buffinton
                Team Horizon Hobby

                Comment


                • #9
                  Hey Michael, I agree. Guess I should put a photo up so folks will know what I'm building.
                  Click image for larger version

Name:	Cirrus01.jpg
Views:	1140
Size:	9.5 KB
ID:	10346

                  Comment


                  • #10
                    Thanks Len!!! Well, Larry ropes me into these deals but I make sure I get an airplane out of the deal.

                    Comment


                    • #11
                      I got a little bit done today. The sheeting, leading edge and wing tip are all done.
                      Click image for larger version

Name:	640IMG_4290resize.jpg
Views:	921
Size:	121.1 KB
ID:	10349
                      Click image for larger version

Name:	640IMG_4291resize.jpg
Views:	879
Size:	123.9 KB
ID:	10350

                      Next are the spoiler and aileron.

                      Comment


                      • #12
                        Ok guys I need some advice. I haven't worked with the mechanical airbrake type spoilers before. What size would be appropriate for this sailplane (3 meter w.s.)? I have a set of Multiplex 350 mm spoilers and can use them if they will work. Also when installing how do I tell which is right and which is left? I don't see any indication on these.
                        Click image for larger version

Name:	640IMG_4292resize.jpg
Views:	915
Size:	139.0 KB
ID:	10352

                        Comment


                        • #13
                          I can't help with sizing, but the flat blade side is the front, the black arms are the rear. The mechanism typically points to the fuse.
                          In this picture the bottom spoiler is for the left side.
                          Len Buffinton
                          Team Horizon Hobby

                          Comment


                          • ingrahal
                            ingrahal commented
                            Editing a comment
                            Thanks Len!!!

                        • #14
                          Got the aileron made. This is a very custom made piece. I used my homemade thickness sander and some tapered stock along with a little creativity to mill the aileron. This minimized the hand sanding.
                          Click image for larger version

Name:	640IMG_4295resize.jpg
Views:	856
Size:	118.8 KB
ID:	10380 Click image for larger version

Name:	640IMG_4296resize.jpg
Views:	858
Size:	116.9 KB
ID:	10381

                          I'll be taking a break from this project to work on the DG 808S club plane. That shouldn't take too long though.

                          Comment


                          • #15
                            Ok I'm back on this project. I've been working on the right wing panel.

                            Both wing panels are done except for the spoilers.
                            Click image for larger version

Name:	640IMG_4380resize.jpg
Views:	837
Size:	143.1 KB
ID:	10987


                            I stuck the wings on the fuselage to see what the 3 deg. dihedral looks like. Looks good to me, just like the full scale. The original models had 6 deg. and looked a little odd to me.
                            Click image for larger version

Name:	640IMG_4381resize.jpg
Views:	864
Size:	161.2 KB
ID:	10988
                            Click image for larger version

Name:	640IMG_4381aresize.jpg
Views:	878
Size:	34.7 KB
ID:	10989

                            Next will be the spoilers.

                            Comment

                            Working...
                            X