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1:3.5 Slingsby Sedbergh T21b Build (Chris Williams Design)

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  • 1:3.5 Slingsby Sedbergh T21b Build (Chris Williams Design)

    I've been an R/C modeler for 26+ years and most of that time was building .40-.60 size sport kits with a few ARF's and a couple of scratch builds. About 6 years ago I flew my first glider, the Radian, and was immediately hooked on soaring. The Radian led to a Skybench Oly II and then I started a Skybench Skybird (that I still haven't completed). About that time I saw some of Chris Williams videos on Youtube and really wanted a big scale sailplane and Traplet had several of his plans. Something about the T21 drew me to it though, maybe the side-by-side seating, the open cockpit, or the fact that it was a military training aircraft, and I'm a Veteran of the USAF. And it was a bit simpler than the other, beautiful gull-winged birds. So I purchased the plans. Unfortunately things at work, and politics in our club, weren't good at that time so I took a break. In an effort to save money and prepare for job-searching if it came to that (which fortunately it did not), I sold my truck and kept my motorcycle. I was also an apartment dweller which meant building a big scale glider would have been difficult to say the least.

    Eventually things got much better for me at work. I got a different position with much less stress - in fact now I get really bored! I bought a house (my first) and last year I bought a used Dodge Caravan. I converted one spare bedroom into my workshop. I made a few false starts on some other R/C projects (most notably a 1:6 Fairey Firefly) and built some model rockets for about nine months, but I recently got the bug to build my big glider finally.

    Marc Beaupre at www.scalesailplanekits.com had the cut files to laser cut a short kit for me. I contacted him in July and the first part of August I had my kit.

    I work a week on, week off, out of state, so my builds happen in starts and stops. I started this back around the 8th of August, but wanted to have a fair amount of progress before I started any kind of a build thread, but here it goes. I'll start with separate posts to get to where I am at this point.


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    I prefer the Silver with Yellow banding over the slightly more common Red and White Air Cadets scheme.
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  • #2
    Marc did a very good job of laser cutting my kit and was very kind in adding a sheet of laser cut gussets so that I wouldn't have to cut them by hand later.
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    My bench is 9' along one wall and 6' along the other. I've got about 18" to spare! I also build using a magnetic jig system. My original was one offered by Great Planes, but I upgraded to the one produced and sold at www.airfieldmodels.com. I really like building this way.
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    • #3
      I started with the Horizontal Stab, building it vertically from the trailing edge first.
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      Then, once the leading edge was on, I could lay it down to add the top and bottom leading edge sheeting, cross bracing, cap strips and gussets.
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      • #4
        Next were the Elevators. The Trailing Edges are laser cut 1/16" Ply faced with 1/8" Balsa either side so it can be sanded to the proper taper later. The ribs are simply triangles of 1/8" Balsa cut oversize and then sanded to shape. I notched the ribs to accept the ply trailing edge on my band saw. Again, I started the build of the Elevators vertically on the Leading Edge.
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        The plan design for the Elevator Joiner/Actuator is a music wire pin attached to a plate that gets glued to the backside of the Leading Edge. I went a slightly different route, borrowing from something I saw done elsewhere here on the Forums (I don't recall at the moment who it was though, sorry). I used square brass tubing and a piece of sheet brass soldered to it, that was then epoxied to the leading edge.
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        • #5
          95% completed Horizontal Stab and Elevators. Only locating it properly on the Fuselage, as well as finalizing the hinging (Robart 3/16" Pin Hinges) remains. And in this image the tips had not yet been sanded to final shape... They are done now also.
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          • #6
            Then I moved on to the Rudder, which is built in the same exact manner as the Elevators.
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            I had just a bit of warp in the Trailing Edge, so the vertical jigs are holding it in alignment as I glued the Ribs into place. I also notched the ribs on the band saw.
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            Oddly, the plans do not include rib templates for the upper/forward balance tab portion of the Rudder. I'll wait to finish the Rudder after I've built the Fuselage that includes the Fin so I can extrapolate the remaining portion from the Fin.
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            I used various sanding implements - rifling files and emory boards - to make the requisite relief cuts for the gussets.
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            • #7
              Just looking at the 1:1 Sedbergh the nose moment looks rather short compared to the tail moment which suggests it'll require quite a bit of additional weight to get it to balance properly, and that is supported by the remarks of Chris Williams and others who have built this model. With that in mind, and the fact that the cockpit is open and quite visible, I thought I would attempt to build an animated cockpit to include the Rudder Pedals and Pilot and Copilot Sticks. The world-wide-web has helped quite a bit in providing detail images, but for details I couldn't find, I found a gentleman on Facebook who restored one in the UK and he's been a blessing. He's given me some photos and even better some PDF's of the aircraft manual! With what I had, I set about to build the Rudder Pedals first, drawing out a working plan.
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              They're not complete yet, but I think they're right on target. I still need to shorten the vertical length a little below the pedal crossbar, then add a tang to the innermost pedals near the centerline to attach the actuating cable and bungee, then prime and paint.
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              • #8
                Now I'm off until Wednesday afternoon when I have to drive back to work for a week, and I'm building the Fuselage sides. At this point it's pretty basic stick construction; Spruce Longerons, Spruce Verticals from the front to about the CG, then Balsa Verticals to the tail. I built one side first, then the second on top of it. Once the glue has set up, I'll remove them from the board and complete them separately into left and right sides with the required gussets and plywood doublers. The forward section gets skinned with thin plywood also, but I think I'm going to add that after I've set the curve dictated by the formers.
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                • #9
                  Subscribed! Will be following with great interest. My good long time friend Gino had one up in PGC PA which I got to fly a few times, including winch launch back in the late 80's & 90's. I love this glider so much that I designed one back in 1988. Though it was ~1/6 scale, I flew it for 20 years. First ten years off a high start and the last 10 was aero tow. I done it in his red / white color scheme and retired the model, which he has hanging in a room in his house for almost 10 years now.

                  in the back of my mind I would too like a 1/3 scale model of this someday.

                  nice work so far, something to look forward to this fall / winter on your project.

                  gunny

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                  • Tango Juliet
                    Tango Juliet commented
                    Editing a comment
                    Thanks for following Gunny. I've flown in a lot of different kinds of aircraft, but never a glider. It's on my bucket list. I'm hoping this turns out to be a good thermal hunter like I've read about the 1:1. In two weeks I'll be at the NARCA Aerotow near Huntsville to ask a lot of questions and take a lot of photos.

                • #10
                  Nice stuff, waiting for next installment!

                  Jeremy and Ben
                  SCCAAA TT TN

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                  • Tango Juliet
                    Tango Juliet commented
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                    Welcome aboard. Give me a few days and I'll have something more to add.

                • #11
                  Amazing stuff! Thanks so much for sharing!
                  Team JR Air ............You can't buy happiness. But, you can buy a sailplane and that's pretty darn close.

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                  • Tango Juliet
                    Tango Juliet commented
                    Editing a comment
                    Welcome. Thank you. I'm glad you like it so far.

                • #12
                  All right! I'm glad to see you have started your build. The elevator horn set up is 'pin and fork'? The 'pin' drops into the 'fork' or slot on end of push rod? I think Art had this on his Cherokee thread or maybe Dion had it on his(?)

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                  • Tango Juliet
                    Tango Juliet commented
                    Editing a comment
                    Thanks. Yeah, I think it was on Art's Cherokee build that I saw it. CW's design is essentially the same, I just think this is a little more robust (and of course it's also heavier, which is NOT better, but oh well).

                • #13
                  Next time you could probably do something similar with music/piano wire in lieu of the brass parts. Bend some wire to epoxy/fit each elevator then solder the 'pin' ends side by side. Leave one shorter than the other. The longer one is the 'pin' to go into the 'fork' which has a hole to receive the 'pin'.

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                  • Tango Juliet
                    Tango Juliet commented
                    Editing a comment
                    I'll save that for the next big sailplane.

                • #14
                  Today is my last day off and also my "travel" day to go back to work. I live in Mobile, AL, and work in Houma, LA, so I usually leave town about 1PM. My work day starts at 05:00 tomorrow morning. 12 hour days for seven days. I'll get home next Wednesday evening, then the next morning I'll be heading up to the NARCA Aero-tow near Huntsville for four days, so I won't get a lot of shop time on my next week off.

                  And speaking of shop time... I spent quite a bit of time in the shop this week, but for all the time I spent, I don't feel like I got a whole lot accomplished. On the plans, all of the formers are built up, being faced with 1/32" plywood and outlined with 1/4" square Spruce, but the laser-cut short kit comes with 1/8" Plywood formers. Four of the six formers fall ahead of the CG so the plywood formers are good because they're heavier. But for F4 it's a bit of a problem. It could sit in front of, or behind the Spruce vertical member of the fuselage side, but it should really be in line with it. It's also the former that makes up the rear of the open cockpit, so I decided to build up F4 as per the plan.
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                  I wasn't able to start joining the fuselage sides yet because I was short on my plywood sheeting for the nose section for the right side and had to order more. If it weren't for that I'd almost be ready to start joining fuse sides.

                  I also started to make my movable control sticks. They still have a ways to go to be complete, but just this little bit of work took several hours.
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                  I also need to order some itty-bitty hardware to assemble these.

                  Well, that's all I've got to show now for a few weeks. Stay tuned for future updates.
                  Last edited by Tango Juliet; 09-27-2017, 09:54 PM.
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                  • Cliff Evans
                    Cliff Evans commented
                    Editing a comment
                    Having built two of versions of this glder from this plan I can say that F4 is better as a solid rather than built up. It looks like you are trying to keep this aircraft light. DON'T it needs the weight as it is a very draggy airframe. The plan states the the all up finished wieght shouls be around 22Lbs, the first one I built came out at exactly 22Lbs, it flew very well. The scond however came out at 26Lbs and flew far better than the first. It had much better penetration and handles so much more like the full size which, I leart to fly in in 1978. If you can get it at around the 25/26Lb target you will not go far wrong.

                  • Tango Juliet
                    Tango Juliet commented
                    Editing a comment
                    I'm not as worried about F4 now as much as I am F5 and F6. I've noticed that there's not much "meat" to those two formers, yet they are the ones that carry the wing once attached to the fuse. Thank you for the insight though, I'll keep it in mind.

                • #15
                  It's always good to have a break in a project, time to solve issues in one's head as the build evolves!
                  Looking forward to meeting you in Huntsville next week.

                  Jeremy and ben
                  SCCAAA TT TN

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                  • Tango Juliet
                    Tango Juliet commented
                    Editing a comment
                    Likewise.
                    Too much time away from a project can sometimes mean doom for me though as I start thinking about other things I want to do, or I imagine the project I'm working on getting too complicated and I shelve it for "someday". I'm really trying to maintain my focus now and make sure I build this to completion. I think NARCA will help immensely in keeping me motivated.

                  • JimD
                    JimD commented
                    Editing a comment
                    I am enjoying your build, will be watching with great interest!
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