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Build Log
TMRC 2.9m Schweizer 2-32 beta build
Well, here I am in my new digs in Idaho, pleased as punch and ready to begin my beta build of the new Schweizer 2-32 sailplane from TMRC. This will be my fourth laser-cut partial kit from Tom Martin's fine line-up, and judging from the previous projects from TMRC, I am expecting the usual high quality and precision fit that makes a TMRC build so enjoyable.
The kit includes all of the laser-cut balsa and ply parts, two plan sheets, one for the fuselage and one for the wings and tails, and a nicely made vac-formed clear canopy. All of the sheet and strip stock and all of the hardware must be provided by the builder, but if you are like me you already have a good supply of materials on hand, and the stuff you may not have at the ready can be purchased as you go. I like partial kits. They allow me to choose my own hardware and adjunct bits, rather than having to settle on what is provided in the kit. They also provide me plenty of design latitude for doing things "my way", particularly when it comes to functionality and assembly sequence. I will try to identify areas where I may deviate from the plan, for personal preference or for design improvement where required. My first step for a project like this is to sit back and just stare at the plans for a good, long time. There are no instructions-- you are expected to know what steps need to be done and in what order. After about 30 minutes of absorbing what was before me, I began to develop an appreciation for the well-thought-out engineering that went into this model. Everything made implicit sense, and the design conformed to established conventions to a comforting degree. Tom is not only an accomplished CAD draftsman, he also knows how to construct a good airplane that is relatively easy to build and easy to assemble in the field. I can't see how this Schweizer won't fly as well as anything in its category. It has excellent scale fidelity (obviously drawn from the full-scale three-views), and it appears that it will come in at a quite acceptable weight. The chosen airfoil is the SD3021 section-- one of my favorites in this size-- and the nearly flat bottom with Phillips entry allows the ribs to be laid flat on the board without having to use tab feet. This is going to be an attractive model, and one that will fill a hole in my fleet as a small, compact scalie for light aerotow and winch, as well as sloping off of grassy hills. Let's get started! Onward! ImagesView all Images in thread
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Fuselage construction begins
The 2-32 is a shapely design, with a rounded fuselage cross-section. As a result, there is much strip planking to be done. I've always been of the opinion that the only way to ensure a straight fuselage with no twist or bow is to use a fuselage jig of some sort, to keep the formers in their proper location during the skinning operation. So, before beginning on the assembly, I headed out to the local hardware store to buy a nice, straight plank of wood for a jig board.
This will be used to set the formers in elevated location along the length of the board using stanchions to hold them in their assigned position. Once the skinning is done on the top and sides, the fuselage can then be removed from the jig board and the stanchions can be pried loose and discarded. At this point the fuselage shell will have adequate stability to remain straight and true, while the final planking is added to the underbelly. It takes a little longer than just trying to assemble the fuselage in free space, trying to keep everything aligned as you go, but it is well worth the added effort. ImagesView all Images in thread
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Looking forward to seeing this one.
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Also looking forward to this build!
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Out of the starting gate... with a bit of a snag...!
Well, I ran into my first problematic snag tonight when I went to lay out the keel members F19 and F20/F21. Turns out the parts are longer than what is shown on the plan, and the former slots don't line up. What to do now?
This is a common problem with a lot of die cut kits, where the die cutting is less than accurate and the plans paper has suffered some years of storage that allows them to shrink. I would expect a much closer match for laser-cut parts made from the same digital source as the CAD plans. My first suspicion was that the paper had shrunk a good deal, but there is a scale key shown on Sheet 1 that indicates the scale measures in feet. When I laid my ruler up to the hash marks, they aligned perfectly with the corresponding inches for a one-sixth scale drawing, where each 6 inch increment measures one inch on the plan. I can only conclude that a scaling error crept into the laser cutting files. Fortunately, the error is rather small, and can be accommodated by simply adjusting to the laser-cut slots. I will be flying the wood, not the plans, so I will let the wood dictate the actual dimensions during the build. To do this, I will re-do the hash marks on my jig board to conform to the actual position of the slots on the keel members. The important thing for a straight fuselage is that the formers must be dead-center on the jig board centerline, set at 90 degrees to the centerline, and the faces should all be normal to the board (or angled forward or back by some set amount where required). This will result in a fuselage that has no twist or bow, but in this case will be about a half inch longer than what is shown on the plans. I can live with that. This discrepancy also led to an examination of Sheet 2, where I found that the aileron 1/64" ply upper and lower capping sheets were also too long by some small amount. Again, let the wood dictate placement and disregard the plan. The rudder capping sheets were precisely correct, as were all of the wing ribs and tail feather ribs, with the exception of a few stabilator ribs that were too short by nearly a quarter of an inch. Here, I will keep the stabilator outlines shown on the plan and conform the ribs by adding small pieces of balsa stock. I don't know what to attribute these anomalies to, but I didn't see them as a show stopper in my progress. Maybe I am really "old school", but I have dealt with these sorts of dimensional adjustments many times in my years in the hobby, and in the end they will have no effect on the appearance or flight characteristics of the model. In my next session, I will pick up where I left off, after having made the necessary corrections to the plans and jig board. ImagesView all Images in thread
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Last edited by dgliderguy; May 27, 2021 at 12:28 AM.
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Following Don and good to see you're all moved into the new shop... it looks like a nice setup
I'll be following and taking notes already and have just cleaned up my shop and cleared of all tables so I can spread out a set of the 2-32 plans to mark up as you go... Tom |
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Racking up the formers...
I repositioned all the former stanchions on the jig board and got all the formers and keel parts racked up. Sighting down the fuselage gave me the reassurance that all of the formers are properly aligned and the keels are straight. From here on out I will be rechecking this to make sure nothing moves while I am adding the skins (planking and sheets), but it all seems pretty rigid and stable at this point, so I don't expect any issues.
Next up is to install all the longerons and stringer pieces along the length of the fuselage. From my past experience, I know I may be adding some intercostals between the stringers for more support where it is needed, to keep the skins from sagging between formers. The plans show 1/16" balsa skins, which will be nice and lightweight, but may be a bit too thin, at least in some areas. I'll keep an eye on this and see how it goes. ImagesView all Images in thread
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Don, I've added the angle gauges to the plan and cutfile, etched with the angle and corresponding fuselage station point bulkhead. Working on the previous and will update accordingly. Nice work!
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Fuselage ready for planking
I pre-sheeted the ply fuselage sides with 1/16" balsa sheet, which really helped in the installation of the delicate ply truss, to prevent breakage. Once done, the fuselage siding could be installed. I discovered that the laser-cut sides were too long, by a good half-inch, so in order to get a good fit, I cut off the last portion at the tail, from F13 back. This cut off portion will be installed later, once I am ready to install the stabilator to the aft end of the fuselage, with the excess length removed.
I also discovered that not all of the formers were the correct width, particularly former F11, which was too narrow by a quarter-inch per side. To allow for this, I sighted down the length of the fuselage and packed the daylight gap with balsa wood, until I was able to achieve a nice taper to the fuselage sides, with no "coke bottle" waisting. The idea is to fair the taper of the fuselage constantly and gradually toward the tail. I used balsa triangle stock in the joints between former and fuselage siding, to present more gluing area and fill any gaps. Once these erroneous former widths are corrected on the plan, this kind of "eyeball" fairing should not be necessary. The nose area required some sanding to get the stringers (F18, F23, F24) shaped to the desired contour. I also added some intercostals between the upper nose stringers where needed, to better support the balsa planking strips. With that, the fuselage was ready for planking (oh, boy!). Planking is a curse to some builders, in that each strip must be custom fitted for a good radial distribution around the circular cross-section of the fuselage. I consider it a challenge, but a rewarding and satisfying one, if you do it right. I have decided to use 3/32" balsa for my planking, rather than the specified 1/16", to ensure against the "starved horse" look that can result if the planking strips sag too much between formers. It will also provide a much stronger skin, for handling and overall durability. ImagesView all Images in thread
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Last edited by dgliderguy; Dec 30, 2021 at 05:54 PM.
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I thought it would be prudent to fabricate my battery tray before sheeting the nose, for better visual access. The ply tray slides into a slot up front, and will be screwed down to a transverse beam at the rear, so that it can be removed for battery pack installation and servicing. I also got the aft upper fuselage sheeted. Went quicker and easier that I expected. Next up will be sheeting the nose, and making up the canopy tray and canopy installation.
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Excellent work.
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Thanks, guys!
My canopy is cut and installed, now waiting for the RC56 glue to thoroughly dry before removing and filling the gaps. You will notice I cut the back part of the canopy away aft of bulkhead F6. I want to make a removable hatch aft of the canopy for access to the wing joiner area, for plugging in the aileron servos and for access to the rudder servo. I'm going with a pull-pull system for rudder actuation, and this bay seems like a good place for the servo. The hatch will be planked like the rest of the fuselage, and I may use rare-earth magnets to hold it down, rather than a latch release. We'll see. [EDIT-- Epic fail.. OH NO! I managed to introduce a large gap up front, so I tried to loosen the glue seam and re-align it, and the frame came apart. I will have to re-do the canopy install. One step forward, two back. I also got some thin CA on the canopy, a nice big run that will show forever more. After all these years of doing this, I should know better than to get thin CA anywhere near clear acetate, but there you have it. Repeat offender! I will try to polish it out with some Mirror Glaze, but I doubt it will ever look pristine. I deserve this visible scar as a witness to my hastiness.]. ImagesView all Images in thread
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Last edited by dgliderguy; Dec 28, 2021 at 04:21 PM.
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Doug lurking here.
I am attracted to this aircraft. When do you think the kit will be for sale? It's about time for some real balsa as I am getting frustrated with very thin epoxy. Your planking is truly beautiful. Thanks for doing this thread. I guess I am too lazy and too slow as well. One guy in our club painted his canopy with clear mat krylon. He did not like the looks of his pilot. Maybe he looked too frightened. |
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Last edited by rrcdoug; Dec 29, 2021 at 12:15 PM.
Reason: spelling
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Hi, Doug! Long time no hear....!
Tom Martin could answer this question better than I can. I expect that he will want me to finish the beta build first, to see if I can find any other corrections to the plans, before committing to more laser-cutting. I do like the way his designs go together. This one and the 1-26E require a lot of planking, but it goes quickly, and it sure does make for a nice, light, but strong fuselage! I agree with you about all-wood structure. Fiberglass is pretty, no doubt about it, and lightweight too, if the lay-ups are done correctly, but there is just something about wood that turns me on. It can take a thrashing on a crossed-up landing, and even if it fails here and there, the repair can usually be done with just some glue. I guess I'm just an incorrigible old woodie fan at heart. |
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