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Saab 37 Viggen - Custom Wings 1:9 scale turbine
I started this short kit from Custom Wings a year or so ago, and couldn't find anyone else on-line making one, so thought I'd start this thread with the build in it.
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Australian vendor - HolkRC
https://www.holkrc.com.au/
This is the vendor I purchased the short kit from. As its intended for a turbine, I didn't buy the EDF intake ducts and saved a few dollars. It came with the laser cut parts and the canopy. No plans or documentation is supplied. |
https://cimg4.ibsrv.net/gimg/www.rcu...cd999c6df4.jpg
Kit as supplied, plus a sheet pack of 2.5mm balsa I purchased at the same time. |
3D jigsaw puzzle
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So its a two piece...
https://cimg3.ibsrv.net/gimg/www.rcu...ad1a10f2b5.jpg
Custom Wings design concept is a two piece, split down the middle. Makes a lot of sense for a low aspect ratio jet and saves on jigs. https://cimg4.ibsrv.net/gimg/www.rcu...a1aa24820c.jpg Engine cover on the bottom, intended for an EDF fitout. https://cimg5.ibsrv.net/gimg/www.rcu...6e872508c5.jpg https://cimg6.ibsrv.net/gimg/www.rcu...63c2a264e3.jpg https://cimg8.ibsrv.net/gimg/www.rcu...e7e822bd7e.jpg https://cimg9.ibsrv.net/gimg/www.rcu...138e90de2c.jpg Wings detach in-line with the forward canards. Note the undercarriage in inboard so assembly at the field should be easy |
Step 1 - Organise those parts
As this kit is a mirror image, there are two of every part. So in order to check if I have all the parts, and to put some order in the 3D jigsaw, I strongly recommend spending the time to sort it out into matching parts.
https://cimg1.ibsrv.net/gimg/www.rcu...3beef00b3b.jpg Play match the parts.... |
Find those missing parts
I did end up with a few missing parts following my organisation. But Kevin from HolkRC was really helpful in cutting out some fresh ones (after he searched his workshop floor!). The only 'pair' of parts I was missing was Frame 1, but they are really small so I'm not surprised they vanished.
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The old CoG question....
https://cimg1.ibsrv.net/gimg/www.rcu...f1c3e3933d.jpg
As provided by Custom Wings, the CoG is quite far forward, so a consideration when building and doing the install of components |
Let the gluing commence....
Due to its mirror split design, building on any flat surface is easy. It also helps keep the plane straight laterally.
However, as there are no reference plans, it’s difficult to determine if the plane is being built like a banana (i.e. nose and tail sagging). ** Recommendation to Custom Wings to provide a plan to lay the build on so that I have a reference to build from. ** I recommend laying down a piece of tracing or semi-transparent paper and making vertical lines where the frames sit. It was designed in metric, and found most frames are 80mm apart. Then trace the outline on the paper and flip it over to do the other side, and like magic you have a reference which should match the first side. https://cimg4.ibsrv.net/gimg/www.rcu...5fe7af3bef.jpg 1:48 plastic kit for reference. Doesn't really help at this stage though. |
Wing Spars
I recommend have the carbon spars handy when building the wings and installing them during the build. I was a bit impatient and found that the holes for the Carbon spars were too small, so had to remediate later.
I purchased a 1m length of 14mm Carbon wing tube (2mm thick) with a 16mm outer sleeve. The length was fine. Don’t put it all the way through or it will get in the way of the thrust tube. Lucky I had the wing tubes before assembly of the second half, it was much easier to enlarge the holes in the frames while the kit was still in pieces. |
Quick fit of the turbine
I have a Kingtech K-85 going into a sports jet so thought I’d give it a quick fit for size. It fits in fine, the only question is how far forward to put it, noting the fuel tank wants to be at the CoG. The tank in the picture is just a Dubro 3000cc for scale, probably not the ideal shape.
My thought is probably fitting a 100N in the future, and size it for that. Flight weight is alleged to be 7-10kg according to Custom Wings and they recommend a 80 – 120N turbine. However, the rate of development by the time I get to buy it, it will probably be the same size as my 85N unit! https://cimg8.ibsrv.net/gimg/www.rcu...5424835a60.jpg https://cimg9.ibsrv.net/gimg/www.rcu...5ed68b3d56.jpg |
First half finished
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Second half on the build
https://cimg8.ibsrv.net/gimg/www.rcu...dab74629da.jpg
It’s much easier when there is a handy reference. |
I have a whole plane now
Given space constraints in my workshop, the only sensible thing to do was to hang it from the roof.
Note this is six months of work up to here for me. I don’t build very fast and like to jump from project to project doing little bits on each. However I have sourced the undercarriage now, but that is a story to tell on another night. https://cimg6.ibsrv.net/gimg/www.rcu...e8376737ba.jpg https://cimg7.ibsrv.net/gimg/www.rcu...54365f4fec.jpg |
Great work. I emailed the maker about buying a kit sometime ago and they told me they were waiting for feedback, maybe you are that person. Btw Rc crafters makes a main gear set for the Viggen.
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That looks like a cool project! :) Will have to check them out... Good luck with your build!
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Quality work for sure. Pitty for us non builders their wish there was a highly detailed composite Viggen available.
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Originally Posted by F900
(Post 12716855)
Quality work for sure. Pitty for us non builders their wish there was a highly detailed composite Viggen available.
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Originally Posted by Bob_B
(Post 12716790)
Great work. I emailed the maker about buying a kit sometime ago and they told me they were waiting for feedback, maybe you are that person. Btw Rc crafters makes a main gear set for the Viggen.
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Bob - Who makes it? I'd interested to know more about it.
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F900 I sent a PM
Bob |
Originally Posted by rustyives
(Post 12716890)
Hi Bob, I've worked with Ed from RC Crafters to produce a Viggen set in 1:9 for this model. He has made a superb set for me which I received just last week. I plan to post about these retracts and the integration into the kit shortly. I wasn't aware of Custom Wings waiting for feedback, but I heard they were interested to how Ed's design fits into the kit.
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Find some Undercarriage
The internet led me to RcCrafters as they already had a 1:10 scale Viggen set on the web page.
https://rccrafters.com/# https://cimg9.ibsrv.net/gimg/www.rcu...25317a643e.png 1:10 scale set available from RcCrafters Contacting Ed via his email lead to discussion and subsequent development of a set of a 1:9 scale Viggen set. Initially I had to join the queue as Ed had a number of projects on at the time including a very impressive set for a B-58! Ed has been awesome in creating the design to meet both the scale look together with the constraints of the Viggen aircraft itself. He always seems to be one step ahead of any idea and I’m very pleased with the results he has produced. Makes me want to build another type of aircraft just to see another undercarriage design be developed by Ed, ha ha. |
Viggen wing constraints
Firstly, the Viggen has a very thin wing at the section where the undercarriage attaches. I have a conventional retract set for an Xcalibur which I just dropped in for a comparison. Note the wing thickness at this location is around 25mm. Whereas a standard top mounted actuator retract unit is much more and unable to work with this kit design.
https://cimg9.ibsrv.net/gimg/www.rcu...f119738d4b.jpg Retracts for an Xcalibur dropped in for comparison. https://cimg0.ibsrv.net/gimg/www.rcu...e3b68994ec.jpg Too tall for a top mounted retract unit https://cimg1.ibsrv.net/gimg/www.rcu...e317fda746.jpg About 35mm height on these units https://cimg3.ibsrv.net/gimg/www.rcu...7362b0568b.jpg The wing is 25mm maximum! |
Custom side mounted actuator for the Mains
Ed from RcCrafters developed an initial design using a custom side mounted actuator. He sent me the design for me to see if it fitted.
https://cimg0.ibsrv.net/gimg/www.rcu...c6b1efafcf.jpg RcCrafters - nose unit. Note the oleo support is on the starboard side on the Viggen. https://cimg1.ibsrv.net/gimg/www.rcu...e52f8d05b3.jpg RcCrafters - Left main unit initial design (retracted). Note the oleo support points forward, actuator is on the aft side. https://cimg4.ibsrv.net/gimg/www.rcu...5ff95dfc93.jpg RcCrafters - Left main unit initial design (extended). Note the oleo support points forward, actuator is on the aft side. |
Check Undercarriage fit for size on the Viggen
I used Ed’s initial design and 3D printed a set to try it out (much easier than Papier-mâché). The first question related to the strut lengths, to make sure the mains and nose lined up correctly so that the plane sits level on the ground. The Mains use a 65mm wheel and the Nose twin 50mm units with the final products from JP Hobby.
https://cimg2.ibsrv.net/gimg/www.rcu...543b488940.jpg 3D printed representations of RCcrafters inital design https://cimg3.ibsrv.net/gimg/www.rcu...b457858815.jpg Layout of the Mains and Nose units to check the relative strut lengths. All good. |
Custom Wings kit design issue with Mains
When putting the Mains up against the constructed kit, it shows the design did not accommodate the forward wheel of the mains when retracted into the fuselage. ** Custom Wings – recommend you move Frame 14 design forward to 13, and copy/past Frame 15 design to 14 (will result in extension of EDF engine access hatch by one frame too) **.
https://cimg6.ibsrv.net/gimg/www.rcu...b28350ad7b.png Issue with Mains retracting into Frame 14 https://cimg8.ibsrv.net/gimg/www.rcu...23d29c1bf8.jpg Clash with Frame 14 - Some work with the Dremel and some custom framing & formers are required.... |
Options behind the Mains in the Wing
However, there is plenty of space behind the Mains in the wing area, and I just happened to come across this video showing this superb set of mains for a 1:5 scale build.
So why not incorporate a back brace into this set, there is plenty of room in the wing and it should provide some really good support to the mains when loaded aft on landing. https://cimg0.ibsrv.net/gimg/www.rcu...7462f48a20.png Frame 14 cutaway to fit in the Mains. That's a K-85G2 represented in the background for turbine positioning setup. |
Mains now has an aft brace
Ed from RcCrafters was very accommodating with the addition of an aft brace. He sent me the STL files of his CAD design and I simply threw them on the printer (with supports) for a PLA print. Not particularly suited to a 3D print, but really handy to work out what fits.
https://cimg3.ibsrv.net/gimg/www.rcu...f0ea9f6ba0.jpg Quick 3D print from RcCrafters STL file of Ed's CAD design with the aft brace in place https://cimg4.ibsrv.net/gimg/www.rcu...77fb53d356.jpg Fits fine, just some minor optimisations before the final design |
Finalise the Mains - add alignment link
Ed finalised the design and started the build. He also added an ‘Alignment Link’ so that the undercarriage tandem wheel strut can self-align when not under load. This is both scale (per the photo) below and very handy to align the tandem wheel strut prior to retraction.
https://cimg0.ibsrv.net/gimg/www.rcu...e15c2798bb.jpg Ed sending me teaser shots of the mains assembled prior to attachment of the wheels. Note the alignment link has double spring design for easy centering adjustment. https://cimg1.ibsrv.net/gimg/www.rcu...3260b2408c.jpg Photo from the internet showing the layout of the Mains. Note the alignment link on the front which has been replicated in the RCcrafter's design. |
Undercarriage Completed :)
Ed’s completed design built ready to send, superb bit of kit! Ed says he made enough parts for 5 sets, so if anyone is interested in getting a set for this kit, get in fast with https://rccrafters.com/#
https://cimg0.ibsrv.net/gimg/www.rcu...0d235add27.jpg |
Dremel the wing and fit the Mains
Because of the design of Frame 14 mentioned earlier, together with the addition of the Aft Brace to the undercarriage, the Dremel had a bit of a workout. The photos below ONLY have material removed from the original Custom Wings design, I have not added any structure at this stage. It’s purely to show the modification I did to the kit to fit it in.
There have been no issues with the RcCrafters undercarriage, it fits in the wing fine. All this rework is around accommodating the kit design around this undercarriage. https://cimg2.ibsrv.net/gimg/www.rcu...6f097c8c87.jpg The kit structure I removed in order to fit in the undercarriage. 3D printed Mains included for reference aligned with their mounting location. https://cimg6.ibsrv.net/gimg/www.rcu...f3147fd365.jpg Installed RcCrafter's Viggen undercarriage. Now to build in the mounting and support structure. |
All up to date now…
This thread is now up to me in real time. My next stage is to build in the support structure to the undercarriage and get it working. Hopefully so I can clip the two sides of the airframe together and push it around the yard! Will keep you all posted with how I go… including the nose retract
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Hello, |
Hi Frank. The nose gear unit is 236g (123g without the retract unit), and the mains are 390g each all up. The complete set at 1:9 scale including custom undercarriage, Robart retract units, Robart retract controller, 6 x JP Hobby wheels, JP Hobby brake set (excluding shipping) was around the USD 1,500 mark to give an indication. Obviously costs are changing all the time at the moment, but it should give you a ball park number.
Nice work with your undercarriage design, they look really good, and I like the CAD work. That Einar Johnsson kit looks flash. Does it come with the undercarriage doors too? - I'm trying to work out the size of those at the moment from 3-view drawings as the Custom Wings kit doesn't provide any plans or reference material unfortunately. |
Thank you for the weight data. The height from the main landing gear of 30mm should not be exceeded.
The landing gear doors included in the kit can be seen in the first picture. There are several pictures of the landing gear doors. I used the 2D drawing as a guide....see pictures below. I have deposited two landing gear doors on the website of Thingiverse. https://www.thingiverse.com/thing:5351398 Regards Frank https://cimg8.ibsrv.net/gimg/www.rcu...9b930870f2.png https://cimg1.ibsrv.net/gimg/www.rcu...fa395d9e50.jpg |
Thanks Frank, much appreciated.
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Just glue it together already…
Ok, so I may have had the kit hanging from my ceiling while I was doing other projects and thinking way too much about the benefits of internal access having the two halves just clamped together. I eventually just got to the stage of saying ‘stuff it’ and glued them together anyway. So far I’d say it was the way to go and I should have done it months ago… the model is much stiffer; I can work on the centre section; I can align the other side and reference from it easier; and the nose gear is easier to install.
https://cimg7.ibsrv.net/gimg/www.rcu...5a11f9cf9d.jpg |
Install the undercarriage (about time!)
With some momentum on my side, I progressed the installation of the undercarriage. The nose was easy as it’s just a plywood plate for the retract to mount on. I put some packers under it and used tape to hold it in place at the maximum (downward) extension, as its easier to shorten packers than to ‘unshorten’.
https://cimg9.ibsrv.net/gimg/www.rcu...e0a645f204.jpg |
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