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Old Dec 09, 2014, 02:21 PM
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Leif Thelin's Spiggen, a vintage pusher prop jet

I am about to embark on a build (or perhaps I should say rebuild) of Leif Thelin’s Spiggen. This is a pusher prop jet with a family resemblance to the Saab Viggen. The design was originally published in RC Modeler in May 1967. It was also published in a Swedish modelling magazine called Modellflygnytt in 1968 (see http://modellflygnytt.se/gamla/1968/MFN_1968-1.pdf). The first picture attached shows Leif with his original plane.

I say that this is a rebuild for me because I built one before in 1970. The second and third pictures are of that model. It flew, once. No it didn’t crash, it was just underpowered and didn’t fly very well. The difficulty was that it requires either an engine that will run in reverse, or a pusher prop. I couldn’t find a pusher prop in the right size so I chose to try and make the engine run in reverse. I don’t remember for sure which engine I used but it might have been a Supertigre 60. To make it run in reverse I unbolted the front housing and turned it 90 degrees. According to my calculations this would change the timing in such a way that it would run in reverse. Well it did run backwards, but never achieved full power.

I tried flying it from my club’s grass field but never could get up enough speed to get it to take off. So it sat for a while until an opportunity to try it on a paved runway presented itself. The club I belonged to at the time was the DCRC club in the Washington DC area. One of the members was Maynard Hill who is best known for his transatlantic flight, but Maynard also set several other records. In 1970 he enlisted several DCRC club members to assist in an attempt on both the speed and the altitude records. I signed up to help because the trials were going to take place at the Dahlgren naval air station in Virginia and they had a paved runway. As I remember it, Maynard did succeed in setting the altitude record but failed at the speed record. At the end of the day I set up my Spiggen and had a go at getting it to fly. It did take off but was clearly underpowered. It flew with a nose high attitude with the wings doing that characteristic delta wing wobble as if it was going to stall. I couldn’t get the nose down enough to build up any speed. In the end I landed it and called it a day. It never flew again and I no longer remember what happened to it when I finally moved away from the DC area.

So here it is 44 years later and I thought I would try again. My current club, the Sun Valley Fliers in Phoenix Arizona has a nice paved runway so there is no problem with getting up enough speed for takeoff. I also thought that I would make it electric. All of my current planes are electric powered and an electric motor will happily run in either direction. My choice of motor is a Hyperion HS4025-890. This is a largish 12 ounce motor that is intended for helicopters. I bought it because Hyperion is giving up on motors and it was available at a huge discount from All E RC. But the motor appears to be well built. It has a Kv of 890 which is high for a large motor but is just what I need to run a 9x6 or 9x7 three or four bladed prop at a high enough RPM to produce the power I need. The battery will be a 4S or 5S 4000 or 5000 mah LiPo.
I am really not sure how the balance is going to work out. Leif used a 60 size glow engine in the tail and balanced it with most of the radio gear being mounted under the foreplane and a nicad receiver battery all the way in the nose. His radio was an early digital system which was probably two or three times heavier than modern equipment. I plan on putting the flight battery under the foreplane, but my electric motor is lighter than a typical 60 size glow engine so I may end up nose heavy. If I have to I can put the flight battery further back, just in front of the landing gear, but that would make it difficult to access the battery. We shall see how it turns out.

Other modernizing changes are in the wing. Instead of separate elevators and ailerons I will use just elevens with one servo each. That lets me leave out all of the bellcranks, which are fiddly and prone to linkage slop.

I am a little bit worried about weight. Leif says to keep it under seven pounds. Seven pounds works out to a wing loading of 22 ounces per square foot, which is pretty good for a plane this size. At eight pounds it would be 25 ounces per square foot which is just tolerable. The design is all sheet and is pretty heavy by today’s standards. So I have ordered some light weight balsa and plan on doing lots of sanding. The sanding is especially important because Leif originally used metric sized wood. If you look at the Swedish magazine you can see that he used a lot of 2 mm wood. In the RCM plan that was translated to 3/32 of an inch which is actually about 1/64 of an inch too thick.

I have worked on the plan using TurboCad to clean it up. The results are attached as a zip file of PDF’s. This is my first try at cadifying an old plan so I hope it is good enough to be usable by others if they should fancy building a nearly 50 year old pusher jet design.
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Old Dec 09, 2014, 10:11 PM
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That's an interesting airplane! It's like he took the cranked delta Viggen and turned it inside out. I'll enjoy watching the (re) construction! I use TurboCAD too, so it will be doubly interesting.

Andy
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Old Dec 11, 2014, 09:57 AM
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CG missing from plans

It was pointed out to me that I omitted the CG from the plans. I have updated the original post with a revised set of the cadified plans that now show the CG. It is shown in Leif's original plans as being in a range of 3/4" to 1.5" in front of the point where the landing gear leg enters the wing.
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Old Dec 17, 2014, 05:07 PM
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Bo Edström, Sweden
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Jeff Bean,

I have some info on Spiggen. Some more articles and photos. The articles are in Swedish (I live in Sweden) so I need some time to translate it to English. Just be patient.

/Bo
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Old Dec 17, 2014, 06:16 PM
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Jeff, that's an interesting model. I'm looking forward to your build. Thanks for sharing.
John
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Old Dec 17, 2014, 11:49 PM
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Waiting for balsa order

The lightweight balsa I ordered has at last been shipped. Unfortunately it won't get here until the day before the family and I go away for Christmas, so there won't be much progress until around New Year's Day.

While I was waiting I cut out the ribs using some of the lighter pieces from my existing stock of wood. I also cut and grooved the hardwood landing gear mounts. When I went to Home Depot to find a small piece of hardwood to use for the mounts I had a choice of either red oak or poplar. The poplar was quite a bit lighter so I went with that.

I also found and purchased on eBay a copy of the original RC Modeler issue that had the Spiggen article. I have attached new scans of the article. These are a big improvement over the original scans I uploaded. Before, all I had to work with was a xerox copy of the article.
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Old Dec 17, 2014, 11:53 PM
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Magazine plan pages again

Looks like the RCGroups forum software reduces the quality of jpg files you post, so I have put them in a zip file and uploaded that too.
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Old Dec 17, 2014, 11:59 PM
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More info on Spiggen

Quote:
Originally Posted by bossee View Post
Jeff Bean,

I have some info on Spiggen. Some more articles and photos. The articles are in Swedish (I live in Sweden) so I need some time to translate it to English. Just be patient.

/Bo
Tack, Bo, I look forward to any more information you can provide. Sweden is a lovely country. I was there this last summer. I also lived in Stockholm for a few years when I was a toddler (my father worked in the US embassy) but my family left when I was four and I lost whatever Swedish I managed to pick up.
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Old Dec 18, 2014, 12:43 AM
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Bonner Digimite 8

I was flipping through the ads in the issue of RCM that has the Spiggen article and came across one for the Bonner Digimite radio. The eight channel version, which is what Leif used, had a list price of $615 in 1967. In today's dollars that is $4,356. I don't think that even the highest end radio systems today cost that much.

Weight was advertised at 25 ounces for the airborne system with four servos. Leif used five servos.
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Old Dec 20, 2014, 12:57 PM
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Bo Edström, Sweden
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Jeff Bean,

I have now sat down and gathered the information I had avaliable on Spiggen.
Sources are:
1. The Swedish magazine "Teknikens Värld", issues 27, December 1966 and "Teknik För Alla" 1, January 1967.
2. Swedish Model Flying Federation, SMFF, member Magazine "Modellflygnytt" issue 1 1968, issue 6 2011 and issue 6 2012.
3. Swedish book "Radioflygboken" 1973.

Sorry for any misspellings and such and any oddies in the translation from Swedish to English.
/Bo

The Swedish magazine "Teknikens Värld", issue 27 December 1966
In this magazine it was articles about the full scale Viggen at that time and they also heard of the radio controled model Spiggen and had an article about Spiggen.

The article in this issue about the full scale Viggen I have translated to English and is attached in PDF below.
What they wrote about Spiggen in this issue was:

Page 37:
Viggen in the air!
Is this spying? Before the Swedish Airforce has got its fighter and attack plane Viggen in the air has over Gothenburg been seen a glimpse of an almost exact replica.
During Viggen construction time some has been published to the world press.
We know that the great powers has full time staffs that monitor the worlds specialist press. A puzzle of pieces can lead to a "copy". Now it has been known that Washington has ordered drawings from the Gothenburger that has made the Viggen "copy".
The Americans has to wait however. The journal Teknikens Värld can as first magazine in the world present the plane that pinched the Swedish Airforce on maiden. Read our hobby pages!

Page 45 (hobby pages):
A world sensation: Viggen as a model
We present a flying sensation in the hobby world, a news that is close linked to the Swedish Airforce Viggen.
It is a radio controled model with Viggen as original and where the designer managed to place the engine at the rear. After 1 1/2 years of preparation and build the plane is now in the air.
The designer is an adman, Leif Thelin, from Kungälv.
The model is 1.4 meter long, weight is 3.2 kilogram and has a 10 cc engine of about 1 horsepower with pusher propeller. The plane is still in testing stage and more advanced performance tests has not been made yet. But the model has reached height of 1500 meter, the radio range in the air can be up to 3 kilometer and on the ground 700 meter.
Flying time is close to 20 minutes. The model is a copy of Viggen with many of it's characteristics. It is controlled by radio of a type that gives proportional servo throws against the sticks movements on the transmitter and has following functions:
ailerons, elevator, rudder, trimmable flaps on front wing, throttle, stearable nose wheel with brake and device for firing rockets.
It is built in conventional way and is covered with 2 millimeter balsa sheets.
It is also covered with a thin layer of epoxy and painted with a 2-component fuel resistent boat paint.
The intention was from the beginning to get a plane with the engine at the rear and that resemble a modern present-day plane. So far in RC models the most of the builders has paid attention to World War II models. Some time ago he got a telegram from from Washington where a paper wanted to publish his drawings of the plane. But he consider not the project ready and the paper has to wait. The same is for Teknikens Värld journal but as soon as Leif Thelin is ready we hope to present the drawings on this interesting model.
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Old Dec 20, 2014, 01:13 PM
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Bo Edström, Sweden
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The Swedish Magazine "Teknik För Alla" issue 1 January 1967

Page 32-33
Viggen flies in Gothenburg
The Swedish Airforce Viggen has just been ready with the first testplane.
In Gothenburg a Viggen is already flying, a model of the SAAB-plane, and the testflights is reported to proceed excellent.
Here we present Spiggen, as the model is named.

First flight with Viggen went very well.
The designer Leif Thelin from Kungälv was very satisfied with the planes behavior in the air. It should be noticed that Thelins Viggen is a model that is no more then a 10th as big as the real Viggen. It is a model construction in master class.
About at the same time the first testplane of the real type 37 Viggen is ready for approval at SAAB in Linköping the adman Leif Thelin from Kungälv has his radiocontroled model ready. He started to build his 1.4 meter long model at about a year ago. First two testmodels was made that was 2 1/2 smaller. With help of much snow it was soft landings and starts for each testplane. The final model had a thoroughly tested background already at maiden.
Leif Thelin has not used any drawings as a starting point for his model. He has used articles and sketches as base. The model is not a scale model.
To enhance the flight characteristics the fuselage has been made smaller compared to the wing area. Wingspan is 105 centimeter.
What primarily differentiates Spiggen, that Leif Thelin name is model, and 37 Viggen is of course the propulsion. On Spiggen it is a 10 cc Merco engine that spinns a four blade pusher prop. Viggen air intake is also missing on the model. Landing gear is not retractable on Spiggen, that is painted white, red and black.
The 3 kilogram Spiggen is built in balsa except engine bed, bulkheads and some reinforcments. Even the thin front wing and fin has ribs iside to keep the weight down. Cost of material is not more then 80 SEK.
The radio is more expensive, Leif Thelin has mounted a proportinal radion that has following functions: elevator, ailerons, rudder, trimable flaps on front wing, throttle, stearable nosewheel with electric brake. Spiggen can also fire rockets by radio control.
Spiggen is a fast airplane, close to 150 km/h. It is easy to manouver in the air and can be used for advanced flying.
If one look at the details it is some which differ from Airforce Viggen. Spiggen is painted white, black and red. If one forget about the color it is hard to distinguish it from the full scale plane.
That it is a model of the fighter jet from Sweden has Leif Thelin marked by using the emblem "Tre kronor" (Three crowns) on the fuselage.
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Old Dec 20, 2014, 01:24 PM
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Modellflygnytt (MFN) nr 1 1968
(Swedish Model Flying Federation, SMFF, member magazine)

SPIGGEN
Since SPIGGEN was first published for the public in Teknik För Alla January 1967 issue and then in american magazine RC MODELER May 1967 issue and also in other maganzines the avalanche was started with air shows and more publicity in the press.
For me that has all the time been busy with constructionsproblems and concentrated on how the plane would behave - if it would fly - was all the attention and the joy that the plane behaved over all expectations rather dazing. Normally the life at the hobby lamp is almost isolated. Hundreds of mails has also been received in a steady stream, mainly from US and Sweden but also from England, Canada, Switzerland and South Africa.
Most of them contain questions of technical nature but also about family and flightconditions. The letters from the nordic area has mostly contained a questioin if any Swedish magazine has or will publish drawings. Therfore it is fun that MFN want to publish them even if the model by now is not new. The prototype still exists.
Also it would be extra fun if this would help to contribute people to do own constructions. Remember what satisfaction some simple creation can give for the person that construct compared to more professional guys that must specialize in a narrow field.
Vi can make our creations as we like and be in center of all phases of construction, from first sketch to first test flight and not to forget all professions we try and "cheat" in.
Then the freedom to tumble in the sky with the creation or more seriously do testflights.
To remeber exactly when a creation start to take shape is rather hard to tell. It all hangs together, probably one can go very long back in time to find clues. One of the delights with trying to create flying vehicles for pleasure lies in the fact that a project grows unpretentious with no time limits. When the thought first appeared that it would be fun to have the engine placed at the rear as naturally as in the front I do not remeber.
The delta wing was however more immediately the solution. The final shape was developed during several versions. It is little difficult now in retrospect to try to point at the obstacles and try to analyze them. Much that was new and mysterious is now natural.

To start with the Delta had to high wing loading and other problems occured because of the nosebody required as compensation for engine weight in the rear. At some point I was thinking of redesing an ordinary multi plane, that is to place main wing at rear and stab at the front.
That way came the canard wing in the solution. It had a potentional to work good but was a little tricky to construct. Back to Delta again but with stab in the nose. My idea has many similarities with XB-70 and did not look amiss but was not quite convinsing since not a build took place. A hot summer day, a 1/2 year later, in the shadow with nothing to read drove me to a kiosk where I found a Flying Review. Here for the first time the mock up of Viggen was presented and since that day I have not had any problem to occupy myself.
Small sheet constructions and experiments with dragons in different shapes in the summer vaccation bereezes learned me a lot. A first sketch was made to determine space for the radio gear and weight in the plane. The first plane in scale 1:2 1/2 was soon ready. It was completely crappy. It flew as good as a tree root when wing loading increased.
Nr 2 flew but behaved strange sometimes. But it was not worse then one could determine effects on various modifications. Nr 3 was built as close to the sketch as possible with landing gear and a Pee-Wee engine and was filled with plasteline clay. It was released from a hill out into the snow landscape. Spiral straight into the ground in a snowdrift in so strange way they my hope dissapeared. Several attempts confirmed fears - stillborn. But it was fun to, after some modification, go out in the evening or in weekend filled with expectations to some desolate place or in light from a streetlight see the plane going into the dark trying to decipher the behavior before it dissapeared. Maybe a month later, a Saturday evening, I was out in the one meter high snow again. Now I was determined this should work. Only a light moonlight sparkeled in the surfaces on the small-Spiggen when it glided like a dream out in the dark. Had I changed something? Later it was discovered that at a certain trimming in combination with to much V-shape on front wing the plane was super sensitive on rudder throws. The hinges for the rudder gave not enough precision and firmness to rudder.
The drawing was modifed so that the position between main wing and front wing was changed some in relation to center of gravity to avoid a critical trim position. Main wing also got a slight assymentrical profile to give the plane slightly better float. Many meter paper was used to find final seize, total weight, wingloading and volyme that could accommodate space for radio in a good way.
The result is a Viggen-resembling thing that is 1350 millimeter long, 1040 millimeter wingspan and has a weight of 3150 gram. Speed of about 150 km/h with a trimmed .60 in the rear. To be able to run with pulling propeller, where the assortment is greater, I ordered a new chrankshaft from factory. For the moment I use a 3-blade prop 9x6 but it works also fine to make a 4-blade prop out of two wood 2-blade props.
The fuel system was the only thing that acted up at the first test. Because of the unusual long way for the fuelline it was created a siphon effect in the fuel line that varied with level differences and centrifual forces. Much effort was made to solve it with a pressure equalization device but it was solved with an extra carburator needle, as a restrictioin in fuel line, the problem was solved.
After one year flying this plane the experience is that it is easier to handle then expected and it has a softer and more harmoniously behaviour then a traditional multi-plane.
It would be desired to find an elegant solution to coordinate elevator and aileron movement. The control surface effectivness decreases little to much with speed decreases and in some rolls the effectivness decreases of aileron with use of rudder.
Full scale drawings (18 SEK) can be ordered from Leif Thelin, Nordmannagatan 8G, Kungälv, that also has all the commercial rights.
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Old Dec 20, 2014, 01:33 PM
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Radioflygboken by Pär Lundqvist 1973, three photos
In the book it say the it is from Nordic Championships in F3A 1972 where probably this Spiggen competed with registration number SE-424.

Modellflygnytt nr 6 2011, one photo
Show the color scheme of the Spiggen with registration number SE-424.
According to this link where this Spiggen can be seen the builder was a person Verner Kristiansen (born in Denmark but lived many years in Sweden and was member of Siljansbygdens Modelflying club here in Sweden).
http://www.siljansbygdensrfk.se/gall...bild%2020.html

Modellflygnytt nr 6 2012, one photo
Show a blue Spiggen that still exist here in Sweden. The builders name is an oldtimer Lars Grahn and it was an article about his model flying activity in that issue. Nice model!
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Old Dec 20, 2014, 03:31 PM
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Here is a glimpse from one airshow that Leif Thelin was invited to fly his Spiggen. It was a note in the Swedish magazine Modellflygnytt (MFN) issue 3 1967:

SPIGGEN
Leif Thelin made displayflights with his Viggen inspired Spiggen, that was presented in MFN 1/67, at F5 (wing) airshow May 21. After the show a letter came to Swedish Model Flying Federation and its RC responsible person Gunnar Hoffman with following wording:
"Brother, Thanks for the help. I'm still equally impressed by Spiggen. It was without hesitation one of the airshows highlights."
Signed by Major P. U. Fogde (Swedish Airforce flying school at F5 wing)

It is obvious that his Spiggen was a real attraction at airshows at that time. It was "new", unusual and exciting delta-canard plane that looked like the real full scale Viggen that was on all lips at that time (one of the biggest industrial projects here in Sweden back then).

Leif Thelin also designed in 1967 the club logotype for "AeroKlubben Modell i Göteborg" where he was member and the logotype is still the same today and can bee seen at the clubs homepage here (in upper left corner):
http://www.akmg.se/
Delta inspired club logotype...

I checked at birtday.se if Leif Thelin is still around and I found one person Leif Ingmar Thelin in Mölndal here in Sweden and that person is 88 years old. Mölndal is just south of Gothenburg and when Leif Thelin constructed Spiggen he lived in Kungälv just north of Gothenburg. So it could be that this person it our Spiggen Leif Thelin.

/Bo
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Old Dec 20, 2014, 09:06 PM
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One of our club members built and flew one in 1968. Most impressive in the air, but quite a handful!
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