Thor.2 --- Slopesoarer with F3f/b genes

[vanquish]

Hello folks,

I would like to introduce myself briefly:
I was infected with the model flying virus as a little child. At that time with models made of balsa and plywood. I was infected with slope soaring fever around 2008. Thanks to my mentor Franz Prasch, I had the opportunity to use some great F3f/b models from his own moulds. He taught me a lot about aerodynamic design and how to build moulds and models from them. Over the years, I was able to take part in various f3f-competitions and get to know other crazy modellers and learn from them. I was always in lively dialogue with Max Steidle. He always gave me a push in the right direction. I was able to learn a few tricks from Vaclav Vojtisek when building such models and Dirk Pflug was also immediately willing to provide me with a modern airfoil for my first own F3f model in 2010. Two years later, he also gave me his professional support for my first self-made profiled wing, which then became the THOR.

The 2018 F3f World Championship on Rügen/Germany was groundbreaking for me, as the idea for the VANTAGE was born there. Originally conceived as a private project, the possibility of series production of the Vantage by CCM, a high-end manufacturer from Ukraine, arose shortly afterwards. This was followed in 2022-23 by the small flying wing Riddick and in 2024 the Vrace (Vantage.race) was launched, the development of which was completed in winter 2022.
These last few years have been incredible for me from a modelling point of view. Above all, the collaboration with Jochen Günzel on the VJX project (and later the VJX.glide) and the developement of the Valkyrie for parts of the Austrian F3f team for the 2022 World Championships were a real booster for me. In my humble opinion, Jochen's input and his self-developed software tools (all open source) are priceless! He has taken the development scene, not only in the f3f/b area, a huge step forward.

Some time ago I came into contact with @Jerry--TJIRC Glider uav from TJIRC Glider UAV via Facebook. TJIRC enjoys an excellent reputation and I have to say that communication with Jerry via Facebook or email is excellent! We were quickly able to negotiate the general conditions for the manufacture and sale of a slope-model. The Tjirc UAV team is currently working hard on the moulds and I am always delighted when I receive a picture of their work.
I would like to report on this collaboration with Jerry and TJIRC and provide some background information on the THOR.2. This will probably not happen all at once, but at irregular intervals, which I hope is okay.

To get you started, here is a screenshot of the CAD model from THOR.2:

Kind regards,
Mario Perner

 

[Wayne]

Mario!

Glad you found your way to our forums! I heard word of your new model and have been waiting to hear more info on it!

I just came aware of Jochen Günzel software earlier this month. I have taken a little look at it, but need to read up more on the usage. I know of several really great planes I have flown that are the direct result of his software packages! It is eye opening! I think Thor 2 will be a plane well worth the wait.

Thank you very much for sharing.

 

[vanquish]

Hi!
Nice to be here!

Jochen's software tools are fantastic. I personally use the Airfoil Editor to modify my airfoil-designs and for final smoothing. I don't use XOptfoil-JX, because I want to design my own airfoils. For me, that's exactly what makes it so appealing. Similar to XOptfoil-JX, I also always take an existing airfoil and modify it until it meets my expectations, but seeing how a particular modification affects the characteristics of the existing airfoil is exciting and instructive. Of course, you also need some basic knowledge to use XOptfoil-JX, otherwise you won't get anything useful out of it. But the work is done by the software, with all the advantages and disadvantages.

Jochen has also published some excellent airfoil series. The very fast JX-GS, which is used on the VJX and the wider JX-GT, which is used for example on the MambaGT, or also on TJIRC's WazzUp and also the JX-GP, which is used on the light-condition F3f-modell VJX.glide. All are great designs with features that you should keep in mind when designing the overall construction.

As I said, I would like to share a few of my thoughts on the design of this new model here. I don't want to write a scientific paper on aerodynamics, but rather try to write down my thoughts in a comprehensible way. In doing so, I will probably generalise or perhaps develop aspects too briefly. However, if any questions arise, I will of course answer them as best I can. Of course, I am always happy to learn new things, so I am quite open to constructive suggestions, even if it will probably be too late for the THOR.2.

I developed the THOR in 2012/13. At the time, it was my second mould-making project and the first one completely of my own. That means I also designed the airfoils myself back then. Since I lent the master moulds to colleagues in Austria and Germany over the years, quite a few mould sets were created and, accordingly, there was also a lot of feedback from pilots about the flight characteristics. On the whole, the THOR covered a fairly wide range of uses and also showed a good-natured handling over a wide range. However, it needed a comparatively higher wing loading to be able to keep up in competition and at sub-30 speeds an unpleasant undercutting began. Now you rarely have such fast conditions in competition and if you do, the pilot has to be able to fly it. However, in normal slope soaring, you can quickly reach these speed ranges.​

​

Even 11 years after the birth of the first THOR, this model is still being built in private workshops and serve as entry-level and training models. Somehow I think that's pretty cool and it also shows me that the overall concept was not entirely wrong. So I took it up again and with TJIRC I found a suitable manufacturer.
The idea behind THOR.2 is to construct a modern and broadly designed slope soaring model that, on the one hand, gives hobby pilots fun and enjoyment on slopes, but on the other hand is also competitive enough to enable entry into the F3f and F3b competition scene without having to invest €2000-3000 per model. To achieve this, a few things have to be considered during construction. First and foremost, the buildability/statics and thus the choice of materials for the individual components. The well-known competition models from mainly European manufacturers are so expensive because very expensive materials are (have to be) used to achieve the low empty weights while maintaining very high rigidity or strength. Currently, thin airfoils (less than 8% thickness) are often used to achieve this. The JX airfoils mentioned at the beginning would be suitable candidates. I also used thin airfoils for the Vrace, the Vantage and the Valkyrie. Regardless of the buildability, in my experience, such thin airfoils often require more attention and time to find a suitable setup. At the risk of generalising, I would say that thicker airfoils tend to be more "user-friendly" than thinner ones. With this in mind, I consider a thickness in the range of 8.0-8.3% for the main airfoil to be a sensible choice.​

The situation is a little more relaxed on the outer wing. You still have to keep a close eye on the torsional loading of the wing, but the problem of deflection is decreasing more and more, so the airfoil thickness can decrease towards the outside. So I reduce the thickness on the outer wing to about 7.5%.

Kind regards,
Mario

 

[Wayne]

Very good points and it total agreement. Thin airfoils can deliver results, but the handling and construction costs can work against you. One of the many balancing acts with aerodynamics that I absolutely love. Nothing is free, you are always looking to balance the scales to meet the goal.

I don't know if Jerry told you, but I challenged him to see if he could build a lighter version of one of his models. He recently let me know he managed a huge reduction in mass using different materials. I'm waiting for one of those in the next shipment. I'm very curious to see how it turned out.

 

[Doc J]

Hello folks,

I would like to introduce myself briefly:
I was infected with the model flying virus as a little child. At that time with models made of balsa and plywood. I was infected with slope soaring fever around 2008. Thanks to my mentor Franz Prasch, I had the opportunity to use some great F3f/b models from his own moulds. He taught me a lot about aerodynamic design and how to build moulds and models from them. Over the years, I was able to take part in various f3f-competitions and get to know other crazy modellers and learn from them. I was always in lively dialogue with Max Steidle. He always gave me a push in the right direction. I was able to learn a few tricks from Vaclav Vojtisek when building such models and Dirk Pflug was also immediately willing to provide me with a modern airfoil for my first own F3f model in 2010. Two years later, he also gave me his professional support for my first self-made profiled wing, which then became the THOR.

The 2018 F3f World Championship on Rügen/Germany was groundbreaking for me, as the idea for the VANTAGE was born there. Originally conceived as a private project, the possibility of series production of the Vantage by CCM, a high-end manufacturer from Ukraine, arose shortly afterwards. This was followed in 2022-23 by the small flying wing Riddick and in 2024 the Vrace (Vantage.race) was launched, the development of which was completed in winter 2022.
These last few years have been incredible for me from a modelling point of view. Above all, the collaboration with Jochen Günzel on the VJX project (and later the VJX.glide) and the developement of the Valkyrie for parts of the Austrian F3f team for the 2022 World Championships were a real booster for me. In my humble opinion, Jochen's input and his self-developed software tools (all open source) are priceless! He has taken the development scene, not only in the f3f/b area, a huge step forward.

Some time ago I came into contact with @Jerry--TJIRC Glider uav from TJIRC Glider UAV via Facebook. TJIRC enjoys an excellent reputation and I have to say that communication with Jerry via Facebook or email is excellent! We were quickly able to negotiate the general conditions for the manufacture and sale of a slope-model. The Tjirc UAV team is currently working hard on the moulds and I am always delighted when I receive a picture of their work.
I would like to report on this collaboration with Jerry and TJIRC and provide some background information on the THOR.2. This will probably not happen all at once, but at irregular intervals, which I hope is okay.

To get you started, here is a screenshot of the CAD model from THOR.2:
View attachment 21232

Kind regards,
Mario Perner

Looking good!

Doc.

 

[Jerry--TJIRC Glider uav]

Mario is a really great guy. He is very friendly and very professional. He has a lot of experience in design and production. And European craftsmanship standards.
We exchanged a lot of things in the production field. This glider - Thor.2 will be built using maybe two processes. One is a TJIRC craft and the other is a European standard craft.
Everything is under discussion, so let's wait and see.

 

[Wayne]

Very cool! I think this project will result in a fantastic model.

Has the tooling production begun?

Mario I just noticed the plan cut for the ailerons out very near the tip. Is this something you are able to study in the software, or just a layout you have used in the past? I'm a little shy of running the aileron out that far on a wing that will be working as hard as this one will be for fear of setting up a tip stall. There is that fine line of desired roll rate and maintaining as much tip flow as possible.

I understand the software can help analyze the trailing edge "performance" of the airfoil. I'm not sure what the technical terms for this. But assume it has a lot to do with how long you can maintain a smooth airflow at the rear of the airfoil under a range of conditions and loadings. Basically the better the wing is able to work, the smaller the flight surface movements are, and the smaller the drag penalty. (I think we have all flown some planes that had major issues in this area and the result can be a plane that is very vague feeling.) Wondering if you might share some insights on this topic? I imagine this also touches on the location of the hinge line on a given wing.

(Old school approach to a poor handling is to put in more throw or make the control surfaces larger, but I think the better fix is a better airfoil. I was reading about a full scale airplane a while back where the rudder had no effect until you reached something like 5 degrees of throw, basically the airflow separation was so bad this plane would make the passengers sick from the constant yaw left to right, the only way to stop it was to crab the plane with constant rudder.)

 

[Doc J]

A bit of tech stuff here.

For a design to work well, it needs to use optimized lift distribution, which puts the correct wing chord where it should be to provide the required lift, where it's needed, and only there. The result is a wing planform that can look scary, but if well-designed, the lift profile works well throughout the desired performance envelope. I have seen this trend emerging more in recent F3f model designs. Frankly, stall-wise, there is more to fear from an "Oar Wing" design with larger chords towards the tips than for an optimised planform, even though the OLD planform typically has less wing area. Another critical factor is the aspect ratio, but I won't get into that here.

But - as most of us know - sometimes, to our detriment - most stalls begin at the wingtips, especially the high-speed stall or the dreaded "flick roll", as it is sometimes called. In this case, mainly during high-G turns where the wing might not be at an ideal angle to the general airflow, the stall will propagate at some interference point on the wingtip and instantly encompass half or more of the wing with the resulting sudden re-kit. Often, the aileron ends, being placed close to the wingtips, provide such a stall initiation/propagation point, which is dangerous.

I have studied this spanwise flow phenomenon extensively, and any control advantage that comes from having extended ailerons that interfere with the tips is marginal, to say the least, and far outweighed by the potential danger they present. This idea might be a hangover from F3J models, which are typically much slower and require all the aileron they can get.

The other point is that the airflow does not want to do what we want it to but will always find the point of least resistance to leave the wing. If the wingtip design is not optimized, the spanwise flow will leave the wing with nasty, sucky, draggy, noisy vortexes. Again, I have studied this very carefully and tried many shapes in many practical tests, some quite elaborate, but I have never been able to beat the simple 15-degree cut-off wing end.

Last, putting too much emphasis on computer simulation is dangerous at our model scale. If we could really rely on computer simulation, we would not need those nasty, expensive, noisy wind tunnels—and by the way, neither would Boeing or Airbus. Computers work in linear bits and bytes, but our slope conditions and ourselves are seldom so rational.

It's nice to see a new design and so much effort.

Doc.

 

[vanquish]

Hello,
Thank you for your input! I was very busy during the last days, so please excuse my late reply.

Yes, the production of the moulds has already begun and, as far as I can see from the pictures Jerry sends me, it is already well advanced.

Regarding the aileron question:
In short:
I have used this configuration several times and have had good experiences with it. The wing planform of the THOR.2 is based on Vrace/Valkyrie (F3f world champion models 2024) with a little less aspect ratio.

In long:
When designing a wing, there are basically only two factors that can determine the character of the wing. On the one hand, the airfoil (the airfoils) and on the other hand, the depth distribution, i.e. the geometry/planform. Both factors together determine the lift distribution and thus – roughly speaking – the handling and the induced drag of the wing. For good-natured handling, lift reserves are needed in the border area at the outer wing, for example through more surface depth. However, this in turn increases the induced drag, especially in the high-lift area. The designer's task is to find the desired compromise.

Personally, I like to use a software tool from Frank Ranis for this task: FLZ-Vortex. It is not as powerful as XFLR or Flow5, but it is very easy and intuitive to use and the calculation results correspond very well with practice. My goal is usually to let the stall happen first on the inner wing. This has the effect that the model feels ‘spongy’ or ‘lazy’ at the limit and ideally sags in a controlled manner first, without tipping over at the wing tip. This tipping over happens exactly when the stall happens on the outer wing. By outer wing, I don't mean the tip, i.e. the last 2-5cm at the very outside, but really the area from about halfway the aileron outwards.
The wing tip at the very outside is ‘special’: the wing depths there are usually very small, and the Re numbers are correspondingly small. Re60k and smaller are the order of the day there, and in these areas the ingenious XFoil (the core of XFLR5) increasingly fails. You do get a result, but you should definitely question it. Furthermore, 3D effects appear at the tips, which we cannot calculate with our (publicly) available tools. Here, too, I agree with @Doc J : wind tunnels have their place.

So: in practice, both full-length ailerons (VJX, Shinto, Device, PP2, Vantage, ...) and ailerons that end just before the wing tip (Vrace, Valkyrie, also Vantage, Pitbull series, Freestyler series,...) have proven themselves. All these models are very powerful and at the same time very forgiving. The Vantage was built by CCM with continuous ailerons from the start. Personally, I didn't like that because it gives you no indication of the correct flap position. However, it is very important, especially in competition, to be able to see quickly whether a servo is resetting correctly or perhaps showing a drift or a beginning malfunction. If the control surfaces end up a little further inwards, you have a reference point for this. CCM then adjusted this in production. This change had no effect whatsoever on the handling and the good-natured behaviour, neither positive nor negative.
For my part, I have therefore decided to simply ignore the calculations and theories on the wing tip and instead design this area according to optical and practical aspects.
As for the high-speed stalls mentioned by @Doc J , I basically agree with him. I have not studied aerodynamics, but this behaviour is understandable to me and corresponds to my simple understanding of the matter. In addition, however, I also believe that the stall often does not happen first on the wing, but rather first on the tail, usually due to excessive deflections. This is not easy to see, especially with high-speed stalls. I have experienced this myself with the Pitbull and the Toy, and I have often observed it. A reduction in the maximum deflections is enough to turn a fussy monster into a well-behaved and also quirrel kitten.

Kind regards,
Mario

 

[Doc J]

Well, I thoroughly enjoyed that!

Cheers,

Doc.

 

[jure]

thanks for your comments Mario !

 

[Wayne]

Thank you Mario, exactly what I was hoping you could share with us. It is conversations like this that help all us understand the options and thought processes that go into a design.

 

[vanquish]

Airfoils

When designing the airfoils, I first had to decide which path I wanted to take with the THOR.2. Should the model be designed for rather weak conditions, or more of a model for chasing the F3f world record? Or should I rather look for the happy medium? A good-natured allrounder, as the first THOR already was? Well, as I mentioned at the beginning, I decided on the middle way because I think that such a design provides a more useful overall package for rookies and hobby pilots.

Showing airfoil polars out of XFLR5 is nice, but it only becomes interesting when compared with other known airfoils. In my search for suitable comparison airfoils, I came across the JH817 from @Doc J . He writes about this airfoil that he designed it for fast slope racers/allrounders. Unfortunately, I don't know on which specific models this airfoil is used. At 8% thickness, it is only slightly thinner than the base airfoil of the THOR.2; the camber of 1.77% is the same for both. This seems to be a perfect sparring partner! DocJ has kindly published the airfoil data.
If you look closely, you will see an additional polar, namely that of the Vrace (Vantage.race). The similarity now reveals the parentage of the THOR.2

The following picture shows the JH817 and the Thor.2 base airfoil in comparison. In the area of the main wing with a class-typical surface depth, we are moving in the range of Re200k - Re500k, depending on the flight speed. Anything above that is really very fast and rarely occurs in competition.

What we can see very clearly here are the obviously very different approaches of the two of us. Looking at the Type 1 polars (constant speed) alone, I would say that the JH817 should show very good acceleration in competition. This is particularly advantageous when building up the altitude (‘bowling’) in the first 30 seconds and entering the first leg. I had followed a very similar approach with my Vantage and the JX-GS series also goes in this direction! However, flight measurements have now confirmed that in the F3f course, you not only fly in these very low cL ranges, but use the entire lift spectrum. Depending on the (possible) flight style in different frequencies. An F3f allrounder must therefore cover a wider cL range to score points.

But drag alone is not everything. To be successful, you need more, of course. For example, (maximum) lift.
In my opinion, the F3F competition is decided in the 10 turns. Sure, speed on the course is also important, but the speed must also be brought through the turns. Depending on your flying style, you need either high lift reserves in the medium CA range (EM style) or in the high lift range (Bank'n Yank). Ideally, even in both ranges, but that´s a little difficult . The following picture shows this:

The JH817 is definitely a representative of the Bank'n Yank genre. In DocJ's posts, I often read the term ‘fast turns’ and that seems to be a strength of this airfoil. The THOR.2, on the other hand, has its strengths in energy-management style. However, there is also enough lift reserves for tight turns. This high lift maximum is also an advantage in the F3b high start!

Finally, I would like to show the polar curve (type 2 – constant lift). This is not entirely irrelevant for F3f with its total of 10 distances, especially at slow speeds. However, the THOR.2 (like its mother Vrace) should also be able to perform in the F3b and F3g classes.


I deliberately kept an eye on this during the design phase and expect a thoroughly good performance in cross-country flying. I think that this was not the top priority for the JH817. But at maximum climb rate, DocJ's design is slightly ahead.

That would be the basic airfoil of THOR.2. Further out on the wing, I use Re-number-adapted and slightly thinner airfoils. I'm still looking for a sparring partner for comparison purposes here...

Kind regards,
Mario

 

[Wayne]

Great post Mario!

I like the comparison with the JH817 as I'm sure I have flown this airfoil as I have flown all but one of Hammond's designs. I will say as a sport pilot I really like the way Hammond's planes perform, and yes, I am one of those guys that really enjoys a bank and yank kind of plane. Pretty sure the JH817 is an older airfoil at this point. Hammond is always doing little tweaks. Not sure what all he did on his F3F models based on the RedShift, but liked that he was willing to do something different in planform and airfoil.

I am very much looking forward to giving the new Thor some stick time.

Curious, have you ever met Václav at VV Model? He has some wonderful designs that he seems to update darn near every season. I have imported a several of them over the years and am always impressed. His refinements tend to be rather small steps every time. It is interesting to study his models and the small changes he has made. Small changes to tail area, 1 degree angle changes to the v-tail. Slightly larger wing joiner, etc.

 

[Doc J]

A scholarly study - thanks, Mario.

Quick question - will you publish your profile data?

Here are some insights into the way I think:

As you may also have found from your studies—which I can see have been quite extensive—for my own thoughts after a long time doing aeronautical design work, not only models, although I have done quite a few of them too! I don't place that much value on computer data because, as you say, using your different way, the model is not working in a static environment but in a dynamic situation that changes every second. Computers can only work from good inputs, and it is pretty impossible to duplicate any situation drastically changing by the micro-second.

It has to be said that as our approaches are broadly similar, the aerofoils should not be so different. But honestly, I have found that most of the new, well-designed "F3f type" aerofoils perform pretty well in the boxes we need.

So, having ascertained that fact some years ago, I designed a series of profiles, thinking that if they were my own, I could do with them as I would and tweak them as needed for the models I design. JH817 is one such. Frankly, I really laugh when I see an aerofoil described with the dreaded 'Mod" addendum. e.g: "E374-mod"

From my day job, which was happily not too far from the model size, I could do many practical wind tunnel tests to ascertain the critical points of a good design (for its job). And it came down to the most logical conclusion possible. Planes fly due to lift, so lift must be critical. Now, here, most people immediately seize on the aerofoil as the be-all and end-all of design simply because, due to a number of design and analysis programs - they can. Or they think they can. However, as I have often stated, the aerofoil is only a part of the equation. If you have a wrongly designed wing planform, the best-ever aerofoil will not have any chance to work as well as it should.

So, using what I hoped would be a "good" aerofoil, I designed the Redshift, but with a planform that I hoped would be good for the job - at that time, it was the JH25. I have to admit I made a mistake there. I designed the tailplane volume to be only an "adequate" size, and that caused some trouble. But the model did reasonably well in international contests.

Something new was needed, and I didn't think it would be worth resurrecting that design as a lot had changed, so armed with the new planform data I had been developing, I came up with the Spada design. This is a fast-flying model, and with good acceleration and no tip-stalling danger that can be associated with F3f models, it lands well, too. So now I think I have this planform aspect ratio vs lift distribution problem well in hand. I think I know what is happening and why.

Next, I'm going to incorporate the BSLD wing twisting principles, as Al Bowers and Red Jensen have described, to make what I hope will be a really fast model. I did this at great risk (you know all about CNC mould costs) on my latest little whizzer, the Toccata—it's only a two-metre model, but it goes fast!

Thanks again for the comparison; it is most illuminating.

Cheers,

Doc.

 

[vanquish]

Curious, have you ever met Václav at VV Model? He has some wonderful designs that he seems to update darn near every season. I have imported a several of them over the years and am always impressed. His refinements tend to be rather small steps every time. It is interesting to study his models and the small changes he has made. Small changes to tail area, 1 degree angle changes to the v-tail. Slightly larger wing joiner, etc.

Yes, I have met Vaclav many times. Mostly at competitions, of course. But I also had the pleasure of visiting him twice for a few days and being able to look over his shoulder as he built. He really is exceptionally talented at building. At the time, he had moulds from my mentor Franz Prasch, which he used to build a few models. That was in 2011 )Franz Prasch on the left; Paul, a worker from Vaclav in the middle and Vaclav himself on the right; myself behind the cam ):

happy memories

I flew some of his models and always enjoyed it. At the competitions, Vaclav was always a source of great fun, especially in the after-competition programme Unfortunately, I haven't seen him for quite a while now.

 

[vanquish]

Quick question - will you publish your profile data?

Currently, I do not want to publish the data from THOR.2 and Vrace, because there is a commercial interest not only from me, but mainly from the manufacturers. I ask for your understanding in this matter.
I had published a few of my profiles on my website www.f3f.eu before the hack. Among other things, the THOR profile from 2012. I guess I'll do that again...

In fact, I also believe that you can't just rely on computer simulations alone. They are good and important and - at least for me - absolutely necessary, but you also have to interpret the data and occasionally trust your gut feeling or experience. I see the calculations as a tendency in one direction, but not as an incontrovertible truth. Our models move in a dynamic environment; but the calculation only shows a brief snapshot.

I can remember the ‘Redshift’. At the F3f World Championships 2018 on Rügen, the British team competed with a fleet of Redshifts. In good/fast conditions, the model looked quite good. Unfortunately, these World Championships were characterised by unusually weak wind conditions for this fantastic F3f-location... I can't say for sure whether it was due to the size of the tail unit, but a larger tail volume is needed in light weather. I made the same mistake with the Vantage as with the Redshifts: the larger tail of the Vrace is much better suited to the Vantage wing.

CNC-moulds, master models, etc. are expensive. Fortunately, I am able to mill such parts myself. The limiting factor is time:

​

 

[Wayne]

I figured you had probably run into Vaclav at some point. Very nice. If you ever run into him again, tell him I say Hello. I wish we had more demand for his models here.

Are you doing the milling work for the new Thor or letting Jerry do that this time?

Again thank you for sharing, I know I'm enjoying it greatly, and have heard from a few folks in email that are also enjoying the conversations.

 

[vanquish]

Jerry is doing all the hard work in this case. I only send him the CAD-files.

 

[Doc J]

Hi Mario - thanks for the further information. A few comments below.

HiCurrently, I do not want to publish the data from THOR.2 and Vrace, because there is a commercial interest not only from me, but mainly from the manufacturers. I ask for your understanding in this matter.

No problem. I am an 'open-source' type of person, but I do understand that some people regard this information as "secret".

I had published a few of my profiles on my website www.f3f.eu before the hack. Among other things, the THOR profile from 2012. I guess I'll do that again...

Cool, I miss the old environment where people used to share information so that we could all improve. I'm sure we used to have as much fun talking about the models as we did flying them.

In fact, I also believe that you can't just rely on computer simulations alone. They are good and important and - at least for me - absolutely necessary, but you also have to interpret the data and occasionally trust your gut feeling or experience. I see the calculations as a tendency in one direction, but not as an incontrovertible truth. Our models move in a dynamic environment; but the calculation only shows a brief snapshot.

I see you have a good understanding of it. Many people swear by computer simulations, probably because they have nothing else to go on. Me - I wish I could reliably use computer simulations!

I can remember the ‘Redshift’. At the F3f World Championships 2018 on Rügen, the British team competed with a fleet of Redshifts. In good/fast conditions, the model looked quite good. Unfortunately, these World Championships were characterised by unusually weak wind conditions for this fantastic F3f-location... I can't say for sure whether it was due to the size of the tail unit, but a larger tail volume is needed in light weather. I made the same mistake with the Vantage as with the Redshifts: the larger tail of the Vrace is much better suited to the Vantage wing.

Yes, it's my fault. The model was really good if the wind was strong and without too much turbulence. But if it got choppy or weak, then it lost out quickly. At that time, I didn't fully understand the difference in the wing-to-tailplane relationship between a V-tail and an X-tail, and it was actually quite hard to figure out. I have now devised the formula, and I'm happy to say it seems to work.

Nice-looking moulds. You say you can do the CNC yourself. Do you have a full-sized CNC milling machine at home?

It's nice to correspond with you. I'm looking forward to your model coming out. Then we can have a friendly fly-off in Europe or the USA between the models just for fun.

Cheers,

Doc.