A Flying Wing Design Slope Model

                                                                                                         link: 2 Years on.....

Having flown flying-wing designs for some time now, I am moving things forward to achieving something new, for me at least. A wing that can fly in excess of 150 – 200 mph as a glider with no tail plane, in the dead air on the back of a steep slope using a technique called Dynamic Soaring (DS).

Where did it all begin?
Starting with a “SAS Thing” back in the 90’s which, I built and flew for many hours in some bitterly cold southerly wind conditions whilst in the Falkland Islands. At the end of my tour, it was dismantled (I actually put a saw through the wings to pack it into a box) and shipped it back to the UK before reassembling it and flew it for quite a few years after, complete with the talon wounds inflicted by the territorial turkey vultures, residents of the Falklands.

Because I felt the “Thing” needed a little more directional stability, I then created a new model “Stingray” of similar wing form but different wing section and with a ply fuselage allowing the fin to be further back behind the wing. This improved the flying characteristics of the model. In fact, the foam veneered model proved quite popular with my colleagues who all managed to twist my arm to provide them with a wing plan pack. This worked well at promoting the RAFMAA slope flying wing - fun event. And, for the record, I still have the original! However, this was all before the advent of EPP foam and the famous Zagi models.

At the time of the new combat craze, I found a source of EPP foam and took the general design and created a number of different zagi type models and often cut a few extra wings for those not wanting to pay so much money for a commercial kit.

Next came the “Fling”, another of my own small flying wing designs, about 700mm wingspan, veneered foam wings with an MH 61 section which, is a reflexed wing section designed for flying wings (No tailplane). A fibreglass fuselage based on the shape and size of a model called a “Gnott” which was a free plan in, I think, the Radio Modeller magazine back in the late 80’s. (I had a couple of these little aerobats too – Great Fun!). However, this was my first attempt at making a fibreglass fuselage and I learnt a lot - my first attempt saw more resin on me and the bench than in the mould! The "Fling" was particularly fast due to the high wing loading, but it worked really well, yes it looks like it needed a tailplane, but looks are not everything. The landings were a bit too fast for comfort though. Again I still have the original model, but I only made one of these.

Next came a commercially available EPP model call a Wanabee, made by Stan Yeo at Phoenix model products. I still take this model with me almost everywhere I go. It is a real fun machine and very forgiving, It copes with such a wide range of conditions. Indeed, At a gathering on the Long Mynd, Shropshire two years ago, we measured the wind speed gusting to 72mph. Yes It flew, just couldn’t get it to land…. Eventually landing it inverted………..(Phew!). Sadly, these models are no longer in production.
 

Over the last few years I have become quite intrigued with Dynamic Soaring (DS) since watching a video, from Reece Videos, called “Lift Ticket”. The concept is to fly in and out of the dead air behind the slope in which, speed over of 300 mph can be achieved. Well that was the record when I started to look into this type of modelling. It is now over 400mph, and all with a glider !!!!!!!!.

Dynamic soaring info can be found on a Google search "Dynamic Soaring" and videos can be found again through a Google search "youtube dynamic soaring" , but a couple of links are here to start you off.

What is DS'ing :  http://www.tmfc.org.uk/ds/darkside.html

(An old but informative article)

2008 speed check: 100" glider = 357mph http://www.youtube.com/watch?v=Vi0hrjqU15I
(hold on to your hat!)

Another one for 350kph but this one ends in tears!!!!!

http://www.youtube.com/watch?v=QjWFcYqdgA4&feature=related

I even found a video of a "Weasel" being encouraged on to the darkside and also an "Alua".

http://www.youtube.com/watch?v=d6aEjDNFQAs

Remember, Dynamic Soaring is on the back of the hill opposite side from the prevailing wind direction!

As you will see from the many youtube videos available, DS is not for the faint hearted, but I want to have a go! Not to break the record, or a model, but to achieve a commendable speed with a flying wing (if its a record then so much the better - I'll walk before I run). Lots of research and sketching has resulted in a new own design model called “Dude”. A flying wing design of 60” constructed from Foam veneered wings, with a spar and covered in epoxy glass, a fibre glass / carbon pod and boom fuselage and 2 servos controlling Elevons. The model now flies really well, but in the beginning, this was not the case.

 

Plug and Mould waiting for Fuselage to cure

Fuselage just out of the mould - needs trimming

Dude #1 - dry assembled

The model has now been developed into the 2nd generation model of 72” design “Dude ds”, and a 4 servo wing, allowing different type of control mixing. Essentially, 2 x aileron, and 2 x flaps. These can be configured in many ways, but the idea is that in fast flight, only the inboard flaps would work as elevators, the outboards as ailerons, but for really lively performance they could be configured at the flick of a switch to be full span aileron, or full span elevons… The model flies really well with full ailerons and inboard only for pitch control. This is important when I eventually get the model on the back of the slope for that Dynamic Soaring experience. Consecutive outside loops is particularly pleasing, a rare capability of most slope models.

Dude # 1 (60 ")

Dude # 2 (60")

Dude # 3 (72")

There are only 3 Dude models in existence at the moment with the 72” version built and owned by my good friend and flying buddy Neil Tricker. This really is the model I had in mind when I started to design it, and just for Neil, we had a new shape for the fin. The extra wing span gives the model that little extra lift, but does not slow it down, the inverted performance is second to none. it performs consecutive outside loops with more grace than the 60“ version and with the various control mixing, it generates a major grin on those that fly it. And what’s more, although quite critical to set up correctly, it also allows for crow braking, slowing the model up for landing. . I have yet to build one of these, or at least have a second 72” wing for the original fuselage.
 

The Need for Speed….
The next stage is to build the 72” – “Ultimate Dude”, Hopefully the model that will be put to the test during Dynamic Soaring conditions. The model construction will be similar to the original sport versions but instead of wood veneer on the foam wings, it will have Carbon and Kevlar, with living control hinges, making for a much stiffer and stronger wing. If you have seen any models being subjected to Dynamic Soaring, then you will know that they need to be very strong.

Lots to do.....

I need to build a 72” wing and get my head round the mixing required, then create the carbon Kevlar version. However, I need to hone the vac bagging technique of carbon Kevlar wings yet. So making a new wing for a new SmArt model is now required (uses less carbon and Kevlar cloth so will be cheaper on any mistakes), so that’s another to-do job.

The photos depict some of the stages of build of the component parts up to dry assembly. And then the finished models.  - more models to come!

At the Lleyn slope fly-in event in October 2011, the model was flown by Andy Ellison (RCM&E Slope columnist) resulting in some good photos and encouraging words. (RCM&E January 2012 – “Hey Dude”).

2 years on and I now have a new 72” version of the Dude.

A lot has happened in the Waite workshop since my original Dude article but 2 years on I now have a new 72" Dude to show off.

As previously stated, I needed to hone my skills and the techniques for vac bagging and produce some glass covered wings with living hinges. To keep cost down and the project small whilst I develop the new skills I developed the wind construction technique for my new small fun sized aerobatic model to replace the aging SmaArt model. This new model is the “Midge”. Indeed I have made quite a few wings for this new model, some with wood veneer press onto the cores with epoxy, and also multilayer glass with living hinges pressed straight on to the foam cores which have been particularly successful.
 

Utilising my CNC foam cutter I created the blue foam cores for the new 72” Dude. I prepared some Mylar sheets on which to lay up the glass cloth and hinge material.
Having incorporated the servo wire conduit, installed a shear web “I” spar from 1/16 ply topped with carbon tows, a carbon leading edge. Plywood reinforcement for the root chord and balsa wing tips, each panel was subsequently vac bagged.

Once the excess glass cloth and resin was trimmed from the cores they were then joined, spars joint filled with Carbon and then reinforcement glass cloth layered over the join and subsequently put back in the vac bag overnight.
 

The control surfaces were prepared by removing unwanted core foam material up to the hinge and then fettled until the controls were free to move. 2 controls per wing, Elevator and Aileron, but with mixing these can be programmed to work together (Elevon) much like the smaller 60" version of the Dude or individually. The servos were installed into the 50mm holes cut into the underside of the wing and used some ABS covers to finish the installation off.
 

A new fuselage was fabricated with a slightly longer carbon boom and a new shape fin which is more akin to the shape of a surf board skeg. The whole model was finally lightly sanded before the new colour scheme being applied.
With the model balanced where I calculated the Centre of Gravity to be, a test flight was arranged at my local slope, Parlick, Lancashire.
 

Conditions were very light but good for a first flight to get everything sorted. I was very glad of the light conditions as the CoG was a little too far back giving an exceptionally twitchy model to control and land safely. Fortunately I had pre-empted this very situation and after selecting the individual control mixing and application of rates, the model was landed successfully.

Having moved the C of G ¼” forward, the model was then committed to the second and subsequent flights, this time much more secure in flight envelope and whilst the conditions did not allow for much height or manoeuvres to be performed, I was able to trim the model for normal flight in readiness for better conditions.

Two weeks on in early December I met up with my flying buddy Neil, at the Long Mynd, Shropshire for a long weekends flying. The 2nd day weather conditions favouring the Dude. (the 1st is a story all of its own - Sun and Ice) I was not to be disappointed. Gaining confidence that the balance and set up was good the flight envelope was expanded; rolls were good, not as lively as could be, but more than adequate, multiple loops and bunts were good, and if put into a gradual stall situation, it just didn’t. The model just nodded slightly having pulled the stick back gently to the full deflection, only being able to induce a predictable stall with very aggressive use of the controls.

Such was the confidence, that Neil reminded me I was pushing my luck whilst pushing through half bunts for turn round manoeuvres close in to the slope… but it did what was asked of it and quite impressively too.
 

The 3rd and final day to our expedition also did not disappoint once the low cloud had cleared. A nice sunny day with good lift and again the model was pushed further and was at one point, flown alongside Neil’s Dude for comparison with both offering a similar flight performance, but what was noticeable was that my model had come out a little lighter than Neil’s original, possibly due to the different techniques during the wing fabrication. The use of crow brake was good allowing for a slower than normal landings which to my surprise was fairly easy to set up on this flying wing.
 

With smiles all round we headed home and I’m looking forward to getting some big air beneath its wings and really pushing the envelope, hopefully the coming weeks and months will be kind. Indeed, with Christmas just a few days away, I should be able to get out and be forced fed fresh air stood on the side of a hill.
We also need to get a date in the diary to meet up at Rushup edge in the peak district to try some DSing.

If you are interested in the Dude or have any questions, why not get in touch.

The Dude recently featured in the March 2016 RCM&E article by Andy Ellison.

Happy landings.

Colin