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Updated 14/05/06 - Issue 57 Click here to go directly to recent update below:
Feb 2006: At the RAFMAA main championships back in September 05, Garry Chiles impressed me and many others, with his new Discuss Launch Glider (DLG). His launch technique seemed pretty good, which allowed him plenty of height on each launch. Lee Wilson offer his excess energy and helped time and time again to sling shot the DLG to the heights that far exceeded than that normally achieved by a standard Hand Launch Glider (HLG). I even managed to blag my way (well, Garry offered) to having stirring the sticks, Garry even launched the model for me (what a nice man), which I might add was probably for the best considering my recent efforts and poor technique—more about that in a moment.
Afterwards, I gave the model a thorough looking over and generally guessed the Dimensions, with the aid of the Mk 1 calibrated eyeball and a few props from the tool box………...
After the weekend and on return to the workshop I set about drawing up some very rough plans. I knew I had a carbon fishing blank in the loft, which would probably lend itself well to the tail boom. Ply and balsa for the fuselage pod, and balsa tail feathers. As for the wings, I had some wallmate blue foam which was only 25 mm thick but would probably suffice.
The wings came first. I joined two layers of blue foam together using a light coat of copydex to make a piece of foam 50mm thick. A bit of a dilemma ensued as I did not know which wing section to use. A bit of research of other DLG models on the Web suggested a number of
different sections. Some a little too thin for my wing cutting
technique— sections more akin to moulded wings. I
The foam was then cut out in my usual way—templates and hot wire to form two separate wings panels—not bad. A hole was cut through the centre of the section full length of each panel to accommodate a 5mm carbon tube as a spar. As you can see from the first photo, the wing section is pretty thin at the tip and the spar is visible; this was glued in with epoxy. A 1/16” ply reinforcement disc was sunk into each tip on the top and bottom surfaces to accommodate the 5mm carbon tube—wing peg, which is used to hook your fingers round to aid in launching the model.
A layer of glass wing skinning cloth and resin was wrapped around the leading edge to give some resilience to the wing followed by a layer of glass cloth to the under side. Once dry, 3 carbon tows were laid against the trailing edge of the foam cores to provide strength to the TE. Two layers of glass cloth were then applied to the upper surfaces of each wing panel and wrapped around the leading edge. The ailerons were then cut out and faced with 1/32” ply and coated with a thin coat of epoxy. The servos were laid into the foam on the underside of the wing and connected. Both panels were then joined together with a ply and carbon brace; 7 ” of dihedral seems a lot, but it works well.
The fuselage evolved as I went along, tweaking the shape, and re-tweaking as I continually changed my mind where I wanted the servos, how method of attaching the tail boom etc. Wish I’d made the nose slightly wider!..... Battery is a bit of a squeeze!
The radio was installed in front of the wing with a push rod running outside of the tail boom for the elevator and closed loop through the boom for rudder control. The whole model weighed in at 1lb 2oz, giving a wing loading of 8.25oz/ft2 not bad if I say so myself.
On the big day, the weather was calm, with just a slight breeze. A trip across to the local school field allowed a fairly private test of the unknown, but by the end of my hour long session I’d had quite a string of spectators. My main fan was my Son Matty, who took all the photos (80 in all) and a number of videos with my phone…. see the streamed video below.
required. Due to the flexible nature of the tail boom (I thought it would be stiff enough) the model rolls quickly during the launch but is totally manageable, but poor technique, control inputs and the extreme angle restricts the launch height. I need more practise!
The model performed extremely well—yes I impressed myself, but the slightly too flexible tail boom makes for some interesting characteristics if too much elevator is applied. I need to modify the boom to stiffen it up….. Anyone have any ideas? I think the pictures speak for themselves.
The problem is now sorted! I’ve had the model flying off the slope, at an AUW of only 1lb 2 oz, it coped brilliantly with the 25mph wind with no ballast. Furthermore, the consecutive rolls, loops, bunts (all intentional) were really true. The stall is gentle and the model is such a dream to fly. Ask Lee Wilson cos he offered to swap his Gnott ……….. The proof came last Sunday, when my Son was given the controls. Matty has only been out flying three times but is doing really well. He took a shine to the model straight away, putting it through loops and rolls within 10 minutes… I had to prise his hands off the tranny. Now he wants one too and insists that we take the DLG up on the slope every time, regardless of the weather! 
So what did I do to get it sorted? The tail boom was a little too flexible, I discussed the problem with Steve Hart who suggested that I bind the boom in Kevlar string. Well, not having any string and being a guy that would rather improvise and than spend more money - I mean, I used a free fishing blank for the boom for goodness sake……….I used some of the threads from a square of Kevlar cloth that I acquired some time ago. I wet the kevlar thoroughly with resin, put it in the drill and twisted it well, then set about wrapping the boom in two directions—don’t know if this was the right way, but you have to try these things. The outcome didn’t seem too impressive so I stripped the Kevlar cord off and did it again, a little neater this time. The boom isn’t too stiff now, but it has overcome the problems—a good compromise. As for getting some colour onto the wings—Naahh, it’ll just add weight, lets just fly it! I’ve been surfing the ‘net and discovered a few secrets on how to get a better launch. During yesterdays outing to the slope, with rather becalmed conditions, I set about doing a few electronic tweaks to the controls. A few mixers later - reflexed ailerons and some rudder for launch saw the model launch become much straighter with less tendency to roll and attain twice the height previously attained; drooped ailerons for landing - still playing with these.
Whilst the model was
being built, I saw another DLG model on the internet called the ‘Blaster’
available from Vladimir's models in the Ukraine. I was so impressed with
its performance on the streamed videos (http://www.kennedycomposites.com/blaster.html),
I actually ordered one. Well, three to be exact, because having told Lee
Wilson and Garry
Colin Waite
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eventually settled on a pretty standard section—MH32 with some wash out
at the tips and a 60” wing span.
nature of the carbon blank, and was eventually
permanently attached using epoxy and glass cloth. The tail feathers are
balsa covered in glass cloth with two carbon tows applied to the
leading edge.
In
the last edition of the Newsletter, I brought to you my new development
project, an own design Discuss launch Glider, which I was very impressed
with, but there were a few problems that needed to be ironed out. The
problems were all associated with the tail boom that was a little too
flexible.
Chiles
about the model, they put in an order too. Garry even went to the
trouble of selling his original West London Models DLG so his missus
didn’t get too upset with him ordering a new toy….. Delivery took some
time and when the models did finally arrive, only two turned up. Having
suitable drooled all over them I duly passed them on and I ordered
another one for me — maybe it’ll get here for Christmas? However, I am
so pleased with my own model, I’m not sure I need another; but the
Blaster is nicely finished, it looks really good and if it flies
anything like on the video, WOW - it’s what dreams are made of and it is
a source of inspiration to get the best out of my own design. Lets go
and have some fun!