R/C model DG 500 Elan makes history

updated 10/1/08

The posts quickly ended before we got to thirteen (I am not superstitious) but the maiden flight on post no 13? I wasnt going to take any chances anyway here is the whole story .

A group of us went down to Volksrust from the 2nd of January 2008 until the 6th my intention was to maiden a HILL BILLY a JART give my SWIFT-S1 its second flight and finally maiden the DG500 ELAN which at 7.4mtrs and 16kg ,we believe is the largest model glider flying in South Africa at present but we stand to be corrected .

Conditions most days were good in the afternoons with some flying in the mornings between lulls generally with light gliders or electric assisted soarers,this allowed us to fly everyday and for the first time , I flew from the Eastern point , the northern point both with small lift bands and patchy lift , and tricky landing areas (ok for foamies).
Friday saw Charl and Peter join Piet and myself as well as ,Glen from Pinetown and Herman and Izak from ETB. During the day some "other" pilots also flew from the southern slope with us.The day started out with the mountain top in the mist and only Izak dared fly in these conditions keeping his Zaggi at extremely close range.
I decided to set up the DG 500 so it could be checked out , fortunately Andries from ETB popped past on his way home to show off his extremely well detailed ASW 29 complete with pilot, detailed cockpit and working retract with wheel brake coupled to the airbrakes a real craftsman and I asked him to also check out the DG.
At this time I had a few concerns 3 actually and was curious to see what others would pick up. These guys all questioned the same things so I felt better.
They were
1. are you happy with the springs on the rudder closed loop system(a bit soft I had thought) I had bought stronger ones so decided to swap to these.
2. are you happy with the tailplane incedance, I had checked at home and felt it looked wrong although it had been set at zero-zero when I built the fuselage, by moving the postion of the tailplane slightly forward it had raised the leading edge, I had rechecked it and reshaped the saddle area to bring the leading edge down by 2mm back to zero-zero. So this was now ok.
3. The joiners had been bonded in so they would fit between the wing skins, in hindsight I could easily have added a few more degrees dihedral and they would still have had space so the wing
only has a small dihedral and this is one thing I cant change.

The group who checked out the DG500 included Andries J.G. from from ETB a skilled scrath builder of large scale gliders, Piet R. from Berg an experienced glider pilot of many, many years, Peter K and Charl V. both glider pilots of both full size and models, none of this group had any concerns and all agreed the glider was ok to fly.
The control throws and radio range were checked, but as I had no intention of flying it off the southern slope, a photo session ensued, were upon it was taken apart and packed away.
Later I maidened a new Hill billy which is for Blake my son and also my Red Jart see the video on the Jart blog., both flew fine.

Saterday dawned with signs that the wind had again shifted ,more Northerly so things started looking more promising for the DG500. When we arrived on top of the hill the wind was very light but blowing slightly from the north and not generating much lift.
The ETB guys had some fun launching their discuss hand launch gliders directly into the light thermals that came through Piet "bless him" set up his bungee and attempted to launch his 20year old gentle lady into the lift. Charl (Mr punchout) flew his electric as did Peter with his Hawk , surprising Peter logged nearly an hours flying time in these conditions.
At about 14-00 hours the wind swung straight onto the slope and picked up to gusts of 20kmh, some bigger ships seemed to stay up no problem so I gave the JART a flight it really zooms around the sky and at this stage all of us had gliders in the sky, including my son Blake
who stood next to me proudly launching and flying his Zaggi on his own, he now needs to get some stick time so he can advance to his Hill billy.

At about 16-00 hours the wind was good and very bouyant so I decided to fly the SWIFT to test the air. The original wing joiner had gone missing so for this trip I used a substitute which has no carbon in it , anyway after Charl gave it the heave , I was walked back up to the top as it continued to gain impressive height, when settled on top I decided to start decending as it was at speck height, on one of these passes the rudder started fluttering and made a big noise, as I fed in some up to slow things down the rudder broke free, the left wing realising big sh..t was about to happen decided to abandon ship . The fuselage realised at this time it was in deep cr..p and it was best to make a dive down and hide amongst the rocks well away from the pilot who started this whole chain of events ,which it promptly did way down the slope.





Blake and I went to recover the pieces, visible in the centre of the photo and I am amazed at how little damage it suffered, the wings have some minor delamination, the stabilizer is fine ,the fin and rudder was ripped of on impact and two tears in the glass at the nose, the servo tray broke free and the wing joiner is scrap...one weekends work and it will fly again.


At this time I decided the wind was right and proceeded to assemble the DG500 and give it some final checks. Peter and I walked to the edge and discussed the plan of action should an outlanding be required, we both agreed the wheat fields aproaching from left to right was the best bet, I prepared a pair of binoculars in case we needed a spotter, those fields are a small target from the top.

The range was checked again and the team discussed the plan of action ,we then moved forward for some final photos.

Double click on the photos for a full screen shot

From left to right yours truely, Peter with his cap in launch position, Charl all 6feet plus of him , Glen glider and Piet the official photographer.
The brewing storm can be seen in the background.

The team took up their position and I suddenly needed to adjust the rudder this was probably due to the stronger springs, Charl looked back for the go ahead no..no..no.. now the last two segments of my arial had suddenly collapsed inwards...was this a sign ...hell no I was not aborting at this stage out with the insulation tape a quick bind and we were good to go, I gave Charl the thumbs up and he started lifting the heavy glider as it came up it started lifting, Peter on the right wing let go Charl started pushing out, Glen who because of his age and perhaps seperation anxiety decided to play last touch (sorry Glen I would never tease the guy who spot landed on my park flyer breaking off its tail).. Anyway the DG pulled slightly left I pulled the sticks right and they leveled in less than 5 mtrs of flight, the glider flew straight out no drop in altitude as per my Ventus.

The usual suspects all cheered behind me as I gained height which was no problem.
Glen walked me back up and I settled down , the only trim was three clicks of up at launch,
I did some passes hands off and she tracked straight and true, dual aileron rates speeded up the turns and deploying flap almost stops this gracefull beast in its tracks with a small nose down decent, what a relief no ballooning up.
A glance behind showed the storm getting closer so I shouted landing and asked everyone not to take their eyes of the glider, I started my approach much higher than normal and the final decent with full flap the DG continued downwards not gaining speed, once again the Blesbok grazing took one look upwards and bolted fortunately to the side and safety , I closed the flap and the nose lifted ,the chorus behind me rang out nose down ...nose down who am I to argue out went the flaps again and a smooth touch down at my feet. Total flying time about 8 minutes.
The agony of the SWIFT now replaced with the Exhileration of a safe maiden flight.

My thanks to the team who assisted with the first flight, plans for something bigger who knows but I really wish to fly more in 2008 than build, also some Ideas about glider to glider in flight video I would like to try , as well as ,assist some other pilots get their big ships into the air, Peter? Charl?

mission accomplished.
Mike May

PS Piet provided the fight photos, as it is launched and landing sequence.

DG500 ELAN post 11

Well Christmas has come and gone and I hope it was a joyous and festive time for you and your loved ones.
I have just popped in to the office for a while so I thought I would do the last post before the DG500 is off to the slope for its maiden flights. During the last couple of days , the weather has been hot so epoxy tends to cure rapidly so progress has been speedy, and I am multi-tasking to finnish this glider.





In the last post I was busy bagging wings, these came out ok but a tad on the heavy side, but hugely strong with all the carbon( the pair weigh about 7500grams).
The wing joiner and wings all fit together nicely and now I am busy setting up controls and servo's .















The rudder is operated by a closed loop system and as an avid deepsea fisherman I found some stranded trace wire with a plastic sleeve in my tackle box which at 90lbs breaking strain was ideal. This was cut to size and crimped together(no solder here), two springs attach the cables to a bellcrank made of dural which in turn is driven by a servo/ linkage.
















The nose weight was moulded in a foil disposable pie dish (thickish aluminium)which was fashioned into a shape that would fit the gliders nose(about 2.5kg needed to balance at this point).















The nose weight is held in place by two steel bolts which have been epoxied into place with large washers and then glassed over with carbon cloth to spread the loads. I cant have this weight move about . I have also made a set of smaller weights for trimming.




The all up weight has now been revised to 15kg which feels dam heavy to me, but gives a wing loading of 69gr/per dmsq, I saw a video on the internet of a 7mtr Nimbus being launched and flying gracefully at a wing loading of 100gr /dmsq so maybe its not to heavy.
If it should ever land out it would require a team to fetch it, I get tired just moving it around.

Very rigid wings these with hardly any flex, in this photo it is fully weighted.


Cheers for now,
Hope it flies,

DG500 post 10

Wing bagging

The techniques I use work for me but there are many little tips and tricks that other builders use that are good , so experiment and find a method that works for you.
The photos here are not great ,but its difficult to use a cell phone with a hand full of epoxy.
Hereunder the lay-up of the DG500 wing , which will be done in four steps bottom of each wing then top of each wing one at a time.






This photo shows, 1. prepared ,sanded and cleaned wing core.
2. vacumn bag material (tube, blueish colour)
3. mylar thick (white under the wing)350micron
4.breathers I use batting from a sewing shop, which is rolled around some dowel sticks(left)
5. Roll tacky tape for bag sealing(prestik also works)
6.strips of peel-ply (on the right).











The mylars are cut to shape and waxed with release wax. Then the bag is prepared with the breathers down both sides and across the ends.Note the breather cloth wrapped around the vacumn pipe on the near left hand corner.


Ghetto blaster on the left provides music and is of vital importance.(yellow.)
















The mylars are polished off with a soft clean cloth and then sprayed with 2k as many coats as is needed to get good colour coverage, in this case about 4x I also do not thin this paint to much, about 10 percent thinners for a low presure spray gun about 2bars , the gloss will come from polishing later.














Once the 2k paint has dried ,the 1st layer of glass cloth is cut out to shape, as is common practise a fine weave against the outer paint gives the best finish , here I have used 106gr not at 45degrees, but straight.













Next I have cut at 45 degrees the 196gr carbon
cloth, this is were the torsional stiffness will come from. This layer is cut to size on the mylar with the 106gr underneath(dry).






















I now pre-weigh several cups with 50gr of resin in each(epolam 2022), the harderner is added as I go along, it takes some time to wet out and work the resin in ,on these long wings.





















I carefully fold back halfway the carbon cloth and then wet out the glass cloth, speading the resin in evenly with a plastic telephone card.

























The carbon is then folded back and wetted out
and then the dry half folded back and the wetting out repeated . This way the cloth is not removed from the mylars which sometimes distorts its shape.(you can clearly see the wet out area).





















This step is to lay on the UD carbon which is layed on and then had the pink plastic backing removed, I add resin which I work in lengthways with the fibre grain.




















After a few minutes the backing strands seemed to soften and with a little work can be scraped off with the card.































A second layer of UD goes on the first meter of wing and the srands also removed, I check for any dry spots and add a little resin if required.
At this point I transfer the mylar onto a strip of
paper towel this aids in sliding it into the bag, and soaks up excess resin.

The wing core is placed onto the wet skin , and carefully aligned, then because I am only doing one side I tape some strips of peel-ply over the leading and trailing edges.













The whole thing is slid into the bag and rechecked for position and then sealed and the vacumn applied, the wing core is now placed on a
flat surface and the core shells placed under the core and weighted down, this prevents any warpping that the bag may impart onto the wing.
The vacumn will be held for at least 10 hours.
With a bit of luck this side when opened will reveal a smooth strong shiny surface(I am holding thumbs).All the above work was done yesterday between 11-00 and 17-00 hours including coffee and lunch breaks .

The wing took 300grams of resin to wet out .
The above process will now be repeated for the other surfaces, after which the edges will be cleaned up and touched up with 2k and my airbrush, then comes polishing and finally the cutting of the control surfaces and servo fitment and wiring.
The next post may well be the first flights .

Have a great festive season
cheers for now.
Mike

DG500 WINGS post 9

This is a long build thread because these are long wings, but here goes...

The feather cutter made a nice job of the cores which have all been bonded together and prepared for later vacumn bagging. Rainy weather over the past long weekend allowed me to accomplish a lot , but the coolish conditions slowed down the epoxy curing times(probably not a bad thing to put the brakes on a bit)

The leading edges have 5x 12k tows layed on just to add stiffness and a strong edge which stands up better to minor dings and bumps on landings.

The leading edge is painted with resin and this holds the tow on as it is wetted out , I dont use contact spray glue but some guys do. A layer strip of 104gr cloth is layed over the tows and wetted out.

The slot for the joiner box is cut out using a rib template for accuracy , note the grove I have routed out with a dremal tool , this is the channel for the wiring.

The joiners were glued in with Sika-dur epoxy and the wings aligned on a flat surface a little dihedral was also built in .The joiner was masked and held in position while things cured.

The groves were sanded into the foam along a straight edge and the 60k tows layed into the bottom surface. In this case two at the tip increasing in steps to 16x at the root (about a 1mtr long , out past the end of the joiner box)

Left overnight to cure.(Epolam 2022 epoxy system)

Some carefull measuring and , now cutting against a straight edge with a big stanley blade(the smaller blades tend to wander cutting through thick foam)I cut down to the carbon spar cap below. Using a large flat screw driver I broke out the foam. The exposed carbon is sanded clean so that the shear web can adhere well.

In this photo the shear web(premade earlier) was placed in the grove and needed a little shaping in the outer /thinner part of the panel .

I then bonded IT in with strong structural epoxy, in some places I had gaps, these I filled with Epoxy resin and flox, paste. This was placed on a flat surface weighted down and allowed to cure.

The initial wing design is a four part with removable tips for transport, so I have extruded 2 x carbon rods 12mm thick that fit into some aluminium tube(curtain rails ) a little overkill, but I plan some longer tips later so this is insurance. The tubes and the incedance tubes are epoxied in(the cut line is shown and measured) so I can cut exactly right once its bagged.

The top surface carbon tows are layed again into a sanded grove and after curing I have screeded on a paste of epoxy/ micro ballons.

The top surface is under compression when flying(normally this is were a failure occurs first) so it has more tows 3x at the tip stepped to 21x 60k tows at the root also about 1mtr out past the joiner box.

Here you can see the areas that have been filled on the under side , the hollows at the joiner box are filled with a strip of balsa and epoxy balloons.

The surfaces will be sanded smooth , blown free of dust and the skinned and bagged.

I weighed these super rigid wings and they weighed....

Left 2047 grams

Right 2054 grams

a differance of just 7 grams , this is good as a balanced aircraft is easier to trim and indicates consistant use of materials and epoxy.(and a little luck)

___Fiddly Bits____

While the big pieces cure , I multi-task and do little things such as

The top of the tailfin has been cut open and two pieces of ply , shaped to fit inside, these where drilled to accept the servo and then using a piece of balsa cynoed in place.

The cable tie prevents the piece from falling down inside, the servo tray is epoxied into position. Next I epoxied two captive nuts the kind with little points on them (as a precaution put some release wax on the bolt threads)using a tweaser these are held in place until the cap screw can be threaded in . I use a washer as shown and pull these up tight , the points penetrating into the ply, the cap screws are then removed .

Thats it for now , next the mylars need to be prepared and the wings bagged, I will post these later this week.

I hope this build thread is informative , but any questions are welcome other than those of the perceived angles, parallel or perpendicular type.

Cheers for now.
Mike

DG 500 part no 8

The heading should read "Stoned on foam fumes" really its smokey in my Skunkworks and I am not sure about its effect on your health but it has all gone rather well with the foam cutting.





The panels have all been cut to 570mm sections because the foam has a width of 600mm but the lap joint needs to go.


End result unless I cut the sheets lengthways is a new trimmed wing span of a mere 7040mm
which honestly looks about right for the DG500. The mock up with the ventus wings was only to get some ideas.

The new specifications are as follows
Wingspan excluding winglets 7040mm
Area 205.20 dm sq
Loading 56.04 gr per dm sq
aspect ratio 22.8 to 1
estimated AUW 11.5kg
M.A.C. 313.65


This photo indicates how far into the span the shear web goes.
Currently , the panels are being glued together and will then be sanded smooth, next step is to slice a piece out and test fit the shear and joiner box( the dihedral that can be built in and set up when this is glued )back together.
To keep everything in line between the left and right wings the joiner blade needs to be in both boxes.






The weight of the white foam and joiner box/shear web is 1.261kg per wing, resin and glass
will probably double that.




Once the basic wing is assembled,there needs to be a premade channel for installing the servo wiring this will be just behind the shear web.
Then the carbon tows (1x60k goes onto the leading edge) and then the carbon tows for the main spars once this is cured a quick sand and the surface skins can be bagged on.

It looks like the skin layup will be as follows from the outside in
104gr glass straight weave layed straight.
196gr carbon at 45 degress.
UD carbon gr? 2x layers 1.5 mtr out 1x layer to tip.
all wing epoxy is the Epolam 2022 system.
should be very strong .

Cheers for now.
Mike

DG500 ELAN part 7

The block of white foam that I started with is a distant memory and that first adrenaline rush as this beauty takes to the sky draws near, so here are more steps in the build which will be posted right until the maiden flight.

The next task is wing cutting and in this regard both Evan and Peter have been invaluable and a great help. I have always cut wings by hand and it was always a hit and miss affair, the last wing I cut like this, was the JART and its very thin profiles made it a nightmare.

But this has all changed, what a revelation ..........my own feather cutter and it works like a dream.

The DG 500 is based on the HQ 3/12 profiles well proven on large scale sailplanes , I cut some

balsa templates for panel planning and

layout , these will be cleaned up and transferred to Formica sheet as templates.












The white extruded foam is cut into 600mm x 360mm blocks which once profiled will be bonded together using Alcoline extreme (tip: wipe the areas to be glued off with a damp cloth)

The foam ceiling boards have a lap joint which needed to be removed.

I had to check if it worked and the wire heat is was ok.. The results far better than I can ever cut by hand.. to master the taper cutting I will use the foam calc program which is on the Jart Blog.



























This weekend the wings need to be bagged or close to that

In the meantime two new challenges (notice I dont use the word problem) have presented themselves.1. the servo tray is exactly in line with the wing joiner box, so running braided steel control cables to the rudder is a problem. The solution is to install small ball bearing pulleys (I have some)and go over or under , or scrap the servo tray and mount the single servo on plywood blocks lower down on the belly , option two probably better but could pose a problem if I ever fit a retract.






2, the elevator servo is to mount in the tail fin(much like the CMP discus featured recently)




this may compromise the strength of the fin . It now makes sense to install the servo into the fin from above, would be a neat solution with equal strength both sides , option two seems more likely unless I can think of any down side.

more later,
Cheers.

DG500 BUILD

Well weekends are for building the big pieces , I tackle smaller components during the week,the weather on saterday kept looking like rain, but I managed to water paper the rudder, tailplane and fuselage , and spray the final coats of 2k white.

In the photo above you can see a dowel through the fuse which makes handling easier,it also acts as a referance marker for the wing joiner tube which needs to be bonded in later.

I went about it like this, and hoped that my initial wing positions on the plug were accurate,I did take as much care as possible at that stage.









The template (HQ 3/12 )was placed on the fuselage and the pilot hole drilled, a thin carbon rod was pushed through and the fin checked for verticle, it was spot on , so far so good.(dont use the column as a referance the glider was leaning a little, check the carbon to the wall top)

Happy so far ,now I check from above (the wooden dowel fitted) the carbon rod on the centre line, the dowel is 90 degrees to the centre line and parallel to the set square, everyone happy.


Next I started with the major shear web which will extend 2.4mtr into each wing , on the Ventus I made the shear web out of a spruce strip with a carbon sock over it and it worked ok, as this span is greater , a different approach is required.



I purchased several sheets of 5 and 6 mm balsa(pity I did not have my scale with) I choose the pieces for stiffness and lightness but just look at the variation in weight. No problem the denser balsa will go inboard the lighter to the outside.





I cut and glued 2x 5mm x 40mm strips grain lengthways , then I cut endgrain pieces from the 6mm sheets. Next I cut out strips x4 of 45 degrees 196gram carbon cloth , lovely stuff this.



The proceedure is as follows onto a mylar sheet on a flat surface , you lay a strip of peelply, next comes the long strip of balsa, I wet this with resin first then lay on the carbon strip. I then wet out the carbon and place the end grain balsa pieces on ,each one lightly brushed with resin.
Next came another layer of carbon , wetted out and then carefully the layup was flipped over , carbon onto the peelply. The same proceedure on the top and closed of with peelply and mylar.

I now placed a piece of wood (straight and flat) on top and loaded on some weight

(you could also vacumn bag this sandwich).
I cleaned up the edges with my belt sander and now have a strong light shear web which will be built into the wings between the carbon tow spars.

The next big step is the cutting of the cores and preparation for bagging the wings.
Until then .