Because this Blog is updated regularly it is a good idea to visit at least once a week so as not to miss anything. If however you are not a regular visitor, please use the archive links, at the bottom of the side bar on the right, to view postings that have moved off the main page. Or type a key word in the search block in the black bar at the top left and click on "SEARCH BLOG" and it will take you to the posting within our Blog. (For instance, type "Jart" and all the post that mention Jart will open) The Label at the bottom of a post can also be used. Click to get all posts with the same label together!
This BLOG is best viewed at a screen resolution of 1024x768. Click here to get instructions on how to adjust your monitor to these settings.

Monday, December 31, 2007

An Old Toppie and his three 20 year Old Gentle Ladies

Well the year 2007 has come and is just about gone. So I thought that it would be a fitting time to finish some not complete projects that I started this year. With the holidays on hand I managed to revamp my Gentle Lady and to complete my Hill Billy and also progressed with my Jart project.

The pictures (below) that I am posting were taken twenty years ago of a Carl Goldberg Electra(a modified Gentle Lady) and my two daughters Celeste and Lauren take with my film camera in 1987-1988 when Lauren was 2-3 years old and Celeste 4-5 years old.

The next picture was take yesterday the 30 Dec 2007(+/- 20 years later) with Celeste, now 25 and Lauren 23 and the same Gentle Lady (20 years old and now without electric motor).

Lauren (left) and Celeste( holding the tail) taken in 1988

Yesterday 30 Dec 2007 (Lauren, 23 on the left and Celeste, 25 on the right

Celeste holding the Electra - 1988

Celeste holding the now Gentle Lady -2007

Over the many years that I have flown her I had many a long flight and some of them more than and hour in duration, and yesterday after revamping her for third time and on my third flight for the day got in another 45 min flight. (Pictures below)

One doesn't see many Gentle Lady’s around these days and I am not sure if it still is in production as a kit but I bet there must be many of them around waiting to have there wings dusted off ready to take to the sky again.

The 20 year " Old Lady "of on another 45 min flight-30 Dec 2007

Sunday, December 30, 2007

Volksrust Trip December 2007

A couple of us went down to Volksrust on Friday and Saturday and what a fantastic weekend it turned out to be. The weather man got it spot on. We arrived at the slope at about 08h30 and the wing was light out of the NE. So we went to the point. Robert tested the air with his Zagi, but alas there wasn't any lift and down he went. After an hours search we finally found his Zagi and headed to the Cross site.

There we found Lionel and Andre flying their light planes in the light lift that was blowing straight onto the slope. By 11h00 the lift was strong enough for Zagi combat with occasional lulls when a thermal would develop in front of the slope. Of course this caught Robert out again and down he went for another walk of shame. But, to his credit, he managed, on another occasion, to find the thermal that had blocked the lift on the slope face and worked his Spirit Elite back up from very low down.

All the while the wind strength was increasing and by 14h00 it was strong enough for all the heavies. Trevor, Kobus and Wesley had their Jarts and Trevor was first to maiden his. Followed shortly by Kobus. Unfortunately, Wesleys did not fly because of sticking ailerons. But these models really fly beautifully. Very fast and twitchy at first until the pilots got used to the sensitivity.

Evan on top of the rock outcrop posing the question: Where did it go?

The wind just kept getting stronger all day and we flew our hearts out. By about 17h00 we had all had enough. Power reserves were low in both models and body so we headed down to town to buy some groceries and then off to Oom Louis we went. A lekker braai with great company and the accompanying stories kept us entertained until bedtime.

The wind kept blowing all night and at one point was so strong that it woke me up.

The next morning we were treated to some fantastic espresso kindly supplied by Michel. One sip and we were wide awake and rearing to go.

After breakfast we headed back up to slope to be greeted by even stronger winds straight onto the SE slope. It was rather chilly in the wind and launching was tricky in the buffety conditions right at the lip. Hats and caps had to be tied or taped to ones head and wind breakers were essential.

Trevor, Kobus and Wesley had gone home the previous evening so no more Jarts to entertain us, but all the other heavies could fly.

Once again Robert (aka BJ - ask him how he got the name) did the walk of shame when his 'ill Billy went down.

Derek and Martie joined us for the day. So I'll leave the rest of the Saturdays rambling to Derek. He'll no doubt tell you about Roberts 6th "walk of shame" for the weekend.


Baudis Banana ready to goMartie and I decided last minute to go out to Volksrust for the day. Quickly packed breakfast and lunch, picked up my Dad in Heidelberg on the way and headed further south for The CampsiteVolksrust, The long grass along the roadside indicated a good breeze and a call from Evan already on the slope confirmed the wind was pumping on the slope.

We arrived at about 11:00 to join Evan, Robert, Michel and Lionel having some greatTito hovering inverted over the slope flying time. We set up camp next to Michel's Expresso machine on wheels and put the Tito up to test the air. The more I fly this little aerobatic model the more I am getting to like it.

Unfortunately the wind was a little too strong and gusty for the scale models. Neither Lionel or I unpacked our Discus models. But Evan was prepared to give his DG1000 a bash if he didn't damage the elevator servo extension lead. I have no doubt these little scale models would have flown well in the conditions, but there was not much chance they would have survived the landings. The rotor was vicious - standing facing the wind ten meters back from the slope face you could actually feel wind coming at you from behind!

Great though for the Zagis, Toko, Tito and Banana and it wasn't often there weren't any models flying. And other than a few hard landings (which most of the models flying could handle) there weren't any incidents or casualties for the morning.

Rob Street MemorialBut almost as if ordinary good clean fun is just never enough - after lunch Evan and Robert decided to head off with their Zagis to the "Street Bowl" - the area at Rob Street's Memorial where the wind gets compressed into a little bowl to produce phenomenal lift. After cleaning up around Rob's Memorial it was fun time and the Zagis were launched off into the stiff breeze.Evan and Robert at the 'Street Bowl'
Evan very successfully demonstrated an impressive manouver where from far out the model is dived downwind in towards the slope, is forced up the slope in the bowl The rock outcrop around which Rob's Zagi disappearedand then when overhead is pulled inverted and rolled out into the wind. Rob had fair success with the manouver as well but then seemed to get carried away with some other undefined manouver which took the model out of sight behind the rock outcrop on the left. Despite frantic stick twiddling and neck stretching, the model just refused to reappear.

So where did that Zagi go?Well, not much left but to partake in Rob's 6th "walk of shame" - but this time no luck. We searched all accessible terrain to no avail. I doubt the Zagi flew too far as Zagis don't fly too well on their own and I doubt Rob's frantic stick twiddling gave out the correct control signals for the required straight and level flight. It probably went down into the the thickest bushes on the steepest rock face and we just couldn't get in there. Just have to wait for the locals to find it and then fork out the reward money!

Back at the Cross site Michel lauched his Trinity and Evan his Prodij. A bit of slope racing and not long before the Prodij clipped off one half of the Trinity's V-tails. Evan managed to land the Prodij with only one operational aileron and the Trinity did a slow spiral down into the slope face. Amazingly the only damage to the Trinity was the broken V-tail.

Enough fun then, and with no sign of the wind calming so that we could give the Discus a try, everyone decided to pack up and head back to Gauteng. I believe Mike is off to the Volksrust slope over the New Year period - should be worth the trip to see that DG500 ELAN fly. Hope the conditions are good and best of luck there, Mike.

Friday, December 28, 2007

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,

Wednesday, December 26, 2007

Having some Fun Over Xmas Time.

Well after not falling for the reindeer food that I set out for Santa on Christmas eve, I manage to contact the overworked guy to stop in on Boxing day before his long flight back north.

He showed me his empty reindeer food bag (as you can see in the picture below).
However I quickly re-fueled it for him (hoping to score some brownie points) and hoping that he just might have one more Jart left amongst all his empty Christmas bags. But alas there was nothing.

There was one bag though, that looked quite full and rounded in the right places. He said that I can gladly keep this although it might not fly to well. So I offered to look after it (hoping to score some more brownie points). He also gave me his twin barrel hail gun and some cartridges and said that I might need it in the process, as nobody is going to Hi Jack a Santa with a empty sledge on his way home.

So not wanting to disappoint the dear old fellow, I agreed to all his terms and conditions and soon he was on his Sledge and with afterburners glowing Red Hot (sounds familiar) he disappeared in late night sky. A happy fellow with his work done for the year.

Obviously I was disappointed at not getting my Jart for Xmas but I could not wait to see what he did given me for Christmas.

So I rushed inside and this is what jumped out the bag!!!

Anyway, I will compete my Jart in the New Year and in the mean time, I am quite happy with this present.
Don’t get any ideas guy’s, remember the twin barrel hail gun !!!.

Wishing all the BERG members a happy and Thermal filled, New Year.


Thursday, December 20, 2007

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.

Tuesday, December 18, 2007

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.

Friday, December 14, 2007