Apr 012009
 

dl50-2

I was trying to get something flyable ready for this weekend’s Mount Spelga event. I also had been toying with the idea to start using the great outdoors in the backyard for some time. And I frequently find myself in far away places with some spare time, or driving home, wishing I could stop and fly on that nice field. Of course I have my Flash, but the thought of leaving a box of hot batteries in the car during the day is not that appealing to be honest. So, when Mr. Expressfly mentioned his encounter with a DLG when he was visiting Donatas last year, the seeds were planted. A long search resulted in finding some nice affordable kits in Germany. You can find the Spinning Birdie’s here. To my surprise, Richard mentioned he had ordered a handful of DL50’s from Mountain Models, and would I like one? Silly question of course. Anyway, workbench was cleared and the mind was programmed to ‘ready for Spelga’. My first ‘flights’ were performed on the day Matthew flew his Toffee Bomber. I can say that the performance of a 270 gram glider in a howling gale is ‘quite interesting’. However, it proved 2 things: It flew, and was controllable. I’ve since managed 3 decent sessions, and think I have the trimming sorted now.

As all things ‘new’, some of the things I did ‘could be better next time’. The building instructions are good enough, but let you down on a few critical places, so you really have to think things through before sticking bits together. The best of it all is, that I (re)discovered the backyard. Apart from the stunning views, it’s seems to have some nice slopes. Here’s the map. Driving North on Yellow road you will see a very steep valley, should be exiting flying in N and NE winds. The southern slopes are more to my liking at present, and allow more civilised access. The picture above was taken at the junction of Yellow Road and Mullaghgariff Rd, in the field on the east side.

There are a few rcgroup threads to have a look at:
RCGroups link1, RCGroups link2.

A few things I learned so far building this plane, in no particular order:

  • The tailboom can only go in from the front of the fuse, therefore do not add the nose block or the first former until the tailboom is in place!
  • The wings do take the longest to build, and take a lot of very gentle handling. Dints are easily created!
  • The whole method of adding the ply plates on top of the wing is very complicated, I did mine the other way around. (will describe in detail later, or if you can’t wait, email me)
  • I added cloth to the ply horns, they have a tendency to break.
  • The carbon fibre is actually covered in glue on both sides.
  • I used the lightweight B&Q filler to level the spars and any other imperfections.
  • B&Q has the required clear water based polyurethane as well as Bostik spray glue that does not appear to affect the foam if used sparingly. (use  polyurethane sparingly anyway. 2/3 layers on the fuse (and sand it back) gives a nice cover. 2 coats on the wing is ok too.
  • Polyurethane can be hard to paint. Some colours go on fine, (reds and yellows), others refuse to stick. On proper planes I would have sanded the polyurethane and applied a coat of primer. (This might be entirely due to my skills, so try your paint and your skills on a bit of scrap.)
  • Foam brushes? If B&Q does not have it, it don’t exist. I’ve always used ordinary soft brushes to apply this stuff. I’ve been using it for a long time to fuel proof balsa and to add to odd quick layer of glass to whatever I had in hand.
  • I ended up using a 3 cell nicad to get my balance right. So do not add anything to the tail section that does not need to be there. Why would you fly on three cells anyway? with 4 cells I would have needed extra tailweight. It’s me indoor legacy. Keep It Light, you can always make it heavier. Only 3 cells? You get very close to Rx dropout point. True indeed. Do carry a spare battery. 3 Cells only work reliably with old fashioned low current Rx’s! Do not try this trick with a single lipo cell and 2.4GHz equipment, unless you fully understand what you do.  
  • Hyperflight.co.uk has a very nice ready made lipo regulator. (suitable if you can fit your indoor 2 cell batteries)
  • 2.4 is a bit of a nightmare to fit actually, your antennae are hard to mount properly due to the small space available. (Standard Spektrum Rx’s)
  • Some people put the antenna in a wing (with suitable connector to RX-  35 MHz kit)
  • The CG as shown is EXCACTLY where you should have it. A millimeter is a LOT on this plane. Don’t think you’ll get away with changing it, you won’t. Which is really a ways of saying, get all your gear, move it around till you get the balance right, THEN fix things in place.
  • It’s like our indoor planes. First one is the heaviest and the one that has all the mistakes.. Don’t worry, we have lots of strong winds when you need all the weight you can get.

 

  • Think hard about the sequence of building the tail section. You can not add the stab/fin untill the boom is in and the wings are ready (Trust me!)
  • Do decide whether you like to throw left or right handed, and do read where you want to put your rudder-horns as a result.
  • See above and decide which side the hinge tape goes.
  • Reasonably important: Do sand the rudder/elevator down to airfoil-ish shape as described in the manual. It appears to make a good plane better.
  • If you don’t, you hear a nice whistling sound when you make a low speed pass. Remember, sound=energy.
  • Do add a few extra layers of glass to the very nose section (stagger a few bits, I added 10 cm to the bottom, less to the sides. ) Actually, On the next one I would add a 45 degree and a 90 degree layer to the whole pod. In our climate you will need the weight (very little) and it will give you some extra strength during the early days.  
  • Also add additional glass on the wingtip that does not have your peg: It will hit the ground during your initial throwing trials. Since you need weight on that side anyway, you might as well put something useful on it.
  • Yes, it NEEDS to be laterally balanced! Even so, mine needs right rudder to offset the drag of the leftwing mounted peg. (That’s my excuse anyway)
  • The plans are not clear but you are better off extending the push-rod tubes all the way into the servo bay. The supplied tubes are long enought for this. This means making the holes in the formers  bigger. You will be very grateful you did if you ever have to repair the back-end of the pod. Superglue will find it’s way into the push rods!
  • I flew mine with 100 gram ballast on Buttermountain/Spelga. Don’t expect aerobatic performance but it flies and stays up as long as your fingers hold out.
  • Make some lead weights to sit besides the tail-boom at the CofG. Biggest I could fit on one side was 60 gram. I made another one of 40 gram, which give me 4 choices. 280, 320, 340, 380 grams.  (Actually a tad less, but it’s close enough.)  280 gram is the no lead, the heaviest 2 are not for DL launches!  (not yet anyway, need a bit more practising)
  • The bottom of my throwing wing shows some slight creases, obviously due to my less than perfect launching technique. On the next one I would double the bottom glass. Weight is a none-issue, but it will give you additional strength where it is needed. It will also look better then my patched up version. When the manual talks about making a diamond shape for the center, I would use the pointy bit on the outside wing, but use the full length on the throwing wing.
  • My definition of throwing wing: wing that has the peg.
  • I put a bit of heatshrink tubing on the peg to save my fingers. I know, weight!

More as we learn, and still lots of fun. The sad and dangerous thing is, that you will soon discover that DLG’s are quite addictive. So be aware, you have been warned!

Kees

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