DLG - NRJ build log

[hollopeter]

Hi all,

I lurk here a lot but have only posted a couple times. I've been flying off and on for years and am looking for a new thing to try. I've watched David Windestal's Flite Test DLG video way too much over the last few years and have done a lot of other research in the hopes to purchase once and not do a slow upgrade over the years spending more and more. So I took advantage of the current exchange rate (thank you Brexit) and got a full carbon DLG from Hyperflight in the UK. It's a 1.5m NRJ. I believe the producer is Anton Ovcharenko from Ukraine. There are a few distributors here in the US but they are all sold out at the moment.

Full disclosure = I am a total DLG rookie (minus tossing an eFlite Whip-it around) and just got it to go fly, at first, quietly at the local ball fields. No F3K competitions planned yet but maybe I'll need a challenge in the future. The minimalism of a DLG looks like a huge amount of relaxing fun. Plus - they seem to hold their value pretty well so if I want to sell it down the road (in good shape), I shouldn't lose too much of my investment. Not something I can usually say with my meager fleet these days.

So... I will do my best to document the build. This is also my first build of a glider that is unpowered and needs more attention to detail than the couple Horizon Hobby sailplanes I've had in the past.

Ordered from Hyperflight in the UK on June 5th. A blue/white NRJ with their 'standard' carbon layup (there are also light and strong versions) plus 4 of the recommended servos. They were fast in communication and gave me a tracking number to follow it through local shipping, customs, and through customs in the US. From there, the tracking number went quiet but only a day or so after the last update it arrived on my porch.

I didn't get a picture of the unboxing, but it was well secured in a couple layer thick corrugated cardboard box and all parts were bubble wrapped and taped together spaced to sit in the middle. It arrived safe and sound without a scratch. I'll take some pictures soon with all parts on the scale and post them but I wanted to get the tread started and force myself into good documentation! There are a few build logs out there but most of those know what they're doing so I thought I'd add some rookie experience to the internet.

First impressions are WOW the build quality is really nice. And even though I knew it would be lightweight and tough to package, I'm not sure I realized quite how much lightweight and tough. The receiver and battery I pre-purchased may not both simultaneously go where they need to. The servo tray and servos in all of the instructions I looked up were photographed fairly close so I didn't realize how tiny they are.

Weights -

Fuselage and nosecone - 39 grams
4 KST X08 servos - 35 grams
3D printed servo holder - 5 grams
Turnigy 1S 750 mAh Lipo - 19 grams, though I need to find a smaller one or a longer/thinner one.
Spektrum AR410 4 channel Rx (without plastic case - it won't fit unless it's stripped down) - 3 grams
Horizontal stabilizer - 5 grams
Rudder - 6 grams
Wing - 91 grams
Miscellaneous bag-o-hardware for assembly - 12 grams.

By my math that's 215 grams total minus the little bit of glue I'll need. There are also ballast weights that (I think) are used to help in windier weather but a set for about $50 seemed pretty steep since all it looks like is adhesive wheel weights shrink wrapped to specific lengths of wires. I think that should be easy enough to reproduce for a tenth of the price but I'll cross that bridge when I get to it.

I'll start the build tonight!

 

[hollopeter]

First trip to the hobby store since quarantine started yeilded a better shaped battery in the form of a Dromida 650 mAh one cell. And it's a couple grams lighter. Gotta figure out how to get it to connect to the Rx. More on that in a minute. But it should fit up front with the small Rx.

Sanded down the servo box so it would fit in the fuselage without bulging it and did several test fits until it was snug. Measured and marked it's recommended location. There seem to be two schools of thought to the servo installation with one being to install them and tack the wires in place along the outside edges of the box the wires with a little adhesive. The other is to epoxy the box in place (need to pick some of that up) and then feed the wires forward after installing the servos. To do that, you need to take the terminals out of the connector, feed them through, then put them back in the connector. I think I'll do the former but need to verify everything works first. There was a slightly overzealous kid helping out and the wires of one of them got pinched and dragged around a little on the workbench. I can see a little metal where the insulation peeled away but it doesn't look like more than one wire and it doesn't look frayed. A little electrical tape or a thin spread of hot glue will solve the problem if no shorts have occurred. Still - I'd rather know now than later that it works - once these are in, they aren't coming out! So that will delay things a bit.

Now... onto the receiver problem. Which would help me check the servo. I bound my Spektrum AR410 to my Tx a few days ago using an ESC I had lying around. No issues once I realized I had to hold the bind button on the Rx for a looong time before it would hook up. I won't have an ESC on this and had heard that I could directly plug into the Rx with the battery since it's a low voltage (3.7) and it should power the receiver fine. No luck. And no light indicating power. No problem - get out the ESC and a bigger battery and do like I did to bind it to check the servos. No light. Uh oh...

Sent an e-mail off to Spektrum to see what's up and will go from there. For now, I'm dead in the water until that gets sorted out and I can check the servos. Or just go back to the hobby store and get a servo centering tool.

 

[hollopeter]

Day 2 - not a whole lot, only got an hour or so of work in but some progress.

Got my AR410 Rx woes figured out with a little online chat help from the folks at Horizon Hobby. It somehow lost the bind but if you hold down the bind button on the Rx when you power it up you can re-bind like usual. Also confirmed the minimum voltage needed to power it up (3.5V). Used a bigger 2C battery and the old ESC to power it up and check the servos were ok (yes!).

With all that figured out, I used a small amount of hot glue to route the servo wires through the servo box outer 'gutters' and installed it all into the fuselage, setting the rear face at 23 mm from the opening per the instructions and secured it in place with a thin layer of 30 minute epoxy.

While that cured, i hooked everything up to the Rx (minus the battery) and started fiitting that and the battery into the nose. There is NO room for anything else, but it'll fit. After verifying that it will work, I pulled the battery out, snipped the connector off of it and soldered/heat shrinked a servo type connector on it so it's the same as the rest to plug in. Then I scavenged through old wires/connectors and fabricated a pigtail so I can charge it off of my 1c E-flite charger since my 'big' charger needs a balance plug to do anything.

Lots of tedious work, but nice to make progress. Next step is linkages.

 

[hollopeter]

Day 3!

A good few hours today, though it's still slow progress.

Carved out 1.5x25 mm slots at the inner edge of the ailerons for the control horns as well as the foam underneath the carbon fiber. It went pretty easy - it's only one layer thick with a foam core but I'm amazed at how strong the thing is. Then a tiny bit of oil up on the small bit of exposed kevlar hinge.

The horns were put on with a little foam safe CA (the instructions said regular, but I don't want to risk the foam dissolving) and then some 30 minute epoxy to fillet the outside edge of the horn to the aileron. A couple of strips of tape on the opposite surface kept any spill over from accidentally gluing the aileron inner edge to the wing. Once everything cures I will need to sand a little bit of the run over to make sure the aileron still moves freely.

Then I mounted the wing to the fuselage - well, I tried. The rear screw lines up without a problem but the front is a bit off center so it wouldn't start. Fortunately I didn't strip the screw threads and I'll enlarge the hole a bit from the bottom before mounting it all the way so the front screw will go in fully. But with the rear tightened and a little tape up front I got the wing seated and measured out what I needed for the control linkages and sleeves. That's going to take a bit of acrobatics to finally get installed - it is, like everything else on this, a silly tight fit. I even had to bevel the tops of the control horns at the servos so they'd fit under the nose cone without rubbing!

Everything is ready to mount the wing tomorrow, but I want the CA and epoxy to cure fully. Then a couple test fits to make sure I can screw the wing down and then it'll be a bit of ballet - control linkages in the aileron horns, slide everything up, control linkages into the servo horns. Screw the wing down.

At least that's the plan, we'll see how it goes tomorrow.

 

[bracesport]

@hollopeter - looks great - I have been enjoying the DLG thing lately, you will love the thrill of the first launch!

 

[hollopeter]

Day 4 - Good progress today and I'm going to quit early, let things cure up overnight, and go get ice cream with the kids.

Bored out the wing mounting forward hole a little bit and both fasteners now thread in smoothly. I undid them, promptly lost the rear one (I'll do a sweep up tomorrow morning and go to the hobby shop tomorrow for another one if I don't find it. Super fine threads!), hooked the linkages to the aileron control horns, and started jockeying things forward. I got close, but one of the horns pulled out, so I re-scuffed it up, new epoxy, and I'll try again tomorrow.

Back to the fuselage - for the rudder and elevator, you have to cut a slot in the rear face of the elevator mount to pass the control cables through, so I drilled and Dremel-ed it until I had a passthrough.

I figure out which way is which on the rudder (it is ever so slightly different left to right), dry fit the elevator, lined up the rudder at 90 degrees, and put an absolute minimal amount of epoxy on it to set it in place. Once it was finally set, I also dripped some thin CA around the mating surface and it wicked in and at least made me relax a bit more about the joint strength. The instructions emphasize as little mass out back as possible to get the right CG. For both the rudder and elevator control horns, I taped over the carbon fiber and cut 0.5x20 mm slots, cleaned out the little bit of foam in there, and CA'd them into place.

I'm continually amazed at how strong this is with the absolutely tiny layer of carbon fiber that's used. You have to be sooooo careful not to poke through when digging around the slots with an Xacto knife.

Finally I bent two 0.3 mm rods in a C shape with the legs of the C about 45 degrees apart from each other. Then shoved them into either side of the rudder and elevator to create a small torsion spring so you only need to do a pull cable that's always under tension up to the servo. Super elegant solution and I will use that trick again.

 

[hollopeter]

Day 5 - tight spaces and tight bends

Taped the rudder in neutral, made a loop and crimped the tiny crimp sleeve in place going through the control horn, then ran the braided steel line up to the servos through the hole in the elevator mount. With the plane powered up and the radio on, I set the rudder spacing then played around for a while trying to bend a linkage in the right shape. Once that was set, I installed (for the last time) the rudder servo horn and linkage and tightened the cable through the linkage and crimped another loop in place. It wasn't perfect, but close. Some radio subtrim solved that. Set the travels per the manual.

The elevator was a very similar process, though I tried a shorter linkage this time.

Cut a hole in the left wingtip for the launch lug. After a few frustrating minutes with the Xacto kife, I discovered I needed the dremel for that one - full carbon all the way through, no foam. Tacked it in place with a little thin CA, then epoxy around both sides, top and bottom.

Left to do is counterbalancing the launch lug, mounting the wing and control rods, setting the CG, and making ballast sets.

I did spend a long time looking for the wayward wing screw but no luck. Local hobby store to the rescue and now I have 4 more that I can lose!

 

[hollopeter]

Day 7 - no posts yesterday, but excellent day nonetheless.

After some frustrated head scratching trying to get the battery and Rx in, I had to dig out the picture I took that at least proved it could be done. Once I got past that 'hey, moron' moment, I connected everything, slid the nosecone on (a little friction, but not bad) and... well, guess I'll head to the field! Sunny, not much wind, doesn't get much better.

Did some paper airplaine style tosses and attempted to trim it out. Then there was nothing left to do but try a discus style launch. It went zooming off towards the horizon, gaining virtually no altitude. But at that speed, I was able to get it to circle around and come back close-ish to me. I dialed in some up elevator trim and did a few more launches, gaining good altitude now and was able to push the trim back to neutral - figure out the flight modes on the bench at home later.

Spent the next half hour or so working on my launch technique and seeing how long I could stay up. LOTS to learn here, but I'm getting better each time up. Trying to pay attention to how the plane twitches in the sky to see if I could pick up a thermal.

At home now, dialing in flight modes on my DX6e and looking for a tutorial somewhere out there that can guide me better than my 'mash buttons until it works' attempts. Got an elevator up launch mode and a flaperon landing mode figured out. Might go try those for a while before seeing what the cruise, speed, and thermal mode needs.

"Just one more toss" is really hard to ignore. The only thing slowing me down is the Rx battery monitor. at 3.6 volts I call it quits.