da Rock

The running test gets two thumbs up (and both big toes) from here.

It's amazing how much you can feel just jogging into the wind. You can see it too. And it doesn't even have to leave your hand. Once you got a 'feel for it' (no lie), and it feels right, just pushing it off to glide on ahead gives you a good amount of time to set the elevator trim. You will discover however, that you need a fair amount of runway for the glide part of the test.

Doing it with the motor gliders of today works too. The last couple of times I did the trot and push with powered sailplanes, they were good with their elevator trim, so I just rolled in some throttle. They were good to go so go they went.

Nodd

Maiden Flight Video
Well you've all been asking for this so here's the video. Enjoy...

http://youtu.be/Gyn1AmESRSM

Nodd

Maiden Flight Details
Well the video was fun but I left out a few details. So before you ask...

I used a 2100mAh 3S battery. I landed after 15 minutes not because the battery was getting low but because I didn't want to push my luck on the first flight. I believe I made four, maybe five, climbs during the flight. The battery was at 11.02v when I checked her after the flight, so still had plenty of juice for a few more climbs.

I didn't try to do any thermalling, instead the flight was spent playing with the elevator trim mostly, the rudders & ailerons didn't need trimming. You may notice at the end of the video I show there's maybe an 1/8" of up trim on the ruddervators. The tail was mounted at 1° to the plane's datum line. In hindsight it could probably have used a tad more incidence.

You can't really tell in the video but the flaps & crow mixing were pretty effective. I tried them out while nice & high. It produced a fair amount of ballooning when I dumped in full flaps but that's to be expected. Fed in slowly & with the down elevator I mixed in, the flaps behave nicely. I put them to good use in my rather over extended landing.

Currently I have very little crow mixing, the ailerons move perhaps a 1/4" up at most. I'll play with it more but I think I'm going to stick with the flaps as the main speed brakes so that the ailerons don't get all mushy on me.

Important safety tip! DO NOT mess with the trim when you're 20' off the ground & in a hard turn. Not sure what I was thinking but as the video shows, I took my eyes off the plane for a split second & almost sent her piling straight in. I'm SOOOO glad I was able to recover in time, would never have forgiven my self.

Some may have noticed my ESC was set to slow start. I did this just for the maiden flight. I thought without a proportional throttle it might be nice to have the motor spin up to speed gradually instead of all or nothing. I'll be setting it back to normal after I'm done messing with the throttle to elevator mixing.

The middle position on my three-way throttle switch was set at 30% thrust. Turns out that's pretty wimpy. I think I'm going to increase that to 50%. At 100% she climbs out very nicely though. I think I may have nailed the motor/prop combo.

I will be producing plans for this sailplane. I'll let you all know when those become available.

Anyway that's all I can think of for now. Thank you once again for following my build & a HUGE thanks to those who offered advice.

rhall999

AWESOME Nodd!!! It looks really nice all finished in the transparent red and white. Looks like it flys as nice as it looks too. Excellent work!!

checksix

My Feedback: (4)

This was one of the best documented design-build-fly threads I've seen. Nice job, and congratulations.

highfly3D

nice video also liked the build..

Nodd

Change of Plans
Some people have been asking when the plans will be available. Sorry to report it'll be a little while still. I need to rework the wings. I'll get into the juicy details shortly but basically there's a major problem with the current wing design. I'll post more about that soon, my apologies for the delay.

Nodd

I'm going to redesign & build a new wing for this sailplane. As this thread is getting rather long I've started a new one here...

Sailplane Wing Design Round II

Mango73

Nodd,

Greetings from near Seattle from a former Connecticut (Ledyard) resident.

I read your post showing a Duo Discus in the background of your designed and built balsa/carbon sailplane. I am just starting my design efforts to build a 1:4 scale model of a Duo Discus XL sailplane. I am creating a three dimensional computer model in AutoDesk’s Fusion 360 software. This same software will then create the G-code to drive a CNC machine to carve the various parts. I will make molds from the parts and the produce the actual model plane in FRG. Today, I am in the initial stages of computer modeling.

If you would respond and possibly assist me, I would greatly appreciate your efforts. Your bog is impressive qnd you have obviously been "around the block" on this a few times. My questions are below. Thank you in advance.
1. Can you tell me a source for accurate Duo Discus XL drawings? The only two dimensional drawings I can find are small and limited to top-down, front, and side views. Additionally, there are some drawing in the operations manual that I down loaded from the internet. When I overlay vector lines on top of the raster image and scale these drawings, I find the shapes do not agree very well. Close, but for example I have five overlays of the portion forward of the wings. The (worse case) disagreement between the outer most and inner most profile line in 10 mm on the 1:4 scale drawing. This equates to 40 mm or a little over 1.5 inches on an actual sized plane. Other examples of difficulties are that the drawings of wings show only approximate locations for the dive brakes and the locations and widths for the flaps and ailerons.
2. Similar question as #1 for the winglets. I can find no information about the size, shape or cross section of the winglets.
3. If you have built in fiberglass, can you tell me a suitable cloth stack for the fuselage, for the wings, etc.? If not, any good source(s) where I could learn how to decide cloth layers to use, where to reinforce with carbon, etc.? I will use epoxy resin.
4. Same question as #3 but for strengthening FRG parts by incorporating structural foam sheet (maybe 1/8" or 1/4" thickneses).
5. Do you have a favorite form of wing spar? What form of receptacle in the fuselage do you construct to receive the ends of the spars?
6. Where did you install the antenna(s) for the 2.4 GHz receiver(s)?
7. You are using the 7037 airfoil for your wings. Any particular reason why you are not using the SD7035 (Selig/Donovan low Reynolds number model sailplane airfoil from the University of Illinois Urbana/Champaign Airfoil Coordinates Database)? Unless I find better information, I intend to use the 7035.
8. Any info of the exact location of the Duo Discus Center of Gravity or ideas on where I might find this?

Thanks so much for any response and help.

Mango73

Nodd

Hello Mango. This is not relevant to this build log so I've answered using a private message.