skater_719

My Feedback: (4)

After many years of powered flight, I have caught the glider bug, I have a couple electric gliders, that I have a blast flying. Lately I have been looking into DLG's and have a few questions about building one. From my experience it seems when it comes to thermalling, generally bigger is better, but would enjoy something small for the back yard, and something I can keep in the trunk for spur of the moment flying. I would really like to build a small dlg, between 30-40". First thing I am having trouble deciding, is what material would be the best to use. For the wing I was planning on using 1/4" balsa sheets and just sanding out the airfoil, seems for the simplicity and weight, wood would be the way to go, but I have never built anything like this, so do you guys think any composites or foam would be more weight friendly and rigid? My biggest undecided material is the fuse, I have not used composites before, but I have been wanting to give it a try, I'm worried balsa would be a pain to get to bend for the tight compound curves a micro glider fuse would entail, which is making me think carbon fiber would be more reasonable. The setup I plan on using is a Hitec electron reciever, with a 100mah 1 cell lipo, and 2 nano servos for either V-tail or just classic rudder elevator setup, another undecided part, are there any advantages between the two? Which would give more authority since there wont be any prop blast to help? Feel free to share your Micro Dlgs if anyone has one. Hoping to start this project within the next couple days. Thanks for any advice

BMatthews

There's lots of options. But for now check out the Charles Rivers site and Mark Drela's Apogee at;

http://www.charlesriverrc.org/articl..._apogeehlg.htm

It's intended for direct javelin like hand launching but I suspect it would be pretty simple to convert to DLG. The big first step would be to convert it to a separate vertical and horizontal fin design instead of the V tail. The more regular style setup seen on many DLG's would tend to damp out the yaw during launch more easily.

skater_719

My Feedback: (4)

Well i went ahead and built the apogee 36" and had serious cg issues with it being tail heavy due to using 4.6gram servos and such a light lipo reciever battery.i really hate adding weight so i experimented with removing the tailboom and tail to make it into a flying wing, and added a rudder off the back of the pod, and put 2gram servos in the wings.for elevons. It now can achieve a good range for the.cg.dependimg on reciever and battery placement. I started off with the cg far forward for.the first toss and had almost no elevator authority, so af

skater_719

My Feedback: (4)

Well i went ahead and built the apogee 36" and had serious cg issues with it being tail heavy due to using 4.6gram servos and such a light lipo reciever battery.i really hate adding weight so i experimented with removing the tailboom and tail to make it into a flying wing, and added a rudder off the back of the pod, and put 2gram servos in the wings.for elevons. It now can achieve a good range for the.cg.dependimg on reciever and battery placement. I started off with the cg far forward for.the first toss and had almost no elevator authority, so after many cg adjustments it just does not seem like i.can make it stable, its either insanely.sensative or completele mush. I guess such a small chord is not.helping. I have an idea for.a small horizontal stab on the rudder and or a canard style serface in the front. Any input would be appriciated. Btw i have tried al different amoumts of throw and expo settings.with no luck

soaringrace1955

There are a few good threads on micro dlg also a few small gliders for sale.

soaringrace1955

Whoops didn't add they are on RC Groups

BMatthews

Skater, you're not able to make it stable because the airfoil has a negative pitching moment. That's why the tail was on there in the first place. To make a plank or very low sweep angle flying wing you have to start with a whole other airfoil that has a postive pitching moment. Airfoils with this trait act like the combination of a regular airfoil with a rearward stabilizer.

If you set up the wing with full span elevons you can "fake" the reflex in such airfoils by trimming in some amount of up trim to the surfaces. Aim for a balance point of around 20% back from the virtual leading edge of the MAC (Mean Aerodynamic Chord) and keep adding up trim to the surfaces until it glides well.

qldviking

I just saw this thread, and got curious. regarding the pitch attitudes when you go tail-less, try trimming both ailerons up about 3-5 degrees for normal trim, you may need more or less depending in chord and aileron size

Cloudsoarer

Take a look at the Mimi - an updated version of the Apogee.
Similar construction but more wing area and DLG tailset.
Weight is very important in Mosquito class DLGs, as you can see from the Apogee weight budget.
Modern batteries and receivers have helped considerabvly in this since the Apogee was designed, provided you use a longer nose and very light tailset with a wrapped carbon boom.
Correct balsa densities and careful construction are required to make a good small DLG.
The Apogee and Mimi need sub 5lbscuft balsa which is largely unobtainable. Therefore various built up balsa wing constructions have been designed from solid D boxs to sheeted D box with ribs. Also light .75 ounce glassed foam wings are good either hot cut or sanded, using either epoxy or polyurethane.
The Bug is another quick construct possibility with a lesser performance.

skater_719

My Feedback: (4)

I lnow its been a while, but. I added full strip ailerons with.some up trim and can finally keep it flying although.its been a challenge to find any lift with it.