Balsa DLG

[ThomasMartino]

I’m taking a break from my other build to work on a new DLG. I’ve built two other DLGs and they both came out heavy. The main objective is keeping the flying weight below 250 grams. I’m using balsa since it’s the easiest material for me to build lightweight structures with. My last two were two channel gliders with rudder and elevator control. This time I want flaperons so I can adjust the camber of the airfoil.

 

[ThomasMartino]

I started this project yesterday morning. The first thing I tackled was the tail boom. I used a carbon fiber arrow shaft for the boom on my first DLG, and a regular 8mm carbon fiber tube on my second. This time I want a tapered boom that will be lighter and have less flex. It will be made out of balsa and carbon fiber.

I’m using a small pool cue as the mandrel. I started by wrapping a piece of 0.034” balsa around the mandrel. I sprayed the wood with veneer softener to make it more malleable. Soaking it in warm water also would have worked. Taping pieces of paper to the mandrel helped me tightly wrap the balsa. Once it was wrapped and secured with tape I left it to dry for a few hours.

Once dry, I gently unwrapped the tube enough to slide it off and remove the paper. I glued the seam with regular Elmer’s glue.

 

[ThomasMartino]

Next I sanded the seam to create a perfectly round and smooth tube. I covered the mandrel with packing tape and applied three coats of release wax to ensure the tube doesn’t get stuck during the next step.

I’m using Textreme spread tow carbon fiber tape to cover the tube. It’s very thin and light unidirectional carbon. There is one layer oriented lengthwise. I put the assembly in a vacuum bag to guarantee a tight bond with the balsa and remove any excess resin.

After that cured I lightly sanded it and applied a second layer. This time I wrapped the unidirectional tape around the tube to add hoop strength and torsional stiffness. I tightly wrapped the layup with electrical tape to clamp down the carbon while the epoxy cured. Here is it after removing the electrical tape and lightly sanding the surface to remove some of the ridges.

the finished boom is 35” long, 1.58” diameter at the wide end, and 0.575” diameter at the small end. 31 grams.

I soaked the balsa near the end with thin CA to reinforce the area where it will mate to the fuselage pod.

 

[ThomasMartino]

Today I’m working on the wings. The wingspan is 60”. The planform shape is a slightly modified ellipse. The root airfoil is AG45 and it blends to AG47 at the tip.

 

[ThomasMartino]

It’s late and I’m tired but the wings are done! I love those curves.

 

[danskis]

Very impressive build! That looks great and I love the curves. Its a classic DLG.

Wingspan = 60 inches? 5 feet? I think most DLGs are 1.5 meters or 1 meter but I could be wrong.

 

[ThomasMartino]

Very impressive build! That looks great and I love the curves. Its a classic DLG.

Wingspan = 60 inches? 5 feet? I think most DLGs are 1.5 meters or 1 meter but I could be wrong.

Thanks! 1.5 meters is 4 ft 11 inches so it’s basically the same. I just prefer working with imperial units.

 

[ThomasMartino]

Horizontal stabilizer framing is almost done. I’m using the HT14 airfoil which is well suited for tail surfaces.

 

[GliderFlyer]

I started this project yesterday morning.

Dang, this build is going fast!

 

[ThomasMartino]

Dang, this build is going fast!

I’m hoping to finish it in another day or two. I’m really pleased with how fast it’s going.

 

[ThomasMartino]

Well this is disappointing. I added some cardstock reinforcement to the trailing edge and it doubled the weight of the stabilizer. It weighs 9 grams now.

 

[ThomasMartino]

Covering film added another 3.26 grams.

 

[hsquier]

Hats off !
What a lesson you give ! Wow, very impressive.
Like you my first DLG experience was a two channel (A flyECM kit of Mark Drela's Apogee). It was already one of my best RC experience. And adding ailerons pushed the pleasure even beyond. I have no doubt on the flying performances, it's already written : you will have good time !

I will watch with great attention how you will mount the stabilizer on the boom and the pod installation.

Hum !! Multiple simultaneous RC projects ? We are definitely in the good forum section .

 

[ThomasMartino]

Hats off !
What a lesson you give ! Wow, very impressive.
Like you my first DLG experience was a two channel (A flyECM kit of Mark Drela's Apogee). It was already one of my best RC experience. And adding ailerons pushed the pleasure even beyond. I have no doubt on the flying performances, it's already written : you will have good time !

I will watch with great attention how you will mount the stabilizer on the boom and the pod installation.

Hum !! Multiple simultaneous RC projects ? We are definitely in the good forum section .

Thank you! Discussing DLGs with you in my other thread made me want to build another. I love working on multiple builds at once. Stepping away from a big project once in awhile is important. It keeps me inspired.

Your Apogee looks beautiful. Mark Drela sure is a genius. I love two channel gliders but I’m excited to finally have ailerons.

I mounted the stabilizers earlier tonight. I will post pictures tomorrow showing how it was done.

 

[ThomasMartino]

Yesterday the weather was too good to stay inside working on the plane. Today is cold and rainy. Perfect building weather!

I finished the fin and mounted it to the boom. The trailing edge is reinforced with a strip of 1/16” spruce and the bottom corner that will touch the ground on landings is reinforced with 1/16” birch plywood.

 

[ThomasMartino]

This is the pivot mount for the horizontal stab.

 

[hsquier]

Addict to your ultra neat job.

Thank you ++ for the photos. Simple and efficient (an other of your characteristic I noticed in your build) . Allow me to copy you !

I have a question :
How do you determine the location of the pivot on the horizontal stabilizer ?

Just for fun as I was talking about it : FlyECM Apogee wood kit :

Already 2009 !! wow time flies !
I had a lot of pleasure to build. And still flies (on 27 MHz !!).
The very well made kit allowed me to reach 114 gr (4,02 oz), leading to an surprising 9,7 gr/dm2 (182 sq inch) I could never manage to get again.

You were speaking on weight.
I was totally obsessed by weight and still totally obsessed by weight, but :
Interestingly my molded Apogee (2020), plain copy of the wood one, is heavier : 128,5 gr (+ 10%, 11 gr/dm2) but flies surprisingly equally well : +/- 45 sec in total dead air for both of them ...
My last DLG is far more on the heavy side (13,5 gr/dm2) but flies still very well with an mean of 55 sec in total dead air (I don't know for you but to me 60 m DLG launch is science fiction).
At these level of wing loadings perhaps it deals with low end speed more than with sink rate ?
... hard to know really what to think.

 

[GliderFlyer]

This is the pivot mount for the horizontal stab. View attachment 192869 View attachment 192870

How long did it take to cover that tiny pivot mount? I probably would have just left it a part like that uncovered. It looks nice though.

 

[ThomasMartino]

The only major tasks left are installing the pushrods and making the fiberglass pod.

 

[ThomasMartino]

The guts of the plane added a staggering 78.56 grams. The total weight is now 277. My goal of a 250 gram flying weight won’t be achieved, but I’m sure it will perform admirably even if the flying weight ends up at 300. I could save a few grams by cutting down the servo wires and soldering them directly to the receiver, but I need extra nose weight for balance so there’s no point.