Posted on by — Leave a comment

DIY RC Glider – The Lull DLG Build Guide

[DIY] DLG Glider - The Lull Build Guide

Looking for a guide to the Lull Balsa DLG build?

You are in the right place.

Lull is a beginner-friendly DIY DLG Glider that you can build yourself from balsa, carbon, and plywood parts provided in the kit 🙂

The build is relatively simple but would require basic skills for working with wood and essential DIY tools.

There is nothing too crazy though, so if you are just starting with discuss launch gliders – it is a great choice.

Below is a step-by-step guide on the build with some tips to make it less stressful.

For more tricks and tips on the build, check this RCGroups thread.

Of course, feel free to share your build there!

Before You Start

You’ve got the Lull kit – that’s awesome!

It will make you an airframe but you will need a little more.

Make sure you have all the tools and RC gear for the future glider and have it handy.

Prepare Your RC Gear

The Lull offers a wide variety of RC choices due to the large pod, so please, set aside:

  • Two servos up to 9g. HXT900’s are a great choice, but consider something smaller and more reliable if you have a budget
  • Rx Battery. We recommend a ~500mAh 1S LiPo, similar to what is used with indoor whoop drones, that has a great capacity for the weight and packs inside nicely.
  • A micro PWM radio receiver that has pins for direct servo connection, and will work with your Radio Transmitter.
  • A pigtail for connecting the battery to a receiver. It can act as your power switch as well eliminating the need to install another component in the powertrain.

Prepare You Tools And Supplies

To help you with the build, please, prepare the following essentials:

  • A sharp model (or paper) knife
  • Medium and thin CA with kicker
  • D2 or D3 PVA glue
  • Masking tape
  • Diamond files
  • Tweezers
  • Pliers
  • Flathead and Phillips-head screwdrivers
  • Sandpaper
  • Kapton tape, or the other sticky tape that you prefer.

You will also need a model covering film and the tools to work with it.

Scissors, covering iron, etc.

If all that is ready, let’s go straight to the build.

Part 1. A Wing

We recommend starting the assembly with the wing, as it will be used for the tail alignment later in the build.

Pro Tip: Use a clean flat surface for assembly. The wing ribs have a flat bottom tail shape, so you can position them flat on the plan and apply CA to fix them permanently.

Also, thin, medium CA, and PVA D2/D3 glue are handy for this stage. Use PVA for wood-wood connections and CA for wood-carbon connections.

Also, installing the main spar first,  the trailing edge next, and the leading edge last in the exact order is important.

This will help you prevent bending the main spar during assembly.

Find all the wing ribs and half ribs and put these onto the 5x4mm tube from the kit in the correct order. Each rib has a number that will help you with this taslk
Then, prepare your plan by applying a clear sticky tape over the areas where you will apply glue. This will prevent the wing from sticking to the paper
You may notice that the ribs on the plan are not perpendicular to the main spar
So either one by one or in small groups by 5-6 pcs, gently squese the ribs to set a required angle
Start with gluing the “full ribs” in leaving the “half ribs” unglued
Also, make sure to keep L1+ and L2- unglued as well
Next fix the trailing edge in place
Install the wing tip
Now, install the leading edge glueing it to the “full ribs” only at first
Fix the leading edge on top surface of the wing tip, apply CA and kick it with kicker to cure fast
Now, you can finally position the “half ribs”and fix them in place with CA
Use a piece of scrap 2mm balsa and create a stiffener on the last rib to reinforce the leading edge connection. Pay attention to the grains alignment for the best result
Install a plywood launch peg reinforcement
Use CF tube wing joiner to align the L1+ and L2- reinvorcememnts and glue them to the corresponding ribs. DO NOT GLUE the CF wing joiner part yet!!!
You can use PVA glue for his tals as it doesn’t stick to the CF and will give you more time to remove the latter
For right-hand launchers, soak the Left launch peg opening with a thin CA
Do that on both sides.
Prepare the top root sheeting by glueing its parts together
Then, install it onto the wing and fix in place
Repeat every step above for the right wing as well
TEMPORARY install the wing joiner in place to check how both wings join together
Use a sand paper over a flat surface or a big sanding block to raper the edges of the wing sheeting
Join the halves together and make sure that there are no gaps. Take this part slowly
Install wing bolt holders in slots of the root ribs
Make sure these are centered and enlarge the wing bolt openings in the sheeting to make a space for the wing bolt coming in and out freely
Trim the trailing edges to be flush with the root ribs
Use a flat surface to align both wing panels by the root ribs
After making sure everything works as expected, apply glue to the edges of the sheeting and the CF wing joiner
Use scrap 6mm balsa to fill in the gap between the roob ribs on the rear and under the wing bolt holders. There are also parts marked with WBF which you can use here
Sand the fillers making them flush with the ribs
Do that on the top side as well
Protect the ribs with a few layers of clear sticky tape before sanding the wing tips
Round the edge and taper the launch peg reinforcement slightly
Pay attention to the bottom surface as well
Soak 30-40mm of the rear part of the wing ribs with thin CA to prevent it bending under the load of shrinking covering film
Cover the wing and make openings for the wing bolts. Hot soldering iron tip might help here
For right-hand launchers, jpen the covering on the left with tip for the launch peg
If using stickers, cut them in parts
Then, position and apply to the wing where desired
Cut the launch peg from the 5x4mm CF tube. For strong launchers, use 5x3mm tube instead
Round the edges and push it into the wingtip opening. Then, make a healthy fillet around it with a medium or thick CA
(Optional) Add up to 3° of wash-out to the wing tips, to improve the wing performance and stall characteristics

Part 2. A Fuselage

Prepare the parts and assemble them as shown in the pictures

Start with installing the wing mounting nuts
Install the wing mounting bolts and screw the nuts on all the way. Turn tight
Install the wing nut holders making sure that the threads are clear of any glue
Center the rear parts to the top plate of the fuselage, and press them tight
Install the front boom holder in place
The rear boom holder consists of two parts
Align both parts on the future boom, to make sure the opening are dead straight
Install the “firewall” onto the top plate
Install the bottom plate in place. Flip it upright from this stage and continue working on a flat surface, to keep the fuselage nice and straight
Glue the nose fillers together. The cut out in the NF2 part is for the ballast, so keep this area clean of the access glue
Install the side walls in place
Now, install the nose fillers
Apply just a few drops of fat glue on the side walls to temporary fix the cover in place. You will need to break this joint after shaping down the fuse
Fix the cover in place and let it cure before proceeding

Part 3. Tails & A Tailboom

Since DLG pilots may launch gliders with either left or right hand, you can build the Lull DLG to suit both categories.

Before starting this part of the build, you need to decide on what hand you will use for launching.

Most DLG pilots launch with a right hand, so if you are like that, follow along as the pictures below show how to build the glider to perform best for the Right-Hand launchers.

For Left-Handers, you will need to alter the positions of the following:

  • Rudder hinge – left on the pictures below to the right side of the fin
  • Rudder control horn – should be on the left side for Left-Handers
  • Elevator control horn – flip the entire stab from left to right to put the control horn slot on the right side
  • Pull cable exits – mirror the positions of the holes on the boom

For more info, please, refer to the hints on the printed plan provided with the kit.

And make sure to build the tails

Also, in this build, we’ll be using Z-Stitch, aka Crossover hinges, made of a covering film.

For more info on this type of hinge, please, check the video below and scan through this tread on RCGroups.

So, make sure to build the tail boom and tails following the desired side of the launch peg.

Removable Fin?

Building the Lull you will have an option to make a removable vertical fin.

Please, note that choosing this option will make your glider heavier.

For this purpose, you must 3D-print a mount and use it as shown in the image sequence below.

The fin mount will increase the weight of the tail which will also lead to adding nose weight for a correct CG.

So, we recommend going with a permanent tail install unless you strongly need your fin to be removable.

The latest kits will be supplied with the updated stab mount which is lighter, stronger, more compact, and easier to assemble

If you choose to use the mount, expand the opening in the fin using the laser cut marks as guides and cut the central “pin” from the slot as well.

The pictures below show how to build the Lull with the removable fin.

So, back to our build:

(Optional) While the control surfaces on the tails are uncut, apply a stipe of a masking tape and taper them for better glider performance
This is the example of how it should look after
Find 500mm long Twill carbon 6mm tube and wrap one of the sides with a masking tape
(Optional) Sand this edge of the tube 45° from each side, creating a 90° tip
(Optional) Dry fit the vertical fin mount making sure that it fixes on the boom and does not spin, when pushed all the way in
Find a pair of stab standoffs (updated to one-peice mount in the latest kits) & M3 nuts, clear the plastic parts from printing escess making sure they can slide on the 6mm tube with a moderate force
Insert M3 nuts into the corresponding slots in the standoffs and screw the stab mounting bolts in, making sure the nuts are positioned correctly. Fix the nuts with a drop of medium CA. Make sure that the treads are clear of any glue and the bolts can come off
Next, wrap the “boom” ~140mm from the edge sanded to 90° before
Drill ~1.5mm holes on both sides of the boom, selarating them by ~10mm
Oval your holes by altering the angles of a drill bit while making these holes
Put both stab standoffs on the boom
Position the front standoff ~100mm from the sanded 90° edge of the boom.
Dry-fit the fin mount on the fin, put it on the 90° sanded edge of the boom, slide all the way in so it locks from spinning and temporary fix the fin on the boom with a wrap of masking tape
Mount your stab on the standoffs. Adjust the position of the rear standoff as needed to fit the mounting holes on the stab
Now, adjust the position of the standoffs on the boom to find a perfect perpendicular position of the stab and a fin
Measure the distance from the front edge of the boom, to the elevator hinge line to make sure the stab is perpendicular to the boom as well
Note the position of the elevator horn cutout. This is valid for the Right-Hand launchers. For Left-Handers, please flip the stab right to left
Double check all the angles and fix the standoffs on the boom with CA
Make a nice fillet around the boom from each side
If you are using aftermarket flathead mounting bolts, feel free to screw them all the way in, so they push through the wood to become flush with the top surface
This is the maximum you should tighten these
Regardless of the type of bolts used, remove the stab and apply a few decent drops of thin CA into and around the mounting holes
Apply activator, and sand the grains that may appear with a fine sandpaper block
Now, you can cut the elevator and rudder off
Round the edges and taper the hinge lines of each surface accordingly. Please, refer to the printed plan for your options. In this build we’ll use the Z-Stitch or Crossover hinches
Wrap the tails with the covering film of your choice and hinge your flying surfaces. Make sure you have an extra hinge around the control horn and in 60mm distance from it
Open slots for for mounting bolts and control horns. A soldering iron with a thin dry soldering tip might help here
If using opaque covering, light up a flashlight from the opposite side of your part to locate the holes with 100% accuracy
Prepare your control horns and scrub the sides with a sandpaper for better adhesion
Insert your control horns in place and fix with a medium CA
Remove the film from the fin mount slot. Make ~1mm of balsa wood free of the covering
Carefully install the fin mount into the slot, and apply the thin CA on the entire perimeter, from both sides
Bend two pcs of 0.5mm music wire into a C-shape, with ~15-20mm legs.
Insert the your torsions into the tails from hinge side into the surface. Make sure that one of the leg is as close to the control horn as possible and the other is also close to the hinge. This will prevent bending the tails under load
Glue the tail fillers in a single stack and push it onto the boom
Insert your boom into the fuselage, all the way in
Mount the wing in place
Install both tails and spin the boom to align the tails with the wing
Use a drop of CA from the rear side of the fuse to fix the boom in place and prevent it from spinning out of desired position
Slide the rear filler to the fuselage and glue it in place
Now, shape and sand the fuselage to the desired shape
Remember to protect the boom behind the fuselag with a masking tape
Once finished, stick a knife under the cover to pop it off
Prepare two pcs of plastic sleave
Install these into the firewall and apply a drop of CA to fix in place
Also, use medium CA to fix the front part of the boom inside the fuselage
Make a healthy fillet inside from both top and bottom part of the fuse

Part 4. Control Linkages & Servos

The Lull is designed to fit a lot of servo options in the pod, up to 9g analog ones.

Check how different servos perform in a combo with 1S LiPo and choose accordingly.

Center your servos, trim the control arms and install them at 90° to the side of the servo
(Optional) Remove the tabs and wrap them in masking tape and/or thread for better adhesion
Grab the cable from the kit and split them in two halves
Push one cable through the boom opening near the tails, and all the way through to the fuse
Fish out the first cable from the bottom side of the fuse and fix it temporarily with a masking tape. Repeat for the second cable making sure they do not cross or interfere with each other inside the boom
Fix both wires with a masking tape on the rear
Cut two pieces of the plastic sleeve
Put it on one of the wires and slide it all the way back to the boom
Lay the sleeve nearby the B4 part of the fuse, and push the sleave 0.5-1mm into the boom. Pull the “tail” of the wire to the top side of the boom to help you keep it in place. Finally apply fix it permanently with a thick CA
Next, push the front tail of the wire into the sleeve in the firewall and repeat the process for the other cable
Find a good position for your servos
Crimp the cable on one of the servos
Using servo tester of your radio, turn the control arm to the full “backward” position, and glue this servo in making sure that the cable crimp tube will not interfere with the firewall
Turn the servo arm to the opposite side, and leave it this way before gluing the front servo
Crimp the cable on the second servo now
Find a place where it won’t interfere with the rear control arm, and glue it permanently. Also apply a drop of CA on the crimp tube to secure the wire inside
Now, use your radio or a servo tester to hold central positions of the servo arms
Install your tailplane in place
Make a loop through the crimping tube on the elevator wire – the one on the left for right-handed builds
Hook the loop onto the elevator control horn
Pull the end of the wire towards the cable opening in the boom to set elevator in the neutral position
Pull the crimp tube closer to the control horn and crimp, leaving ~10-12mm long loop. Apply CA to the both sides of the crimp tube
Install the fin in place.
(Optional) For removable tail, use two stripes of sticky tape along the boom, and then wrap the same tape around the boom and fin sleeve to fix in place
Repeat the same proces as with elevator to finish the rudder pull cable
Pack your radio gear into the pod
Make an O-ring for easy battery access following this tutorial

Part 5. CG Balance & Radio Setup

The last part of the assembly includes the installation of the RC receiver, a battery, and finding a correct CG point.

The last bit is critical as it will directly influence your in-flight model performance.

Feel free to use the following settings as your starting point and adjust later based on your preference.

Recommended Settings For Lull DLG

Lull 1.2m DLG Control Throws CG Settings
CG 84-87mm from wing leading edge (at the root rib)
Rudder Throws +/- 12mm
Elevator Throws 6mm up / 12m down
Launch [Elevator] 1-1.5mm up
Launch [Rudder] 6mm right (for right hand launchers)
Zoom [Elevator] 0.5-1mm down
Zoom [Rudder] Neutral

If your CG is too far behind the recommended position, you can use some car weights in the nose to move it forward.

Our build here required 15g of weight in the nose which perfectly fit into the ballast enclave stuck one over another.

The radio setup for Lull is quite basic since you need only two channels here.

However, for OpenTx / EdgeTx users I highly recommend SoarOTX templates, that offer user-friendly configuration, flight logs, scoring, flight graphing, and many more.

Lull 1.2m DLG it the flying field

As soon as you are ready, head down to the field and please, share your experience with us in the comments below, on RCGroups thread, or just by tagging us on Instagram.

We always appreciate your input!

And as always, happy flying!

Leave a Reply

Your email address will not be published. Required fields are marked *