PUG DLG

Posted by Shane Cooke on

The Pug DLG is our entry level 800mm span Micro DLG.
Aimed at Builders who want something to relax with on a Sunny afternoon .
Simple Rudder elevator Control and easy lauching are attributes that make this suitable for small fields and quiet country spots.

With careful use of adhesive and lightweight components and covering film the Pug can be built to between 85 and 95g ready to fly weight.

So Whats in the box?

There is a selection of Laser cut Balsa and a small amount of laser cut 3mm Birch Ply. Some nice Quality Carbon fibre tubes that make up the boom and wing spars along with a solid carbon fibre rod leading edge.

Piano wire pushrods, a 40-50mm length of pre etched ptfe tube that gets cut into 5 8-10mm lengths to support the pushrods along the boom, 2 M3 Nylon Bolts for holding the wing on, and a single M3 Steel bolt to tap the plywood hold down plates. There is even a Bobbin of Kevlar thread to bind the tailplane support onto the carbon boom.

The 3 piece balsa block nose has a hollow centre section that accepts a 5p coin or more if you build heavy to help obtain the CG.


Building:

Anyone who has bulit a traditional Balsa Model before will probably glance at the plan and  a few key points of the fuselage build and just assemble the kit without glancing back at this log.

First job is to tape the 2 sheet plan together using the reference marks.
I also run clear sellotape along the glue line of the trailing edge. There is nothing worse than picking bits of the plan off the balsa, especially if your using transparent covering

.

Release all of the 2.4mm Balsa ribs from the sheets cutting through the tabs with a craft knife. If you prefer you can lightly sand off the slight scorch mark from the laser before assembly. Either pin or tape the Balsa trailing edge section to the plan and locate the ribs in there approximate positions to make sliding them onto the 3mm Carbon tube spar in the correct order nice and easy.

You may notice I haven't slid the main Root rib and the 2 half ribs that go under the wing sheeting on at this stage. This is a personal choice and just the way I decided to build the wing at this stage.

Make sure the spar extends past the wing tip into the tip block, this is essential for strength for discus launching!

Working from the tip rib glue all the Main Ribs to the TE Section. I used a medium CA for this, although PVA or even traditional Balsa cement would be a good alternative.Again working from the tip align and glue all the ribs and sub ribs referencing the plan for accurate position using thin CA.



Please note that what largest rib shown in the above image cannot be glued to the trailing edge as it is cut to a point to take the centre wing sheeting. Slide a scrap of 1.5mm Balsa under this rib to get the alignment correct before bonding to the spar. At this point I realised just how quickly this wing goes together. 

Again working from the tip glue the 1.5mm carbon rod leading edge into the notches in the ribs. You may find that when you glue the leading edge to "R2" it pulls the rib away from the trailing edge as the next image, this is not an issue.

Cut your lower centre wing sheeting from the spare 1.5mm Sheet
You will need to join the sheet so it runs from the trailing edge and past the carbon fibre leading edge,

Glue the centre sheet to the railing edge first! Now you can glue the Sheet to "R2" pulling the spar between finger and thumb to close up the gap.

The 3mm Birch Ply main wing spar is released from the sheet cutting through the tabs with a heavy duty DIY style knife

Slide the remaining 2 sub ribs and Front centre rib onto the spar. One of the sub ribs is a doubler against the main centre rib, the other goes central between the Main centre rib and R2. The dihederal brace should be be glue to all the Ribs, sub ribs and lower sheet, and finally the Rear Centre rib can be glue into place. Note that the centre rib needs to be angled to match the dihederal brace. This is easy to achieve close enough by eye.


Wing tips are laminated from 3 pieces of 3.2mm Balsa. The middle core has a cut out to accept the spar where it extends trough the tip rib. The spar can be glued into this cut out using tick CA or epoxy, or if your using thin CA fill the void with baking soda or similar. This joint really wants to be as strong as possible.


You can now add the Top centre wing sheet and trim the bottom sheet before removing the wing panel from the plan and sanding the tip and centre sheet.
 
The opposite wing panel is built in exactly the same way. up until the point of adding the dihederal brace and centre top sheeting.It is at this point we join the already completed panel.


You will end up with a slight tapered gap between the centre sheets.
Using scraps of the 1.5mm balsa cut tapered filler pieces to fill the void.
Its really easy to do and you can use pva to glue these in rather than sticking yourself to the model.

You can now remove the wing from the plan, Sand you wing tip to shape and final sand the wing ready for covering.

On with the fuselage!


Release all of the 3mm Birch Plywood formers and the 1.5mm Balsa fuselage parts using a craft knife and DIY Knife. Please note that some of the fuselage parts are very small.

On early kits the main Fuselage former is wrong! There is a correct updated former provided in the small parts bag

Drop the formers into one half of the fuselage and tack glue into position before adding the opposite fuselage side. Again only tack the formers into place. This allows some movement and flex.

Once you have added the lower fuselage sheet you can then run CA into the joints of all the fuselage formers and add the rear Wing hold down plate right at the back of the fuselage. Fit the 1.5mm Balsa front former, front top Sheeting and rear sheeting. tack glue the Hatch into place for sanding. Do not use excess adhesive.

Its a good idea to prepare all the tail surfaces now.
The fin / Rudder has a sub fin that should be glued on first
Do not remove the rudder at this stage. Sand the trailing edges of the rudder and sub fin to around 1mm thick! if your not comfortable with covering delicate parts you can ommit this for a small weight penalty and maybe a little extra nose weight.

Remove the rudder and cut a bevel on one side. The rudder and elevator on the PUG are hinged using the covering film or lightweight clear tape. The tailplane and elevator should be sanded and bevelled the same.


Glue the fin centred  to carbon Fibre boom. I packed the fin from the work bench surface using 0.8mm balsa, although thin card or multiple layers of paper can be used. Glue and bind the plywood tailplane mount to the boom. This should be glued so the rearmost edge of the Mount is 43mm from the end of the boom. You can check this distance before saturating the kevlar binding thread provided with CA by offering the tailplane and elevator assembly onto the mount.


Slide the boom into place but do not glue yet! The boom should protrude through the former by 3 to 5mm.


It was now I decided to fit the wing as it would allow me to check the alignment of wing to fuselage and also the vertical alignment of the fin tail assembly. The above picture shows the boom held in place with just one dot of CA and the same with the tail.

I found it easiest to use a thin Screwdriver to drive a pilot hole through the TE section first and mark the rear hold down plate. Drill a hole where marked through the hold down plate using a 2.5mm or 2.6mm drill.Using the Steel M3 bolt supplied tap out the hole in the plywood until the M3 Nylon bolt screws in and out nicely. I cut the head off the steel bolts and use a battery drill to drive the bolt in and out of the plywood plate numerous times to ease the thread. Repeat the same for the Leading edge of the wing ensuring the wing is square to the fuselage and boom. you can check alignment by measuring  the distance between the wing tips and rear of the fin, making sure both distances are the same.

Radio Installation 

You can see how I mounted the Rudder and elevator servos to the floor of the fuselage. Keeping the servos as far forwards as possible. The Piano wire pushrods are attached to the servo horn first using a z bend on the end of the pushrod. The servos are glued to the floor using contact adhesive or thin double sided tape.


I used a Lemon DSM2 RX and a 1s 500mah Lipo mounted underneath the hatch.
Youll notice that I still havent added the nose block.

My advise is to cover the model apart from the fuselage at this stage.
We recommend Oracover light which is only around 36gsm, Most budget coverings are in excess of 100gsm, Not only is the weight penalty huge it can also badly distort the parts
We can easily add weight to the nose block to obtain the CG once the tailplane and fin are covered and mounted!

The pushrods are supported on the outside of the boom with PTFE guide tubes.
A 40-50mm length is provided with the kit, I cut this into 8-10mm lengths. I used 2 lengths for the elevator pushrod positioned at 120mm and 210mm from the end of the boom. The remaining 3 lengths were used on the rudder pushrod at 30mm, 120mm and 210mm


For the control horns we suggest using a cut down servo arm glued into a slot in the rudder / elevator. Again a single Z bend is use to terminate the pushrods

With the tail now mounted, and the boom squared and gluedIts a good time to see if you CG is close. This will differ based on how much you sanded the Tail surfaces and the covering. 

The nose block is cut so the centre core will accept 5p coins. Hold the nose blocks onto the fuselage with masking tape and check your balance the Pug should balance on or just in front of the main spar at the root. Add 5p coins until your CG is close. Once your happy you can glue the nose blocks into place with or without any coins glued in and sand the nose block and finally cover the fuselage.

You have one job left before your going flying, and that is just the launch peg. You can glue the peg in for either left or right handed launches.

Time for fun :)

My model weighs in at 91g with 5g of bluetak in the nose (hence the hollowed nose block now supplied with the kits) 
CG is set to 60mm from the leading edge.

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