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Aug 11, 2017, 03:06 PM
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Mini-HowTo

Design solutions for a simple DIY pod & boom glider


Hi,

Some time ago I designed and build a model that after almost three seasons has proved to be ideal for conditions I usually fly in and to be robust enough to survive for so long.
What I want to do here is to describe some of the design solutions I used in the process. I hope it will be of some help to other builders.

I live and fly in the South East of the UK. Most of the time I fly the wind is around 46 m/s (810 knots), but sometimes, on a calm day, it could be as low as 2..3 m/s. Good thermal activity is not unusual on my local slop as well.
I do not like flying fast. I prefer searching for thermals and lifts, but sometimes I practice basic aerobatic.

After some extensive research I decided to base my design on Fusion by leadfeather . I kept the general dimensions of the original design. However, my requirements were different leading to several modifications. These in turn resulted into a heavier and perhaps more robust model better suited for rougher flying and especially landing conditions of my local slop.

Attached diagram shows the general dimensions of the model. The sort of highlights of the model I would like to describe here are:

A wing with a multi-element spar
All elements are mounted on a single nose-to-tail CF tube
Almost all elements of the design can be removed for re-positioning, replacement etc.
All moving tail with flexible push rod
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Aug 11, 2017, 03:19 PM
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Wing


Unfortunately, I do not have facilities and expertise to cut cores from EPP as in the original Fusion design. Thus, I am limited to somewhat simpler solutions in all my designs.
The discussed wing was sanded from a block of Depron. Each half of the wing was divided into three sections. Two or three pre-shaped layers of 3mm Depron were glued to the base 6mm layer for each section using EVO-STIK Solvent free IMPACT glue. Profile templates were glued to the ends of the sections and the sections were sanded to achieve the required profile. The attached pictures illustrate the process.
After that all six sections were glued together using Gorilla glue. The resulting weight of the core was 115 grams.

The central spar was made of four 3 mm x 0.5 mm CF stips. Two 1.5 meter long strips on the upper surface and two 1meter long at the bottom. The strips form a sort of box 5mm x aprox. 10 mm. The groove for the strips were cut using a piece of sharpen strip of the same thickness. Two additional shorter strips added at the bottom to stiffen the wing. The strips were glued in with Gorilla glue. After that the wing was covered with laminating film

Due to the small cross section of the strips the whole installation process is very easy and painless. At the same time the box like structure together with the laminating film covering make a very rigid constriction.

The final wing mass including 15g servos and the outer layer of packing film is 290 grams.
Aug 11, 2017, 04:04 PM
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Boom and Pod


The backbone of the model is a single CF tube with OD 7mm and ID 5mm. It extends from the nose to the tail without any interruption. There is one hole drilled in it to fix the elevator. I will talk about it in a later post.
The nose tip is made of balsa and glued to the boom. In the beginning I had tried to make the tip the part of the pod, but with my poor moulding skills it did not work quite as expected.
The elevator and the rudder (if used) servos are mounted directly to the boom. The battery pack is simply taped in the position.
The pod shell was moulded out of a water bottle and does not have any load bearing role. It is just a cover protecting the battery and the servos.
The wing bed consists of two parts bolted together using six M3 screws. Thus it can be disassembled or moved along the boom.
The rudder is made of three layers of 2mm Depron and glued to the boom. Again, I wanted to make it removable, but all solutions are not quite as light as needed for the model. However, the first variant managed to survive for two seasons. I replaced it recently with the second iteration shown in the photos. No damage to the boom.
Finally the elevator assembly. It is fixed in its position by a M3 screw and can be easily removed if needed.
Aug 11, 2017, 05:43 PM
It's time for me to fly
JimZinVT's Avatar
Nice. I have built similar, but smaller span (32" - 40") DLG gliders with no carbon at all in the wing, just 3 mil lam. film covering and an extra strip of 3 mil as a "spar" of sorts. Surprisingly stiff and with a little care they held up fine, so yours with the carbon ought to be nice and stiff. Nice job with the sanded wing. I did a single template pivot cut for mine.


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