Hong Kong RC Sailplane Forum 香港滑翔機發燒友論壇

Years ago I was thinking to acquire an EPP model with conventional tail so that I can practice serious aerobatic skills without risking losing an expensive molded model. There were a few on the market at that time, such as Redback, Eraser, etc. However, I am not impressed with their performance in terms of speed or maneuverability, so the idea was put off. Recently, Windrider has introduced a new EPP model based on the well-known scaled Fox glider. The new model has a wingspan of 66" and was made by Windrider's EPP molding technology. After watching some crazy DS movies of this EPP Fox, I was convinced and immediately called the boss of Windrider, Lou Tze Ming, for acquiring one. When I opened the box, I was amazed how thin the wing profile is for this EPP model. The design and molding are of high quality. Sure it would be a good aerobatic model. Here is some information to build the model.

The box design and the packaging are good



Sanding off the steam hole dumies


The wing is too thin near the wing tip areas. Need to install a fiber sheet to re-enforce the wing tip


Re-enforce with sheets both on top and bottom of the wing. Look stronger now!


The original design has only one spar of 5mm carbon rod. I installed another spar in front of the cable cabinet in the wing root



The model is too light to fly unmodified, so I installed a ballast tube on the belly with the exit hole on the wheel chamber. The wheel can be taken off when I need to install ballast.





I think I need to re-enforce this area with fiber sheet because this is the weaker part of the fuse and it carries most of the weight.


To be continued ...

even install a ballast tube in it & azaming enforcement. if coming with good performance, in the coming 60inch race may try to use it too Stanley

Finished the ballast tube and wheel cradle

Ballast can be easily installed after removing the wheel which is fixed by 4 screws to the cradle

I want a model with good 3-axis manuvourability, so I set up the rudder. The original rudder size according to the molded cut line is too small for yaw motion, so I have to cut a larger rudder.

Reinforce the rudder and rudder cradle with balsa sheet

Again, need to reinforce the elevator with balsa sheet

Look good! The movement is free of any obstruction

The foam aileron is too soft for serious aerobatic, highspeed dive and DS, so I installed balsa ailerons on the wing.

Look more solid and should be good for speedy flight

Tape the leading edge with strong tape to protect the wing from any unwanted impact


To be continued..

Stanley, 攪到三更半夜，你似乎對佢好大期望喎！

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Good job Stanley, first building log in HK forum, salute to you !

Is it possible to detach the wings for delivery and re-asssemble the wings to the body in the flying site?

The wing is in two pieces. Once you install the wing rod and slice the wing into the fuse saddle, it is already very tight. There is no need to glue the two wing parts together.
Anyway, I also installed two strong magnets on the wing roots so when the wings come together in the fuse, they are held even tighter together. So these two wing parts can be separated for transport.

Thanks for answering my question. I have two more questions: Is the EEP wings "rigid" enough under serious aerobatic? Is EEP more durable compared with Balsa planes?

Well, I think the wing is very thin but it is made of EPP (mode durable), so provided that you reinforce the wing tip with fiber sheets and build a strong wing rod system that will be ok for serious aerobatic and some abuses. I installed a second wing rod because I also built a ballast system. Anyway, I have yet to test whether the two rod system (5mm rod) is strong enough when the ship is fully ballasted.
I will try to keep the overal weight to be light and only in heavy wind condition ballast is needed.

Well, continue on the build

Just installed the rudder servo

Glue the elevator into the fuse and install the control linkage

Completed the radio installation and also installed the magnets for holding the canopy

Installed the wing servos.
The original servo bays are for futaba 3016 micro servos. I want to install stronger aileron servos with metal gears, so I cut a larger bay and installed the HS125 wing servo which I hate to use in big F3F planes. Anyway, Hitec gears are easy to break so I also installed a servo cover to protect it from breaking during landing.
The all up wieght is 520g without balancing the CG. I needed to add an extra 20g to balance the CG at 2" from the leading edge as recommended by the manufacturer.
The ballast tube in the belly can carry 300g of lead.
It's now ready and I will test fly this beautiful model this weekend.


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Maidened my Fox today in Fei Ngo Shan. CG is exactly at 2" from leading edge as recommended. It flew well with good behavior and apparently fast. However, the wing is still too floppy even with no ballast installed. In a dive and pull up, the wing bent easily, this caused the plane to shoot up further possibly due to a positive attack angle. With full ballast installed (300g), the wing cannot sustained in narrow turn which caused the plane to stall or steer to other direction, making it very difficult to control. The wing definitely needs more enforcement.
The aileron authority is too small for quick roll as the aileron length is only half that of the wing length. I would have preferred to install a full span aileron extended to the wing root.






Some movies taken today
http://www.rcsail.com/tmp/fox_epp_movie1.mpg
http://www.rcsail.com/tmp/fox_epp_movie2.mpg
http://www.rcsail.com/tmp/fox_epp_movie3.mpg

Stanley,

你改到隻 EPP Fox 面目全非，子明真係多得你唔少，人地以為佢架 Fox 唔大改唔掂

不如你改個標題做“EPP Fox 上山劈友無堅不摧之終極大改造”，以正視聽

嘩！每個人的喜好都唔同。子明隻Fox係好機，無需大改都可以飛，改多D使它較穩固是想它的性能提升。我個人覺得隻機無大改的話比較適合初學者用來提升個人飛行技術，加強後隻機就比較適合有經驗的機師用來練習花式飛行。