Steve Shumate F-15 Eagle Park Jet depron scratchbuild

[cdfigueredo]

Hey, guys. I've been searching the web for some new models to build, and I came across these amazing models by Steve Shumate.
Some more complicated to build than others, so I decided to start with this F-15 Eagle Park Jet.


As some will know, getting foamboard where I live is impossible, so I will build the original version in deprom. On the plan he uses 6mm deprom, but here I can only get 5mm, so I'll build with that.
If everything works well, it will be easy to replicate using foamboard. I have also modified the construction to use swapable power pod.

 

[cdfigueredo]

The first challenge was to modify the fuselage to accept the power pod. The solution I found was to separate the original engine mounts to allow inserting the power pod between them.

Those are images form the assembly guide.


And this is the solution i found


The power pod does not need to be holded in place with barbecue sticks because, as a pusher plane, the power pod wont came out.

 

[cdfigueredo]

The main problem with the modification is replacing the elevator's operating mode. The rod that connects both elevators interferes with the power pod, so it is necessary to find another way to do it.

This is the way the original elevators works


And this is what i have now


I was thinking of cutting the shaft in two, one on each side of the power pod and using two servos to control the elevators. What do u think??? Any other idea? I'm really short on servos, and I wish I could do it with just one.

 

[cdfigueredo]

This is what I have so far. Not bad for only feew hours

 

[cdfigueredo]

At the end of the day I found the solution. It may not be the best, but I think it will work well.
I used barbecue sticks as an axle for the elevators. A servo arm glued with cyanoacrylate to allow mobility. Then I added hot glue to the joint to make it even stronger. I don't think it will help the joint much, but it makes me feel more comfortable. I am using a single servo to controll this.


As you can see, the power pod wont be blocked by the elevators axle.

 

[cdfigueredo]

Some other details added

 

[mach1 rc]

Sweet clean looking build

 

[cdfigueredo]

Sweet clean looking build

thanks!!!!!

 

[danskis]

Great idea for the elevators. Very nice build and it looks like it flies well too.

 

[cdfigueredo]

This is what I have now. . Looking good ah??

 

[OliverW]

This is what I have now. . Looking good ah??
View attachment 151800 View attachment 151801 View attachment 151802

Looking awesome!

 

[CrazyFastFlying]

Looks great!

 

[CrazyFastFlying]

What's the flight time and what battery does it take?

 

[cdfigueredo]

What's the flight time and what battery does it take?

I don't really know. Guess I should figure it out. . On the original building log thread they used a 3s 2100mAh, but the plans say 1300mAh. So I don't really know.

 

[cdfigueredo]

Hey, guys, it's been a long time since the last update. This project has been going very slowly.

The current state:

• The wings are attached in their final position.
• The ailerons are connected and functional.
• The hatch to access the receiver and servos is ready, just need to install some magnets to fix it.

What's missing:

• The cockpit.
• Add some velcro to hold the battery in place.
• And most importantly, re-design the elevators. The original system didn't work for me. Maybe because the servo was too far away from the control surface and this caused the elevators to shake. The barbecue rods are also not rigid enough to prevent twisting. That's why I've decided to modify the elevators. But I'm waiting for a new servo because I don't have any more and I need an extra one.

So far this is what i have.


By the way, this guy has taken the original plan to the next level. Unfortunately I found this thread after I started my construction, and there are steps that I can't undo now. But it would be a good idea to try another model later.

 

[cdfigueredo]

This is what i mean.

Using the red dot line to make a control surface. Not pretty scaled but will work i guess.

 

[cdfigueredo]

The maiden flight didn't go as expected. It didn't really fly. The photo sequence I think is better than the video.

I think I have identified the causes of the failure.

1. The elevators were too loose. They could move easily with the hand while the servo was still. I think that in spite of trying to apply the lift, the air simply had more force.
   This has already been repaired. I moved the servos out of the fuselage and installed control horns and push roads to the elevators.
2. I used a slow flying propeller with a lot of diameter and little pitch. Maybe this plane needs a higher pitch propeller to gain some speed.
3. Perhaps the flat profile does not have enough sustainability for this plane. I may need to modify the wing profile.

Can anyone give me any ideas?

 

[danskis]

Did Steve use a flat wing? Try a little up elevator on launch? Move the battery back a little? Use the 1300 instead of the 2200 battery to make the whole plane lighter. The plane looks light enough to use the prop you're using....I don't think I'd change it.

 

[quorneng]

Was it at full power?
To me it looks like it did not accelerate after the hand launch and simply did not have sufficient flying speed to create the required lift.
It could be a simple prop pitch issue but I agree with danskis the best solution to get it to fly initially is to reduce the weight with a smaller battery.
Once you know it does fly you can address any problems that might arise from using a heavier battery.
If it were me I would have no hesitation is using individual (and smaller) elevator servos. You get no slop then!

 

[cdfigueredo]

danskis & quorneng, i think u are both right.
It is importatnt to say that it was not full power when i launched it, so i think it did not have sufficient flying speed. But i stil thinking about using maybe an 8x8 prop instead 10x3.8. Now i am also using individual servos for the elevators, so no sloping probem now.
About using an small battery, i must way it is not an option, because the 2200mAh i am using now it is necesary to get the CG in place.

This is how the elevators are working now.