XF VIPER - Foamboard F-16 EDF

[Pieliker96]

I finished and maidened the 100mm XF Viper! Using two 3300mAh 6S packs in series for insane 12S power, it flew for about 4min. It's probably hard to grasp from the pics, but that thing is HUGE! About 175cm long.
Conclusions:

• Hand launching it is difficult (but doable once you find the right technique)... Unfortunately I scrunched the nose on the first attempt, but that didn't stop me from trying again.
• It feels like the EDF is not getting enough air, making it less powerful than it could be... unfortunate, but that's just due to the F-16's design.
• It's not extremely fast, but not exactly slow either.
• The maximum roll rate, as predicted by Ben, is insane!
• Belly-landing is no problem, even at >4kg AUW.
• The batteries get VERY hot, due to having no airflow over them - this would really hurt them in the long term.
• The carbon fiber reinforcements I made were definitely necessary!

In conclusion, this was definitely a fun project, but I feel like the very high-end electronics and powertrain I have on this plane would be better suited for a more sturdy plane - even after just one good flight, you can already see the maker foam looking very worn in many places. Ultimately, I think the material just doesn't scale up that well for heavy/large planes. Thus, I'll probably take out the electronics and build something else. Still, many thanks to Ben for the excellent plans! I will most likely build another, but at its original size.

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One thing you may want to check with regards to performance is your nozzle exit diameter and area. Compare that to the Fan-Swept Area (FSA) - the area of the fan's frontal area minus the area of the motor and hub. From this post it doesn't visually look like there's any taper to the thrust tube, which is required to get the exit area equal to or smaller than the FSA (≤100%). A straight pipe with no taper will be at over 100% FSA which will lose both static (stationary) and dynamic (in-flight) thrust. 100% FSA optimizes for static thrust, and more constricted means higher top speed with the tradeoff of lower thrust at lower speeds - 90% is a good starting point. Constricting the nozzle exit area if it is indeed over 100% has the potential to drastically improve performance.

 

[Taildragger]

My first was Ben's A-4 and I think the F-16 flies a little better, easier. The Viggen would probably be the best trainer foam board EDF, but if you're already a decent-ish pilot you will be fine with ben's F-16.

EDIT - 11/5/2020: Version 8 plans are UPDATED and in the "Resources" section: https://forum.flitetest.com/index.php?resources/xf-viper-foamboard-f-16-edf.47/

(also in the attachments at the bottom of this post)

- Latest version is "V8" - Paper thrust tube page is still "b5".
- Current plans are full-sheet, 5 sheets of foamboard, 1 paper thrust tube


It's been a LONG time comin', but it's out!

SP0NZ has been pokin' at me for quite some time, "when are you gonna do an F-16!?" .... so after the Valkyrie project wrapped up I figured it was time. Surprisingly the design came together fairly quickly.

Starting from a 3-view, I blocked it out....

View attachment 110816

One main design constraint I gave myself was that I wanted to simplify the controls. After designing the F-5 and F-20, both of which were 4-servo jets, I knew that was too much. It's doable, but it's also annoying to set up.
So for the F-16 I challenged myself to try using elevons on the horizontal tails ONLY. I could always add ailerons to the wings later if necessary, but if the elevons proved to give enough control then great! (spoiler alert: they worked!)

Here is a progress shot from the first weekend working out the design:
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Here are a few shots of putting the first one together:
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And here's the first prototype assembled:
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You can see the elevon servo wires snaking on the outside. I completed the build before knowing exactly where I wanted to put the servos.

About a week later the first prototype took to the sky:

If you can believe it, I didn't need a single click of trim; it flew awesome!

After a few test flights I determined it was a bit nose heavy, and I couldn't shove the battery any further back, so I went to the drawing and moved the EDF about two inches aft. That gave me enough headroom in the airframe weight to put the battery in a comfortable place and get the CG that I wanted.

THEN Flite Fest Ohio 2018 was looming ahead, so I decided that would be the perfect place to unveil it to everyone:

Something about this design just, "clicked". The A-4 Skyhawk is my favorite little jet - it's the first jet I can remember seeing when I was a kid, and my dad showed me the Blue Angels "Dreams" music video from the 80's - but this F-16 is stealing the show right now. It's more aerodynamic, has a better CG balance, simpler servo setup, and just performs better all around. Yes, it's a bit more involved to put together and it takes one more sheet of foam (5 vs. 4), but it's SO rewarding! And it's SO fun to fly!

Which brings us to now: "WHERE ARE THE PLANS??!!??"

SP0NZ will be reworking the plans, making them readable for everyone, and I'll have a few select builders checking them too, before releasing them in the wild. I have a bad habit of sending out plans and IMMEDIATELY finding something I need to change. I may release a set of beta-plans, after I get some more eyeballs on them, but please be patient in the meantime regardless. No one wants you all to start playing with this jet sooner more than ME!

Finally, here are the specs:

Wingspan: 30"
Length: 48"
Power: 70mm EDF (12-blade 4S recommended)
Suggested EDF units:
- https://www.motionrc.com/collection...mm-12-blade-edf-4s-power-system-w-2849-2850kv
- https://www.banggood.com/FMS-70mm-1...5-KV2750-Motor-For-RC-Airplane-p-1023640.html
- https://www.banggood.com/QX-Motor-Q...27-2849-2600KV-Brushless-Motor-p-1094622.html

Battery: 2500-5000mAh 4S
ESC: 80A (recommended)
Control: Two servos, Elevon tails

Build video time-lapse:

And that's that! Hope you like it!

Hey ben, I was wondering if it would be possible to make a BDF fit in one of these
honestlyI'm looking for a cheaper way to make this beautiful plane, maybe scale it down and use a prop in slot?

 

[XDmToter]

This is the first design I've seen that actually made me want to go buy an EDF! Great Job Ben!

I picked up the cheapest EDF I could find. I got one of those $5 Changesun 10 Blade units from HobbyKing, and the $15 Turnigy L2855 to match. Hopefully it doesn't explode.

I've been flying many various Prop-in-Slot, Tractors, and Pushers for years, but this will be my first EDF jet.

I'm probably going to build my first one with $Tree foamboard per the plan like a "normal" FliteTest style plane. After I crash that beyond recognition, I will likely make some modifications and rebuild it using techniques that I am more accustom to using ModelPlaneFoam.

Honestly though, I've never had much luck with FliteTest planes due to delamination of the paper after a few flights... I might just skip this step and go straight to modifying it and build the first one with the cheap Fan Fold Foam from Homedepot. It's ugly, but cheaper than $Tree foamboard, and it's practically the same as ModelPlaneFoam, so the build techniques are identical.

Wish me luck!

 

[speedy7385]

Hey ben, I was wondering if it would be possible to make a BDF fit in one of these
honestlyI'm looking for a cheaper way to make this beautiful plane, maybe scale it down and use a prop in slot?

Yes, you can use a BDF. I made one, using 2207 1750kv 4052 prop on 6s. BDF need a lot of air flow, you will need to add some treater holes
in front of the BDF. ( Thanks Ben for the advise on the treater holes ).

 

[Matthew Sanders]

This is the first design I've seen that actually made me want to go buy an EDF! Great Job Ben!

I picked up the cheapest EDF I could find. I got one of those $5 Changesun 10 Blade units from HobbyKing, and the $15 Turnigy L2855 to match. Hopefully it doesn't explode.

I've been flying many various Prop-in-Slot, Tractors, and Pushers for years, but this will be my first EDF jet.

I'm probably going to build my first one with $Tree foamboard per the plan like a "normal" FliteTest style plane. After I crash that beyond recognition, I will likely make some modifications and rebuild it using techniques that I am more accustom to using ModelPlaneFoam.

Honestly though, I've never had much luck with FliteTest planes due to delamination of the paper after a few flights... I might just skip this step and go straight to modifying it and build the first one with the cheap Fan Fold Foam from Homedepot. It's ugly, but cheaper than $Tree foamboard, and it's practically the same as ModelPlaneFoam, so the build techniques are identical.

Wish me luck!

Good luck! It’s a great flying jet for sure! Personally I love EDFs! I’ve got a question. I haven’t been able to find a Home Depot with fan fold foam, so I’ve never used it. Is it more crash resistant than DTFB?

 

[XDmToter]

Good luck! It’s a great flying jet for sure! Personally I love EDFs! I’ve got a question. I haven’t been able to find a Home Depot with fan fold foam, so I’ve never used it. Is it more crash resistant than DTFB?

The 1/4" Owens Corning fan fold foam has two main disadvantages:

1. It has a plastic film on it that can be difficult to remove. Sometimes you can peel off the plastic in decent size sheets, but other times it just wants to tear so you only get a little bit at a time. The easiest way I have found to peel the plastic film is to cover it with packing tape. Then when you remove the packing tape, the plastic film will come up with it, leaving you with a clean sheet of foam. This uses a huge quantity of packing tape that you are just going to throw away, so the $$ you save on this foam quickly goes out the window when you have to buy 4 rolls of packing tape just to get the film off.

2. It's pink. Be prepared for the guys at the flying field to make fun of your pretty pink plane.

As far as the actual structure and density of the foam, it's very similar to DTFB with the paper removed, but it is thicker.

To your "crash resistant" question; DTFB with the paper on is a bit stronger, so you might survive a crash a little better with DTFB. However, I find the lighter weight of the Fan-fold foam makes for a better flying plane than the equivalent plane made with papered DTFB. Therefore I'm less likely to crash in the first place. I built a FT Sparrow from DTFB, and then built another from Fan-Fold, and the Fan-Fold version was notably easier to fly.

Honestly, I probably won't buy any more Fan-fold foam for the reasons I mentioned. But you get 200 Square Feet of the stuff, so I've been building prototypes with the same pack for years.

 

[Matthew Sanders]

The 1/4" Owens Corning fan fold foam has two main disadvantages:

1. It has a plastic film on it that can be difficult to remove. Sometimes you can peel off the plastic in decent size sheets, but other times it just wants to tear so you only get a little bit at a time. The easiest way I have found to peel the plastic film is to cover it with packing tape. Then when you remove the packing tape, the plastic film will come up with it, leaving you with a clean sheet of foam. This uses a huge quantity of packing tape that you are just going to throw away, so the $$ you save on this foam quickly goes out the window when you have to buy 4 rolls of packing tape just to get the film off.

2. It's pink. Be prepared for the guys at the flying field to make fun of your pretty pink plane.

As far as the actual structure and density of the foam, it's very similar to DTFB with the paper removed, but it is thicker.

To your "crash resistant" question; DTFB with the paper on is a bit stronger, so you might survive a crash a little better with DTFB. However, I find the lighter weight of the Fan-fold foam makes for a better flying plane than the equivalent plane made with papered DTFB. Therefore I'm less likely to crash in the first place. I built a FT Sparrow from DTFB, and then built another from Fan-Fold, and the Fan-Fold version was notably easier to fly.

Honestly, I probably won't buy any more Fan-fold foam for the reasons I mentioned. But you get 200 Square Feet of the stuff, so I've been building prototypes with the same pack for years.

I’ve seen online that there’s a blue version of Fan Fold. As for pink, it can be painted over (as shown on YT by PeterSripol) So the color isn’t an issue. Thanks for the info!

 

[XDmToter]

I’ve seen online that there’s a blue version of Fan Fold. As for pink, it can be painted over (as shown on YT by PeterSripol) So the color isn’t an issue. Thanks for the info!

Unfortunately, I cannot find the blue fan fold locally. Lowes has some green stuff but it has lots of perforations and it seems brittle. Not good for planes.

 

[Matthew Sanders]

Unfortunately, I cannot find the blue fan fold locally. Lowes has some green stuff but it has lots of perforations and it seems brittle. Not good for planes.

Ah, ok. Thanks for the heads up!

 

[CrshNBrn]

Just had to add my effort to this long-running thread. The foamboard I used was pretty bad with lots of delamination, so I probably added ton of unncecessary weight hotgluing bits of the paper back down. Dunno how long it will last; maybe have to rebuild it with some fancy Flite Test waterproof foamboard after this one falls apart. Much obliged to Ben for the plans and for all the other posters on this thread for ideas.

 

[Matthew Sanders]

Just had to add my effort to this long-running thread. The foamboard I used was pretty bad with lots of delamination, so I probably added ton of unncecessary weight hotgluing bits of the paper back down. Dunno how long it will last; maybe have to rebuild it with some fancy Flite Test waterproof foamboard after this one falls apart. Much obliged to Ben for the plans and for all the other posters on this thread for ideas.

View attachment 225797

Looks very nice and Sharp! You’ll be flying on 3000 I take it?

 

[CrshNBrn]

Looks very nice and Sharp! You’ll be flying on 3000 I take it?

Yup. Ben's post #20 in this thread indicated CG was 7.3-8.0" from the center root-leading-edge of the wing. I'm not 100% sure where that is on the wing, but it seems to fly okay with the 3000 towards the back of the cockpit hatch area. The first few flights yesterday I had the battery way too far aft... which made for exciting times. Moving it forward helped.

 

[luvmy40]

I downloaded the plans for this yesterday and started getting them ready to Gcode for the needle cutter. I have the FT Limited MS F-16 kit on the shelf, waiting for the time to build it, and the room to store it! Is this a similar size as the FT MS build?

I love the look of this design, I'm definitely going to build one.

 

[CrshNBrn]

I don't know about the specific Master Series size, but I'll bet Ben's Viper is close in size.

 

[Mid7night]

I don't remember all the dimensions off-hand of either, but I do know they are both designed around a 70mm EDF and are of similar size.

 

[Velodrom]

Does anyone here have a good .stl file for a 70mm BDF design?

Based on what I'm reading here, some have created their own designs, and I even managed to find 100mm BDF .stl files from the forum, but I don't have the CAD skills to scale down the outer shell while maintaining inner dimensions for the motor mount.

 

[Player4]

Does anybody know the estimated dry weight and all-up weight of this plane?

 

[DMiller]

My inspiration...
View attachment 117549

Nice, from a Cheesehead transplant !!

 

[NickOfTime]

I recently finished the paint and stickers, and did the second and third flights tonight. This thing flies surprisingly well for how it looks.
In my edition, I 3D printed a simple thrust tube in order to more finely have control over the exit size. My first flight used the stock foam cone which was much too big as I found out after take off. It was a full throttle flight. With a bit more constriction, I certainly lost the low end punch but could fly much faster resulting in more control.
My build still has this weird alpha lock on landing but holds energy very well. This easily has become my favorite plane.

 

[Mid7night]

I recently finished the paint and stickers, and did the second and third flights tonight. This thing flies surprisingly well for how it looks.
In my edition, I 3D printed a simple thrust tube in order to more finely have control over the exit size. My first flight used the stock foam cone which was much too big as I found out after take off. It was a full throttle flight. With a bit more constriction, I certainly lost the low end punch but could fly much faster resulting in more control.
My build still has this weird alpha lock on landing but holds energy very well. This easily has become my favorite plane. View attachment 231259 View attachment 231260

That looks amazing! Great job on the build and livery! Any video of it flying??