FTFC23: Build-ruary by Inq: Inq'd Fokker D.VIII

[Inq]

I've wanted a build challenge and as part of FTFC23, I offer one that I've been wanting to do for some time. This is a custom design using scale dimensions as close as possible, but will follow the design concepts of the Flite Test Mighty Mini DR1 Triplane. In fact, I plan to build them together in lock-step as a kind of guide. Although the build challenge starts in February, I'm guessing it's OK to do design work ahead of time since building kits from FT that are designed AND pre-cut are acceptable in the challenge.

At the moment it is expected to be:

1. Single DTFB sheet design
2. Wing span 760 mm (~30")
3. Power - probably get off cheap with A2212, 2200KV, 6x3.5 propeller, 1500 mAh

I also want take a shot at making a skin for it. I'm still working on color scheme, but here is where I am at the moment.

Back to Inq's top level Build-ruary...

 

[Inq]

I got a late start to the Buildruary this morning and started on this one before thinking I should show my initial status as of February 1st, 2023. Here, I've cut out the fuselage and empennage pieces.

 

[Inq]

Scale, 3D Printed wheels for the Fokker D.VIII. In actuality, all WWI wheels are pretty much the same even across combatants. They can easily be scaled to other models. I'll be using the same wheels scaled down slightly for the FT MM DR1 Triplane. The resource is available (Once Approved) at https://forum.flitetest.com/index.php?resources/ww-i-wheel.369/

Suggested Cura settings will also be provided in that resource. The wheel diameter for the D.VIII is 66 mm (~ 2, 5/8 inches).

 

[Yankee2003]

Scale, 3D Printed wheels for the Fokker D.VIII. In actuality, all WWI wheels are pretty much the same even across combatants. They can easily be scaled to other models. I'll be using the same wheels scaled down slightly for the FT MM DR1 Triplane. The resource is available (Once Approved) at https://forum.flitetest.com/index.php?resources/ww-i-wheel.369/

Suggested Cura settings will also be provided in that resource. The wheel diameter for the D.VIII is 66 mm (~ 2, 5/8 inches).

View attachment 234431

View attachment 234430

Love this plane…”The Razor”. I built one for the Dawn Patrol last year for Flitefest 2022.
It was the first scratch built plane I ever attempted. Looked pretty good….mine was a bit heavy and flew like a brick.
I also built the Simple Scout XL and a Bloody Baron. None of them survived the weekend. It was glorious!

 

[Inq]

I also built the Simple Scout XL and a Bloody Baron. None of them survived the weekend. It was glorious!

I really like the mentality that Flite Test has instilled in people... I can almost hear the grin on your face!

 

[Inq]

I built one for the Dawn Patrol last year for Flitefest 2022.

Almost forgot the first part of your post Did you have a build thread for your Razor or any summary details? You've now got me wondering about weight versus wing area... etc and what I need. I'm hoping (or was until your post) to be about as benign as a FT MM DR1

 

[Tench745]

Almost forgot the first part of your post Did you have a build thread for your Razor or any summary details? You've now got me wondering about weight versus wing area... etc and what I need. I'm hoping (or was until your post) to be about as benign as a FT MM DR1

https://forum.flitetest.com/index.php?threads/flite-fest-2022-dawn-patrol-build-fokker-d-viii.69241/

 

[Yankee2003]

Almost forgot the first part of your post Did you have a build thread for your Razor or any summary details? You've now got me wondering about weight versus wing area... etc and what I need. I'm hoping (or was until your post) to be about as benign as a FT MM DR1

It was mostly first timer mistakes. Inexperience with scratch building and use of materials. The fact that those planes tend to build tail heavy anyways was against me as well. Lastly I spent a lot of time and weight on paint, filler, etc hiding all the dead bodies.
But a super positive experience overall. What you learn by going through the process yourself is the real payoff.
If I would have any advice for a first time scratch builder or maybe someone feeling overwhelmed or discouraged, is to just finish it. Complete all the steps until the end. There are plenty of things to learn and still victories to be had until the very end.
On top of all that be honest and open. The amount of help and advice I got along the way really helped as well. The level of craftsmanship on this forum and the discord channel are almost unbelievable if you didn’t see it for yourself. The willingness of people to contribute and share their ideas …… incredible.

 

[Inq]

Today's progress on the D.VIII

Today's progress was a little slower than I was expecting. Ran in to some hurdles and some re-work.
3D Printed Wheels
The first printing yesterday was not satisfactory. I have updated the resource with a version 2 and explanation for the changes. The second printing went well. The assembly and initial sanding look pretty good (for a 3D print). I will be making another set (slightly scaled down) to match the scaling of the FT MM DR-1 Triplane.

Tool - InqCutter
I am not near gifted enough to cut a strait bevel on the foam board hinge lines. As an illustration of my competence I offer the 3" hinge line of the Rudder.

This simply will not do... and didn't when I tried to do the leading edge fold on the wing (same as a Storch). I decided that there is a better way and created a 3D printed razor blade holder that holds the blade to cut a 45 degree bevel and blade angled at 30 degrees relative to the cut direction. It also incorporates an offset square so that it cuts the 45 bevel in the perfect place above the paper fold. The InqCutter is in the Resources and will be available after approval.

3D Printed Linkage Hardware
I wanted to try using the single servo version for aileron control. I have created the right angle levers and control horns. These are also in the Resources and will be available on approval. The right-angle joints are low profile so they don't stick out. In the Resources, I've included three different versions of the arm so that up/down aileron differential can be incorporated with 0, 10 and 20 degree options.

The Wing
Besides the lousy cutting, I also was wanting to use the rounded top surface used in Master Class planes, but I just couldn't achieve it this small of a wing, so I fell back to the double-creased versions as used on the FT Storch. Here is the semi-assembled wing before folding over the bottom skin.

 

[Piotrsko]

By any chance are you removing the paper from the inner top wing surface? Makes it bend much better doesn't seem to make it that much weaker.

 

[Inq]

By any chance are you removing the paper from the inner top wing surface? Makes it bend much better doesn't seem to make it that much weaker.

I tried that. I even did it selectively from the leading edge back to about 60% which would have gotten it over the main spar / servo. I left the back 40% on thinking it would be stiffer and be more airfoil like if it was near strait. I even tried using a heat gun on the exposed section to hopefully soften it up. It buckled on me anyway and in a not so nice way... thus a fallback and build a second one. I'm sure I just need more experience and practice. But I am beginning to think I bit off more than I can chew with four planes this month!

 

[FlyingTyger]

Don't worry about getting all 4 done. More important to build them right.
Your build looks great so far. Keep chugging along. And I really like how you did the aileron linkages. It's an old-school technique but your 3D-printed parts make it much cleaner. I am putting those parts in my library for future builds. Thank you.

 

[Inq]

Don't worry about getting all 4 done. More important to build them right.
Your build looks great so far. Keep chugging along. And I really like how you did the aileron linkages. It's an old-school technique but your 3D-printed parts make it much cleaner. I am putting those parts in my library for future builds. Thank you.

I appreciate the complement.

 

[Tench745]

I made a quick little video describing/illustrating my technique for curving foamboard without creases. (Production quality is horrible, sorry.) It may or may not be things you don't already know, but hopefully it helps someone. Forgot to note, my table has a rounded edge. Sharp edged surfaces are more likely to crease the foam.

 

[Inq]

Even though I honored the scale drawings accurately...

... I can't help feeling that the proportions don't look right to me once it's in 3D. BTW... the wing came out nicely.

 

[Tench745]

Nope, that looks correct to me. Not having the curved turtledeck changes the visual slightly, but the later German planes were very oddly proportioned to a modern eye.
For flying sake, I recommend doubling the area of the vertical stabilizer, and size up the rudder area by about 30%. WWI planes are all about rudder control, and the German planes doubly so because there is almost no vertical stabilizer, so you have to constantly, manually, stabilize yaw with the rudder.

 

[Inq]

Nope, that looks correct to me. Not having the curved turtledeck changes the visual slightly, but the later German planes were very oddly proportioned to a modern eye.
For flying sake, I recommend doubling the area of the vertical stabilizer, and size up the rudder area by about 30%. WWI planes are all about rudder control, and the German planes doubly so because there is almost no vertical stabilizer, so you have to constantly, manually, stabilize yaw with the rudder.

That's all I need... a difficult plane to fly. Sounds like I chose badly.

 

[Tench745]

That's all I need... a difficult plane to fly. Sounds like I chose badly.

You seem to be doing quite well with the planes you've been flying thus far. It's just something to work up to; like flying a plane with no dihedral. Practice using rudder when you fly. Try initiating turns with rudder, try some flat turns where you use rudder to turn and ailerons to stop the plane from rolling. Practice slips, practice slow flight and using rudder to keep the wings level when at high angles of attack, etc.
A plane that's hard to fly makes a more competent pilot. And hey, if it crashes, that's why we build with foam.

 

[Inq]

D.VIII Progress...

Spent most of my time today on the D.VIII! A lot of head scratching, designing, re-designing, printing, re-designing... ad nauseum. I strive to design structures do double-duty. In this I little piece, I think I've achieved a personal record.

No... it doesn't pick up microwaves.

1. This started out being a motor mount.
2. It still uses the aluminum X-mount as I had a motor burn up and melt an old mount. The aluminum will help dissipate heat before reaching the plastic.
3. I believe I was able to get the CG right even if the battery is tucked up behind the motor. Unlike the FT DR-1 that has to have the battery below the motor. The design incorporates the battery clip to keep the battery located.
4. The main wire landing gear is mounted between the plastic and the aluminum X-mount. The screws holding the motor to the mount, also hold the steel rod. It also places it at the scale positions, so it is hidden within the scale struts.
5. I hope to be able to use bamboo skewers for the parasol wing struts. This design incorporates the lower forward strut positions. This will aid mounting the wing as the structs are positioned for length, and proper, scale angle in all three axes.
6. Finally, the design has walls positioned to fit the foamboard fuselage, centering the motor and has large surface area for good bonding strength.

All this for 10 grams of plastic.

Next... I wanted to add some suspension to the design. I'm hoping my rough landings can be somewhat absorbed by a little give in the landing gear. I'm not sure if you can tell in the photo below, but the music wire comes down to the stub wing between the wheels as expected. But instead of bending out to fit the wheel, it bends in and crosses to the other side. At the center the two crossed music wires are soldered together. This keeps the wheel track constant, but also sets the base of the bending beam wheel spring. The wheel can now travel up while bending the wire outside this center solder joint. If more suspension stiffness is required, two more joints can be soldered out bound from the center one... thus shortening the beam length and thus increasing stiffness.

It's an experiment...

 

[FoamyDM]

Today's progress on the D.VIII

Today's progress was a little slower than I was expecting. Ran in to some hurdles and some re-work.
3D Printed Wheels
The first printing yesterday was not satisfactory. I have updated the resource with a version 2 and explanation for the changes. The second printing went well. The assembly and initial sanding look pretty good (for a 3D print). I will be making another set (slightly scaled down) to match the scaling of the FT MM DR-1 Triplane.
View attachment 234492

Tool - InqCutter
I am not near gifted enough to cut a strait bevel on the foam board hinge lines. As an illustration of my competence I offer the 3" hinge line of the Rudder.
View attachment 234493
This simply will not do... and didn't when I tried to do the leading edge fold on the wing (same as a Storch). I decided that there is a better way and created a 3D printed razor blade holder that holds the blade to cut a 45 degree bevel and blade angled at 30 degrees relative to the cut direction. It also incorporates an offset square so that it cuts the 45 bevel in the perfect place above the paper fold. The InqCutter is in the Resources and will be available after approval.
View attachment 234494

3D Printed Linkage Hardware
I wanted to try using the single servo version for aileron control. I have created the right angle levers and control horns. These are also in the Resources and will be available on approval. The right-angle joints are low profile so they don't stick out. In the Resources, I've included three different versions of the arm so that up/down aileron differential can be incorporated with 0, 10 and 20 degree options.

The Wing
Besides the lousy cutting, I also was wanting to use the rounded top surface used in Master Class planes, but I just couldn't achieve it this small of a wing, so I fell back to the double-creased versions as used on the FT Storch. Here is the semi-assembled wing before folding over the bottom skin.
View attachment 234496

I love the linkage hardware.