Mini XP50 for FTCC World War Two Challenge!

[Waffleman]

FTFC'18 WWII XP-50 "Skyrocket" designed by Waffleman

The rules say 1/20th scale stuff is allowed, so I figured I'd whip up a "little something" to test the waters with scratchbuilding from my own design. I already had a couple good Xnova motors to use, so I settled on the twin engine prototype fighter from Grumman called the XP-50 "Skyrocket.

Well, that's all fine and dandy, but I cant exactly build a plane from that picture alone. So I grabbed a 3-view drawing instead.

That's better.
I'm doing my actual design work in autocad, and I'll release plans for it once they're good enough. It'd be neat if we could have a group of these flying at once.
But I digress.
I didn't really bother to take a lot of screenshots of my plans-drawing process, and screenshots cant really do the thought process behind it justice anyways. But here's one anyways:

Next post: The prototype build

 

[Waffleman]

Step one: Printing, cutting, and taping the plans. They did NOT tile well, I'll need to work on that.

This is what the paper templates looked like. A couple are missing, because I didn't draw them out for a couple parts which I will only know the geometry of once the plane is together.

Step two: cut out the foam. I didn't bother taking pictures of that, there isn't anything new to see in THAT process.
Step three: build a plane.


I wish I had photographed how the mini power pods are actually held in there before I put the cowlings on. I guess you'll just have to guess for a little while

This is the point where I needed to make those few parts. It was just the fuselage top cover, really.

This is where the battery hatch is as well.

And now, electronics. Would have been a LOT easier to do it during the build instead of after. As it is, the ESC wires are just taped to the bottom of the wing. When I build a new one, they'll go inside and it'll look a lot nicer.

Next up: Flight!

 

[liamnave]

That looks really coo! When you clean up the build a bit and paint it that thing is gonna be awesome! One question, it seems to me that the tail surfaces are small. I'm curious to see how it does it flight. Good Luck!

 

[Air-headed Aviator]

Looks nice and clean, I also salute the building of the Skyrocket. The first Twin I was planning to build originally was gonna be inspired by its earlier rendition, the XF5F. good luck on your eventual maiden.

 

[Waffleman]

Yes, it does fly.
https://www.youtube.com/watch?v=3250CUgRnf8
I'd say it flies pretty decent. It's no trainer, you can definitely tell it's a warbird, but it handles surprisingly okay as long as you don't push it too hard. It snap rolls pretty hard, and can tipstall, but usually wont. Instead, the elevator just stops having noticeable effect when you shut off the motors. it's plenty sensitive enough even with light power, but the moment the props stop, so does the pitch authority. It certainly doesn't glide well. I think it's those big nacelles, it just doesn't get airflow over the tail when there's no propwash.
It's got decent power. Not quite as fast as I was expecting, honestly, but it will go straight up with ease. And I've only flown it on 3s 1000mah so far, I wonder what it'd do on 4s... I know the power system can handle it.

 

[Waffleman]

That looks really coo! When you clean up the build a bit and paint it that thing is gonna be awesome! One question, it seems to me that the tail surfaces are small. I'm curious to see how it does it flight. Good Luck!

I was expecting to have to change it, but it feels stable in flight as long as I keep propwash over it. I'm going to keep it scale, at least for now, I'd rather sacrifice low speed handling than the looks.

Looks nice and clean, I also salute the building of the Skyrocket. The first Twin I was planning to build originally was gonna be inspired by its earlier rendition, the XF5F. good luck on your eventual maiden.

I'd like to see an XF5F done, but I probably wouldn't do one myself. I could see balance being an issue. I was honestly expecting a balance issue on this build, but the battery actually sits slightly BEHIND the CG on this one since the motors are so far forward. So an XF5F might be possible, I don't know.
As far as "eventual maiden" goes, check the video i just linked in my other reply. Well, that was the second complete flight, third total. The maiden went bad because my elevator trim was way off, so I thought it was tailheavy, until I slowed down and it borked the nose in. Not bad enough to prevent flight, so I fixed the trim and flew it again a couple times with much better success.

 

[Air-headed Aviator]

I'd second that "flies pretty good" sentiment. Some under-cambered wing tips could help with them tip stalls, and if pitch authority continues to be a problem you could always do some "sneaky construction" and widen the H stab a bit for greater elevator throws.

 

[Michael9865]

Congratulations

 

[PsyBorg]

That came together pretty darn fast AND flys well for a first run. Awesome job mate. :applause:

 

[Grifflyer]

Oh boy, now we've got some competition me and JimCR120 are doing the same plane but with a different fuse
http://forum.flitetest.com/showthread.php?36045-FTFC-WWII-Grumman-XF5F-JimCR120-and-Grifflyer

 

[rockyboy]

Holy smokes that was fast work!! Congrats! :applause:

I think you'll have the first fully completed entry by far - perhaps even before I start the official challenge thread this weekend!

Now you can spend the rest of the challenge time with a combination of polishing this and working on your second entry

 

[Waffleman]

Oh boy, now we've got some competition me and JimCR120 are doing the same plane but with a different fuse
http://forum.flitetest.com/showthread.php?36045-FTFC-WWII-Grumman-XF5F-JimCR120-and-Grifflyer

I looked at your thread, if you guys want to use some of my work for your A-pack sized version, you're welcome to it. My wing is 25" to be at 1/20th scale though, not the 30" you guys were thinking of. It will probably be a little bit before I release plans - I want to build a second one with a few changes to make sure it all fits correctly - but it definitely looks like it could use the same wing design on both yours and mine.

 

[TrRC68]

Waffleman,
Any chance of getting a beta set of plans for the XP-50? I'm looking for something to do over the winter build season. I have about 4 solid months of unflyable weather to look forward to. Have you had a chance to build your second version yet?