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FTFC'18 WWII Vought XF5U "Flying Flapjack" designed by SP0NZ & LocalFiend

localfiend

I like 3D printers...
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#21
Fantastic. I've got a feeling I'm going to need one of these
I'm hoping it will actually be a pretty easy build. If I can get the skin pieces figured out perfectly, applying them is pretty simple.

Tricky bits are going to be the motor pods. Not sure how tightly I can easily roll foamboard. Also gonna want some way to plug them into the fuse. Maybe a carbon/wood arrow or dowel rod for strength.
 

localfiend

I like 3D printers...
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#22
Some more progress. As you can see, everything after the middle section still needs work. Especially the wingtip. It might look better after I get the shape more nailed down, but I'm thinking sanded profiles may be better.

I'll adjust skin pieces, recut, and do the other side. Then maybe do the bottom skins before starting over on another airframe.

Also gonna need some BBQ reinforcement for the rear spar. Everything gets forced down and bends things at the rear. Maybe that won't matter with the bottom on, but I'd prefer not to force things.















 
#24
Awesome work, it's looking fantastic! Looking forward to seeing how you'll squeeze the retracts in there. For the props, you might have a look at the Dynam B-26 props. I think they are the only contra rotating 4 blades out there outside of small miniquad props.
 

DamoRC

Elite member
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#25
Just brilliant work! Did you hand cut the sub-structure pieces? The look like they are laser cut they fit so well.

DamoRC
 
#27
Wow man! Your build is looking great! Can't wait to see this one in the air! As far as how tight you can roll foam board for the engine pods....id say pretty tight. I rolled the nacelles on my little Boeing 314 project. If you look in the attached pic, you can see one on the build table next to a American flag. The diameter is about 1.5 inches. Had to make a lot of relief cuts, but they came out good. I don't think you will have any problems. Your build is really coming out great, wish I was that far along on my Spatz  image.jpeg
 

localfiend

I like 3D printers...
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#28
Awesome work, it's looking fantastic! Looking forward to seeing how you'll squeeze the retracts in there. For the props, you might have a look at the Dynam B-26 props. I think they are the only contra rotating 4 blades out there outside of small miniquad props.
The fuselage/wing is so fat that I think retracts will actually be quite simple. Just need to make a rectangular box for them to sit in, and a simple lid. Maybe we could 3D print some hinges for that. We'll see if Sponz has any ideas, he's the 3D guy.

I more concerned about prop size than 4 blade. To be scale, at this 25" wingspan 16" props are needed lol. Wonder how big I can go with the C pack on 2s.

Just brilliant work! Did you hand cut the sub-structure pieces? The look like they are laser cut they fit so well.

DamoRC
I cheat big time. Built myself a CNC machine, which is excellent for rapid prototyping. Otherwise, all the frame pieces would probably have simpler lightening cutouts. :cool:

Wow man! Your build is looking great! Can't wait to see this one in the air! As far as how tight you can roll foam board for the engine pods....id say pretty tight. I rolled the nacelles on my little Boeing 314 project. If you look in the attached pic, you can see one on the build table next to a American flag. The diameter is about 1.5 inches. Had to make a lot of relief cuts, but they came out good. I don't think you will have any problems. Your build is really coming out great, wish I was that far along on my Spatz  View attachment 91958
Yeah, I've had success rolling stuff tightly in short sections. We'll see how longer pieces work. I may have to split stuff up. At least my tube will be a bit bigger. I sized the plane up enough that they're around 1.75 inches.
 

Tench745

Elite member
#29
When I was building the original cylinders for my Cafe Racer Mk 3 I rolled foam tubes with about a 1" outer diameter. Any tighter than that is probably unrealistic.
Remove the inner paper and use a form to help keep the foam supported when bending or else it can split. The outer paper helps support the foam in tension while the inside of the foam can crush. The only limitations on radius are how strong the paper is in tension and how much the foam can actually crush.
 

wilmracer

I build things that fly (sometimes)
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#30
So... What is the size of this?

Also, any thoughts on perhaps using inrunners with inline gearboxes for the motors? Might help to keep the scale lines and still swing large props.
 

localfiend

I like 3D printers...
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#31
So... What is the size of this?

Also, any thoughts on perhaps using inrunners with inline gearboxes for the motors? Might help to keep the scale lines and still swing large props.
Here's a slightly melted prototype triplane for scale:





Wingspan is 25 inches, which actually has a massive amount of wing area. If this thing ends up weighing 1200 grams it will still have a WCL of 5.3.

I do have some 3110 470kv outrunners and am considering using them with 14" triblade props. Maybe bigger if I can use 2 cell without exceeding wire amp limits.

I have no experience with inrunners. Aren't those generally super high kv? How much gear reduction can you get inline?
 

wilmracer

I build things that fly (sometimes)
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#32
I have no experience with inrunners. Aren't those generally super high kv? How much gear reduction can you get inline?
There are some gearboxes used by glider guys to let them use inrunners and spin some big props. I'll take a look around and see what looks most appropriate. Himax has some that with 3.33 x 1 gear reduction to spin 13x10 props (http://www.maxxprod.com/mpi/mpi-262.html). I've seen gearboxes with 6:1 reduction as well. 16" 4 blades could be possible with enough reduction. Now where to find those props, that's another story.
 

localfiend

I like 3D printers...
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#33
There are some gearboxes used by glider guys to let them use inrunners and spin some big props. I'll take a look around and see what looks most appropriate. Himax has some that with 3.33 x 1 gear reduction to spin 13x10 props (http://www.maxxprod.com/mpi/mpi-262.html). I've seen gearboxes with 6:1 reduction as well. 16" 4 blades could be possible with enough reduction. Now where to find those props, that's another story.
Interesting. Never would have though to look at glider stuff. I'll do some looking and see what comes up. 14-16" 3 bladed props are easy to find. 4 Bladed stuff not so much.
 

wilmracer

I build things that fly (sometimes)
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#35

localfiend

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#36
Motion RC has a few props in this range from their big models. They have a 16X10X4 but I don't see a counter-rotating version.https://www.motionrc.com/collection...products/flightlinerc-16x10-4-blade-propeller

Yeah, plenty of big 4 blade props out there, just not many that have counterrotating pairs. Maybe I'll have to combine a couple props. They were kinda offset on the full scale version anyway.

I'm starting another airframe that will
hopefully have the final skins as a double check. The last one was close, but not good enough. Maybe I'll finish the skins on the old one and do some glide tests.

It's even more skeletal, but I think this thing will be stupid strong anyway.

 

willsonman

Builder Extraordinare
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#38
Figures you guys would ALREADY be on your SECOND prototype before I'm even off the ground. Ben and I have a ways to go but we should be able to carry more ordinance. :p
 

localfiend

I like 3D printers...
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#39
Figures you guys would ALREADY be on your SECOND prototype before I'm even off the ground. Ben and I have a ways to go but we should be able to carry more ordinance. :p
Second? That's for amatures. I've already messed up 3 and am on my 4th. :cool:



But that's just my build style when I'm making plans for complex curved aircraft. Keep recutting and fitting until the CAD is good enough to not bug me anymore. :D

At least I can eat the remains this time. Mmm, maple flavored foam....