WIP: Swappable Piper PA-12 Super Cruiser

[thatjoshguy]

Some data for the number lovers out there:

25" tip to tail
40" wingspan, 6" cord, 240 sq.in. wing area
fuselage is 2.5 inches wide

if the data provided here is accurate, estimated build weight (based on foam area of 638 sq.in.) without electronics, landing gear, power pod, turtledeck, and wing supports should be around 4.5 - 5 ounces depending on glue/tape/etc. SketchUp sure is handy!

plotting the plans as I type this, hope to start building this weekend.

 

[augernaught]

Thanks for the ideas! I tried several ways to get the servos into the tail section, but it really is pretty tight in there. Your model seems to be a good deal larger than mine, and my fuselage is just a bit wider than the power pod (as thick as the foam core on either side).

I like the idea of a popsicle stick on the rudder to stiffen it up, so I may try that. It will fit with my current measurements already. I'm trying to stick to readily available parts/materials as much as possible so that anyone can build this model. For instance, I've designed the landing gear to be similar to the other swappables in that it is made with piano wire, but has a poster board cover to get the look right. Still nice and bouncy too.

My last real concern is the wing. In my current design the wing is glued on. I happen to like that, but the more I think about it it may be better to hold the wing on with rubber bands similar to how NewZee has done. The design doesn't change much, jsut glue the wing or add sticks and bands... guess I can leave it as an option.

If anyone wants an early copy of the plans I can post them. Can't guarantee they'll be super easy to follow but if you have a good eye you can probably figure it out. I'll eventually write up instructions, maybe do a build video with sketchup animations

I went with a rubber banded wing style also. I wanted the option of trying different
wing shapes/thicknesses, and possibly an Armin or KF wing style to see how they changed performance.
Another advantage is that in a crash, the banded wing stands a better chance of less damage
because it is not rigidly mounted, and will have the ability to flex away from the fuselage on impact,
or if I clip the wing on a tree branch and damage it beyond repair, it won't shred the fuse.
Either way I should be able to salvage one or the other and not have to keep rebuilding
entire air frames.

 

[thatjoshguy]

I went with a rubber banded wing style also. I wanted the option of trying different
wing shapes/thicknesses, and possibly an Armin or KF wing style to see how they changed performance.
Another advantage is that in a crash, the banded wing stands a better chance of less damage
because it is not rigidly mounted, and will have the ability flex away from the fuselage on impact,
or if I clip the wing on a tree branch and damage it beyond repair, it won't shred the fuse.
Either way I should be able to salvage one or the other and not have to keep rebuilding
entire air frames.

All valid reasons for the banded wing... I'd be interested to see how NewZee handled the wing supports. I can't tell from the images if they are secured to the wings or just sort of standing there?

 

[augernaught]

This is why i love this community!

Augernaught,

Will you be releasing pland for your design as well?

I had issues with the program I used to make my plans, so I can't say for sure.
I could print them out to scale from my program, but when I tried to save
or convert the plans into something others could use, the scaleing wouldn't remain at 1:1.
Besides, I never had the conventional plans done like you see here on Flitetest.
I only had a top and side profile to work from, and had to lay them on the foam board
and do the tricky stuff, like the spacing for the channel cuts for the A/B folds
and all the wing bend lines by hand right on the board the way NewZee explained to me.

 

[thatjoshguy]

I had issues with the program I used to make my plans, so I can't say for sure.
I could print them out to scale from my program, but when I tried to save
or convert the plans into something others could use, the scaleing wouldn't remain at 1:1.
Besides, I never had the conventional plans done like you see here on Flitetest.
I only had a top and side profile to work from, and had to lay them on the foam board
and do the tricky stuff, like the spacing for the channel cuts for the A/B folds
and all the wing bend lines by hand right on the board the way NewZee explained to me.

what program did you use?

Just a thought - if you can print to a printer, you can print to a file. Should remain scale that way, either a PDF if you have the software, or an EPS that can be converted

 

[augernaught]

what program did you use?

Just a thought - if you can print to a printer, you can print to a file. Should remain scale that way, either a PDF if you have the software, or an EPS that can be converted

I used Coreldraw7, imported a .jpeg 3 view of the Yak Air-5,
and just traced over the outlines of the top and side profiles.
I was able to print out my traced profiles to scale while active in CD7,
but as soon as I tried to save and re-open the files the scaleing got corrupted,
and when I tried to open a converted .pdf file, it showed up as a blank page in Adobe.

 

[thatjoshguy]

I've used CutePDF in the past to print directly to a PDF file. May be worth a shot if CD7 is giving you problems. It basically installs as a printer on your PC, so every program can use it via native print interfaces. As far as the program knows, it's printing to paper (sends the same data). the virtual printer handles the rest. Adobe Acrobat works just as well, but isn't free. If you already have it though it's great.

 

[thatjoshguy]

Cut the tail out, definite flexing issues on the elevators so that needs addressed. Rudder is sturdy though. Also built one wing and it's great

 

[Blackbeltrrf]

Love it! Great work so far!

 

[thatjoshguy]

Ugh! Can anyone confirm if the Spitfire's elevator had flexing issues? I haven't built that one. I modified the area between the rudder as large as I could without ruining the rudder stability, but it's still not very strong. Tried gluing on a gift card but it didn't help much. Any ideas?

 

[augernaught]

Cut the tail out, definite flexing issues on the elevators so that needs addressed. Rudder is sturdy though. Also built one wing and it's great

How can you post something like that without some pics!?!?!
You're killing me over here... :black_eyed:

BTW, Thanks for the CutePDF info. I will look into that, but I sure ain't no computer GURU.

 

[augernaught]

Ugh! Can anyone confirm if the Spitfire's elevator had flexing issues? I haven't built that one. I modified the area between the rudder as large as I could without ruining the rudder stability, but it's still not very strong. Tried gluing on a gift card but it didn't help much. Any ideas?

ummm... that's why I mentioned the "half moon" fix in post # 35 with pics.
It spreads the support to the outer edges of the control surfaces much
better than a popsicle stick, etc. weighs less, and can be constructed out of a
a few layers of gift cards if need be.
But watch any slow motion video of these planes (ex: FT Spit) control surfaces,
and YES, there is still flex/shutter, but you will not notice it in actual flight.
They all do it a bit..... even balsa or fiberglass builds.

 

[NewZee]

All valid reasons for the banded wing... I'd be interested to see how NewZee handled the wing supports. I can't tell from the images if they are secured to the wings or just sort of standing there?

I glued electrical terminal lugs into the underside of the wings, and also crimped the same ring style lugs on the skewers I inserted a cut length of skewer, through the holes in the lugs and wrapped with a rubber band to secure, maybe you can see it a little better in this pic? I must admit that after the first few flights I stopped using the struts, the wing seems plenty strong enough without them!


BTW you dimensions are very close to mine ! 40" WS, 26" OAL, 7" cord

 

[thatjoshguy]

ummm... that's why I mentioned the "half moon" fix in post # 35 with pics.
It spreads the support to the outer edges of the control surfaces much
better than a popsicle stick, etc. weighs less, and can be constructed out of a
a few layers of gift cards if need be.
But watch any slow motion video of these planes (ex: FT Spit) control surfaces,
and YES, there is still flex/shutter, but you will not notice it in actual flight.
They all do it a bit..... even balsa or fiberglass builds.

I rememebr that post, that's why I tried the gift card. It didn't make much of a difference though - maybe it was a flimsy card. Looking at the Spitfire plans though, there's no way my design is any worse than it. I've got about a 16th of an inch more on the connecting section, so mine has to be stronger! LOL. Maybe i'm worried about nothing then. I'll move forward with the build and mod it later maybe. If I change the tail any more it won't be accurate at all.

Nothing fancy to show yet, but here's some pics as requested

Flexy tail


Rudder is decent enough


Wing is basically the same as Spitfire

 

[Jaxx]

Looking good!

 

[adamd]

Man id love to put floats on that thing at blow it up by maby 50%/60%. This thing is clean!

 

[adamd]

Newzee- the strut idea with the ring connectors is genius!!

 

[thatjoshguy]

Got a lot done this weekend, hope to have some pics up soon. Some of my measurements were off, and my build skills are less than perfect, but it's getting there!

 

[augernaught]

Got a lot done this weekend, hope to have some pics up soon. Some of my measurements were off, and my build skills are less than perfect, but it's getting there!

I have seen a lot of people use a wire bent into a squared off " [ " shape to support
the elevator also. They trace the wire outline onto the elevator,
and press a slight channel into the foam board the same way
the wing curves are done so that the wire can be glued into the channel
and remain flush with the surface.

It is placed in about the same location as the styrene "C" piece
I used, but usually on the bottom surface.

That works well because the ends of the wire can be brought
right up to the hinge, and gives support to the entire elevator, front to back,
where a popsicle stick only supports the very thin portion at it's front.

Hope you can picture what I am saying...

 

[thatjoshguy]

Build is going well. Ran into some issues with the poster board top, but I kind of expected that as SketchUp isn't great at handling curved surfaces, let alone flattening them out to make a pattern. I also had to notch out a portion of the tail as I had forgotten to take the movement of the control horn into account... oops! Easy enough fix though. The new version of the elevator is stable enough, I'm no longer worried about flexing.

Agreed that NewZee's use of ring connectors for the wing supports is genius. I'm gonna have to try that

I'll still be releasing the plans, but honestly they'll be more of a starting point open to interpretation than a perfect plan

Test fitting the fuselage:


...and the tail:



...and the powerpod:


Once I had the wing assembled, I couldn't resist getting on some color: