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Dec 19, 2019, 07:10 PM
Just Toss It !!!
MATIN's Avatar
Thread OP
Build Log

*** Zephyr 46 ***

It is time for a smaller sleeker Zephyr…… Zephyr 46!

In the next few posts I will take you through the process that produced this new PSS sloper.

First a little background to get the credits out of the way:
The original Zephyr was a very successful 2009-2010 PSS project mostly associated with dutchydog .
This was the original thread where dutchy politely asked Artsloper for his permission:
As dutchy said at the time : ”..... the Zephyr was a group creation. Artsloper did the origional design work. TFLG did the scale drawings and the graphics.I did the plug and mold.... It was over a two year project and worth all the effort…..”

The original Zephyr prototype was built in July 2009 and flew in 2010
During the years there were a few efforts, serious or not, to make a Mini Zephyr…. Like these guys clowning around in 2013 :

About 2 years ago TFLG started talking seriously about a smaller Zephyr that would be nearly the same size as a typical ISR sportscale PSS model.

I volunteered to CNC mill the plug if I had a digital 3D scan of the original fuselage that I could scale down.
Search began for a digital scanning outfit that would not bankrupt us with their fees….None was found.
So a friend of mine who happens to be the proud owner of a digital scanner volunteered his services in 2017.
So an un-built Zephyr fuselage was sourced and delivered to my friend ..... and the wait began.
Months went by and we didn’t hear from my friend. Our queries didn’t produce an answer to when the scan would be ready either.

So the wait continued.

Sometime in October of 2018 my patience finally ran out and I was reminded of the old saying: “If it’s to be, it’s up to me!”
So I dragged out my own un-built Zephyr fuselage (yes I have one, thank you very much!) and I started to extract the shape of the bulkheads with a simple contour gauge from Home Depot.

I hadn’t signed up for the 3D modeling that would be required absent a digital scan – But there was no scan forthcoming…. so I plodded on.

The night I was importing the manually extracted bulkhead shapes into my desktop, the thought crossed my mind:
"Wouldn’t it be funny if tomorrow I’ll receive the scan?!"

And you guessed it!..... The next day the Zephyr fuselage scan arrived via email!

The original idea was to simply scale the fuselage digital 3D scan you see above, down to the length that we needed it to be, import the data into the CAM software and voila we could CNC mill a plug!

I should be forgiven for being hopeful of a quick turnaround.

Little did I know that the CNC operation would not begin until a year later!
A combination of work, other hobby projects, travels and more importantly, the need to completely model the smaller Zephyr are responsible for the delay.

Why completely model the smaller Zephyr if we already have a perfectly usable scan? you ask.
Well,.... for the simple reason that although the 46” Zephyr fuselage, for the most part, is a scaled down copy of the original, it does not have the same “airframe proportions” of its larger sister. This is because the proportions of wing chord, stab chord and their relation to the fuselage and each other is not the same as the original Zephyr.

On top of that TFLG had a slightly different shape for the tail section in mind where the fin is taller and positioned higher relative to the wing….. what you might call “Ass-High” !

In the image below you see a comparison between the original Zephyr (on the right) and the Zephyr 46 (on the left.) if they were the same size of course!

So TFLG produced a new profile outline for the new fuselage and I used the digital scan of the original Zephyr to extract the shapes of the bulkheads.
I extracted cross sections from the Zephyr scan to ensure fidelity to the original...... But as it turned out, they were not useful in creating the new mesh!
So I had to completely recreate a curve for every bulkhead to ensure a smooth final mesh.

I used the new outline and bulkheads to construct a 3D model in Rhinoceros that is the same size of the original.

This allowed me to be as faithful as possible to the original shapes of the curvaceous fuselage, as I was able to check them against each other.
Once we were happy with the 3D model, I scaled it down to the size required.

Here’s the original Zephyr on the left and the new Zephyr 46 on the right.

From that point on the new wing and stab were constructed and positioned and the fuselage fillets were fitted to the model.

Last edited by MATIN; Dec 19, 2019 at 11:33 PM.
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Dec 19, 2019, 07:11 PM
Just Toss It !!!
MATIN's Avatar
Thread OP
The CNC portion of the project had to wait until I returned from my Australia trip this past September .
The CAM work was straight forward thanks to the lessons I leaned three years ago when I worked on the Tucano plug.

Here are the 3D models for the fuselage and the hatch:

In total I needed to cut two plugs, each in two halves.
And each half required three CNC operations:
1. A profiling cut that would cut the outline of the part.
2. A roughing pass that would remove most of the material from the stock.
3. A finishing pass that would produce the final smooth surface.

For the CNC cutting I used my Probotix Asteroid CNC router.
The first order of business was to fashion a spoilboard that would support the work on the CNC table and allow me to mill two fuselage halves that were identical and of the highest quality.

The spoilboard is double-sided so it can be flipped around for the other fuselage half.

The spoilboard also has special provisions in the tail area of the model to hold the thin fin down. After my experience with the Tucano, I was worried of the thin fin would come loose from the spoilboard and be ruined in the process.

The stock was glued up from a ¾” and 1” pieces of lightweight MDF

No sense wasting material at the aft section. So for the most part the cutter was cutting air back there!

After the outline was cut and the roughing pass was complete, the waste was removed so the finish pass could start.

Here’s the rough-cut plug after the roughing pass and before the finish pass.

The finish pass was performed with a 4mm ball nose cutter with a 10% step-over.
The finish pass took 6 hours per side, bringing the total cutting time for each fuselage half to 8 hours.

Here’s the finished left side plug before it was removed from the spoilboard.

The hardware holding the fin in place was removed and the basswood stubs were ground off :

And here are the two halves of the fuselage. They didn't require sanding:

Next came the hatch plug :

Milling the hatch was not as straight forward as the rest of the fuselage. The “blisters” on the hatch presented an “undercut” to the CNC router that it could not reach in the finishing pass..... You can see the issue in the image below:

The plug to the right is what the first pass produced. You can see material under the blister has not been removed.
The plug at the left shows the results of the second cleaning pass that removed the material from under the blister.

For the cleaning pass the hatch plugs had to be reoriented, re-registered and re-milled to remove the material from the undercut.

The results turned out better than I had dreamed, but the process was daunting and time-consuming.

In total 4 fuselage halves were milled. The first two were test pieces that exposed the potential trouble areas.

The saddle area of the final pieces had be adjusted to fit the saddle plug that we cut so it can be used to finish off the wing fillets.
The saddle plug has the same wing sweep and dihedral as the wings.
So the sweep had to be hand-cut using a chisel into the fuselage plug’s wing saddle.

The material from the hatched area had to be removed .

After that, the fuselage plug and the saddle plug fit perfectly.

Gluing the two plug halves needed to be precise and clean. Hence all the masking tape to protect the finish:

I also cut a parting board using the CNC router from a melamine covered piece of particle board:

.... and here's the full plug fitted to the parting board:

These are the parts to be used in making the fuselage mold.

Here are the plugs that are wrapped for shipping:

And here’s the results of a year and half's worth of work leaving my shop for the C.O.W. so TFLG can finish it off and get it ready for being molded:

You will next hear from TFLG whenever the plug is ready to be molded.

My work is done until we need a Mini Zephyr!
Last edited by MATIN; Dec 20, 2019 at 02:57 AM.
Dec 19, 2019, 07:12 PM
Just Toss It !!!
MATIN's Avatar
Thread OP
Reserved .... just in case!
Last edited by MATIN; Dec 19, 2019 at 07:17 PM.
Dec 19, 2019, 07:31 PM
Auzzie built planks
timbuck's Avatar
Oh my.... yes please
Latest blog entry: More colours
Dec 19, 2019, 07:37 PM
Registered User
Wow it looks....

Even more pointy?!
Dec 19, 2019, 08:52 PM
It's not going to build itself
TRISME's Avatar
pointier and maybe a cup size smaller. Looks fast!
Amazing work!!!
Dec 19, 2019, 09:03 PM
Registered User
Really gorgeous work Matin. Thank you for the write-up.
Kudos to all involved, can't wait to get my fuse!
Dec 19, 2019, 09:24 PM
F3Foamie Pilot

I am very impressed. Actually I'm blown away at the level of work and innovation.

I think a lot of us will be hovering over the "Buy" button.

Thanks, I now feel like a caveman standing next to you.
Dec 19, 2019, 09:38 PM
Gliders ain't drones!
Zenmaniac's Avatar
Quite a beauty!

-= Dave
Dec 19, 2019, 09:48 PM
Old Master, New Grasshopper
toro's Avatar
Boom ! such a great looking model. Looking forward to this.
Latest blog entry: Pics
Dec 19, 2019, 10:04 PM
Yes, ALL your money...
winchdoc's Avatar
Oh ha ha! So that’s what you’ve been up to...

Dec 19, 2019, 10:30 PM
Gliders ain't drones!
Zenmaniac's Avatar
Uh-oh. Looks like Rolls-Royce already hacked your plans for their new electric plane, Matin.

-= Dave
Dec 19, 2019, 11:45 PM
Slow builder
_AL_'s Avatar
I don't care what everyone else says Matin, I say you are a great man!

That is exceptional work mate. I wish I had half your skills.
TFLG better make that mold robust, I get the feeling it's going to get a lot of use. I'll be adding my name to the list when the time comes.

Dec 20, 2019, 01:08 AM
PDX Slope Pilot's Avatar
Dec 20, 2019, 03:28 AM
Epic Win or Epic Fail!
awood12345's Avatar
This is great news, I've wanted one of these for years. Please tell me you'll be selling them! I want one.

I nearly drew up a fuselage to print, this'll save me a bunch of work.
Last edited by awood12345; Dec 20, 2019 at 08:47 AM.

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