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Mar 15, 2018, 03:50 PM
Aurora Builder
Very nice work Alex. I am certainly very interested in your Matlab simulation suite, especially the claim that your viscous drag calculation is more accurate than XFLR5, but that may be a conversation for another thread or PM.

The molds look great, and I would love to hear more on 3D printed molds. I assume you are finishing the ABS either through sanding or otherwise sealing it out?
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Mar 15, 2018, 04:37 PM
a quantum of science
Alex Guffler's Avatar
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Quote:
Originally Posted by krikkens
hello Alex,


could you share more info about the third last picture? yellow mold with roving with carbon sock around?
i assume it's the sparjoinder mold ?

i would think you could shed weight from the sparjoiner , sub 4gr should be possible i think with foam core and UD/roving tapered down towards the ends
Yes, It is the spar joiner. Still a little heavy with the rovings and the carbon sleeve. We will optimize the layup. And yes, it is still too long. So something about 4 g is realistic for the final layup and length. We will glue the joiner into the wing in the left side and make a kevlar sleeve pocket in the right wing.
I can take some better pictures next time I am at the workshop.
Mar 15, 2018, 04:48 PM
a quantum of science
Alex Guffler's Avatar
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Quote:
Originally Posted by samc99us
Very nice work Alex. I am certainly very interested in your Matlab simulation suite, especially the claim that your viscous drag calculation is more accurate than XFLR5, but that may be a conversation for another thread or PM.

The molds look great, and I would love to hear more on 3D printed molds. I assume you are finishing the ABS either through sanding or otherwise sealing it out?
The drag estimation is more accurate than xflr5, because it calculates drag for all spanwise airfoil cross-sections. It uses the actual Re number applying locally. XFLR5 does this by interpolating from precalculated Re-range polars. And for special tasks like high-lift situations I can use MSES instead of XFOIL.
Maybe I will publish my version of Tornado vortex one day, but it will need some cleanup first ;-) And I should talk to the original autors of Tornado Vortex before doing that. Concerning MSES: You can only get it from Prof. Drela for academic puroposes. As we are an academic and non-commercial team, we may use MSES for our projects!

However I would say XFLR5 is really great software and works fine for DLG design. If it had a command line interface, I would have used XFLR5 instead of debugging and extending Tornado Vortex. Combining design tools with optimization algorithms is the real deal!

We printed the fin molds from ABS and just polished it with a polishing machine. The ABS gets really smooth and shiny! Of course, it is not as exact as a "real" mold.
Last edited by Alex Guffler; Mar 15, 2018 at 05:00 PM. Reason: typo
Mar 15, 2018, 05:11 PM
a quantum of science
Alex Guffler's Avatar
Thread OP

Wing molds


I saw that the most clicks were on the image with the wing molds. So I decided to offer some more CAD screenshots.
And yes, both my team mates at university and me at my job have CATIA V5 licenses, that we can use! ;-)

Unfortunately, we could not make the molds longer due to machining space limits. But it shoud work anyway.
The wing molds are from 30mm blocks, fuselage molds from 50mm blocks. All molds are master molds, from which we make carbon fiber production molds. I hope that we can make prepreg fuselages one day!
Mar 22, 2018, 03:23 PM
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Alex Guffler's Avatar
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All master molds milling completed


There is great progress! We recieved the wing and fuselage master molds today. The set of molds is complete now! There's still some work to be done, but the team is highly motivated.
We also demolded the second half of the fin production mold and the elevator production molds. They feature groves, which will be ribs in the production molds for seperating the aerodynamic control surfaces. I guess almost everybody in the current F3K scene uses this technique.

Personally, I am really looking forward to building the first fuselages. The "Bachelor" fuselage was really hard to build because of some ugly edges. The "Ascender" fuselage idea is to keep things simple, straight and smooth. And thus hopefully lightweight.

I am really impressed by the videos with sub 200g DLG's. I don't know if it will be feasible, but if we can get an Ascender in something under 220g, the airfoil design will begin to really pay off, as the Ascender will still be able to fly at windy conditions and penetrate ;-)
Mar 22, 2018, 07:05 PM
Registered User
Rollo340's Avatar
Very impressive, Alex...
Mar 23, 2018, 08:48 AM
Aurora Builder
Nice Alex. How did it go pulling molds with built-in hingelines from the plugs? I would be concerned about breaking that part off during release...

I'm looking forward to a flight report, that wing looks like a high launcher.
Mar 24, 2018, 04:17 AM
a quantum of science
Alex Guffler's Avatar
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Quote:
Originally Posted by samc99us
Nice Alex. How did it go pulling molds with built-in hingelines from the plugs? I would be concerned about breaking that part off during release...

I'm looking forward to a flight report, that wing looks like a high launcher.
Thanks! We will see very soon how it launches. I hope by beginning of May we will have the first Ascender planes

Yes, in the beginning, we were concerned of breaking the hingelines. Thats why we built a test piece (see post #39) with different geometries. We tested different layups for the hingeline rib in that piece as well. My team mates figured out a building method which is durable and demolds well. I will ask the guys to take some pictures when they build the wing molds.
Mar 24, 2018, 08:13 AM
Registered User
Quote:
Originally Posted by samc99us
Nice Alex. How did it go pulling molds with built-in hingelines from the plugs? I would be concerned about breaking that part off during release...

I'm looking forward to a flight report, that wing looks like a high launcher.
The molds pulled fine from the plugs thanks to the angle of 10° of the built-in-hingelines. We used a lot of release wax on grooves in the master molds to make shure everything would separate fine.
The layup on the hingeline begins with two layers of molding resin, followed by two stripes of 50 g/m^2 glass fiber only in the grooves (with a bit of overlap into the rest of the mold). Atferwards we filled the remaining hingeline-cavities with carbon rovings and thickened epoxy. Then the standard layup of the mold consisting of 2x50g/m^2 glass fiber, 2x110g/m^2 glass fiber and 3x160g/m^2 carbon fiber (twill weave) is build.

With a bit of caution during the demolding process everything comes apart nicely. We are still curious about long term stability of the ribs.
Mar 24, 2018, 09:06 AM
a quantum of science
Alex Guffler's Avatar
Thread OP
Quote:
Originally Posted by The Pitcher
The molds pulled fine from the plugs thanks to the angle of 10° of the built-in-hingelines. We used a lot of release wax on grooves in the master molds to make shure everything would separate fine.
The layup on the hingeline begins with two layers of molding resin, followed by two stripes of 50 g/m^2 glass fiber only in the grooves (with a bit of overlap into the rest of the mold). Atferwards we filled the remaining hingeline-cavities with carbon rovings and thickened epoxy. Then the standard layup of the mold consisting of 2x50g/m^2 glass fiber, 2x110g/m^2 glass fiber and 3x160g/m^2 carbon fiber (twill weave) is build.

With a bit of caution during the demolding process everything comes apart nicely. We are still curious about long term stability of the ribs.
Here is the exact information by one of our master builders
Mar 24, 2018, 08:03 PM
AERO+
nickbox's Avatar
Very nice Alex, a wonderful design.
seems you are going to make it carbon mould from positive mould you showed? would be appreciated to see more detail how to do that.
Mar 25, 2018, 04:34 AM
Registered User
Quote:
Originally Posted by nickbox
Very nice Alex, a wonderful design.
seems you are going to make it carbon mould from positive mould you showed? would be appreciated to see more detail how to do that.
All molds will be carbon molds, we only use fine glass fiber in the first layers to get a better adhesion between the molding resin and the heavier carbon fiber. We can try to take a few pictures when building the fuselage or wing molds but it will take a few weeks before we get to that. First we have so sand and polish our master molds.
Apr 03, 2018, 02:47 PM
a quantum of science
Alex Guffler's Avatar
Thread OP

Sponsoring 3M


We would like to thank 3M, who supported our project with some transfer tape ATG 926 (12mm) und ATG 924 (19mm).

In the German RCNetwork thread about our project, Jan Henning suggested to use the transfer tape and we are absolutely amazed.
It is perfect for fixing carbon and glass fiber stripes to the leading edge and flap spars. It's really easy to work with. First we apply the tape onto the carbon fiber fabric, then we cut the material into stripes. These stripes stick well on the foam cores and the fibers can be impregnated with resin then. Nevertheless, the tape is very lightweight.
Apr 03, 2018, 03:00 PM
a quantum of science
Alex Guffler's Avatar
Thread OP

Sponsoring Vladimir's Model


Vladimir Gavrilko was so kind to support us with Carboline 39 g/m^2 and 26 g/m^2. Our master builders say that it's a pleasure to work with it. Soon, our first "Ascender" wings will be laminated from this material!
Apr 03, 2018, 03:10 PM
a quantum of science
Alex Guffler's Avatar
Thread OP

Sponsoring Ebalta


We have been using ebaboard PW920 for many years in different projects, a block material from the German manufacturer Ebalta. It is well suited for milling positive and negative molds with our milling machine. To improve surface quality to perfection, Ebalta supplied us with pore filler for free. The pore filler is applied after rough sanding and it closes the remaining pores in the mold. After 30 minutes drying, the mold can be continued sanding/ polishing. We tested the material already at our canpoy molds, the result can be seen in the attached pictures!


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