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As secretly hoping to use our carbon fibre parts as a common ground for overall power distribution, I thought it would be good to actually measure how it is doing in a context of our other options. The plan is to measure the material resistance and voltage drop for copper wire, aluminium bar and our CF tape on 1m of material.

Copper

Our first testing subject is 25A 2 Core Tinned DC Power Cable from Jaycar.

Running it through a nice cable calculator, we should be seeing following readings – expected resistance to be 5.8 micro-ohms.

Now to our actual measurement.

Well, we measured 0.3 ohm. That doesn’t seem to be correct as this would be 100 times higher value than what calculator shows. Voltage drop was 5.87 mV.

Aluminium

Our second testing subject is Metal Mate 20 x 1.6mm 1m Aluminium Flat Bar from Bunnings warehouse.

Running it through our nice cable calculator again, we should be seeing following readings – expected resistance to be 0.8281 micro-ohms.

Now to our actual measurement.

Well, we measured 0.4 ohm. That doesn’t seem to be correct as this would be again 50 times higher value than what calculator shows. Voltage drop was 0.6 mV. This value is lower than with copper as we have more much more cross-section area here (10 times more).

Carbon Fibre tape

Our last testing subject is 12k 200gsm 4″/10cm width Carbon Fiber Uni-directional Cloth UD Fabric Tap High strength Repair material Tensile strength 3400Mpa from AliExpress.

Unfortunately our calculator doesn’t know Carbon Fibre material, but as it didn’t help much for that copper and aluminium before we’ll just go ahead. Seb prepared aluminium clamps so we have something to connect to.

First reading came with 8 ohms resistance, what seems to be roughly 20 times higher value than for the others. As were trying to measure the voltage drop, we needed to put weights on those clamps to improve connectivity. Still, we measured quite high 1.2V drop just on that 1 meter!

So putting it all in a table:

Honestly I am not sure what to make out of this. Does this still qualify to be used as our common ground? I suppose someone with more insight into electricity needs to have a look. It is not a big deal if this is not ok, but we’ll have to count with additional weight for doubling our power cables.

Update from Richard 2023/1/23

You can connect it to GND, but you can’t use it for electrical GND for return currents. So you really want to be using:

P=I^2R
So if 2A flows P=32W

Update from Chris 2023/1/23

Resistance is different in different directions on carbon fiber as well – and almost none between layers. CF threads are “wet” with a chemical which helps the resin absorb – if you’re wealth enough to grow carbon nanotubes on the CF to use as the wetting agent, you then get excellent conductivity in all directions.

Or the opposite of that technology – when you don’t use nanotubes, conductivity is poor. Multi-Functional Carbon Fibre Composites using Carbon Nanotubes as an Alternative to Polymer Sizing – what’s the ground for? If it’s the high-current for the motors, perhaps some copper tape laid along with the fibers when you make the tubes like below?

There’s been also big comment from Adam, see in comments below.

Thank you guys!

Carbon fiber tube curing process, we are working at, needs to go through several stages. First one is to hold temperature on 70C for ~3hrs, followed by another 1.5h on 140C. To be able to achieve that, we needed to put together some sort of thermostat which would drive our heater.

Discussing this problem all around, Richard suggested to build our own and provided list of parts needed.

So we got ourselves one MAX6675 K-type Thermocouple Temperature Sensor 0-600 Degrees Module Arduino – mainly to grab its signal amplifier.

Followed by AU Heat-resistant K Type Stainless Steel Thermocouple Sensor Probe Meter (1m) as it comes with pretty impressive operating temperature range: -100 – 700°C.

Both packages arrived quickly (days).

It took Seb to hook it up to one his Arduino.

Sebi provided me with a code, claiming that that’s just a copy & paste from some thermocouple example. I am putting it here for reference, while all credits go to Adafruit guys.

// this example is public domain. enjoy!
// https://learn.adafruit.com/thermocouple/

#include "max6675.h"

int thermoDO = 4;
int thermoCS = 5;
int thermoCLK = 6;

MAX6675 thermocouple(thermoCLK, thermoCS, thermoDO);

void setup() {
  Serial.begin(9600);

  Serial.println("MAX6675 test");
  // wait for MAX chip to stabilize
  delay(500);
}

void loop() {
  // basic readout test, just print the current temp

  Serial.println(thermocouple.readCelsius());

  // For the MAX6675 to update, you must delay AT LEAST 250ms between reads!
  delay(1000);
}

Finally we took a tiny video to see it all working together – showing data from Seb’s Arduino being received by a plotter on his laptop responding nicely to temperature changes.

Afterwards we did some attempts to hook it up with Richard’s MosFETs to drive our heating coil, but that didn’t work out well, so keeping it for another post as there is quite a live discussion running around it right now.

Also there is a question of an actual driving of our heater as it will certainly react with some delay following the hysteresis curve, but that’s for another day as well.

In continuation of our Tubes story, we’ve hit several delays and proper celebration of New Year 2023 was one of them. However there were others…

Adapter jig

Initial plan was to have both tubes (50mm and 60mm) as one component and do all tube cladding like that. Seeing how potentially fragile is that heater made me rethink further steps. I assumed that would be much better to do all preparatory works on that 60mm tube only and use the internal heater when needed only. This obviously called for a new set of jigs to allow our thick tube handling.

Practically that meant to develop an adapter which would allow to extend our 60mm tube and plug it into our 50mm wall mount. Bit of OpenSCAD design and couple days of printing worked out nicely.

Wall mount upgrade

Another obstacle appeared when testing the heater. Our current wall-mount made out of ABS didn’t give me enough confidence that it will withstand whole working cycle reaching 150C for 90 minutes. It actually seemed like it started loosing its internal integrity anyway.

Using the graph from arpnjournals below, it is obvious that we can rely on ABS on up to 110C only.

Thinking about which material to pick instead and how to actually make it happen, Serge appeared and offered his help.

A day later we ended up having new wall mounts. 🙂

Material – TR-102 REGULAR PASTE WAX

Checking on all material, we’ve been able to get our hands on, there were few interesting bits. The first one was a mold decoupling wax. Looking around it worked out that the best fix will be for TR-102 REGULAR PASTE WAX from Barnes Australia.

It arrived in an excellent condition – thanks to our sponsor Tam!

Material – Carbon Fiber tape

Next part was to get our hands on a Carbon Fiber tape. I’ve ended up picking 12k 200gsm 4″/10cm width Carbon Fiber Uni-directional Cloth UD Fabric Tap High strength Repair material Tensile strength 3400Mpa. Thinking about it a bit later, I should probably pick bidirectional woven instead, but well we need to start at somewhere.

As before, it arrived in an excellent condition, couple weeks later.

I’ll leave you here so this post doesn’t go forever, but here is a tiny TODO list what to expect next:

• Getingh the high-temperature Epoxy Resin
• Develop thermal control system for our heater
• Apply first layers of decoupling wax at our molding tube

See you soon!

Bit late, but well, airships don’t need to rush – why to be fast, when you can enjoy being slow. 🙂

This is a continuation of the Back to Tubes – Mounts and Adaptors article. Here we’ll finally focus on real action when wiring the heater tube and finally doing some initial testing.

In preparation of the heater tube winding, I first did a review of all the material we’ll need.

The most important part of this ended up to be a set of heat resistant 11 AWG cables, so we can lead them from inside of the tube. (This is actually why our previous attempt couple weeks back failed right at beginning.)

Drilling holes in our 50′ aluminium pipe was the first step, followed by initial wiring and cable insulation.

The next stage was where all the fun started and we needed Serge and Seb! Unfortunately I haven’t been able to take a video of that initial tube winding, but we ended up multiple runs when re-aligning these threads, which I’ve been able to document.

Making that thread consistent ended up being quite tricky and after several attempts Seb came with a classical hair brush which did the best.

Still I took more than few pictures from all that process.

Final step was to test it all.

We took temperature and width measurements and it all worked out. Serge thinks that that tube expanded roughly 3 paper widths.

Finally we ended up having a visitor – Paul, who participated by supervising whole session and came with a way to measure tube temperature through the paper as it was reflecting the thermometer laser. 🙂

Well, all done for now. Seb is still preparing a jig which would allow us to control heater’s duty cycle, but that will be for another article again.

This is a continuation of the Back to Tubes – Theory & Shopping article. Here we’ll focus on some CAD design and 3D printing.

To be able to do all wire & tape winding on a tube we ended up with a need of several gadgets / jigs, namely wall mount, vise mount, levers and mount adaptors. Wall mount and the vise mount was in place already and seemingly holding ok.

While using an electric drill later in videos, we also prepared a lever with a handle.

OpenSCAD handle code here:

//Lever
module lever() {
  D() {      
    union() {
      //main body
      D() {
        union() {
          Tx(75)
          cube([146, 56, 16], center=true);
          cylinder(16, 28, 28, center = true);
        }    
        T(148.4, 506,0)
        cylinder(21, 500, 500, center = true, $fn = 1000);
        T(148.4,-506,0)
        cylinder(21, 500, 500, center = true, $fn = 1000);
      }
      //small ring
      Tx(150)
      cylinder(16, 10, 10, center = true);
      }
    //Main hole
    cylinder(21, 24.5, 25.5, center = true);
    //Small hole
    Tx(150)
    cylinder(21, 8, 8, center = true);
  }
}

//Handle
module handle() {
  D() {
    union() {
      T(150,0,50)
      cylinder(100, 8, 8, center = true);
      T(150,0,10)
      cylinder(2, 10, 8, center = true);
      T(150,0,100)
      cylinder(2, 15, 15, center = true);
    }
    //central hole
    Tx(150)
    cylinder(210, 6.8, 6.8, center = true);
  }
  
  //reinforcement
  T(150,0,50)
  cube([1.3, 14, 100], center = true);
  T(150,0,50)
  cube([14, 1.3, 100], center = true);
}
  
lever();
handle();

Final product worked out nicely.

Final missing part was a set of tube adaptors (60 -> 70mm) so we can reuse mounts we have for a wider tube. (I made it probably little more fancier than it needed to be, but it is sometimes difficult to hold back. 😉 )

OpenSCAD adaptor code here:

module big_tube_adapter() {
  D() {
    union() {
      cylinder(180, 25, 25);
      Tz(140)
        cylinder(40, 27.1, 27.1);
      Tz(40)
        cylinder(100, 27, 29);
    }
    Tz(-1)
    cylinder(182, 23, 25);

    Clamps = 4;
    for (i = [0:1:Clamps]) {
      R(0,0,i*(360/Clamps)+45)
      T(0,70,90)
      scale([0.3,1.3,1.2])
      sphere(50);
    }
  
  }
  
  //reinforcement
  T(0,0,90)
  cube([1.6, 50, 180], center = true);
  T(0,0,90)
  cube([50, 1.6, 180], center = true);
}

big_tube_adapter();

Slicing in Cura:

Final product:

Well, that wraps it up for this post, next one will be finally some action about wiring and testing.

This article is a follow up on our previous tube development covered here, here and here.

I had to remind myself on what we are trying to achieve here a bit and rethink it again. So for our actual project we need to develop a tube which will serve as a central duct and airship keel. It has to be ~6m long, roughly 6-7cm diameter, super-strong and also super-light. Yes, whole tube needs to be under 1kg to make it working, even better under 800 grams.

The idea is to end up with a scale-able jig which will allow us to produce continuous tube without a need to do some vacuum bagging or autoclave usage.

I made a simple draft on how that’s plan to work out.

So reading it sort of left to right there are two main parts, heater and mold pipe. For a heater we’ll get an 50′ aluminium tube, wrap it in Kapton tape, wind it in 18AWG 80m wire and apply two more Kapton tape layers.

Second part starts with another aluminium tube, now 60′ which will serve for the heat distribution and molding. First layer will be actually a set of decoupling wax layers (6) followed by a first carbon tape (200gms) clockwise winding, hand-applied resin, second carbon tape layer (200gms) counter-clockwise, finishing with very thick layer of office tape (1mm thread) to squeeze out excessive resin and air.

When done, the plan is to achieve a curing plan when on 3 Hours at 25˚C plus 2 Hours At 155˚C and attempt get tube parameters around as described in article Effect of Thermal Exposure on Residual Properties of Wet Layup Carbon Fiber Reinforced Epoxy Composites.

Translated in a table from here it practically says that we need to shoot for 90 minutes curing at 150C.

Percentage Change in Characteristics.

Shopping

In preparations we needed to do some additional shopping first. First thing on my list was a demoulding wax. Picked the best out of the best (and probably also the most expensive) TR-102 REGULAR PASTE WAX from Barnes.

Well, why not to get the best, when we have such a generous sponsors like Tam (huge thanks Tamara)!

Second essential was to order a Carbon Fiber tape – after some serious thinking, we ended up with 12k 200gsm 4″/10cm width Carbon Fiber Uni-directional Cloth UD Fabric Tap High strength Repair material Tensile strength 3400Mpa. It is on its way.

The final missing part is Epoxy, this is still to be decided on which one to use, secretly hoping to get our hands on EPOXY RESIN 4 HIGH TEMPERATURE FIBERGLASSING & CARBON FIBER PREPREG RESIN 80 as it seems to be perfectly what we need.

Next on the list is some CAD design and 3D printing as we need jigs to hold our tubes and operate them in general. I am splitting it into another post so it remains readable.

Thanks to Sebi, we’ve got some new 45A ESCs, which looks awesome.

While replacing the old ones, which burned out, it let us thinking about why we are actually getting so many burned out ESCs? Sometimes those burn without any actual load, just connecting them to a battery is enough to get a “smoke” situation.

Discussing this with Richard he suggested to implement a power soft-start design to reduce initial kick (inrush current) to those electronic components. THE ULTIMATE GUIDE TO SOFT START DESIGN article provides detailed description of this problem, including several options on how to address it.

The basic solution to this is trivially simple – limit the inrush current by adding a power resistor in series with the load primary.

Which very much correlates with Richard’s version (recommending to use 10 Ohm 5 Watt Wire Wound Resistor):

Intention here is to achieve something like on a the measurement below – reducing those current spikes to a level where our 100A battery won’t cause any harm.

After the inception phase, our project started with some decent shopping.

1 x 10 Ohm 5 Watt Wire Wound Resistor

2x DPDT IP56 Heavy Duty Toggle Switch

… well and to be little bit fancier – a Missile Switch Protective Cover!

We also couldn’t avoid bit of 3D design & printing for the switch case.

Finally, it’s just about putting it all together.

Final assembly done!

I had a chat with Ken Macken (modern day MacGyver) on some other topics, when he surprised me with a note on the ChatGPT – that he dared asking it “How do I make a business out of a global blimp transport service?” and it came with pretty cool answer. Well and as ChatGPT resonates these day through all the media I thought to make it in this post.

So let’s start from beginning – what exactly is the ChatGPT? ChatGPT is a chatbot developed by OpenAI. ChatGPT is built on top of OpenAI’s GPT-3.5 family of large language models, and is fine-tuned with both supervised and reinforcement learning techniques. (taken from Wikipedia)

You can already find some good videos explaining ChatGPT on Youtube, I liked this one:

Anyway, back to our original topic, Ken asking “How do I make a business out of a global blimp transport service?” got following answer:

GPT3: To make a business out of a global blimp transport service, you will need to conduct thorough market research to determine the feasibility and potential demand for such a service. This should include identifying potential customers and their needs, as well as any potential competitors and the market conditions they will be operating in.

Once you have a clear understanding of the market and the demand for a blimp transport service, you can begin to develop a business plan. This should include a detailed description of your proposed service, as well as a financial plan that outlines your projected costs, revenue, and profitability.

You will also need to secure funding to purchase or lease blimps and other necessary equipment, and to hire and train staff to operate the service. This may involve seeking investors or securing a loan from a bank or other financial institution.

Additionally, you will need to obtain the necessary licenses and permits to operate a blimp transport service, and ensure that your blimps and operations meet all relevant safety and regulatory requirements. This may require working with local, national, and international authorities to obtain the necessary approvals.

Overall, starting a business in the global blimp transport industry will require significant planning, market research, and financial investment. However, if there is a strong demand for such a service and you are able to offer a high-quality, reliable service, it could be a lucrative and rewarding business venture.

I obviously liked a lot that last paragraph. 🙂

Our business case just arrived! 🙂

France has been given the green light to ban short haul domestic flights – opening this opportunity to other alternative transport options. Thank you France

More in the original article here.

As per our fist steps into optocoupler world seemed worked out nicely, we’ve ventured to roll out full scale implementation which would cover all our 12 servos.

Progressing with wiring that altogether we’ve reached a dilemma how to actually give them some more practical form. The most plausible idea came to organise them in a triangle.

Finishing that assembly we ended up with some indescribable blob of cables. It needed few iterations to give it some reasonable form and reduce number of all cables.

Mainly, looking at it it instantly reminded me of a famous Flux Capacitor from the Back to the Future movie. 🙂

Anyway, it took us another week to plug it in and see it all in action.

We’ve agreed with Sebi that it looks like those ghost signal were substantially reduced and overall responsiveness seem to improved as well! That cabling is still quite silly, but that’s just an opportunity for improvement.

Passing our Hydrogen generation test and also having our new Hydrogen detector in place, it’s been time to move forward. First stage was to review leftovers from a previous day together with checking whether there’s been any impact to our Teflon coating.

It worked out that there’s been some more material in there, while coating came out without any scratch or signs of decay.

To test everything works and also to get rid of any excessive air in the container we filled another blimpy first and took some cool pictures of our dramatic sky

Seb’s been having fun with his new friend.

And we started filling the Windreiter envelope.

As you can see from the gallery below, it actually took few hours to get us there. Luckily chemical reaction stabilised nicely so we’ve got pretty stable Hydrogen production.

Finally we’ve ended up with some super-cool blimp!

Last bit was when we measured the lifting power to confirm achieved Hydrogen purity.

As you can see our kitchen scale measures 171g, where advertised value should be 195.60g of lift at Sea Level H2.

That’s roughly missing 25g, which we accounted to the thread attachment metallic clamp, sealing clamp and potential Hydrogen impurities as our experiment has long way to a clean laboratory environment. Whatever it was I think we did pretty well and whole team was very happy about the outcome! 🙂

Next morning after our initial Hydrogen generation test, I’ve realized that couple months back we’ve bought several MQ8 Hydrogen Gas sensors for our Arduino and this would be also an excellent opportunity to check if & how that’s working.

So I asked Seb and Christopher to put it together and about an hour later – voila – they had it working!

Arduino code looks pretty straightforward.

long sensorValue;
void setup() {
  Serial.begin(115200);
}
void loop() {
  sensorValue = 0;
  for (int i = 0; i < 100; i++) {
    sensorValue += analogRead(A0);
  }
  sensorValue = map(sensorValue/100, 0, 1023, 100, 10000);
  Serial.println("ppm: " + String(sensorValue));
  if (sensorValue > 300)
    tone(3, sensorValue/5);
  else
    noTone(3);
  delay(100);
}

As you may see on video below, they also added a “buzzer” to signal number of particles detected and connected it to a plotter to show values on a graph. They are using hydrogen from a previous day to test that it is really working.

Having that buzzer there came later pretty handy as it served us well to detect all the leaks whilst generating hydrogen, but that’ll have to wait for another post. 🙂

In follow up on our latest adventure in Envelope from Windreiter we’ve ended up some amazing progress this weekend. Our plan was to get heaps of it from Aluminium and Sodium Hydroxide Reaction | Al + NaOH.

Christopher dug out for us how it should work – one sodium atom, one oxygen atom, and one hydrogen atom make up this compound. When all of the molar masses of the constituents of sodium hydroxide are added together, the result is sodium hydroxide’s (NaOH) molar mass. Thus, 22.989g/mol+15.999g/mol+1.008g/mol=39.996g/mol.

So approx 40g of caustic soda = 1g hydrogen.

Molar volume, or volume of one mole of gas , depends on pressure and temperature, and is 22.4 litres – at 0 °C (273.15 K) and 1 atm (101325 Pa), or STP (Standard Temperature and Pressure), for every gas which behaves similarly to an ideal gas. The ideal gas molar volume increases to 24.0 litres as the temperature increases to 20 °C (at 1 atm).

For an ideal gas, the attractive or repulsive interactions between the molecules of gas can be neglected, therefore we can treat this gas as “ideal”. (Side Note: interaction forces between specific gases create conditions for non-ideal gas situations)

The actual molar volume of hydrogen can be exactly calculated from the experimental density of that gas, that is 0,0899 g/L at 0 °C (1 atm ) and 0.0837 g/L at 20 °C (1 atm), knowing that one mole of dihydrogen (H2) amounts to 2,0159 g/mol. Thus, if 0,08988 grams amount to 1 litre, a mole will be as big as 2,0159/0,0899 = 22,42 litres at STP (0 °C – 1 atm) and 2,0159/0,0837 = 24,1 litres.

These values of true molar volume of hydrogen are very close to the ideal gas values of 22,41 L/mol and 24,0 L/mol at 0 °C and 20 °C, respectively, thus confirming that hydrogen gas behaves almost ideally.

As always it needed some shopping to be done first to get our Hydrogen production back on rails. We started with getting 0.5 kg of Aluminium powder from Barnes.

It looks so tiny when having it in hand.

Getting Caustic Soda from Santo was much more entertaining as they keep selling it in 25kg bags only.

Of course, handling such material might be mildly problematic, we’ve got proper protection ready.

Next phase started by putting together the “reaction chamber” by scavenging on our previous hydrogen generator. Mainly our original investment into the Teflon coating paid off thousand times as the main basin needed to be corrosion resistant to withstand that caustic soda solution, while also having high thermal conductivity to disperse heat from planned (exothermic) reaction.

As a lid we’ve used an old perspex sheet and drilled couple holes to get solution feed in and hydrogen outlet. Whole contraption got placed in an esky filled with water to cool things down and also to capture any potential leaks.

Moments later we’ve started generating our first Hydrogen!

And few moments later, with assistance from Ondra, we had our blimpy back again.

At that stage we had to stop our test as it was getting late and we had some other activities.

While working in parallel on multiple projects here, an important one seemed to became quite laid back lately – our airship’s envelope. However that’s not that true. I’ve been checking all the corners to get an material which should do the job – 100 micron PU sheets – but with no luck so far.

At some stage I’ve got in touch with Mr. Martin Hill, who suggested to contact a German company called Windreiter and check what they are doing. Then it was easy and I’ve got in touch with Dr. Andreas Burkart – Windreiter co-founder and we briefly discussed our project.

To my minor setback Dr. Burkart suggested not to start building anything too complex before taking baby steps and pointer to their e-shop with few of-the-shelve envelopes there. Being busy with work I couldn’t make myself to decide where next with this topic till the “Father’s Day” event came with Sebi asking what do I want. While my first idea went to the SignMyRocket, then I reverted to a more plausible solution and asked him to pick one of the Windreiter envelopes for us instead.

Sebi picked the Silver Blimp 181-200 for 40,00 EUR.

It came from Europe in about two weeks in a well padded envelope.