Re-Think

As I said before, Lifelife currently makes no sense as a product.
The main problem just now is that sending all of your assets away on a string is a bit pointless.

It all needs to be considered from the usefulness to the person in the water. For example, the PLB will need a separate battery as before in order to stay functional even if the other battery is flat.

If the light is staying with the user but the line is still travelling then we need another separate battery from the LED lighting.

So in all we have 3 electrical  systems in one product. This should not be a problem, they should even be able to charge and be switched on my the same systems. The added complexity is worth the value added to the product. The system will look something like this on a high level visualisation:

My next big issue is that I don;t know who to rectify the line visibility problem. None of the solutions such as dyes and luminous coatings can't last long enough to be worthwhile and you are unlikely to see them in the day still anyway. It needs to be passive but non bulky....

Pre Submission Presentation

I've come to the conclusion whilst doing these sheets that this product needs a major re-think. I'm not sure what that will entail yet but it's mainly focussing on the internals and the fact that at present the thing flies away with all of your signalling capability. Not a good move. I'm also still not sold on the luminous line but haven't found an alternative yet.

Presentation pages ready for pre sub pres' tomorrow. I got some good renders and photoshop in context shots so I think this should be quite good. My main concern is that aside from the first page and technical features they are quite wordy sheets. 

Pointless Features

I'm beginning to notice some fatal flaws in the Lifeline, mainly to do with the glowing line concept.

Imagine you're flying over the sea at night, searching in vain for a head bobbing between the waves. Suddenly a glow appears on the horizon, as you get closer your realise that a spirla of light is leading you right to the MOB. He has been rescued at least half an hour before the search pattern was set to get there, half an hour that would have been 20 minutes too long.

Now picture that same scene but during the day. Hanging out oft he helicopter in vain, following the search pattern. Half an hour later you fly over the spot where he was and continue along the planned route with a heavy heart.

Unless it is night-time this product is essentially useless. How can I get round this and solve the problem?

On the bright side I'm putting some usb ports in the charging hub that will ensure an opportunity for the crew to charge any devices they have on board from a single outlet, freeing up limited resources within the boat.

3d graphene has also just been invented in the lab(http://www.nims.go.jp/mana/research/highlight/vol9.html). Tensile strength exceeding 1TPa - that would be an interesting material to use! Unfortunately it cannot currently be mass produced.

Material Decisions

I am using Cambridge Engineering Selector to help me specify materials for this project. With the user, environmental and manufacturing requirements in mind it is very simple to narrow down material choices.

I have decided to use poly-amide for the casings of Lifeline as it has mechanical properties favourable to the maritime environment. Most noticeable is the high resistance to environmental stress cracking, impact properties at low temperatures, price, and translucency.

It is also well suited to mass production processes such as injection moulding - essential for this product.

Another material that I have come across is graphene, also known as super capacitors. They are able to charge in seconds and discharging over much longer times. This could be an answer to the energy storage problems and would also reduce the chore of charging - improving uptake or at least encouraging regular use.

Project Icehands

Live fire testing of the grip models was performed earlier. OUCH!

 I filled a basin with cold tap water and then chucked a bag of ice in and left it to cool down for five minutes.
Experimental procedure was to hol my hand underwater for as long as I could take then try the different grips with a quick 30 second dunk to cool my hand back down after being out of the water.

I can honestly say I was not expecting it to hurt as much as it did. I lasted about 3 minutes before I was jumping up and down trying to keep going.

Round Grip: 40mm

 Hexagonal Grip: 25mm

 Hexagonal Grip: 38mm (WINNER)

 Pentagonal Grip: 38mm

Hexagonal Grip: 47mm

It was shocking how quickly my grip strength faded, I could not put any pressure on these grips at all (you can see it in the pictures). Having said that, there was definitely a sweet spot for a good sized grip.

The round grip was ideal for sitting in your hand but felt really insecure as it spun round farily easily. However, the hexagonal grip of a similar size retained the ideal holding dimensions whilst the corners provided a secure feeling.

The 40mm round grip and 38mm hexagonal grip were the best received through my previous survey which cemented the decision to go with the hexagonal form factor.

Aftermath: Tutorial 3

Unfortunately our tutor wasn't able to make this group session, surprisingly it turned out to be very productive anyway!

No one seemed too keen on the ice water testing route but did appreciate the idea. I think I'm going to be putting this off for a bit, might take the plunge tonight...

Issues highlighted by this tutorial were to do with material selection and tech integration.
Materials wise I haven't given this proper thought yet. I want to use an engineering plastic such as polycarb or polyamide but I haven't had a look at CES yet to decide properly.

The integration of coastguard contacting when the device is trigger is trivial. Personal locator beacons currently exist that transmit a distress signal to a satellite and this is monitored worldwide. They are relatively inexpensive and will integrate nicely with Lifeline.

Sketch Modelling

got some foam modelling in the workshop done today. I wanted to test out the different possible shapes for the handle of Lifeline. 

Based on the optimum power grip diameter of 1''-2'' I cut out 3 different sizes of foam hexagon which I will be testing using ice and cold water later on alongside a handy baseball bat as a round grip and also some steel tubing taped together as an ovalised tube.

I will also be handing these out to people with varying sized hands over the next few days and asking them to pick the one that feels best. The idea is that if their responses converge on a similar size and I agree with that after freezing my hand and trying them again then I will have found something close to good for the average person. 

I won't be asking anyone to participate with the ice water experiment because I'm pretty confident it'll hurt.

How Are Searches Conducted?

There are whole textbooks written on the science of searching for people, many feature lengthy calculations and derivations but it is true that the most commonly used search patterns used at sea are these three:

These three search patterns are extremely effective when carried out by a party such as the coast guard or the navy, in other words people who have training . We get into problems when boats and crews who are inexperienced or out of practice try to search. Inevitably their patterns will start to drift or their track distance is too large and so on. For this reason the coast guard will generally refuse all offers to help with a search until the situation becomes desperate. The lifeline is clearly going to have to cater to both professional searches as well as those conducted by untrained amateurs. The difference between the two has cost lives in the past. 

My next research session is going to have to begin looking into visibility at sea - how far can you see from a boat? What can the human eye discern at distance? But first, I'm going to go do some sketch modelling.

Simulation Dead end

Modelling for both people in the water and the power requirements of the lifeline ahve hit a dead end.

Firstly, there are so many variables in the first case that it doesn't help much more to have various parameters that are editable because it is never going to be accurate. I am going to use the chart I posted previously as a guide to aim for:

I've decided that my best option is to ensure that Lifeline is operable within a couple of minutes and that it's ergonomics and geometry are well suited to the conditions and the physiological effects they cause.

The other model, of Lifeline's electrical power requirements has also died a death. I have calculated the power requirements for a certain speed, but I do not know enough about prop geometry (I also haven't been unable to find clear information online) to be able to then translate this into a motor speed and hence current drawn which would allow me to spec a battery.

I've sunk a fair bit of time into it so I'm going to call it quits there and spec the motor and battery by comparing with RC models that deal with comparable loads.


A more successful foray into excel allowed me to calculate the space required for a set amount of line. It turns out spirals take a huge length to create relatively small diameters. I used an online tool (http://deepfriedneon.com/tesla_f_calcspiral.html) to calculate the length of line for a given diameter and then used excel to calculate what volume I would need to fit this in.

Aftermath: Tutorial 2

On Friday we had a group tutorial with Craig Lynn, he was really helpful for everyone and I came away with a huge list of things to get working on!

A lot of what came up in the tutorial I had already been working on but there were definitely some interesting ideas brought up.

The thought of using a propulsion system that was not electrically based had not occurred to me so I'm going to do a bit of digging. Compressed air looks like it might work although I'm not convinced that the numbers work so far.