flying uav update - not good

demonicpicaxeguy

Senior Member
very usefull to know my next question is how much can i trust good earth?

i've done a little scavenging around here so far i've found
1X 200watt electric brushless motor with 4kg/cm worth of torque
2X 18ahsealed lead acid batteries
5X spools of automotive wire 10m on each spool
2X nokia phones (batteries completely dead) (looking for the chargers)
1/2 a can of expanda foam (i think i'll need another one or two)

as for the hull i've picked out a design which has a weighted stabilising fin underneath it is 1.5m long 30cm wide and 30 cm high in the body it's going to be constructed out of fibreglass which i'll pick up next week after payday

all i'm short on now is a Picaxe pilot a secondhand Gps unit and the various other picaxe based modules that will control and monitor the whole thing

i might go and get one or two of thos big aluminium sealed boxes and stick everything in that when it all works

total cost so far $0 ( only because i have everything already so far ) :)
 

andrew_qld

Senior Member
good earth?

If you are sealing the electronics (ie the GPS, pixexe etc- not the batteries & motor) you may want to put some sillica gell or some sort of decassant in it to absorb any moisture which may condense out of the air. Maybe mount the boards "mid air" in the box so no matter which way up it is the processor isn't sitting in water if it does get water in it.

There have been a few articles on interfacing mobile phones to processors around by serial. Worst case is you use DTMF tones or something through the microphone wires.

I read a few articles on phones in balloons and gliders with GPS. Ill see if I can find them.

Well the price is right so far!

Cheers,
Andrew
 

demonicpicaxeguy

Senior Member
i meant 'google earth"

the aluminium boxes which i'll seal with a HDPE glue and the suck all the air out with a vacume pump courtesy of one of my neighbors first things first thouh i need to find myself a cheap gps unit
 

hippy

Technical Support
Staff member
I've watched a few of the DARPA Autonomous Vehicle Challenges on TV and I can never resist the thought, "Sheesh; that's easy. Why can't these guys get it right" ?"

Given that they are usually entered by some of the brightest groups of people around with full technical support and considerable funding I think it shows that there's a big difference between the simplicity of how to and the practicalities of doing.

I think there's a lot of merit in throwing something together at minimal cost to see what you can do with it and identifying what in hindsight is obvious but got overlooked. I'd be surprised if SS PICAXE looked anything like the first prototype but you could get lucky.

The hardest part is debugging for situations which are not easy to test ( GPS inversions as you cross the equator or meridian ). The lessons of Beagle 2 are worth learning. If you don't test or go ahead after a failed test hoping it works when needed you can be sorely disappointed, even though everyone else saw that disater looming from 36 million miles away.

I wouldn't worry too much about SatCom for now. Once you have something which looks like it's capable of doing what's required you should be able to attract sponsors who can provide the clever stuff.

The biggest obstacle to success ? Al-Qaeda could take your idea, bolt a nuke to it and sail it straight into New York Harbour. Just like the DIY Cruise Missile, intellectual pursuit can be crushed when up against knee-jerk paranoia. And we were told the Dark Ages were over :)

Despite my scepticism of really great success any time soon, I really do hope you prove me wrong. Bon voyage !
 

Dippy

Moderator
2 questions;

1. Why Google Earth? Why not proper marine charts?
2. Why vacuum? You'll have cable glands to/from your al boxes won't you? You'll never retain a vacuum or even a vacume. I'd stick with Andrew's dessicant and also spray pcbs with a conformal coating.

I hope it works too, but ... the sea is a rough place.
 

hippy

Technical Support
Staff member
i need to find myself a cheap gps unit
Get yourself a web site. Find yourself a Mission Statement. Knock out some hyping-up copy and write to people on your official letter-headed paper who may be able to give you what you want.

The more interest you can generate the more likely it is you find someone will have what you need which they may not want. Once you reach a critical milestone - your boat/ship/sub sailing in a neat path hugging the contours of a local swimming pool or lake - you can attract TV crews for the local story. Publicity and interest breeds more publicity and interest; take note of how Richard Branson works.

With Climate Change ( we'll all be living on water soon ) plus Recycling / Re-Use very much on the agenda you can play those to your advantage. Be modest in what you ask for to start with and once you've got some donors on board that can be used as persuasion of bigger fish to hand over a little more.
 

demonicpicaxeguy

Senior Member
goole earth - easy ,cheap, i already have it and it shows everything on it

reason for vacume is that while everything inside is going to be embedded in a casting resin type material the gps unit won't be so what i'm thinking is if i seal up the box it's in and suck the air out there won't be any oxygen for anything to corrode
as for the wiring going in and out of the box a liberal amount of construction adhesive around the holes and wiring does tend to provide a pretty good seal for a vacume
 

Wrenow

Senior Member
Again, DPG, I do recommend getting in touch with the Australian Battle Group guys http://www.ausbg.org. 1-2 meter long vessels are their bread and butter, and they re celebrating their 10th anniversary as a national organization next year. They have also sponsored the last 6 Big Gun Model Warship World Championships.

Remember, these are not casual toys. They can cost from USD$1,000 to $2,000, and take upwards of a year or more to build. They not only have to maneuver, but have traversing and depressing gun systems, pneumatic firing systems, etc. They are very familiar with the waterproofing of electronics, what size motor drives what hullform what speed. Sources for parts. How to build stuffing boxes for the prop shaft and rudder shaft. Remember, they build these for actual combat, and intentionally sink each other. Some have also been designing control electronics. They would definitely be the pool of neurons I would try to tap into. Remember, these are basically battlebots on the water with a WWII theme.

One thing I would suggest - aluminium might not be the best choice for a WTB (water-tight box). You might be better off with an Otterbox or other polycarbonate waterproof diver box. You can drill cable connections and put solid metal headers through, and epoxy them in place to provide passthroughs. Wires will wick water in, solid metal will not. Gold plated headers are a really good idea.

And, 3m Skotchkote is your friend in a marine environment. Lastly, you might want to look into a 2 part flexible urethane foam, like Smooth-on Flexfoam instead of a rigid spray foam. And some of the AUSBG guys may have some tips on using foam as well (some of us use it in the water channeling, and there are some gotchas to beware of).

By the way, we just put our knowledgebase up on the http://www.ntxbg.org web site. There may be a couple of articles of interest there.

Cheers,

Wreno
 

Coyoteboy

Senior Member
Having read about competent university engineering teams destroying 20Ks worth of ROV and have to return 4000 miles from the test site. due to badly specified connectors and poor waterproofing, id suggest this is a tough task even with adequate funding and design knowledge. I know one thing that is used for waterproofing and oxidation control (vacuum wont work a jot, for a start you wont be able to maintain it and for a second start (lol) all that will do is encourage a leak INTO the elecs, you'd be better with positive pressure if you were taking that route) - they usually submerse the electronics in oil as it is non-conducting and obviously water-repellant. Its also easier to seal than a vacuum. HTH.
 

Brietech

Senior Member
I'd second coyoteboy on the oil thing, as I believe that is a fairly common technique. There is probably a fair amount of info out there regarding the autonomous submarines that university students build for competitions. I also think a cell phone with a global roaming option would be a good idea, as there is such a HUGE leap in cost between cell phones and satellite phones.
 

Wrenow

Senior Member
Filling the WTB with oil is fine, IF you use an oil with the right deielectric properties, and that does not degrade the servo pots or servo motor brushes. Corrosion-X or Aeroplate might work (we commonly use both), but I have noticed some issues with Aeroplate and a couple of servos (HS-55's in both cases - most, including other Hitec servos like it just fine). I still say you will want 3M Skotchkote. It is ugly as sin and smells worse, but is highly effective. Liquid Electric Tape is contraindicated, especially if you are using any oils.

As for position reports, check out findmespot at http://findmespot.com/ which gives satellite based position reports , and you can track on GoogleMaps - supposed to be USD$150 and USD$100 annual fee. It is also waterproof. Hmmm... a potential sponsor, along with the AUSBG?

Cheers,

Wreno
 

crumpybrown

New Member
Hmmm I'm missing something.... what data do you want to send to it? I had the impression that the trick was jsut to have SS Picaxe tell him where it was?
 

Brietech

Senior Member
you would ideally be able to send it new waypoints (you could [and likely should] just preload the course, but being able to change it after-the-fact would be a nice feature)
 

D n T

Senior Member
Radio telemetry provisions

DPG I have been following this thread, very cool, If you needed a sat phone and you told telstra about what you are doing they might come to the party, it would be awesome advertising for them.
Once again, very cool idea
 

demonicpicaxeguy

Senior Member
i've sent an email to the poeple at telstra about that , just waiting for a response

re- non conductive oil in the aluminium box, i had an inkling that would come up and i have a better solution

i'm going to embed the whole lot excluding the gps unit in casting resin

as for the gps unit and water proofing i've got a water proof chamber that it should fit nicely in

the hull design is getting interesting the battle ship idea doesn't look like a bad way to go but my auntie is sending me some of my grandfathers schematics and drawings for some of the hull designs my grandfather had some fun with when he was working as an engineer in the french navy and see if there is anything good in there
 

Dippy

Moderator
Cor that looks pre-WW2.

I must admit I thought it was going to be a picture of the Titanic with a windmill on top.
 

Wrenow

Senior Member
DPG, If you want to look over French hull designs, you might want the original hull plans (these are, I believe, mostly 1/100 plans, but of course you scale them as you see fit) many are available at:
http://www.servicehistorique.sga.defense.gouv.fr/02fonds-collections/banquedocuments/planbato/planbato/listebato/listebato.php

Richelieu/Jean Bart would be my choices of French hulls, I think, for this project. My son battles th slightly smaller Dunkerque. Yamato/Musashi (Japanese) is roomier, though.

Easier, and probably cheaper, to pick up a ready-made fiberglass hull from Bowning Shipyards. Bowning tends to build the hulls with a higher freeboard, that a battler trims down to the proper deck level. You might want to leave the extra freeboard, and just put a caprail and deck on. For the deck, Sintra (foamcore PVC) might be a very good choice. Or, of course, fiberglass.

When you get to Bowning, you will find that many of these hulls have beautiful lines.

Do keep in mind that these hulls are designed to have penetration windows cut and then sheathed with balsa, so do not expect fancy polished gelcoat. Do expect a strong and sturdy hull (the areas not cut out, 3/8" "ribs", have to withstand the abuse of being repeatedly shot at and the balsa being stripped and reapplied every so often). If you want a polished look, then sanding, polishing, and waxing are in order. Or gelcoat yourself. You will understand what I am talking about when you see the raw hulls and a finished ship.

Cheers,

Wreno
 

hippy

Technical Support
Staff member
re- non conductive oil in the aluminium box, i had an inkling that would come up and i have a better solution. i'm going to embed the whole lot excluding the gps unit in casting resin
Don't forget that this could a one-way process so would not be appropriate until you push SS PICAXE off into the sunset. Are you thinking of potting everything or taking the box of electronics and just potting the box itself ? At least with the later you can saw it open and start again.

I don't know much about resins but it's probably worthwhile investigating further before doing it. Any shrinkage or deterioration could open gaps around cables/sheaths which will allow water seepage. There's probably some issue with heat dissipation as well.

Heat and cold generally - that's something not so far discussed.

No matter how well protected parts are, there will always be a weakest point. If the GPS unit / aerial isn't protected well, that could be the first to go and it would be shame to have a perfectly serviceable and survivable system simply not know where it is.
 

boriz

Senior Member
Encasing the electronics in resin is fine. But what about the rest? The motor, the wind turbine, the steering gear etc.

This vessel has to be able to survive in extreme conditions of temperature, sea and wind. It will need to be self-righting should it become inverted, and withstand battering from all sides, not just by sea, but by flotsam, other vessels and rocks. What if a lump of floating debris were to be tossed upon it by a big wave?
 

Brietech

Senior Member
Boriz - That's what my primary concern would be at the moment. I'm confident I could build a self-righting ship that could take waves, but I'm not sure I know of any plastic hull that could take half a tree being thrown on it from 2 meters up!
 

Coyoteboy

Senior Member
There are some things you cant really prepare for - that ship landing on it is one. Theres no way you could have a wind turbine that remains active in rough seas - it would form a sail and be ripped off in high winds, clog with weeds/rope/anything.
 

Coyoteboy

Senior Member
IMO and IME resin is a substandard solution when compared to oil. For a start you can make repairs or tweaks if you use oil.
 

Dippy

Moderator
Well, shall we worry about that later?
There's a lot of work to do first before we reach for the GTX.
 

Coyoteboy

Senior Member
Not really sure "worry about it later" is the best route, in fact its one thats fairly commonly associated with project failures! Plan it, do it right, do it once.
 

Dippy

Moderator
The electronics/mechanicals/build need planning for sure.
But I don't think it requires too many planning meetings to decided whether to fill a box with oil or Epoxy, or does it?
 

BeanieBots

Moderator
Well I'd go for good old fashioned electronic potting compound.
LONG before that though, I'd be testing the electronics, with potting just a back thought.
Probably fit to a simple buggy and test in a large car park first. So much easier than a boat to start with. Recovery is not an issue. Accidents less likely to cause damage. Corrections easier to implement. Then worry about how to water seal in a boat.
It ain't going nowhere without a control system that works, no matter what the platform or how well sealed.
 

manuka

Senior Member
Kiwi contribution:

Quite some years back CIT (Central Institute of Technology-a NZ tech institute) came up with much the same idea as DPG,with a Trans-Tasman trip (~2000km) in mind. Considerable $$$$$ was thrown at it (in todays terms about a years Western income), but trials,local politics,red tape & funding sunk the planned NZ-Aus sea voyage. I recall it managed about 10km off shore before the sea battered something into submission & students graduated. There was even some talk of rascals intercepting it...

Quite by chance I ran across the stored canoe sized hull recently, & can take a few pix & measurements if you like. It certainly caught the imagination at the time (~late 90s?), with significant NZ press/TV coverage. Here's a 1999 mention =>http://www.rsnz.org/news/index.php?view=searchdate&year=1999&month=02&day=13

DPG: Given the Aussie sunshine & empty outback (+ windless conditions), maybe consider a solar powered plane as more feasible - & CHEAPER! How about joining the Darwin-Adelaide "Solar Challenge" next month?

Stan
 

Coyoteboy

Senior Member
The reason I was suggesting planning your waterproofing first is simply that that determines the kind of containers needed for the elecs, therefore it also determines the material, shape and size of them, and therefore the weight and cabling, therefore the hull capabilities and motor/chargine requirements. It needs to be looked at early on, it doesnt take many design meetings to choose, just requires choosing. A few simple tests could give a good idea of the practicality of each.
 

Wrenow

Senior Member
Boriz - That's what my primary concern would be at the moment. I'm confident I could build a self-righting ship that could take waves, but I'm not sure I know of any plastic hull that could take half a tree being thrown on it from 2 meters up!
You obviously have not seen the tough fiberglass hulls of the AUSBG (the Australian Battle Group). My little 22" freighter had a little warpage (bowed in) in the sides due to normal shrinkage in the molding. It took a lot of oomph with a 1/4" plywood subdeck to ease it back out. Trust me when I say I am larger than the average bear, and it took a lot of oomph.

It has taken a lot (probably in the several hundreds if not low thousands) of shots from 1/4" steel balls traveling about 200fps (usually 3-8 hitting in unison). Not to mention accidental rams from 6' battleships weighing 50-100lbs.

Cheers,

Wreno
 

Coyoteboy

Senior Member
I think the best solution to the hull would be to make it a simple tube-based construction, theres no need for "ideal hull" designs etc - make it strong, make it reasonably streamlined but dont worry about manouvreability greatly. I think if I attempted it I'd be going with essentially a torpedo.
 

ljg

New Member
If you are looking for a tracking system that promises to be less costly than satellite phone or personal locator beacons, check out.

SPOT Satellite Personal Tracker

just coming on the market--- $149 + $99/yr I presume only one year would be needed.


will give GPS coordinates and can be tracked with Google Maps.
 

Wrenow

Senior Member
I think the best solution to the hull would be to make it a simple tube-based construction, theres no need for "ideal hull" designs etc - make it strong, make it reasonably streamlined but dont worry about manouvreability greatly. I think if I attempted it I'd be going with essentially a torpedo.

Hmmm. Problem with a tube/torpedo shape for a surface vessel, no "up" side - putting the GPS sometimes on the bottom, and making navigation more difficult. Also, tends to have more area exposed higher in the atmosphere to be affected by wind than a flat-top. Less buoyancy than a more squared-off hullform of the same width. A catamaran or trimaran of tubes, perhaps, with an inversion sensor in case it is flipped.

Simpler to simply weight one of the recommended model warship hulls for self-righting.

Also, a long, thin, tube, while it may be easier to push fast, is terrible on maneuverability. Do not be quite so quick to discount maneuverability. The better the maneuverability, the better you can deal with the ill effects of wind and current.

And, from a practical standpoint, it is easier to deal with and seal an access hatch in a "box" where you can remove one flat side (the deck of the warship hull) to reach everything inside than a cylinder.

I am not so sure I would discount the use of something that is, relatively speaking, cheap, sturdy, reliable, and for which the hydrodynamic design has been refined over, literally, hundreds of years.

Of course, if DPG wants to experiment with hydrodynamics as well as control systems, that is a whole 'nother kettle of fish. But the warship hulls give a pretty good test bed to start with to work out the control issues.

As well as giving at least a good starting point for the hydrodynamic issues/experimentation.

In fact, I have a USS South Dakota hull in my garage that I would press into service for this project if I were doing it (I think it is a better choice than my also available Bismarcck and Titanic).

Cheers,

Wreno
 

Brietech

Senior Member
Wreno - i was looking at the bowning website, and they do have some cool stuff. What are their typical price ranges? Any idea how much shipping to the US would be? Their website makes them seem kind of like a guy making boat hulls in his garage (which is probably true, actually).
 

Tom2000

Senior Member
I've been giving the hull quite a bit of thought.

The more I think about it, the more I'm convinced that any machinery such as a motor or wind turbine cannot last for any length of time in a salt/sea environment. So that pretty much leaves a solar-powered sail craft. But which one, and in what configuration?

I ran over the characteristics of some of the boats I've sailed. Sailing dinghys have a lot to be said for them. A bit large (5-5.5 meter or so), and probably too heavy to derive power from solar cells. But the hull design is right, and they are, for the most part, strong.

Which dinghy design?

Again, running through those I'm familiar with, I think one just above the sailing dinghy classification might serve well, with suitable modification.

The Rhodes 19 looks like a good jumping off point.

It's a very strong, efficient hull design, with a large fixed keel. I know that it's a decent heavy seas boat for its size, and from personal experience, I know it also performs well in light air. The large operating envelope points to an excellent hull design. But it's too large, and has a fairly complex sloop rig plan. It would take too much power and too much computing overhead to manage a sloop rig. Not to mention that one set of fabric sails probably wouldn't last a year at sea when flown 24/7.

So...

Scale the hull down to something 3 to 4 meters in length, leaning toward 4. Design the hull with absolutely no through-hull fittings... completely sealed... and as strong as possible. Scaling the hull size down will kill the hull's light air capability, but light air conditions aren't a major concern for blue water sailing. (You either have plenty of wind or you're becalmed.)

Seal the deck, and cover every possible square inch with solar cells.

Modify the design for a rigid airfoil sail that can be trimmed solely by rotating the mast. If possible, set the mast up for a 4-guy support system.

The airfoil shape should be conservatively designed, purposely keeping the aspect ratio well below optimum to minimize mast height. For this craft, duration and survivability are the key design criteria, not speed. It won't win any races - purposely. The airfoil should be designed for adequate power during heavy air conditions, and provide sensors and operating rules for feathering during storm-strength wind conditions.

The airfoil and keel design should be coordinated so the craft will be unconditionally self righting.

The through-deck fitting where the mast passes through gives me a real problem. The mast must pass through the deck right down to the keel for support, but the opening in the deck, no matter how I think about sealing it, is a source of water entry to the hull. I don't have a good solution for that problem, other than a bilge pump (which should be included in the design in any case.) I've considered mounting the mast and trim mechanism completely above deck. With a suitable guying system, possibly redundant, this is a possibility, and should be considered during strength analysis.

The rudder would be stern-mounted and overdesigned, both the rudder itself and its mounting arrangement. If possible, twin rudders might be considered for redundancy, but this arrangement would add problems of its own. It's something to keep on the back burner, though. In no case should a through-hull rudder be considered.

The rudder operating mechanism would be mounted completely above deck level, or built into a watertight box set into the deck. It would not be mounted below deck. The rudder operating mechanism should not be a source of leaks.

This is just an idea, and my "seat of the pants" feel based upon my sailing experience. The nautical engineer or naval architect, who is a necessary team member for this project to have any possibility of success, would be the one to consult on the design of the actual craft.

Good luck!

Tom
 
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BeanieBots

Moderator
Ok, so now we have a few hull design suggestions:)
How about the control system:confused:
GPS to know current location?
Waypoint sent by some method as yet undefined for destination.
So, which way do we need to go?
Hmm, need to know heading. Magnetic compass?
Directional light sensors (daytime only).
Track GPS changes?
Did the wind take it that way or was it pointing the wrong when the power was applied? Need to know wind speed & direction? Currents?
Maybe a video feedback for visual clues. How are you going to keep the lens clean? Salt water leaves a very opaque residue once evaporated. Lenses not very effective when wet.
If the vessel size is comparable to wave size, which way is up?

Assuming reliable sensor information. What about control method?
PID, Fuzzy, Vectored forces, combination of 2 or more? Maybe one I've not heard of.
Something everyone has overlooked. which PICAXE?

Object avoidance. It will be required at some point.
IR? US? They could be fun to design for sea going!

Some background reading to avoid repetition.
http://www.picaxeforum.co.uk/showthread.php?t=5814
 
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Tom2000

Senior Member
At this point, I'm concerned with the power budget.

How much deck area, implying "how much solar cell area?" How much will the three high current devices (mast trim, rudder actuators, bilge pump) require vs the solar cell capacity? Is there enough power available for running lights at night?

Then come sensors. Wind speed and direction, hull speed and slip angle, hull attitude and acceleration, sail instrumentation, rudder instrumentation, mostly. How can you get the wind speed and direction sensors to last for a year?

Next would be nav sensors. GPS, obviously. One or two? Compass or compasses. Do you need to physically measure hull speed, or is the GPS data enough? If you need to measure hull speed, how can you do so without a through-hull fitting?

Maybe with answers to some of these questions, (and probably a lot more I haven't thought of... such as "ET phone home"), it might be time to consider the software design and requirements.

Then, and only then, can you begin to answer the question of which processors, and what type. (My guess is that this might be beyond the capability of a single 08M. :) )

The point of my last two posts is that this is a project which requires serious, intensive design and a whole lot of expertise. It's not something that can be cobbled helter skelter in the basement.

Tom

PS - Not to mention the longevity problems with the rudder actuator and sail trim motor(s). Those won't have the same life problem that a propulsion motor would have, but they'd still be running a lot. That problem bothers me quite a bit.
 
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