Hi,
Anyone can shed a little light? Additional boot project (trailer)
How many liters of air in a normal, say 10M, leading edge and struts.. as in what would be the size required for an air tank at 100psi to fill 2 medium sized kites.. before the motor needs to kick in and refil the tank?
This is an ongoing project and now I am looking at the last parts of it - onboard compressed air and board racks 
I have a compressor that will fill a tank at 50 ltrs /min up to 100 PSI and this can be going on my way to the beach 
, now I need to know what size tank I require, research where to get it from, aluminum / steel / carbon, etc.
Any Eng's want to put 2 cents in? 
Ahh and for the comments "pump it by hand, HTFU" etc.. I am thinking of the whole crew I kite with...
Cheers,
V
Option 1 -Very rough estimate:
Measure how much goes in by pumping it up.
Vp=Swept volume of your pump = 1/4(pi*diameter^2)*stroke
Assume all swept volume (Vp) from the pump goes into the kite. (Note it will probably be less than this in reality due to compressibility of air)
Multiply Vp by the number of up and down strokes of a two-way pump to inflate to required pressure.
This will give you the absolute maximum amount of air you need to inflate your kite. In reality, it may be up to 50% less than this due to compressibility.
Option 2 - More accurate:
Fill a bladder with water. Measure how much comes out (V1). Calculate volume at pressure using formula: V2=V1*P2/101.3. (Note: P2 is the absolute pressure=101.3+gauge reading in kPa. Thus 6psi on gauge = 142.7kPa absolute)
, now I need to know what size tank I require, research where to get it from, aluminum / steel / carbon, etc. 
Hey V i have and still use an old air conditioner pump on the 4x4 . Tank is 30 lts (piece of pipe 200mm diameter with caps weilded in 900 mm long ) and the pump kicks in at around when the kite is 12 full but i use this pump also to pump up my tyres after i get back on the bituem (black stuff ) the hardest problem you will have with all this set up is the onoff pressure switches are for work shop air compressers - on - 80 psi . off - 110 psi so to compare my set up is hard at full tank of 30lts pump starts up at 80psi so i recond if you had a tank of 50 lts pumped up to 110 psi you would get pretty close to filling one kite . My kite is a 11meter . I have used this same combination on a old lpg bottel you need at least 1 hp to drive pump to 110psi . It works out to be around 11cfm . if you only need say 20 psi the motor could be an old starter motor direct drive to pump . Hope this all helps or i have just filled ya head up with useless crap .
What type of AC pump is it and what mods have you done to it to get the oil around it. AC pumps are prone to spitting out chunks of metal if not lubricated, with gas in it the gas drags the oil around the system you dont have gas in it now?. Ac compressors can also reach over 300psi so i would make sure your receiver tank can handle that pressure or you are just relying on a cheap electric switch for protection. Alternately you can put a pressure release on the tank.
hey waxman dont use the rotory use the piston type like xe -xf ford has its own sump valves do require some lube a hit of crc of small amount say every 40 hrs and shes all good i have had this set up for 12 odd years with no probs . Your are right safety dose come first sorry i do have a releve valve on it as of the same you find on a handy man or any industrial compressor around the $17 it cost me (pops off air at 120 psi) . It has the same electrical switch as a normal compresor i wired it up with a master switch so as pressure gose down it makes contacts in it close and the eletric clutch on the ac pump engages and it starts pumping too simple really it is dead simple . has to be treated like a normal compressor dont forget a drain in bottom of tank aswell to drain water out also make the out let at top of tank so any crap ,water or what ever stays in tank not in kite .
Awesome feedback guys, head full of ideas.. still deciding how to go but now I have more info. tks.
Anyone knows how many liters to a kite, average 10-12 mtr? opinions vary between 80-200 ltrs..
Tks ,
V
my 14m took 142 1 litre return stroke for the leading edge, thats 284l.......
i reakon the pump was ****ed. but i never hurt my back.
Compressed Air Explained
What happens when we compress air?
Compressed Air is clean, safe, simple and efficient. There are no dangerous exhaust fumes of or other harmful by products when compressed air is used as a utility. It is a non-combustible, non-polluting utility.
When air at atmospheric pressure is mechanically compressed by a compressor, the transformation of air at 1 bar (atmospheric pressure) into air at higher pressure (up to 414 bar) is determined by the laws of thermodynamics. They state that an increase in pressure equals a rise in heat and compressing air creates a proportional increase in heat. Boyle's law explains that if a volume of a gas (air) halves during compression, then the pressure is doubled. Charles' law states that the volume of a gas changes in direct proportion to the temperature. These laws explain that pressure, volume and temperature are proportional, change one variable and one or two of the others will also change, according to this equation:
(P1 V1)/ T1 = (P2 V2)/T2
Where P=Pressure V=Volume and T=Temperature of the gas, 1 being an initial state before a change, 2 being final state after a change.
When applying this to a compressor, air volume (or flow) and air pressure can be controlled and increased to a level that suits the way it is being used. Compressed air is normally used in pressure ranges from 1 to 414 bar (14 to 6004 PSI) at various flow rates from as little as 0.1m3 (3.5 CFM - cubic feet per minute) and up.
So if we assume the air temp is the same between the kite and the tank, P1 = 10psi, take v1 as 200litres = 2000/100psi = 20 litres. But that would have to be at a constant pressure so as your pressure drops so does the volume of air. So without working it out to much you would have to assume that a 40litre tank would be a safe bet to pump up one kite.
If you look at a higher pressure tank like a dive tank, i not sure exactly what pressure they hold but think its around 3000psi the tank would be a lot smaller
200x10=2000/3000=0.67litres.
So a good sized dive tank would be able to pump up a lot of kites. cost about $10-15 to get filled for a big tank.
Waxman (and everyone else) - tks for this. I am looking at a 40L tank and my compressor will fill it at 100 PSI approx so it seems I'm around the ballpark.
Now lets see if I can find a Carbon Fibre tank rather than a steel or aluminum , valves and cut-off switches, gages - long list .. eheh
I appreciate everyone's contribution. Awesome, guys.. will post pics when done.
V
I'm sorry but this is retarded. A pump is $20 from the camping store. My estimate is you'll spend $1000 on this nonsense you speak of. So let's assume instead that you bought 50 pumps which break every 6 months. That is 25 years worth of pumps.
This reminds me of the spacepen the Americans developed, millions of dollars research and development to produce a pen that can write in zero gravity and upside-down. The Russians? They use a pencil
Why don´t you just buy a Bravo electric kite pump which is made for pumping kites, it has a auto shut off valve which can be set at different levels as struts have different pressure to leading edges, you can usually pump up 4 to 5 kites with it before it needs recharging which can be done at home or with a car lighter. The problems with this pump is you have to be very careful with it not to get sand in it, although if you do you can clean it out but this has to be done at home and takes about an hour as you need to pull the whole thing apart, the other problem is the price, they are expensive but I have had one for six years and it is still going good!
A better route to go might be a really large inflation bag. This is the small one, but I've heard of guys using larger ones to inflate large inflatable boats in a matter of minutes.
Sir V,
If you are looking for the "build challenge" and/or "multiple use" rather than the commercial units perhaps you could:
Match the required current draw from whatever 240 volt device you choose and get a 12v to 240 volt inverter for your vehicle (can be put to other electrical uses as well).
Then you could use:
A chopped down / modified, free (old barrel style) vacuum cleaner which give a high volume output.....( I have used a similar unit to inflate a small dingy).
Or Salvage an air pump ( hi vol) from a disused spa unit.
I'm not sure but you may be able to use a hi flow unit from a low pressure spray gun setup.
Keep mindful that the commercial units are much more portable, a plus & minus, as they are more portable to the pond scum that steal as well.
regards
Fossil
I am really very pleased with (almost) all the feedback on this topic. It is awesome to see that we are all here for each other. to clarify. This is not about being lazy or the money spent, it is about problem solving and innovation. I neither have loads of cash, since I work like everyone else, nor I want to re-invent the wheel. But I love a new project so that is the main purpose of the enterprise.
The proposition comes from 'What if...', then the ball starts rolling. If you understand that, you'll be laughing with me.
Cheers guys, keep contributing as I am sure others like me enjoy constructive input.
V 
