How many litres of air do I need for a raft in a Daft Raft Race?

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In summary, a raft for a "Daft Raft Race" will need at least 601 liters of air to support 600 kilograms. This is based on Archimedes' principle, which states that the weight of water a barrel can hold is the weight it can support. However, it is recommended to have a larger volume of containers to ensure that the flotation device does not sink. Additionally, one should be cautious of converting between liters, gallons, and kilograms to avoid miscalculations.
  • #1
rob.oc95
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raft for a "Daft Raft Race"

Hi all,
Now I know this has probably been asked already, and it's probably a very simple question, but I'm building a raft for a "Daft Raft Race" and I was just wondering how many litres of air in cylindrical, metal barrels would i need to support around 600 kgs?
Thanks a mil.

Rob

P.S. Even just let me know how it's calculated/a formula and I would be able to work it out myself.
 
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  • #2


rob.oc95 said:
Hi all,
Now I know this has probably been asked already, and it's probably a very simple question, but I'm building a raft for a "Daft Raft Race" and I was just wondering how many litres of air in cylindrical, metal barrels would i need to support around 600 kgs?
Thanks a mil.

Rob

P.S. Even just let me know how it's calculated/a formula and I would be able to work it out myself.

Welcome to the PF.

In general, whatever weight of water the barrel would hold, is the weight that the empty barrel will support:

http://en.wikipedia.org/wiki/Archimedes'_principle#Archimedes.27_principle

.
 
  • #3


Not to say you're wrong or anything but this doesn't seem correct.

To support 600 kgs or so I would only need 3, 50 gallon containers (plus a little extra) ?
This just seems a lot less than what i was expecting.

Thanks for the quick reply anyways...
 
  • #4


One liter of water has a mass of one kilogram, so you need at least 601 liters of air to float your 600 kilograms. (600 liters of air has a mass of 0.7 kilogram!)
 
  • #5


rob.oc95 said:
Not to say you're wrong or anything but this doesn't seem correct.

To support 600 kgs or so I would only need 3, 50 gallon containers (plus a little extra) ?
This just seems a lot less than what i was expecting.

Thanks for the quick reply anyways...

Check out the wikipedia article that I linked to. It should help out.
 
  • #6


To support 600 kgs or so I would only need 3, 50 gallon containers (plus a little extra) ?
]

a gallon of water weighs about 8.3 lb, and there are 2.2KG per lb, so a gal is about 3.8kg
and 150 of them would weigh about 150 x 3.8 or 570 kg. so you really need closer to 600/3.8kg or 158 gallons of container to support 600 kg...
 
  • #7


While what has been said in this thread is true, you are likely going to want a much larger volume than what you are calculating, otherwise your flotation device will be 99% under the surface.
 
  • #8


berkeman said:
Check out the wikipedia article that I linked to. It should help out.

Ok. I think I see it now. Very Sorry. Thanks everyone else too. Great help. Couldn't find out any other answers on the internet...
 
  • #9


Naty1 said:
a gallon of water weighs about 8.3 lb, and there are 2.2KG per lb, so a gal is about 3.8kg

That's the exact thinking that caused the 767 to run out of fuel over Canada!

It's 2.2lb per KG.A litre of water = 1kg.

There are approximately 4.54l in a UK Gallon.

That gives 4.54kg per gallon.

That means each 50 gallon container holds 227kg of water.

So for your boat you would need 3 of them to give you 681kg of buoyancy.
 
  • #10


jarednjames said:
That's the exact thinking that caused the 767 to run out of fuel over Canada!

It's 2.2lb per KG.

:smile: Good catch!
 

Related to How many litres of air do I need for a raft in a Daft Raft Race?

1. What materials are needed to build a raft for a Daft Raft Race?

To build a raft for a Daft Raft Race, you will need materials such as wood, plastic barrels, ropes, and waterproof glue. These materials are essential for constructing a sturdy and stable raft that can withstand the challenges of the race.

2. How can I make my raft more aerodynamic for the race?

To make your raft more aerodynamic, you can add a pointed front and tapered sides to reduce drag. You can also attach a sail or use paddles to help your raft move more efficiently through the water.

3. Can I use any type of wood for my raft?

It is recommended to use lightweight and buoyant wood such as balsa or plywood for your raft. Avoid using heavy or water-logged wood as it can weigh down your raft and make it difficult to maneuver during the race.

4. How do I ensure the safety of my raft during the race?

To ensure the safety of your raft, make sure all the materials are securely fastened and the raft is well balanced. It is also important to wear life jackets and have a designated safety boat nearby during the race.

5. How can I make my raft stand out in the race?

You can make your raft stand out by adding unique decorations or themes, such as a pirate ship or a tropical island. Just make sure that the decorations do not interfere with the stability or aerodynamics of your raft.

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