planning10

Displacement....

Need to have a closer look at displacement.

Our Armless paddler.....Fred, has just made a nice new boat.

Hes very proud of it....

 

He thinks it is perfect.

When he sits in it, the bottom and a small part of the sides go into the water.

If he heels it, the shape makes the water push back, making it very stable.

He is happy.

Unfortunately, he has a cousin - who goes everywhere with him.

His cousin is called Duh. Hes also green as he is usually seasick.

Fred is still happy. The water is still part way up the first sides. The boat will still cause the water to push back when it leans.

Seems Duh has heard that when some people go camping, they whittle spoons.

Duh doesnt like wooden spoons. He likes metal spoons.

He wants to feel a part of it all.

So hes bought a big box full of tent, sleeping bags, food, cooker.



Ooops...Nearly forgot....

He also bought his hammers and his anvil.

Fred is pretty sure that he has a problem.

He thinks about it for a bit.

AHA!

Fred built a bigger boat.

Er.....

I think he misjudged Duh.

Seems Duh likes to hug his anvil while he vomits over the side....

Fred could save himself a whole lot of trouble by simply shooting Duh.

However, there might be some reason why he shouldnt.

If Fred works out exactly what the poor boat has to put up with, and designs accordingly, puking Duh and his anvil do not have to be a problem.

When it comes to displacement, you need to know how much cargo the canoe has to carry. You need a maximum weight, and a minimum weight.

Maximum cargo includes you, your clothes, your emergency kit, your camping kit, your food, your water, your maps, your kids, your partner, your dog, and even the anvil, if you intend to put it in the boat.

At maximum load, you must design your boat to still float properly for what you wish to do with it.

The boat must also still function when its unloaded and just you in it - if you intend to use it like that.

At maximum load, the sides must still slope out at the waterline.

At minimum load, the ends must be far enough down in the water to allow you to be able to paddle in a straight line - if thats what you need it to do.

The trick is to actually achieve this.

If you look at pretty much any of the plan sets available, they all have maximum and minimum load limits.

This is to make sure the finished boat will actually perform as required.

Sometimes you just cant get away with shooting Doh....



If my kid shoots me...

He will end up in bed with no tea and grounded lol.

Sometimes, its better just to build a bigger boat and then shove stabilisers on it.