planning09

Sides....

Pretty obvious that they are there to keep the water out.

They must also increase the width of the boat as it heels. This is done by making sure that the distance from the boast centre of gravity to the edge were the side comes up out of the water keeps getting bigger as the heeling angle is increased.

The top of the sides - on a canoe, must be low enough that the paddler, while sitting on the seat, or on the floor, does not bash his elbows.

Havent tried to paddle round something in a hurry with a thumped funny bone, and Im hoping to avoid it.

Sides.....

Freeboard.

Er....I thought this was something to do with cheap guesthouses, or staying at the parents place.

Turns out its the sides of the boat stuck out of the water when the water is flat and the boat is sat normally.

I also thought that if the waves were 5 foot tall, I would need 5 foot tall sides.

Turns out I was right.

Although only if the waves are the same sort of length as the boat.

 

Little boat in long tall waves, rides them without problems - despite being considerably shorter than the waves are high....



Now one half the height

As the wave length gets shorter, the boat struggles to change direction at the bottom and keep its bow out.

When the wave length is slightly shorter, no real problem...




...and shorter again....



The bow is getting lower in the turn now.

The corner is getting too sharp for the length and height of the nose of the boat...



...now its near its limit (please ignore the wave lenths)

Eventually, when the wave length gets too short, this happens....



..Thats not really where you want to end up.

Obviously, 10 foot tall waves...

Not in my harbour.

Max there is only 2 ft, so Im safe.

The shorter the distance the wind has to run over the water before it gets to your boat, the shorter the length of the waves are.

2 ft waves hitting a 2 ft boat arnt expected to be anything like as bad at the 10 ft waves earlier...



However, as the boat crests a little wave, the bow drops into the next trough with inertia and goes down deeper than it would if the wave dropped it slower...

The shorter the length of the wave, the faster it drops the boat....


This boat is getting close to its limit despite having plenty of boat out of the water when at rest.

These numbers are correct.

This boat is taking on water every wave, not because of the height of the wave, but due to the waves short length dropping the bow...

A boat thats going to be used exclusively on canals, where any traffic will be paddled, or out in ditches, minimum freeboard isnt a problem.

However, anywhere near motorboats, where wind gets 3 or four football pitches after running off a mountain, or off a sea....

You can need as much freeboard as at sea - or more.

Another stupid question....

Why havent Kayaks got 3 ft of freeboard?

Kayaks and some specialised canoes are designed to be constantly flooded. They have big air bags in the ends to stop water filling them up, and they just bob back to the surface like a held down football when its released.

Ok....Why dont I want 5 ft of freeboard on my 14 ft long canoe as Im going to use it in wind on the lake?

Windage.

The wind isnt very smart. It hasnt sussed that we only want it to blow us along in the direction we want to go, or to fill our sails with just the right amount to make us go at the speed we want.

The stupid stuff keeps blowing all over the place.

It hits the sides of boats, and especially canoes and blows them sideways, or turns the lightest end away from where its blowing from.

This can be nearly as much of a pain as the boat sinking.

Well.....Nearly.

Thats why canoes are usually around one to one and a half ft tall. 30cm - 45cm.

The bows, and often the sterns are higher to stop them sinking in short length waves - or chop (choppy waves).

The sides of the canoe are the pieces of canoe, from the bottom up to the top of the tumblehome.

On the ends, this is tipped forwards to make the boat climb over waves.

Canoes are traditionally very pointy, which encourages them to pierce through waves initially, before the wider area a foot back lifts the canoes bow up.

I believe this is why many canoes are traditionally built with very high noses.