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I used to sail and fairly quickly got the understanding for sailing up-wind. The thing that blew my mind, and continues to, is that the top speed you can reach

I used to sail and fairly quickly got the understanding for sailing up-wind. The thing that blew my mind, and continues to, is that the top speed you can reach is dependant upon the length of the boat and not the weight. This obviously excludes modern things like motorised craft, planing, foiling etc.

hutzlibu 4y ago
"The thing that blew my mind, and continues to, is that the top speed you can reach is dependant upon the length of the boat and not the weight" Is there a simple explanation for this to share?
- leetcrew 4y ago
  you might find this video helpful: https://www.youtube.com/watch?v=URgSFglbl5g https://www.youtube.com/watch?v=URgSFglbl5g
- gerdesj 4y ago
  Longer => greater surface area in contact with the water. Friction and stiction due to area is a greater killer of speed than weight, which will only put you a bit lower in the water. It is obviously a lot more complicated than that. Enough weight will sink you and more length will slow your descent to the depths a bit. Greater weight will increase inertia so acceleration will take a hit. Depending on how the weight is distributed you risk turn over due to your meta centre being in the wrong place in relation to your centre of gravity.
  - closewith 4y ago
    > Longer => greater surface area in contact with the water. >Friction and stiction due to area is a greater killer of speed than weight, which will only put you a bit lower in the water. The opposite is true. The longer a hull, the faster a displacement vessel can travel. Here's an MIT explanation: https://engineering.mit.edu/engage/ask-an-engineer/what-is-the-relationship-between-the-length-of-a-boat-and-its-maximum-speed/ https://engineering.mit.edu/engage/ask-an-engineer/what-is-t...
- mhandley 4y ago
  As a boat moves through the water it creates a bow wave. The wavelength (ie crest to crest) of the bow wave increases with boat speed. Once the wavelength of the bow wave equals the hull length, the boat will start climbing the front of the bow wave and will be sailing up hill. Unless you've got a lot of power and can climb on top of the bow wave and plane, this is the maximum hull speed.
  - sprkwd 4y ago
    Best explanation I have ever read for that.
User23 4y ago
> The thing that blew my mind, and continues to, is that the top speed you can reach is dependant upon the length of the boat and not the weight. This is true for any rigid body traveling through a fluid. It comes up in ballistics too.
sopooneo 4y ago
The most mind blowing down “wind” sailing I’ve ever seen: https://m.youtube.com/watch?time_continue=13&v=q2il8Fagbyk&feature=emb_logo https://m.youtube.com/watch?time_continue=13&v=q2il8Fagbyk&f...
Kon-Peki 4y ago
“Modern” things ;) It’s been 94 years since Uffa Fox built the (planing) Avenger and thoroughly destroyed his British competition on the Isle of Wight. And then took that little 14-footer across the channel to do the same to the French. All because the elitist snobs didn’t want him to join their club :)

hutzlibu 4y ago

"The thing that blew my mind, and continues to, is that the top speed you can reach is dependant upon the length of the boat and not the weight" Is there a simple explanation for this to share?

leetcrew 4y ago
you might find this video helpful: https://www.youtube.com/watch?v=URgSFglbl5g https://www.youtube.com/watch?v=URgSFglbl5g
gerdesj 4y ago
Longer => greater surface area in contact with the water. Friction and stiction due to area is a greater killer of speed than weight, which will only put you a bit lower in the water. It is obviously a lot more complicated than that. Enough weight will sink you and more length will slow your descent to the depths a bit. Greater weight will increase inertia so acceleration will take a hit. Depending on how the weight is distributed you risk turn over due to your meta centre being in the wrong place in relation to your centre of gravity.
- closewith 4y ago
  > Longer => greater surface area in contact with the water. >Friction and stiction due to area is a greater killer of speed than weight, which will only put you a bit lower in the water. The opposite is true. The longer a hull, the faster a displacement vessel can travel. Here's an MIT explanation: https://engineering.mit.edu/engage/ask-an-engineer/what-is-the-relationship-between-the-length-of-a-boat-and-its-maximum-speed/ https://engineering.mit.edu/engage/ask-an-engineer/what-is-t...
mhandley 4y ago
As a boat moves through the water it creates a bow wave. The wavelength (ie crest to crest) of the bow wave increases with boat speed. Once the wavelength of the bow wave equals the hull length, the boat will start climbing the front of the bow wave and will be sailing up hill. Unless you've got a lot of power and can climb on top of the bow wave and plane, this is the maximum hull speed.
- sprkwd 4y ago
  Best explanation I have ever read for that.

User23 4y ago

> The thing that blew my mind, and continues to, is that the top speed you can reach is dependant upon the length of the boat and not the weight. This is true for any rigid body traveling through a fluid. It comes up in ballistics too.

sopooneo 4y ago

The most mind blowing down “wind” sailing I’ve ever seen: https://m.youtube.com/watch?time_continue=13&v=q2il8Fagbyk&feature=emb_logo https://m.youtube.com/watch?time_continue=13&v=q2il8Fagbyk&f...

Kon-Peki 4y ago

“Modern” things ;) It’s been 94 years since Uffa Fox built the (planing) Avenger and thoroughly destroyed his British competition on the Isle of Wight. And then took that little 14-footer across the channel to do the same to the French. All because the elitist snobs didn’t want him to join their club :)