Monday
March 30, 2015

Homework Help: Physics/Nautical

Posted by Mike on Saturday, November 24, 2007 at 1:56am.

Further to my post yesterday re wave speed.

If a fast 25Kn 10m power boat had the choice of making a passage against the wind & waves (head sea) or with the wind & waves following (following sea). Assuming 15Kn wind in open sea conditions & no tide the skipper would choose to make the passage with a following sea. This would give a smoother & faster passage.

Once the tide is brought into the equation the picture changes. Wind & tide together creates a smoother sea state than wind opposing the tide. Apparently a point is reached when it would be preferable for the skipper to make the passage into a head sea providing the tide is flowing in the direction of the wind. Rather than in a following sea in wind against tide conditions.

I understand wave speed is a very complex issue but I have noticed waves generated by 15Kn wind overtake my 8Kn fishing vessel. I assume a wave crest speed of 10Kn which I believe is sufficiently accurate to use in the following examples.

1. A vessel doing 25Kn into head sea impacts the waves at 35Kn.

2. Same vessel doing 25Kn following sea impact speed reduced to 15Kn.

Example 1 wind & tide together makes slightly smoother sea state.

Example 2 wind against tide slightly rougher sea state.

Considering the above I fail to understand how a passage into a head sea would be the preferred option.

One thing I have not included is the rate of tide. Obviously the stronger the tidal stream the more noticable the difference in sea state between wind with & wind opposing the tide.

I have personally made a few passages in a 25Kn 10m vessel and have never encountered a situation when we would have preferred to take on a head sea than run with it.

I do hope I have explained my question clearly.

Can someone explain why make passage into head sea and what rate of tide would be applicable to make this preferred option.

Thanks

Mike

Answer this Question

First Name:
School Subject:
Answer:

Related Questions

algebra - Wind farms are a source of renewable energy found around the world. ...
Pre-Algabra - Unfortunately for mariners, the total amount of wave energy in a ...
College Physics - In Chapter 3 we learned that the force of air drag on an ...
8th Grade Math (Algebra1) - I actually have a few different problems that are ...
Nautical - With a steady wind blowing at 15Kn blowing over the sea is it ...
math - A plane makes an 900-mile flight in 3 1/3 hours against a strong head ...
algebra - Wind farms are a source of renewable energy found around the world. ...
English - 1. He died young. 2. He died when he was young. 3. When he was young, ...
Help - Erik bicycles 32 km/h with no wind. Against the wind he bikes 33 km in ...
Physics - A wind turbine has blades that sweep an area of 2000m2. It converts ...

Members