Boat and Ship behaviour

[kach22i]

I offer this article as a learing tool, it puts into simple terms some things you may want to know about, enjoy.

Marine Firefighting Inc.
Newsletter # 17
Maneuvering a Fireboat or Small Service Vessel Near Large Ships
http://www.marinefirefighting.com/Pages/Newsletters/Newsletter17.htm

[74-911]

Good article. I do a lot of sailing in an area with a lot of ship and barge traffic, much of the time in the narrow ICW or the Corpus Christi ship channel. The golden rule is: "Tonnage Rules".... stay as far away from the big boys as you can without running aground.

[kach22i]

I've been in a rubber raft on a river, I did not know if it was the current or the "bank cushion"/"bank suction" pushing and pulling me to and from the shore (could have been my rowing taking me off course).

I'd like to know if these forces are only at the surface and if they become worse with speed or less with speed.

[Seahawk]

Originally posted by kach22i
I've been in a rubber raft on a river, I did not know if it was the current or the "bank cushion"/"bank suction" pushing and pulling me to and from the shore (could have been my rowing taking me off course).

I'd like to know if these forces are only at the surface and if they become worse with speed or less with speed.

Kach,

Waayyy to many questions without context: speed of the boat, speed of the water (river), with current, up current and all the combinations inherent.

Then add rocks, drops and turns, mulitply by above because "hydraulics" come into play depending on the speed of the current, depth of the water and shape of the riverbed.

I've been kayaking for almost 40 years, owned a rafting company in the late 70's...the force has been with and without me.

Edit: I have also been the Officer of the Deck (OOD) during replenishment operations between two very large ships within 120-140 FEET of each other. The suction action tries to force the two ships into each other...you can see my little helo on the back of the ship on the left.

[Seahawk]

[Tim Hancock]

Originally posted by Seahawk
Kach,

Waayyy to many questions without context: speed of the boat, speed of the water (river), with current, up current and all the combinations inherent.

Then add rocks, drops and turns, mulitply by above because "hydraulics" come into play depending on the speed of the current, depth of the water and shape of the riverbed.

I've been kayaking for almost 40 years, owned a rafting company in the late 70's...the force has been with and without me.

An old college buddy and did the whitewater kayaking thing for a bit 15 years ago. We bought kayaks and gear and took a few classes with the local club. We mainly played in some tame rapids at the local Maumee river, but we did do a guided trip on the upper New (might have been the Gauly?) then the following day, I stupidly ran the last stage 5 on the lower (I think it was a five) just past the bridge by myself.

I made it past the nastiest part, but went over in the huge waves after. I made 1 feeble half hearted attempt to roll, then bailed. I surfaced for an instant then was immediately pulled under for what seemed an eternity. Finally I washed out and collected my boat and nerves. I was shaking when I got out! I loved kayaking, but it definitely demands experience!

[Seahawk]

Originally posted by Tim Hancock
We mainly played in some tame rapids at the local Maumee river, but we did do a guided trip on the upper New (might have been the Gauly?) then the following day, I stupidly ran the last stage 5 on the lower (I think it was a five) just past the bridge by myself.

I made it past the nastiest part, but went over in the huge waves after. I made 1 feeble half hearted attempt to roll, then bailed. I surfaced for an instant then was immediately pulled under for what seemed an eternity. Finally I washed out and collected my boat and nerves. I was shaking when I got out! I loved kayaking, but it definitely demands experience!

Any Kayaker understands absolutely what you experienced...I used to have a very good roll (with or without paddle) and still got stuck inverted a few times.

The Gauley is in West Virginia...I first ran it in 1988 when I moved to Maryland. It kicked my a$$...one of the few times I have ever been shy around water.

[kach22i]

Originally posted by Seahawk
Kach,

Waayyy to many questions without context: ................

Edit: I have also been the Officer of the Deck (OOD) during replenishment operations between two very large ships within 120-140 FEET of each other. The suction action tries to force the two ships into each other...you can see my little helo on the back of the ship on the left.

1. Sorry about the open ended question void of contex, I was thinking about something which happened 30 years ago - Never mind.

2. How do they keep the ships apart? I guessing they lower the speed, keep a safe distance and pray? No tugs out there, do any of the ships in the picture have bow or stern thruster?

[Seahawk]

Originally posted by kach22i
1. Sorry about the open ended question void of contex, I was thinking about something which happened 30 years ago - Never mind.

2. How do they keep the ships apart? I guessing they lower the speed, keep a safe distance and pray? No tugs out there, do any of the ships in the picture have bow or stern thruster?

No issues about your question, Kach, it is fun to try and solve those type of posts...

To answer your other question, please remember that I am not an expert on ship handling, rather, was conscripted as an "Air Boss" and had to learn the basics of the trade.

That said: The ships generally turn into the prevailing sea, make turns for eight knots or so and join up via very proscribed maneuvers. None of the ships have tugs or thrusters...they use rudder to counter the forces (think the venturi effect) of the water rushing between hulls.

Depending on the sea state, it is a fairly benign operation. Do a search on "Underway Replenishment"

[Tim Hancock]

Originally posted by Seahawk


The Gauley is in West Virginia...I first ran it in 1988 when I moved to Maryland. It kicked my a$$...one of the few times I have ever been shy around water.

I get the New River and the Gauley confused. The one we were at was in West Virginia and it has the bridge that once a year people sky dive or bungee jump off of (can't remember which... maybe both). Either way, I had no business attempting that rapid at the skill level I was at at that time without an experienced person there to coach/instruct me on the best way to do it. The upper portion that we ran the day prior with a guide/instructor was mainly class 2 with one or two class 3 rapids

[kach22i]

Originally posted by Seahawk
None of the ships have tugs or thrusters...they use rudder to counter the forces (think the venturi effect) of the water rushing between hulls.

I can imagine steel panels of the ship being sucked off the hull if going to fast.

The sides facing the opposing ship would be drawn together, like the uneven pressure on an airplane wing which causes lift.

[SLO-BOB]

Been sailing all my life and I might add, those big a$$ boats move a LOT faster than you might think. I was sailing the gap between Manitou Islands and Michigan (state) to do a crossing to Wisconsin. To starboard and ahead was a large freighter heading north. I was heading south. He was waaaay off starboard so I just went about my business. I was running a 170 up front and the winds were from the east (which is unusual) so once I settled in to the cock pit I lost sight of the freighter behind the big sail. No biggy. A few minutes later I went up to set up for a chute. When I got to the fore stay, I saw nothing but black steel. The freighter had taken a sharp right to navigate the gap I was in and he was now directly in front of us heading east. Didn't seem to matter that I was there. Maybe he never even saw me. I could only yell back to the people sailing with me to drop the sails and start the motor. In our panic all we managed to do was release the jib sheet and let the 170 flap out front of us ike a flag. It did slow us down a bit, but the speed of the freighter saved us. He steamed past and we drifted across his stern. At that point we were probably 200 feet from his stern, but it seemd like we could reach out and touch the freghter. It scared the ***** out of us!

Stay away from ships!