Call number:
ZSP-201-79/21
In:
CRREL Report, 79-21
Description / Table of Contents:
The report studies the question of whether Great Lakes freighters could move effectively through ice-clogged channels with the aid of tows provided by warping or kedging systems. Ten operational concepts are outlined, and their advantages and disadvantages are noted. The crushing resistance of floating brash ice is then analyzed. The neutral, active and passive states of stress for laterally confined brash ice are considered, and the resistance to horizontal thrusting by a smooth vertical wall is calculated for cohesionless brash ice, and for ice in which there is finite cohesion between the ice fragments. The thickening of the ice cover in the vicinity of a "pusher", and the formation of pressure ridges, are analyzed in order to estimate the amount of pile-up that can occur against a ship hull. The analysis then moves on to consideration of ship resistance by brash ice, taking into account crushing resistance at the bow, tangential friction at the bow, and hull friction aft of the bow section. Comparisons are made between thrust from the ship’s screws and the calculated ice resistance. The next section of the report estimates the force requirements for a warping or kedging system in terms of thrust augmentation for existing vessels. Tow cable requirements are given, and estimates are made for cable anchors and for anchorage of underwater structures. The force and power requirements for winches and windlasses are given, the practical problems involved in the pickup or transfer of cables are mentioned, and the report concludes with a brief appraisal. The conclusion is that a simple warping tug system is appropriate for a full scale experiment, a chain ferry with auxiliary barge seems attractive for an operational system, and a chain ferry plow may be an efficient way to clear ice from channels.
Type of Medium:
Series available for loan
Pages:
iv, 21 Seiten
,
Illustrationen
Series Statement:
CRREL Report 79-21
URL:
https://apps.dtic.mil/dtic/tr/fulltext/u2/a077801.pdf
URL:
https://hdl.handle.net/11681/9051
Language:
English
Note:
CONTENTS
Abstract
Preface
Introduction
Operational concepts
A. Warping tug system
B. Chain ferry system
C. Chain ferry with auxiliary barge
D. Ski tow system
E. Dual winch warping system
F. Simple kedging
G. Trailing-line system
H. Above-surface dual winch system
I. Pulley systems
J. Chain ferry plow
Crushing resistance of fragmented ice covers
Resistance to ship passage by broken ice
Crushing resistance at the bow
Tangential friction at the bow
Hull friction aft of the bow section
Total ship resistance from brash ice
Comparison of ship thrust and ice resistance
Force requirements for a warping or kedging system
Tow cable requirements
Anchors and anchorages
Force and power requirements for winches and windlasses
Pickup or transfer of cable
General appraisal
Literature cited
Location:
AWI Archive
Branch Library:
AWI Library
