can anyone give me a relation between AHTS's length/breadth to bollard pull

[sujith]

i am working on my thesis
i need to know wheather a particular dimension satisfy for a certain bollard pull
is there any relation between ship's length/breadth with bollard pull

is their any formula for calculation ships power with given bollard pull


ship data
l=82
b=16.4
cb=.782

i want to know wheather 150t bollard pull satisfy this dimension


all i have design particulars of another vessel which has same hull form but of different dimensions
l=67
b=15.4
bollard pull=120t

is their anything i can do by refering rules for stability during towing

[cyclops]

I was under the impression a Bollard pull is just that. It is a static pull by a ship on a post anchored into a very strong pier. Shape or size of the ship should have nothing to do with the maximum pull available as long as solid water is surronding the screws or propellors.

[hateka]

I reckon you talk dimensions in meters. Bollard pull is a function of the installed power, and the propeller effectiveness. Free water flow to the propeller(s) has to be there of course. The larger propeller diameter the better. Ducted CPP propellers helps. (Kort Nozzle) Two or one ? But again, it is a compromise between free speed of the tug and maximal bollard pull. A recently built tug with length 45 m, B 11.2 m installed 2 x 2710 kW, 2 fixed props, diam. 3.22 m, ducted, made a bollard pull of 100 ton, and a free speed of 13.3knots.

[safewalrus]

I believe that Cyclops has the right idea - it's how much the engines can pull! But what do I know I'm only a simple seaman! Worked as mate on AHTS's for 17 years of some different sizes (not many different shapes! All roughly boxes! Some of the older ones did try a bit to look like ships but the newer ones!)

[hateka]

Further to my earlier reply, the normal way to obtain this kind of information is through a number, at least 4, compatible, existing designs, out of widely available litterature. Owners, more than builders yards are willing to provide information, because they sell the ship on the same info. An AHTS is basically a tug anyway, and tugs are sold / hired out on bollardpull.

[hateka]

For outsiders: AHTS stands for Anchor Handling Tug Supplier.

[safewalrus]

Wrong! AHTS are primarily supply vessels that CAN handle anchors (rig) and tow - sorry mate it's a box that carrys Oil Rigs drilling stores and can occasionally be used to shift them!

[hateka]

Both functions are basic. Its a tug with an open rear deck. Thats all. And a roller at the stern. But power is essential. Of course they are suppliers. But the strongest gets the job. Anchor handling is not thet important anymore. DP is more and more popular. But still the strongets gets the job.

[safewalrus]

Actually its a bit more than a tug with a rear deck - maybe in the gulf ports (texas and arabian) but in the North Sea theres a need for bulk fuel, water and various drilling powders, all underdeck 'cos with the distance travelled and amount used (partially due to the depth drilled) theres a little more required than can be carried as deck cargo - we ain't talking pallets but tonnes here, lots of! Anchor handling is not that important anymore? Pray how do we keep a drilling rig on station? Lots of bloody big anchors and chains thats how! OK so there are a few small well production vessels which remain in DP for the extraction process then steam to port to discharge, but these are the exception not the rule. Also exploration rigs use anchors and chains/wires. Anchor handling may be easier but it's still important (how many you done Hateka?) I'm afraid with an AHTS the Supply is still the bread winner! the Dedicated Anchor Handling Tug now thats a different beast!

[hateka]

I think you drift away from the subject. That was bollardpull.

[safewalrus]

Definately but......We need to be aware of whats do the bollard pull! don't we?