Log of SV Free Spirit and ships company

The chronicles of the schooner Free Spirit and her crew, embarking on an open ended journey upon the great rolling heap. Free Spirit is currently pursuing humanitarian and commercial goals in the Dominican Republic, on the island of Hispaniola. Working under the Ocean Reach USA and Paradigm Research banners, she is serving as logistics headquarters, workshop, and development laboratory for many ongoing projects. This is the log of her journey.....

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Thursday, September 14, 2006

Indigo skies

In Hood River the call of the sea echoes gently up the Columbia. Occasionally a glint of the Great Rolling Heap shows itself in the craft that pass by, a whispering reminder of the great Pacific ocean lying just beyond the treacherous Columbia Bar.

Here I walk the docks and long once again for the gentle lurch of an anchored deck underfoot. The comfort of terra firma gradually has given way to the desire to live within an intentions width of the infinite, To once again be tethered to the land with only a few lines, so than with only a thought the tiny cocoon of a ship that is my home can be eased towards the distant horizon, perhaps to make landfall on the far side of the earth.

Until then, some three thousand miles distant, our sturdy ship lies waiting. Surely by now she again suffers the indignity of wasp infestation, a few rust streaks, and yet another year upon her keel. Much work awaits, but like all insurmountable obstacles the bits will fall away, eroding until the last task has vanished in time. Once again she will taste the salt, feel the urging of the wind in her tanbark sails, the whistling in her shrouds. Again her decks will be alive with the patter of busy feet, the laughter of children under the cautious guidance of her master. This is the only life she has ever known, and it is this that she patiently awaits.


~%~


This morning I took my first formal kite(boarding) lesson. Like most machines of the air, control of the kite came quite naturally to me - and I trust that a few sessions, with sleep betwixt, will start me on the road to mastery. The power of even a small kite is quite impressive, and rigging schemes for automatic kite controls already invade my dreams.

I Talked to Raoul today, his thoughts also wandering towards his little ship and the upcoming voyage. Perhaps we will meet in December and accomplish some work towards his sea change. At least I'd like to pull Feng Shui's rudder and overhaul it while I'm there. I hope that his stint of work helps him to put aside a good cruising kitty, I'd really like to see him achieve his Eastern Seaboard cruising dreams next spring.

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Introducing Propcalc 4.0

Use Propcalc to easily match your hull with your engine, transmission, and propeller
Put the known data in the top fields, then hit the Update button to get the answers.
Results, of course, should be verified by a Naval Architect or qualified surveyor.
Data is provided for three bladed propellers of average type
For two or four bladed props, use the modifiers shown below.

Fill out the fields as follows:

Vessel LWL (ft) = Waterline length
Vessel Disp (lbs) = Vessel displacement
(max) HP = Rated Engine Max HP
Engine RPM max = Engine RPM at Max HP
Engine RPM cruise = Desired or estimated cruise rpm
(Cruise or Max) Kts = Speed to work the calculations for
Slip = Propeller efficience. 45% is average for a displacement cruiser.
Gear ratio = 1: Gear ratio of transmission
SL Ratio Adj. = This value will be added (or subtracted, if a negative value) to the calculated S/L ratio.

Key information:

If the "hp required" is greater than the "cruse HP", you have your cruise RPM set too low for your engine parameters.
If the "hp required" is significantly less than the "cruse HP", you have your cruise RPM set too high for your engine parameters.
If the "hp required" is greater than the "Max HP", then your target speed is too high for your engine/hull parameters.
The S/L ratio is calculated automaticaly based on your input. It can be adjusted if necessary, but normally it should be left alone.
If the calculated S/L ratio exceeds S/L MAX, then the results are likely to be non-predictive. Try a lower speed requirement.
SL Ratios of 1.1 - 1.4 are typical of displacement hulls. Semiplaning or planing hulls can go higher.

Typical propeller slip values:

Sailing auxiliary, barges, etc less than 9 Kts............45%
Heavy powerboats, workboats 9 - 15 Kts....................26%
Powerboats, Lightweight Cruisers 15 - 30 Kts..............24%
High speed planing boats 30 - 45 Kts......................20%
V bottom race boats 45 - 90 Kts...........................10%


Note:

it is possible to get irrational answers by irrational input , I.E specifying excessive speed for hull type and length
Any attempt to exceed hull speed (1.34 times the square root of the waterline length in feet) with a displacement hull are likely
to fail unless the hull is extremely fine (multihull) or otherwise exceptional. In such cases, an S/L adjustment would be in order.

2 and 4 bladed props:


For two bladed propellers, multiply the diameter by 1.05, and the pitch by 1.01
For four bladed propellers, multiply the diameter by .94, and the pitch by .98


PROPCALC
  Inputs:
Vessel LWL (ft) =
Vessel Disp (lbs) =
  (max) HP =
  Engine RPM max =
  Engine RPM cruise =
  (Cruise or Max) Kts =
  Slip =
  Gear ratio = 1:
  SL Ratio Adj. =
   
    Solutions:
  Prop rpm max =
  Prop rpm cruise =
  Pitch =
  Diameter =
  Static Thrust =
  Cruise HP =
  Cruise HP% =
  SL Ratio =
  DL Ratio =
  SL Max =
  HP Required =