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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Sunday, April 25, 2010

Rum Cay, Bahamas ~ 5-5 / 5-8 2009

A small church in Rum Cay..



~Christina~



Rum Cay was a very small island community just North of Crooked Island. It was our second stop after leaving Georgetown. The first one was at Conception Island, which is a uninhabited Island. We ended up staying here for only 3 or 4 days. We had to wait for the delayed mail boat to arrive so we could buy some fresh provisions.



A little Bar/Restaurant on the beach by the main dock.



Rock carvings were all over the area surrounding the marina on the south end of the island.



Just hangin' out being crabby :-)



Christina snapped this picture, and I find it hilarious. It would really appear that Mathieu and Bretton are being arrested! Fortunately, this was not the case :-)



~Drake~



Sumner Point Marina was our Internet Cafe location here on the island. We had to pay $10 a day for it, so we would all take turns getting done what we needed to!



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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 =