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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Saturday, April 29, 2006

Suisuin Bay to Owl Harbor

The run from Suisuin Bay to the marina at Owl Harbor began mercifully late at around 1100.

The tide had slackened, and we were rested from the last nights adventures. (see the next story, below) We set off on a starboard reach South from our anchorage at the Northwest point of Sherman Island. When we turned east onto the San Joaquin, our relative wind became so weak that we decided to motor-sail up the river, at least for now. With the doddering 34 year old outboard pushing us onward as best it could, we made good four knots over the bottom. We had previously discovered that this motor prefers not to work too hard, so we were limited to about 1/4 throttle excepting short bursts of "war emergency power".

After we crossed under the big bridge East of Antioch, the breeze began to freshen and we cut the motor as we turned onto a port reach to the Northeast. Fortunately this time we wouldn't be running from the law like the last time we were here, as the rain upstream had subsided and the delta was reopened. The revelations divined from the book of wishes turned out true (no doubt due to the sacrifices) and we had a fair current the whole way, often making over 6 knots over ground upstream, though our waterspeed probably never got much higher than 5.

After a beautiful and relaxing trip upriver (often looking down on the surrounding farmland, an odd sensation) we finally turned the bend that marked the entrance to Westward's permanent berth. Entering the narrow channel to the marina, we took down sail with perfect timing and motored (a guilty pleasure after watching the engineless Knarrs) into our berth at about 1600, well satisfied in our accomplishments.

I'm not telling what happened the next day, though I will hint that Westward performed handsomely in her short career as a cable laying ship. By the way, the crab cakes upriver at The Riverboat are quite edible, and the homeward beat upwind in the dark was challenging if uneventful.

1 Comments:

Blogger SV Free Spirit said...

Can't wait to hear for the "rest of the story" :-)

12:55 AM  

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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 =