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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Books and more, at the Schooner Free Spirit Chandelry
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Sunday, February 22, 2009

Rough Seas 11/29

We were headed out of Southport, North Carolina with an outgoing tide, and a 20 knot wind coming at our nose. The result of this is 2 very strong water forces working against each other. We only needed to spend a little less than an hour heading out of the channel in a Southwestern direction, and then we would be turning to the West into better predicted winds. Amazingly enough, the weather forecast was wrong (I know this is a shocking occurrence) :-)
In the above picture, Kent makes his way to the bow in 12' steep seas. What you have to keep mind, is that a 12' foot wave is actually 12 feet from the regular sea level to the top or bottom of the wave... Making it 24' from the very lowest to the very highest point. The starboard anchor had come loose from the bow sprit and was banging on the hull and causing damage below the waterline. He and Paul had to spend a good 45 minutes up there, getting completely buried in water about every 5 minutes, to retrieve the anchor and tie it back off. They were amazing, stoic and brave during this task, and we were super proud of them!
The following pictures will tell the story on their own, all I ask is that you really try to grasp the intensity of the conditions.


There were times when you looked off the bow, and could either only see sky, or water.

The end result of this situation was that the weather DID NOT change, and we were in these seas for over 6 hours. Everyone on board was desperately seasick, but Tamer toughed it out and helmed us into a sheltered inlet just South of the North Carolina / South Carolina border. We were all very thankful to be safely at anchor, and ready to travel the Intracoastal Waterway the next day!


Blogger Gayle said...

The previous post had me glamorizing your life. Now I think you are insane. I want to live the carefree life as you do, but maybe I should stick to land. That is so intense!

2:10 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%


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

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. =
  Prop rpm max =
  Prop rpm cruise =
  Pitch =
  Diameter =
  Static Thrust =
  Cruise HP =
  Cruise HP% =
  SL Ratio =
  DL Ratio =
  SL Max =
  HP Required =