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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Tuesday, July 01, 2008

Next Stop Charleston, My Dear! 6-15/6-23

After being at sea for a day or so, it can be really exciting to see 'anything at all' :-) This was a structure out at sea on our way from Cumberland Island to Charleston, which was a 47 hour trip all together.



The Free Spirit boys looking, well, maybe just a tad bit seasick.... It takes a day or so at sea for your body to adjust to being seasick if you are prone to get it. The problem for us so far is that our longest trip has been 56 hours, so by the time that you get comfortable, you stop again. I guess it is a small price to pay for all the adventures and experiences that we are having!



Container ships look WAY bigger when they are close to you out at sea... This one was coming from our starboard aft quarter for a couple of hours. We were maintaining a constant heading, so we would take binocular/compass headings to figure out which direction they were headed. Many of those big ships take a course heading and attempt to maintain it for days. He passed behind us about a 1/2 mile back, and it was neat to watch the ship sink into the horizon.



We had the most amazing, beautiful dolphin experience on this leg of the trip. Generally you will see and be visited by small pods of dolphins while at sea. But we were amazed at the size of the pod that we saw one this occasion. At first there were about 10 (which is normal), but after about 45 minutes of them playing in our bow wake and swimming around the ship, we realized that there were somewhere around 100! It was spectacular!!! There were 2 different varieties, and many different sizes.



You don't realize how playful they are until you can see them racing and jumping in the waves for as far as the eye can see. They would take turns at the bow and circle us over and over.



I was really surprised that none of them hit any part of the boat during their visit. The boys and I think that this experience was definitely the best animal one that we have ever had. I anxiously await the next encounter that beats this one :-)



Rupert, on Patrick's back completely tuckered out by a trip to shore. He has this incredible ability to sleep anywhere at any time.



Me, in Charleston.....



Fort Sumpter, on the way out of Charleston. We were not able to see many of the historical sights during this visit but plan to on our way back south this fall.



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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 =