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, May 06, 2007

Blustery Day's



As proven by the current drought situation, storms are few and far between. But we do really love it when they come !! They are extremely refreshing, and who doesn't enjoy a good lighting/thunderstorm :-) Here is a little break in the clouds to the Northwest up the river.



One thing is for sure; when a storm hits here, it is hard and fast... These winds were gusting around 40-45 knots.



YES! We have been praying for rain. When we arrived here the middle of January, the water was well into the grass line. The level changes every day, but mostly it is way lower than any normal depth. The travel lift is starting to have a hard time lifting boats out of the slipway.



Drake, heading into the gusting wind...



Valin, enjoying the challenge of running out the dust storm.



Blayde, soaking wet.... and loving it!!



The wind was so strong that the chair you see on the right, blew all the way down the hallway that Nathalie is standing in, and almost off the porch.



Olivier, yelling at Tamer across the yard, to prepare everything for one heck of a storm.



A Couple of days later, just in time for our Sunday potluck, an even bigger storm arrived. I now understand what the term "raining buckets" means! I have never experienced such a concentrated amount of rain before. We had to go outside to fix the tarp that had come off of the Lathe, and were both completely soaked in less than 60 seconds!

Because of the above problem, we ended up staging the Potluck out of the Women's bathroom.... For obvious reasons (I shouldn't have to go into much detail here), the Men's bathroom was NOT an option :-)



The boys had the only semi-dry seats in the house, and were "Freezing" all throughout dinner.



Although not a very good quality of picture, a rare one of lightning.


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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 =