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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Thursday, June 07, 2007

Project Management and the tortured soul


Free Spirit as seen from the mast of P'tit Lois
(with thanks to her crew for the photograph)


For those readers that have not yet gathered this yet, a refit on a 50' steel sailboat is not an insignificant undertaking. About 20,000 hours ( ten full time person-years) went into her initial construction. A refit, such as we are doing, can range from 10 to 70 percent of her initial build. In our case the hull and most gear was in very good shape, and I estimate that we will have only 3900 age adjusted worker-hours into the refit when we launch in December of this year.

The countless details, mind numbing and back breaking work, difficult conditions, and elaborate logistics all add up to more than most can expect to undertake. To complete this type of project as a family team, we have had to steel ourselves to the task, spending 75% of our waking hours on the task, six days a week. Even the youngest puts in a pretty good days work.

Morale is a delicate balance. Even a small upset causes ripples that can be felt for days, a large disruption weeks. It is hard to see the end of the work for an adult, much less for a child. If we don't achieve our daily goals, the morale of the boys is hit the hardest, and work problems often crop up with them for the next few days. Even my own morale is sometimes tenuous, as I have never been big on delayed gratification. Laura, the pinnacle of strength that she is, never shows a shred of doubt - though she endures hour upon hour of back pain in the completion of her endless duties as main deck crew, purser, and cook. Sometimes I despair that the work will never end - especially when weather, fate, or other complications in life contravene our steady progress. These dark hours do nothing to improve the moods of my crew, of course, so I do my best to suffer in silence. When it gets to be too much, a word or two in confidence with the purser helps me to lift my spirits, thanks to her deep well of optimism and faith.

Which all boils down to the why. What were we thinking? Most people will never understand, I suspect.

The answer lies somewhere between building a home and leaving it, squarely athwart of mainstream culture, and never closer than a few points off our imagined path. The best explanation I can muster is a question: Have you seen the world? What wonders, what peoples, what scenes hide under these stars. Does not your soul thirst as well?

For a sound-bite version of the question-answer, I recommend an excellent movie called Baraka , by Ron Fricke. If you can't find the movie in your local video rental outlet, or would like to own your own copy, you can purchase it here.

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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 =