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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Monday, January 22, 2007

Expediting is a way of life!!


Well, this morning started with great enthusiasm towards the productive work day ahead of us....

Sometimes things do not go as planned :-)

About 15 minutes into the very productive use of the just purchased on Saturday, scaler (an air tool that removes rust much faster than little boys with a scraper), the boys and I hear this HORRIBLE glass shattering sound. First of all, because of power issues, we have the very noisy air compressor set up right outside the front windows of the trailer. My first instinct was that the air hoses had come apart at their junction and the pressurized hose had broke out some of the windows on the boat. The boys raced out to make sure their Daddy was ok, and could hear him happily scaling away in the anchor locker, forward in the bow, where he could not even hear us calling. Upon closer observation by Blayde, he discovered that the whole pulley system on the back of the compressor, had basically shattered within the housing. So, he immediately unplugged it, and without the air pressure, Tamer started to wonder what was going on...

Now, dear readers, you have to understand that today was (in our minds) going to be the first day that we had all our little ducks in a row, and we could really get dirty! There is nothing more frustrating than being totally ready to start a project, and to be missing a stinking pulley,(or welding rod, or extension cords, or safety masks, or duct tape, or paint, or gases for the torch, or sand for the sandblaster, or hmmmmm, I know there was more :-) )

Anyway, we had a very productive day expediting around Fort Myers getting all the things that once we were in that mode, we realized we needed. There is a positive side to everything!! Now the breakers don't blow whenever the air compressor is on with any other drain on the power... The air compressor runs like a top (with the new pulley from an electrically defective model they happened to have on display at Harbor Freight tools. This made it so we did not have to wait for a week for a new compressor).... We have found a source for sandblasting sand that is $4.50 for 50 lbs instead of $40.00 for 50 lbs.... We can weld all over the work site instead of just at the aft end of the sandblasting pit.... And best of all we had some down time waiting for a supplier at Barnes and Noble with a Starbucks coffee and the new copy of Latts & Atts!! Life is good, and tomorrow will be the most productive day yet....... If I have anything to say about it :-)

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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 =