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, August 25, 2008

Everyone Said We HAD To Go To Deltaville.......

While in Great bridge, we talked to a lot of folks about what we were planning to do, and where best to do it. Almost everyone said "go to Deltaville, it will be perfect", so off we went! Here you can see through the bridge at Great Bridge, on our way to Deltaville. Because of the numerous bridge openings and traffic, we decided to make an intermediate stop at Willoughby Bay, on the way to the bay out Hampton Roads.



On our way out past Norfolk, we had the opportunity to see a lot of shipyards and related industry. Here is an old ship being scrapped - you can see the pile of steel that it is being converted to in this picture.... all that remains is the front 1/3 of the ship, still visible here. The steel will be recycled, perhaps into a new ship someday!



One of the many bridges that we passed through on the way to Chesapeake Bay. Usually, you just call the bridge on the radio, and they stop traffic and open for you. In high traffic areas they often open on a fixed schedule, making it important to time your run from bridge to bridge. Add to the mix the railroad bridges -which are normally open, but typically close 10-20 minutes prior to the passage of a train and remain closed for another 10-20 minutes after- and it can get interesting at times!



The view as we approached the two lift bridges, one of which is visible in the distance. Off to the left you can see a row of navy tenders, used to support other ships with supplies, workshops. They sometimes also provide a little unofficial r&r, especially for submariners - who always welcome the sight of their tender with its large compliment of female crew.....



The tenders, as we approached. You can see by their rippled skin that they have taken a beating on the stern, having been slapped around a bit in the heavy seas they encountered at various points along their journeys.



Another view of the tenders, showing their gracefully rounded sterns to good effect, a welcoming sight to many a navy man back from the sea!



The lift bridges. The operator rides up and down with the bridge in the little house in the middle of the span. The far one is up, and you can see the near one on its way...



....up, all the way for little Free Spirit to pass through.



And down again. Here you can see the pulley and cable mechanism at the top quite well.



We passed through many naval shipyards, this one putting the finishing touches on what looked like a new (or maybe refitted) aircraft carrier, if a small one. No smokestack means it is probably nuclear powered.



Some guided missile ships. Long and lean, you wouldn't even get to see these peek over the horizon if they were after you.



Another pair of imposing bows. Not what you want to be seeing, except at a dock!



Fishing for sharks, the navy way - in Willoughby Bay. We anchored here and had a sound nights sleep before the journey up the bay.




The sun sets on another days adventure for the crew of Free Spirit.



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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 =