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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Friday, June 27, 2008

It's Always Something!

It's a good thing that this did not have to be explained to a boss!!
One of the risks associated with setting 2 anchors (which we pretty much always do), is that especially in the dark, you can easily get the 'set' anchor rode fouled in the prop. I did not completely understand this risk until it happened to us in Tavernier, and there were some choice words exclaimed from the helm and the bow at the same time!
The picture above shows where Raoul had to dive down, in the dark, and tie a rolling hitch from the black line to the anchor line. We had to do this so that we could manage the rode (anchor line) better and relieve some of the tension so that it could be un-fouled from around the propeller.



Finally we had it in our hot little hands!



Raoul taking a little breather, overcame some of his worst fears and dived down to do all the dark, creepy underwater work. (Diving in the dark, under a 25 ton ship, with fish nibbling at your toes and ears can be a tad unnerving.) Although we did have support from the whole crew, he was definitely the hero of the evening!



A few days later, P'tit Louis came to visit and tied their dinghy up to the regular stantion.... The wind was blowing quite hard, and much to our dismay it managed to completely break the stantion right above the deck. It turned out that it had not been welded, only tacked when we repaired it in the yard. Needless to say, all other repaired stanchions were meticulously checked, with no other problems found. It is a testament to the strength of steel that even thouh this one was welded on only about 1 / 20th ofthe way around, it still held for months, routinely bearing hundreds of pounds of loading, and only breaking when it was jerked hard enough to cause the whole 25 ton ship to lurch a bit.



The biggest challenge was figuring out how to weld it back in place, without damaging all the cables that were running through it, all the way up the mast! I went ahead and headed to town for my provisioning.... Of course, when I returned it was completely repaired and there were NO damaged cords. Once again..... My honey saved the day! We wrapped the wiring in a dct tape insulator to protect it from the red hot metal and keep it centered. Then we welded the stantion in increments cooling it between welds.



Once again, we had an unexpected problem... This one, like almost all the others that we have had, could not have happened at a better time. We had just (and I mean JUST), rafted up to P'tit Louis to watch the space shuttle launch, and we lost propulsion! The funny thing was that for about a week or so before this, I had been telling Tamer that there was a new weird sound coming from 'down there', when we were under power.
Well.......


So here's Tamer replacing the bolts that had become completely sheared off in the shaft. And, oh yah, it was affirmed that the strange noise I was hearing was from this problem :-) We were really thankful that it happened after we were securely tied up to P'tit Louis. It could have been a bit more difficult if it had happened while we were underway in the Intracoastal, though we always kept an anchor hanging for just such an occasion.



Can anyone guess what the boys are doing here?? I will give you a hint: Some little boys on shore must do this to their family car....
Yes, you were right, they were cleaning our family dinghy by scraping all the barnacles off the bottom. I'm sure that you all knew as soon as you saw the picture :-)
Happy Washing!!!!!!!!!!


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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 =