Boat Trim and Speed Trial

I devoted yesterday's effort to preparing the boat for today's sea trial.  This involved a lot of cleaning both inside and outside of the boat as well as rearrangement of stores. 

There was a fine film of dust from the engine work as well as the dry desert wind in every nook and cranny inside the boat.  I started off with cleaning the port quarter berth and closet behind the navigation station then restoring into them much of the material that had been temporarily displaced into the cabin and forecastle. 

Along the way I gathered up the impressive set of Sabb engine spares and handed over to Joel brand new oil filters, at least 6 fan belts, about 6  water pump diaphragms that I had ordered form Norway, all sorts of gaskets, etc.  Later I  delivered the old stuffing box and Sabb instruments (tachometer, oil pressure, ammeter) and Joel said that they would all be useful.  It was painful handing over this set of spares that had taken me years and considerable money to accumulate but this is inevitable when you make an engine change.  (What the economist Joseph Schumpeter called "creative destruction".)

I finished the day on deck with a water hose and I was amazed at the amount of desert dust that had accumulated in the ropes, rigging, chains, canvas, and every hard surface.  I looked at the boat's trip as I walked away and saw with great pleasure that Pachuca was almost perfectly trim in the water, with an ever slight nose-up bias.  Although the plow anchor is in position at the bow roller the chain and spare anchor are on the foredeck, which means that when I move them forward the bow will tend to dip again.  This should be compensated somewhat by the Zodiac and its Mercury engine which will be stowed at the stern. 

Brenda and I arrived at the boat this morning at 11 AM.  After settling in and doing some final preparations for departure Joel and a workmate arrived just before noon.  Leaving the slip was no problem because I was pointing bow out.  I kept the engine revs  low for the first 10 minutes to clear the marina and warm the engine up.  Our plan was to run down the narrow channel along the city front as though we were leaving La Paz then turn around and come back.  On the outward run we got a maximum of 7.9 knots at 2600 rpm.  On the way back we reached 6.3 knots at 2600 rpm.   Thus our maximum speed (after eliminating the effects of the current) was 7.1 knots.

The Volvo owner's manual states that the maximum rpm should be in the range 2800-3200 and Pachuca's theoretical hull speed is around 7.9 knots. 

To me it confirmed that Pachuca's 17" prop does have too much pitch.  The propeller calculator in the internet suggested a pitch of 14" and I had measured a 16" pitch on Pachuca's propeller. 

The next question in my mind was what are the ramifications.  The Volvo manual does not make a comment in this area. 

The return to the slip was to my mind perfect.  I employed the lessons learned from mistakes when I first backed into the slip months ago, overshooting the double slip, and being saved by 4 or 5 members of the morning coffee group who were waiting for me.  This time I sneaked up only a few feet from the line of slips and before the stern had cleared the end of the slip walkway I put the engine in reverse and let the prop walk nudge the stern into the slip just inches from the walkway.  Joel and his companion had an easy step off the boat to do the rope work.

Later in the day I discussed the speed findings with Mark at Port Townsend.  Tomorrow I will check and make sure that the throttle lever is providing maximum travel at the engine.  There may also be another issue of "throttle creep" since I could achieve 2700 rpm if I held the throttle forward but fell back to 2600 rpm when I let go of the lever.

Brenda's footpath challenge of the day does not make a very exciting photo. It is the metal protrusion. This one tripped Bob Carroll when we were walking with him a couple of weeks ago. It is about four inches high and very solid, being square channel. As it is in an otherwise trouble free walkway, defenses tend to be down. This is the last in the series for the time being. So far we have not managed to photograph the dogs with their snarling jaws on our side of the fence (this has happened to us twice), or the famous wire concealed by vegetation that can fling the victim onto the road.