Hydrophone work with Dr. Jay Barlow

Written late on Aug 14th

Day: 53 Odometer: about 1,850M
Position: N24 35’ W146 11’
Distance from start: 1,502M
Nearest land: Point Kumuhaki 568M due 239T
Waikiki Yacht Club by my course: 679M due WSW
ETA: end of August

RECORDS as running totals
Solo career total in days at launch: 845 now 898
Overall career total in days at launch: 928 now 981
Solo career total in miles at launch: 27,595M now about 29,445M
Overall career total in miles at launch: 31,083M now about 32,933M
==> Ralph Tuijn (NL) leads the last one with 35,635M

Actual distance rowed in miles until Waikiki will append to my existing career totals at launch in solo and overall categories; to become official, London based Ocean Rowing Society must adjudicate supporting GPX files from my chart plotter and YB Tracker.

—-oOo—-

A few days ago the winds began to weaken. I had been on a mission to keep advancing west to outrun yet another tropical storm, this time Hurricane Linda. If I could get far enough west, it would weaken by the time it approached my vicinity, went the logic.

Yesterday was a stifling windless day yet I still managed 24M in 24 hours. Then came today which brought first SE then S then SW 5-knots breeze. The sea state was mellow with long period undulating waves which created a “breathing” sensation at the surface level providing some relief. When the sun and its reflection became piercing, I rummaged around for my SPF-rated white long johns and despite the extra layer over my skin, the sense of cooling was immediate.

The SW breeze in the afternoon was essentially a headwind. When I rowed, I easily maintained 270T COG at 1 knot speed. When I stopped, the rowboat wanted to run northerly at 0.6-0.8 knots. Clearly I was not going to win this game. The forecast was for southerly breezes through noon on Monday.

I decided to deploy my para-anchor from the bow to see how the system would behave. I hoped for the water under my rowboat to move west or WSW to counter the breeze action which is exactly what happened, immediately reducing my drift to under 0.25 knots.

I was able to get in the cabin with the main hatch half open and the rear hatch cracked ajar for cross breeze. The latter is always shut under normal circumstances to avoid a splash into the cabin, but with the bow turned into the breeze and sea state mellow, the cabin offered the ideal shade for me to enjoy. The rowboat had practically stopped for my enjoyment!

When I started the day, I was determined to deploy the high frequency SoundTrap hydrophone to gather ambient sound data for Dr. Jay Barlow. He is a NOAA scientist gathering data about the range and activities specifically of the Beaked Whale species. He wrote: “Most beaked whale are active 24/7 but one species only talks to us at night. So I have a slight preference for nighttime data collection. The night beaked whale is just called BWC or the Cross Seamount beaked whale. We think it is the gingko-toothed beaked whale, but we still need to verify that.”

The SoundTrap hydrophone is a neat self-contained cylindrical device which records underwater sounds for later retrieval. I fit this hydrophone into a towbody which is an acrylic tube that floods around the device. I turn on the hydrophone using a remote, then deploy it in the water at the end of a 25 meters long 3-mm Kevlar cord. That is tied to a 6-lbs lead ball which hangs 10 meters below my rowboat again held by a Kevlar cord.

Ahead of my launch, I had attached a tie point on the skeg just forward of my rudder to which I permanently spliced a fixed length Dyneema strop. This reaches the side of my deck to attach the Kevlar cord to deploy the hydrophone. I have a retrieval line that is twice as long as the strop which I tie to one of the spare oar locks. When I pull on the retrieval line, I can reverse the deployment, bring up the 10-m line, lead ball, 24-m line then the towbody…

I experimented with the towbody earlier and I found that it behaved like a small drogue. I had chosen a tie point location aft center of the rowboat which influenced the directional behavior of my rowboat. With the device deployed, the rowboat wanted to point straight downwind. Earlier in the crossing with persistent northerly winds, I needed the rowboat to run diagonally across the waves to gain some westing. The hydrophone created lee helm. Later in the crossing, I went through a 10-day period of squalls with aggressive northerly winds. Again that was a no go.

Then the excuse became the need to maintain high mileage to stay ahead of storms like Hilda. The hydrophone slowed my rowboat by 0.6-0.8 knots. There was the option to shorten the 10-m Kevlar to 5-m to reduce drag but still…

While the drag and the speed penalty are a given, as I am typing this update, I wish that I had made one more tie point at mid length to not pay the directional penalty. Even at Waikiki I cannot drill into the skeg unless we lift the rowboat off the water… I should experiment with dangling a bridle under the rowboat tied to opposing oar locks on either side. By moving the bridle from aft oar locks to middle, I could judge its effect on the course that the rowboat keeps. I have thinner Dyneema cords that may provide a low drag option…

So today started with towing the hydrophone. I was going to tow for four hours. I maintained 1-knot speed but a couple hours later, I simply could not travel west with the SE breeze. Up came the hydrophone. However when I retired later using the para-anchor, that became the ideal setup to also deploy the hydrophone. The device will record for as long as I am on para-anchor which is until Monday morning.

I will pull up the hydrophone once every 24-hours to transfer the sound data first to my laptop then on to an external drive while also recharging the device. Down it will go again…

Starting on Tuesday night, the leading edge of by then Tropical Storm Linda will bring steady ENE winds. With that, and the bridle under the rowboat idea to try, I am hoping for more opportunities to record until Waikiki…

Erden.