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Hole In The Wall And Double Checking The Data

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The channel seemed almost calm—“Hole in the Wall” is an apt name for this place, just up the road from Desolation Sound in British Columbia. We were surrounded with the beautiful steep walls we have come to take for granted, sheltered from the wind, and under sunny skies. This trip was not quite routine for two reasons. First, we were on our way to the Octopus Islands Provincial Park for our first visit. A new place is exciting and requires some preparation concerning route planning and familiarity with potential hazards such as water depth at the entrance. The second reason is this was to be our first time passing through “Hole in the Wall.”

We are not new to ‘rapids.’ In this part of B. C. the channels and passages are narrow. A large volume of water has to get in and out of the Georgia Straits each time the tide changes. Nautical charts of all cruising areas have several names for narrow bodies of water like Trincomali Channel, Discovery Passage, and Dodd Narrows. In this area, we see the designation—Rapids—so named because when the current is running at its strongest, it truly looks like rapids in a river. One might think that an 8-knot boat could motor against a 7-knot current; it would just take a long time. This might work in a canal or test tank with smooth uniform banks and an even bottom. This is not the case in the real world of rapids. The edges of these passes are irregular and the depths vary. Back eddies and whirlpools add spice to the mix. Sailing directions and cruising guides strongly suggest that no matter what type of boat you are operating, you should calculate slack water and go through the rapids close to that time.

The phrase ‘close to slack water’ means different things at different times at different rapids. During spring tides where larger water level changes require greater volumes of water to get through a given space, close to slack means darn close. Neap tides and less restrictive channels may allow more leeway when it comes to timing. Have there been recent heavy rains or very warm temperatures melting nearby glaciers? This increases the amount of water that has to pass and will affect the speed the water moves. At some rapids, plus or minus 10 minutes will work. There are other places where 45 minutes of slack is pretty comfortable. You need to time it properly on your own. Be cautious at first, then refine it.

At the west end of Hole in the Wall is a rapid. The slack time between water moving rapidly northeast and moving rapidly southwest is short. What I mean is neither the 45-minute possibility nor the 10-minute options are available. You really should hit ‘the hole’ within two or three minutes of slack unless you are a thrill seeker and have Red Bull as a sponsor.

Determining when slack water occurs is normally straightforward. On this trip, I used a tide and current table we bought at the boat show. It was better than the Canadian hydrographic tables because it converts standard time to daylight savings time in the spring. The time of slack water where we were going is based on the slack at Surge Narrows. To this Surge Narrows time, one applies a correction of plus 50 minutes. Slack at surge is 1344, so Hole in the Wall is slack at 1434. It’s easy math—as long as your data is good.

So, I figured out a good time to leave Refuge Cove (where we picked up our daughter, Jenny). At normal cruise we would arrive at Hole in the Wall a little early. It’s best not to be late. We could always loiter a while and go through right on the money. I put a waypoint on the chart plotter at Hole in the Wall’s west end.

The channel leading to the rapids was still calm, and the beautiful scenery was still with us. There was sun and no wind, and we were still going to arrive at the rapids right on time. As we got closer I noticed a little water taxi skim toward us through the narrow pass. They didn’t seem to have to wait until slack. A different hydrodynamic is involved. He waved and scooted by. This was new territory for us. That water seemed to be moving fairly fast considering that slack was scheduled to happen in about seven minutes. Something did not look right. My wife and daughter chimed in and commented that it did not look close to slack where we were going. I assured them that I had done the calculation and checked three times. We were moving along to Hole in the Wall with a 4-knot push. At some point, I was not able to turn our boat around to keep from going into the rapids that were clearly running at a speed that would have us out of control. Discretion being the better part of valor, I made the turn and we slowly, very slowly, headed back up and away from the very, very, rapid rapids.

The trip to the Octopus Islands was off. The next possible slack was six hours later and we did not wish to delay and arrive at an anchorage that late, so we picked another destination. I rechecked my math. I had not erred. Had we had cell phone coverage, I would have been on the phone to the tide and current book’s publishers in a big way. The next day we reached them (I am sure they wish to remain anonymous). I had cooled off considerably. The problem? The sign before the 50-minute correction from Surge Narrows slack water should have been a minus, not a plus. We were an hour and forty minutes late for slack. To their credit, they had emailed people to inform them about the typo. We were not on their list. They said we could have a free book next year at the boat show.

Back when this happened we did not have two sources to check the current and time of slack water. Now we use Nobeltec, which has tide and current information elegantly displayed. We always check computer information against the tide and current tables. As we found, it is possible for current tables to be wrong. But computer software provided data—could that ever be wrong? Our laptop running Nobeltec has nothing else loaded on it and therefore never goes online. If I forget to tell Mr. Nobeltec what the proper time is when I turn the laptop on, he will give me bad tide and current information. Garbage in, garbage out. Now, I always double-check charts against computers.