4/14/2018: Houghs Neck, Quincy, MA to Hull Gut and Peddocks Island circumnavigation. 12:00am-4:00pm. Two pods, Bob L (Green Explorer), Marc P, Shari G, Jim S, Christopher C; and Jeff C, Peter B, Sue H, Karen G, and Patrick D. Boston Harbor Navigation paddle. HT 10:55am 10.1 feet, LT 5:04pm 0.2 feet. Tidal range 9.9 feet, near last quarter moon. Low 40F air, mid 40F water, 1-2 foot chop, NE winds increasing to 15-20 kts as late afternoon storm approaches. We met 11am at Houghs Neck in Quincy. There was a brief consult with the harbormaster, who had kindly left the office doors open for us to dress and use the restrooms. In the pre-paddle briefing we discussed the overall goal for the day being an on-water review of navigation as we paddled around Peddocks Island. We further considered the big picture for paddling around Hull, Hingham, and Quincy Bays. To summarize:
The area has unique tidal dynamics of a scale less than, but approaching, the river systems around Boothbay in Maine. Due to the importance of Boston as a commercial port, the harbor currents are extensively mapped by NOAA. Figure 1 contains the marine chart of Boston Harbor showing the area we paddled. Appendix A is a data sheet showing currents for April 14-15 taken from the NOAA website. The appendix also has a chart, Figure A1, showing the locations of reported NOAA currents and rotary currents. There are two constrictions, West Gut and Hull Gut. The situation on the day of the paddle, 4/14/2018, captures the properties of flow around Peddocks involving these two guts. West Gut (data sheet graph #1) had a slack-before-ebb around 11:36am whereas Hull Gut had slack-before-ebb (data sheet graph #3) at 10:18am. That means that Hull had started ebbing a full 1.25 hours before West Gut. During this time, water was pouring out of Hull and entering through West. Water levels continued to rise until 10:55am when the drain from Hull finally turned the tide against the slowing West Gut flood. Once started, the Hull ebb reached a peak value at 2.32kts at 3:00pm, before ending at 4:54pm. During this long Hull ebb, the delayed West Gut ebb had started to drop from a peak value of 1.43kts at 2:03pm until hitting slack-before-flood at 4:59pm. The two guts are coincident at the slack- before-flood. The lag in ebb between West and Hull is due to the fact that West Gut is more exposed to the larger Boston Harbor tidal cycle through Quincy Bay, whereas Hull Gut is controlled by Hull and Hingham Bays. The two distinct phases were 10:18am-11:36am, water flowing in from West and out through Hull (cycling around Peddocks), and then 11:36am- 4:59pm, water flowing out through both Hull and West. These are shown in Figure 2. The current station #7R on the data sheet chart indicates a rotary current along the eastern shore of Peddocks. It is mostly flowing up to 0.4kts in a northerly direction towards Hull Gut, but had a few hours of stalled westerly flow. AREA OF PADDLE
Figure 1: Chart of Massachusetts Bay and Boston Harbor. Area of Paddle Indicated. Note constrictions of Hull and West Guts and locations of Hull, Hingham, and Quincy Bays. PHASE I: 10:18am-11:36am PHASE II: 11:36am-5:00pm
Figure 2: Phases of Tidal Flow around Peddocks Island on April 14, 2018.
After the briefing, we first moved out onto the Hough’s Neck dock and oriented charts to recognize Pig Rock, and Sheep, Bumkin and Grape Islands. I tried my arms-length thumb estimate of the Grape Island range. As seen on the Figure 3 chart, the island contours, separated by 20 feet, have a maximum at 80 feet. Assuming a peak halfway between contours (90 feet) we would have an 80 foot height-above-sea-level at high tide. My sighted thumbnail was just covering the island so, with a length of 1cm on an 80cm extended arm, we have a range 80/(1/80)=6400 feet. Taking 6000 feet/nm (actual value is 6076 feet), I found one and 1/15th nautical miles to the island. A quick check from the chart was 1.2 nautical miles. That was a reasonable result given the uncertainties in arm length and height. A more careful analysis at home; eye-to-thumb of 85cm, and using the 6076 feet/nm; I get 1.12nm estimate of a 1.18nm range – which is amazingly accurate! Of course, you would never use numbers like 85 and 6076 on the water unless you had a Gauss-like brain condition. We also tried horizontal estimates of distance using the British Army (reference Gatty and Eyges below) technique of looking at the shift of a finger at arm’s length sighted with left then right eye. I also counted knuckles of an extended fist. We ran out of time, and would consider this is detail the next day in Salem Harbor, but I did note that sighting from the left to the right eye did move my finger from Pig Rock halfway to Princes Head, which on the chart is close to the supposedly universal six degrees.
Figure 3: Range to Grape Island and Paddle Ground Track to Peddocks Dock. Observation of Sheep Island against Grape from Peddocks Island.
After orienting the chart and understanding our location, I noted that coming back to Houghs Neck from out on the bay can be confusing for people. The coastline will look featureless, and it is important to assess the back view on the paddle out to determine guidelines for the return. Of course, we have West Gut and Princes Head – but those landmarks are still distant from the put- in at the end of a long paddle. The key feature that pinpoints the public ramp is the topography of Houghs Neck. It is a very well defined hill of probably 100 feet height; and the ramp is just south of the hill. Everyone agreed that despite the many land and water features, Boston Harbor is no place to be without a chart. We launched around noon and headed north towards Peddocks. Our choice of mid-April for the paddle had a lot to do with expected boat traffic. As we were paddling up Houghs Neck a freighter and pilot boat were moving from the Fore River to Hull Gut. They were much too fast for us to catch up and intercept them in the gut. This was unfortunate as it would have been quite a sight! As we passed Pig Rock and the nearby daymarker, it was noted that the Pig and its Piglets were safe zones for kayakers crossing in mid- summer among a lot of boat traffic. During the day we defined safe zones – locations where paddlers would likely not encounter boat traffic. Except for one small but significant incident later in the Hull Gut, there were no more boats present during our paddle. We crossed West Gut after the ebb had started (see data sheet Plot #1) and first attempted to use the Hull Gut windmill against Prince Head as a transit. The problem was that the angle of the crossing was moving the windmill even if you paddled on the desired straight line. A more useful transit was formed by the edge of Prince Head against a large structure on Hull. After crossing on the transit we went to the east side of Prince Head. During a break there, we discussed the “Rule of 30”, namely that the boat angle on a transit is a measure of the current. In the crossing, I noted that at the peak current, my boat angle was about 15 degrees. A 30 degree boat angle for a 3kts paddler corresponds to 1.5kts current, so 15 degrees would counter .75kts of current. Certainly, it was no more than one knot. The ebb was probably closer to .5kts at this time so it was an over-estimate, but there were other factors such as the NE wind that may have been quartering at some points. Also, we were not making three knots on the crossing. At Prince Head we first encountered the “Hull Lighthouse”, a prominent vertical tower on Hull that looked just like a lighthouse. Some people thought they could see lights flashing from it, although on this trip I did not. We stopped to take a 90M bearing to the “lighthouse” from the Prince headland. This became a post-paddle discussion point described in Appendix B. As we progressed up the east side of Peddocks, we checked lobster buoys for the current which seemed slack. A member of the group noted a single moored sailboat pointed northeast, indicating a southwest flow. There was a slight NE wind, but it was weak and shadowed at this point, and it is known that moored sailboats are more impacted by current than wind (due to the keel). Hull Gut was heading for maximum ebb, and the effect could have been back-flow in the consequent eddy. West Gut had already started the ebb, which would contribute to a southwest flow. I decided that the evidence for a rotary current at this location would require much more sustained observation. Landing at the docks on Peddocks, I took a 105M bearing to the “lighthouse” after walking down the beach. We then worked on the problem of finding Sheep Island in Hingham Bay. This turned into an exercise involving compass bearings (177T), the Rule of Hues, and a careful assessment of the topography of land behind the island as seen on the chart. We were eventually able to find the low island against the distinctive topography of Grape Island. The sighting of Sheep against Grape from the Peddocks dock is shown in Figure 3. A picture of our Peddocks Island activity at this time is shown below in Figure 4.
Figure 4: Break on Peddocks Island
After our break on Peddocks, it was time to cross Hull Gut, now running near maximum of 2.4kts on the ebb. We crossed under the docks and went near the safe zone of the R”2” buoy before crossing. I had passed out the ferry angle calculation included in Appendix C, which we later discussed in detail at the in-house session on Sunday. It suggested a ferry angle of about 60T=75M would get us behind the Windmill Point eddy and minimize the time in the channel. The crossing was uneventful and the ferry angle seemed to work well. Note from Jim S’s ground track in Figure 5 there was an inconsequential overshoot, probably due to the fact that we were crossing with less than the assumed 3kts paddling speed. After regrouping in the eddy, we crossed again. Peter, Sue, and Jeff’s pod stopped in the mid-stream standing waves. Our pod crossed more directly according to a transit crossing. Just as we entered the flow, I noted a small motor boat heading in from Long Island with a very high upturned hull. The operator probably could not see us, and he was not in the channel. I was a little down-current so at more of a side view to the operator. I signaled to him that we had paddlers in the gut. He nodded and waved, and then crossed between the kayaks. It was a lesson that, especially at high water, boats do not stay in the channels.
Figure 5: Ground Track of paddle from Jim S showing crossings of Hull Gut.
We paddled to the northeast side of Peddocks and landed. I suggested to everyone to find the bearing to the checkerboard tower on Long Island, and verify it on the chart. I also said that with this long coastline, we really do not know where we landed; and part of the exercise is determining our location. People mostly looked for features to get a back bearing to the Peddocks coast. After a while I mentioned that there was a natural transit back to the beach from the two eastward buoys off Georges Island – G”3” and R”10” that pointed directly back to our location. In places like Boston Harbor, these transits are everywhere – buoys, daymarkers, island edges, land features, and etc. With a little care, a paddler can identify a point on a transit to determine location on the chart. Everyone then got the bearing to the checkerboard and verified it with the chart. The transit to locate our position along Peddocks is shown in Figure 6.
Figure 6: Transit locating a position along Peddocks using buoys off Georges Island, G”3” and R”10”. They are the first buoys encountered to the east of Georges looking out from Peddocks. Similar transit on southwest side of Peddocks.
The chill of increased NE winds, a darkening sky, and the predicted storm suggested it was time to head for the put-in. We were aware of this possibility from the forecast and synoptic chart in Figure 7 showing cold and occluded fronts crossing the area before the storm. It was unfortunate, since I had wanted to cross to Georges; and check out currents along Nantasket Roads (date sheet Plot #6) – but, next time. The west side of Peddocks (data sheet Plot #3) was much further along the return to slack-before-flood, and with the NE winds picking up around 3:00pm; we had a delightful push down Peddocks towards West Head. West Head itself was providing a wind shadow, and I took the opportunity to note the transit GC”5P” with the flashing red Sunken Ledge daymarker back to the West Head shoreline. This is also shown in Figure 6. Crossing West Gut around 3pm, from data sheet Plot #1 we see that the gut was still ebbing over a knot. This was expected since the drain of Hingham and Hull Bays was continuing. Hull Gut would be hitting its strongest ebb at around 3:40pm as the most delayed and persistent effect of the draining of these large bays. We split into two pods, one crossing directly to Houghs Neck to stay on the shore side, and the other crossing in an attempt to use R”2” as a transit. I initially went with the transit group, and suggested that everyone paddle into the safe zone cushion behind the buoy. I then moved over to briefly accompany a paddler with the shore group. Everyone was surprised by the difficulty of staying on transit because of the intensity of the increasing NE winds. Emerging from the cushion, the group then crossed easily to Houghs Neck and proceeded down to the landing. The shore group had already landed. There was a brief problem with a paddler’s skeg, requiring a landing on a Houghs Neck beach; but that was quickly resolved and everyone came to shore at the put-in around 3:30pm. It was such a successful day that I celebrated with two quick rolls before landing. The storm really was coming in at this point. Even during the packing away of gear and changing in the parking lot, there was a discernable worsening of conditions on the water. Total distance of about 5.7 nautical miles.
Figure 7: Synoptic Chart for April 14, 2018.
APPENDIX A: NOAA Website and Tidelog 2018 Current Data and Locations for Peddock Island Circumnavigation on April 14, 2018 in Boston Harbor
The relevant website and lat/lon location for current data is given with each plot. Figure A1 identifies the current data locations on the chart. Also indicated is the location of rotary currents (5R and 7R) as obtained from Tidelog 2018. https://tidesandcurrents.noaa.gov/noaacurrents/Stations?g=456
1. West Head, 0.2 n.mi. southwest of (ACT1411) Depth: 10 feet
LAT/LON: 42.2858° N 70.9530° W
https://tidesandcurrents.noaa.gov/noaacurrents/Predictions?id=ACT1411_1
2. Hull Gut (BOS1123) Depth: 9 feet
LAT/LON: 42.3034° N 70.9249° W
https://tidesandcurrents.noaa.gov/noaacurrents/Predictions?id=BOS1123_9
3. West Head, Peddocks I., 0.1 n.mi. W of (ACT1391) Depth: 10 feet
LAT/LON: 42.2908° N 70.9537° W
https://tidesandcurrents.noaa.gov/noaacurrents/Predictions?id=ACT1391_1
4. Peddocks Island, west of (ACT1426) Depth: 10 feet
LAT/LON: 42.2872° N 70.9653° W
https://tidesandcurrents.noaa.gov/noaacurrents/Predictions?id=ACT1426_1
5. Georges Island, .2nm WSW of, Rotary Current
LAT/LON: 42o19.02’N 70o56.10’W
6. Georges Island, 0.4 n.mi. SSE of (ACT1336) Depth: 10 feet
LAT/LON: 42.3112° N 70.9255° W
https://tidesandcurrents.noaa.gov/noaacurrents/Predictions?id=ACT1336_1
7. Peddocks Island, east of, Rotary Current
LAT/LON 42o17.50’N 70o55.52’W
8. Sheep Island, 0.3 n.mi. west of (ACT1476) Depth: 10 feet
LAT/LON: 42.2812° N 70.9330° W
https://tidesandcurrents.noaa.gov/noaacurrents/Predictions?id=ACT1476_1
9. Pig Rock, northwest of (ACT1491) Depth: 20 feet
LAT/LON: 42.2813° N 70.9425° W
https://tidesandcurrents.noaa.gov/noaacurrents/Predictions?id=ACT1491_1
Figure A1: Locations for tidal current estimates from NOAA website and Tidelog 2018. The numbers in red correspond to the plot numbers. Lat/lon values for each estimate and ebb/flood flow direction are shown above the plots.
APPENDIX B: The “Hull Lighthouse”
There was a post-paddle discussion via email on what we observed while paddling along Peddocks:
Well, intrepid sleuthing on google earth has possibly paid off! The mysterious "Hull Lighthouse" is probably the cupola over Memorial Middle School. It fits the bearings we took along Peddocks, 90M from Prince Head and 105M from the docks - both on the chart and the address of the school. These bearings indicate that it could not be Boston Light or the Fort Revere water tank. If you google it, the image shows a school building with a prominent tower that appears similar to what we saw. When people observed flashing lights, Minot was suggested as the only other lighthouse in the area (other than Boston and Graves). The line to Minot intersects Hull closer to the base; and more importantly, with a 10 mile visibility it would just barely be observable from Peddocks without Hull in the way. People with local knowledge noted that the color did not match the gray Minot structure. Also, as we paddled along Peddocks there was no parallax motion of the object against Hull - indicating that the structure had to be on the peninsula. I briefly thought it may be the old water tower on Fort Revere (in Hull), but the location does not match our bearings. So...my bet is on the school cupola shown in Figure B1.
105M
90M
Figure B1: Bearings to “Hull Lighthouse”
There followed a discussion on the observability of Minot from Peddocks:
The formula in Eyges and Gatty is that an object of height H seen from a height h will be visible to a distance of 1.14*(sqrt(H)+sqrt(h)) just due to the curvature of the earth, where H and h are in feet, and the distance is in nautical miles. If we put in the Minot H=85 feet and (sitting in our kayaks) h=3 feet, we get 12.5 nautical miles. Great – at a distance of 8.75nm, Minot is "observable" from Peddocks. However, look Figure B2 below (from page 206 in Eyges). It shows a 100 foot tower at 8 nautical miles. It is very tiny, much smaller than the "Hull Lighthouse". On the other hand, a light from Minot would probably be observable - so perhaps we are seeing Minot lights but assigning to another structure on Hull. If so, then probably not the cupola. But then the bearings are off - but they may have been in error, as we were bouncing on the water...Note that the cupola and a more southern tank have lit buoys around them. The radio towers probably have lights as well. Interesting problem!
Figure B2: Observability of structures over water. (Eyges reference, page 206).
APPENDIX C: Ferry and Transit calculations for Hull Gap crossing on April 14, 2018
We met on Sunday the day after the paddle to look in detail at estimating ferry and bow angles for crossing in current. I felt it was useful to consider two distinct approaches with different inputs to the problem. In the case of a ferry angle, in addition to current and paddling velocities, we consider crossing duration and balance distance vectors. Crossing on a transit is different in that we are continuously balancing the velocity vectors, and do not make assumptions about the duration of the crossing. The output in this case is both the bow angle (angle between kayak orientation and the transit line), and the crossing duration.
Below are vector analyses for crossing Hull Gap on the April 14th paddle using both of these approaches. Hull Gut is the fastest running stream due to the constriction of Hingham Bay into the rest of Boston Harbor. It can also have heavy boat traffic. This is a crossing where one should do some analysis beforehand. I used the NOAA data and assumed we will reach it by about 12:30 for the crossing from Peddocks Island to Windmill Point in Hull. Hull Gut encapsulates the general problem of crossing channels in current.
There are four charts: The first two use ferry angles to cross either as a 3kts or a 2kts paddler. The second two assumes the paddler uses a transit to cross the gut. As we discussed on Sunday, the assumption of ferry angle or transit requires a different vector construction. A ferry angle involves balancing distance = speed X time. A transit involves balancing velocity vectors. A paddler should be well versed in either approach because different conditions require different techniques. To summarize: note that a 3kt paddler is in the channel about the same time, whether by ferry angle or transit – about 5 minutes. However, a 2 knot paddler is in the channel for 6 minutes on a ferry angle, and 13 minutes on a transit. The 2 knot paddler’s bow angle is 60 degrees; an indication that a lot of energy is being wasted in compensating for the current. This could be relevant with boat traffic – a long 13 minutes in the mid-summer Hull channel is not pleasant. However, there could be other issues such as desiring to stay out of the more open water if swell or wind is present.
Summary for Chart #1: Hull Gap, 12:30 4/14/2018 Ferry angle crossing assuming a 3kts paddler. Green = ground track, blue = tidal current offset, red = paddle track. Ebb Current 1.8kts @340T
Desk chart scale 127.5mm/nm after xeroxing Distance of ground track .2745nm Time for 3kts paddler, .09150hr = 5.5minutes. Assume 6 minute paddle. Tidal offset 1.8kts*(1/10) = .18nm*127.5mm/nm = 22.95mm. Plotted in blue.
3kts paddler * (1/10hr)*(127.5mm/nm)=38.25mm. Use drafting compass at end of tidal drift vector to draw circle of radius 38.25mm that intersects the extended ground track. Where it intersects defines the paddler water track of 60T = 75M bearing. Total time is via the ratio 1/10 hour *(35/50) = 4.2 minutes.
Figure C1: Chart #1, 3kts Paddler crossing Hull Gut with a Ferry Angle. Notes from chart indicate procedure to construct relevant vectors.
Summary for Chart #2: Hull Gap, 12:30 4/14/2018 Ferry angle crossing assuming a 2kts paddler. Green = ground track, blue = tidal current offset, red = paddle track. Ebb Current 1.8kts @340T
Desk chart scale 127.5mm/nm after xeroxing Distance of ground track .2745nm Time for 2kts paddler, .13725hr = 8.23minutes. Assume 8.23 minute paddle. Tidal offset 1.8kts*(8.23/60) = .24705nm*127.5mm/nm = 31.49888mm. Plotted in blue.
2kts paddler * (8.23/60)*(127.5mm/nm)=34.998mm. Use drafting compass at end of tidal drift vector to draw circle of radius 34.998mm that intersects the extended ground track. Where it intersects defines the paddler water track of 63T = 78M bearing. Total time is via the ratio 8.23 minutes*(35/48) = 6 minutes.
Figure C2: Chart #2, 2kts Paddler crossing Hull Gut with a Ferry Angle. Notes from chart indicate procedure to construct relevant vectors.
Summary for Chart #3: Hull Gap, 12:30 4/14/2018 Bow angle assuming a 3kts paddler using Windmill Point to define transit. Crossing channel at right angles. Green = ground track, blue = tidal current offset, red = paddle track. Ebb Current 1.8kts @340T
Velocity vector scale on desk chart 1kts/inch Size of tidal current velocity vector (blue) is 1.8inches at 340T. Draw line parallel to (green) ground track through the end of the tide current vector. Water velocity vector for 3kts is 3 inches. Use drafting compass to draw three inch circle starting at starting point. Intersection determines the water velocity vector of the paddler (in red). Use compass to determine a bow angle of 15 degrees. The transit speed is the effective ground velocity vector in green. It is 2.125 inches for a speed of 2.125 kts. Compass at 113T on water track. Time to cross the channel is 20mm*(1nm/127.5mm)*(1/2.125kts) *60 minutes/hour=4.42minutes
Figure C3: Chart #3, 3kts Paddler crossing Hull Gut with on a Transit. Notes from chart indicate procedure to construct relevant vectors.
Summary for Chart #4: Hull Gap, 12:30 4/14/2018 Bow angle assuming a 2kts paddler using Windmill Point to define transit. Crossing channel at right angles. Green = ground track, blue = tidal current offset, red = paddle track. Ebb Current 1.8kts @340T
Velocity vector scale on desk chart 1kts/inch Size of tidal current velocity vector (blue) is 1.8inches at 340T. Draw line parallel to (green) ground track through the end of the tide current vector. Water velocity vector for 2kts is 2 inches. Use drafting compass to draw two inch circle starting at starting point. Intersection determines the water velocity vector of the paddler (in red). Use compass to determine a bow angle of 60 degrees. The transit speed is the effective ground velocity vector in green. It is 0.75 inches for a speed of .75 kts. Time to cross the channel is 20mm*(1nm/127.5mm)*(1/.75kts) *60 minutes/hour=13 minutes
Figure C4: Chart #4, 2kts Paddler crossing Hull Gut with on a Transit. Notes from chart indicate procedure to construct relevant vectors.
GATTY REFERENCE: Gatty, Harold, Nature is your guide: How to find your way on land and sea, Penguin Books, New York, NY, 1978.
EYGES REFERENCE: Eyges, Leonard, The Practical Pilot, Coastal Navigation by Eye, Intuition, and Common Sense, International Marine Publishing Company, Camden, ME, 1989.
TIDELOG REFERENCE: Tidelog 2018, Northern New England, Pacific Publishers, LLC, Tybee Island, GA; 2017.