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Michalak's Vireo Resting at Spruce Run (T. Clarke)

Saturday, December 24, 2016

John Welsford's Mollyhawk & A Texas 200

John Welsford’s Mollyhawk is 15% longer than his Seagull, but the widths and heights are the same. Though flat bottomed, she is narrow on the bottom, with flaring sides reminiscent of New England dories. With plenty of rocker, she makes a fine row boat. Plans are available on Duckworks.

Andrew Linn in One of the Two Mollyhawks Built at Toledo CommunityBoathouse

Mollyhawk is 5.336m (17 1/5 feet) long,
with a beam of 1.226 m (4ft 1 in) and
weighs 42 kg (93 Ib.) approximately.

Rick Laudervale and Andrew Linn Rowing Another of the Mollyhawks

Andrew Linn:
“She FLIES on the water - just slips along like a queen. Both Rick [Laudervale] and I weigh over 200lbs and you can see how nicely she trims [photo above]. What really surprised me was her maneuverability. The keel is just deep enough to get her to track nicely but she can turn in her own length.”

John Welsford:
“Recreational or sports rowing boats are often pretty easily upset, the narrow waterline beam making them very tender. In this boat, though, the bottom is wide enough to allow one to stand up within the boat (carefully), stability which, although it does knock a little off her performance, makes her a much more versatile craft and only about three minutes in the hour slower than her more sophisticated sister Joansa featured [in this blog post]." 
"Rowing a boat like this is nothing like most boaties have ever experienced, they move incredibly easily using very little energy, and once the technique of [establishing a rhythm in the oar stroke] has been mastered, it can be rowed for hours on end at a speed that would surprise many sailors. A good recreational rowing boat, unlike the delicate “toothpick” that the competitive rowers use, can cope with even quite extreme weather conditions, and with an experienced rower in charge will ride over seas that would put much larger boats at risk." 
"Mollyhawk! She looks as simple a boat as its possible to be, flat bottom, straight sides, transom, some seats and oarlocks. But they perform a lot better than many flat bottomed boats, and they do that because there was a heap of study, several tow test models, and two full sized prototypes before the shape was finalised." [dwforum Nov 27, 2016]

Rob Fisher and his son rowed the 2016 Texas 200 in a Mollyhawk… following is his description taken from his .pdf file.

"Rowing Tips for the Texas 200

By: Rob Fisher 
Now that the 2016 Texas 200 is over, my son and I have recovered, I wanted to capture some thoughts and suggestions for future rowers. Our significant effort for training, planning, and rowing allowed us to be 1 of 18 boats to arrive at all camps in 2016, rowing a total of 224.6 miles over 6 days and 10+ hours each day of continuous rowing. I hope these thoughts will help future masochists.

1. Boat Selection

What boat to row, selection is one of many trade-offs. You will have to deal with
very diverse weather, wind and water conditions. First you need to be able to
carry considerable cargo loads for all your gear and provisions. Just consider the
weight of the water we carried this year was 216 pounds. We experienced high
winds in excess of 20 mph from different directions, high waves and some
current. We built the Welsford Mollyhawk with two rowing stations. Weighed in
at ~170 pounds for boat and rowing stations. LOA is just over 18 feet, 4 foot
beam. 
Freeboard is needed for the high waves and cargo capacity, but it creates a lot of
windage. There were times when we clocked in at 3.5-4 mph without rowing
going dead down wind. The trouble was that it wasn’t in the direction we wanted
to go. Despite our amount of freeboard we still took waves over the side, over
the stern and one over the bow. 
Get an estimation of the weight you think you will carry. The single biggest load
was our water. We carried 26 gallons at the start. We carried it in 1 gallon jugs
which was great. It allowed us to move it around the boat to balance it
depending on the wind and wave conditions. We were consuming 4 gallons
each day for 2 people so we kept the empties in case we needed extra ballast
later in the week. The first days we had the highest waves and the extra ballast
from the water made our boat really stable. 
Sliding seat or fixed seat is a personal choice. We have always rowed sliding
seat. We prefer it as it allows you to use your leg muscles when rowing.
Through our training, [we found] if we rowed with the sliding seat compared to no sliding, it increased our speed by ~50%. 
Seat comfort (or lack of it) is extremely important and we underestimated this one. We used carbon fiber molded seats with thin padding. They felt fine for the first 20 or so miles for a couple days, but nothing feels good after sitting 11 hours every day for 6 days. By the end of the trip our back sides were suffering. 
One thing we didn’t have was a rudder. Traditionally in a row boat you don’t
really need one. Just take an extra pull on one side or the other to change
course. We found with the wind and waves it took considerable effort to keep the
boat on course. On day 2 we had a side wind of 20+ mph and there were times
we rowed for miles with the starboard oar only to go where we wanted.

2. Training 

I can’t emphasize this enough. What does it take to go from rowing in a racing
shell for a couple hours a week, to rowing 10+ hours a day, for 6 consecutive
days in a boat fully loaded with gear? One can potentially row and push yourself
for a day or two, but doing it 6 days in a row requires some base level of
conditioning unless you want to suffer a lot. 
Our training started in January, 5 months before the event. We were either
rowing on the water or on a rowing machine 6 days a week. During the week we
rowed one hour each day, then on the weekends we extended the distance using
a modified marathon training plan[see chart below]. During the long training days, we were able to test the boat, food, hydration, different weather and build physical conditioning.
 
In January we rowed 7 miles one Sunday and it took us 3 days to recover. At
that point we wondered how we could row 40+ miles each day for a week. The
key for us was having a written plan and sticking to it, never give up. 
Basic rule, build up miles for a couple weeks, then drop back to rest and build some more. At the end do a gradual taper to rest before the event. 
We developed a rowing strategy so that we could stay hydrated and fueled. We
would double row for 25 minutes, then one person would take a 5 minute break
to eat and drink while the other person single rowed. Then switch and start over
again. We did this non stop for 10+ hrs each day. We also took one long break
just over half way through the day. This allowed for more stretching and rest.
 

Rob Fisher's Training Regime for Rowing the Texas 200


3. Sun Protection
 

One constant for South Texas is the heat and sun. I can’t emphasize enough
how un-relenting it is. There are two strategies for sun protection. Use tons and
tons of sunscreen and hope you don’t miss something, or cover everything up.
We chose to cover up since we would be sweating a lot. Lightweight clothing
takes some of the heat load off your body. We didn’t want to get sunscreen all
over our hands and oars.

4. Hand and Physical Health

If you have rowed at all, you know that blisters are inevitable. The single most
important thing for a rower is keeping your hands healthy. We used a variation of
techniques during the trip. During all our training we found the single biggest
factor in hand health was keeping our hands as dry as possible. Wet hands turn
soft, soft hands get hot spots, hot spots become blisters. 
Our routine was to start out in the morning with bare hands for the first 3-4 hours of rowing until the sun started getting strong. Then we would tape up our hands and put on gloves. The gloves worked well for sun protection and to some extent they soak up
excess sweat. 
When we took a break every 25 minutes, the gloves would come off. This allowed for the hands to breath and dry a little. The tape was changed out a couple times a day. The tape helps protect from blisters and gives your fingers some extra support. Following that strategy, we had very few blisters.
The ones we did get weren’t debilitating and could be managed. We also took
hand sanitizer for cleaning our hands and oar handles. If you have ruptured
blisters, you don’t want an infection.

5. Hydration and Nutrition 

Rowing non stop all day long takes a lot of food and water. We consumed 2
gallons of water each day per person for food and drinking. We figured we were
burning something like 400-500 calories each hour of rowing. We started the day
with a hot serving of oatmeal. We joked that it should be an Olympic event to eat
one serving, but we never went hungry. 
One serving oatmeal:
   1 cup oats
   1 T chia seeds
   ½ cup dried fruit
   ¼ cup sunflower seeds
   ¼ cup pumpkin seeds
   ¼ tsp cinnamon
   1 T brown sugar
   2 cup water for thick, more is better 
It was nice to have a hot meal for breakfast. For the remainder of the day we
had snack food (no lunch). We tried a lot of different things for snacks. Keep in
mind it’s hot in Texas. Anything with chocolate becomes a mess. This includes
chewy granola bars which melt in the heat. Some different ideas we tried;
    various granola bars,
 
    peanut butter filled pretzel bites,
    various different trail mix,
    various nut mix, 
    jerky, 
   dried fruit, 
   peanut butter crackers 
   and cheese crackers. 
We actually had to force ourselves to eat. Since you are exercising a lot you
don’t really get hungry and if you are feeling hungry or tired, it’s too late. Eat
small portions and eat often, even if you don’t feel like it. 
Before the trip we portioned out snacks into small Ziploc snack bags and then divided out our snacks into gallon Ziploc bags for each day. 
Doing this helped when we were tired, all we had to do is pull out the food bag in the morning and we were ready to go. No thinking required. We ate on average 350-400 calories each hour. The hardest part was having enough variety. After 5 months of training, we were sick of pretty much every possible snack. For example, rowing 40+ miles over 10+ hours. Eating every 30 minutes comes out to 20+ snacks for the day. After a week, you need a staggering 120 snacks.

6. Navigation

Rowing offers an additional challenge for navigation since the rower faces the
wrong direction the whole time. There are very few landmarks on the TX200 so
a GPS unit is very helpful. Getting off course or zigzagging around adds a lot of
miles on a 40 mile day.
 
We used a handheld GPS and had our paper charts as backup. I made a GPS mount that attached to the rigger between the rowers feet so that you could look at it while rowing 
We made a course with all the way points for each day which was a direct course because we didn’t know any better. We didn’t take into account that the wind shifts during the day by as much as 90 degrees and changes direction as you progress north and east along the route. 
If we had to do it again we would have pre-planned alternate routes in case the wind changed. This was something we did not expect since we hadn’t done this before." 
I personally thank Rob for taking the time (and candor) to write this... informative and well written!
Tom


Love to see your comments below…

Sunday, December 18, 2016

CATCH: Small Boats in Epic Voyages


Dave and Mindy Bolduc, authors and adventurers, have curated an archive of epic voyages in small boats on their "micro-cruising" web site.

The listing is in date order and includes the length and name of the boat, who rowed/sailed/paddled it, a brief description and links to books, articles, photos and/or drawings of the boat. 

For example:
In 1876, Alfred Johnson, sailing/rowing his fully decked “Centennial” became the…
First person to cross the Atlantic solo West to East. This Grand Banks fisherman sailed his gaff-rigged dory from Gloucester, New Brunswick to Albercastle, Pembrokeshire. His boat is now on display in the Cape Ann Historical Society museum in Gloucester, MA.
Alfred Johnson's Centennial Crossing the Atlantic in 1876 

Someplace between untying gift wrappings and feasting on Plum Pudding, you may want to sit back and peruse this list… bury yourself in a true adventure. 

Have a wonderful Christmas Holiday and a safe...healthy 2017!

Best regards,

Tom  

Piloting Part 5: Dealing with Currents


Introduction


Ignore this post if you ONLY row/paddle in landlocked lakes or reservoirs... there are no currents. But if you ever even think about rowing in rivers, or bays/estuaries that are affected by tides, then continue on.

Tide and Currents


The tides are the result of the gravitational pull of the moon and sun…  the moon’s gravitational pull is about twice that of the sun. The gravitational pull causes a ‘bulge’ in the earth’s waters, about 18 inches (46cm) in mid-ocean. There is a corresponding bulge on the opposite side of the earth, and two ‘hollows’ 90° from the bulges. These bulges and hollows circle the earth about every 24 hours and 50 minutes.

But we don’t typically row in the middle of the ocean… we travel in bays and estuaries connected to the oceans. The bays and estuaries have water levels that attempt to keep up with the bulges and hollows in the oceans. They do keep up, but there are delays while the bays and estuaries fill up with water and then empty to match the bulge/hollow as is passes. This emptying and filling results in tidal currents.

The tidal currents, though caused by the tide, are not necessarily in sync with the tide. This means that the strongest tidal current may not be (and in most cases seldom is) at the half way point of the flooding or ebbing tide.

How do we know how strong the current will be, and when will it occur?

Current Tables


In the United States use NOAA Current Predictions: select the state, then the ‘station’. The image below is what will be displayed. At the bottom of that screen, you can change dates to be displayed as well as other parameters.

In the chart heading is the ‘true’ direction of the current, e.g. “Mean Flood Dir: 30° (T)”. (Subtract your local declination to convert 'true' to 'magnetic' direction of the current.) The peaks and valleys of the chart are also given in a text file on the right side of the screen. The speeds, in knots, are the maximum estimated speeds.

Example NOAA Current Table

Outside of the United States, NOAA provides a listing of resources for tide and current information by country.

Using the Currents


The current predictions (how fast and when) are for a single designated point. The current speed can be very different just a short distance away.  What are the factors that affect these differences in predicted speeds/times and how do you use these differences while you are rowing?


  • If a confined waterway (e.g., between two islands) becomes narrow (in width and/or depth of water), the speed of the current increases in proportion to the amount of narrowing. For example, if the waterway narrows 50%, the speed of the current doubles. Another application: Rowing under a bridge… stay equal distance from the two abutments to avoid eddies that occur as the faster current flows around the abutments.
  • The current is slower closer to the shore in a wide bay or estuary because the water is shallower. If you are rowing with the current, stay in the middle or deepest water where the current is stronger. If rowing against the current, stay closer to the shore.
  • The current is stronger on the outside of a bend in a narrow waterway, such as a river… and slower on the inside of the curve. If you are rowing against the current, stay on the inside of a turn… and if rowing with the current, stay on the outside of the turn.
  • A point of land protruding into a waterway often creates a ‘back eddy’ (reverse current) downstream of the point. Heading downstream, row well outside the point to avoid the back eddy. If going against the current, stay inside the point as long as possible to take advantage of the reverse current.
  • A steady wind blowing over a body of water for at least half a day will start a surface current flowing at a speed of about 3% of the wind speed. So an extended 20 knot wind will create a 0.6 knot surface current. Note that the waves created by this wind will increase in size if the tidal current is in the opposite direction.

How Fast is the Current?


When we do a look-up in the ‘current table’ (example above), the speed value is the estimated fastest speed of the current. As you can see from the discussion above, current speed varies a great deal for a number of reasons.

One way of determining  current speed is to use ‘speed made good’, which is your actual speed (measured along the shore… i.e., between fixed points) in comparison to your speed in the water.
Example: You are rowing at 3.5 knots and you row past two buoys that are 0.9 miles apart (according to your chart) in 27 minutes. You remember the ‘sixty D street’ formula (60D=ST), solve for S, giving you Speed = 60 x 0.9 / 27, which is 54/27, or 2 knots speed made good. This means the current is 1.5 knots against you (3.5 – 2 = 1.5).  
Example: But if it only took you a little less than 11 minutes to go 0.9 miles (still rowing at 3.5 knots), speed made good would be 60 x 0.9 / 10.8 which is 5 knots speed made good… you’re getting a 1.5 knot boast in speed from the current.
Two issues with this technique: You have to do some math in your head (the real world usually doesn’t come out in nice round numbers like these examples). And second, we have not accounted for wind. We’ll talk more about the effect of wind on rowing in Part 6 of this series.

Another way to determine current speed is to measure the current directly:
Current speed = 0.6 x Feet per Second.

Example: If I’m anchored in my 15 foot boat, and a twig floating in the water takes 5 seconds to go by my boat, the speed of the twig (current in this case) equals 0.6 x 15/5, or a 1.8 knot current. Note that this formula can also be used to measure boat speed…
Example: I’m rowing in Newport Harbor (Rhode Island) and spot a 12 Meter anchored… typically they are 70 feet (21.3m) long. It takes me 10 seconds for me to row by it… my speed is 0.6 x 70 /10 or 4.2 knots.
Example: I’m rowing Barnegat Bay early morning, no wind, at slack tide. I see a channel marker in my mirror… it takes 3 seconds for me to pass the marker from stem to transom (15 feet)… I’m rowing at 3 knots. (0.6 x 15 / 3 = 3 knots)

Crossing a Current 


The current table gives the estimated highest speed of the current, typically in the middle or deepest part of the waterway. The current becomes progressively less as you approach the edges of waterway. Because of this variability, it is difficult to predict where you’ll end up when you cross a current.

Let’s say you want to cross a river and end up at point X on the other side. In general terms, there are four ‘strategies’ to get to point X:


  1. Aim for point X (let’s assume 85°m) and start rowing. You’ll end up an unknown distance downstream (in the current direction) from X. Not a good strategy.
  2. Row upstream close to the edge of the waterway where the current is weakest. When you are ready, head across the waterway at 85°m. The current will take you downstream toward X. Where you’ll end up depends upon how far upstream you went before crossing. But you’ll be better off than using strategy 1.
  3. Use a range (two landmarks in line with X, an LOP). As the current keeps pushing you downstream of the range, change your course upstream. Continue to adjust your course (upstream or downstream) to stay on the LOP. This strategy, combined with strategy 2., has the advantage of landing at X and of minimizing the amount of upstream rowing/paddling that must be done in the strongest current.
  4. Do the following calculation to get the upstream angle (called the Ferry angle) you must apply to your course in order to get to X. Ferry angle = 60 times current speed/rowing speed.
Example: If the azimuth to X is 85°m, current speed is 1.5 knots (at about 180°m) and your rowing speed is 3 knots, then the ferry angle is 60 times 1.5/3, or 30°. This means you should row/paddle on a course of 115°m (85° +30°). And you’ll end up at X… well, not really. Because the current speed is not constant all the way across the waterway. You’ll probably end upstream of X, which is usually not a bad thing. 


In this post, we’ve discussed currents and how to deal with them. In the next post in this series on piloting, we’ll focus on how to deal with wind... but first we'll show you another John Welsford design and how it was used in the Texas 200.

The fine print...


I’m not a professional pilot. I try to be accurate and I check my information, but I’m not perfect. This post is for information purposes and is intended to be only a starting point for learning the skills of piloting. As with any activity with a small boat, there is always the opportunity for ugly surprises. Practice the skills under ideal circumstances and you’ll increase the probability of being able to use the skills during an ugly surprise to keep you and your boat safe.

Sunday, December 11, 2016

The Oxford Wherry 16 as an Oar Cruiser

Colin Angus offers a beautiful rowboat, the Oxford Wherry, that would make a really nice oar cruiser.

Colin Angus's Oxford Wherry

The specifications show that she is fast (note the bow wake in the photo above) and is capable of handling weight you would need for a weekend cruise.

Specifications:

  • Length Overall: 15' 10" (488 cm)
  • Waterline Length: 15' 7" (475 cm)
  • Beam: 38" (97 cm)
  • Weight: 53 lbs (27 kg)
  • Watertight compartments: 2
  • Depth: 11"
  • Freeboard at 250 lb displacent: 7.5"
  • Freeboard at 600 lb displacement: 5 "
  • Block Coefficient: 0.39
  • Prismatic Coefficient: 0.51
  • Sprint speed: 11-12 km/hr (6.5 knots)
  • Cruise Speed: 6-8 km hr (3-4 knots)
  • Maximum recommended touring load: 500 lbs (225 kg)
  • Maximum recommended short distance load: 600 lbs (270 kgs)

Colin Angus Comments:
“The Oxford Wherry combines elements of traditional beauty with modern design and construction to create a vessel that is not just gorgeous, but unbelievably fast and functional.  Its design takes the most positive elements of traditional wherries and Whitehalls – wineglass transom, carvel-like construction, and elegant woodwork - while jettisoning the less-than-ideal attributes such as excessive weight and beam… 
…The hull is shaped for true performance without compromising stability.  The vee bottom is almost flat in the middle further creating stability (a surprising number of designers create deep vees in similar style vessels which decreases stability and does nothing for performance).  The vee increases near the stern and bow to assist in cutting through waves and creating lateral resistance to enhance tracking…”
Interestingly, the Oxford Wherry can also be paddled, useful when exploring narrow creeks and marshes.

Oxford Wherry Paddling...

...or Rowed with Sliding Seat...

...or Rowed Fixed Seat

As I always do with row boat designs, I consider what modifications could be done to make it fit the definition of an ‘oar cruiser’ (see definition in right column in this blog), without compromising the hull design. What modifications could be done to make the Oxford Wherry an oar cruiser, suitable for week long cruises?

  • Add a water-tight bulkhead, with large access hatch, at each end of a 7’ (2.1m) rowing/sleeping cockpit, eliminating the designed seats, but retaining the frames.
  • Add a cross-planked set of floorboards for the cockpit, spanning the frames, to provide a dry sleeping platform and attachment points for rowing seat and foot rests.
  • Add fore- and aft-decks, as well as narrow side decks, using skin-on-frame, resulting in a cockpit opening of 4’ to 5’ (1.2m to 1.5m) long. These decks would partially cover the ends of the sleeping area.
  • Add a 3-inch (76 mm) coaming around the sides of cockpit to increase freeboard as well as a support for short outriggers (to provide oar lock span of 4 feet (1.2m)).
  • Provide rain protection for sitting headroom and sleeping using some form of shelter.


Colin sells plans for the Oxford Wherry as well as kits. The diagram below shows the panels that are provided in the very complete kit for the boat.

Wood Components in the Kit

Tom Fry has put together a 10 minute time-lapse video of building an Oxford Wherry.

Let us know your thoughts on using the Oxford Wherry 16 as an oar cruiser.

Sunday, December 4, 2016

Piloting, Part 4... More on Distance Off…


In Part 3 we discussed getting the answer to “Where am I?” and introduced a couple of ways to measure distance off… distance from a visible object that is also on the chart. In this post, we’ll show additional techniques to measure distance off.

More Preparation...


In the post on "Preparation", we suggested you print charts of the area you intend to cruise in. There is some additional preparation of those charts which can be very helpful when piloting the area.

  • Mark a scale on the chart for distance in miles or kilometers. For example, if the chart is scaled 1 inch to the mile, draw a line  4 inches long, with tick marks at 0, 1, 2 and 3 miles, then divide the last inch into eighth inches. Then it will be easy to measure distance on the chart.
  • Annotate major land marks such as water towers, bridges, light houses with heights, widths, colors, etc. If you do a Google search for the object, you can often find the required information. For example, when I did a search for Mantoloking Bridge , I found the center span vertical clearance is 30 feet and the horizontal opening is 80 feet. Published nautical charts typically provide this information.
  • Pre-measure and mark on the chart distances between points that will be obvious from the water. For example, the distance between two jetties protecting an inlet... distance between two small islands... distance between two shorelines that mark the edges of a narrow channel. You'll see in the discussion below how having these measures at hand will help you.


Objects Visible at Different Distances


We can estimate distance by noting what we can see at various distances. For example…

  • At 5 miles (8 km), we can see houses (but no detail), ships, water towers, light houses 
  • At 2 miles (3.2 km), we can see large trees and windows in the houses 
  • At 1 mile (1.6 km), we can see big branches in trees, large buoys
  • At 1/2 mile (0.8 km), we can see people as dots or sticks, small buoys 
  • At 1/4 mile (0.4 km), we see people's arms & legs, detail on boats, such as an outboard 
  • And at 1/8 mile (0.2 km), we can see faces, registration numbers. 


Using Small Triangle to Find Distance Off 


Doing this is illustrated in the diagram below:


Let's make this easier by simplifying the 'mathematics' we have to do...

How to Create the 'Small Triangle' Using a Kamal


To make the mathematics easier, we need to make a 'kamal'... an Arabic device that was originally used to measure the altitude of the North Star so that sailors were able to sail east and west (along a given latitude) between Africa and India out of sight of land for weeks at a time.

Here's one way to make a kamal: Use a 6" (15cm) plastic ruler and at least a meter (40+ inches) of heavy (durable) string. Tie one end of the string to a (carefully) drilled hole in the center of the ruler. Tie a second knot exactly 57 cm from the ruler. Leave the rest of the string... we'll use that for the second technique for creating the 'Small Triangle'.  

A small triangle 57 cm high with a base of 1 cm subtends 1°. So what? The general equation for  using a 'small triangle' for measuring distance off is shown in the illustration above. By introducing degrees into the equation and simplifying it, we can create a formula that is easier and more flexible in use:

                                     60 times Width of the target (in miles)
Distance off (miles) = ------------------------------------------------------
                                    Target angle in degrees as viewed on the kamal

Mnemonic: Sixty miles per hour over degrees.

Example: Looking at the chart, I see that the distance between a water tower and a building on top of a hill is 2.3 miles. I grab the 57 cm knot of the kamal with my teeth, keeping the kamal extended and perpendicular to the string, I align the 0 mm mark on the water tower and note that the hill-top building is at 5 cm (degrees).

                                                 60 times 2.3
So the Distance off in miles = ------------------
                                                         5

60 divided by 5 is 12. 12 times 2.3 is 2 times 12 (= 24), plus 0.3 times 12 (= 3.6) for a Distance off of 27.6 miles. 

This formula above works when the target Width is expressed in miles. Let's modify the formula so that it works with a target Width expressed in feet.

                                    Target Width in feet
Distance off (miles) = --------------------------------------------------------------------
                                    100 times target angle in degrees as viewed on the kamal

Mnemonic: My feet are over a hundred degrees.

Example: 
I'm heading for Mantaloking Bridge which has a vertical clearance of 30 feet.  Using my kamal, but holding it vertically, I align the 0 mm mark with the water and note that the bottom edge of the bridge itself is at 0.5° (5 mm).

                                     30                  30
Distance off (miles) = ---------------  = -----  I'm approximately 3/5ths of a mile from the bridge.
                                    100 times .5   50

How to Measure Distance Off with a 'Wink'


In the discussion above, the base of the 'small triangle' is the kamal (a 15 cm ruler) and height of the triangle is 57 mm. What if we use the distance between our eyes as the base of the triangle and 10 times that distance as the height of the triangle? 

If we do, we can hold up a pointer (finger, pencil, kamal...) at a distance of 10 times our eye 'span', sight on an object (e.g., a bridge from shore to shore) with one eye and then (without moving), sight with the other eye, the pointer will seem to 'jump' across the bridge. The length of the 'jump', measured on the object, is Width in the formula in the illustration below. 


If the 'jump' crosses the bridge in one jump, then the 'distance off' is 10 times the known width of the bridge. If it takes 4 'jumps' to cross the bridge, then 'distance off' is 10 times 1/4th of the known width of the bridge. If it the 'jump' spans 3 times the width of the bridge, then 'distance off' is 10 times 3 widths of the bridge.



The average ratio of eye span to arm length is 10:1. To make the 'winking technique more accurate, do the following:
  • Measure the distance between your pupils by looking into a mirror with a metric ruler aligned just below your pupils. My eye span is 61mm.
  • On the string attached to my kamal, I tied another knot at 61cm (10 times the eye span).
  • When using the 'winking' technique, I just hold the 61cm knot in my teeth and stretch out the string and use the kamal on edge as the pointer. 
The beauty of the 'winking' technique for measuring distance off is that all you need is the 'width' of the object, be it the horizontal opening of a bridge... the distance between two jetties... size of a large building. The calculations are easy... 10 times the estimated width of one 'jump' (on the object). The answer will be the same measure as the measure of the object width, i.e., feet to feet, meters to meters, miles to miles. 

Example: I'm rowing south of Mantaloking Bridge, where the horizontal opening is 80'. I align the pointer with the left side of the opening using my right eye. When I close my right eye and use my left eye (a wink), the pointer 'jumps' to twice the width of the horizontal clearance...So the width of the jump is 160 feet, and therefore the distance off is 1,600 feet. If the 'jump' covered 3/4's of the horizontal clearance, the width of the jump would be 60 feet and my distance off would be 600 feet.


Summary Available on Dropbox


Below is a summary of the key formula and factors (room to personalize it for yourself) for the piloting materials we covered so far. I've personalized my copy, water 'proofed' it with clear spray and glued it to the back of the map holder I made for myself... see Part 2 for the map holder.



This .pdf summary is available on this link... download and print it.

The fine print...


I’m not a professional pilot. I try to be accurate and I check my information, but I’m not perfect. This post is for information purposes and is intended to be only a starting point for learning the skills of piloting. As with any activity with a small boat, there is always the opportunity for ugly surprises. Practice the skills under ideal circumstances and you’ll increase the probability of being able to use the skills during an ugly surprise to keep you and your boat safe.