Sunday, August 09, 2015

Grand Tetons National Park boating

This summer we have been traveling, towing our boat to new locations.  We started at Holter Reservoir, near Helena, Montana, then on to McDonald Lake in Glacier National Park, and, from there, onward to Lake Coeur d'Alene, Idaho.  With the concern about invasive aquatic species, the boat has been inspected numerous times as we traveled from lake to lake.  In Wyoming, Montana, and Glacier N.P. the inspections were free.  In Idaho we were charged for a state sticker but received no inspection.  Then we traveled to Grand Tetons National Park.  There, we first had a park entry fee, then a boat inspection, then an aquatic invasive species sticker $30 payment, a boat entry fee payment ($40 season's pass only), then a $35 per day slip fee.  We then discovered that another boat was already tied up in our assigned slip.  It was almost sundown before we were able to launch and tie up in our assigned slip.  We were wondering if all the cost and hassle was worth it.  But, as we motored out onto the lake next morning, all our concerns faded.  The Grand Tetons have to be one of the most scenic mountain ranges on earth.  Steep, jagged peaks still with visible snow fields in mid-summer.  The mountains end right at the lake's edge; the shores are covered in undisturbed dense forest.  As we went out onto the main lake, I recorded a reverse compass bearing of the entrance to the cove where our dock was so that we could find our way back to it.  Jackson Lake is about 15 miles long by 7 miles wide with over a dozen islands and located at a high altitude of about 6800'.  From a distance, the shoreline blends into continuous forest.


We spent the next three days exploring the lake (as well as hiking).  The water is clear, cold, and deep (almost 450 feet).  Few other boats were encountered.  We went water skiing briefly (no wet suit).  The Tetons, especially Mt. Moran, kept attracting us like moths-to-a-candle with its high, rugged prominence and partially snow (glacier?) clad slopes.  The peaks were so picture-perfect they seemed like something computer-generated out of a movie.  The weather was cool and calm which meant very few waves.

We met my brother and his wife at the lake.  They have a 27' Sea Ray cruiser, twin engine, 430 hp, so we cruised the lake together, stopping in quiet coves for lunch.  I had mounted a 13" pitch propeller on my boat which provided extremely quick acceleration and a top speed of 33-34 mph.  We had a full tank of gas (18 gallons) because we spent hours exploring away from any harbor.  My brother, Jay, commented that he had never skied behind a boat which pulled him out of the water so quickly (and he has been skiing for 50+ years).  I could have easily mounted a 15" pitch prop which would have provided more speed.  My wife, Dawn, also enjoyed the boat handling, such as making high-speed circles, banking into the turns and creating a large wake.  It rained several times, mainly at night, but our full canvas enclosure kept the boat interior completely dry.


At this point, I am completely satisfied with my boat's performance.  The secret to success in this case is the strong but light-weight construction of the boat.  Modern wood/epoxy/glass construction provides a water-tight, monocoque, composite structure which is significantly lighter than normal fiberglass.  I should add that the boat tows on its trailer so easily that you can almost forget that it is there.  We towed on the highway at 80 mph or better when allowed.  Our SUV still got decent fuel efficiency, 16-18 mpg.  One thing needs to be addressed: I originally wanted to paint the topsides but was encouraged to finish it clear to show the wood grain.  Now the "clear" finish is becoming slightly opaque and uneven in color.  Before next boating season, I hope to sand and paint the topsides.  A black color, to match the deck edge, would be the most obvious choice, but I would prefer a lighter color to not absorb so much sunlight.

The link below is to a brief video showing the beautiful scenery surrounding Jackson Lake with our runabout gliding across its surface.

https://youtu.be/X1m7WiJS7S8
 
 

Wednesday, April 22, 2015

Modified "next boat" design

After re-considering the boat lines plan I posted a few months ago, I decided it could be improved.  The aft portion seemed too dominant, so I added more taper to the deck and topsides, and gave the transom more of a forward slant.  That aft section is now proportionally smaller.  My goal in developable designs has been always to show that a design that can be sheathed in plywood doesn't have to look "boxy", and I think that has been achieved.  Of course, a developable design can also be sheathed by almost any other technique or material.  There are no sharp curves which would require extra thin sheathing materials; 6mm ply will bend to

any of these curves.

An outboard engine of 60-90 hp should give 30-40 mph at the altitude here (6000') and somewhat faster speeds near sea level.  I have wondered about installing an inboard engine, revising the cockpit, and increasing the deadrise to 14 degrees (due to an anticipated greater displacement).  An inboard would have that authentic runabout aura; the deep rumbling exhaust; the weight and power to knife through waves, but I can't forget the many advantages of an outboard.

We will be busy this summer on some significant boating trips: the Grand Tetons in Wyoming, Glacier National Park in Montana, and Coeur dAlene, Idaho.  Our current boat is well-suited for the trip.  The ample freeboard and raised foredeck provide weather protection.  A newer boat is only a dream for now; however, I hope to build a scaled model this winter.

Because the design is created mathematically (geometry, algebra, trigonometry), the design is initially a table of offsets for a full-size hull. To make a model, the dimensions need to be scaled down and then plotted on paper.  Engineering paper makes the task easier for a model.  Full-size patterns require much larger sheets of strong, stiff paper (rosin paper) and careful plotting.

Wednesday, February 11, 2015

Sail design

Long ago, in 1983, I was building a two-masted 20' sharpie.  Naturally, it was a custom design and would require custom sails.  In order to save money, I would sew my own sails.  Sailcloth was ordered from the Sailrite company which is still in business.  At that time it was headed by Jim Grant (and may still be) who put out a quarterly newsletter.  As a customer, I received a newsletter which included an article on "broadseaming", a method of varying the width of seam overlaps in the fabric panels of a sail so as to control the shape, specifically the draft, of a sail.  Broadseaming was considered to be an art and somewhat of a mystery (at least in the published literature).  Just as plywood hull shapes can be described mathematically, I thought that sails made from stabilized fabric panels could be similarly described.  I wrote a letter to Sailrite outlining such an idea.  Later, upon receiving the July 1984 Sailrite newsletter, I discovered that Jim Grant had made my letter into an article titled, "The Mathematics of Sail Design".  Although CAD technology has progressed greatly since 1983, that article is included here because a recent internet discussion suggested that even now little has be made public.


Jim Grant overstated the difficulty of the mathematics required for these computations.  An inexpensive pocket scientific calculator provided necessary results for me, and the described method was used to design the sails for that 20' sharpie.  A photo of the sharpie is included in which you can see the shape of the sail draft by looking at the curved shadow that the straight sail boom makes on the sail surface.  The curvature appears to closely duplicate the cross-section shape of an airplane wing.
  I made one mistake in this sail design: the draft is too shallow.  Due to a lack of published data, I had to guess what the proper draft/chord ratio should be.  I guessed too shallow (it was about 7-8%); it should have been about 10-11%.  Although the boat handled okay, I have wondered how much more power the sails would have developed with a greater draft.

Sunday, December 21, 2014

Next Boat?

Should there always be a "next boat"?  Creating another boat design is always rewarding: changing a mental vision into something that is real; something you can see and touch.  The work of creating and building is a pleasurable challenge, but how many boats can one person use?  I only have space for one full-size boat.  To completely equip a new boat is far from cheap.  And there is no guarantee that the new boat will be better, only that it will be different.

With that in mind, I started on a new design.  The guiding idea was to create something with more curvature to be more visually interesting but maintain an uncomplicated build sequence.  A forward sloping bow profile with more lateral flare provides a more modern look and will also be easier to plank.  The raised foredeck of my previous build added complication to the build and would not blend well with the flared bow; thus, it was deleted.  The vertical stern on the previous build was helpful in providing internal volume for flotation foam, but it was esthetically bland.  The new hull would have a forward sloping stern.  The topsides avoid any slab-sided sense by continuously transitioning from significant flare forward to significant tumble-home aft.  In fact, tumble-home has been reduced to be more in harmony with the added beam forward.  Added beam means more usable cockpit space.

The result, if built full-size, would be a hull 18 1/2 feet long by 6 feet 3inches wide with a 12 1/2 degree deadrise for about the aft 1/2 length of the hull.  Of course, the hull surface is fully developable which simplifies construction and provides exact dimensions.

If you can't build the full-size boat, a model helps to visualize what has been designed and also really clarifies construction details.  Thus, I built a model at 1/6.25 scale (alternately expressed as 0.16 scale) which gives a model about three feet long.  I had enough scraps from previous projects to provide all the parts.  At this point I regret not spending more time creating a rigid strongback building form.  Some of the frames shifted as parts were bonded together resulting in a slight distortion in the model, but it still is accurate enough to serve its purpose.  And I was able to visualize



a much better strongback design to be used if the hull were ever built full size.  For now, the next boat is a dream.  Owner designed, home-built wooden boats are hard to sell.  I need more time to enjoy the boat I completed last spring, and a new boat would take about two years, spare time.  Anyone looking for a design to build?

                  

Wednesday, September 10, 2014

A Day at the Lake

Not much to report.  This summer in Colorado has been unusually cool and rainy, providing fewer dry, sunny days for boating.  Yesterday we did take the boat out and had a bit of an adventure.  Friends brought their boat, a 21' pontoon boat, also.  I had checked the weather forecast before leaving; nice weather until mid afternoon when wind and possible rain was predicted.

We joined up with our friends, who anchored their pontoon at the entrance to a small bay, for lunch on the pontoon's broad deck.  Everyone was enjoying the beautiful weather and showed no concern about a possible change later that afternoon.  Then my wife, myself, and our friend, Roger, left in our boat to explore the lake which was several miles long.  His wife and her two sisters stayed on the pontoon.  As we headed up the lake, the wind picked up, and whitecaps started to appear.  The waves continued to build, but by now we were at the upper end of the lake where we were somewhat protected.  As we came downwind along the opposite lake shore, I was able to make out the pontoon in the distance and noticed that it was no longer anchored in the center of the small bay, but drifting toward the shore.  When I pointed it out, Roger agreed we better get over there to see what had happened.  As we crossed the lake we met with the full force of the waves, 2-3 feet high.  We lowered our bimini to reduce windage and took some spray in the cockpit from occasional waves breaking on our starboard side.

When we got to the pontoon, it was being pounded on the rocks on the lee side of the bay.  The three women on the pontoon had decided that the anchor was dragging so they started trying to pull it in.  They did not take down their boat's bimini; they did not start the motor and use it to position themselves over the anchor.  Thus, their efforts to bring in the anchor only accelerated the effects of the strong wind and waves which quickly pushed their boat onto the rocky shore.  My job was to get our boat as close as possible so that a tow line could be passed.

The wind and waves were too strong to keep the bow of our boat into the wind while maneuvering slowly, and I wanted to keep our propeller as far as possible from the shallow rocky shore.  So I approached the pontoon bow first with the waves breaking against our stern.  The engine splash well and covered rear deck were valuable in keeping our boat interior dry.  Roger went over the side (with a life preserver), waded chest-deep to the pontoon, and passed a tow line to our runabout.  Then it was just a matter of putting our 75hp Evinrude in reverse and backing off, pulling the pontoon with us.  I wasn't sure that the prop would have enough reverse thrust for the task, but it worked well.

Once we were free of the shore, they were able to get their engine started and the tow line was returned.  We headed for a somewhat sheltered marina which was further downwind.  With the wind and waves behind us, we were able to surf the face of waves, and it became an enjoyable run.  On later inspection of the pontoon, the actual aluminum tubes had been protected by aluminum angles welded onto the tubes to act as strakes which minimized damage.

It frustrates me that all the women involved showed so little interest in learning competent boat handling.  This entire situation could have been avoided.  What happens if they encounter a more serious situation in the future?  People die from simple errors.       

Friday, July 11, 2014

Resting on its design waterline

If my wife were sitting in the forward seat, the boat waterline would be about exactly where I painted it.  Calculating displacement takes place very early in the design process.  This hull has a 12-degree deadrise. If I increased the deadrise, then something else would also have to change:  increase displacement (weight), shorten the waterline length, or risk the hull riding above the major chine which would decrease stability and may cause the hull to be louder at speed from water slapping against the hull bottom.

Increased deadrise will make the hull ride better in waves and may increase directional tracking, but it also could require more power to maintain planing speed.  Everything is a trade-off.

Saturday, July 05, 2014

At Flaming Gorge, Utah

A planned trip to Pueblo Reservoir had to be cut short because of an electrical short in the power tilt/trim switch.  Diagnosis was difficult; installing a new switch was simple.  There was a crack in the rubber cover for this switch which, after a period of use, allowed moisture intrusion to complete the circuit.  This past week we went to Flaming Gorge Reservoir in Utah for some real boating.  The lake extends into Wyoming for 75-100 miles filling a deep and scenic gorge.  We explored the lake for 30-40 miles and encountered some wind and waves.  It is a light boat with little draft so, when maneuvering into the dock with a wind present, we lower the bimini top to cut windage.  Also, when cornering while planed out, the hull will skid; when cornering while accelerating onto a plane, the hull will bank well and turn sharply.

There is almost no bow rise when accelerating, and the hull rides smoothly and cuts through moderate waves with no fuss.  I switched to a 15" pitch prop for this trip.  We were operating at 6000' altitude, and the engine achieved 4700 rpm, easily exceeding the 35-mph maximum speed of the speedometer dial.  The "sweet spot" for this engine is supposed to be 5000-5200 rpm and our next outing is at Grand Lake, over 9000' elevation, so I have ordered a new 13" pitch stainless steel propeller which, hopefully, will be perfect for these circumstances.  I have to think that, if we were near sea level, this boat would easily exceed 40 mph or, alternately, I could have installed a somewhat less powerful engine.

I haven't yet mentioned that this new boat fits our trailer perfectly, much better than the previous boat.  We trailed it 400+ miles to the lake; other than a decrease in acceleration, you couldn't notice that we were towing.  Although I can't find anything design-wise to improve on this boat, I am always evaluating what could be made better/ more esthetically pleasing on a next boat.  This is a 12-degree deadrise hull; I wonder what a 14-degree deadrise would do to performance?  I have an idea for a more modern-looking runabout which I hope to publish here in the near future.  I already have all the offsets and need to make up some drawings.  Then perhaps construct a model.



    

Sunday, May 25, 2014

What a day!

Having been busy/out-of-town the past few weeks (a trip to the Galapagos islands), this week was finally the chance to take the new boat out.  I picked a nearby (50 miles away) small reservoir knowing that this was a test run with possible complications.  The boat performed well; however, there are still adjustments to be made.  In a few spots at the transom, the red bottom paint came off.  I don't expect it to be difficult to repair; probably just a light sanding and thorough cleaning to improve adhesion.  The engine RPM topped out at 4200 which is below the recommended range of 4500-5500.  I was using a 17" pitch propeller and will need to switch to a 15" or 13", both of which I have on hand.  The indicated speed was 35+ mph due to the speedometer only reading to 35 mph.  I need to decide if I should replace the speedometer.  We had three people and 8 gallons of gas on board with the bimini top up.  The boat accelerates quickly with very moderate bow rise and vision is good from the driver's seat.

I want to view and photograph the boat at speed, but we will need a second boat for that.  On this lake the shore areas are "No Wake Zones".  The reason for the "What a day!" label for this entry is because when we arrived home from the lake, and I was putting away the boat, I developed some stomach discomfort which quickly worsened into acute appendicitis.  We went to the emergency room, and within a few hours my appendix was removed.  Now no strenuous exercise for the next six weeks.

View photo 3.JPG in slide show

Wednesday, March 26, 2014

The new boat looks complete.

Finally, the windshield is completed.  My wife encouraged me to have a metal windshield frame, but now that it is done, she says that the wood looks better than a metal frame.  But she thinks that it should have been taller.  I considered the height, angle, and fore-aft placement of the windshield when designing it; both from an esthetic and functional aspect.  Unless you make the windshield quite tall, the upper edge of the frame is in your field of vision.  Tall would have not fit the esthetic I desired; most of the time I expect to be viewing ahead over the top edge of the windshield.  I had an extra cushion made for the captain's seat to raise the line-of-sight.

And the upholstery is completed.  The seats are separately removable, allowing access to the fuel tank under the front seats and access to the battery and storage behind the rear seats.  A person could do their own upholstery, but it is not an area I have any expertise in; so I contracted it out.  And the bimini top with full enclosure panels is complete as well as a travel cover.  Looking over the amount of detail in all those panels, the variety of materials required, and the expertise involved, I am glad to have it done professionally.  Bringing the boat home, I had to drive through a spring snow storm; the boat and cover were wet and dirty when I arrived at our garage.

The boat is still not done, but we are in the home stretch.  I need to bundle and strap the control leads, electrical wiring, and fuel lines in place.  There is one slight scratch in the paint to touch up.  I need to get the boat inspected by the State of Colorado to get a Hull Identification Number (HIN) for licensing.  Then we will be on the water.  Here in Colorado, the scenic mountain lakes aren't warm enough for boating until June.  We may end up towing the boat to lower altitudes for a longer boating season.



       

Saturday, March 01, 2014

Why I use rosin paper


I recently read an article concerning conversion of developable surfaces into flat sheet patterns.  In previous posts, I really haven't discussed how to do that using a mathematical approach.  It can be done; I used this approach when I built a 20 1/2-foot sharpie design many years ago.  The only reason I haven't expanded on the subject is that, once I have a hull framework constructed, it is easier to simply make a stiff rosin paper pattern by laying a roll of paper over the framework and tracing the edges.  But, for those who do not want to construct a full hull framework, being able to go directly to laying out patterns for sheathing may be worthwhile.

The method utilizes what may be best called external triangulation.  It is external because we are not calculating distances just between points within the design surface but instead are using our conic apex, located at some distance from the surface borders, as a reference point for many measurements.  Using the coordinates of the apex in conic development and the coordinates of consecutive points along the chine of the hull, we can calculate the length of radiating (ruling) lines emanating from that apex.  The chine of the hull is created using a mathematical equation; thus, by integrating this equation (the power of calculus) we can find an equation [it is a long but standard equation] to calculate the distance along the curve between any two designated points on the chine.  Those points along the chine provide the third distance in creating a series of triangles which, when plotted in sequence, will give us the shape of the developed surface.

However, part of the chine curvature may be contained within the outline of the surface itself; thus, the sequential points of the chine are best first plotted along a fair batten which is then laid in place and connected to the ruling lines from the apex.  For parallel projections, instead of an apex, we would be plotting parallel ruling lines.  If you calculate the distance between two sets of coordinates in a developed surface NOT connected by a ruling (straight) line by using simply the formula square root of (x squared plus y squared plus z squared), the distance will be distorted by lack of consideration for the curvature present.

In conclusion, yes, I can create flat surface patterns for sheathing.  But is it really worth the effort when a roll of rosin paper will give me the same thing?   

Saturday, February 08, 2014

Pictures of boat windshield

The windshield was constructed in four separate sections.  Each section shape was calculated using the x-y-z coordinates available because the entire hull shape was created numerically before any construction began.  Junction angles between sections, and between the windshield and deck could also be pre-calculated.  Because some error can be anticipated in any human-constructed shape, the four sections of the windshield were then bonded together while positioned on the actual hull deck.


When finished, the windshield will be bonded to the deck and fastened with screws from underneath the hull decking.


I'm getting excited about what it will look like after the interior is upholstered (not by me).  The same people will also make a bimini top, full foul weather enclosure, and travel cover.  By the time I get it back, the weather will be warm enough to finish the windshield details for final installation.  I am guessing you have noticed the snow present in the background.

Winter progress

Sorry for the lack of recent posts; the winter weather and some logistical problems have slowed things down.  My previous boat has been transferred to a new owner and is now residing in Montana.  The new boat has been transferred to the trailer and fits it perfectly.  The new 75hp Evinrude E-Tec engine has been installed, and all the controls have been connected.  I still need to organize tubes & wires by wrapping and strapping them under the deck.  I had wanted a stainless-steel windshield frame, but no matter how exact and simple I made the proposed design, the metal fabrication shop still estimated the cost at $4000-5000 which just didn't fit my goal of producing a good boat at a moderate price.

I bought a plank of African mahogany for $68 and built my own windshield frame.  I have had the glass cut and fit for the frame.  The glass people said that they think the wood frame will look nicer than metal.  Nice to hear such comments.  The wood frame has been fabricated in four sections.  Although the four sections fit together well, I want to bond them together with epoxy while they are in place on the hull foredeck for a strong, accurate result.  The boat is now in our unheated garage with outside temperatures mainly below freezing.  The epoxy will require warmer temperatures.  It may be a while before the final assembly of the windshield takes place, but, in the meantime, I can clamp and screw the windshield in place well enough to have a boat cover fabricated.

The windshield frame was designed mathematically.  It is a system which works incredibly well for me.  Everything is done in an X,Y, Z coordinate system.  After building two mock-ups, I elected to build a windshield 12.5 inches high which slants aft 10.5 inches from bottom to top and is 53.5 inches wide with rectangular sections.  Knowing also the offsets of the deck curvature, I was able to calculate the angle of intersection of the two front panels, 16.54 degrees, the angle of intersection of the front panels to the deck, 42.48 degrees, and the angle of intersection of the side panels to the deck, 9.09 degrees.  All the linear dimensions were calculated to similar accuracy.  When cut to those angles in the shop before assembly, the panels fit together well.  I can't imagine how much more difficult it must be to use trial-and-error, cut-to-fit methods.

We were in Bocas Del Toro, Panama recently and I brought back some pictures of abandoned, hollowed-out-log cayucos and the pangas which have replaced them to a great degree.  When we lived there 30+ years ago, our local maid said she wouldn't trust a boat which was made with adhesives instead of from a single tree trunk.  Times have changed.



            

Friday, November 29, 2013

A Voyage to Remember



                                                       A Voyage to Remember, Miami to Panama

When we were snorkeling in Maui recently, talk turned to snorkeling in Panama and our life there.  I recalled an exciting trip I took bringing a boat to Panama from Florida.  Our friends suggested that the trip was interesting and unique enough that I should record it on paper.  So my attempt follows.

When I was on active duty in the US Navy, 1966-68, I initially attended navigation school in San Diego.  The subject was interesting enough to me that I graduated #1 in my class, and continued to study available nautical references on board the two ships on which I served.  Spending many hours per day on the ship’s bridge deck for months at a time (crossing the Pacific twice, navigating the Mekong Delta, patrolling the Vietnam coast and Gulf of Tonkin, and cruising to Japan for maintenance) provided plenty of time for such review.  I became an enlisted supervisor in the navigation department.  Later, in 1976 while visiting Hawaii, I picked up a reference on Polynesian navigation techniques (We, the Navigators) to help understand how the early voyagers were able to find their way in the ocean’s vastness.  In late 1980, our family was living in Panama.  My assistant and her husband were buying a used 46’ trawler (single diesel engine) in Florida which they intended to bring to Panama to live and cruise on.  They asked me if I would act as navigator for the trip from Miami to Colon, Panama.

They offered to pay for my flight to Miami, which I declined.  If I were to do this, I wanted it to be from a sense of friendship rather than any monetary obligation.  I provided a list of the different nautical charts, references, and instruments which would be necessary for such a trip.  My assistant’s husband, Charles, was a retired US Navy diver who now worked for the Panama Canal Company.  He was to fly to Miami and spend one week examining and preparing the boat, including obtaining the necessary navigation supplies, before we left port.  He was one very tough individual and totally fearless.  He recruited a third crew member, Bill, who I hadn’t previously met but who seemed like a solid character.  It would be just the three of us on a quick voyage back to Panama.

I had talked to one of my patients, then employed as a canal pilot, who had previously been a Caribbean charter captain.  He gave me a route recommendation, which appeared reasonable, and loaned me his sextant.  I flew to Miami on a Saturday in early December, took a taxi to the yacht basin, and was prepared to leave harbor the following morning.  Upon arrival, I asked about the navigational charts and references and was stunned to discover that none of the publications I requested had been purchased because it was now December 6 and the contained data was only good through the end of the year.  They were deemed too expensive to obtain for such a short period of use, but, without the sight reduction tables, the sextant was useless.  Also, only one chart had been obtained.  It was an overall chart showing Miami toward the top edge and Panama at the bottom edge.  With such a large area to cover, the chart lacked any detail of depths and features of the various coastlines.  Additionally, the trawler had only been maneuvered on various headings once to check the accuracy and deviation of the compass.  The boat was equipped with a radar set, but the range was only a few miles.  LORAN coverage of the southern Caribbean was lacking at that time, and GPS had not yet been invented.  This was shaping up to be quite a challenge, and I was glad I had some knowledge of navigation without dependency on instruments.

Checking on supplies, the trawler was almost empty with very little on board for ballast, just some groceries, a few tools, and our suitcases.  Our only refrigeration was a single large ice chest.  On Sunday morning, we set out on our adventure.  The first leg was to follow the coast of Florida southwest to Key West, then head straight south to the coast of Cuba.  The hurricane season officially ends November 30; we were now in December but encountering strong winds.  As we headed south from Key West we were headed into nighttime, crossing the Gulf Stream with a strong current from the west opposing strong wind from the southeast which made for large, steep waves against our under-ballasted hull.  Forty-six feet may sound like a large vessel, but, on the open ocean, it is a tiny presence.  The strong wind created a surface haze of spray allowing very limited visibility.  Instead of an enclosed bunk, I had a bed to (try to) sleep in at night.  I tried to hold onto the bed, wrapping my arms and legs around the mattress while resting, but was completely thrown out of the bed once by the lurching hull.  Once I heard a scream from Bill, “We are going over!” as the boat slid sideways down the face of a wave with the rudder seemingly useless.  Fortunately, before we were rolled in a trough by the next wave, the rudder finally caught hold and the bow came around sufficiently to face it.  When it was my time to go on watch, I filled a paper cup with water and held it in my hand.  If I were to fall asleep, I would drop the cup, and it would be my alarm.  It worked.  Everyone needed what rest they could get; there was no asking someone else to take part of your watch.

We were glad to see the morning, but were now presented with a new problem.  Our large chart showed no detail of the Cuban coast.  As we continued south, we wanted to approach the coast as a navigational reference but not get so close that Cuban gunboats would escort us into port.  The solution was Polynesian navigation using cloud formations.  Distinctive cloud formations are found over islands.  Although we never actually saw Cuba, we followed its cloud formations west along the coast while staying offshore.

As evening set in, we were ready to jump off from the west end of Cuba toward Mexico.  It is an easy dead reckoning exercise (hard to miss Mexico) but it also meant re-crossing the Gulf Stream as it flows north.  We subtracted a few degrees from our compass course to allow for the current and set off into the night.  The next morning we sighted Isla Mujeres and pulled into port for refueling.  That afternoon we headed back out to sea with Cozumel to starboard and the Swan islands as our next intended waypoint.  Heading southeast, we encountered rising wind and waves from the northeast.  As the hull angled into the face of each oncoming wave, it was obvious that the "thump, thump, thump" sound of the big single diesel slowed significantly.  The engine was losing power.  Upon inspection it was discovered that sludge, from the diesel fuel we just received, was clogging the fuel filter.  The engine was being starved for fuel.  To clean the fuel filter we needed to stop the engine.  Then it was discovered that the alternator, used to charge the batteries, was not working.  The batteries were very low on electrical charge.  If we stopped the engine, it was doubtful that the batteries held enough electrical current to restart it.  It was time to change course and our plan.

We turned to run with the wind toward the southwest for a smoother ride and slowed boat speed slightly to match the speed of the waves and reduce engine load.  We shut off almost all electrical equipment to save the batteries, and Charles went down in the belly of the boat, holding electrical wires by hand on the batteries until the battery acid started to bubble, in an attempt to recharge the batteries.  Through the night we steered manually, using a flashlight to read the compass, and no running lights.  When it was my turn to lie in bed, I wondered what the future would hold if that engine stopped; what bit of shoreline or reef would the drifting hull crunch coral on?  Fortunately, the engine kept "thumping".

The next morning we could see some of the Bay Islands near the coast of Honduras in the distance off to port.  The wind and waves were still strong.  Charles thought that the downwind island was Roatan and suggested we aim for it.  I pointed out that if he was wrong, we would be unable to work our way back to any of the islands further upwind.  So we angled our course to port and headed for the nearest island.  It turned out to be Roatan.  The old wooden wharf was on the lee side of the island, allowing us to get out of the wind and motor quietly up to the dock (where I was to receive quite a surprise).  I was standing on the bow, dock line in hand, peering intently at the dock’s shabby state with substantial holes punched in its gray, wooden-planked surface.  I wanted to make sure that when I leaped to the dock to tie up, I didn’t put a foot through one of those holes.  Suddenly, a young black man came out on the dock, and his first words, in clear English were, “Hey, Did you hear that John Lennon was shot and killed?”  Here I thought I was in some remote place far from the beaten path, and, instead, I was getting the latest news in my own language!  Mainland Honduras inhabitants speak Spanish, but on the Islands, they speak English due to previous British influence.  In Roatan we were able to get an alternator from a wrecked yacht which Charles and Bill then installed.  The fuel filter was also cleaned, and we had a good meal and rest at anchor before leaving the next morning.

We cruised east along the Honduran coast taking turns on watch.  The following morning when I came up on deck, I was immediately concerned.  I looked down at the ocean and saw churned brown water.  I yelled to Charles that we were in too shallow of water and were in danger of running aground.  He replied that the radar range he had taken indicated that we were a sufficient distance from the beach.  I pointed out that the radar was not being reflected from the gently sloping sand beach, but from a line of tall palm trees several hundred yards behind the beach.  We immediately turned out to sea until we were in clear blue water.  Later that day we passed Cabo Gracias a Dios which held a lesson for us.  The Cabo is the outlet of a major river marking the border between Honduras and Nicaragua.  A submerged tongue of silt, an invisible delta, stretches miles out to sea at this location.  You can be miles from the coast and still run aground in very shallow water.  Several ship wrecks stood as evidence.

From here we headed south and slightly east out on the open seas, away from the Nicaraguan coast, with the next intended waypoint being the island of San Andres.  The weather was now good, and we were able to troll and catch fish for dinner.  Our ice chest no longer had any ice or fresh food so the fish was appreciated.  We were again dead reckoning [basically following a compass course allowing for expected currents and other influences] for navigation.  We never actually saw San Andres but were again aided by Polynesian navigation using wave patterns.  Ocean waves obey the same principles of physics as other types of waves.  When ocean waves or swells reach an island, the lines of wave crests are slowed causing a diffraction or bent angle toward the shallow water; on the lee side of the island you will see a cross-hatched pattern of waves from being diffracted around both ends of the island.  This phenomenon extends for miles downstream from the land.  Our intended path was planned so that if we didn’t actually sight the island we would pass on its lee side, and that is what happened.  Watching the wave pattern closely, you could see the oncoming waves transition to a cross-hatched pattern as we passed on the lee side of San Andres and then resume their undisturbed linear pattern as we came back into the clear.  Observing such a pattern, we knew where we were.

For ancient navigators on the Pacific Ocean, you can understand how important it was for them to understand natural phenomena to expand the “target size” of the islands they were seeking.  From an ocean liner, at some height above the water, the horizon is distant, but from the deck of a small boat the visible horizon may be only 2-3 miles away.  When I was in the US Navy and we were approaching Midway Island in the Pacific, we had the advantage of a huge radar array atop a tall mast and still only detected the low-lying island from about 15 miles away.  The Polynesian navigators understood clouds and waves and had memorized the passing star groupings in an ever-revolving sky with its seasonal variations so that the stars provided a map to follow.  Additionally, they knew the seasonal direction of swells (separate from waves), the patterns of bird flights, as well as other more subtle influences, and had memorized the legends of previous voyages.  Think of it as their equivalent of an advanced college degree.  I had only learned a few of their “beginner” topics.
 
On a calm evening at sea, we continued southeast toward the coast of Panama.  I miss-judged slightly in estimating the coastal currents; when we sighted the Panama coast the next day we were 10-20 miles east of the Colon harbor entrance.  But it was a familiar coast, where my wife and I had spent numerous snorkeling and sailing trips, and only a short cruise to correct our position.  During the trip, each of us had been emotionally self-contained.  We simply focused on the mechanics of getting through each day.  No long conversations; no sharing of concerns.  I still didn't know Bill's background, and he didn't know mine.  However, at the entrance to the harbor Bill turned to me and said, “If I were to meet someone who wanted to do the same trip with me as crew, I would charge them at least $2,000.”  [Remember, these were 1980 dollars] I turned to him and said, “Funny, I was thinking the same thing, and I came up with the exact same price.”


Months later, my wife Dawn and I would cruise with Charles and Jean to the San Blas Islands where we did run aground with their trawler, but that is another story.

Sunday, November 17, 2013

Instrument Panel

I have been in the process of transferring gauges and switches from the previous hull to the new boat.  I have also added some new instrumentation- an electric horn, and a fuel gauge.  I ordered an in-panel fuel gauge of the same style and manufacturer as the two existing gauges.  While waiting for the new gauge to arrive, I went ahead and cut out holes in the instrument panel for all three gauges.  You know what they say about assuming; when the gauge arrived, it was a smaller diameter than the other two gauges. Thus, I was left with the task of making a larger hole, 3 1/2" dia., into a smaller 2 1/4" diameter hole.  I had to create a 1" thick wooden doughnut to reduce the hole size.  Done, but time consuming.

At this point I am re-thinking the windshield design, something lower and less upright; also see if I can make it simpler to lower the cost.  In the near future, the 50hp engine will be removed from the previous hull; then that hull will be removed from the trailer so that the new boat can be placed on the trailer and the new 75hp engine installed.  Some logistics involved here. I also had to build an engine stand for the 250 pound 50 hp ETEC engine to be stored on after it is off the transom.  Fortunately, I had enough spare lumber in the shop to complete a sturdy stand.
 

Friday, October 11, 2013

Now for the accessories

The basic hull is now almost finished; just need to add some varnish on a few trim pieces.  The deck hardware is installed.  Next I want to install a fixed fuel tank under the front seat.  I had originally planned to put the fuel tank on the hull midline, but have been unable to find a fill hose either flexible enough or with the proper curve to extend from the tank, under the seat, then up the cockpit side to a stainless steel fuel fill cap to be mounted in the side deck.  So I will shift the tank about 10" to the port (left) side to provide a short, straight path for the fill hose.  Then I will offset the battery installation to the other side of the hull to maintain balance.  From here on it will be a process of adding items: bilge pump, gauges, steering, throttle control, engine, windshield frame, upholstered seats, flotation foam, and bimini top.  But, for some of these items, I need to get the hull out of the shop and onto a trailer.  The clearance to get the hull out of the shop door is about 1/2".  I plan to add a chrome strip along the sheer line, but it will add about 3/4" to the hull beam, so that will also wait until the hull is out of the shop.  Another associated task will be to move the previous boat off the trailer.  Anyone have a trailer I can use temporarily?

A new 75 HP Evinrude outboard has been ordered, and I have arranged for a nearby authorized Evinrude technician to install it.  I shopped across the country on the internet until I found a "deal", saving at least

$2000 below what it would cost to simply buy locally.  Of course, Colorado is a backwater to all things nautical, so such efforts may not be necessary in more lake & ocean blessed parts of the country.  It is all part of the fun of building your own boat.

Monday, July 29, 2013

Sample Developable Design calculations

In 2008 I wrote a short paper on a mathematical method of developable hull design (which is included in this blog, see entry of Dec. 2008).  I tried to keep it short and discuss only general principles, but some subjects are difficult to understand without providing examples.  Without any examples, I don't think it was very meaningful for most readers.  Recently the subject came up again, concerning the difficulty of developable design and the paucity of explanatory material.  Last night, I wrote a short paper concerning a stepwise approach and actual sample calculations involved in creating a hull shape.  The numbers used are from the runabout building in my shop currently.  The paper is not a comprehensive "how to" but hopefully will make the subject more easily understandable.



Sample computations for Developable Design


To illustrate the generation of many exact points along the chine curve, the following is a list of some coordinates of the chine at 7” intervals for the anterior chine of the hull I am now building:  (0, 0, 24.48), (7, 3.2, 22.56), (14, 6.3, 20.7), (21 ,9.2, 18.96), (28, 11.9, 17.34), (35, 14.4, 15.84), (42, 16.7, 14.46) ,.…. until (119, 28.8, 7.2).  This series is generated from the parabolic curve Y = 28.8- (119- X)squared / 490 and also Z = 0.6(28.8-Y) + 7.2 and is valid for values of X between 7 and 119. 

Where did these equations come from?  I want a boat about 6’ by 18’, so I picked a length of about half that which I could evenly divide into 16 segments [more segments = more accuracy]; 16x7 or 112” will suffice, next add a short straight 7” segment onto that.  Have you ever noticed that when you bend a batten, the curve does not extend all the way to the end of the board?  At the batten end there is no fulcrum to apply torque.  Thus, last few inches have no bend unless confined along its entire length.  So I always add a straight segment at the end of every curve.  A 6’ beam gives a 36” half beam; minus some width for flare of the topsides (4”) and an allowance for a chine flat (3.2” at maximum point) and you end up with 28.8” chine beam which is 25.6” of camber in the 112” length and 3.2” of offset along the 7” straight end segment.

To create the forward keel projection, I most frequently use a parallel projection.  A conic projection, with the apex of the cone forward, will create sharp curvatures in that area.  It may be what you want, but it will also be hard to plank.  A conic apex amidships will give a mild curve at the keel, if that is what is desired.  The parallel projection has a controllable curvature and is easy to calculate.  We already have defined a 28.8” chine beam, and picked a 7.2” deadrise to go with it [based on estimated displacement].  So deciding on the slope for this parallel projection from chine to keel only involves selecting an X intercept from the maximum chine point (119, 28.8, 7.2).  The further forward we select this point, the more pronounced will be the forefoot of the keel with sharper curvature.  I chose a point 52.5” forward of maximum chine beam.  52.5/7.5 = 7; 28.8/7.5 = 3.84; 7.2/7.5 = 0.96; thus we have our slope, X: Y: Z=7: 3.84: 0.96 which coincides with the 7” segment intervals.

Now all anterior keel intercepts can be calculated to define the keel.  At the keel, Y=0, and we solve for X and Z.  X@keel= X@chine- (7/3.84)Y@chine and Z@keel= Z@chine– (0.96/3.84)Y@chine. Aft of the point X=119”, the keel is straight and Y=0 & Z=0 for the keel.  After finding the shape of the keel, we next move on to the shape of the transverse frames below the chine.  To calculate transverse frame shapes below the chine, the same slope or ratio is used.  We set X = 14, 28, 42, etc., or whatever other frame locations desired, and solve for Y and Z.  For every 7” forward we project a chine coordinate, the Y dimension will decrease by 3.84” and the Z dimension will decrease by 0.96”.  Simple math creates the entire shape of each frame.  Just connect the dots.

Creating topsides with some flare to the bow, transitioning into a tumblehome stern, seems to be best accomplished with a conic projection forward, linked to another conic apex further aft to create the transition, then a parallel projection extending aft to finish the tumblehome contour.  Conic projections involve finding a third point on a line give two defined points.  Rather than discuss an entire design, I will list selected apices and show sample calculations.

The apex of the first cone was selected at X, Y, Z = (56, 39, 70.2).  This will give a bow angle which matches the forefoot of the keel and provide moderate flare to the topsides not to exceed a 6’ total beam.  A sample calculation would be to calculate the Y and Z intercepts at the frame location X = 98 for a line between the apex and the chine coordinates (119, 31.9, 7.2).  The calculation is Y = 39– (98- 56) (39– 31.9)/ (119– 56) = 34.27 and Z = 70.2– (98– 56) (70.2– 7.2)/ (119- 56)= 28.2.  The relation is that the change in any one coordinate of a point on a line is proportional to the change in any other coordinate.  Since we choose our X intervals, we can then find Y and Z.

When calculations are complete for X between 0 and 126, we select a second apex (91, 35.5, 38.7) which lies on the ruling line, halfway between the first apex and the point of maximum chine beam (to the outside of the chine flat) which is (126, 32, 7.2).  This new apex is then used to calculate points aft to the chine location (189, 32, 7.2).  From there a parallel projection is used with the slope 7: 0.25: 2.25 and defined points every 7” along an extended chine equation to X= 294.  Although the actual chine ends at X= 213.5, the extended portion will determine the shape of the tumblehome at the stern when projected forward.  As more curvature is included in this extended curve, the tumblehome will also increase.

The entire shape is not yet designed, but sequence and type of calculations needed should be understandable.  The results, when finished, are full-size measurements in three dimensions with fair curves and excellent accuracy using simple tools.  Enough offsets are generated that all you have to do is connect the conveniently-spaced dots.