S/V FROG'S LEAP.com
THE ARCH

How about an Arch for Solar Panels and Radar, Antennae, etc?

An arch is nice, but it is nicer if it looks good.

At the end of the first season in 2009, I came to realize that the radar post on the stern of the boat was poorly mounted. The base was made of mild steel welded onto the stainless tube and secured by rather small screws to the aluminum stern plate. The post was tied to the stern rail which served as the only support to keep it vertical. Disliking the prospect of falling overboard while relieving myself, and wanting for solar power, I started the design and construction of the Arch in 2011, completing it in 2012.

Refrigeration and watermakers, autopilots, are simply hungry for electricity. I am not a minimalist cruiser, preferring to follow the technology path. Frog’s Leap has a very valuable autopilot, GPS, Radar, SSB, VHF, a watermaker, a network, and industrial WiFi. Refrigeration, on the advice of the knowledgeable folks at Sea Frost (Cleave Horton) is much better off operated by electrical power while at anchor. No engine noise for the engine driven compressor. Electric reefer at anchor, supplemented by engine while underway motoring, is a good solution. Many boats are also switching to 115VAC systems. I can see the point to it: save copper, save weight. But Frog's Leap is a 12V boat. I have not met many who prefer to Haul Ice and it only works for short trips. So, Solar was a must, and the panels needed a home.

I quickly realized that an arch needs to be custom made. Wells Marine seemed capable and their price was allright. However, the complexity of shipping templates and hoping for the correct measurements was a receipe for many adjustments. You simply can't replace the convenience of having the fabrication next to the boat. My yard at Lockwood is very competent, had the advantage of being able to walk over to the boat. Wells was offering 0.089” wall tubing thickness and I was advised to use 0.063 by the yard. This made the arch weaker, but saved weight. I did not plan on hanging the dinghy on the arch, see the Davits project page for this. I designed the arch with the idea of using it for Radar, Solar, Antenna mounting, and for the fog signal/hailer speaker. I also planned to mount the industrial WiFi Client on it.

My design method was unconventional, in the absence of drawings for the boat. First, the Arch needed to be as much a part of the boat as the rest of the design. Looking at the arches mounted on various boats, I started analysing their look and wondered how anyone would design an upside down U with squarish corners and two parallel legs at a 45 degree angle, but these do exist. To avoid such offences to the eye, I started with a picture of the boat from astern and one from abeam. These would become the background of the design drawings and allow me to tweak the design to verify the appearance. After five or six iterations and sleeping on the idea a few nights between each revision, I felt the boat looked good with the substantial framework mounted on it. At a friend’s suggestion I added a bend so the arch would be vertical on the deck to mimic the aft pushpit. This approach not only helped with aesthetics, but also kept clearances to other systems in the stern quarter, which is a busy area with winches, runners, pushpit, backstay hydraulic pistons, and docking cleats.

The rest of the design was a series of measurements, building a template using wood, and checking for interferences, and of course tweaking the drawings accordingly. To match the deck angle, I build a two aciz swivel with aluminum bracket, which allowed exact replication of distance and landing pad angles relative to vertical datum. Next came calculations, since this was done on 2D drawings I had to calculate the length of the horizontal bars used to reinforce the structure. This was a useful refresher in 3D vector algebra.

The arch fabrication took a while. A couple of mandrel bends bends had to be sent out for forming, the rest of the bends were higher radii and could be doone in the yard. I since bought a tubing bendor for other projects. The fabricator (Ron) said I was quite close in the calculations and and he was able to touch up the lengths to match perfectly. The welding took a while, and the arch was lifted into the boat with the boom truck. Since the Arch is supposed to support my weight at close to 200 lbs, proper reinforcement of the deck was necessary. I had prepared the area, reinforcing the boat at the corners of the transom using ½ inch G10 and many layers of glass matt and stitched engineered laminate fabric. I used epoxy, which I prefer exclusively because of higher strength, adhesion, and flex/fatigue performance. The holes were made in the deck, and an aramid-buta-n pressure gasket was used as a mounting base. These gaskets (trade mark is Blue-Gard) do conform, but because they are used in joints for steam high pressure lines they are quite strong under the compression forces of the pads against the deck.
The arch was lowered using the boom truck, and held in place. The aft legs were then positioned barely touching the transom and the holes for the aft legs were drilled. Once everything was positioned, the deck pads were tack welded onto the arch and it was lifted back off the boat for the welding to be completed. Then, the arch was placed onto the boat and bolted down.

Once the arch was in place, the yard welded the stern pulpit to the arch. My design called for the lower tweens to match the height of the stern pulpit lower and upper rails, which worked out very well. The finish was to weld the arch to the prepped pulpit sections. This made for athwartship stability of the arch. The electrical panels work would then start. Solar panels have come a long way in the last ten years. I did a fair amount of research and came to a number of conclusions. The first was that China was dumping panels on the market and taking a shot and dominating the industry. Next, monocrystalline cells had increased in efficiency and were up to th 20% range. Polymer printed panels research showed great promise in 2012, with an efficiency of up to 40% achieved in the lab. Today, the winners are multilayer cells which help trap more photons, and numbers like 35% to 45% are likely to become the trend in commercial panels. There was a tremendous amount of research in printable nanoinks for solar panels, promising mass production through printing. Nano inks have been equated by some solar industry experts as “replacing the printing press with a bunch of Monks”. Nanoink Inc went bust eventually after a 150M investment when it became clear the technology was not scalable. May be more will come through and make it, certainly the idea of printing a panel should scale well. Crystalline cells had their set backs too, for example evergreen went bust in 2011 after having become the darling of Massachussets, so the market is still very dynamic

I zeroed in on Sanyo HIT panels: Made in the USA, though it is a Japanese company, and high quality packaging, five year warranty, with a ten year degradation spec of 10% in power generation. The panels are 48V, which has two advantages: Reduced wiring weight, and the use of an outback charger.

The charger feeds off 48 Volt and adjusts automatically to match the charge current to the supplied power. Instead of controlling the current from a voltage source, the DC to DC converter in the Outback charger (available from several off grid companies) takes the maximum power possible from the V-I curve of the solar panels, and transforms it to the correct voltage or current to the battery, depending on bulk vs float charge cycle status. It is a three step charger, therefore won't cook your batteries and the solar recharge does protect battery life by keeping cells operating close to full. . Adding a charger would seem like a drawback, but this is indeed an advantage in efficiency. In full sun., I get 30- 40 Amps from two large panels. I may add one more, or who knows- spray nano-inks when I redo the deck and turn the boat into a power plant! What is clear is that within ten years after installing the panels, I will want to replace them for higher power, more efficient panels of the same size. Efficiencies are likely to go up to aerospace levels, eventually.

The frame for the panels is made of 80/20 aluminum extrusions. This is a bolt together system, but I may replace it with welded square tubing some day. The aluminum It is very sturdy, easy to use, and comes in several cross sections and sizes. The anodizing has held up well at this time, it is year 4 already.

The construction of the Arch. The feet were held in place per the measured dimensions during the welding operation. The welder is very experienced, and I could not have done as good a job. Truly a nice piece of art. Thanks Ron and Lockwood Boat Works.

Here is a Drawing of the Stern. The same technique was used for the stern and abeam views. Picture of the boat, and the design was tweaked to provide the desired appearance. I recommend this approach for visualization of the design. It is very difficult to understand how a frame will interact with the lines of the boat. Notice the reinforcement ring inside the aft tube of the arch. This is a stiffener which works very effectively.

The design technique: Take a picture of the boat in the water. Use a 2D drawing program and lay the dimensions on one layer, the arch on another layer and whatever dudas you might wan tto add on yet other layers. The use of layers is important, not only for housekeeping, but it allows you to turn layers on and off in order to visualize the design. Structurally, the arch does not have to carry great weight if the dinghy is placed on davits. But with 0.063 tubing wall thickness in 1.5inch tube, it is plenty strong. The tweens (horizontal bars) are 1.25inch diameter tube.

The finished project. This picture is prior to the Davits construction

The Arch was a 2012 project.SInce (2015) the solar panels, and the Davits were addde. Also in 2015, the Solent inner forestay roller reefing and storm sail replaced the removable wire stay.. Now the bimini looks weird, so another project is again looming..
There is a also page on the davits construction coming soon.(link to be added)
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Final bolts and drilling. Notice the hook on the book truck block is well padded to protect boat rigging. At this point in the picture the arch is resting on deck and there is zero lift. Needless to say I was a little too busy to take pictures in the midst of the installation. The counter was ticking.

I am glad the Arch came out ok. I was afraid it would end up looking like this:

CREDITS:
Such a project would not have been possible without help from many great friends. For the Arch project: Sebastien Granier and Daisy Pelszynski

Bill Lockwood, who runs one of the best yard in New Jersey, and his crew of brothers, sisters, and employees. Simply they are super multitalented machine operators, welders, fiberglass experts, machinists, storekeepers, and office workers. A great crew, and they will bend over backwards for loyal customers. Never once did they let me down.

Mike Vinik for his help with supplies.