(Updated 9-25-2020)
--Final Sea Trials, September 2021
Since our first sea trials in July, we've completed a 2-page list of upgrades. Most were minor, such as rigging tweaks, while others were more major like installing portholes, the electrical system, AIS, comfortable deck seating, etc. With the list completed, we headed back to the Oregon coast in mid-September for ocean testing. We spent two days and a night offshore, testing the self steering, a novel drogue system, a new stove, AIS, etc.
We were quite pleased with the results and based on our experience so far, she's shaping up to be a good voyaging boat for warm waters. I already knew, having voyaged on a small catamaran before, that the motion at sea would be more comfortable than even a significantly larger monohull. For Pearl it was a new and pleasant discovery.
We find the unusual 4-masted rig very easy to handle, although the inspiration for the rig wasn't easy handling, but its potential for self steering. That appears to be a great success, as noted below.
As was our experience during the first round of sea trials, the boat garners a lot of attention and we enjoyed answering lots of questions from curious dock walkers.
Sailing and general observations:
While we'd have preferred stronger winds for testing, conditions remained consistently light, around 6-10 knots on both days and through the night. As we headed out to jetties to sea, frequent wakes from high speed sport fishing boats and large commercial fishing boats provided at least an initial test of the cross beam to hull lashings. We watched closely and detected zero movement, even when the boat bounced around considerably in large wakes. We also noted that when meeting wakes from multiple boats in succession, she had little tendency to pitch. This is probably due at least in part to the relatively low center of gravity of the rig.
As in our first sea trails in July, we found the rig very easy to handle, which is no surprise given that even the mainsails aren't much larger than dinghy size and all sails can be handled from the security of the central platform. Another feature we really like is that we can easily step the masts by hand, without any outside help. I expect we could even do it at sea, should it ever be necessary for repairs or other reasons, provided conditions were moderate and we were lying to a drogue with the boat perpendicular to seas.
On any course between a beam reach and downwind, we were generally sailing around 3-1/2 to 4 knots in about 6-8 knots of wind. We were pleased to see that on a beam reach there was little leeway, despite the lack of any sort of keel or other leeway prevention, aside from the hulls themselves. One concern we had was blanketing of the leeward sails on a beam reach or close hauled, but found that by sheeting the windward sails looser and the leeward tighter, it wasn't much of an issue. Given that she moves well in light airs under full sail, as the wind gets up we also have the option of eliminating blanketing entirely when close hauled or on a beam reach by using only the two windward sails or the two leeward sails. With this many sails, there's a lot of learning left to do.
As we expected, her weak point is to windward, mostly due to the flat junk sails. Winds were also light, which didn't help. If our intended use was for coast-wise sailing, we'd modify the sails to be cambered. As compared with flat junk sails like ours, cambered junk sails considerably improve windward ability. We'd probably also install a more efficient method of leeway prevention to improve progress to windward and make coming about easier. Given that our intended use will be primarily trade wind voyaging however, we don't feel that either cambered sails or more efficient leeway prevention is warranted, but it's nice to know that either could be retrofitted.
Self Steering:
Minimus II has two modes of self steering, both of which exceeded our expectations. Before describing them though, a couple contributing factors should be noted. One is that she has two long, narrow hulls that track exceptionally well. The other is that her 4-masted rig allows unusual flexibility in balancing her sail plan to make her very light on the tiller. Also, in larger seas we wouldn't expect her to hold course quite as impressively. That said, here's a description of the two modes and how they performed:
One we call the 'delta' mode, which is primarily for downwind sailing. It involves simply letting out both mainsails on opposite sides until they're in a delta configuration, each angled about 45 degrees downwind. In use, we brought the boat onto course, made fast the mainsheets and locked the tiller bar. In that configuration, she held to within about 5 degrees either side of the course for as long as we cared to let her go. An unexpected surprise was she would self steer in this configuration up to about 45 degrees to either side of dead downwind. All we had to do was adjust the tiller bar to the new course and lock it in place. Anywhere in that 90 degree arc, she would stay within 5 degrees of her course indefinitely. While in this mode, we decided not to push it beyond a broad reach as jibing becomes a possibility.
Here's a video (unedited) showing her in this mode:
Self steering video #1 (delta mode)
The other mode we call 'mizzen-as-windvane'. It allows her to self steer between close hauled and a broad reach. It would probably work downwind as well, though we prefer to use the delta mode for that as it's a bit easier to set up. Mizzen as windvane is somewhat more complicated to describe, though still quite simple as compared with normal self steering gear. The basic concept is that the windward mizzen sail acts as a very large wind vane, providing course corrections through two steering lines from the mizzen boom through blocks to the tiller bar. This mode also kept her to within about 5 degrees either side of the course.
The mizzen as windvane mode is particularly interesting in that it might be retrofitted to monohulls by the addition of a small mizzen sail. The mizzen could also serve a dual purpose in preventing sailing at anchor.
The required equipment consists of a cross bar about 3 feet (1 meter) long with a block at either end. The cross bar can be locked to the windward mizzen mast, just below the sail. Two more blocks are fastened to the deck, on the outboard edge of each hull, in line with the tiller bar. Two steering lines and a couple bits of surgical tubing complete the kit.
In use, let's say we're on a starboard beam reach. One or both mains are driving the boat, as is the leeward mizzen, which is also used to balance the rig. The windward mizzen becomes a steering sail. Its sheet is slacked and the sail allowed to feather into the wind. The cross bar is then set perpendicular to the sail and locked to the mizzen mast.
A steering line is fastened on each side of the boom, near the end of the boom. The line on the forward side of the boom leads to the block on the forward end of the cross bar and then down to the block on the starboard deck. From there it leads to the center of the tiller bar. The corresponding steering line on the aft side of the boom leads to the block on the aft end of the cross bar and then to the block on the port deck. From there it leads to the center of the tiller bar.
As the boat gets off course, the sail remains feathered into the wind and the steering lines remain static, relative to the sail. Effectively, the boat is rotating under the steering sail and as it does, the steering lines cause the tiller bar to move in a course-correcting direction. A minor refinement is a short length of surgical tubing where each steering line connects to the tiller bar. The purpose of the surgical tubing is to overcome a minor differential in the effective length of the steering lines as the boat gets off course.
Given that this description is probably about as clear as mud, here are several videos (unedited) explaining it in more detail:
Self steering video #2 (mizzen-as-windvane mode)
Self steering video #3 (mizzen-as-windvane mode)
Self steering video #4 (mizzen-as-windvane mode)
A Novel Series Drogue:
This is a take-off on the basic principle of the series drogue in which the spacing of drogue elements (fabric cones) along a rode insures that a sufficient number of cones will provide adequate resistance at all times. On our original Minimus, a Cape Dory 25, we made a series drogue using fabric cones. The drogue, with its 250 foot (75 meter) long rode, was heavy and took up a surprising amount of space.
Since weight is a more critical factor on a multihull, we've taken a considerably different tack for the drogue on Minimus II. Based on my previous experience, I consider a drogue to be an essential piece of gear on a voyaging multihull, especially a small one. Being easily driven, such a vessel will tend to surf as winds and seas build up. We're cruisers, not racers and have no desire to surf in mid-ocean. Putting out a drogue on a bridle from the sterns in such conditions slows the boat down and makes sailing much more relaxing. Also, as winds and waves become too much for safe sailing, we want the ability to set a drogue and rest while drifting dead downwind in reasonable comfort. I did this when sailing my previous catamaran, a 23 foot (7 meter) Wharram Hinemoa, from Mexico to Hawaii, and it was a revelation to know that there was a safe option when conditions required it.
Our current drogue design saves weight and space by using one of our 1/2" (12mm) braided nylon anchor rodes instead of a dedicated drogue rode. Each drogue element is made of 1/2" (12mm) thick by 12" (30 cm) square epoxy-coated marine plywood. A 4-part bridle on both sides of each element allows it to be fastened to the rode. We have 4 elements and can use whatever number the conditions require. The rode is marked at specified points so that a figure-8 loop (or alpine butterfly loop) can be quickly tied at the appropriate points to provide anchor loops for each drogue element. The two loops for each element are spaced such that the rode is slack where it passes around each element, but is taut between elements. The distance between each element is about 30 feet (9 meters). To help keep the elements submerged, at the aft end of the rode is 10 feet (3 meters) of 1/4 inch (6mm) chain. For additional weight if needed, we also have a small stuff sack partially filled with round gravel can be made fast to the end of the chain.
We expected the concept might fail due to the elements spinning and winding up the rode, or that the elements might veer back and forth, providing directionally unstable resistance. In our limited testing however, they did neither. When we attached one or two elements to the rode and pulled it behind a dinghy with a 2.5 hp outboard at full throttle, they remained steady, with no spinning or veering. We didn't have access to a load cell to measure the tension, but with two elements the rode was very difficult to hold onto.
 Center line is anchor rode used as drogue rode. Bridle lines on either side are fastened to the rode and to a chainplate on each stern. 4 plywood drogue elements can be seen in background along rode. |
 Drogue bridle is attached to rode with climbing sling rigged as prussic knot. Two carabiners join sling to bridle ends. Thanks to Drew Frye over at Practical Sailor for that idea. |
 Showing the last two drogue elements. Elements are spaced about 30 feet (10 meters) apart. |
 Last drogue element, showing chain which keeps the elements submerged. Elements are made from 1/2" (12mm) epoxy coated plywood 12" (30cm) square. |
 Closeup of plywood drogue element and bridle. Bridles are short enough that they won't become fouled around element even if tumbled in heavy seas. Element is fastened to loops in rode with a figure 8 knot. |
 Closeup showing black ribbons marking rode. These are lined up together and a figure 8 loop is tied in the rode to form 1 of 2 attachment points for each element. Two more black ribbons about 6 feet (2 meters) along the rode mark where the second loop is tied for that element. |
Stove:
On our original Minimus, we used a multi-fuel backpacking stove modified with a pot stabilizing system. We ran it on kerosene and primed it with alcohol. Although it was a safe stove and worked well, we decided to go a different route for Minimus II.
After a god bit of research we purchased a Gas One GS-800-P single burner stove that works on propane or butane. It's a low profile design and very stable. A concern with such stoves is that the fuel is heavier than air and leaks can gather gas in the hull and lead to explosions. I once saw this happen (gratefully from a safe distance) and it lifted the entire deck off a 45' (14 meter) motor cruiser. No one was aboard and no one hurt, but the boat was totaled. Normally, boats with marine propane or butane stoves have solenoids and thermocouples to help insure that gas doesn't accidentally flow into the boat.
Our new stove is a simpler and far less expensive alternative to marine stoves. In our experience so far, it's also potentially safer. It runs on either a 16 oz. propane or 8 oz. butane cartridge. We'll be using butane cartridges, because they can be quickly locked into the stove for use and can be removed almost instantly afterward. This allows the cartridges to be stored on deck in a dry bag between uses, so we never have butane inside the boat except when cooking. The stove has a piezo-electric igniter and the flame is easily adjustable. It's about the most convenient stove one could imagine. For $35 it's hard to beat. The one upgrade we'll make is to fasten it to the galley table and add some sort of pot retention device.
 Gas One dual fuel stove with butane canister |
 Gas One stove with butane canister inserted and locked |
 Gas One stove with canister cover closed, ready for cooking. Less than 10 seconds from inserting canister to cooking. |
AIS
On our original Minimus, we installed an AMEC Cypho-150 AIS receiver, which worked well. For Minimus II we're using a dAISY 2+ Dual Channel AIS receiver from Wegmatt. At $89 US, the dAISY 2+ is less than half the price of the Cypho and appears to have similar performance. Even better, it's designed to accept a wifi card ($10.00 on ebay) so for under $100 US, we have a wifi equipped AIS receiver. On our phones or tablets we use a chartplotter app such as Open CPN (for Android) or iNAVX (for iPhone or iPad). We prefer Open CPN for its greater functionality. Whichever device we're using though, it picks up the AIS signal even when we're in one hull and the AIS receiver is in the other hull.
Our AIS antenna is about 4 meters above water level and in offshore testing we were able to pick up targets, commercial fishing boats and tugboats mostly, at up to 15 miles. We expect that ships, due to their much higher antennas, would likely be picked up at around 20 miles.
Wegmatt (wegmatt.com) is a small company in Seattle, WA that manufactures marine electronics. We were impressed with the build quality and sturdy aluminum case of the Daisy2+ and even more so with the customer service. On a couple occasions when we had minor questions, we emailed the owner, Adrian Studer, and both times he responded within minutes.
 dAISY2+ AIS Receiver (with VHF cable disconnected). |
 Wifi card for dAISY 2+ AIS Receiver is the small card to the left of the green NMEA connector. |
Miscellaneous photos:
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 Minimus II in Newport, Oregon |
 Minimus II in Newport, Oregon |
 Minimus II in Newport, Oregon |
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