Monday, May 30, 2011

Thinking About Phil Bolger's MICRO - Part 2

A little while ago I wrote a preamble in response to a request from Dennis Marshall for comments about Phil Bolger's wonderful Micro design - see

Dennis' request went as follows: -
Dear Ross,
I hate to commandeer your blog with all my questions and comments. I do enjoy it immensely. I was wondering if you would be so kind as to comment on Bolger's Micro at some future date. I would be very interested in hearing about your experiences with her and your assessment of her abilities. That was the first boat plan I ever bought. And ten years later, she still intrigues me.

My feeling is that Micro was designed while Phil Bolger was at his peak. Some of my very favourite Phil Bolger designs (but not all) come from that period, and include Black Skimmer, Micro, Long Micro, Martha Jane, Sparkler, Scooner (a.k.a Light Schooner), Otter II, Manatee, Surf, Folding Schooner, Harbinger, Dovekie, Defender, Light Dory Type V, Light Dory Type VI, Victoria, Thomaston Galley, Fieldmouse, Lynx, Monhegan, Yarrow, Nahant, Hope, June Bug, Burgundy, Pico, Apogee and Birdwatcher - the list goes on and on, and I really don't know where to draw my personal line. Suffice to say that of all the designers I'm aware off, Phil Bolger has had the greatest influence on my thinking.

You may think it is a case of hero-worship, but I don't believe that is the case. It is just that Phil had such an open mind from a technical point-of-view that I am constantly discovering more thought gems. It is noteable that he said on a number of occasions that Ray Hunt was the designer who had the most influence on his own thinking, and that it was because of Ray Hunt's open mind....

To Micro... well, where do I start? From the bow, I guess.

    Integral boarding ladder which makes the boat go faster!
  • The first thing you notice is that Micro has a transom (or flat) bow with a couple of prominant holes. I believe that the reason for this is that Phil was attempting to match up the curve of the topside panels (in plan view) with the curve of the bottom panel (in profile view). If the bow was drawn out long enough to come to a point, the side panels would have been longer than two butted plywood sheets, and the heel of the stem would have been way up in the air adding weight and windage, but without any hydrodynamic improvement. So, he just cut the bow off at the length of two plywood sheets. The boat is faster and better handling as a result. Being a sharpie, she sails on her chine and doesn't need a sharp bow. The resulting flat bow transom has been turned into a superb boarding ladder - that is what the holes are for - and where do you push-off when leaving a ramp or a semi-submerged trailer? From the bow, of course! How many people have you seen struggling to get onto a boat through the pulpit? With Micro, it is simple, elegant, and (usually) graceful.
  • The self-draining, open bow well. This compartment is a superb amenity, and can be seen on many Phil Bolger sharpie designs. When standing in the well, one is well supported at hip height, so that working on the mast, halyards, or ground tackle is made into a two-handed affair - no need for the "one hand for the boat, and one hand for youself" routine
  • Well supported in the self-draining forward compartment
  • The Cat-Yawl rig allows the masts to be positioned at either end of the boat, meaning that the entire length of the boat is free for accomodations. A minor drawback is that the weight of the main mast is in the eyes of the boat, and therefore drugs her in a chop. But Micro quite full in the forward sections, and can stand the weight. I make my masts hollow, so weight is reduced. The mast step and partner arrangement is simple, reliable, and allows for easy stepping and lowering of the mast - all without the weight and complication of a tabernacle.
  • Micro's simple, rugged, and easy-to-use mast stepping arrangement
  • The cabin and cockpit are overlapped. The lower legs of a person on one of the bunks in the cabin are under the butt of a person sitting in the forward part of the cockpit. Therefore, crew-weight is concentrated in the middle of the boat, while still having a combined length of cockpit and cabin which is shorter than the sum of the two. Think about how quarter berths work, but the Micro solution to accomodation problems is even more elegant.
  • Micro's cockpit doesn't have a conventional foot-well. The cockpit is in fact a deck on which one sits, with a hatch in the middle through which you can hang your legs if weather permits. The hatch is on the centreline, so that even if she is on her beam's end, the capsised water-line is below the hatch opening. The hatch also gives access to the enormous cargo hold below the aft end of the cockpit. If there were a foot-well, this superb hold would not be possible. The hold can also be accessed from within the cabin.
  • Right aft, there is another open, self-draining well into which the mizzen mast, outboard mount, outboard fuel tanks, ground tackle etc all fit. In the event of the cockpit flat being pooped, all of the green water can instantly run into the aft well, and the majority will pour out of the large outboard opening in the transom in an instant. The remainder will flow out of the drain holes and the opening around the rudder post.
  • Drain holes visible just aft of the tie-down strap, and around the rudder post
  • The rudder is mounted on the aft end of the keel, and because the rudder post runs up into the self-draining stern well, there is no need to worry about sealing where the rudder post goes through the hull - ever!
Convenient motor mounting which also acts as a super-fast way of ridding the cockpit of water
  • The keel structure is hollow other than for the middle section in which the 412lb lead ballast casting is located. The remaining hollow sections are free-flooding to make use of the neutral buoyancy of the water filling, and to obviate the problems of swelling and contraction of large timber deadwood components. In addition, solid timber deadwood sections tend to float (which the water filling doesn't) resulting in a reduction in stability when heeled. So Micro's water and lead-filled keel is cheaper, easier to make, lighter, and provides more stability.

Just visible near the bow is one of the vent holes in the keel structure. The solid lead casting runs from approximately the first trailer roller to the third trailer roller.
  • There is a vent in the forward bulkhead, another one in the aft bulkhead, and a clever arrangement for venting under the companionway hatch. All of these are arranged to allow air in and out while keeping water outside the hull - even when partially capsised. Even with the boat totally closed up, she is well ventilated.

There are many, many other subtle details in the design of Micro, but I've written too much for one sitting. A careful study of hundreds of Phil Bolger designs will reveal many similar examples of the designer's genius. The great pity is that so many people see the simplicity of his more notorious designs without understanding the genius which produced them. As a result, the majority of the amateur-built PCB boats we see have been altered to a greater or lesser degree - usually without the builder or owner being aware of the design elements being violated along the way. What happens is that the crudities remain, but the genius is lost forever....


  1. Dennis has been unable to get the comment function to operate satisfactorily (I have problems with it myself), so I am posting his comment for him. RL

    Dear Ross,

    I have tried several times to post a comment on your blog, but I have been having some difficulty for reasons I do not fathom.

    I wanted to let you know how grateful I am of your analysis of Micro's "anatomy". Much that I studied in the plans has been made clear by your pics and description. This is especially true regarding the rudder bearings, which have been a puzzle to me for some time. I guess it comes in part from having only sailed center board/lee board/dagger board dinghy's and have never really looked at the way "keelers" attach their rudders.

    I know you are a busy man, but I am truly appreciative of the time you have taken to discuss this boat.

    Warmest Regards,

  2. its a nice boat Ross , but for me who live in norway , its werry dificult to get complit plans,if you have idi pleas healp me ore annyone aut ther ,my engelsk are not the best but hope you understand,i wich for complit plans for Bolger micro,best wich from trygve one

  3. Ross - Thanks for the great write-uo on the Micro. Your explanation of the subtle features really helps me to settle on building this design in the future.

  4. Ross,

    I love Micro design and was thinking about building it. I live in Rio de Janeiro where we have a beautiful protected bay to explore.
    About 60 nautical miles from here there is another big bay with hundreds of islands to visit and many safe small bays to anchor.
    The 60 nautical miles route from one place to the other is usually done in less than 20 hours on motor or sailing in light wind. But you can have bad luck and deal with a headwind of more than 20 knots (force 5 to 6).
    Do you think Micro is safe enough to keep beating this strong wind? There is no safe port between the 2 bays and is impossible to heave to without going aground.
    Thanks for your attention and for sharing your impressions with us.

    Renato Guimaraes

  5. "In addition, solid timber deadwood sections tend to float (which the water filling doesn't) resulting in a reduction in stability when heeled. So Micro's water and lead-filled keel is cheaper, easier to make, lighter, and provides more stability... There are many, many other subtle details in the design of Micro.." - RL above

    Ross, I much appreciate your appreciation of Micro. Well covered, well said. May I add an item for consideration on that Micro keel water filled volume and stability?

    The water fills and drains from the keel via a few relatively small diameter permanently open holes at high and low locations in the keel sides. In a beam ends knockdown or worse the keel is no longer immersed. The water in the keel is no longer neutrally buoyant, but, raised up above the surrounding water, the mass of the keel contained water becomes quite significant and very effectively located positive righting ballast. This is clever. Due to the limited drainage holes the water in the keel drains slow enough to provide that effective ballast for a significant time. That is clever too. On beam ends the keel is more or less horizontal, and the water must drain even slower through the holes on the low side only. More clever! The really clever thing about it though is that it is all done so simply, so passively, without any crew thought or action required:

    Launching off the trailer water enters the vertical keel;

    Later, as quickly as the Micro is winched back on the trailer the keel water drains out from the vertical;

    Knocked over, hardly any water leaks out from the inclined to horizontal keel before the weight of it helps right the boat quickly and easily.

    It's simple in practise, once pointed out it seems simple to do, but it is no easy thing to design, to so masterfully simplificate a boat design. Boats involve a whole mess of complicated things. Seemingly simple boats can be harder to design than quite complicated ones. Simplifying involves a lot of effort and design flair.

    "I love to simplify things," Bolger says of his work. `And I think this is a minority outlook. I think the majority impulse is to make things more complicated." - Nautical Quarterly 21, Spring 1983( )

    "Simple" is instanced 15 times (!) there in Joseph Gribbens' 1983 review of Bolger as Bolger is entering his fourth decade of independent design practice. At his career peak? A plateau? How about a long high rising ridge with more peaks ahead in the next three decades?