More Detail on the Micro Repair

My recent post http://rosslillistonewoodenboat.blogspot.com.au/2015/04/micro-repair.html about repairs to a Phil Bolger Micro generated quite a bit of interest, and the following comment from Dave is an example:-

Thanks for the blog post, Ross, but you left out the details on the very parts Id be most interested in seeing!

So if you do a future post on the nitty gritty details of truing up and patching the damage, Id be most interested in that. 

Well, after taking initial photos of the damage, I didn’t many more during the repair process, simply because of time pressure – but here is a brief look at some aspects of the job: -

Initial job was to do a rough paint removal around all of the damaged areas to get a clearer idea of the extent of the damage, and to remove components/timber which had been destroyed. It also allowed ventilation and thorough drying.

Initial job was to do a rough paint removal around all of the damaged areas to get a clearer idea of the extent of the damage, and to remove components/timber which had been destroyed. It also allowed ventilation and thorough drying.

A small puncture wound on the forward/starboard topsides on the outside, and

....the corresponding spot on the inside

Brutal removal of paint, damaged timber, and broken epoxy fillets 

Brutal removal of paint, damaged timber, and broken epoxy fillets

Paint removal from around the forward bulkhead on the interior of the cabin, where the floorboards had punched through.

Most of the work shown above was done using a heat-gun and a variety of sharp scrapers. The paint was all two-part epoxy primer/undercoat and two-part polyurethane topcoat (I know, because I built this particular boat myself fourteen years ago!) and removal was not ever going to be easy. However, the heat-gun and scraper combination is a good choice as long as you are very careful about never overheating the material and damaging epoxy adhesive and paint in locations which are not part of the repair. Other primary tools include chisels, 4" angle grinders, drills, sandpaper - and elbow grease!

Next stage was to carry out a more gentle sanding  using (in this case) a 5" random orbit sander, going down through the grits to about 120 or 180. On the internal areas, the job is more difficult to achieve, and I made heavy use of a Fein Multi-master detail sander and plain, simple sandpaper on a sanding block, or folded triple. Hard work!

See above comments

See above comments

I dont have many photos of the next stage, but it mainly involved pulling usable components back into position using a variety of improvised tools such as lengths of purpose-cut steel angle-iron with holes drilled at strategic locations, and also temporary through-bolts and backing pads. This work can be very satisfying if done properly, and with attention to detail. The key is to have an open mind, and to be prepared to be bold with your surgery.

Once I was happy that my bracing would all work, and that all interfering debris was removed from joints, I opened the whole lot up again, and even spread damaged components further apart (using wedges and chisels etc). With the components held apart, it was relatively easy to treat all surfaces with un-thickened epoxy resin and hardener in order to prime the mating and damaged joints using disposable bristle brushes. This is a very important step if you expect to achieve a good structural repair. With the work area well primed, it was then a matter of applying a rich mix of epoxy/hardener combined with the recommended structural glue/filleting powder additive.

With the structural epoxy  mix worked into all joining areas, I screwed, bolted, or clamped the repaired sections together, which is why the previous work dry-fitting the bracing and jigging was such an important step. Where appropriate, I applied structural epoxy fillets at the same time.

The above two photos show steel angle braces screwed into position over the epoxied repair. In the case of Micro I had the luxury of using straight sections of steel to hold things in place, but on more conventionally shaped boats the same thing can be done using shaped and bent timber splints. Ill show an example of this in an up-coming post on a Whitehall repair.

Interior shot of the repaired bow transom, topside planking, and forward bottom planking. This was taken while the initial epoxy work was still wet and ugly. This work was followed by additional cosmetic epoxy filling.

Exterior shot of the starboard, forward topsides repair taking place. The actual puncture damage is quite a small spot underneath the centre of the plywood pad.

Matching plywood pad on the inner surface of the topside panel. As you can see from the exterior shot above this one, I placed twelve screws through the hull and into the internal plywood pad and pulled them in tightly over the epoxied repair. Note that both pads have been covered in a film of plastic to prevent them being glued to the hull permanently. All of those screw holes had to be repaired later, but the repair turned out well. The plywood pads were large enough to take up the curve of the topside planking when screwed together.

Structural work complete, glass applied where required, fill and cosmetic work done, and the two-part epoxy primer/undercoat applied (the white paint - three or four coats)

Topcoat (two-part polyurethane) applied, with just some minor black line work to be done between the green topsides paint and the off-white bottom paint (that is my little step ladder relected in the paint by the way).

Because of a lack of photos, time and space, this has been a very brief overview of the job, but it may give you some inspiration. Unfortunately, I have no photos of the way I repaired the forward watertight bulkhead of the cabin - a job involving more steel angle bracing and numbers of temporary through-bolts, nuts and fender washers.  In a post in the not too distant future, Ill show the repair of a glued-lapstrake Whitehall tender which suffered very serious damage to her hull in an accident. Most people considered her a write-off, but we were able to give her a new life.

Just a word about repairing screw and bolt holes. Many people simply fill the holes with thickened epoxy and sand the surface smooth after curing. I do not do this because the "cylinder" of hard epoxy in the screw hole intersects the surface of the repair at 90 degrees, and is sure to result in a circular crack in the paint after cycles of expansion and contraction due to temperature changes over time.

My approach is to heavily chamfer the hole on the inside and outside surfaces using a wide countersink or by dishing-out the surface using a sander. Then I fill the hole and the chamfered areas - this gives much less of a stress-riser where the epoxy fill intersects with the surface. However, if the repaired holes are going to be covered with a layer of fabric set in epoxy, this step is not necessary.

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Micro Repair

Phil Bolgers Micro design is a favourite of mine, and of many other people around the world.

To the uninitiated, the boat looks somewhat like , well..., a box. The hull cross-section is, in fact, perfectly rectangular - something which leads many observers to underate the design and write it off as a crude and simple piece of work.

Well, Micro is a very simple boat to build, but only a genius - someone like Phil Bolger or Naval Architect C. Raymond Hunt - could design such a hull and make it work well (Phil Bolger was heavily influenced by C. Raymond Hunt, among others). It takes understanding to get the best from Micro and her free-standing cat-yawl rig, but if treated properly, she is an exceptionally good performer, while at the same time being cheap and quick to build, self-righting and self-bailing, roomy, and comfortable - all in a 15-1/2 x 6 x 18" package.

Cricket - a Micro which I built back in late 2001/early 2002.

In this photo you can see some of Micros unusual features - flat bottom, extreme rocker, and rectangular sections. Very few people could design such a boat and make her a success. Very few people understand why the hull and rig work so well.

Im not going to go into detail about the design aspects of the boat, but I will say that on one occasion I sailed her against a well-handled Navigator and an equally well-handled Penobscott 14, and even though I had two passengers, we beat both boats to windward, and pointed just as well. Now, the conditions were ideal for Micro, in that we were on a lake with about 10 knots of breeze and almost flat water, but her performance was superb, surprising me as much as anybody. It might have been different in a steep chop....

This particular Micro has been back to my various workshops on a number of occasions in order to have cockpit modifications made, and to have repairs carried out. Most recently, she came back to me after having been in collision (head-on) with a concrete floating walkway/wharf beside a boat ramp.

The damage was fairly localised around the bow transom and forward topsides, but Micro has a wonderful self-draining well, right between the bow transom and the forward bulkhead of the cabin, with a strong set of floorboards filling the space between the bow and the cabin bulkhead. The floorboards are at approximately the level of the painted boot-top (i.e. the division between the green and cream just above the waterline in the photo below).

My youngest boy, Steven, standing in the forward well back in 2002. He is standing on the forward well floorboards.

When Cricket hit the concrete walkway, the point of impact was head-on, almost exactly at the level of the floorboards. This not only damaged the bow transom, but also forced the floorboard panel back through the forward cabin bulkhead with great force. Micro is not a particularly light boat, carrying 195kg/412lbs of cast lead in her keel, weighing-in at around 500kg/1/2 a ton - so the damage was substantial.

Winch post pad covers most of the external damage. The paint is the original Hempel Polybest two-pack polyurethane which I applied in 2002! Notice how the plywood of the topside panels has de-laminated and split away from the bow transom framing. The damage is much worse than it appears.

Photograph of the inside of the forward well, looking towards the bow transom. The two large holes in the transom are the steps of the boarding ladder! (there is a hydrodynamic reason for the transom at the bow, but that is another story). You can see how the bow transom has been driven backwards through the topside panels, and that the framing has suffered serious structural trauma. In addition the planking-to bow transom epoxy fillets have been more or less destroyed.

Looking aft at part of the damage inflicted to the forward cabin bulkhead by the floorboard assembly. The boxed opening at the far left of the photo is the cabin ventilation opening - lets air through but keeps water out...

External damage to the starboard side of the bulkhead after initial paint removal...

......and the same on the port side. Doesnt look too bad, but represents serious structural damage on close inspection from inside and out.

Micro has a primary structure made from 6mm/1/4" marine plywood for the most part, with a substantial amount of 3/4" framing timber throughout in various widths. The boat relies on her large volume and surface area for her structural strength, and is well designed from an engineering perspective. However, like many aircraft, she is structurally strong, but vulnerable to point impacts.

Bulkhead damage

Damage to the bow

Damage to the bow.

The point of this post is to let people know that with careful planning and execution, a wood/epoxy boat can almost always be repaired to as good a standard (or better) as when she was built. Do not skimp on the process and avoid any temptation to "plaster over the cracks" so to speak - attention to structural detail is essential.

I may write more about the repair process use on this boat in a later post (no promises), but here are a couple of photos of the structurally complete repair, with only a few remaining paint details to be finished.

Just some painting to be done over the white two-pack epoxy primer/undercoat visible at the forward end of the keel, and some black boot-topping to be painted as well.

The repair process involved a lot of debris removal, fabrication of simple jigs to regain the correct hull shape, re-lamination of damaged plywood sheeting, plenty of epoxy, epoxy fillets, and glass fabric reinforcements - but the boat is alive and well!

The moral of the story is to build your boat properly in the first place, and repair her with care if the need arises. Have an open mind and be prepared to be inovative and to improvise. There is no reason why a home-built plywood boat should not last several lifetimes, even if damaged along the way. In fact, if you are not under too much time pressure, the process can be both challenging and rewarding.

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Thinking About Phil Bolgers MICRO Part 2

A little while ago I wrote a preamble in response to a request from Dennis Marshall for comments about Phil Bolgers wonderful Micro design - see http://rosslillistonewoodenboat.blogspot.com/2011/05/thinking-about-phil-bolgers-micro.html

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 Bolgers 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 dont know where to draw my personal line. Suffice to say that of all the designers Im aware off, Phil Bolger has had the greatest influence on my thinking.

You may think it is a case of hero-worship, but I dont 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 Hunts open mind....

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

??



Integral boarding ladder which makes the boat go faster!

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• 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 doesnt 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.??
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• 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.



Micros 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.
• Micros cockpit doesnt 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 beams 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 doesnt) resulting in a reduction in stability when heeled. So Micros 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 Ive written too much for one sitting. A careful study of hundreds of Phil Bolger designs will reveal many similar examples of the designers 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....

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Thinking About Phil Bolgers MICRO Part 1

A few weeks ago, Dennis Marshall wrote to me asking for comments about Phil Bolgers superb Micro. Here is Dennis message: -

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 Bolgers 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.

Well, I am keen to respond to this request, although I have to admit to being intimidated by the idea of making comment about the work of someone as well-regarded as PCB. I hope to write something this week. 

Ive been very busy over the last week, and have also been away, so the writing has been delayed. However, I thought it may be appropriate to start off with a very short piece I wrote about ten years ago dealing with an imaginary cruise aboard a Micro.

The style is a direct copy of the type of essay which Phil used to write about cabin arrangement in issue #86 of Woodenboat Magazine. Although the trip is from my imagination, the information is based on experiences I have had over a decade or so.

Mike Rowe stood in the companionway of his small cat-yawl holding a mug of black coffee, which was now half-cold due to his habitual day-dreaming. He was at last starting to relax after the mental and actual turmoil of the preceding days. It seemed to him that the only place he could really unwind was on the water, and the current conditions were his favourite. A light north-easter was moving his keel-sharpie steadily past Earlando Resort and he was anticipating with satisfaction the first mental milestone of his outing – Gloucester Island.

Mike, who was approaching middle age with at least some grace, had calculated a speed over the ground of 4.63 knots since departure four hours earlier. Calculating was habitual for him. At this rate they should reach the rendezvous with his friend Ian by one pm the next afternoon, allowing for the present favourable ebb tide.

Although Mike’s coffee was now cold and unfinished, it had provided him with satisfaction beyond measure, just by having been prepared in the tiny cabin while the boat steered herself. How many times he had dreamt of such activity he could not have told anyone; but although long in the gestation, the situation had been as sweet as he had anticipated.

The other activity he had particularly enjoyed was lighting the kerosene navigation lights. These had come from a supplier in Canada many years before (he also habitually bought gear before it was needed, as though it would bring a cherished project to fruition ahead of time!) and promised to be a worthwhile investment as long as the contents of the reservoirs could be prevented from permeating the vessel. To this end, the skipper had stored the filled lights in a plastic nappy bucket. This he had chosen because of its robust construction and close-fitting lid. It normally resided in the aft free-flooding well, where kero spills could be washed away with seawater. They were more reliable than the corroded wiring of his mate’s GRP sloop – electricity had its place, but that place was not on a small boat.

Just after eight pm, Mike went below to rest. Had anyone else been present he would have justified his action on the grounds of tiredness – but as he was alone he could indulge himself for the real reason, which was that he loved to feel the little yawl steer herself. The feeling was heightened enormously when he went below. The wind was forecast to veer, so any unnoticed course change should be towards open water. A medium sized, spherical compass was mounted through the main bulkhead, so he could monitor headings from the bunks as well as from the cockpit. Danger of collision was his only concern, but during construction he had stuffed crumpled aluminium foil inside the hollow wooden masts to act as radar reflectors.

The hypnotic sound of water against the 6mm plywood planking lulled him into a short, relaxing sleep, but the novelty of this trip soon saw him back in his favourite position in the companionway. What had always puzzled him was why so few people followed the cheap and simple route to boating pleasure? Mike’s boat had cost him only a few thousand dollars, and six months part-time labour – yet she was built of the best materials and had an effectively unlimited life expectancy. His friend’s glass boat had been much more expensive (even second-hand) but gave little extra other than internal room. On the other hand, it was in need of major work to treat osmosis, and was a real handful on a trailer. To each his own – but Mike Rowe felt happy in the knowledge that his boat was simple to maintain, and that her total cost including trailer was less than the expense that Ian had incurred upgrading his vehicle to tow the second-hand GRP boat. The little wooden boat had no standing rigging, no sail battens, no stainless fittings, no winches – yet she was a true open water vessel. Self-righting, positive buoyancy, two full-sized bunks, dedicated storage hold – all very shipshape in her brush painted finish.

Mike Rowe’s advice to those who came to see his boat? : -

·        Start building, even if it is smaller than the project of which you dream;

·        Use high quality timber, adhesives, paint and tools;

·        Keep up the momentum of the project – letting the job remain idle for even a few days makes it much more difficult to continue;

·        Never leave anything in the construction which you don’t feel good about – no bad timber, no bad glue mixes, no bad joints etc;

·        Seal all surfaces and joints;

·        Follow the application instructions for the painting system religiously;

·        Resist the urge to varnish;

·        Keep it simple.

Here is a link to a youtube video taken from on-board a Micro. It was a very light day - 8 knots of wind max - but the little boat went very well indeed on the smooth waters of Wivenhoe Dam here in Queensland, Australia.

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