Wednesday 27 November 2019

Lazarettes | The Conundrum

While the floor boards were hardening off inside the house I started to think about painting the interior of the hull, ready for permanently refitting the floor boards.

At this point it became clear that there was a potential problem with the stern compartment. A glance at the hitherto largely ignored profile drawing #4 showed a small amount of buoyancy installed in this compartment.

The build manual, however, shows no such thing. In fact, the builder goes on to deck over the stern with no mention of solid buoyancy whatsoever.

I'm guessing that there is a mistake here, somewhere. Maybe the requirement for stern flotation in the prototype PocketShip was an oversight by the designer, or maybe the builder forgot to include it on the boat and in the manual.

Either way, it's an issue.

I looked at other builders' blogs and saw that they tackled this problem by creating what they call lazarettes, meaning dividing the stern compartment into two separate lockers accessible by the deck hatches.

This means that the buoyancy is sealed permanently into the space below the footwell sole. Some builders do this by fitting vertical panels between the footwell sole and the bottom of the hull, and some do it by fitting horizontal panels from the bottom of the footwell sole out sideways to the sides of the hull. Either way means that there is no access to the sealed space should there be a need for maintenance, repair or cleaning.

I thought about this for a few days, and decided to do nothing. I don't wish to have a permanently sealed area below the waterline anywhere in the boat, and having carefully built the stern compartment I didn't want to make compromise modifications on the fly.

So I will resolve the problem by installing a buoyancy bag underneath the footwell sole, secured by straps. That way it can be removed for maintenance, and requires no rework on the stern compartment.

And I can do this at any time. Problem solved.

Various sizes of buoyancy bag are available from Crewsaver here in the UK.

Onwards and upwards!

Monday 11 November 2019

Floorboards | Finishing With Danish Oil

The floor boards were all complete and awaiting a finish. I decided to use Danish oil, purely because that is what the builder in the manual used and I figured that if it is good enough for a professional then it must be good enough for me.

Danish oil is apparently a blend of Tung oil and solvents. This is the brand I selected, having read good reviews of it.

And I decided to try foam brushes out for the first time, again having read great things about them when used for varnish. Here they are.

They are excellent, allowing fast, easy and accurate coverage with no mess.

I used just under a litre of the oil to apply four coats to both sides of the floorboards. That should take care of them.

When the odour had disappeared I moved them into the house to harden off completely before being set aside to await final and permanent installation.

This is the TV lounge currently.

We are getting there! My next job is to tidy up the interior of the hull and paint it before refitting the floorboards for the very last time.

Floorboards | Making The Lift Out Sections

With all the floorboards rounded over and sanded smooth it was time to make the lift out sections, which of course entails the nerve racking business of cutting full length floorboards into three pieces.

So I measured twice, and cut once. The results were excellent. I used the mitre saw to ensure that the cuts were accurate and clean , as below.

The pieces of the lift outs were then joined together by three cleats made from scrap Ash. Here they are, glued up and fastened with temporary dry wall screws.

It remained for me to drill the finger holes. These had to be quite large at 25mm and perfectly vertical, with a very clean cut and crisp edges.

I experimented with the router and a plunge cutter, but it was a failure. A hole saw would probably work but I could not be sure of drilling true vertical holes with a drill and I was not sure of the quality of the cut.

What was really needed was a Forstner bit, which is specifically intended for this sort of job. Forstner bits though are for use in pillar drills. In the sure knowledge that I would face this problem again in the build I decided to invest in one.

I looked at the pillar drills in my preferred tool store. The biggest craft and hobby model was too toy-like for the job, and their entry level trade model was enormous and immovable.

I needed something in between that would be good enough to drill stainless steel tubing when the time came, as well as hardwood floorboards now.

I found another tool store online which sells a vast range of pillar drills and called them to ask for advice. They were very helpful and recommended a model between their craft/hobby and trade ranges which can satisfy my requirements but is small and light enough to store in a corner when not in use.

So I visited the store and bought one. I also  purchased a set of top quality Forstner bits by Fisk. Here are the bits.

And here is the drill, set up to drill the first finger hole with a 25mm bit.

Here is a close up showing the drill clamp which I purchased with the bits to hold work down firmly on the drill table.

It was set to a slow speed for drilling hard material, and after a few tests I drilled the finger holes. It worked brilliantly! Here is one of the holes after drilling.

The temporary screws were removed and replaced with silicon bronze wood screws, and the lift out sections were ready for finishing.

That was good fun! I love my new drill ...

Floorboards | Levelling The Planks

During the whole exercise of fitting the floorboards it became obvious that some tuning of the height of the floors would be required to get them to sit level and fit nicely.  So out they all came again!

Shims were required on bulkhead 2 and floor 3, and I also decided to increase the width of the sister cleat on bulkhead 2 because I didn't think there was enough material for the screws to securely hold the floorboards. I made the shims from plywood scrap, tapered to make the floors level. Here are the modifications being glued up.

I also fitted an insert to the port side of the cleat on bulkhead 8 because it was not long enough to securely fasten down P4. Here it is.

I made and fitted mini cleats to floors 4 and 6 to support the lift out floorboards because the floor by itself was not wide enough for the job, as here.

Lastly all the floorboards were refitted (for third time!) to check for levelness.

All was well! Finally all the floorboards were taken out (again!) and rounded over with a 3/8" bearing guided router bit, and sanded smooth.

Floorboards | Fairing The Planks

Marking in a fair curve to the floorboards requires a long, flexible strip of some kind. I used a length of wooden edging.

Here is the batten held in place by spring clamps against nails pushed between the floorboards.

When the curve was marked to my satisfaction I removed the boards one by one to do the final trimming with the jack plane, and then replaced them to check the final fit.

Here are the trimmed boards, all in place.

Now I can stand in and move around the boat with ease. Hooray!!!

Floorboards | Fitting The Curved Planks

With the easy-to-fit full length floorboards in place I now faced the challenge of making the shorter boards with curved ends, and in the case of the outermost boards entirely curved sides.

I must say that in common with some other builders I felt somewhat abandoned by the build manual at this point. It devotes just three pages and five photographs to what is actually a really big project. You can tell that the writer of the manual was not the builder of the boat!

My first question was how to shape the edges of the floorboards where they meet the sides of the hull. Should the edges be perpendicular to the top of the boards, with vertical edges, or should they be chamfered to lie flat against the hull sides? The manual offers no clues, and I could find examples of both approaches in builders' blogs.

However, common sense prevailed when I realised that a chamfered edge would require the planks to be longer and wider than they are designed to be. So that was easily answered.

My next question was how do I mark up the curved ends and edges on the floorboards? It was easy to see how the final fairing would be done, using a batten on the fitted boards, but how do I cut the boards to shape without removing too much or too little waste for them to fit?

I tried making a pattern but that didn't work. Then I tried spiling from the side of the hull onto stock, but all that did was mark in the curve that would be required if the boards were chamfered.

In the end I figured it out from other builder blogs.

First you need to mark where the full width floorboard first touches the side of the hull at both ends. This point is where the curve begins. In the pic below, X marks the spot where the full width of P5 meets the hull at the bow.

Mark this on the floorboard, then draw a straight line to a point at the end of the board which removes enough stock to allow the board to be fitted but leaves enough for the final curve to be faired in. Like this.

Here is P5 fitted in place. You can see the gauge being used to mark the position of pilot screw holes on floor 4, and the spacers to hold the planks 1/8" apart. I held the boards lightly in place with bar clamps, just to stop them from moving while I was marking up. 

Not all the floorboards had perfectly straight sides, unsurprisingly, so needed a bit of trimming to make them sit neatly alongside each other.

Here P5 is being trimmed with a big Lie Nielsen panel plane which I bought ages ago for just such a job. The jack plane isn't long enough to do this.

You don't need a plane like this very often, but when you do it really is the only way of getting a true straight edge.

So that's how I fitted the curved floorboards ready for final fairing. It's a bit hit and miss and is not very scientific, but it works.

Here are all the floorboards fitted, looking aft.

You can see in the picture below that the curve will flow between the points where each side of the board meets it's neighbour. The trick is to leave enough waste in place to scribe in the curve.

The next step is to fair in the outline of the floorboards.

Floorboards | Fitting The Rest Of The Full Length Planks.

There are eight full length floorboards running from bulkhead 2 at the front to bulkhead 8 at the rear of the hull - four on each side of the centre board case.

I refer to them as either port (P) or starboard (S) and by number, going from the centre board case outwards to the side of the hull.  Thus P1 to P4, and S1 to S4

Fitting them does not require a lot of work, other than making sure that they are the required 1/8" apart.

However, it does require focused attention and bearing in mind our mantra mentioned in the previous post ("measure it twice, and cut it once") I immediately made a silly mistake when marking up and drilling the countersunk screw holes.

There are lift out sections in the floorboards, two boards wide and on both sides of the boat. They run between floors 4 and 6, meaning that the lift out boards do not require to be fastened down to floor  5.

The first plank I marked up and drilled was P2, and of course I forgot that the lift out does not require screw holes.

So I cut and fitted ash plugs to fill the holes, hoping that they would not be noticeable. They are ... at the time I considered it to be a big deal but on reflection it is a purely cosmetic issue, so I downgraded the incident from Cock Up to Silly Mistake.

Here are P2 and P3 being test fitted. You can just make out the bungs in P2!

I used a countersink drill bit in the plunge router to bore all the screw holes. Here it is.

Before each plank is fitted pilot holes have to be carefully drilled in the support floor or bulkhead cleat.

The planks were fastened down with temporary dry wall screws, which will be replaced with silicon bronze wood screws when the planks are permanently installed later in the build.

Here is S4 in the process of being fitted. A drill driver makes short work of the very many screws, and a piece of stiff wire is useful in aligning the floorboard with the pilot holes.

There is insufficient room for a drill to be used below bulkhead 7 and below the cleat for the cockpit sole on bulkhead 8, so a new tool had to be purchased.

This right angle drive made it easy to drill pilot holes and drive screws in tight corners. An excellent piece of kit!

Here we see all eight full length floorboards fitted. Note the unusual pattern and colouration in the grain in P4 at the rear. I don't think it is very attractive but as with the plugs it is a purely cosmetic issue, so I placed that plank where it will be hidden under the cockpit decking - out of sight and out of mind!

The next step is to fit the curved floorboards, which had me scratching my head for a bit ...

Floorboards | Marking Up And Fitting The Central Planks

At last the time had come to make and fit the floorboards! I had really been looking forward to working with some real wood again, and setting the epoxy resin aside for a while.

Now, the Ash provided to make the floorboards is beautiful wood and it would be a crying shame (as well as expensive) to waste any of it by careless working. So the mantra for this phase of the build would very much be ... "measure it twice, and cut it once".

Bearing this in mind, the first task is to fit the two central planks which run along either side of the centre board case. This requires a section to be cut out of each plank to accommodate the case.

Rather than directly mark up and cut the planks themselves, I made a pattern to be sure the fit was correct before any wood was cut. I wanted to be sure that the width of the cut out would ensure that the two central planks would sit 1/8" apart when fitted, and that the curved front end would sit nicely around the case.

Here is the pattern, slid into place. This is how I wanted the planks to fit.

When the fit was correct I used the pattern to mark out the waste section on both boards, like this. 

Only when I was completely confident did I get out the saw, planes, chisels and rasps.

Lastly I test fitted them, as here.

So far, so good. I have floorboards!