Saturday, 9 May 2020

Bow Compartment | Installing Buoyancy

With the completion of the centre board pendant hole I was ready to install the cockpit deck, but I wanted to practice this by fitting the forward deck first. Much of the interior below the forward deck is not visible, so it would not matter if things went a bit awry in this area.

So ... the first task is to install buoyancy in the bow compartment.

The recommended material for this is PIR (Polyisocyanurate) insulation board, which is rigid and waterproof.

I did consider using liquid expanding foam, as seen on one or two other blogs, but people told me it is very messy and difficult to control. So PIR it is.

I obtained a sheet of 50mm foam and set to work.

The first task is to construct a 'tunnel' between the inspection port in bulkhead 1 and the stem. This will allow a bow eye to be fitted to the stem much later in the build, after which the tunnel will be filled with pieces of foam inserted through the inspection port.

I first made a cardboard template for the sides of the tunnel. Here it is, with a very useful cordless cutter. I originally got the cutter for fibreglass cloth, but it handles most light materials with ease.


I then marked up and cut out and bevelled pieces of foam using a compass saw, which made a lot of mess with bits of foam everywhere.

Part way through this I realised that what I really needed was something with a finely serrated, long, thin, flexible blade. Like ... a kitchen knife. A visit to the kitchen revealed exactly what was required, which was promptly liberated.

Here are the tunnel side pieces, with the cutting tools.


I then made top and bottom spacers to hold the sides apart, and decided to use nylon cable ties to fix them in place. Here they are.


The long, pointed piece is the top spacer which butts up against the stem. The short piece is the bottom spacer which sits below the inspection port.

I found that a hand drill was best for making holes for the cable ties. An electric drill just makes a mess. Here is the drill.


And here is the fitted tunnel, held in position by plywood slats and tape while the cable ties were inserted and tightened to make the tunnel a rigid structure.


And this is the view inside the tunnel, looking towards the inspection port and showing the bottom spacer in place.



I then made another template for the crosswise panels to fill both sides of the compartment, starting with the largest piece at the bulkhead. This is the template with the tools used to make it. The blue object is a contour copier, useful for getting the turn of the bilge just right. It was a Christmas present from my lovely wife. Thanks Alison!


I then discovered that a jig saw cuts the panels quickly with a fine, smooth cut and very little dust. Here we are cutting out the first panels.



The angle on the side of the panel where it butts up against the hull is lifted with a bevel. Here is my antique bevel, given to me by my brother-in-law from New Zealand one Christmas. Thanks David!




See … Christmas presents can be very useful!

I worked my way towards the stem, trimming a piece off the edge of the template as required to get a good fit.

Here are two panels with the bevel marked out.



And here are the same panels with the bevel cut with the knife.



Eventually the bow compartment was filled with foam panels. Here it is.



Finally, and quite unnecessarily, I fitted a piece of 25mm foam to cover the lot up and fill the small gap below the forward deck.



That's it. Job done. I made a lot more work for myself than I needed to here, but it was good fun and I learned a lot.

Next step is fitting the forward deck!


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