The Ballast Project

And so the Ballast Project can begin!

The 300kgs of ballast for the project has finally arrived.  As you can imagine, sourcing this was tricky to say the least.  Many companies that I talked to simply refused to even answer emails as the quantities were not what they normally deal with, normally dealing in tonnes.  Some that offer manufactured shot were far too expensive considering what the use of the product would be for.  Even bulk abrasive products like crushed steel was expensive.  The best results I had were from engaging companies that either had steel punchings as a waste product to a manufacturing process, such as punched decking or perforated steel sheets and were hence eager to get more than just scrap prices for the offcuts, or reselling companies that deal specifically in these waste materials on behalf of the manufacturers.  I found such a company, that deal in a few specific steel by products that are entirely suitable for ballast.  Their prices were the best I had found considering the quantities I needed.  I could have got cheaper, but I would have needed to take a tonne, and I do not want to have to deal with 700kg bulk fragments of steel!

The product I chose for my ballast was the Steel Punchings which in my application, were clearly the output from a perforated steel panel manufacturing process.  In my case, the product was also galvanised before entering the press, so my punchings will be well protected from corrosion to begin with.  With a quoted bulk density of 4500kg/m3 I was well set.  Each keel can take 40 litres, a result I have physically checked when I was dismantling the interior of the boat by filling up one of the keels with 2 litres at a time from an Irn Bru bottle (well I am Scottish).  I would therefore have 32.7 litres of steel in each keel, and so needing 13.6 litres of encapsulating resin to full up the interstices in one keel, or 27.21 litres in total.  All this is in the calculation package available here: (CALC PACK)

Now that I had the ballast on hand I verified the calcs by doing some experiments.  I checked the volume of water that 8.6kg of punchings could absorb - 0.75 litres thus 0.087 litres of resin per kg of ballast, thus 26.1 litres of resin for the whole job... so I was only 1.1 litres out - a figure I can happily live with!!!

I also tested 1kg of punchings with polyester resin to verify that the ballast would absorb it correctly.  I started with 1kg of punchings in the bottom of the mould with a mark on the side of the mould to check that the before and after volume remained the same.  I then poured the resin in on top.  It was slowly draining into the ballast, so I started to mix it to ensure absorbtion.  Upon mixing it quickly filled the interstices, and remained at the same level in the mould, which is a good result.  I weighed the completed moulding at 1.1kg, so ratios are all spot on.  The ballast checks out and I can proceed with installation.


8.6kg of ballast at the testing stage! 8.6kg of ballast absorbs 0.75 litres of water 1kg of Ballast absorbs 0.1 litres of resin


17th October 2011

So the ballast project went quickly!  Males a change really...

Over the course of a few days I filled the keels up with the new ballast punchings and unthickened polyester resin.  I catalysed at 3% and worked in batches of about 25kg.  I adopted this strategy to ensure that I had a full cure to the resin, but kept the potential for a runaway exotherm low.  This worked well, and I was able to do up to 3 batches a day.  To bolster my ballast I installed a 25kg length of chain by halfing it and using it in one of my batches.  The small punchings easily took up the spaces between the chain links.  At this point, the total installed ballast stands at 340kg.  I have kept 12.5kg of punchings back incase I need to apply trimming ballast at the floating stage.

Pictures should say it all!

First batch - right down in the bowels! Plenty progress and the keels filling up A batch of chain goes in

More as it happens...

Punchings filling up the chain interstices Operations station and 25kg of polyester! Internal work station... 12.5kg bag ready to pour

And the final result of the ballasting operation...

Starboard keel and batch notes Port keel and batch notes

So the next thing to do is place some serious closing laminations over the ballast to cap it in and seal the ballast.  Then the interior can seriously be built.



19th October 2011

Naomi was feeling keen today so we quickly managed to get the closing laminations for the port side keel completed and looking good.  Firstly I sanded the bonding areas with 40 grit paper to provide a good key, then brushed and hoovered the area out.  Then I solvent washed with acetone and let things dry off while I prepared some filleting compound just to ease the edges and provide a smooth transition for the cloth.  This was then pasted in to make a fillet around the edges.  We let this dry out while we cut the cloth for the job, which consisted of up to 4 layers of 450gsm Biaxial fabric.  Resin would be polyester, as this is a fairly hefty moulding and I would prefer not to drain the expensive epoxy on this part - the epoxy can do more good stabilising and bonding the plywood when it comes to full scale interior construction.  These laminates are only for capping the keel and are not seriously structural, otherwise epoxy would be the resin of choice.

Then Naomi and I proceeded to laminate up the cloth!  Working together to get things done we installed the bonders as needed.  Pics below!

Filleting mix in - both sides Pile of biaxial 450gsm cloth Laminates installed in resin



23rd October 2011

Today I resolved to fit the punching laminates at the back ends of the keels.  These are here owing to the tendency of the keels to rotate upon grounding, punching up at the rear edges.  Although the hull laminates are already thick here for this very purpose, a little more never hurts!  I installed these laminates in polyester again owing the volume of material, and the large bonding area which obviates the need for epoxy.  In total, there is 3 square metres of 450gsm Biax cloth and nearly 4 litres of polyester in the capping laminates.  Installing the punch layer draws the ballasting project to a welcome close!

Starboard side punch laminate Port side punch laminate

Last Updated (Sunday, 23 October 2011 20:02)