Lead Keel and Painting

Here's where I'm up to today. Read on to see the steps along the way.

There is a photo of the mould for the lead keel in the previous post. I was nervous about melting the lead and pouring it into the mould for a variety of reasons. After a week of sitting in hot sunshine the surface of the mould still felt damp; I decided that the Plaster of Paris is hygroscopic and the high humidity made the surface feel damp. I was also concerned about actually spilling the molten lead and being splashed. Consequently I approached the job wearing heavy clothing, boots, welding gloves and a full face mask. This on a day when the temperature was 37C! The melting was easy, gas stove and old stainless steel saucepan in the open air. The pouring was harder because the saucepan was heavy (obviously), didn't have very good handles (although a pair of multi-grips improved on this) and didn't have a pouring spout. The lack of a spout was the biggest problem and resulted in a somewhat messy pour.

I cut of the flashing around the top with the bandsaw and then flattened the top with the power planer; both dealt with the lead OK although there was a tendency for the lead to "weld" onto the edge of the planer blades.

I made the pattern sightly larger to allow for the shrinkage of the lead as it cooled with the result that the casting was slightly oversize. The excess was removed with the power plane and belt-sander. In the photo above the lead is sitting on the hull as I "fine tuned" the shape. The pitting in the surface is due (I think) to the surface moisture in the mould which became steam and bubbled through the molten lead. Thankfully it didn't cause any splashing.

I drilled holes for fixing screws (bronze) and bedded the casting in place using thickened epoxy. Some more bag and sanding and the hull was ready for the the fibre glass cloth.

Two coats of unthickened epoxy with each coat applied when the previous coat was just still tacky and it looked like the next photo. A third coat with enough sanding filler to give it a creamy consistency completely filed the weave of the cloth and provided a surface that could be sanded flat. The coats of resin were poured on and spread with a squeegee cut from a length on 1.5mm balsa sheet.

The patchwork quilt disappeared under three coats of primer and 3 coats of undercoat followed by a lot of wet and dry sanding.

Then the waterline was marked and taped and 4 coats of satin finish paint sprayed on.

Now to the exciting part. I "launched" the boat into my garden pond to see where she floated and to get a feel for how much internal ballast would be needed to sink her to her waterline. The photo at the start of this post shows Tally Ho floating quite high with no internal ballast added. Adding a  mixture of lumps of lead and  concrete pavers sank her down to her waterline.

Now for some numbers. The bare hull weighs about 12 kg and the internal ballast added 17 kg for a total of 29 kg. It's now clear that I will need a trolley of some sort to transport the completed model to the water. Sure I can carry 29 kg but not when it is a big awkward shaped model boat!

It is interesting to compare my model displacement with the full size displacement given on the original plans, The plans show a displacement of 30 (English) tons or 30481 kg. At 1/10 scale the volume of water being displaced is 1/1000 of the full size boat so my model displacement should be about 30.5 kg. Adding another 1.5 kg of ballast to the model would sink it a bit more but only by a couple of millimeters.

I think it has all worked out according to plan.

Slow Progress!

Progress seems to have been slow but there has been some. I found a suitable propeller and shaft and after some head scratching drilled a hole through the stern post and installed the brass tube making sure the space between the metal and wood was completely filled with epoxy. Here's what it looks like  from astern - Captain Pugwash is a bit on the short side, he's only 5 foot tall including his box!

The propeller is 60 mm diameter which scales out to 24" which is about the size I measure off the plans and looks about the size of the prop that Leo pulled out of the boat in video 7 but it isn't as heavy!

I cleaned up the inside of the hull using sanding disks on a Dremel. It is still uneven but the blobs of epoxy are gone. It now has a coat of epoxy with grey primer over that and looks quite respectable. No one is going to see it when the model is finished!

The outside of the hull was more of a challenge as it has to have a smooth surface. Sanding removed the high spots in the planking and an application of epoxy "bog" (white) filled in the low spots. Sanding and more bog (grey) and more sanding gave it a surface that I'm happy with. It looks a mess at the moment but that will be fixed soon.

The drawing show the stern post cutaway to give clearance for the prop. Leo's videos show that the prop was held away from the stern post by a wooden spacer block. I've chosen to follow the plans with cutouts in both stern post and rudder. Here's what it looks like (I need better hinges!).

I've made a mold for casting the lead keel using the wooden pattern made previously. I used Plaster of Paris because it is easy to work with and readily available. It is taking a long time to dry out (still feels damp after 2 days but in Brisbane's high humidity it is taking longer than expected). If it doesn't dry out in another day or so I will put it in my steam box with a hair dryer - it is too big for the kitchen oven. It has to be dry because moisture and molten lead are a bad combination.

I've begun thinking about how I can control the sails with radio control. Obviously by using servos but just how to do this is not so obvious. The main sheet needs 800 mm of travel as the boom moves from the centre line to just touching the shrouds. There are several ways of handling the main sheet using sail winch servos but getting the 800 mm travel is a problem. The foresails provide a different problem because there are two sails (working foresail and number 2 jib) that need  different amounts of sheet travel using one servo also one sheet has to be let out so the other can be taken in. Of course all of this has been done before but not by me and I am having trouble finding the "how to" information.

The reason for sorting out the sheeting and servo arrangements is that I want to get them installed and working before I start putting the deck on. Once the deck is on access to the inside of the hull will be more difficult unless I can find some tiny assistants.

Next steps are: cast and fit the keel, fibre glass the outside of the hull and put some primer on it, continue working on the sail control.

Planking All Done

 The planking went fairly quickly to begin with because the planks could be put on without any shaping. Eventually one or both ends of the planks had to be shaped. Even then the process was much easier than it would be on a full size boat. I used clamps of various sorts to hold planks while the epoxy set. Mostly though I used staples put in with a hand powered stapler and then pulled out the next day. Inevitably the stapler picked up some epoxy and I killed one stapler.

The next photo shows the last few planks going in on the port side. The staples are clearly visible. This whole process was very sticky. Applying epoxy to the edges of planks and holding them in position was very messy. Fortunately I don't have any allergic reaction to the type of epoxy I use but it will be a few days before my hands are clean again!

Some cleaning up of the excess epoxy has been done (hot air gun and scraper then sandpaper) and the outside part of the stern post is being glued in place.

The outside part of the keel (below the rabbet line) has been glued on and the light coloured pine piece is the pattern for the lead keel.

The hull is now the right way up.

There is something not quite right about the sheer line above the forward cradle; it seems to bulge up but probably only by a couple of millimetres.

At this stage the inside of the hull is a mess with blobs of squeezed out epoxy along the plank joins and at the frames. I'll have a go at cleaning it up but it will be difficult to get access with a scraper so it isn't going to be perfect. Also. the gaps between planks that didn't get filled with epoxy are no more obvious. Can't use oakum and a calking hammer at 1/10 scale so the whole inside of the hull will get painted with epoxy slightly thickened with filler powder to make it slightly less runny.