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Posted by: Tom Daniels 8/17/2008 11:48 PM
It may be handy for folks to see just where the parts we've been making will eventually end up in the boat. To start with, let's look at Cherokee from Olin Stephens' original construction plans.


We'll see close ups from this throughout today's entry, but this will give you the big picture.

Let's start with the ballast. In this boat, the hull weighs about 3,000 pounds, and the ballast weighs 5,800 pounds. That's a lot of lead, and it's been Karl's job to make sure that the mold (more accurately, the plug)  for the ballast keel is just right.  Here he is working on one of the of lifts for the plug.



These lifts all get stacked and glued together like this:



A common centerline allows Karl to keep the layers properly oriented to each other.  Here's what he's trying to do:



This is like a cross section of the ballast.  If the shape he's trying to end up with is defined by the red curve, each layer is cut so that the upper edge of the layer (or "lift") just defines the edge of that final shape.  Once he's gotten all his lifts cut and glued together, he works on the final shape by cutting the excess wood off (essentially cutting the corners off) and fine-tuning the shape using templates.  
  
It's a little hard to see this as the ballast keel while it's upside down, but once you turn it upright,



It starts to make sense.  You can see that he's started to shape the section of the keel that's farthest away from the camera here.

And, in case you don't know where the ballast keel goes, it's at the very bottom of the boat.



It's the part with all those long bolts going into it.  Those are the keel bolts, and they hold the ballast to the keel, and thus to the boat.  If you're sailing along and your ballast happens to fall off, 2 things happen in rapid succession:
  1. Your boat shoots upwards since there's no longer 6,000# of lead holding it down
  2. Your boat then falls over sideways and probably turns completely upside down since the mast is now the heaviest thing on the outside of the hull, and it wants to sink.
In case it's not painfully obvious, those keel bolts are very important and we make them heavy and strong.

And speaking of bolts, we've been making lots of bolts that will connect the floors to the keel.  In the picture above, the floors are the dark rectangles just above the red keel.  You can see them here on Jill's backbone:



And when the floors are just sitting around waiting to be installed on the keel, they look like this:



You saw this before in the last blog entry.  Well, in order to install these puppies, we need lots and lots of bolts.  In particular, we're using a type of bolt called a fin neck bolt.  It's something like a carriage bolt, only the head is flat (instead of round) and the bolt has 2 thin fins coming off of the shaft just below the head to keep the bolt from spinning in its hole.  

We make our out fin necks by heating bronze rod, and pounding the bejeezus out of it.  David is quite good at this.



Of course, it's not enough to just heat and pound it.  You have to pound it into something that will give you the head and fin shape we're looking for.  That's where the steel die comes in.



You can see the shallow depression that the rod is hammered into to get the head shape we're looking for.  

It's quite an art really.  The metal has to be just hot enough to become malleable, but not so hot that your ruin the bronze.  Here's the head shape we're shooting for..



You can see the fins just extending below the head.

David's been hard at work making up the many bolts we'll need for the floors.



We still need a lot more.

I've been working out the locations for these bolts and drilling the holes in the floors.  The trick is to make sure that the floor bolts go straight down through the middle of the floors, that they don't hit any other fasteners along the way,  and that they end up close to the edge of the underside of the keel, but not too close.

This is where a jig comes in handy.

 

NO, no no.  

This kind of jig.



This little jig guides your drill bit straight down through your floor.  The holes in the side allow you to line up the drill bit with the slight angle of the holes in the floor, like this:



You can see the line drawn on the floor lines up with the little marks on the inside of the holes in the blue jig.  These holes simply allow one to see the line drawn on the floor.  The blue wood is attached to a hardwood block with a hole drilled into it that aligns a drill bit exactly with the lines on the blue wood.  



You can see the drill and long bit inserted into the hardwood block here, and the whole affair is clamped to the floor.  This way, your holes go right where you want them every time.

The result is a pile of floors with holes drilled, ready for installation onto the keel.



Max has been doing the final shaping on the horn timber.  



The aft end of the timber is closest in this photo.  In the construction drawing, it's here:

It's the blue part just above and to the left of the rudder.  You can see how the horn timber supports the whole aft end of the boat, just like the keel does in the rest of the boat. 

I've now finished the rabbet on the stem and fore keel.  As before, it started with lots of pockets

 

that were then joined together to form a continuous rabbet



By the way, this part is here on the drawing:



The lower yellow part is the stem, the blue parts are the fore keel.  Even though they're different colors, in this boat, they're all one piece.  The fore keel joins up with the keel (colored pink here) using a long, tapered joint called a scarf.  Here's that joint being worked out on the fore keel.



Robin has been checking the shape of the fore keel using a template, and making sure that when the keel and fore keel are scarfed together, that they form a perfectly straight, continuous line.



We're shooting to get the keel and fore keel joined up and set on the floor in the coming week.  We've made a sloped surface for them to sit on that will put everything at the proper angle while we're building the boat.

 

The whole boat will rest on this thing, so it's pretty sturdy.

Lastly, Jason has been working on the stern post.  



That's the blue angled part that sits on top of the ballast keel, in front of the rudder, and attaches to the underside of the horn timber.  It has a cove cut into its aft face to allow the rudder and rudder post room to turn.



He did a very nice job.  Next week the plan is to join the keel and fore keel, set the whole thing up, attach floors and molds, and this collection of parts should start to look like an actual boat!
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