Inside IYRS 

The backbone begins to take shape

Oct 12

Written by: Tom
10/12/2009 9:30 PM 

The first year students are busy building backbone parts these days.

 

We'll start things out with a little correction.  In the last entry, I said that the hull construction for the Gar Wood was Batten and Seam while the construction of the Chris Craft was double planking.  Well, that's both correct and incorrect.  The hull above the chine on the Gar Wood is Batten and Seam, while below the chine it's double planked.  And on the Chris Craft:  it's the same thing  Thanks to 2nd year student Jens for clearing that up!

When students are accepted at IYRS, they get an extensive list of tools that they'll need.  The first years are getting lots of opportunities to use these tools now as they are deep into the production of boat parts.  Let's take a look.

The old stems have been removed from the Beetle cats and new stems are being constructed from mahogany laminates.  The thin laminates are steamed to make them flexible and the clamped to a mold to bend them to their initial shape.  After they've cooled, they are put back on the mold and glued together with epoxy to create the rough shape of the stem.



After the glue has dried, the excess glue is removed and the stems are planed down to their final thickness.  Using a pattern, the students mark the stem and cut it to its final shape.  



Sometimes you make a little mistake and need to add another mahogany strip to get your stem to the right size.



No worries.  Learning how to fix your mistakes is a critical part of this business.

There's a lot of planing to be done at this stage so the students get loads of practice using their (possibly brand new) planes and spokeshaves here.



Once the shape of the stem has been nailed down, the next step is to cut the rabbet along the side.  A rabbet is a sloping, curved groove that follows the shape of the stem.  Eventually, planks will have to fit tightly against this groove, so getting the angle just right is critical.



The rabbet has a "rolling bevel."  This means that the rabbet's angle changes as it curves along the face of the stem.  If it was a constant angle, one might be able to devise a way to make a router jig to cut the rabbet perfectly every time.  Not so here.  This is strictly hand work.  One thing that makes this tricky is that most of these students have never built a boat before, and so they've never had to fit a plank into a rabbet.  Cutting this joint is purely an exercise in trust that if they accurately transfer the lines from their patterns, and then cut their rabbet to those lines, that it will provide the perfect landing for their planks when they eventually curve into the stem.



It's not something you want to be distracted by when you're trying to chisel a slope to just the right angle.  

The biggest part that most students are working on these days is the keel.  It's a thick piece of oak that's been cut to shape, and then steam bent.  The keel also has a rabbet cut into it.  That's the slot you can see along the upper edge of the keel on the left.  



To the right of the keel is the pattern that the students used to mark the shape of the keel.  The pattern also has layout lines on it to orient the keel on the boat as well as lines to mark the centerboard slot.  

Here, a student is using a circular saw to cut out that slot.



He uses a board clamped to the keel to act as a guide so that his slot will be dead straight.



In fact, one of the things that students learn in these first months is that circular saws are not just for cutting straight lines; they're great for cutting gentle curves.  Most folks who use these saws in the construction industry only cut straight lines with them.  It may seem like a small thing to some, but for many of the students, this a genuine revelation.

Once the keel is marked and rough cut to shape, the students finish shaping it using hand planes.



Teamwork.

With the keel shaped and rabbeted, it's time for bending.  IYRS has a kick-butt steaming set up.



The silver unit is an industrial steam generator, and it powers both of those long steam boxes you see behind it.  This is a 40 Kv generator.  To put that in perspective, the portable space heater you might use to keep your feet warm at home uses about 1.5 Kv.  This puppy uses about as much energy as your house.  



It can really, really put out the steam is what I'm saying.

So, the oak keels are loaded into the steam box and heated up for about an hour / inch of thickness.  Once they're pliable, they're quickly pulled out and clamped to a bending jig.  You can see the slight curve produced here in the keel on this student's bench.



And here's a bent and shaped keel set in place.



The keel and stem are 2 parts of what is called the Backbone of the boat.  Seeing them put together on the bending jig starts to make that name come to life a bit.



Some students are also working on their skegs.  The skeg is also made of oak and will be fastened to the underside of the keel.  



Learning how to plane (or spokeshave) a curve while keeping the face of that curve square to the sides of the skeg is a new skill for many.



It's good to check for square all along the face as you go.



A few folks have also moved into making their centerboard trunks.



They'll be primed and then painted with anti-fouling bottom paint on their wet surfaces to inhibit critter growth.  In a little while, they'll be attached to the top of the keel.  

Over at the Chris Craft things are moving along smartly.

They're also working on a keel for this boat.



Same skills as learned in the first year, but no one makes the patterns for you.



The same is true for the frames.  Here a student is copying the shape of an existing frame onto a pice of thin plywood.




He'll take these templates over to a slab of oak and lay them out for cutting.  





What he's trying to do is to match the curve of the frame with the curve of the wood's grain.  In a perfect world, he'll be able to find a section of grain that exactly matches the curve of the frame.  This makes the part as strong as it can be.

The original 1939 engine has arrived back at the shop.



The folks over at IYRS's Marine Systems program have looked it over and pronounced it "leaky."  



That means we send it out to the pros for some more intensive work.

Here's a little "that's why they do it that way" lesson:  when builders have to fasten something into a long part, like a frame, they make a point of not putting their fasteners exactly in a line.  Instead, they offset each fastener a little above or below the one nearest to it.  They do this because fasteners exert a wedging action on the wood, and if you have all your fasteners right in a line, all those small wedges can act together split the part along the grain.  Like so:



Offsetting the fasteners spreads that wedging action out along different sections of the grain and reduces the chance that the part will split.

Lesson over.

Up on the 2nd floor, the lofting for the 12 1/2 has been completed and mold -making is well underway.  



The solid wood pattern is rough cut and then fastened over a curved spline that follows the shape of the mold on the lofting.  You can see it peeking out from beneath the pattern in this photo.  That curved spline is used to guide a router with a straight bit to bring the pattern to its final shape.

After shaping the pattern, various layout lines are transferred from the lofting.





Since the boat is symmetrical, both sides of the pattern are cut at once in this operation.  They are then opened up and fastened together into their final shape.



One by one, the molds are completed and stacked up in preparation for fastening to the building floor.



That's where these students are, setting up the station marks and other lines that will guide the placement of the molds.



After much fussing and tweaking, the Gar Wood is finally leveled, straightened, and secured to the building floor.  



This allowed the students to get good measurements for their lofting and they're spending their time upstairs working out those lines.  



More on that one later.  

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