February 2017

February 27, 2017

I've been working hard on making the appendage keel for the boat.  The appendage keel is a triangular keel at the aft end of the hull where the rudder is attached.  It also provides directional and lateral stability as well as protection for the rudder.  I've chosen to build it up from laminations of 3/4" marine plywood.  Actually, I used scraps from cutting out the bulkheads and keel.  It took every scrap I had in the shop and managed to clean the shop at the same time.

The first step was to lay out the appendage keel on the work bench.  Gathering all the scrap 3/4" plywood I could find I ripped it to 4" width.  I cut and rough laid all the 4" strips within the outline on the workbench.  These are loosely laid so when I had filled my outline I clammed the entire assembly with 1" bar clamps.  I lost about 5 or 6 inches when I applied pressure via the clamps.  This shrunk the triangle.  I measured for additional pieced and added them where I thought would fill the triangle back out.  These steps were repeated until the entire appendage keel lay out was filled with wood under clamping pressure.

Lines were drawn at the boundaries of the appendage keel and down the middle.  All the pieces were numbered and I cut about an inch along one of the boundaries.  This helped me align the pieces when I glued them together.

I glued (West Epoxy) about 10 - 15 pieces at a time and made sure I had adequate clamping pressure. Ending up with a stack less than 12", I was able to run them through the portable planer and quickly clean up the sides when I was done.  It was also difficult to maintain the proper shape clamping more than a few pieces together.  After the first set, I used a pneumatic stapler to hold the pieces together.  Two in the middle and one on each end of the pieces.  This kept everything aligned without too much danger of the staples interfering in drilling holes and final shaping.  The 5 sections were then realigned once the epoxy was cured and the sides cleaned.  I used strips of wood to temporarily hold all the sections together.

All the sections held together by strips of wood.  

 Once I was happy with the lay out, I used the circular saw to cut the entire keel to shape.  It took two passes, one on each side.  I then marked where the two 1/2" stainless steel threaded rods would go and where the cut-out for the prop would be.

Notice the two faint lines where the threaded rods would be drilled and the cut-out on the left where the prop will go.  

Two half inch holes for the threaded rods will go from the bottom center to within 3/8" of the top and bottom edge.  A tricky drilling.  I actually got a little off in the last two sections and had to make some adjustments.   In the end, I was happy with the results.

This is the jig I built to guid the drill bit through all the pieces.  I only have a 24" drill bit so I will have to repeat this jig set-up a few times.  This is actually the second setting of the jig.  You can see that there are shims under the jig to hold it off the keel.  This maintains the angle but is appropriate for the holes that are progressively toward the side.

A close up of the jig.  I used aluminum blocks to guide the drill bit.  The shaft of the drill bit was narrower than the bore so there are two aluminum blocks on either side of the 2X6 with different holes.

The boring jig was securely screwed into the appendage keel before each bore.

All together with the threaded rod in place and everything tightened up.  It worked!  

 The next step is to cut a cove into the edge that will receive the rudder.  The rudder thickness at the appendage keel will be 3 3/4" so I will make the cove with a 2" radius.  This will give me 1/4" between the appendage keel and the rudder for a smooth flow of water over the rudder.

I've attached a 2X6 along the edge that will receive the cove.  This will allow me to attach a fence to guide the circular saw.  I also added a brace to steady the keel.  This piece weighs a few hundred pounds and I do not want it falling over especially while I'm working on it.

You can see the fence an a few of the initial cuts.

This view is a little better.  You can see the cove marked on the foot of the keel.  Also not that I recessed the appendage keel bolts and provided a smooth surface normal to the bolts so the washers and nuts would sit tight.

Just about finished with the rough cutting.

Time to knock out the rough stuff.

All the rough stuff is knocked out. The next step is to cut out a bit of the upper section where the prop will eventually go.  I have not worked these details out so I'm leaving myself plenty of room. I do want to cut out a bit though so I can clean the cove up with a cove plane and be able to slide the plane all the way through the cove.  The plane I'm using is actually an antique wood plane use to made molding.  They are very cheap but extremely versatile.  Because they are readily available (and cheap) you don't feel bad about modifying them to suit your work which I did a bit to the ones I used.

Plane work is done.  Wasn't easy by any stretch of the imagination. 

60 grit sandpaper glued to a 3" schedule 40 PVC pipe cut to the length of a sheet of sand paper cleaned this cove up with quite a bit of elbow grease.  I sanded until all the score marks from the circular saw were removed.  I then followed with 100 grit sand paper on the same PVC.

The next step will be to radius the forward edge.  I'll end up with a 1" radius at the leading edge.  Then I'll smoothly take the 2" thickness to the full 4" over 4 or 5 inches.  I'm also contemplating glueing a few of the sections together so that I have only 3 easily managed sections.  The top two section will have the drive shaft tube bored through them.  I'll glue the last three sections together as I mount them on the hull.  It will be nice having a relatively light section to handle when I prepare the bottom of the hull for attachment of the appendage keel.  

Now it's time to flip it over and radius the forward section.  Once flipped and secured, I drew reference lines to help guide the work.  One centerline along the edge.  Two more lines 1" to either side of the center line.  This would be my minimum 1" radius although I'm not going for circular.  The last two lines are 5" from the end and draw on the sides.  These help guide the where the taper ends.  There were a few staples that needed pulling so I would not dull my tools.  These took a bit of digging out. Apparently I was not as careful as I though I was when assembling the piece.  No worries, the fasteners only needed to hold till the epoxy cured.  I then just radiused the end with a power planer making sure to mirror my movements on both sides.  I worked slowly till I had a pleasing radius even along the entire side and cleaned it up with a belt sander using 60 grit paper.  When happy, I chose a side and made a template of half of the radius with a piece of plywood.  I used this template to make sure that the radius was even all along the edge and the same on both sides.  I was very pleased that there was little finishing work to perform to make the end fare and even.  Actually I was quite surprised.

Checking the radius with the template.  A centerline is marked on the template and aligned with the centerline (barely visible do to sanding) on the edge.  This is critical because if the template is not plumb with the work, you will not have the correct shape.

After finishing the radius off with the belt sander, first using 60 grit and then 100 grit, I've redrawn the centerline that I came close to sanding completely off.  I just wanted to retain the reference line in case I make modifications.  Also, looking at the line gives my a nice feeling that everything is even and straight.  

A side view showing the progress.  

All the power planing was followed up with 60 grit sandpaper on the belt sander and then 100 grit.  The entire piece will be finished this way once I've mounted it on the hull and cut out the section for the prop.

Getting close to being done.  I've cut out for the prop and shaped everything for smooth laminar flow.  Now I'm just doing a little filling with epoxy so that everything is smooth.