Permanent Bulkheads and Frames

Permanent Bulkheads and Frames

A new job in October 2009 has allowed me to finish the boat building and get started on the actual boat.  By August 21, 2010 I had purchased enough 3/4" marine grade plywood to build the bulkheads, keel, and stem.  Hopefully with enough left over to get a good start on the deck (this actually would be the case). The permanent bulkheads are created in a similar manner as the temporary ones were.  One difference is that when multiple sheets of plywood are used to make up a bulkhead (almost all need 2 or more sheets) the marine grade plywood (3/4" Meranti) is butt glued with West System epoxy.  These butt joints will later be backed by plywood extending at least 6" to either side of the joint.  The plywood backing is glued and screwed every 6".  The only bulkhead that I initial backed this way was the one forward of the engine compartment.  (At this point I decided that all permanent fasteners  will be silicon bronze.  I later relaxed this standard for internal fasteners that are covered by subsequent layers.  I will later switch to stainless steel for these saving me thousands of dollars).  The reason for not backing all the butt joints initially is that much of the bulkheads will be cut away later creating the companion ways and the exact placement of these companion ways will not be determined until the hull is flipped over.  There is no point in backing a butt joint that will later be cut away.  A few temporary backing plates are used because even though the West System epoxy is very strong, the butt joints represent a minuscule surface area compared to the mass of some of these bulkheads.  I feared shock loading these joint when it was time to turn the boat right side up.  Another important difference in the permanent bulkheads is the addition of sawn frames.  I was able to obtain cabinet grade quarter sawn white oak form Indiana at what I considered a steal.  Quarter sawing boards is a technique for cutting lumber from the log that keeps the grain perpendicular to the face of the lumber.  There is usually much more work, as well as waste, involved with this style of milling lumber.  Quarter sawn white oak is highly coveted for cabinets and some high end flooring.  When white oak is quarter sawn, flecking is revealed along the face which is very beautiful and justifies the extra expense of quarter sawing.  It is important for boat construction because wood primarily moves perpendicular to its grain when exposed to differences in moisture and temperature.  If the grain is at an angle to the face of the board this will result in cupping of the board warping of the structure.  In the industry we say that quarter sawn wood has much more dimensional stability than flat or rift sawn lumber.  After running these boards through the planer I was hesitant to cut these beautiful boards with their characteristic white flecking into the small curved pieces that make up the frames.  But I did.  The cut frames are so called because the wood is cut to the contour of the hull as apposed to bending (usually with the assistance of steam).  In this case the frames are six inches wide and made up of two laminated layers of four quarters white oak resulting in an actual thickness of 1.5 inches.  The rough stock did not require planing to 3/4" to true these boards so I ended up with an extra tenth of an inch in total thickness.  This actually saved quite a bit of planing time and created a stronger frame.  Due to the natural curve of the hull it was impossible to have a single board wide enough to create a 6" frame longer than a few feet so small lengths (as long as possible) were used.  I made sure to have plenty of overlap at the joints in the the second layer.  These frames are very important to the integrity of the vessel so I took great care in there construction.  I chose to use resorcinol glue in bonding the frames together.  Resorcinol glue is a two part product consisting of a liquid and a powder.  It use to be the standard in wooden boat building.  The glue forms a plastic that retains %100 of its strength in salt water down to 40 degrees (F or C).  Its an amazing product and also a little difficult to get.  It is considered a hazardous material and only one company still produces it.  It also must be weighed out in parts and will not cure in colder temperatures. Furthermore this glue requires a high clamp pressure.  Once I had a system in place, I found the glue very pleasant to work with although it goes much easier with two people.  Thanks Al Kuhn for the help.

The temporary bulkheads with the permanent ones in the distance.  You are looking toward the stern of the boat.

The first two permanent bulkheads installed.

Two permanent bulkheads with the two temporary ones in the distance.  This is looking toward to stem of the boat.

Yes, thats me standing proud in front of some finished bulkheads.  This photo is taken from the bow section looking aft.

You can see the two temporary bulkheads (1 and 4) and the permanent bulkheads with frames (2,3,5,6,7).  Obviously, placement and alignment of these bulkheads is very critical.  A six foot level was very handy for this.

A jigsaw was used to cut out all the frames and bulkheads.  The jigsaw was quick and accurate and required less "cleaning up" than the band saw.  I actually though I would be using my old bandsaw more often than I have.  It turns out the the jigsaw is more useful on these long graceful curves of the boat.  The edges were cleaned up with a belt sander or table top disk sander.  Once a bulkhead was completed with frames a final touch up with the belt sander created a very fair edge.  The next step was erecting them onto the jig.  Temporary 2X4s and 2X6s are used to help brace the bulkheads until enough longitudinals are installed that the structures is rigid.  With every bulkhead the boat took on more of its final character.  If you squint and look just right you'll start to see the hull lines.

The hull starting to take shape.  These are the erected bulkheads with the sawn frames attached.  This is bulkhead "G" (I think) looking aft.  You can see how the hull changes from a "V" to almost flat amidship.

The shape of the bow of the boat will primarily be fixed by the stem.  The stem is constructed of four layers of marine grade plywood and attaches to the above forward bulkhead.  A full sized pattern of the stem is available.  Nevertheless, getting the shape and placement correct was very difficult.  From the pattern, I made a full sized stencil of the stem out of 1/8" plywood.  Al's brother, Tom Kuhn, was visiting from Chicago and was excited about lending a hand in the construction of the boat.  I was pleased to have the help and set him up to cut out the plywood stem pieces from the stencil I made.  He managed to get almost all the pieces cut out before we heard the words "oopsy"  yes he said "oopsy".  He had over-cut a line and removed a corner that should not have been removed.  It was to be the first real mistake on the boat and its got Tom's name on it (there are plenty now with my name on it).  When a mistake is made on a large project a decision has to be made.  Through my experience I have found that if the mistake in anyway compromises the final result or requires a design change to prevent a compromise you are better off throwing the mistake out and starting over.  In this case the corner was cut off what would be a dead wood part of the stem with no structural function at all.  Its now filled with epoxy.  It turned out that once we faired to stem to its final size the corner was smaller than my fingernail.  Still, we had a good laugh about that (and still do).  The stem was glued and screwed together with West epoxy and bronze screws.  It was then lifted and bonded into place.

The newly installed stem.  There was no one around so I muscled this piece in place myself.   Once in place, I spent quite a bit of time getting it into the correct position and verifying that position.  Needless to say, this was one of the most critical parts of the boat.

A rear view showing the stem.  Temporary battens are used to help keep the bulkheads aligned.

You can really start to make out the contours of the boat now.  Note the temporary longitudinal that is keeping everything aligned.  Tools of the trade include:  The belt sander, hand plane, wooden mallet, metal rule, a box of silicon bronze screws and a box of drywall screws for temporary fastening.  Next to the belt sander is a scrapper that I made myself consisting of a plane blade attached to a nice red oak handle.  The blade is bent gently so I can cut away high spots or remove drilling burs in wood.  I also use it to clean up epoxy drips.  Its nice to have because I don't care if I accidentally hit a screw because I can resharpen it on the belt sander in 15 seconds.  It saves me from ruining one of my good chisels.