3/16/13 - Laminating the Stem

Well the snow is still piling up here... woke up to another six inches of fresh powder snow this morning.

Lots to talk about this week.  First off I was pleased to determine once and for all that no modifications to the motor well will be needed to mount a new 50 HP Honda (or 60 HP) 4-stroke outboard motor, nor for mounting a 50 HP Yamaha 4-stroke.  I had been feeling a little vexed by this.  I felt certain that I would have to make the well bigger to fit today's 4-stroke engines.  But it seems that a 50 HP 4-stroke should fit in the well per spec.  

Early this week I went to a local marine dealer whom had a boat in their lot which had just been displayed at the Duluth Boat Show.  Up till now, there weren't any boats around for me to look at since its off-season. This boat had a 50 HP Yamaha 4-stroke and was soon to be picked up by its new owner whom had just bought it at the boat show.  They let me take a close look at the motor.  I made a mock up of the motor well out of ¼" plywood, and clamped it around the motor to the transom.  The mockup fit nicely around the motor.  I could turn the motor from side to side with plenty of clearance from the motor well mockup... nice!  However, power from the battery was not available so I couldn't be certain if the motor could tilt up 100% without hitting the transom, but visually it appeared it would not.

Also worth mentioning, I came across a link to Joest Boats at the Simmons Sea Skiff website.  In one of the Joest Boats website pictures I noticed a 60 HP Honda 4-stroke powering a commissioned Simmons Sea Skiff 20 with a big cabin which the owner, Skip, had built.  I wrote to enquire what, if any, motor well changes he may have made when building the boat.  Skip was kind enough to call me back and share that he built it his motor well to spec and the Honda just fit.  He told me that he mounted the splash guards per specs too which did their job perfectly.  I was grateful for his call.

After scrutinizing all this information I decided to build to the motor well to spec with the exception of changing to a 12 degree angle for the motor mount as specified by Honda rather than 11 degrees per spec.

I was curious to know the weight of a commonly used outboard motor from the 1950's and 1960's that may have been used on this boat "back in the day".  So I did a quick search on Google for a Johnson Sea Horse.  I found this beauty , a 1958 50 HP Johnson Super Sea Horse that weighs in at 175 lbs.  That's about 40 lbs lighter than a new (2013) Honda BF50D 4-stroke and a whopping 74 lbs lighter than a new (2013) Yamaha F50 4-stroke.

I got back to work in the shop and milled the keelson and bottom stiffeners to size being careful to get the thickness of the bottom stiffeners to the exact depth of the floor notches so that they fit flush with the floor's bottom edge.

The Vertical Grain Douglas Fir scraps made for some excellent quality and badly needed battens.  I used a few of them to check for fairness of the floors.  Both the bottom and the chine edges looks to be very fair.... just a few very small adjustments to make.  I'm quite happy with that.  Dave Carnell's floor dimensions in the plan set are proving to be quite accurate.  

This week I also started on the stem and began the lamination process.  I decided to take Ellis Rowe's lead (WoodenBoat Magazine issue #186, page 31) and laminate a stem out of thin strip Mahogany.  His recommendation seems to me to produce the strongest stem.  I purchased 3/8" thin strip mahogany stock and cut it into 10 2¼"wide pieces.  I initially thought I would just bend them with clamps into a mold and epoxy them together.  But after cutting the strips to size I felt they were a little too stiff.   So I decided to bend them to shape prior to lamination by steaming them.  

Here's the process I followed for laminating the stem.

First I made a template out of ¼" plywood from the full-size pattern drawn on the plan set.  Using the template I constructed a bending jig.






Then I milled the thin stock into 10 2¼"wide pieces.

Next, I set up my small steam box (I made a simple steam box similar to this) and used an electric steam kettle to generate steam.  While this steam kettle was effective, it took a long time to get the steam box up to temperature. In the future I intend to make a steam generator as described in Don Danenberg's book  "The Complete Wooden Runabout Restoration Guide" which he calls "The Danenburg Steam Generator".  I used a steam generator at boat building school that was made like this and it worked great.








After steaming for about 20 minutes, I took them out and quickly bent them to shape in the bending jig using clamps to hold them in place overnight.  The next day I took them out of the bending jig and spaced them apart and let them sit overnight to dry out.  I did this to avoid encapsulating excess moisture in epoxy during the lamination process.








Next I mixed up some thickened epoxy applied to both surfaces of the strips and reclamped them back into the bending jig lined with wax paper.