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Contructing a Motor Launch

Between September of 2005 and February of 2006, I re-activated my boat shop to build a new radio controlled boat.  Using lines found in Howard Chapelle's boatbuilding book for a 35 foot Utility Launch, the boat was scratch-built with the intent of using extra wood left over from previous projects.  Because of the left-over nature of the materials, the whole boat set me back less than $100.  Here are some highlights of the process of scratchbuilding a boat from lines drawing to completion.

Step 1 is to draw out the plans for the boat and start cutting material.  Here's a partial photo of the lofting that I drew by hand, using the measurements table provided by Mr. Chapelle.  To scale and draw the lines took several days to complete.  Also shown are some of the parts for the boat.  The frames are 1/8 inch balsa plywood (the light tan pieces).  The dark wood keel pieces are solid walnut, left over from a box-building project my father started, but never completed.


Making the keel took six separate parts.  In the bow, I simply didn't have a wide enough piece of wood to cut both the stem and keel as one piece, so there's a stem, knee and keel.  In the stern (pictured here) the propeller and rudder had to pass through the keel.  In a normal boat, this would be drilled out, but since these shafts were almost the same width as the keel material, I drew the width of the shaft housings (brass tubes) onto the pattern for the keel  parts before cutting them. The keel was then cut to take out the areas where the tubes were to be placed and then epoxied the parts to make a complete keel.  To maintain the color of the wood, I mixed in walnut sawdust saved from sawing the keel and mixed it into the epoxy.


The keel was cut with slots for the frames to fit into, but sometimes things don't quite work as planned.  This is frame #8 (the one behind the frame propping up the plastic envelope) that's sitting too low on the keel; remember the boat is upside-down here and we're looking forward.  Frame #9 is slightly out of alignment, too. 


After several work hours finessing the frames into the right alignment, all of the wayward frames are now in place.


In this photo, the keel, frames, sheer and chine clamps are assembled.  Notice the extensions glued to each of the frames; this was how I maintained proper hull alignment without a support structure like a strongback.  The frame is now completed and ready for planking.  If you go to the website of the guy building a full sized version of this boat, you'll see a photo that looks a lot like this one.


The balsa wood sub-planking is now completed.  You can just see the herringbone pattern to the bottom planking that was called for by Chapelle's plans.  Placing the planking at this angle simplified construction because the angle of the herringbone compensated for the curve in the bottom.


Here the final mahogany planking for the bottom is complete and the sides are started.  The mahogany is 1/32 inch veneer, used for facing cabinets.  I'm using fast-set "super" glue to attach it to the balsa.  Note: if you try this method of planking (and if I try it again) start at the middle of the boat and out out towards both ends.  Planking from the bow back introduced a fairly severe upwards curve by the time the planking reached the middle of the boat.  This could also prevented by "spiling" the planks (varying their width), but that's a skill I'm still learning.


Here's a detail of the hull contruction.  Looking outboard from the last frame, you'll see two 1/8 square lengths of basswood that are the sheer, the 1/16 inch balsa base planking, then the 1/32 mahogany outer planking.  This is similair to how real-life mahogany runabouts were built and makes for quite a strong boat.


This boat is roughly 30 inches long, but it doesn't have a lot of interior space so all the control electronics had to fit into the deckhouse.  The red box on the right is the motor speed controller, and the male and female plugs are the connection between the battery and the motor controller.  The empty battery holder, switch, screws and loose wires are all for the lights.  The twisted red and black wires are for the controller's on/off switch, which is the red colored switch behind the lights batteries.  The radio receiver is mounted on the underside of this tray, towards the rear.  At the extreme left are the heavy gauge wires that carry electricity forward from the main battery and aft from the motor controller to the motor.


This is the deckhouse nearly completed.  Note the heavy wires that carry the electricity from the battery mounted in the stern to the speed controller and then back to the engine, which is mounted amidships.  In addition to the working door, the upper hatch slides on rails to allow access to the batteries and switchs.  Also visible is one of four blocks and the line used for rudder control, as shown in Mr. Chapelle's plans.  This line circles the boat and connects the rudder to a bar that tilts fore and aft to turn the rudder.


This photo was taken slightly earlier than the previous shot and shows the center of the boat.  You can just see the lower corner of the main battery in the background and the string that boxes the engine is part of the steering system.  The control is the vertical stick on the left, which is connected to the rudder via four blocks (pulleys to you landlubbers).  This is the system that is shown on the plans for this craft and it works well in scale.  In the forground is the framing for the aft end of the deckhouse, before the walls were planked using the same double-layer process as the hull.


One of the last big jobs was the hand carved name plate.  Done in solid walnut, the shape and lettering was generated by a word processor.  I used a light coat of paper glue to tack it to the wood to use as the template to starting carving from. It took several nights of carving to finish it, and it turned out to be one of my favorite sub-projects for this build.  Then the letters were painted white for contrast, and the whole thing was given several coats of marine varnish.  In the picture below, the letters are painted, but the varnish hasn't been applied.


Here is the boat almost done. The deck is home-made balsa and maple plywood, and the engine cover is mahongany planked.  It also shows the limited workshop that I have, due to the relatively small condo I live in.  The scale flags are the Power Squadron ensign and the burgee of the San Diego Sail and Power Squadron.  I happen to be a member of that organization and the Seamanship instructor, which allows me to fly them.  If you're at all interesting in real boats, I can highly recommend the Power Squadron as the place to go to get involved in boating of all sorts.

Click here for the Power Squadron's homepage.


Here's the completed boat.  In addition to the working doors and hatch, it has working forward navigation lights, stern light and two interior lights.  The project ran from September 3, 2005 to February 14, 2006 and I probably spent 8 to 9 hours per week on the project.  Unlike my first projects that seemed to have one impossible problem to solve a week, this project went fairly smoothly, with only a few problems that made me think the project was doomed.  Hope this inspires you to go out, build a boat and take it to the pond.  Hope to see you there.


A final note: I finally floated this craft (3(!) years after building it) and found out the rear-mounted battery weighs down the stern a bit too much and since the bow is sealed, I can't get ballast far enough forward to balance the craft.  The plans for this boat do warn against mounting the engine too far forward, but it's also sensitive to aft loading, too.  At one point, I tried splitting a 6 ni-cad C-cells between the aft and forward compartments, but the modified pack didn't work; I might've cooked one of the batteries while soldering.  If anyone finds lighter batteries or a better place to store them, please tell me. 

That's not all, go visit Anest Yachts by clicking here. He's building a real Chapelle 35' Utility.

Click here to see a racing sailboat.