Building Gigi - A 16' Outboard Runabout

[gordonscg]

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Hi. My name is Steve. I'm new to the Forum and this is my story of building 'Gigi' - a 16-foot outboard runabout based on Tad Roberts' Tokara design. I began thinking about this project shortly after launching my last boat, a glued lapstrake Saint Lawrence River Skiff, in 2020. Before that, I built a strip-planked William Garden-designed 'Tomcat' sailboat which I launched in 2016. I still use and enjoy both of these boats but I decided this time around I’d build something different, at least for me.

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[wizbang 13]

Re: Building Gigi - A 16' Outboard Runabout

Thank You for coming here with your build!
Bruce

[gordonscg]

Re: Building Gigi - A 16' Outboard Runabout

Choosing a Design

I reviewed study plans for about 30 different wooden outboard runabouts from a number of designers. My selection criteria were that it be: traditional in appearance, probably lapstrake, amenable to modern construction methods (i.e., glued lapstrake), small enough for my workshop but large enough to run safely and comfortably on moderate-sized lakes and rivers with 5 people aboard and, importantly, a design that really appealed to me. After a couple months of review and consideration, I decided on the Tokara 16 Speedboat by Tad Roberts (http://www.tadroberts.ca/services/sm...ng/speedboat16) and ordered plans.

Specifications for Tokara:

• Length Overall 16’ 1”
• Length Waterline 14’ 8½”
• Beam 6’ 6”
• Depth Amidship 32”
• Draft 10¼”
• Deadrise at Transom 7 degrees
• Displacement 1280 lbs
• Outboard 40-60 HP

[gordonscg]

Re: Building Gigi - A 16' Outboard Runabout

Hull Construction Method

Before I could get started building I needed to decide on a hull construction method. The plans for Tokara are pretty basic, with most of the details left up to the builder. The specified hull construction method is either traditional cedar lapstrake on bent oak frames or glued-ply lapstrake on laminated frames. I chose to adopt a hybrid approach used by the Great Lakes Boat Building School which built an 18-foot version of Tokara in ~2017 (https://glbbs.edu/projects/18-lapstrake-speed-boat/). They used composite strip-plank construction (edge-glued cedar strips sheathed with fiberglass on both sides) for the hull bottom and glued plywood lapstrake for the topsides. However, whereas the GLBB School used sawn plywood frames spaced about 20" apart, I elected to go with steam-bent oak frames spaced at 6". One downside to composite strip-plank construction is that if water gets into the wood core it can cause rot and the rot can spread undetected from the initial site of water ingress. Therefore, I tried hard to minimize the number of screw holes through the fiberglass and to carefully seal any screw holes that were necessary. The general hull construction approach I used for Gigi is shown in these drawings.

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[wizbang 13]

Re: Building Gigi - A 16' Outboard Runabout

Bottom part is edge nailed AND sheathed inside and out AND has lots of steamed framing??
I think your hybrid thingy may be a bit much.
for teaching, it's a "two fer", but super impractical
choose one

[gordonscg]

Re: Building Gigi - A 16' Outboard Runabout

The glued lapstrake construction option specified by the designer had 1 3/4" square laminated frames spaced 18" apart. My 5/8" x 1" streamed frames spaced 6" apart are my substitute for the laminated frames and will be more traditional looking. The strip planked bottom avoids concerns about damaging lapstrake plank edges below the waterline. My first boat was strip planked and my second was glued lapstrake so I have experience with both methods. I know this hybrid approach is a little more complicated and time consuming but it does offer certain advantages.

[willin woodworks]

Re: Building Gigi - A 16' Outboard Runabout

Why are gluing anything with 5200? Keep it away from your boat. Use epoxy.

[gordonscg]

Re: Building Gigi - A 16' Outboard Runabout

I am using epoxy for most of the gluing but I (or someone) may need to replace a frame some day. For this reason, I may actually use something a little less aggressive than 5200. A little flexibility between the frames and bottom also seems like a good idea.

[Autonomous]

Re: Building Gigi - A 16' Outboard Runabout

Five people in a sixteen foot boat is... how do you Americans say... Cozy? No... Tight!
If you haven't started cutting, suggest you contact Tad and see if you can stretch the boat by ten percent.
Arrange a temporary extension on the building space if you must.

[gordonscg]

Re: Building Gigi - A 16' Outboard Runabout

Lofting

After receiving the plans my next step was lofting, the main goal of which was to develop accurate and fair full-scale half-sections of each of the boat's nine stations and the transom which would be used to construct the molds and frames. I built a 4-foot high by 16-foot long lofting board on the wall of my shop - my knees were forever grateful - for the profile and half-breadth plans. I used a separate sheet of ¼” ply to loft the body plan. I followed the lofting methods described in The Gougeon Brothers on Boat Construction by Meade Gougeon, Building Small Boats by Greg Roussel and Lines, Lofting and Half Models by Walter Simmons. I also viewed several YouTube videos to clarify certain points. I won’t go through the lofting process as it is rather difficult to explain in writing and the sources mentioned above do a much better job describing it than I can. Except for a couple of very minor discrepancies, I found the offsets to be very accurate.

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Next, since the lofting was drawn to the outside of the planking, I had to deduct the thickness of the planking to get the accurate mold dimensions. Since I would be using ¾”-thick cedar planking for the bottom and ⅜”-thick ply planking for the topsides I had to choose where the transition between these would occur. I chose to use the upper edge of the ‘outlapped plank’ shown on the designer’s alternate construction plans. I marked this height on each station line of the body plan and drew a fair curve through these points. Now one more complication, in sections of the hull where the planks run fairly parallel to the centerline, it is generally acceptable to simply deduct the actual thickness of the planking, either ¾” or ⅜” in my case. But, in sharply curved areas, near the bow for instance, this will result in the molds being too large. In these areas, I used a device (dare I say contraption) described in Greg Roussel’s book to determine the correct plank deductions. Finally, I took the time to draw full size half-sections of the stem at each waterline and of the keel/keelson area at each station. These were helpful later when making the stem, keel, molds and frames and helped me get my mind around how these parts would fit together. Lofting and the plank deductions took me about 50 hours over nearly a month to complete. This included starting completely over from scratch once. I’m sure a professional boat builder could accomplish it in one or two days. Now, finally, I was ready to begin actual construction!

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[gordonscg]

Re: Building Gigi - A 16' Outboard Runabout

Construction Begins

I took dimensions from the lofting to make the laminated fir transom knee.
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I milled fir strips and laminated the inner and outer stems over the lofting. I planed the stem down to its 2" final thickness and partially beveled the inner stem.
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I laminated two pieces of 3/4" okoume ply to make the transom blank and cut it out using the transom expansion I did during lofting. I added a perimeter frame of 3/4" ply and cleats to support the motor well and transom knee. I cut notches for the shear clamps, seat risers and bilge stringers, taking into account the 12 degree rake of the transom.
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I made a permanent frame for Station 1 from pieces of 3/4" ply with 1/4" ply gussets at the corners. I made bulkheads for Stations 2 and 9 from 1/2" ply with perimeter frames and cleats. I epoxy-coated all of these parts and set them aside for the time being.
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I also made up blanks for the oak keelson and fir keel and a deck crown template. The work described here took me about 207 hours over 4 months.

[Christopher Morgan]

Re: Building Gigi - A 16' Outboard Runabout

Wow. This all looks fantastic. Thanks for documenting the process.

[Breakaway]

Re: Building Gigi - A 16' Outboard Runabout

Looks like she's coming along.

Thanks for sharing.

Kevin

[gordonscg]

Re: Building Gigi - A 16' Outboard Runabout

Molds and Cedar Strips

I assembled temporary molds from 1x8 pine boards for Stations 0, 3, 4, 5, 6, 7 and 8 using the ‘nail transfer’ technique described in Roussel’s book. I added 1x4 vertical supports to the center of each mold (except mold 0) for additional strength. A 1x4 cross spall was attached exactly 36" above the DWL. This cross spall would later rest on the side beams of the strong back. I drew the centerline and all waterlines and butt lines on both sides of the molds. I drilled a ½” hole at the intersection of the centerline and DWL. This hole would be used later to help align the molds on the strong back. Finally, I cut notches for the stem and/or keelson on the bottom center of each mold, using the full-scale half-section drawings I made during lofting. The 4th photo below shows all of the completed molds, frames and bulkheads.

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After assembling the molds, I ripped fifty-six 1 1/4" by 3/4" strips from 16-foot long, clear, vertical grain western red cedar boards for strip planking the bottom. Rather than trying to wrestle the boards through the table saw, I ripped the strips on saw horses using a circular saw fitted with a narrow kerf blade and attached to a sled set to cut strips to the desired width. The strips were cut square edged with no taper. I tried not to think about the cost of all the saw dust I was generating $$$. Making the molds and cutting strips took me about 47 hours over 1 month.

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[gordonscg]

Re: Building Gigi - A 16' Outboard Runabout

Strongback and Setting Up Molds, Bulkheads and Frames

I started building Gigi bottom-side-up as is common for many small boats. The strongback upon which Gigi’s hull was built was 4 feet wide by 16 feet long. I used 2x8s for the sides and cross pieces, 2x6s for the legs (the front leg was a beveled 2x8), a 1x6 center plank let into the cross pieces and ½” OSB gussets were added to the corners. I made sure it was square and level in both directions and drew a centerline on the center plank. I later added two 2x4 cross braces between the 2x8s to better support the center plank.

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I transferred the locations of the mold/frame stations shown on the plans to the side beams of the strongback and checked that they were square across the jig by measuring diagonals from the center of the jig at its forward end. I attached short 2x2s vertically on the sides of the beams at each station to support the molds/frames on the correct side of the station marks – forward of the marks on the forward half of the boat and aft of the marks on the aft half. I carefully centered each mold/frame on its mark and, using a plumb bob, assured that each was aligned vertically with the centerline. As a double check, I ran a taut string from the aft side of Station 2 to the forward side of Station 9 through holes I had drilled previously in each of the molds at the intersection of the centerline and the DWL. Where necessary, I either shimmed up one side of a mold or cut a shallow groove in the top of the strongback side beam so that the string was centered in the holes and the centerline drawn on the mold cross spalls aligned with the centerline of the strongback. I then screwed the molds to the vertical 2x2s to secure them in place. I nailed a batten across the molds to keep them spaced properly and added 1x4 diagonal bracing at Stations 3, 5 and 7 to prevent the molds from racking.

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I set the laminated inner stem and keelson in position on the molds and made minor adjustments to the notches and to the aft part of the stem to get a good close fit. I checked that the stem was plumb and temporarily screwed it to Mold 0 and to chocks on the strongback to hold it in position. This work took me about 24 hours over 1 week.

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