Grapeview Point Boat Works' 21 ft. 3 in. Electric Launch
Based on a design by Nelson Zimmer
- Length x beam
- 21 ft. 3 in. x 7 ft.
- 21 in.
- 3200 lbs.
- 12 people
- 6 hp Electric Inboard with 15” x 12” prop, 48v 8.6 KWH Battery Bank
- Battery Charger
- Fully Automatic, onboard, 120-240v 15A input, 25A output
- Recharge time
- Less than one hour for each hour discharged
Our motto is "Everybody Needs a Boat" and that applies to us, too. We are building this boat for ourselves and expect to have her complete in the summer of 2013.
We wanted a boat to take a dozen friends on a quiet cruise along the shoreline.
Our ketch, Twilight, has no room in the cockpit for guests.
Our runabout is too noisy for a conversation, and only has the capacity for four adults.
We needed another boat!
Electric propulsion would be perfect for this boat’s purpose.
We've created a chart
displaying performance data.
We chose to build a modified version of Nelson Zimmer’s 21’ Utility Launch. This design was originally drawn for use as a fishing camp tender on the Great Lakes, so it has a higher bow and greater freeboard than many other launches that are intended for use on more protected waters. We began building Grace in late 2009, and construction took 17 months, working mostly weekends and evenings.
Because we planned to entertain guests on Grace, we wanted to have as large a cockpit as possible. We achieved this by eliminating the cabin and raising the cockpit sole 1 ˝” to allow the batteries and motor to be entirely beneath the floorboards.
For power we selected a 48 volt brushless DC motor turning a conventional propeller shaft through a 2.8:1 reduction gear. The motor is rated at 6HP continuous, and easily gets the boat to hull speed, about 6.2 knots. We have a fairly small battery bank installed right now. It provides about 30 miles range at five knots or 45 miles at four knots. There is plenty of capacity to install a larger battery bank if the need arises, but the existing bank is fine for our intended use.
The batteries are recharged with an on-board charger that can run on standard household 120VAC, or 240VAC. The lithium-iron phosphate (LiFePo4) batteries are expected to be able to be recharged 2000-3000 times, depending on usage.
Instead of the carvel construction shown on the plans, we built a lapstrake hull with okoume plywood planking on bent oak frames. The floors are also oak, with sapele backbone and transom.
We just completed a canopy for Grace. It covers the entire cockpit and feature windows all around, making Grace an all-weather boat.
Here are some photos detailing the construction of Grace.
Backbone and transom frame of the launch. Propeller shaft and stuffing box being fitted.
The first few strakes are hung on the bent oak frames
The launch rudder with mockup of the proposed propeller. Rudder heel bearing is supported by 3/8" bronze plate.
The interior of the launch takes shape. Temporary wooden knees hold the coaming pattern plumb.
The interior of the launch
The center sections of the plywood cockpit sole are removable for access to batteries and motor.
The jog in the hatch outline allows for a future enclosed head when the rigid canopy is installed.
The bin to port opens to reveal the depth sounder and watt hour meter. A drawer is to starboard, below is a shallow locker for the AC distribution panel.
The oak planksheer is being fitted. Wicker furniture was often used on the early electric launches. It allows configuring the seating to suit the number of guests, and allows everyone to face the view.
There is plenty of room for seating and tables for eight, plus a helmsman who typically sat on a wicker stool.
The aft deck is strip planked with sapele.
The completed aft deck.
The forward section of the coaming is bent over a trap, then fitted to the boat when cooled.
The entire length of the stem and keel is protected by 1/8" bronze plate cut to shape. A mock-up of the port and starboard steps is being tested.
The 5/8" coaming was bent in cold, and carefully fitted to be plumb along its length.
The steering is via cable and pulley. The cables will exit the bulkhead and run aft just below the coaming. The throttle control is to starboard.
The construction is complete and is currently being prepped for paint.
Have questions or comments? Send us an email
at boat_works @yahoo.com.
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