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Where is the best place to install a 45lbs battery, I am about to start wiring the boat,any advice ?
also what is the best length of shaft on the outboard. I am six weeks in and hoping to get the hull glassed in the next few weeks, before it gets to cold.

For my wiring on my Weekender (which I haven't run yet), I ran a plastic tube up the inside of the mast to use as a wiring chase for the mast head and "steaming" lights.  I also put another tube through the inside of the stem for the bi-colour light.  For the future electric motor, on the advice of an electrician aqaintance, I have a relay that I will install that will actually switch the power to the motor on and off.  Also, based on his suggestion, I did NOT run tubing/conduit from fore to aft as he thought it would trap condensation/water.  Instead, I just ran a string for later fishing of the wiring from the forepeak to the transom behind the seat-backs.

For a wiring panel, I put it inside the cabin on the forward bulkhead which means that I'll have to flip any switches from the cabin - perhaps not the brightest of ideas, but it put the switches close to where the battery will be.

I can't speak from personal experience, but common wisdom in the past has had the batter sit in the forepeak in front of the mast.  The extra weight up forward helps keep the bow down especially in choppy waves.

  Thanks Andrew, You confirmed the way I was thinking, adding the weight up front, thought I would have had more input on the wiring ? Received my fiberglass today which I found on Ebay, 8 oz  55 inch wide for $3.50 a yard looks great. I glassed the deck & cabin two weeks ago, but looks like will have to pray for an Indian Summer it is really cold today on Long Island. I just need a few nice weekends to get the hull glassed after that I don't mind working in the cold.

If you are thinking of an electric motor, one thing to start looking out for is a really long set of jumper cables to run power from the forepeak to the stern.  You want as heavy gague as possible to reduce energy loss and keep the wires from over-heating.  Jumper cables are a good source of that sort of wire - you just have to luck out on a set the right length.

I've got the battery in the forepeak which helps add some weight up there, sometimes I wish there was a bit more weight but that's life. She sails well with the keg of beer just behind the forward bulkhead but the only problem with that is she tends to get lighter as the sail gets longer. Must be something about physics going on there that I don't understand.
Now as far as motor shaft length what most folks do is add a retractable motor mount to the back of the boat. I have both a short shaft and a long shaft. With the short shaft I can lift the motor out of the water while sailing which reduces drag and extra noise. The short shaft is easier to find and will work just fine for you. Mine is an old 6hp evinrude that runs great and pushes the boat along at about 5.5 knots under full power. It's also pretty good with fuel consumption. I have a hard time using 6 gallons a year.
Good luck with the boat, it sure is coming along fast.

I agree: Battery or batteries up forward, really oversize cables for the run aft (we have used surplus welding cable on electric cars, but I don't know if you can find it in sizes like #2 or #0; #00 or larger would be overkill).

Mike

(09-29-2009, 05:05 PM)keith welsby link Wrote: [ -> ]Where is the best place to install a 45lbs battery, I am about to start wiring the boat,any advice ?
also what is the best length of shaft on the outboard. I am six weeks in and hoping to get the hull glassed in the next few weeks, before it gets to cold.

I've got two batteries in the forepeak. I've also got perminent wiring installed I ran 8ga wire back to a wiring block behind the seats in the cockpit and then ran 12ga pairs to every place that got power. There is actually 3 sets of 8ga wire. One set goes to the wiring block, and the other two are for a motor. I have a 24 volt motor and a 12 volt motor so I ran one set of wires for each motor type. I only ever used the 12v wires though so thats just been a spare set. There is also 2 spare sets of 12ga wire in case I decided I needed some new electronic devices in the front of the boat. So far, I haven't used those spare wires either. All my wires are bundled into a big wiring harness type of deal and I covered it with that flexible wire cover that you can get at ace. I did all the wiring underneath the port deck. Turns out all that wire is kinda heavy. Filling the starboard cooler with beer and ice just about  levels it out

  OK many thanks, I am going to go with two batteries up front & a short shaft outboard, I am sure I will have a lot more questions before I am finished. Keep up the good work.

Greetings Keith,

Calculating wire gauge sizes for a required amperage load at a given voltage using copper or aluminum wire and a specific insulation type operating at a specific ambient air temperature inside or outside of a conduit and allowing for only a small voltage drop as a percentage of the source voltage and accounting for acceptable derating factors is a royal pain in the ass.

In its simplest form these equations look something like this ...

CrossSectionalAreaOfWireinSquareMilimeters = 2 x LengthOfWire * AmperageDraw * WireResistance / VoltageDrop

For the Weekender, the LengthOfWire is about 15 ft.  The WireResistance per ft for the type of conductor can be looked up in a American Wire Guide (AWG) table.  For most 12 volt trolling motors, the AmperageDraw in amps is roughly the same as the thrust rating in pounds.  For 24 volt trolling motors, the amps is about 1/2 of the thrust rating.  Acceptable voltage drop for a motor is 2% to 3% of the source voltage.

Brain melting yet?

No worries.  Use this handy calculator instead ...

http://beta.circuitwizard.bluesea.com/

A reasonable set of values for a 45 # thrust trolling motor mounted on the stern of a Weekender with the battery in the forepeak would be ...

Circuit Voltage: 12 v
Load Current: 45 amps
Length of Conductor: 15 feet
Allowable Voltage Drop: 3%
Type of Load: Fixed
Wire Insulation Temperature Rating: 75 c

In Engine Room [ ]
Duration: 120 minutes
Terminated on Fuse? [ x ]
In Conduit or Sheath? [ x ]
Extra Thermal Insulation? [ x ]

Press the ( Calculate ) button, and the answer is ..

AWG 6

(We will assume that you installed the wires in conduit and that the conduit runs through a compartment full of foam flotation (extra insulation)    )

If you don't use conduit and do not encase the wires in foam, then the wire size jumps up to

AWG 8

Or, you could just run down to the local Bass Pro Shop, Cabella's, Dicks Sporting Goods, or wherever, and take a peak inside a one of those fancy new production bass fishing boat in the 16 to 20 ft range with the glitter paint job sitting all sitting on a matching trailer for a cool 20 large, sporting a bow mounted trolling motor, and you will find ...

AWG 6 wires

For the same thrust rating, a 24 volt system will use only 1/2 the amperage which would lead to AWG 10 for the above numbers (ie. Circuit Voltage: 24v and Load Current: 23 amps)

AWG 10 probably is not up to the task for 12 volt systems unless the battery is right next to the motor and you only use the motor for a short time, just to get away from the dock, etc.

If you are really cheap, use AWG 8.

I personally would just go ahead and use AWG 6.

Cheers,
Tom