"Twilight" an electric boat [Archive]

g.maclaren

07-29-2008, 07:15 PM

It has been suggested I start a new thread.

Here's the idea:

Design and build a "stitch and glue" boat to be powered by an electric motor.

The boat is to be used for quiet, probably evening, cruises on fresh water lakes, hence its name; "Twilight."

The boat will usually carry two adults, each in a comfortable seated position. Passengers will face each other.

The boat will fold in half, or possibly come apart in two pieces, for storage and transport.

Launching will usually be done from a pier.

To exploit "hull speed" advantages, the LWL will be about 20 ft.

Maximum width will be about 30 inches, less if practical.

Cockpit will be 20 inches wide at seat back -- same as my office chair.

Batteries to power the boat will be low in the boat, keeping CG low.

Consider flooding fore and aft sections of box keel.

Current (7/27/08) model shows 10 inch high sides on hull, plus 10 inch deep box keel. Can sides be lower? Maybe 8 inches?

Decks will be crowned, if possible. This might inhibit folding, and might suggest the boat come apart in two pieces instead of folding.

Boat will have a "box keel," wide enough for comfortable placement of passenger's feet -- and to house batteries low in the boat. Current (7/27/08) model shows depth of box about 10 inches.

Boat to be powered with a 40-pound thrust Minn Kota trolling motor.

Not sure yet if motor will steer boat, or if a rudder will be added. Experience shows a rudder system might provide for sturdier motor mount.

Boat will have white hull and "natural" decks, and of course, provisions to fly ensign at stern and owner's burgee at bow.

Storage for a wine bottle and a rack for two wine glasses will be provided.

Photos of a "concept model" have been posted on this website.

Updates will be posted both here and at

www.grantmaclaren.com/twilight

I've built a few small boats, but this one will be of my own design and concept (I think!) I'm looking forward to comments and advice.
Thanks!

Fanie

07-29-2008, 11:00 PM

The trolling motor will steer just fine. I had a big canoe I made a centre hole in it with a little transom where the trolling motor mounted on. It worked very well, the trolling motor was comfortable to steer (better than side-mount) and easy to lift in the shallows.

There was only drawback on the canoe I had. The bottom was smooth, so when you turn it side slipped a bit. Having a couple of small strips on the bottom would solve that. Mini-keels.

I would suggest maybe two batteries (and oars). The 24V trolling motors draws less current than the 12V ones, so the batteries last somewhat longer.

Oh yes, it is not always much fun when these things roll over. I would be carefull not to make it too narrow.

You can shape the hull so that it is a bit wider outside the water for less drag, but when it rolls it would resist that. I would say that 700mm is ok for a minimum for the in the water part. I like the length... 6m is going to be ok.

Could I suggest a little 'table' between you... hold the bottle and the glasses for a hands-free.

A foot control steering could also be very comfy. Paddle left paddle right.

g.maclaren

07-29-2008, 11:15 PM

Hi Fanie,

Here's a video of our first electric boat's steering:

http://www.youtube.com/watch?v=qu4xPA-z42o

Intend to use two 6-volt deep cycle batteries as used in golf carts.

Don't want to think about roll-overs, but plan to use "dry" batteries just in case.

Love your table idea!

We like our steering. Push/pull rod with friction hold.
It's very simple and works great.

Worked on displacemnt calculations tonight. There MUST be
some changes made:

www.grantmaclaren.com/twilight/displacement.html

Boston

07-29-2008, 11:22 PM

if its only an occasional user u might think of throwing a few solar panels on it to help keep it charged when your out earning your keep

I was kicking round the idea of using twin electrics instead of diesel
In a live aboard sailer Ive been planning forever
( I hate the smell of diesel )
and power them with an alcohol fueled generator and a battery back up with solar assist
( I love the smell of alcohol )
now granted the solar assist wont be much
but in a pinch it might keep the lights on

I like the idea though
it could be that a small generator would still afford you that piece and quiet you are after and still augment the battery pack
when needed

B

Fanie

07-29-2008, 11:52 PM

Solars make a big difference in how your trolling motor holds out. Used to have a 2A jobby on my previous boat and it does help. Unfortunately solars are very unefficient and expensive. But then they do work every sunny day ;)

You can't go and waste alcohol on motors, good gried B, what kind of a person are you ?

Guest625101138

07-30-2008, 12:40 AM

Grant
What is the capacity of the batteries you plan to use?

How long would you want to cruise at design speed on any one charge?

If you give me these conditions I will provide an optimised hard chine hull for the box keel. It will be based on your displacement figure, 90% battery discharge at 60% overall propulsion efficiency. Would be possible to do better than this but not with a trolling motor. Going slower than design will increase the range.

I am thinking the faux-tri concept that ASM has proposed is the best option here. There are a few variants around now. The last one was this 20ft canoe:
http://boatdesign.net/forums/attachment.php?attachmentid=22533&d=1213778526
It is low drag because the main hull is so narrow. This was a 5-minute exercise so is rough around the edges but gives you an idea.

The advantage of the fauux-tri is that you can go beamier for stability without suffering increased drag. It also is an inherently strong hull for carrying concentrated loads like batteries.

For the folding requirement I think you would be better off having a solid middle section of say 10ft with two smaller sealed fore and aft sections. The stabilisers for the box keel would be part of the central portion.

Rick W.

Boston

07-30-2008, 01:34 AM

well ya know Im just thinkin luck favors the prepared
if its sunny
Im drinkin
if its shady
Im paddling and drinkin
if Im dead drunk
I can breath into the gas tank

what kinda guy do you think I am

B

Guest625101138

07-30-2008, 05:34 AM

Grant
The most important part of the attached is the underwater portion of the central hull. I looked at the Minn Kota 40lb and saw that it was rated at 42A. So taking the 12V battery and allowing a bit I am working on it requiring 480W. Allowing for all the inefficiencies I am working on 280W for the hull.

So the constraints I tested were square chine, 260kg displacement and design speed of 3.5m/s. As it turned out it will take a bit more than 280W to do 3.5m/s. The target is hence 6.7 knots. The Minn Kota may not be suitably propped to do this but it should go close.

You can see the main hull is very simple. Almost flat rocker. I have left a little V in the bottom but you will not lose anything to make it flat. Forcing a slight curve prevents it from pumping.

For the boat, I have thrown together a concept with central hull and two 100mm wide outer hulls set up to just kiss the water at design draft. The overall beam is 1m. This will be a very stable platform. You could make like a 3-sided seat so you can face either side as well. I have not done the stability anaysis but I expect two people could sit on one side without tipping it.

The bow and stern sections could be produced as sealed spaces. Possibly hinged at the deck to fold into the main cockpit or be easily detached. I expect they could be stowed inside the cockpit for storing and transport.

Anyhow this is a concept that does not compromise much in performance for stability and load carrying capacity. I think it requires 11 surfaces so is not all that complex to build. It is about 30 minutes work for me to draw so not too much thought.

If you like the idea then you should build a small model just to see how it looks. Cardboard would do.

ASM, of this list, is in the process of building a large model of a solar powered version of a larger boat using the same concept. He has not updated for a while but you could find out how he is going.

The FT in the file name is for faux-tri to distinguish it from what you may eventually arrive at.

At 5kts it should draw about 16A. So I expect it will have an impressive range on 120lb of batteries.

Rick W.

g.maclaren

07-30-2008, 07:00 AM

Hope I'm using this "Quick Reply" feature in the correct way. (I'm a newbie to boatdesign.net.) Anyway, my experience with my first little electric boat tell me battery life will not be a problem with this new boat. I've managed nice little cruises with a 12 v. Wal-Mart car battery with a less efficient motor than the new Minn-Kota. A solar panel would be a nice talking point, but doubt if I'd notice any difference in real performance. Thanks to all, esp. Rick for the tri-hull concept dwg.

Have you seen my displacemnt "study?" It show me two things.
1) The boat as I've designed it would bob like a cork and maybe turn over if at anchor.
and
2) I'm no marine architect!

I'm now thinking about building the boat in three sections rather than two.

I'l be posting more later today or tomorrow. Later today I'm taking the little gren boat to a nearby lake, meeting the local kayak club for a "show and tell."

Thanks all!

Guest625101138

07-30-2008, 05:52 PM

Grant
I looked at a hard chine monohull having reasonable stability to compare with the FT above.

For the same power it is 0.5 knot slower. So not a huge compromise. It would be easier to build. Just 5 main panels.

The KMT is 490mm and beam is 760mm. It would be very similar to what you have drawn in the original post. Loaded draft is 90mm.

I still think you would be better off making 3 bits, leaving the central portion intact. This needs to be a strong structure to support 120lb of batteries and two people.

Rick

g.maclaren

07-30-2008, 07:58 PM

Rick,

Thanks.

I'll try to find more RE: KMT. Are there photos on
this site?

I've also been thinking of cutting my little gree boat in
half (after installing "transoms") and using those two
pieces for the two end bits.

See "little green boat" at

www.grantmaclaren.com/zac

I've also made the "concept model" waterproof
and having two fellows look at it floating.
Doubt if we learn much. i have a bit of
confidence in my calculations.

-=Grant=-

g.maclaren

07-30-2008, 08:34 PM

Rick,
I've added a retouched photo to original post.
It is me in my 14' "little green boat" (below) and the same
photo retouched to show a 20' version.
(i.e., add the ends of the original boat to a new center section
with box keel for batteries and feet.)
-=Grant=-

Boston

07-30-2008, 10:22 PM

the box keel sounds great

one additional thought
a simple pond pump under the batteries could end up handy in a pinch
might save unloading those batteries any more than absolutely necessary
B

Guest625101138

07-30-2008, 11:16 PM

Grant
I am getting the impression you do not like the FT idea. You want a more conventional looking boat just a bit bigger than you have,

How do you plan to transport?

Also what is the size constraint on a single hull component for the hull.

If you are going to do a nice job I think you would find problems matching to the old hull.

KMT means transverse metacentric height above the keel. You need to have your CoG lower than this for initial stability. I would think your current boat has KMT around 400mm so possibly on the twitchy side to stand in.

I am not 100% certain of the box keel idea you have but if it is just under the feet, therefore quite short, I think it will impact badly on performance. If you are keen on the box keel idea then the FT idea is the best variation of that as it maximises the waterline length. A shorter box keel will create a nasty protrusion making for problems with draft and transport compared with a nice straight keel line.

Rick W

Richard Atkin

07-30-2008, 11:59 PM

Hi Grant, I like the idea of a quiet canoe ride facing my girlfriend, chatting and eating crackers and stuff....very romantic and fun.
I would be more concerned about stability though. If you are not using paddles, and there are two people making separate movements, and you are momentarily distracted, then the chance of capsize is quite high compared to normal canoeing.
Just a thought

Boston

07-31-2008, 01:00 AM

I also like the concept
30" seems a bit narrow to me to
Ive had canoes wider than that
and spent my share of time swimming
although with a hydrodynamic ballast box for the batteries
you will gain some stability
does it have to be a mono hull
a simple outrigger would solve some of your stability problems
might keep a late night moment of affection
from turning into a late night swimming lesson
:-)

(

g.maclaren

07-31-2008, 10:45 AM

Rick,
I do like the FT idea, but can't imagine it being built by me.
I'm too impatient and don't really enjoy the building.
(If I could buy a boat to fill my "needs" (desires?), I would.

I also like the idea of making the center section larger and adding
two sealed end sections. That get the "dividing line" out of
the cockpit and might make the two end sections easy to build.

I am not al all concerned about using the Minn Kota trolling
motor, esp. with larger capacity batteries. The old motor first
used in my little green
boat has had powered cruises of 1.5 hours and when I return to
the pier, the charger does its job. The 12 v. battery is
a car battery. So with better/more batteries and the more
efficient Minn Kota, electric power is no problem in this
application.

From what I've read, golf carts use 6 v. batteries, so I'll
get two of them and hook them up in series. With the Minn-Kota
40# thrust motor supplied by two deep cycle golf cart batteries,
the power and drive problems are solved.

I might consider steering with a rudder, but that's another issue.
I managed to break the vertical shaft of the trolling motor BUT
that's because I was using the boat in a shallow lake -- not in the
water for which Twilight is/will be designed and will be used.

My big problem is hull shape. I want keep the batteries low.
I want to sit with "feet on the floor."
I want the boat to look kinda elegant -- reminding one of a
late 1800's or early 1900's launch.
I think low freeboard and plumb stem and stern and double-
ended hull satisfies this. The decks do, too -- and may be
useful if a wakeboarder is on the lake at dusk.

Transportation is not really a problem. I have a boat trailer for
my Four Winns I/O and it could be used to get TWILIGHT to the
lake for long (1 to 2 week) stays. Having a 20 ft. long hull to store
is a bit of a problem. But even if it didn't come apart, I could
deal with storage, too. If I decide to leave Twinkle at the lake,
having it come apart in sections of less than 10 ft. would be
helpful.

I'll continue to think about the original concept (folding in
middle) but am now leaning toward a larger center section with
comfortable cockpit and the two end sections added for a longer
hull and associated aesthetics.

I am not too concerned about stability, but would like the boat
to float nicely with no passengers aboard, ie, moored at the pier
between cruises. But even this is not an absolute requirement.
I can pull the boat onto the pier, leaving the motor and prop
hanging off the end of the pier.

-=Grant=-

g.maclaren

07-31-2008, 11:47 AM

"I can always pull the boat onto the pier."
This shows the little green boat with its motor pulled onto the pier a few weeks ago when the water was very high and the lake was under a "no wake" order.
-=Grant=-

g.maclaren

07-31-2008, 02:36 PM

Maybe I should just order one of these:

http://www.ElectricCanoe.co.uk/pictures.htm

(His motor mount look just like mine.)

Seriously, Twilight should be a boat used much like
I'm sure this one is used. So, can a simple, cheap
version of this canoe be made that meets my desires?

I'd rather have something that looks less canoe-like

Tiny Turnip

07-31-2008, 05:06 PM

Hi Grant

I've posted a picture and link of Swallow boats 'Winsome' on the pedal powered boat thread here. (http://www.boatdesign.net/forums/showthread.php?p=218466#post218466) Post 61 I think. While a different power source, and not quite as skinny as you are proposing, It might capture a little of the ethos of your concept?

Guest625101138

07-31-2008, 08:26 PM

Grant
I don't think you would find building the FT too difficult. It might make sense to keep the centre section within a length suited to ply. If you can stitch and glue it would not be too difficult. It is possible to make cutting plans from the hull design I have. If you can fit two seats and table in the middle section at 8ft then the two ends become 5ft each.

The long central hull is 16" wide as the maximum so would be fine for standing in. With the outriggers as shown I would expect you could stand on the sides as well.

The boat will sit flat in the water with the two batteries stowed.

I would be looking at setting the drive up beside the rear seat hanging down off the wing. This way it only needs to be deep enough to get the prop under water. Have offset propulsion on a long slender hull like this does not reduce performance in a measurable way. I think it could also be used for steering from this position.

The actual shape of the hull is not super critical. It is very simple so would only take a few hours to mock up in cardboard so you get an idea of what it looks like.

Rick W.

g.maclaren

07-31-2008, 08:51 PM

Hi Grant
SNIP SNIP It might capture a little of the ethos of your concept?

Hi Tiny,

That is does. I visited their website

http://www.swallowboats.co.uk/content/view/94/104/

and found it also uses water ballast to trim for light, or no second person aboard.

Nice.
Thanks,
-=Grant=-

g.maclaren

07-31-2008, 09:12 PM

Rick,
Just returned from a 2 hour cruise on a small local lake. As usual, there was much interest shown in the little green boat.
The motor worked fine and I did not hit any stumps, etc. -- so brought it back in one piece.
I had just about decided to make a model of a most simple hull shape (I'll make a sketch and post it here within 24 hours.) but have decided to first try to model the FT hull you posted as a pdf.
I'll try using luan ply, 1/4 scale.
Maybe before I start cutting wood, I'll post sketches of the components.
Do you think there is a way to "hide" the shape of the boat in plan view?
To make it look more "old timey?"
I'm also going to post a new page (tonight) at www.grantmaclaren.com/twilight

-=Grant=-

PS -- The two images here show the first model with waterproof seams.

g.maclaren

07-31-2008, 10:45 PM

Rick,
Could the beam of the FT's main hull be 20 inches?

I think it be more suitable to my building skills to
just make it a real "tri" and have the small hulls
be supported by (round or square) aluminum tube.

Width of passenger's bodies would have room within
a 20 inch beam and I would not have to build those
beams with their intersecting curves. I'd make a mess of
that, methinks.

There could also be a "table" supporting the small
hulls. I've tried to show that in a sketch below.

The monohull idea came to me while cruising
this evening. The dimensions are more suitable
to ply sizes and the sloped "transoms" might be
extended as seat backs. Eight feet would give
plenty of room for two. The box keel is shallow,
so batteries would be in the center of the center
section and the passengers would have to sit
lower than I would like.

Guest625101138

08-01-2008, 06:31 AM

Grant
I have tried to make it look more conventional. The various images will hopefully give you a better idea of how it goes together.

The colour scheme is to distinguish pieces. The main hull and seating pieces would be maybe 7mm ply. The deck and outriggers would be 4mm ply. You would need some bulkheads and some trim to get the shape and stiffen it up.

I expect it would be quite heavy. Say 100 to 120lb. I would need to do more detail to get it more accurate.

If I get time over the weekend I will look at the box keel.

Rick W

Guest625101138

08-01-2008, 10:00 PM

Grant
Here is the box keel version.

Its initial stability is a bit twitchy but it stiffens up quickly so I doubt that it would roll easily. I have not done a stability check but with 120lb of batteries low down it will be stable enough.

It has similar performance to the wider canoe having the same beam, which is about 0.5kt slower for the same power than the FT.

Obviously this is quite simple to build. If it is going to be in parts I would still suggest a middle with two ends.

There is a variant of the box keel that I have called FT2. I have raised the floor to be almost clear of the water. It means just the chine submerges so it is similar to the FT. It performance is almost as good as the FT.

Rick

kengrome

08-01-2008, 10:13 PM

My big problem is hull shape. I want keep the batteries low.
I want to sit with "feet on the floor."
I want the boat to look kinda elegant -- reminding one of a
late 1800's or early 1900's launch.Grant, this doesn't look like the launch you mentioned above, but it looks good to me nevertheless -- and it has an excellent box keel and is human-powered which makes it ideal for repowering with a trolling motor and a couple batteries:

http://www.jemwatercraft.com/proddetail.php?prod=Buccaneer

http://www.jemwatercraft.com/images/prodimages/Canoes/Buc/BucIsoTop-400.JPG

The plans are only $52 and it's design makes it an exceptionally strong and stable boat with that box keel bottom and built-in 'sponsons'. This one is 32 inches wide. The designer has a larger version too in case you think this one's not big enough.:

http://www.jemwatercraft.com/StudyPlans/BuccaneerXW16StudyPlans.htm

http://www.jemwatercraft.com/images/prodimages/Canoes/RecCanoes/Buc/BucXW1.JPG

Obviously the interior would be of your own design, but these hulls are virtually guaranteed to be strong and stable, and they come from a well known designer of human powered boats -- just like Rick only different!

g.maclaren

08-01-2008, 11:04 PM

Rick and Kenneth,
It's late, just returned from a car show.
(Displayed my SOUPER:

http://www.grantmaclaren.com/oldfordstuff/souper/index.html )

Much to do tomorrow away from here.
I'll post more soon.
I like Buccaner.
I like FT2.
Be back soon.
Thanks!

g.maclaren

08-03-2008, 10:45 AM

Rick (and others),
Did you notice on the website mentioned in "I want one of these" post that the designer says his electric powered version is coming soon?
See
http://www.autocanoe.com/
-=Grant=-

g.maclaren

08-05-2008, 09:27 AM

Only to keep this thread alive, I am posting a recent photo of my 1/4 scale model in water, loaded with rocks.
I'm trying to develop a quick and easy waterproof joint in luan ply and think I've found a solution. It uses the paper tape used in adding machines and Titebond III glue, then house paint.
More to come soon.
Please stay tuned.
Busy with other project right now.
-=Grant=-

kengrome

08-05-2008, 09:58 AM

I'm trying to develop a quick and easy waterproof joint in luan ply and think I've found a solution. It uses the paper tape used in adding machines and Titebond III glue, then house paint.Yes, this should hold any paper model together pretty well, at least for a while ... :)

g.maclaren

08-05-2008, 09:46 PM

Hold the luan plywood panels together with tape,
clamps, rubber bands, etc.
Smear some Titebond along the seams.
Place "adding machine tape" along the seam,
pressing it into the glue. Smear more glue thinly
over the tape.
Let dry a few hours.
Remove the clamps, tape, etc. and glue/tape the other
side of the joint.
When glue is dry, give the seam a coat or two
of house paint.
Float you model boat.

g.maclaren

09-01-2008, 02:37 PM

All,

I've been away from this great forum for quite awhile.

Since July I have not done much "boating" but have been
thinking a lot about Twilight and still intend to build
something very close to meeting my original "problem
statement. (I've also been water skiing, working a bit
on my Four Winns 17' I/O -- and dreaming.)

I've placed an order for three sheets of 6 mm ply
(with a group of other builders) and purchased a set
of plans for an 18' "Piragua" by Jim Michalak -- mostly
because of that boat's displacement, not so much
that it meets my stated desires. (I met Jim earlier
this year at his "Messabout" at Rend Lake, IL, USA.)

Another thing I've done is purchased and read "Lapstrake
Canoes" by David L. Nichols. I've learned a lot from that
book and think almost anyone would. Nicely done!

We have one more serious day of water skiing planned and
I plan on getting my Four Winns stored in a friend's hangar
soon (as soon as I get the upholstery finished.)

I'l also be in Wisconsin enjoying some antique boating
with friends later this month.

For sure, I'm going to build a strongback and station molds
for Twilight -- so it's getting down to the wire on a
design -- a design that might change a bit as we go.

-=Grant=-

g.maclaren

01-22-2010, 10:15 PM

Hope my adding to this ancient (more than 509 days old, it says) thread doesn't screw things up too much. But I've been butchering some wood and cooking some epoxy. So it will soon be time to determine the beam of Twilight. (Rick, I'm back to original 2-piece hull with flat bottom.) I'm thinking between 26" and 30". Comments are invited and will be most welcome. Pls. see http://www.grantmaclaren.com/twilight
Thanks!

Guest625101138

01-22-2010, 11:11 PM

g.maclaren

01-22-2010, 11:27 PM

Hi Rick,
This weekend, I'm going to move some of the panels around on the strong back, and try to get a "feel" for what I see. Because I didn't have room to build it full length (and then cut it in two), I'm building one piece at a time. I might even slap it together and try floating "half" of it.
Thanks very much for your attention and input.
-=Grant=-

g.maclaren

01-26-2010, 09:50 PM

Grant
Hi again.

I have not done any calculations. My gut feel is that 30" will give you adequate stability. Anything smaller is going to be borderline.

Rick

Rick,
I've mocked it up with a 30" beam at "transoms" on "half" a hull length. It seemed too wide, so I made a 28" version to look at. (Is this seat-of-the-pants engineering . . . or what?)
I think my next step will be to put a bottom on it, wrap it in plastic sheet and see how it floats.
See pics at www.grantmaclaren.com/twilight/index4.html

Guest625101138

01-26-2010, 11:22 PM

Grant
There will not be much difference between 28" and 30" beam. I think it will be a bit tippy for boarding but a couple of decent batteries stowed on the bottom will improve that.

Will be interested in your progress.

Rick

g.maclaren

03-02-2010, 09:24 AM

Rick,

Here it is March, and I've not gotten very far.
Maybe Spring will speed me up a bit.
See small progress here on aft half of Twilight."
www.grantmaclaren.com/twilight/index5.html

-=Grant=-

Guest625101138

03-02-2010, 02:54 PM

Grant
Jeremy has made some recent posts on his little electric outboard here:
http://www.boatdesign.net/forums/boat-design/efficient-electric-boat-27996-19.html
You might find something interesting there.

Rick

Jeremy Harris

03-03-2010, 02:00 AM

Grant,

I've just spotted this thread. My aims are identical to yours, I want an easily driven river/inland waterways launch for two people to cruise in peace and quiet, with no fuel or pollution worries.

Rick's already pointed to the thread I started a fair time ago now. The hull I've chosen (because I didn't want to build one from scratch) is very similar to yours. It was designed as a pedal boat, but with enough stability to ensure that it feels comfortable for those who may have a slightly nervous disposition. To save you digging through the thread to find the pictures/link to the hull, here's a link to the pedal boat version: http://www.swallowboats.co.uk/content/view/94/30/

I look forward to seeing your project develop, good luck with it.

Jeremy