Friday, May 4, 2012

Re: [Electric Boats] Re: concept for an electric houseboat

 

Hi Eric, thanks much for the reply. The barge front end would definitely be an issue if the water entry of the hull wasn't so gentle. It is a very shallow angle though, so I don't anticipate a problem as long as the waves are 1.5' or less. Somewhere between 1' and 2' wave height I'll start knocking the "bow transom" into oncoming waves, greatly hampering forward progress. Large boat wakes aside, 2' waves on the rivers I'm talking about are not the norm. In the types of conditions I'm going to be operating in, < 1' waves are to be expected.

As far as the boat settling fore and aft, we should discuss that because it's been a theme of the feedback so far this morning since posting the pics. By my calculations, at 12k displacement and perfect COG, if I (a touch more than 200 lbs) were to move from the center of the boat and go stand on the rear transom, the stern would settle < 1/3". I'm quite willing to accept that. Stepping out onto the bow would cause the front to settle a little more because the COG is about 2.5' aft of the center of the boat, but it wouldn't be much more. Less than 1/2", I believe (though I didn't run the numbers on that yet, so it could be a bit more... but *definitely* less than 1").

All that being said, it's difficult to know how wave action will set the boat to pitching, or how quickly she'll settle down once started. That's definitely a bit of a gamble on my part, but so far I haven't heard anything that makes me want to avoid that gamble enough to redesign the boat. :)

Side winds are indeed a real possible issue. I do have some experience piloting larger houseboats, and side winds really, er, "blow". ;) The height of this one is a compromise, higher than I'd like for exactly the side wind reason, but lower than I'd like for living concerns. Note that one will be forced to duck no matter how they enter this boat. In this particular case I'll probably just have to pick my weather window and go out when the wind is fairly calm. Fortunately it's not overly windy here, and for me just being on the boat is a lot of fun, even if I'm not moving it around on the river.

I'm still interested in hearing someone's thoughts about the ideal power, prop size, prop rpm, and prop pitch for this boat. 27' waterline. 12k lbs. Fairly easily driven in calm conditions, but heavy.

Still hoping for a 48v system, too.

Thanks,
-keith

--- On Fri, 5/4/12, Eric <ewdysar@yahoo.com> wrote:

> From: Eric <ewdysar@yahoo.com>
> Subject: [Electric Boats] Re: concept for an electric houseboat
> To: electricboats@yahoogroups.com
> Date: Friday, May 4, 2012, 11:35 AM
> Hi Keith,
>
> There might be reasons that you've never seen a boat design
> quite like what you've come up with.
>
> With a barge front end, no bow taper, I doubt that a 10kW
> outboard could push the boat to hull speed (6.5kts) even at
> full power.  The full rocker will mean that the boat
> will settle fore or aft when you walk from one end to the
> other, maybe entertaining at first, but I wouldn't want to
> live like that.  You need more set bouyancy at the ends
> to create a stable platform.
>
> Personally, I wouldn't be worried about driving into a
> headwind, I think that your design lasks the power to deal
> with almost any sort of cross wind.  Your boat has a
> huge side profile.  Think about it with a regular ICE
> outboard.  I wouldn't think that a 20hp motor would
> provide safe navigation in anything but very calm
> conditions.
>
> But you did say that this is a liveaboard, and as a floating
> home, it's seaworthyness is not really an issue.  Most
> of the liveaboard houseboats in my area can barely move
> under their own power and rarely move at all.  So if
> you boat has just enough power to move slowly from one place
> to another, picking only the most benign conditions, then
> you should be fine.  If that is all that you want to
> do, then your design should be adequate.
>
> Fair winds,
> Eric
> Marina del Rey, CA
>
> "It's easy to make something that looks like an airplane,
> it's much harder to make one that can fly."
>

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[Electric Boats] Re: concept for an electric houseboat

 

Hi Keith,

There might be reasons that you've never seen a boat design quite like what you've come up with.

With a barge front end, no bow taper, I doubt that a 10kW outboard could push the boat to hull speed (6.5kts) even at full power. The full rocker will mean that the boat will settle fore or aft when you walk from one end to the other, maybe entertaining at first, but I wouldn't want to live like that. You need more set bouyancy at the ends to create a stable platform.

Personally, I wouldn't be worried about driving into a headwind, I think that your design lasks the power to deal with almost any sort of cross wind. Your boat has a huge side profile. Think about it with a regular ICE outboard. I wouldn't think that a 20hp motor would provide safe navigation in anything but very calm conditions.

But you did say that this is a liveaboard, and as a floating home, it's seaworthyness is not really an issue. Most of the liveaboard houseboats in my area can barely move under their own power and rarely move at all. So if you boat has just enough power to move slowly from one place to another, picking only the most benign conditions, then you should be fine. If that is all that you want to do, then your design should be adequate.

Fair winds,
Eric
Marina del Rey, CA

"It's easy to make something that looks like an airplane, it's much harder to make one that can fly."

--- In electricboats@yahoogroups.com, Keith Jacko <nrixez@...> wrote:
>
> I agree with you about the power. A 4 mph current is not the norm of the upper Mississippi... it's fairly rare. I'd personally feel more comfortable with a lot more hp, but larger format electric outboards are just not available. The biggest I've heard of is an Aquawatt at 20kw (BIG GREEN THRUSTER 80 V 20KW). Still not a huge motor really, unless you're considering the price tag, and then it's ginormous. :)
>
> Incidentally, I'd like to stick with a 48v system if possible. It might not be, but it's a nice-to-have in my mind.
>
> Thanks for the feedback about the hull form. I know having the rocker like that isn't the norm, but it's not nearly as severe as Bolger's designs. (I was using Bolger and Thiel as inspirations for this design; I've heard their boats are very easily driven.) I absolutely agree that one tradeoff with the full rocker is less pitch stability. I think I'm willing to sacrifice that though because I won't be using this on big water. Do you think the rocker as pictured is so severe that it'll actually cause issues?
>
> Cheers,
> -keith
>
>
> --- On Fri, 5/4/12, danbollinger <no_reply@yahoogroups.com> wrote:
>
> > If this was on a lake and you only
> > had to deal with the occasional headwind I'd say that 10Kw
> > (13HP) was enough, but not in a 4 mph river current. I use
> > my Torqeedo on a 12' john boat on the Wabash and its typical
> > 2-3 mph current is formidable.
> >
> > Concerning the hull form, I'd take out the severe rocker.
> > Putting in a flat bottom admidships will give you greater
> > pitch stability, reduce draft and power requirements, too.
> >
>

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[Electric Boats] Size of Trolling Motor needed

 

Apologies for hitting again what is well travelled road on this forum, but advice is needed and this looks like the best source there is....

I'm in the process of building a small mini-cruiser; it's less than 4 metres long (12' actually), but quite beamy and heavy. It is intended to have water ballast, but I am substituting lead-acid batteries (a couple of 12V 100 Amp-hr)to bring the sailing weight in at about 300Kg (650 lb). You can get an idea what it is like here, if it helps: http://www.youtube.com/watch?v=wRZNWAkdkXM

As much as any, the reason for the change of ballast is to be able to use an electric outboard as auxiliary power to get me off the dock/beach, back home when in a hurry and so on (nearly exclusively sea use, rather than fresh-water).

If they were still available, I would have used a Torqeedo 801, but of course they are not and the replacements, the 503 or 1003 cannot be used with external batteries (I discount using an inverter to produce AC to trickle-charge the built-in lithium-ion cells on grounds of safety and wastefulness of power)and they are pretty expensive for what they are.

Looking around at alternatives, the only real option looks like a Minn-Kota Riptide (at least in terms of UK availability). They produce 55lb, 80 and 101lb thrust versions. My question is therefore whether any of these will do what I want, as I have heard that trolling motors are pretty inefficient and poorly propped for the sort of application that I have in mind (although of course displacement hull speed will be a limiting factor of around 4-4.5 kts); can anyone who has experience of these motors please advise?

I suspect that I am going to have to butcher which ever one that I use because of the shaft length (I don't think I 'll be doing any fishing...) and cut the shaft down to a more appropriate size.

Looking on the Torqeedo web-site ( http://www.torqeedo.com/images/kataloge/TQ_Katalog_2012_EN.pdf), they suggest (footnote at the bottom of the page)and working through the implications, that the static thrust quoted for 80lb thrust from a trolling motor broadly equates to the equivalent of abouta 2HP ic engine, is that about right and therefore the size that I need? Or have I got that wrong? Can I get away with the smaller (cheaper!) size? One difference is that the smaller one is 12V, whereas the larger is 24V, which I guess will have lower losses (everything else being equal); as I have two batteries, the different voltages can easily be accommodated.

Would a change of prop help my application? For example, http://kipawapropellers.com/index.html.

If I could get a suitable outrunner motor, gearbox and controller, I would'nt mind building my own using a Torqeedo prop, but that doesn't necessarily look very straightforward, if there is a suitable alternative.

As I said above, my apologies for covering old ground, but I haven't managed to find much here in the UK (most of the Electric Boat Association craft are somewhat different)

Thanks,

Nigel

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[Electric Boats] Re: concept for an electric houseboat

 

Many of Bolger's river cruisers are flat-bottomed sharpies with just a little rocker.

Beside using a flat bottom to control pitch, which makes sense in a river, you can also deal with the fore and aft profile. Use the full rocker bottom as you have shown, but as you near the stem and stern, let the form go tangent to your rocker curve. This adds bouyancy that can control pitch. For instance, see Bolger's AS39. Here's something similar, note the tangent (straighten form) fore and aft.

http://www.ace.net.au/schooner/TRAWICsm.jpg

--- In electricboats@yahoogroups.com, Keith Jacko <nrixez@...> wrote:
>
> I agree with you about the power. A 4 mph current is not the norm of the upper Mississippi... it's fairly rare. I'd personally feel more comfortable with a lot more hp, but larger format electric outboards are just not available. The biggest I've heard of is an Aquawatt at 20kw (BIG GREEN THRUSTER 80 V 20KW). Still not a huge motor really, unless you're considering the price tag, and then it's ginormous. :)
>
> Incidentally, I'd like to stick with a 48v system if possible. It might not be, but it's a nice-to-have in my mind.
>
> Thanks for the feedback about the hull form. I know having the rocker like that isn't the norm, but it's not nearly as severe as Bolger's designs. (I was using Bolger and Thiel as inspirations for this design; I've heard their boats are very easily driven.) I absolutely agree that one tradeoff with the full rocker is less pitch stability. I think I'm willing to sacrifice that though because I won't be using this on big water. Do you think the rocker as pictured is so severe that it'll actually cause issues?
>
> Cheers,
> -keith
>
>
> --- On Fri, 5/4/12, danbollinger <no_reply@yahoogroups.com> wrote:
>
> > If this was on a lake and you only
> > had to deal with the occasional headwind I'd say that 10Kw
> > (13HP) was enough, but not in a 4 mph river current. I use
> > my Torqeedo on a 12' john boat on the Wabash and its typical
> > 2-3 mph current is formidable.
> >
> > Concerning the hull form, I'd take out the severe rocker.
> > Putting in a flat bottom admidships will give you greater
> > pitch stability, reduce draft and power requirements, too.
> >
>

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Re: [Electric Boats] Re: concept for an electric houseboat

 

I'm not any kind of expert but I'd agree about the deepish rocker, and I think 6 tons comes up being kinda awful heavy. a pontoon configuration was mentioned but I'd think for that kind of length its doubling the waterline drag and making turbulent drag between em, so no advantage, then theres the structual "fun" of something catamaran (no thanks!).
I like the looks of something like a Mundoo, might be large enough and would likely get around better on lower power. very similar to the Mundoo's is http://www.duckworksbbs.com/plans/storer/tc35/index.htm
Displacement - approx 1800kg (1.8 tons) (includes crew and tankage half full)
sure.. its giving up a bit of square footage going that route, but oughtta travel better.
 
other stuff.. I'd recently installed the "low power A-C unit" into my little electric runabout toy, it's essentially a 1gpm 0.3A 12v pump, through a 6x8x2 automotive heater core, with 2 45 cfm 12v computer case fans. idea being if water is 65-70f, it oughtta blow 80-90 cfm of air maybe 5-10 degree warmer, oughtta be nice when HOT out. it draws a total of 0.8A
its enough to change out the air of a 6x6x6 (216 cu ft) 22-25x an hour too. 
currently plumbing and wiring the same little pump for my fishin boat's livewell, should be enough to change the water 8-10 times per hour is plenty, and only 0.3A to do it.

--- On Fri, 5/4/12, danbollinger <no_reply@yahoogroups.com> wrote:

From: danbollinger <no_reply@yahoogroups.com>
Subject: [Electric Boats] Re: concept for an electric houseboat
To: electricboats@yahoogroups.com
Date: Friday, May 4, 2012, 8:06 AM

 
If this was on a lake and you only had to deal with the occasional headwind I'd say that 10Kw (13HP) was enough, but not in a 4 mph river current. I use my Torqeedo on a 12' john boat on the Wabash and its typical 2-3 mph current is formidable.

Concerning the hull form, I'd take out the severe rocker. Putting in a flat bottom admidships will give you greater pitch stability, reduce draft and power requirements, too.

--- In electricboats@yahoogroups.com, Keith Jacko <nrixez@...> wrote:
>
> I'm interested in building an electric house boat. The basic concept is an easily driven houseboat, strictly displacement speeds (6 - 7 mph), powered by an electric outboard. I'm thinking about a 10kw outboard. The boat as sketched would displace just a little under 6 tons to sit on her lines. Here are a few pictures of the boat sketch (and a .skp file if anyone wants to play around):
>
> http://www.dwdogs.com/Fusion/
>
> I'd love to go with a ~40 kwh LFP pack, but reality probably has me sticking to around 20 kwh. There is enough space on the roof of the boat to fit 2 kw of solar panels. More if I really stretch it, but I'm thinking 2 kw should be enough.
>
> Basic boat dimensions: 32' x 8' with a 16" draft. At 12,000 lbs with the proper center of gravity, the bottom of the transom would just be touching the surface of the water.
>
> I live in Minneapolis, and this boat would be for cruising on the upper Mississippi and St. Croix rivers. Fairly sheltered, and no currents greater than 4 mph (hopefully less most of the time).
>
> The boat will be built with plywood covered in glass / epoxy. I do plan on having fairly thick cabin walls for a boat... 2x4 construction, with closed cell foam insulation / floatation in the walls, hull, and cabin roof.
>
> Any feedback about the sketches or general idea? I'm designing this as a liveaboard, and I plan on living on the hook as much as possible.
>
> About the outboard, I'm not really sure how to figure the proper prop size, pitch, and rpm to shoot for. I understand the general rule of thumb "bigger prop, slower rpm, better"... but I don't know much past that. Could an electric outboard like say the up and coming Parsun 10 kw efficiently drive a heavy displacement boat like this? Or would it be better to think about using an inboard instead, so I would have the flexibility to tailor the rpm to my liking? I really do like the overall project simplicity of an outboard, but if it's really less than ideal I could consider alternatives.
>
> Thanks for your thoughts and feedback. Cheers!
> -keith
>

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Re: [Electric Boats] concept for an electric houseboat

 

It wasn't my intention to start a discussion about the boat building aspect of the project; I'm pretty comfortable with my chosen materials and building technique.  I'm more interested in figuring out how to electrically drive this thing well and with the most efficiency possible.  Honestly, she shouldn't displace the full 6 ton even with all my stuff on board... but if she floats an inch or two high that shouldn't be a problem.

-keith


--- On Fri, 5/4/12, John Robert <johnrbrt@gmail.com> wrote:
Keith, and all,
What would be the advantage/disadvantage of metal framing for those interior walls?
Seems like there would be less weight, also resistance to moisture and associated problems,
assuming one properly coats/treats the metal frames prior to installation.
"JR"

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Re: [Electric Boats] Re: concept for an electric houseboat

 

I agree with you about the power. A 4 mph current is not the norm of the upper Mississippi... it's fairly rare. I'd personally feel more comfortable with a lot more hp, but larger format electric outboards are just not available. The biggest I've heard of is an Aquawatt at 20kw (BIG GREEN THRUSTER 80 V 20KW). Still not a huge motor really, unless you're considering the price tag, and then it's ginormous. :)

Incidentally, I'd like to stick with a 48v system if possible. It might not be, but it's a nice-to-have in my mind.

Thanks for the feedback about the hull form. I know having the rocker like that isn't the norm, but it's not nearly as severe as Bolger's designs. (I was using Bolger and Thiel as inspirations for this design; I've heard their boats are very easily driven.) I absolutely agree that one tradeoff with the full rocker is less pitch stability. I think I'm willing to sacrifice that though because I won't be using this on big water. Do you think the rocker as pictured is so severe that it'll actually cause issues?

Cheers,
-keith

--- On Fri, 5/4/12, danbollinger <no_reply@yahoogroups.com> wrote:

> If this was on a lake and you only
> had to deal with the occasional headwind I'd say that 10Kw
> (13HP) was enough, but not in a 4 mph river current. I use
> my Torqeedo on a 12' john boat on the Wabash and its typical
> 2-3 mph current is formidable.
>
> Concerning the hull form, I'd take out the severe rocker.
> Putting in a flat bottom admidships will give you greater
> pitch stability, reduce draft and power requirements, too.
>

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