Weight distribution for an electric launch

[Sander Rave]

Hi all,

Can anyone give me some wise advise?
I have these two main thoughts, and need someone to tell me if I'm correct on the following:

When I put a bunch of batteries in a boat for propulsion, and I like to go for some hours, I need a substantial quantity of batteries. to keep the amount of copper low, you want to keep them close together.
If you do so, and put them in the center of the boat, I guess it will roll on every wave along the way and people won't experience a pleasant ride.

I guess to give it a confortable ride, you need to distribute the batteries afront and aft, by the rule that the mass slowness of the batteries will make the boat unwieldiness?

Is there someone outhere who can give me an experienced advise?
Regards,

Sander

[cyclops]

Remember. In a storm everyone is huddled in the center of the boat. That is where your batteries want to be.

[gonzo]

The moment of inertia increases if you distribute the weigh around. It will make the ride more comfortable and may be safer too. Boats that roll or pitch too much can get out of control.

[cyclops]

Keep them LOW. Build in a exhaust pipe from the top of the battery room to some point above people standing on deck with lit cigars, etc. The hydrogen gas has to rise to leave the boat. Otherwise--KABOOM.

[Sander Rave]

merci!

[gonzo]

The question of battery exhaust gases is rarely addressed. It is a safety issue. The stability of the boat and the weight distribution are related to hull form. There are no generic answers. If you have so many doubts, you should consider consulting a designer or use an existing known good design.

[Sander Rave]

Hi Gonzo,

Every new design has its unknow factors. They can be indexed if you know what you're doing. With alternatives as backup, this shouldn't be a problem, that's the fun of designing.

In this case i can go for trail and error, but this is pretty time consuming and stupid if there is an experienced soul around. With hands-on information around it's useless to reinvent the weel.

a lot of answers are pretty generic, because they are dictated by the laws of nature, but one can easily get distracted bij theory ;-)
Regards,

Sander

[gonzo]

I think that you need to narrow the question some more. For example, post a preliminary drawing of your boat. This would give some context to the answers.

[Sander Rave]

Thanks for your suggestion.

This I will do, as wel as this feed back already triggered my gey cells. With the present feedback I'm a step further. This little launch is just a leasure craft, not a passage maker. Comfort is bliss. Storm on open waters won't be an option.

In this case I'd say as we say in Holland: Who was first: the chicken or the egg? Preliminary will be very preliminary when I don't know what to fit in where. The hull has to contain propulsion, secundary systems and passengers, and I'd like it as compact as possible.

I'll stick with your first reply. Thanks guys!

[mattotoole]

Have a look at a Duffy, and see how they do it. (http://www.duffyboats.com)

[sal's Dad]

Phil Bolger has written extensively about his personal electric launch "Lily". As I recall, he has a mechanism for sliding part of the battery bank forward and aft, to optimize trim.

The write-ups I saw were in Messing About in Boats a few years ago, I believe he also has a video of the boat available. Googling -Bolger Lily electric- turns up plenty of references.

[Raggi_Thor]

Normally you will put the weight in the bilge, on each side, you want to minimize longitudinal moments and maximize transverse moments, you want the bow to lift over waves and you want a slow roll.

[Sander Rave]

Thanks guys!