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.
> >
>
No comments:
Post a Comment