Friction in a bearing goes up significantly with diameter, requiring more sophisticated bearing such as ball bearing or pressure lubed, and also fine tolerances are more difficult with the larger diameters.. How exactly are you envisaging a kick up system if they go through the bottom of a hull. You either have to have sacrificial areas in the bottom of the hull, leading to difficulties in the structure, have blades that are designed to break off, or be prepared to lose the bottom of the boat
--- In harryproa@yahoogroups.com.au, Rob Denney <harryproa@...> wrote:
>
> Crud in the bearings, fouling, complexity, cost, damage potential, need for
> a flat bottom.
>
> On Mon, Jun 14, 2010 at 9:43 AM, Gardner <gardner@...> wrote:
>
> >
> >
> > Hi,
> >
> > I am curious about your objections to drum rudders. The seem to be a proven
> > technology, since they are in so many production boats (Hunter, Menges,
> > Gunboat, maybe?).
> >
> > I understand the point about collisions, and it also seems like there might
> > be an issue with getting enough chord on the rudder, but those are the only
> > drawbacks that come to mind. What am I overlooking?
> >
> > - Gardner
> >
> > Sent from my iPad
> >
> > On Jun 13, 2010, at 6:35 PM, Rob Denney <harryproa@...> wrote:
> >
> >
> >
> > G'day,
> >
> > I don't think much of in hull rudders, and even less of drum rudders, but
> > they are not too difficult to make from composites and acetal ball bearings
> > from McMaster Carr. You will need some turned alloy or steel (better) rings
> > to use as moulds. Let me know the width of the hull and I will do some
> > drawings.
> >
> > rob
> >
> > On Mon, Jun 14, 2010 at 5:17 AM, Gardner Pomper <gardner@...>wrote:
> >
> >>
> >>
> >> Ok, that is at least 10 times the price I am willing to pay. Anyone have
> >> any ideas on what it would take to make one (well, two, actually <grin>)? I
> >> would like to think that there would be an easy way to just build some extra
> >> rudders if you do hit something and pull out the old one (or push it down
> >> through) and replace it with a new one and (maybe) repair the old one at
> >> your leisure.
> >>
> >> Is this the system that Rapscallion was going to use? I remember his
> >> having in-hull retractable rudders, but I don't remember a mention of a
> >> drum, so it did not seem that they could steer while retracted, which turned
> >> me off.
> >>
> >> - Gardner
> >>
> >> 2010/6/13 Helmut Müller <hmueller@...>
> >>
> >>>
> >>>
> >>>
> >>>
> >>> Gardener,
> >>>
> >>> I got an answer in 2008 from Paul Amon for the inboard rudder:
> >>>
> >>>
> >>>
> >>> Each unit as installed on a Melges 32 would be around 6900usd with hard
> >>> anodized bearing, rudder, tiller, housing.
> >>>
> >>>
> >>>
> >>> Quite expensive, no solution for us.
> >>>
> >>>
> >>>
> >>> Cheerio
> >>>
> >>>
> >>>
> >>>
> >>
> >
> >
>