Transom Raked Forward

[maa. melee]

I was thinking about this today and wanted closure on the topic. If a transom is raked forward (like alot of modern plastic boats), as opposed to tradional aft raked transoms, is it possible to mount a kick up rudder? If not are there rudders that can be kicked up or disconnected from under the boat for beaching?

Is this a crazy idea or can it be done?

http://img.photobucket.com/albums/v197/maa_melee/rudder.jpg

[ 03-09-2005, 11:58 PM: Message edited by: maa. melee ]

[Ian McColgin]

Too much top-foreward rake to the rudder increases cavitation and weatherhelm as the boat heels. The rudder outboard the reverse transom drawn appears too sloped.

The reverse transom's real purpose, besides a fashion statement, is to have the desired waterline length but with a lighter hull. The lightness comes in as you have less hull and deck structure back there. This assumes you don't need the bouyancy back there.

Some boats have the profile appearance of a reverse transom but the aft end of the cockpit actually has a verticle bulkhead at the aft end of the deck shereline and the hull is open behind that. In such a hull, some have knocked out a wedge to allow the rudder to be raised and still allow a bit of turning. Seems to me this defeats the idea of drawing out the hull lines.

You could have a small trunk to raise it up in but that also induces unneeded turbulence.

I'd be inclined to look closely at the reason one must have a reverse transom and a lifting rudder.

[JimConlin]

Some trimarans have a 'trunk' cut into their stern, The forward side is vertical and within it is a pivoting carrier which includes the rudderpost tube. The whole carrier pivots up to raise the rudder.

[Tom Lathrop]

On small boats, I think the reverse transom is mainly a styling thing. A bit lighter, but you loose valuable cockpit space which means the boat is actually smaller than it seems.

On larger boats, the reverse transom makes for nice boarding steps, swim platforms or even dinghy storage. Unless it serves one or more of these purposes, I'd rather have the extra room.

Your first rudder will give gobs of weather helm with the center of effort so far behind the pivot point. Some boats have structure added to support a vertical outboard rudder on a reverse transom.

I also think the traditional stern counter transom is prettier but if the rest of the boat looks like a Nike running shoe, the revese transom is not too noticeable.

[ 03-10-2005, 02:51 PM: Message edited by: Tom Lathrop ]

[maa. melee]

I know the weather helm would leave much to be desired. I guess a kickup rudder here isn't very practical. I was thinking about this just to see if there was a solution. Thanks for the help.

[Stiletto]

A friend had a 9.3metre performance keeler that had only a slight forward rake to the transom. By experimenting he found that shimming the top pintle out about 40mm to make the rudder vertical made quite an improvement.