rudder mountings

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nick.beeton
Re: rudder mountings

In the past I have had excellent service from CCS Fasteners of West Lothian Tel: 01506 834344, email: enquiries@ccsfasteners.co.uk.
They have supplied marine grade s/s UNF nuts, bolts, washers and spring washers to the specific sizes and lengths I required. I prefer UNF as opposed to the original UNC because the TPI is inherently stronger and more secure.

Navigation is a series of plots. In fog the plot thickens...

rick.jones
rick.jones's picture
Re: rudder mountings

Hi Nick

I take your point on UNF, but in contrast I believe that the coarser threads of UNC are less prone to damage, less likely to seize, and of course quicker to assemble and disassemble as fewer turns are required!

Nexus 4, Lollipop 5.0

Rick Jones (Treasurer) 1994 Mac 19 "White Lightning", Isle of Wight

martin.baker
Re: rudder mountings

Hi Nick,
I had a similar kind of problem on my 26D although it has only one rudder and an exterior rudder stock. There was enormous pressure on the rudder and stock when sailing close hauled or in a following sea and this caused the damage. I solved the problem by reinforcing the stock, making a new longer rudder slightly angled forwards under the transom and creating a new rudder downhaul system to make sure the rudder went down well and stayed down as there is more pressure on the rudder if it is angled back away from your transom. I can now heel in a good wind close hauled and steer with a little finger, the rudder is balanced with the axis in the middle instead of forward.
Happy sailing,
Martin

rick.jones
rick.jones's picture
Re: rudder mountings

Good point Martin. I concur that it's very important to ensure the rudders are fully locked down. Even the slightest amount of aftwards "trail" massively increases the load on the brackets.

Nexus 4, Lollipop 5.0

Rick Jones (Treasurer) 1994 Mac 19 "White Lightning", Isle of Wight

mike.floutier
mike.floutier's picture
As I'm just getting into

As I'm just getting into close quarters manouveuring :) I've had a close look at my rudder & o/b alignment.

The upshot is that my starboard rudder is aligned with the o/b BUT, in this position, my port rudder is well out of alignment.

Problem is that I can't see how to adjust the rudders.

Any ideas?

MacGregor 26M 2009 - Sky's the Limit -  Suzuki DF50

mike.floutier
mike.floutier's picture
Ok, well, apparently, there

Ok, well, apparently, there is some form of adjustment on the X, but not on the M.

In theory no adjustment is needed because the correct geometry is built in at manufacture.

However you could say the same about car steering and suspension geometry BUT, as we all know, there is plenty of adjustment built into them.

I have come across a few suggestions for adjustment Mods but they seemed to involve such things as welding and hydraulic steering which I found a little off-putting.

My conclusion is that the easiest approach will be to add some extra holes at the ends of the long link rod that connects the extreme forward ends of the rudder actuator bars.

Looking at the geometry I'm estimating that I'll need to reduce the link rod length by at least an inch to get my rudders in sync. I'll have to re-assess things and possibly add more holes; not to mention possibly needing to adjust the o/b BUT the result should hopefully be the Mac equivalent of F1 DRS flap activation; so look out astern!

MacGregor 26M 2009 - Sky's the Limit -  Suzuki DF50

dave.newton
 

The rudders on high performance yachts are not absolutely parallel. The hydrodynamic flow near the transom is inward and upward (to fill in the hole left in the water behind the boat). The rudders are aligned with the neutral water flow so have a small amount of 'toe out'.

But at the speeds of a Mac this would be miniscule and anyway would be symmetrical. If yours aren't parallel I can only assume something is bent or has been modified.

Dave Newton Sailbadthesinner

mike.floutier
mike.floutier's picture
Thanks Dave, that's

Thanks Dave, that's interesting.

Mine actually has toe-in anyway.

Will let you know how my simple adjustable track rod mod goes.

MacGregor 26M 2009 - Sky's the Limit -  Suzuki DF50

mike.floutier
mike.floutier's picture
Haha, two things, Dave when

Haha, two things, Dave when you said toe-out I just twigged that, of course, the "toe" of the rudder is the leading edge. Doh, picture me looking over the transom thinking that the trailing edge is the toe.

So my rudders are set up with toe-out.

However, as you say, this toe-out effect shouldn't really apply to our typical speeds, eg 5 knots.

Also, the area I've been struggling with is slow speed manouvuering, eg docking against wind and tide, so hopefully it will help to have the rudders lined up.

MacGregor 26M 2009 - Sky's the Limit -  Suzuki DF50

dave.newton
 

Mike,

Part lifting the centre board does help maneuvering. The rudders turn the boat about a centre of rotation that is somewhere in the keel area. Moving that area aft and up has two effects. The centre of rotation moves aft giving a tighter turning circle and even though the keel area doesn't reduce much it moves up and so has less resistance to water passing around it. This gives less resistance to the boat yawing so the it turns with less effort. But if you go too far the keel loses it's effect as a pivot and the boat tends to simply crab sideways and not rotate as much.

I've found about half centre board seems to work nicely and has the added advantage that if I did ground it, it is more likely to lift and avoid damage.

Aggh! the above applies to an X not an M, please disregard!

Dave.

Dave Newton Sailbadthesinner

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