Rudder Attachment to 26M Hull

[Highlander]

Good one Boat! Unfortunately I can't get your video to play - still trying. (How long did you hold your breath...)
That's why HUNTER angles the rudders on their boats that have dual rudders.
Do you mean outward? Mastreb talked about wanting to do that once. Too much re-engineering was involved to alter the stock configuration.
R.

Ross I have a pic in one of my old laptops somewhere Of a converted rudders to raise vertically instead of horizontally meaning they could be still used in shallow water , he must have used other rudders as the rudders r about 26-28" long X 18" wide & they stay pinned down while sailing or under power WOT but they r about 2" thick very strong & heavy , I'll see if i can find that pic & post it tonight

J

[BOAT]

Good one Boat! Unfortunately I can't get your video to play - still trying. (How long did you hold your breath...)
That's why HUNTER angles the rudders on their boats that have dual rudders.
Do you mean outward? Mastreb talked about wanting to do that once. Too much re-engineering was involved to alter the stock configuration.
R.

Ross I have a pic in one of my old laptops somewhere Of a converted rudders to raise vertically instead of horizontally meaning they could be still used in shallow water , he must have used other rudders as the rudders r about 26-28" long X 18" wide & they stay pinned down while sailing or under power WOT but they r about 2" thick very strong & heavy , I'll see if i can find that pic & post it tonight

J

Click on the link below the picture, not on the picture - and it should take you to a video on the photobucket web site. It the same photobucket website that Highlander uses.

I was under the impression that Highlander and beene were already using raked rudders with the flat tips - did I not see a post where the rudders on their boats were not stock? I think their boats already have modified rudder attack.

[seahouse]

Ah ha! On several points things are clearer... and now I see- previously in my mind I had the brackets spreading facing rearward, instead of downward.

I couldn't launch today, so between passing storms and downpours I bodged the following patterns...

There's not a lot of room to put much reinforcement there, and still allow full range of movement (both steering, and deploy/retracting), but the patterns here are out to the max size allowed, so real-world parts will have to be no larger. Off the top of my head I'm picturing 1/4” thick stainless (say, 304L for weldability) here, but 3/16” might suffice.




The very simplest, but least rigid, is a single piece that would just be welded on the outside of the present factory bracket to help reduce the spreading lower down. The width (less than 3/4” ) can be maximized if they are placed so they are level with the space between the 4 mounting bolts at the transom. For more strength you could also use two, one above the other. Welding a thicker piece of metal onto a thinner (factory bracket) piece is less than ideal, but workable, and placing the weld on the bottom allows a possibly unsightly weld to be invisible. Placing the piece just back from the edge by a 1/2” or so, and not right at the edge, will make a better weld too.





In another scenario the larger piece shown would mount below the existing bracket with a reinforcing piece, similar to the one above, welded on the outside. There's room there, and your wings would attach adjustably to these, Crikey. The pivot bolt would need to be replaced with a longer one (maybe bigger too, you could drill out the rudder for 7/16” or 1/2” bolts). I didn't deal with the stop tab, it could be removed and replaced, or a relief could be cut out for it. This makes use of the factory bracket too.

These are geared toward holding the factory tabs in, they don't provide any direct support by bearing against the rudder itself. But placing poly or similar pads of the right thickness inside them would help support the rudders directly.

I'm not really set up to efficiently undertake a project like this, but these are my thoughts, probably similar to what others had, but feel free to use whatever you can from it, if anything.

Has anyone looked to see if Tattoo made any changes in this area?

- B.

[seahouse]

Here are the planforms.



- B.

[Crikey]

Here's the IDA...

Here's stock...

Definitely beefier and seem to be more aft of the pivot point.

Coming back to Wanderers initial point; I think the overall hardware has enough structural strength to easily resist catastrophic failure in any area. It may bend or flex in its weakest areas but I've not seen anyone commenting on welds cracking or surfaces fracturing. The problem seemed to solely come down to corrosion and looseness, and the friction wear resulting from that. Seahouse comes up with an approximate total of 10,200lbs for the sum strength of the four stainless bracket bolts which is going to be way above any sailing loads that would probably break a rudder quickly. Bending of the tangs through over-stressing remains the problem and any lateral flexing is sure to translate into some steering play.
I wonder if anyone has ever noticed bending in the gudgeon (?) bracket at the bottom of the M's setup?

I'll raise my brace fix idea one last time before my hijack contribution ends and I get to work preparing a mod (assume for now I'm not futzing with the rudder skegs thingee) for a separate post later on.
What would be difficult in bending up a simple U shaped SS sleeve that would be slipped over the existing piping and tangs, with exactly matching rudder pivot holes. Rigid as all heck! Easy Peasy....
Correction:
Bri you beat me to the punch in mid edit!
Your idea is elegant, particularly the lower extension for holding more of the rudder top. Unfortunately due to my lowering that's not going to work for me too well. Wouldn't just a non welded sleeve on the upper section only, be sufficient for a large increase in strength if it was snugly fit? The reduction in turning radius would then be very minimal even with thick plate.
Nice work BTW.

R.

[seahouse]

Reminds me - I still have a couple of sets of the rudder spacers on hand if anyone else wants a set (of 4). They are US $50 including shipping, as discussed in this thread...

http://www.macgregorsailors.com/forum/v ... it=customs

-B.

[seahouse]

Wouldn't just a non welded sleeve on the upper section only, be sufficient for a large increase in strength if it was snugly fit? The reduction in turning radius would then be very minimal even with thick plate.

Yes it would. And by my observation it would result in no reduction of the rudder swing range, there is lots of room for it, and the pivot bolt ends (head, nut) come nowhere near the transom.

Even simpler, a large plate on each side (doesn't need to wrap around the back) like a giant square washer having the profile of the bracket petal (and almost identical to my plastic spacers) should be sufficient too. I have mentioned a large, thick washer previously, but before I was aware of the spreading at the lower part of the petals (a good word for them you used, BTW), so for full support to the edges a full form-fitting backing plate is needed. The pivot bolt (go longer and larger at the same time) would have to be snug and hold the whole thing together, so the plastic spacer would be essential for this. A small tab over the edge would stop it from rotating, and there would have to be some accommodation for the stop tabs.

A small compromise with this is the loss of full steering range when the trailering lock-up bolts are in place. The heads on mine already contact the transom when full over.

The pressure calculation was Matt's, I think.

- B.

[kurz]

If you strengten it, will it solve a problem or povocate a next one?

I mean, if there will be much load on the rudder in original setting the bendings takes much of the shok load.

If it cannot bend anyore all the forces are loocking for the next week point. Where will it be???

[Crikey]

It must be either the bottom hinge bracket or the rudder itself.

But given the bolt strength I think the amount would be very small laterally. Downward would be more likely under some weird condition, which would result in the rudder dropping free and damaging the upper fibreglass - though that seems pretty strong too.
My particular mod was also done with an inverted upper bracket in mind that could carry a SS bearing as well provide a better limiter to any upward movement, and carry the higher loading if I dragged a foil under power. It's all very experimental at this point.

Seahouse - wouldn't side plates joined by a wrap around section - sorta like a big money clip - be much more rigid than two separate pieces? Just one side would need a small channel cut to fit over the position tang. Just bend it over a mandrel, fit it and then mark the bolt holes. I never use the locking bolts anymore because I'm afraid of pothole loading while in transit. Bungees do the job fine for me.

R.

[seahouse]

Yeah, the next weakest point could even be inside the hull at the steering mechanism there. I think that was Ixneigh's point too, but this one's the weak link that we know of at his point in time. Fix the next weakest one when it rears its ugly head and you find out where it is .

Interesting how the position on the hull of the white/blue stripes changed from the '10 model to the '11 model; your pic vs my pic above.

Sure, the wrap would be more rigid than 2 plates, Crikey, I like that idea. My thoughts were towards the level of difficulty it will be to make that part to the tolerance you need; comparatively, two plates are dead simple.

If you know a fabricator that can handle that, such as a CNC fabricator, they could probably do it easily. Otherwise it would be tough to bend it around and end up with the two faces dead parallel to each other, and at precisely the dimension you need for it, if you were thinking of trying it yourself. It would be more doable if it were heated first and formed around an adjustable mandrel, (as you suggest) so you could do several trials allowing for whatever overbend and springback you get, and end up parallel at the dimension you want.

The wrap-around would be a nice easy retro-fit installation, too, but you would have to remove the 4 screws from the lower support bracket, of course. (All of which you likely already knew).

-B.

[Wandering]

I have certainly learnt a lot on reading the comments. I have the flaring referred to earlier. So I will have to consider replacing this or strengthening it.

But Seahouse if there are no other takers, I can email you my postbox details to acquire the spacers as a starter.

I believe the cause were the two long and windy crossings I referred to, that kept me at the helm for four hours to prevent broaching and take pressure of the wheel, it was not a day for someone new to the boat to relieve me!

But I am disappointed that I will not have full confidence in sailing her with rudders that are not handling the pressure....more beer needed at the end of my next Georgia Strait crossing....lucky I am an Aussie...

[Crikey]

That explains it! Your rudders are installed upside down....

[Crikey]

Maybe we could eliminate our rudders entirely and put one of these bad boys on instead....

[BOAT]

There is on critical point that's not pointed out here - THE ROPE. The rope is the third leg of this whole thing. I don't think the bracket parts bolted to the boat will fails as long as that rope is tight.

The rope must hold the rudder snug against the plate and rudder stop - the ROPE is actually pulling the rudder through the water, not the bolt or the bracket.

The whole concept of the MacGregor factory setup was that the bracket would "PINCH TIGHTLY" on the top of the rudder to secure the "pendulum effect forces" on the rudder but it's always been the ROPE that holds the rudder in it's vertical position and pulls it through the water.

If that "PINCHING" does not occur because the bracket has bent apart, (be it at the top OR the bottom), the whole system falls apart - and alas the weakness in the design.

The key is to get that "PINCHING" effect and KEEP IT SNUG.
Problem: The rudder might be too long to be supported by such a short bracket - so I suspect the seahouse 'long bracket' design might be the only fix that will not bend a bracket and not break a rudder.

[mastreb]

Winds were too high to hoist the sail on my new rig to finish the boom installation, so I took the opportunity of being disappointed at my boat to install Brian's LDPE rudder spacers and inspect my brackets. My boat is a 2011 so just over three years old.

While i noted a reasonable amount of surface rust on the bolts, my brackets exhibit no splay at all (in fact they were still so tight that installing the shims was difficult) and I saw no evidence of any problematic corrosion. My boat has always been very dry with no leaks whatsoever thus far (knock on FRP).

I believe BOAT is right: keeping the rudders snug against the backstop with the ropes will prevent splay. I think the (new style) brackets are more than strong enough for their purpose. I always hard knock mine back before cleating them off to be sure they're back out of habit, having learned the "loose rudder" lesson on my first time out.

Just my two cents, having done this inspection yesterday. And thanks, OP, for pointing out this annual inspection point!