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Rudder hanse 312

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GunnarJ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GunnarJ Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2021 at 08:24



RUD 34 rudder from Jefa. No vibrations or humming when clean, but turbulence from the prop when motoring is still there of course. A bit more balanced then the original one, but you can not let the tiller go, even for a moment when motoring. I have made a quick release/adjustable tiller lock for this purpose.


 

Edited by GunnarJ - 21 January 2021 at 08:34
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samuel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote samuel Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2021 at 08:54
Originally posted by perry perry wrote:

Bon Jour …ric,
I woulds be interested to know why you are buying a new rudder?.
It is a relatively straight forward boatbuilding job to build a new rudder. As you already have the shell that could be split and removed from shaft, the time consuming molding work is already done.
A new shaft for example might be :- material cost eur 200. turning and milling the keyway and holes for tangs [the pins that stop shell rotating on shaft 400 euro, tangs and fitting tangs 200].
GRP work to fix tangs in place on half shell, fill with structural foam and finish joining the two halves. Finish and fair the joints. A better rudder can be made by fitting a bushat top of shell with "O" ring [toroid joint] seals to shaft and laminated to the shell. Earlier Jefra designs just used Sika flex to seal in this area with instruction to regularly check and replace? I dont know where your based but can reccommend a boatbuilder in La Rochelle.
I would expect the Jefra option  to cost >2500 euro
Perry


Personally I would be careful of going away from the jefra route. They have videos of how they make their rudders & they make the tangs in a different way so that they give support to both sides of the blade. They also make a better job of injecting the resin than the manufacturer of my first rudder shown here. You can just make out the 3 tangs & they were only bonded to one side. One can see where the foam was missing.
I would also point out that the general profile of the Jefra rudder is know to work. If one cares to search way back into the forum archives there are horror stories of badly made rudders supplied by hanse to the 300 series, that either allowed the boat to broach, or had vibration problems.
What is another few  euros in the grand scheme of things if one may well have another bad rudder.
I would also make sure that the problem is not one of slack bearings. The pins at each end of the bottom rollers are very small & it may be that a couple have worn & in some way they have become dislodged- although I am not sure if they could actually drop out. Coupled with wear at the top & movement would be multiplied greatly




Edited by samuel - 21 January 2021 at 08:55
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perry View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote perry Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2021 at 10:31
Thanks for sharing your knowledge. I was aware of some historic rudder problems. And I banged on about poor design when I first bought my 301, it had seized rudder bearings problems.

As an excuse I am an old Git;  [virus jab tomorrow]  with far too much history of  boat/boatbuilding/ boat designer issues. I have put to sea in boats that I  have designed and built the Keel, mast and rudders for and had no problem; I have put to sea in boats from respected manufacturers and designers and had problems, due  to either design and/or manufacture.

To be clear I should not advise people to stray from the likes of Jefra or Hanse. What worked for me, may not work for others!
So in summary I agree with you and your good advice, boat owners should stick to the manufactures.

Just to try and justify my old Git status, when I first had problems with the H301  60mm aluminium rudder stock I offered my solution was to use Duplex Stainless tube, its high strength and total lack of corrosion problems weldability etc mean it can be as light as aluminium by way of  smaller diameter and tubular. The smaller diameter makes plain bearing an option, because needle roller type bearings dont like crustation invasions.
I see Jefra "racing rudders" now offered with Duplex and the thinner section makes for a thinner rudder? Thats progress,  or learning on the job? Some of the vibration just might be due to the thick NACA sections [low speed aerofoils running too fast] needed for thick rudder shafts.

I'm currently correcting  an assymetric rudder problem on my wheel steering 315 [2007]. The drag link arm was fitted [presumably by Hanse] is 860mm long, the tiller arm is keyed at 10deg offset. The correct setup is 5 deg key offset and drag link should be 780mm. The drag link cannot be set below 800mm long so the builder turned the tiller arm over fitting it with 20 degree offset, this makes the steering totaly assymetric.  I am currently correcting both these faults to get my steering corrected. I appears to have come out of factory like this. These type of faults do little to asswage my lack of confidence in yacht  design or build getting it right.
Regards Perry
not quite a rant but I feel better!


Current Yacht Hanse 315 2007
Last Yacht Hanse 301 Round GB in 2017
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samuel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote samuel Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2021 at 11:15
Originally posted by perry perry wrote:

I see Jefra "racing rudders" now offered with Duplex and the thinner section makes for a thinner rudder? Thats progress,  or learning on the job? Some of the vibration just might be due to the thick NACA sections [low speed aerofoils running too fast] needed for thick rudder shafts.

Jefra has been making a "racing" foil for some years.It was available to me in 2014
Going off thread a bit here; but are you sure that a thinner rudder is actually better for the lower speeds that one gets in the smaller, displacement, yachts.
I do not know. Only surmising !!
Most 300 series do not sail more than 6.5kts that often. Yes, many have all done the 11 kts surf now & then, but the last thing on their mind is if the rudder is vibrating
One might ask the question- does the thicker section  give greater lift &, therefore, better response to steering? just having a thinner section may actually induce stalling. It may also reduce the blade strength in the bottom third of the blade where there is no  support from the post. Certainly not from a tube, unless it is engineered with a taper thus reducing its strength.
The bottom third needs to be structurally sound because a vessel may have a light grounding & put a bending force on the blade , thus causing failure. As in my case.
One design issue I have is that the blade is almost as deep as the keel. I regularly ground in the soft mud coming into my marina at low tide & i have to be very careful of the rudder if I reverse off. Any strain on the tiller & i stop immediately.
Daydream Believer- Hanse 311- No GBR9917T- Bradwell Essex
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perry View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote perry Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2021 at 11:59
Yes your right the thicker sections stall later but more drag which is what worries the racing person.
the extreme high aspect ratio rudders seen on race designs with narow cord and thin sections parabolic plan forms maximise efficiency eg minimum drag for max lift, well they stall suddenly with little warning. Checkout some of Bekens broaching yacht pics.

Conversly the old barn doors hung on back of long keel or skeg mounted with little attempt at balanced aerofoil, great wide cord with little attempt at aerofoil sections dont really 'fly', so the difference between attached flow [flying] and stalled flow are hard to feel, and even when deep in stall may still help to push the stern sideways??


Edited by perry - 21 January 2021 at 16:23
Current Yacht Hanse 315 2007
Last Yacht Hanse 301 Round GB in 2017
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samuel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote samuel Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2021 at 16:31
Originally posted by perry perry wrote:

Yes your right the thicker sections stall later but more drag which is what worries the racing person.
the extreme high aspect ratio rudders seen on race designs with narow cord and thin sections parabolic plan forms maximise efficiency eg minimum drag for max lift, well they stall suddenly with little warning. 
Which really confirms that the average cruising sailor on boats like the 311 should not have skinny rudders & should stick with the standard Jefra rudder. A cruising sailor is not going to have crew constantly watching for the stall like a racing crew & wants a comfortable sail. 
In the grand scheme of things, a skinny rudder would be a backward step for the owner of a 311 & ( as you say)Jefra probably know what they are doing.


Edited by samuel - 21 January 2021 at 16:34
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EricT View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EricT Quote  Post ReplyReply Direct Link To This Post Posted: 21 January 2021 at 17:29
 Thank you for your comments, I understand better the different technical aspects of this rather complex problem! Iím currently hesitating between modifying the old one or buying another one....
 kindly …ric
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EricT Quote  Post ReplyReply Direct Link To This Post Posted: 08 February 2021 at 08:56
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EricT Quote  Post ReplyReply Direct Link To This Post Posted: 08 February 2021 at 09:01
hello everybody 

Finally I chose to modify my rudder. I cut it by 15 cm, changed the upper part and improved the profile... I hope my choice will be beneficial! I'll give you my impressions in April.
…ric 
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