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Old 10-09-2013, 18:06   #61
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Re: ANOTHER Hunter rudder!

So you mean is a solid stock? doesnt matter if is a 80 or 2004 or 2011 , just wonder if Hunter change their mind about Foss or is still supplying rudders to Hunter ...
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Old 10-09-2013, 18:11   #62
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Re: ANOTHER Hunter rudder!

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Originally Posted by transmitterdan View Post
I think Uncontrollable Urge had a CF rudder post fail in deep water. The US Sailing report said it failed just below where the post exited the hull. The rudder post failed on S/N #1 of the boat type too in not difficult conditions. It was a CF tube. UU's rudder was made "stronger" by using solid CF rather than a CF tube. I would not want a CF spade rudder on my cruising boat until more is understood about that technology and application.
Thx for the info, i just believe CF is lighter and stronger than regular FG and even in some cases stronger than SS, repairs can be made in the same fashion as normal Fg , but anyway i dont know the circunstances or the reason why this 2 Cf rudders fail.
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Old 10-09-2013, 18:37   #63
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Re: ANOTHER Hunter rudder!

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If they don't fill the shaft, what do they do? A hollow shaft is weaker than a filled shaft, all other things being equal.

Fabbian
I think if you do a finite element analysis of the tube you will find it is not much stronger when filled with something. The side loading forces on the the shaft cause tension on one side of the tube and compression on the other side. The tension stresses are not much affected by the filling material. I think the main reason for filling the tube is to make the rudder lighter by displacing water.
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Old 10-09-2013, 18:59   #64
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Re: ANOTHER Hunter rudder!

Raku, I don't say that our experience was the norm. I only said that it happened. That the original order was built to the wrong dimensions, the original shipping deadline missed, and the subsequent dealings made little to no accommodation for "Gee, we screwed up and now your boat is going to be out of the water for a long time."

That's multiple failures. Maybe someone was distracted, I don't know, that shouldn't have been our problem. I only know that other vendors would have voluntarily worked harder and faster to correct the error. One of the options we discussed was having the rudder "corrected" locally, in order to save the two weeks of transit time (motor freight) and expense of shipping it back and forth to them again. Nope, they didn't want to hear about it at all. Didn't make any effort to do anything besides say "send it back and we'll do it again." Which turned into about a two month wait. I don't know who was in charge at Foss, and I wasn't the one discussing it with them. But I sure do know, the only way they could have failed more would have been if they had closed up shop and kept both the rudder and the payment for it.

You like 'em, by all means, keep using 'em.

If a thousand people eat at a sushi bar and only two of them get food poisoning, is it still a good sushi bar? 998 people would say yes. Two would say that even two is totally unacceptable.
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Old 10-09-2013, 19:04   #65
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Re: ANOTHER Hunter rudder!

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Originally Posted by fgd3 View Post
If they don't fill the shaft, what do they do? A hollow shaft is weaker than a filled shaft, all other things being equal.

Fabbian

It's high quality stainless steel. I forget the number -- don't have the background knowledge on the different types.

It was a VERY hard bang on the bottom of the river, and I don't fault the rudder. I think, as Anne Cate reported about another type of boat, that the rudder is designed to take the blow to protect the boat -- which is what happened in my case.
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Old 10-09-2013, 19:07   #66
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Re: ANOTHER Hunter rudder!

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I think if you do a finite element analysis of the tube you will find it is not much stronger when filled with something. The side loading forces on the the shaft cause tension on one side of the tube and compression on the other side. The tension stresses are not much affected by the filling material. I think the main reason for filling the tube is to make the rudder lighter by displacing water.
No, the reason for filling the tube is to prevent the walls from buckling. When you side load a tube beyond its limit the inside wall deforms and creases. If you can prevent that from happening with a crush resistant filler you can enable the tube to withstand higher side loads without failure.

Fabbian
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Old 10-09-2013, 19:25   #67
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Re: ANOTHER Hunter rudder!

Has anyone addressed crevice crack corrosion on the stainless shafts for these rudders?

Could easily be a design flaw in how the shaft enters the stuffing tube.

Just normal sailing could break them off if they are set up to fail....
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Old 10-09-2013, 19:41   #68
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Re: ANOTHER Hunter rudder!

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Has anyone addressed crevice crack corrosion on the stainless shafts for these rudders?

Could easily be a design flaw in how the shaft enters the stuffing tube.

Just normal sailing could break them off if they are set up to fail....

"Normal sailing" did do something catastrophic to Jopie Helsen's boat. I don't know what, but actually I can find out.

While the seas were not good, 15 - 20' waves if I recall correctly, I would expect a 47' boat to be able to handle that. He is a skilled sailor and everyone on his teams have been too, so I would tend to discount any suggestion of sailor error.
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Old 10-09-2013, 20:16   #69
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Re: ANOTHER Hunter rudder!

"A hollow shaft is weaker than a filled shaft,"
Only marginally. This is why spinnaker poles, masts, booms, structural support columns in buildings, are all unfilled columns, not solid posts. Unless your "filling" is quite substantial, it contributes very little. Even when it is quite substantial, it doesn't add much compared to a slight increase in column wall thickness.
A typical rudder post is supported internally in the rudder tube, and then externally inside the rudder itself. There is really very little rudder post exposed in between the hull and the rudder, which could be subject to buckling from side loads. It is fairly simple to make the post stronger than the hull or rudder which are attached to it.

And again, if the post is stainless steel? Doesn't matter if it is filled or not, it can still fail from crevice corrosion. Stainless is the wrong metal for this application.
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Old 10-09-2013, 20:32   #70
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Re: ANOTHER Hunter rudder!

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Originally Posted by neilpride View Post
So you mean is a solid stock? doesnt matter if is a 80 or 2004 or 2011 , just wonder if Hunter change their mind about Foss or is still supplying rudders to Hunter ...

Foss Foam builds Hunter rudders -- following Hunter's specifications.
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Old 10-09-2013, 20:39   #71
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Re: ANOTHER Hunter rudder!

Raku-
Foss Foam also does business under the name "Newrudders.com" and if you look at their web page on NewRudders.com Rudder Care you will see their statement that their rudders must be painted white, not dark, or else the heat will damage them:

"We recommend that white paints be used. ...
We do not recommend the use of dark color bottom paint for your rudder, as they generate heat whenever your boat is out of the water and in the sun. Since your rudder is made of cellular material this heat can cause dimensional changes and cosmetic damage. If the rudder is painted a dark color it should be shielded from the sun with a white wrapping whenever the boat is out of the water. YOUR RUDDER WARRANTY EXCLUDES DAMAGE CAUSED BY HEAT. "

OK? You don't have to believe me, you can read it directly from them. Now, did anyone tell you that about your rudder? Have you ever heard that rudders can't be painted with the same dark bottom paint as the rest of a boat?

Sure, I believe their warning, for their product. I just find it most peculiar compared to the rest of the rudders in the world. Invulnerable closed cell foam...that can melt on a hot summer day. Hmmm...
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Old 10-09-2013, 20:46   #72
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Oh well, I'll just keep sailing my 60s boat with solid bronze rudder post and not worry about crevice corrosion....
Bronze isn't probably strong enough for unsupported rudder, but I wonder why skeg hung rudders nowadays aren't built with bronze posts. Probably boat builders don't want to pay more for the metal. Heaven forbid several hundred more in cost....
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Old 10-09-2013, 20:51   #73
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No, the reason for filling the tube is to prevent the walls from buckling. When you side load a tube beyond its limit the inside wall deforms and creases. If you can prevent that from happening with a crush resistant filler you can enable the tube to withstand higher side loads without failure.

Fabbian
The pressures from a buckling tube are enormous and no foam could withstand it in my experience. I would be very interested in any real world test showing a significant increase in failure moments due to high density foam filling a thin wall SS tube.
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Old 10-09-2013, 21:02   #74
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Re: ANOTHER Hunter rudder!

Dan, it is common when bending thin copper tubing (icemaker water lines, etc.) to fill them with sand if you don't have a bending spring, before bending them. The sand prevents them from collapsing on the bend. So filling a tube DOES work, but everything depends on the relative merits of the tubing wall and the filling material. If you had an unlimited budget and really wanted to max out the rudder post, you could insert multiple tubes inside of it, snugly, and "honeycomb" the rudder post making it almost as strong as a solid rod but at greatly decreased weight. And of course increased cost.

Bronze got a bad name when the "miracle" of stainless steel cookware and knives was sold to the world in the (50s?). Tell a boat buyer you are using bronze parts, bronze structural parts, and you'll frighten them away. Bronze, that's like, something that came in between the stone age and the iron age, right? No sale. Forget the price, no sale.
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Old 10-09-2013, 21:04   #75
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Re: ANOTHER Hunter rudder!

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I know that keel manufacturers often add antimony to the lead to make it a bit harder, perhaps to make the keel bolt attachment more secure. This addition reduces ductility, of course... so I wonder if the Hunter keels have unusual amounts of antimony added? Do you (or anyone else) have any info on this?
If some one would like to send me a small sample from a lead keel, I can do a Brinell test & give you a pretty good idea of what the antimony percentage probably is. The sample can be as small as a 10mm cube.

I can test it as-is & then test it again in an annealed state to also check for the effects of hardening. Antimonial lead alloys harden from heat treating. They partially harden from aging after being cast. They work soften from stress, unlike most steel alloys that work harden.

High percentages of antimony, as commonly found in alloys like sterotype, monotype, lineotype & most Babbitts, can cause a casting to be quite brittle under certain conditions. There are other metals that can be alloyed in to add malleability & reduce surface tension so as to produce improved quality castings. I can do heat/color tests to check for the presence of some of the other common alloy elements.
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