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Old 11-11-2018, 15:53   #1
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Fabricating a new Spade Rudder

It looks my rudder stock broke due to anaerobic corrosion of the monel steel around a foot down from where it entered actual rudder itself. A stress crack, probably the result of some unknown mishap years ago finally reared it's ugly head when on a reach I suddenly lost steering and saw what was left of the rudder alongside....



Its a light weight Phrf mid eighties sailboat. With a 1 1/4" (probably some metric value) rudder stock.



The rudder itself is a straight foil right to the end, no tapers, etc. around three feet long.


Anyone got any ideas on fabricating this (apart from the stock)?
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Old 11-11-2018, 16:43   #2
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Re: Fabricating a new Spade Rudder

It is a fairly simple fabrication but you have to be meticulous in the fabrication.

I started with 1¾ in. SS round bar and had some SS tangs welded to it.
The heat caused the round bar to bend slightly so I straightened it using a pipe bender. (But you could also use a 5T press or similar)

I then cut marine ply to butt up to the round bar and tangs. Then filled any voids with epoxy bog (talcum powder as the filler). Then fitted marine ply to either side of the tangs and shaped it to a taper. Finally I laid up about 8 layers of cloth/epoxy (covering the stock as well.)

I finished off the rudder with five coats of barrier coat.

The following link gives images of the process. If you want any further information on a particular image just click it and if you was further information still, click "visit" and you will get the article from which the image was taken.


https://www.google.com.au/search?q=f..._s4kZCLQ5_xfM:

There is also a stack of videos too.

https://www.google.com.au/search?q=f...h=494&dpr=1.65
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Old 11-11-2018, 18:27   #3
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Re: Fabricating a new Spade Rudder

Are you sure that the old stock was monel? That's a fairly expensive material and not so often seen in that application.

For the new one, you might consider 2205 duplex s/s. A lot stronger than 316 (the most commonly used alloy) and far less susceptible to various forms of corrosion.

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Old 11-11-2018, 21:25   #4
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Re: Fabricating a new Spade Rudder

Here is a simple rudder being built. Ply laminated with epoxy.
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Old 11-11-2018, 23:02   #5
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Fabricating a new Spade Rudder

There are plenty of NACA profile generators freely available on the web. I used one to plot and print the foil cross section for my wind vane auxiliary rudder, traced the profiles onto 6 mm 316 stainless sheet and welded these to a 1.5 inch stainless tube. (Tube obviously not strong enough for your situation but same technique would work.). Then a layer of ply either side of the foil and filled with pour foam. Coat the result in epoxy glass. 80/20 balance. You would have the advantage of using the current rudder for a template on the whole balance point which is a tricky decision. (That is, if you managed to salvage it, otherwise measure the rudder from someone with the same boat)
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Old 12-11-2018, 05:49   #6
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Re: Fabricating a new Spade Rudder

Not that you're going to build it out of stainless but some of the fabrication principles are there and it's a very detailed video series by a talented fabricator.



I had to replace the rudder on my 37' Dickerson last season after a grounding. Since it was an insurance deal, the yard contracted with Foss Foam in FL to make a new one. Hard to tell, but seems very well made. I don't recall the cost but thinking it was maybe $4k for the rudder.
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Old 12-11-2018, 08:20   #7
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Re: Fabricating a new Spade Rudder

I replaced two (catamaran) before crossing the Pacific. Was pitting and just wanted to be safe.

They used the old rudders as a mold and had a fabricator do the metal work.

Still remember the price tag, 13k :-)

If I had done it, well, still would not have slept at night.

Good luck!!!
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Old 12-11-2018, 08:21   #8
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Re: Fabricating a new Spade Rudder

Here is an example of building a rudder which might give you ideas..

https://she-kon.blogspot.com/2017/08...ng-things.html
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Old 12-11-2018, 08:40   #9
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Re: Fabricating a new Spade Rudder

Split the existing rudder shell and replace the metal part. No need to make a whole new rudder blade.
Saw it with a skil saw at the front, top, bottom and pry it open. You can saw it at the trailing edge also as you can re-layup that when you finish.. Once the new metal is installed glass over the whole thing, fill with something ( I prefer a light weight epoxy or resin slurry) and grind smooth.
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Old 12-11-2018, 08:52   #10
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Re: Fabricating a new Spade Rudder

Foss Foam is a great source as mentioned above. Williston, Fl have all the molds so might even have yours already. Call Al there 352-529-1104 or their web site https://www.newrudders.com they are 3rd generation family business.
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Old 12-11-2018, 09:43   #11
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Re: Fabricating a new Spade Rudder

What Cheechako said. I have done a shaft-ectomy with great success. Just replace the broken part. Good luck
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Old 12-11-2018, 09:55   #12
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Re: Fabricating a new Spade Rudder

2nd vote for Foss, they had the mold for my Islander and it cost $1700 and took less than 2 weeks. Plus these guys are so good to deal with Don had the rudder shipping out before he even received my payment!
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Old 12-11-2018, 10:12   #13
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Re: Fabricating a new Spade Rudder

Check out a company by the name of Ruddercraft in (of all places), Boise, Idaho. They made a new centerboard (8’ long, 20.5” chord, NACA airfoil crossection) for my Irwin sloop. I’ve been to their facilities and have seen their layup and vacuum bagging capabilities. Very top notch company. I am very happy with their product, price and timeliness. They make rudders, centerboards, leeboards, et al.
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Old 12-11-2018, 10:52   #14
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Re: Fabricating a new Spade Rudder

Try Fast Composites - http://http://www.fastcomposites.ca/...09960937500000
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Old 12-11-2018, 11:11   #15
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Re: Fabricating a new Spade Rudder

I was looking at your pictures, it appears you have a fractional skeg mounted rudder (not sure if that is the correct term) but mine is the same. I have a 34 Pearson, and my rudder just broke also. I was able to remove it in the water because the 1-1/4" shaft broke clean at the top of the rudder. It weighs 140 pounds (on my bathroom scale). I cut it open and found it is solid fiberglass with a 3 foot steel plate down the center that WAS attached to the shaft. It also bent my bronze lower bearing which I will have to have foundered. I have a great welder for the 316l and I will be doing the fiberglass my self.
I see your from Mass. I'm originally from Saugus but now sail year round out of Galveston Texas. I have a few pictures, Contact me if I can be of any further help.
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