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Building an O30 elliptical rudder


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For a winter project I'd like to build my own O30 elliptical rudder (to get better control downwind with my autopilot).   I've got the design from the O30 website.  But I have some questions:

On youtube I've seen rudders that were just very hard foam mounted over the shaft, then covered with fibreglass, etc.  I've also seen rudders with horizontal pieces welded onto the shaft to define the shape before the foam was added.  Which is better for this project?

The design plans have the outside measurements, so I have to recalculate the size of the foam to take the fibreglass and coatings into account.  How thick is fibreglass?   How many layers of fibreglass do I put on the sides?  The leading edge?

What is the best way to measure in the proper shape of the foam?

Do I fill the stainless tube rudder shaft with foam to keep out the water?

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I doubt a ss shaft without tangs (i.e. the horizontal pieces you refer to assuming I understand you correctly) is going to work.  Without tangs the blade will quickly break from the shaft and spin about the shaft I would think.

Filling the tube with foam won't hurt, but not going to do much good either.  The entry point of water is at the annulus between the outside of the shaft and the rudder at the rudder neck.

Layup thickness is, not a dead simple derivation.  Depends to a degree on your lam schedule, i.e UD with some triax say multiples of 3 UD/1 triax  Probably want kevlar along the leading edge.

Or perhaps an easier way to obtain a lam schedule is to contact Foss Rudders in CA and ask for the specs of their O30 rudder - which actually looks a lot better than the class elliptical one - and I assume you are only interested in greater control - not being class legal.  Below is the Foss Rudder:

I like that the Foss rudder has much less root area than either the stock or class elliptical one.

O30-Rudder-Foss.jpg

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If I were doing this project I'd opt for the more modern "Foss" design rudder (with the spelling-challenged title on the drawing!).

Make note of how this diagram has a significant error - later corrected in the production of the rudder itself. I think they've made ~ 5 of these for the Olson 30 in the last several years.

Rudders with stainless shafts have an internal armature welded to the shaft. I'd like to know - out of curiosity - what sort of internal structure is in the original rudder with the pultruded fibreglass shaft.

I manage olson30.org and I have some other images of the Foss rudders, I will add them some time soon.

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3 hours ago, yoyo said:

That Foss O30 rudder looks nice but it might be a PITA to remove weed/kelp if that's an issue where you sail.  

That's why I wouldn't consider it.  We've got lots of kelp here and with the standard O30 rudder I often cut right through the kelp patch, while other racers are forced to divert.

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Building a rudder yourself is probably not the best idea. All of the Youtube videos in the world will not help you. Unless you have a ton of experience with this kind of engineering and composites, you risk serious issues which can ultimately lead to failures. People have died due to rudder failures. Even the professionals have trouble at times building a properly strong rudder. Not trying to rain on your parade but you do need to consider the ramifications regarding safety, resale, insurance.

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1 hour ago, Foolish said:

That's why I wouldn't consider it.  We've got lots of kelp here and with the standard O30 rudder I often cut right through the kelp patch, while other racers are forced to divert.

I used to race at RVic many years ago and while kelp was something to keep an eye out for year round it was only really problematic for maybe one month of the year.  Sometime in the spring IIRC.

Once you learn to back down (a pre race ritual there) kelp isn't so much of an issue.  With practise you can back down a boat length  and be under way again in less than a minute.

My boat had an outboard rudder so would be considered a kelp catcher and I can think of only one instance where I got really bogged down - and boy it was a doozy.

But the Foss rudder looks just so much better from an interference drag perspective.

Of course the other rudder company to look at is Jefa: https://www.jefa.com/  They have a very large range of rudders and steering products and have drawings of the layup and lams as well.

PYI carries Jefa in Washington State https://www.pyiinc.com/

Rekord Marine in Vancouver carries the jefa line in Western Canada.

And as other have said, probably not wise to build one yourself.  Especially when you can get one for a reasonable price from a place like Foss or Jefa. 

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On 10/15/2020 at 10:09 AM, Irrational 14 said:

Building a rudder yourself is probably not the best idea.

Wow, you guys are pessimistic.  It's the fun of it mostly.  I'll see how it goes.

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2 hours ago, Foolish said:

Wow, you guys are pessimistic.  It's the fun of it mostly.  I'll see how it goes.

Oh yeah.  Forgot that you single hand mostly, or maybe entirely.  If that's the case, then knock yourself out.  But you should really do some more research into such a project before beginning because it is not the simplest task.

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