Rudder Posts - stainless v. composite

[Eric Collins]

I'm replacing the rudder on Kokopelli, curious what others think about rudder post materials.  The existing rudder has a stainless post, but I understand some boats have fiberglass and some have CF rudder posts.  

Are the composite posts the same 2" diameter as the stainless?

 

[John S]

Eric,

As far as I know the rudder post diameters are the same, regardless of material. I have never encountered or even heard of a CF rudder post on a SC27, but there may be a few out there. The fiberglass posts (I have one on my boat) are a pulltruded sold shaft that is very dense and hard. As for which is better/preferable I don't really know. SS may be more readily available. I did hear someone opine once that the 'glass shafts spring back after bending. But you would have to really hit something hard to bend a rudder shaft.

Where are you getting your replacement rudder?

John

[Eric Collins]

Well, I guess I learned how hard you need to hit something to bend the stainless rudder shaft.  We hit a partially submerged tree branch or something flowing down the Columbia River when the river was at flood stage.  The impact was jarring, but I didn't suspect any damage at the time.  It took a half-inch swath of VC17 off the leading edge of the rudder, but no visible damage to the gelcoat.  Bent the rudder about 10 degrees to port.  I was surprised that an impact hard enough to bend the SS shaft left so little evidence.

Looking at Betts, Elkhorn and Waterat.  

[Andy Schwenk]

betts

[ray.mc...@comcast.net]

Eric,

Was the bend along the axis of the rudder, or off at an angle?

--
Ray McCormack
360-609-1346
http://www.mackconsult.com/
facebook
linkedin

This message, including any attachments, may contain information that is
confidential and proprietary information of McCormack Consulting, Ray McCormack, or the McCormack Family. If you are not the intended recipient, you are hereby notified that any dissemination, distribution, use or copying of this message or any of its attachments is strictly prohibited.

---

From: "Eric Collins" <0eric.c...@gmail.com>
To: sc2...@googlegroups.com
Sent: Tuesday, March 6, 2012 1:27:33 PM
Subject: Re: Rudder Posts - stainless v. composite

[Garman, David M]

Many SS rudder post have been bent, and straightend. Some have had failed welds in flags and the main shaft. The SS is actually schedule 80 1 1/2  welded pipe and is slightly less than 2", either at 1.909 or 1.939 depending if seemless or welded., The lunistrand pultuded green glass (E-glass) is close to 2" diameter.  The lunistrand is +- 0.003 off diameter. The Lunistrand is slightly less weight than the SS pipe.  Flags in the lunistrand are 1/2 rounds of the same material.  Usually, the lunistrand has a thin stainless bushing, 0.005 wall protecting it from the lower bearing.  From what i know, the few CF rudder posts are at 2" diameter. There are many lunstrand rudder posts. The few failures in the lunstrand have been the top bambooing from having the wrong rudder cap. SS rudders tend to have problems with freezing, in places it freezes. lunistrand has the same coef as the foam and vynal ester.

 

Hard to beat Betts or Elkhorn, just depends how much money you have.  You might want to put in a real bearing if you are going to the trouble of replacing the rudder.

 

 

---

From: sc2...@googlegroups.com [mailto:sc2...@googlegroups.com] On Behalf Of Eric Collins
Sent: Tuesday, March 06, 2012 1:28 PM
To: sc2...@googlegroups.com

Subject: Re: Rudder Posts - stainless v. composite

[John S]

David,

It's always nice when some real engineering information surfaces. I have a couple of questions:

What do you mean by "flags" in the lunistrand? I had to make a minor repair years back to mine where it had cracked at the top from torsional loads on the bolt that runs through the cap that holds the tiller. I basically pried it open as best I could and worked some epoxy in there. That stuff was VERY difficult to flex enough to open up that crack. Anyway, the end of the shaft looked like it was all uniform glass strands with no visible structure to it, just a bundle of glass threads.

Do you know what's in the boats for a lower bearing? Express 27's have a delrin (or some similar plastic) bearing that can be replaced. (I know of one E27 that has done this. Not sure where the bearing was from, maybe Ballenger.) But when I've looked into the rudder tube when I've had the rudder out, I don't see any similar structure. (I also don't recall any stainless bushing on the lunistrand shaft, either.)

Anyway, thanks for the technical info on the rudder shafts.

John

[Garman, David M]

Tom Abel (sc27 former owner) will make you a new Delrin bushing for the top and bottom that matches your shaft, or at least he was making them last year.  email attached  he made SC27 rudders for a while too, he still might, not sure.  Check with Tom for pricing.  He also knows a thing or too about SC27 rudders.  Best to get with him in the winter, he likes to go sailing in the summer.  Many boats have the lower bearing captured into the hull with glass, and this must be trimmed to remove the bushing.  The top bearing is helped by putting a screw clamp (hose clamp) around the busing and this will tighten the bushing round the top of the shaft to remove wiggle, tighten more over time.

 

All boats came with a pvc tube with the bell ends used to hold the delrin bushing into the bell.  That is what most boats still have.  The boats with CF or Lunistrand will benifit from having a stainless very thin sleeve between the Delrin and the Lunistrand, the Delrin is tougher and will eat into the Lunistrand over time.  The SS sleeve will keep any degredation of the delrin and the lunistrand.  Run this without lubrication. If you dont have a sleeve and want to build up the area eaten away, use vynal easter resin, and sand very smooth.

 

Lunistrand is a pull-truded product, basically they pull and push it to extrude the round from a die while the material is curing.  There is goo and long strands of E-glass and low-e modulus vynal ester resin and is still used for transformer insulators.  This stuff is tuff, but can splinter if crushed and twisted. hum, i think i will use it in my rudder. 

 

The flags are in the body of the rudder to keep the shaft from spinning in the rudder blade. They are just drilled and re-bonded with resin for the lunistrand shaft.  There are 4-5 flags depending on age. They are 1/2 diameter lunistrand.   The SS shafts have SS flags that are welded to the shaft and size varies by who was making the shafts.  Usually, water gets in and freezes and splits the rudder open over time.

 

I dont know what the CF uses for flags, but they likely have them. AYou could ask Elkhorn Composites.

---

From: sc2...@googlegroups.com [mailto:sc2...@googlegroups.com] On Behalf Of John S
Sent: Tuesday, March 06, 2012 4:34 PM

[Warren Pelz]

Hey Eric,

I just replaced my SS shaft rudder with a Lunastrand type. The SS shaft was used in the earlier boats and like Dave said, it's pipe not tubing. Pipe is not nearly as true as is tubing. They bought 20' lengths so every 4th or 5th shaft was 2 pieces welded together (not terribly reassuring). I'm of the opinion that they switched to lunastrand to reduce failure rates. I know 2 guys who've bent and or broken SS shafts when coming off a wave surfing down the coast. My lunastrand shaft is slightly larger than was the SS shaft. It is imperative to have the SS shim epoxied (no 5 min. epoxy) to the lunastrand to protect and isolate the shaft from the delrin. I siliconed the delrin  into the hull 'cause you don't want movement there but may need to replace it later.

I did a little research into bearings and surmised that the delrin was my best choice. All the bearings I found were intended for much flatter hulls.

The "bambooing" that Dave mentioned, where the lunastrand splits from the through bolt torque, is most often caused by insufficient clamp pressure at the rudder head. The bolt is not really intended to take any torque. It's just there to keep the rudder from inadvertently falling out. The 2 most common remedies for a loose rudder head are to shim between the rudder head and shaft or re-cut the slot at the top of the rudder head both wider and longer.

Hope that helps,

Warren

On Tue, Mar 6, 2012 at 10:03 AM, Eric Collins <0eric.c...@gmail.com> wrote:

[Eric Collins]

Thank you all for the very informative posts.  I'll look into a pulltruded rod shaft, sounds like a marginally superior material to SS.  Warren, where did you source yours?

[Warren Pelz]

Hey Eric,

I got really lucky. I met another 27 owner who happened to have the rudder from Mach 5. I know of 1 more out there too. The guys name is G W Grigg. He single handed the 27 Velocious in the Trans Pac. The only # I have is (408) 205 0584. Good luck, he wouldn't sell it to me. He doesn't even have a 27 anymore, the punk. And, it's being stored in someone elses garage. I'd be happy to give away my old SS but it's one of the welded ones and  I've had to straighten it......It's destined to fail. I can ask Homer, if you'd like, he built most of our rudders and told me recently he knows where to get lunastrand.

Cheers,

W

[Ian Sprenger]

Reviving an old thread here.....

I'm looking to replace the SS sleeve for the lower rudder bearing.  2" ID x 2 1/16" OD is what I'm coming up with.  I've looked everywhere, including Mcmaster Carr and can't find this combo.  Is this a magical size that only existed in the hills of Soquel in the 70's? 

Thanks,

Ian

[David]

No idea. I don’t know where to get one

Sent from my iPhone

--
You received this message because you are subscribed to the Google Groups "Santa Cruz 27 National Class Association" group.
To unsubscribe from this group and stop receiving emails from it, send an email to sc27nca+u...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Charles Abraham]

Matt Coale (rigger) did our bearings years ago. I would suggest you check with him.