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Length of C26 rudder shaft?

Posted: Mon Nov 07, 2011 8:32 am
by Windward
Back from Pamlico Sound and the Outer Banks of NC. Great time, wonderful weather, cooperative breeze, few mosquitoes, and unfortunately a rudder that is once again compromised. Stress risers from the numerous repairs seem to predispose the cheek plates to cracking, and rather than continue to bleed to death from a thousand paper cuts I think I need to start with a fresh sheet of paper -- a really solid rudder assembly built from scratch.

Does anyone know, fairly accurately, the length of the rudder shaft on the C26? I will pull the existing rudder to get final finish dimensions, but would like to order some 1.5" OD, .25" wall seamless 316 stainless steel tubing before I'm out at the boat next and don't want to end up too short. I believe the length is somewhat less than 36", so a 3' chunk will suffice, but don't want to come up short.

Looking at OnlineMetals.com, it seems the sweet spot of strength vs price will be that .25" wall shaft, welded to .135" 316 stainless cheek plates, with a separate 6" wide vertical reinforcement of .1875" stainless on both sides to minimize the stress riser where the shaft ends inside the cheeks. That's the point where I see most cheek plates develop their cracks. The IdaSailor blade is still in perfect shape, and no need to replace it.

Also, for you heavy metal guys (aka fabricators) out there, any particular points or techniques I want to discuss with the local shop to ensure it's welded up for the long haul?

Thanks!

Posted: Mon Nov 07, 2011 9:05 am
by EmergencyExit
Jeff, just happen to have one in my workshop from the other boat - if you don't have an answer by the time I get home I'll measure for you.

EE

Posted: Mon Nov 07, 2011 12:14 pm
by thepartydog
Very interested in this whole project. My cheeks were bolted to the shaft, and my shaft is bent.

Posted: Mon Nov 07, 2011 2:00 pm
by hp18carr
Jeff

As a point of interest, be sure to keep a record of all final numbers along with photos of each step if possible, I'm sure down the road a number of us will find them most agreeable.

Terrence
Wilmington N.C.
Chrysler 26' 1980
Pandora (for now)

Posted: Mon Nov 07, 2011 3:12 pm
by EmergencyExit
In my case 41" is the full length of the tube in my shop.

Posted: Mon Nov 07, 2011 5:13 pm
by Windward
Thanks! I really appreciate it. I found a cruddy Visio-based diagram I'd previously done that also had that dimension, so I'm taking that as confirmation. Materials alone on this little jewel are going to be at least 5 Benjies :cry: so trying to avoid mi$-steps.

Posted: Mon Nov 07, 2011 5:15 pm
by hotdot
This is a project I am very interested in. My c26 rudder assembly is due for an overhaul also.

Posted: Tue Nov 08, 2011 5:33 am
by sauerleigh
I would save a few bucks and go with 304 SS. If the boat was constantly in salt water, 316 would be the best choice but since your boat is basically a fresh water boat 304 will work fine. The biggest improvement will be going with the .25" wall tube instead of the doubled up version used on the original.

The cheeks are another matter. They could be made smaller than the originals. Any material 1" beyond your pivot setup, be it a single bolt or a larger slug, like I've seen on some models, is pretty much useless. It may look more finished with the elephant ears but the outer area provides no support for the rudder. I would make new cheeks out of .25" plate and add a piece of .25" bar along the top edge. Image

Any grinding or sanding done on stainless should be done with new wheels or sand paper. Carbon from other metals can be transferred into the stainless if you reuse abrasives. The same goes for wire brushes, they should be stainless not carbon steel.

Posted: Tue Nov 08, 2011 8:25 am
by Windward
Sauerleigh, that's great info. Is there an immersion duration after which I should use 316? I still haven't discounted the possibility of keeping Windward on the coast for a while, so don't want to save a small %$ but lose out in the long run.

I already had the 1/4" reinforcement added across the top of the current rudder assembly, and it really seemed to stiffen it up.

I'm really surprised that the rest of the cheek would not provide some support for the rudder, particularly if I were to use the .25" plate. If it doesn't, though, I could use 12" width for the cheeks instead of having to cut down 24" (working from stock dimensions from OnlineMetals) and $ave quite a bit. While 1/4" is more expensive than the .135" I'd been looking at, it would be offset by materials and labor from not adding the 6" reinforcement along both sides.

Is the design you pictured something you built, or a 3D model of what you have in mind? I noticed you've omitted the leading fairing block ahead of the shaft. If I did that, the rudder blade would have an inverted chin that normally meets the fairing block. I suppose I could trim that up. Is the force generated by that small surface area ahead of the shaft offset insufficient to contribute significantly to the rudder's balance?

Posted: Tue Nov 08, 2011 10:14 am
by Windward
Another question: Do they need to cut the radius on this stuff with a plasma cutter or what? Is there a thickness of stainless beyond which the labor costs for cutting/shaping become prohibitive, or is that thickness well beyond the 1/4" we're talking here?

Posted: Tue Nov 08, 2011 10:44 am
by sauerleigh
I sketched that up this morning (at work) from the vague memory I have of the dimensions from rudder post. I repaired my post after yours broke earlier this year, I think, and after looking at the design and the failures reported I came up with this idea but never put it to paper (PC). Carbon transfer is a big issue with stainless and also cooking a weld, which changes the metals properties. If you want the best corrosion resistance use 316. For me, even if I left a boat is salt water for a year, 304 would hold up, providing it was worked properly.

Even if you made the entire elephant ear cheek from .25" plate, it will still flex at the outer, unsupported edges. You have 3'+ lever arm with rudder which is trying to bend that metal.

Posted: Tue Nov 08, 2011 11:07 am
by sauerleigh
Any thing over 1/4" would be overkill. I do not know the thickness of the material that IDA uses on their kick up rudder posts or what MacGregor uses for theirs but I'd almost be willing to bet that it is not even 1/4".

The next big issue I have with rudder is the mushrooms, a good idea, but a poor design choice by Chrysler. I'm working on a different system which will still allow for flex between the hull and the deck, but does not pull itself apart even time a load is place on it. It will be a pain in the a-s to make, but it will work much better and will never need to be adjusted.

Posted: Tue Nov 08, 2011 4:51 pm
by Holiday
Be sure to use 316L or 304L. On Line Metals is top dollar you will do better if you can find a local fabricator that works in stainless and has stock material.

Posted: Tue Nov 08, 2011 10:43 pm
by Kevin Dreher
i was looking at the swing rudder on my 22, and wondering about how tough it would be to get rid of. I was thinking has anyone thought of or tried putting a regular rudder system on a chrysler sailboat. instead of the problematic through hull rudder....just thinking it might be a better option with some work. good luck with the repair.
kevin

Posted: Wed Nov 09, 2011 7:08 am
by hp18carr
Kevin

I have considered the same for my C26 overhaul project (rudder change) but being new to sailing I'll admit I feel I lack the skills necessary to make the switch. Also seeing that no one on this forum has taken this route... perhaps it could be more trouble than it is worth. Perhaps someone with the know how will pick up this idea.

Terrence
Wilmington N.C.
Chrysler 26' 1980
Pandora (for now)

Posted: Wed Nov 09, 2011 8:12 am
by EmergencyExit
Kevin Dreher wrote:i was looking at the swing rudder on my 22, and wondering about how tough it would be to get rid of. I was thinking has anyone thought of or tried putting a regular rudder system on a chrysler sailboat. instead of the problematic through hull rudder....just thinking it might be a better option with some work. good luck with the repair.
kevin

See here
viewtopic.php?t=193
EE

Posted: Wed Nov 09, 2011 3:01 pm
by clair hofmann
I've often thought about that. My Ventures have transom mounted rudders and theu're great. It would be easy to do. On a 26 you would have to fill in the motor mount opening and mount the motor off to one side. I plan to do that anyway. My questions are: will moving the rudder back change the center of effort relative to the keel and mast and what will the length and throw of the tiller have to be to reach into the cockpit?
Clair