Composite rudder shafts

Wheel, tiller and autopilots
swanncat
Posts: 70
Joined: Mon Feb 19, 2007 4:33 am

Composite rudder shafts

Post by swanncat » Thu May 10, 2007 4:26 am

thanks 44c for the info on rudder shafts and staunchions sounds good..

regarding resale , i guess with the hours put into both building and THINKING we'll need the mill to break even .....

Whimsical
Posts: 370
Joined: Sat Apr 28, 2007 8:01 pm
Location: Fremantle W.A.

Composite rudder shafts

Post by Whimsical » Thu May 10, 2007 6:01 am

I make the assumption these parts fron exel are glass and not carbon. I was going to fabricate mine from carbon, what are the pro's and con's.

Mike

madaz
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Joined: Thu Apr 26, 2007 7:47 am
Location: Hobart, Tasmania

Composite rudder shafts

Post by madaz » Fri May 11, 2007 3:04 am

They are epoxy/glass.



As far as the pros and cons go, I am not all that up with technical stuff but Perry Cats used to use Carbon Fibre versions but have gone away from them as they were to brittle. They now use these. Also not mentioned in this topic previously i think is that you can also buy a matching rudder tube to match the shaft which give a setup a bit like the Roger Simpson method, A close fit from shaft to tube and the whole tube and shaft acts as a bearing surface i beleive. I am contemplating installing a grease nipple at the top of each of my tubes so i can regrease the assembly at any time with amarine type water resistant grease.

44c has ordered the tube and shafts together, my tubes are still on the way but apparenty the fit between the two is very good.

44c
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Composite rudder shafts

Post by 44c » Fri May 11, 2007 3:28 am

Carbon will cost more, but building your own would save money. Carbon would be lighter, but the glass ones aren't exactly heavy - without going out and weighing them I'd say the glass tubes and shafts are about 1kg each. (Total about 4kg for 2x shafts and 2x tubes) So your'e not exactly going to transform the boat by going carbon.

Carbon tubes may also be more brittle.



You would be doing very well to get as good a fit between tube and shaft as exel get.

Whimsical
Posts: 370
Joined: Sat Apr 28, 2007 8:01 pm
Location: Fremantle W.A.

Composite rudder shafts

Post by Whimsical » Fri May 11, 2007 5:56 am

My plans call for 50mm s/s shafts which I didn't like. Not just for corrosion and water penetration into the core but because if one takes a hard knock and bends then both rudders are inoperable. I would much prefer to have one snap off and leave the other serviceable.

Carbon would do this but maybe the glass version would be more resiliant and spring back, or snap if a huge impact. Might be the way to go.



Only problem may be in tapering them to fit the rudder sections. I suppose one could cut out a wedge shaped piece, bring the ends together and glass over.



Thanks

Mike



Edit - Gee the promtions come fast here- Galley hand already

madaz
Posts: 527
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Location: Hobart, Tasmania

Composite rudder shafts

Post by madaz » Fri May 11, 2007 7:43 pm

My plans call for 40mm stainless shafts, i ordered 50mm Epoxy glas ones from Excell, they may need a slight grind right atthe bottom of the rudder where it tapers but only 2-3mm and only at the very bottom which is not an issue.



I discussed these with Perry Catamarans before I ordered them and as mentioned they had used carbon fibre shafts prior but had issues with them being brittle. They have not had any problems with these epoxy glass ones.



Brian Perry also mentioned in the early days they used stainless, a boat backed into a sandbank, bent the shafts and as you said, lost all steering! it had to be towed back to their factory and required a significant destruction to the back of the boat to get the shaft out. His reasoning was the same, far better to snap a composite shaft and still have steering from one rudder than bend a shaft and be up shit creek.

northerncat
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Composite rudder shafts

Post by northerncat » Sat May 12, 2007 1:44 am

ah but if you make them well and you do bend one you just drop that rudder down fifty mm and hey presto freed up rudder that you still may have steerage off( its only a little extra thinking), or that you can disconnect from your connecting bar and steer off the other rudder, heck if your worried about needing or snapping one go with kick up rudders like the schionnings

sean

Smooth Cruiser
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Composite rudder shafts

Post by Smooth Cruiser » Sat May 12, 2007 3:09 am

I can add to the bent rudder discussion. Bushytales - when owned by her first owner - hit a sandbar at some not-insignificant speed. This resulted in both rudder shafts bending. The problem when stainless rudder shafts bend is that those shafts will never ever be completely round and true again, so they need either major rework or replacing anyway.



In this example the shafts were straightened then machined then machined again and at the end of the day the steering still has a tight spot. So bending steel is not as simple as bending it back again and off you go!!



I am trying to think how you would drop the shats 50mm to get steering back - I don't think I have room to raise or lower at all without some major mods to the tops of the shafts so I don't think this is a simple way out - I know that Bushytales needed towing to manouevre into the slip after this mishap.

Whimsical
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Composite rudder shafts

Post by Whimsical » Sat May 12, 2007 4:35 am

Yes you could disconnect the steering quadrant but this takes time. If I was in a situation where a shaft got bent I would think time to regain steering may be an issue, better to just have the thing snap off.

The Schioning rudder tapers quite significantly so I may need to do more than a little grind, will check it out.



I am oscilating between diesel sail drives and some form of electric propulsion. In these scenarios the fixed rudders would be nice to take some loading if the boat is to be dried out due to tide or intentional beaching.



Mike

northerncat
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Composite rudder shafts

Post by northerncat » Sat May 12, 2007 4:52 am

I am trying to think how you would drop the shats 50mm to get steering back



yes i can see that retrofitting it might be difficult, however if you design it into it its not to hard

as for disconnecting the rudders i intend to make this a five minute job

sean

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