The International Canoe

The forum for the International Canoe
It is currently Wed Dec 19, 2018 1:27 pm

All times are UTC




Post new topic Reply to topic  [ 15 posts ] 
Author Message
 Post subject: Rudder pins
PostPosted: Thu Jul 23, 2009 7:14 am 
Offline

Joined: Mon Sep 22, 2003 7:28 pm
Posts: 228
Location: United Kingdom
I am looking at making a convential slot in style rudder, but not sure what is common practice with the pin, from distant memory I think I have used 15mm solid s/s. That seems really heavy. What do other people use?

_________________
Alistair


Top
 Profile  
 
 Post subject: Re: Rudder pins
PostPosted: Thu Jul 23, 2009 8:26 am 
Offline

Joined: Thu Jul 17, 2003 10:08 am
Posts: 149
Location: United Kingdom
Well I bought a bit of carbon tube (from Carbonology?) of about 12mm OD and wall thickness 3-4mm....

I then took a mixture of uni-carbon and kevlar tows and wetted out twice the length of tube.

I doubled it back in a loop over a length of wire that I then used to pull the whole messy double length of carbon/kevlar/epoxy back up through the tube.

I have to say, it doesn't feel as 'stiff' as the s-steel rod that was in my old rudder, but works fine.

Had 2 years of sailing in mixed conditions without breaking.....but I do check it every now and again.

Even the stainless one broke in the end.

The next one, I will do the same but try and find a thicker bit of tube to start with - 15 or 18mm OD

Good luck

cheers

eib

_________________
Ed Bremner
GBR314 - Silver Surfer
GBR242 - For sale
Lowly forum moderator
Classic & Vintage Racing Dinghy Association
http://www.cvrda.org


Top
 Profile  
 
 Post subject: Re: Rudder pins
PostPosted: Thu Jul 23, 2009 12:21 pm 
Offline

Joined: Mon Sep 22, 2003 7:28 pm
Posts: 228
Location: United Kingdom
Thanks Ed
I tried a carbon one once but it wore very quickly and began to wobble, did you protect the carbon in some way?

_________________
Alistair


Top
 Profile  
 
 Post subject: Re: Rudder pins
PostPosted: Thu Jul 23, 2009 12:56 pm 
Offline

Joined: Thu Jul 17, 2003 10:08 am
Posts: 149
Location: United Kingdom
Wear is certainly an issue....

and I hope some others with more understanding on carbon will be able to explain further....

but carbon bits that I have built which are in continual friction points such as the carriage rails have shown dramatic wear. I even have a black dribble off end of carriage runners after a sail.

But I don't seem to have much problem with the rudder-shaft. I suspect two reasons for this:

First, I didn't make the tube. I suspect it was made mechanically under pressure/heat and has a much harder surface than any I could make???

Second, it 'may' also be due to having the shaft run in an epoxy/graphite bearing through the cassette. This was originally 'tightish' but is now after 2 years still quite usable, but certainly looser than it was, but no wobble.

The 'hardness' of epoxy-carbon structures does rather interest me. I have rather a habit of hanging around any dinghies made with carbon bits and flicking them with my nail. There appears to be a audible difference in 'tone' between professionally built carbon and amateur (mine is very amateur) carbon.

Flick the rudder-stock of a new 14 and the sound is almost 'ceramic' like clicking a coffee-mug, but by comparison my carbon stuff sounds very 'dead' and wooden.

I have talked to Wizz at Matrix Mouldings about this....and he puts it down to the better quality resins used professionally, higher carbon-content etc in fact all the things that make the pro stuff 'pro' and mine pretty amateur!

cheers

eib

_________________
Ed Bremner
GBR314 - Silver Surfer
GBR242 - For sale
Lowly forum moderator
Classic & Vintage Racing Dinghy Association
http://www.cvrda.org


Top
 Profile  
 
 Post subject: Re: Rudder pins
PostPosted: Fri Jul 24, 2009 9:29 am 
Offline

Joined: Fri Dec 22, 2006 10:32 pm
Posts: 523
Location: United Kingdom
Ed,

Its more likely to be to the use of high pressure and heat in professional systems which drives all the air out and hence ensures a solid lamination.

Have suggested to Alistair using a 10mm polyester glass rod which is very strong and also very hardwearing. Anyone ever used these?

_________________
Steve Clarke (UK)
GBR338 "Money4Nuffin


Top
 Profile E-mail  
 
 Post subject: Re: Rudder pins
PostPosted: Fri Jul 24, 2009 12:31 pm 
Offline

Joined: Thu Jul 17, 2003 10:08 am
Posts: 149
Location: United Kingdom
yes, indeed pressure/heat is what I meant to say really... I do vacuum where I can, but it's hard on fiddly bits.

10mm glass rod is interesting.....I considered it, but discounted it....would love to know if anyone has practical experience of using it.

Where I notice the carbon shaft being less than completely stiff is in the torsional or twisting action.

It seems very strong to sideways forces.....but if I grip the rudder under my arm and twist the tiller, there is more movement than I would expect. Certainly not enough to notice when sailing, but less than with the 12mm s/steel shaft in old rudder.

Of course much of my construction was uni-carbon lying up and down the centre of shaft, so not really in right place to stop the twist.

cheers

eib

_________________
Ed Bremner
GBR314 - Silver Surfer
GBR242 - For sale
Lowly forum moderator
Classic & Vintage Racing Dinghy Association
http://www.cvrda.org


Top
 Profile  
 
 Post subject: Re: Rudder pins
PostPosted: Tue Jul 28, 2009 2:43 pm 
Offline

Joined: Fri Aug 01, 2003 2:26 pm
Posts: 164
I would stay away from pultruded glass rod and stay with 12mm stainless.
If you have a larger rigging shop near you, you can often get cut offs of Nitronic 50, which is the alloy used on solid rod rigging. You will need cobalt drill bits or a friend with a machine shop, to do the drilling for you, but you will not break the shaft.
Garden variety marine stainless ( 302 or 304) has worked for years, but I have had problems recently breaking shafts. On the other hand the current rash of rudder blades are pretty deep and that may be enough to take the 302 over the edge.
SHC

_________________
Beatings will continue until morale improves


Top
 Profile  
 
 Post subject: Re: Rudder pins
PostPosted: Sun Jul 04, 2010 2:59 pm 
Offline

Joined: Tue Feb 26, 2008 12:58 pm
Posts: 16
Location: Hampshire
Hello, I'm looking for some advice regarding how the rudder pins are actually fixed into the rudder. Was sailing on Saturday in 20 knots and got into a big tank slapper, lots of zig zagging to correct and finally a swim. Once back ashore I noticed there is some play in the rudder pin, not much - about 0.5 - 1 degrees when twisting the shaft in the rudder blade. It seems solid laterally. I'm guessing this play was amplifying my steering corrections. Is there a way of tightening the pin or removing it, or are they epoxied in at construction, in which case is it fixable? There is a stainless steel tube for the shaft with a solid metal shaft inside of that - Do they come apart somehow?

Any advice much appreciated!

James Close
IC GBR 262
"Longbow"


Top
 Profile E-mail  
 
 Post subject: Re: Rudder pins
PostPosted: Sun Jul 04, 2010 8:53 pm 
Offline

Joined: Thu Jul 17, 2003 10:08 am
Posts: 149
Location: United Kingdom
There are as many different rudder blades as there are canoes....

but on the whole, I don't like the sound of that much!

Is it a foam or wood rudder?

I guess most probably wood. I think I would favour digging in a bit and finding out what is happening and fixing it, rather than waiting for it to go and the interesting sail back. If it does go, do remember to pick it up! Happened to me once and I was so flummoxed by trying to work out what had happened, that by the time I had got my act together the foil had disappeared/floated off.

cheers

eib

_________________
Ed Bremner
GBR314 - Silver Surfer
GBR242 - For sale
Lowly forum moderator
Classic & Vintage Racing Dinghy Association
http://www.cvrda.org


Top
 Profile  
 
 Post subject: Re: Rudder pins
PostPosted: Mon Jul 05, 2010 9:15 am 
Offline

Joined: Tue Feb 26, 2008 12:58 pm
Posts: 16
Location: Hampshire
Thanks Eib, trying to get back to the club through moorings in gusty wind without a rudder doesn't bear thinking about! So won't use it til it's stopped wobbling.

It is a cassette type (through deck), wooden rudder from a Razorback (I believe) Nethercott. Would like to know what is likely to be in there before I start digging at it and potentially destroying it! If the shaft flares out at some point in the rudder to lock it in place I guess it cannot come out and I need a new rudder?

James
GBR 262 "Longbow"


Top
 Profile E-mail  
 
 Post subject: Re: Rudder pins
PostPosted: Mon Jul 05, 2010 10:53 am 
Offline

Joined: Fri Dec 22, 2006 10:32 pm
Posts: 523
Location: United Kingdom
James,

I've done a lot of work on rudders over the last few months and belive you me it is critical area as the loads on the rudder at full tilt can exceed 100kg. This becomes a major issues if the rudder presents itself at more that a few degrees to the flow - a good reason for having an elastic restrainer stopping the rudder turning more than about 20 degrees.

The rudder pins are usually stainless traditionally giving good wear characteristics but should be a minimum of 12mm (1/2") and 316 grade. The usually go inside the rudder core and penetrate about 200-250mm to spread the load. To prevent the the shaft twisting in the rudder casing a pin is usually inserted horizontally along the rudder at one or more points. The standard from Razorback is a stainless tube with a carbon rod down the middle and is much thicker - I'm sure Rob will fill in the detail.

If your shaft is loose you must fix it or it will fail. Only way to do this properly is to cut through one side with a router and expose the shaft all the way down. The wooden core may have rotted so clean it out and dry it out well. Back fill with expoxy mixed with microfibres and also line the shaft with carbon and stuff a load of carbon down the sides of the rod in with the goo. I have found that wrapping the stainless rod tight with 80grm/m2 S-glass and epoxy first helps the rod bind well inside the rudder and stops it twisting. Once Epoxy has gone off swooth it all down and then apply a couple of layers carbon on top faired in with the top surface.

I am actually of the firm opinion that stainless is a pain in the arse as it bends at some point. I am working on a new mould for a rudder using an 18mm carbon shaft with a piece of good old dowel stuffed down the middle at the point where the shaft leaves the rudder and enters the rudder box. Much easier to make and won't bend - if it snaps it is a lot easier to fix.

_________________
Steve Clarke (UK)
GBR338 "Money4Nuffin


Top
 Profile E-mail  
 
 Post subject: Re: Rudder pins
PostPosted: Tue Jul 06, 2010 7:43 pm 
Offline

Joined: Fri Jul 18, 2003 7:53 am
Posts: 142
Location: Emsworth Hants United Kingdom
As the years have gone by, I have seen just about every type of rudder shaft used to varying degrees of success or failure. Strenght is not the only factor in chosing the correct shaft. It also needs to be as light as is practiucal & have good wear resistance. 1/2" stainless bars were the main choice back in the 70's/80's & even up to today but the problemb with thin stainless bar is that it will become brittle if it bends & is straightened & stainless is quite a brittle metal that will fractue which was very common with many a rudder blade using this type of shaft. Thicker bar will be much too heavy so I started using 5/8" 10swg thick walled ss tubing which proved much more durable than the 1/2" solid bar & took impact loads much better than bar but again was a bit heavy. Carbon is nice & light, very stiff but useless on wear resistance & high impact so all the current foils I've supplied over the past 10+ years are made using a combination of both, a 19mm dia thin wall stainless tube (22swg) with a uni di carbon bar inside it to give it the stiffness. These are light & very strong that also give good wear resistance. To make the uni di bar, I start with a 6mm pultrusion glass bar as the core, this glass bar is sometimes used for cat battens. I then wrap uni di carbon around the bar with epoxy to just over the approx dia & peel ply it very tightly so it compresses all the excess epoxy out. I then heat this up to post cure it. When I remove the peel ply after its curred I linish it to size on a linisher belt sander so it just fits inside the tube. I then epoxy it in place making a light strong shaft that should last. Carbon bar can be bought in various sizes from various manufacturers as an alternative (not sure who in the UK as I've never bought any but I've heard their out there). I also manufacture alloy tiller heads that can be clamped very tightly to the shaft, again these are typically one off parts as are many componets for a Canoe.


Top
 Profile  
 
 Post subject: Re: Rudder pins
PostPosted: Wed Jul 07, 2010 5:19 pm 
Offline

Joined: Fri Aug 01, 2003 2:26 pm
Posts: 164
It is hard to discuss rudder shafts or pins without thinking about the shape of the rudder you hope to build.
My current thinking is much influenced by others in the sailing world who have gone for deep high aspect rudders. If these are to be anything but very thick sections, you need to make the shaft as thin as you can and still have it be strong enough. This makes steel a good choice, as it can be small and still very strong.
The weight issue is more of a problem with ICs than with Nethercotts or ACs. I went back to stainless steel and away from carbon shafts when the all in weights were introduced. There was no sense making very light rudders only to add more lead to the boat. And I was able to design more efficient rudders to boot. I still play the skinny rudder game and take the weight penalty top do so.
SHC

_________________
Beatings will continue until morale improves


Top
 Profile  
 
 Post subject: Re: Rudder pins
PostPosted: Thu Jul 08, 2010 2:30 pm 
Offline

Joined: Fri Dec 22, 2006 10:32 pm
Posts: 523
Location: United Kingdom
Steve.

You are absolutely right about the profile. The old triangular shape can have a big shaft being much thicker and also generally are much shorter.

I have been working with Alistair with his very long narrow long profile (approx 120mm) which feels great and I' sure is the way to go for low drag. I have gradually reduced the length to now about 400mm below the skin as leverage on the pivot will increase by the square of the length (I think). I tried initially a 10mm pivot with a 500mm length blade and it lasted about 5 minutes bending by about 30 degrees.

With the narrow profile I can only get a 12.5mm stainless pin inside the skins and I have calculated it is just on the edge based on a 80-100kg load applied across the blade which you can easily get if a stall occurs at 15knots. Went out last week in a very nasty gust F2-6 and I think it bent a little as the rudder will stall if you are too abrupt with steering particulalry on a fast reach and if the boat heels. Have you arrived at a minimum working area required for new rules boats? I guess we can scale this up for a heavier Nethercott?

The major advantage of carbon is of course it will take more load and won't bend (just shatter) but Rob's point about wear is the problem. I have considered getting an axially and biaxially wound carbon shaft to stop twist with a bearing surface of glass or kevlar on the top. I tried Rob's approach with a 12mm stainless tube with a 9mm carbon rod and this wasn't stiff enough and bent albeit only a little. I suppose another approach could be a 12mm carbon shaft into the rudder with a thicker stainless tube over the top as it leaves the rudder to go through the rudder box in the hull. This would allow some flexibility at the joint between rudder and box which wouldn't then not permenantly deform if the stainless was not embedded in the rudder.

_________________
Steve Clarke (UK)
GBR338 "Money4Nuffin


Top
 Profile E-mail  
 
 Post subject: Re: Rudder pins
PostPosted: Tue Jul 20, 2010 12:09 pm 
Offline

Joined: Tue Feb 26, 2008 12:58 pm
Posts: 16
Location: Hampshire
Thanks for all the helpful advice and discussions, all very informative and makes for interesting reading. I've brought a new rudder from Rob, so can get back on on the water ASAP. Will get the old one fixed as a spare.

-
James.


Top
 Profile E-mail  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 15 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group