LM27 rudder blade attachment

[tonyp]

The attachment between the rudder blade and stock on the 1979 LM27 we are buying has a lot of play in it.  I have seen comment by Michael Legg about the need to check frequently the taper that fixes the blade to the stock.  On Sundance, the fixing seems to be an M10 stainless bolt, (though we haven't removed it yet to check) and obviously, if it should be a taper and not a bolt this may explain a lot.  However, if on examination it turns out to be a bolt, my fear then is that it may have worn the hole in the stock meaning a taper would no longer fit snuggly.  
I haven't looked at any other 27s to know if our attachment is standard, but on Sundance two pieces of flat steel bar about 150mm long are clamped along the top of the blade with two bolts, the centre of the bars being bent loosely around the stock. The 8 mm bolt / taper then runs through the middle of the two bars and through the stock. This system looks surprisingly crude, given the superb "engineering" of the rest of the boat.  It looks weak and leaves no fall-back in the event of failure of the single fixing taper/bolt.  
Am I being too windy?   Any comments/ advice would be most much appreciated and if anyone else has modified a 27's rudder attachment (or felt the need to!) I'd be very interested to know how.

[Charles]

Are you sure the play is between rudder blade and stock Tony? On my LM 27 that is indeed tight, but there is an appreciable amount of play in the linkage between it and the wheel. Wait for the expert - Jandane - to reply.

Charles

[tonyp]

Hello Charles,
Definitely play between the stock and the blade attachment.  It's very easy to see (and feel).  There seems to be very little play between the wheel and stock, which I was surprised and pleased to find.  From what you say though, I wonder whether the bars that clamp on to our blade are none original and have been made too loose on the stock. I must say they look a bit crude, which is not at all an LM thing. I will get a photo when I can get down to the boat. The only pic I have is in the surveyor's report and I don't think it will scan well.

Tony

[tonyp]

Herewith Sundance's rudder blade/stock attachment.  Is it the standard fitting?
Tony

[oceandancer]

Hi Tonyp,
Yup, looks very familiar to me. You should remove the pin to see exactly what you've got. I hope someone hasn't drilled out the taper ! If so you will have to use some sort of shim (thin metal sheet) to try to get a good fit, however this MUST be 316 material do not use ordinary steel shim or bronze shim.

You've probably got a taper pin that's very worn or corroded, in which case you will get a lot of play, however,I have not sourced these pins from anywhere, does anybody have any info?

Instead I make my own from 316 10mm rod.
I don't have a lathe, you don't need one, just a column drill. No special skills are needed the job takes about 30-40min. Here's how to proceed:

I am assuming that you do have a taper pin that is worn but will be good enough for a pattern.
Tools: Column Drill,engineers vice, hacksaw, Sharp files, Micrometer or outside vernier caliper, 8mm metric die, a straight edge, emery cloth or 80 grit wet and dry, oil.

1. cut the bar about 30mm overlength to allow for the drill to grip.
2. Lay the drill on it's side to make an inpromptu lathe and insert the rod into the chuck, tightening as well as you can. The end will be unsupported but with 10mm rod of this length this will be OK.
3. With a good (new?) sharp file, start the drill and mark off what will be the threaded portion plus 5-8mm and cut a groove with the hacksaw as a starting guide. This threaded portion needs to be reduced to the outside diameter of the threaded part of the pattern. Start filing from this end up to the mark you have cut. Try to get it parallel, this is a critical bit as the outcome will determine the quality of the thread you are to cut. Move the file forward and back to use all the teeth.
4. When the thread length has been reduced to the correct diameter, file a taper on the additional 5mm length so that the tapered end is about 1mm below the bottom of the thread. This is to allow the die to start.
5. When the thread portioned has been reduced you can begin tapering.The length of the tapered portion of the pattern will give you a guide.
measure against the pattern and cut a small groove with the hacksaw to mark this point on the bar.
Begin filing the taper, avoid slipping back onto the thread portion. Measure the taper on the pattern at several points and reduce the bar to match, obviously you are attempting to obtain a straight slope up to the point you have marked so check with the straight edge occasionally. This bit seems a bit daunting but it's really quite easy, you can do it easily by eye.
6. When you are satisfied that you have copied the taper accurately clean up the bar with a smooth file, emery cloth or wet and dry. A smooth finish is vital. Even 316 stainless steel will rust if the surface is rough in the presence of oxygen and seawater. This is called crevice corrosion.
7. Remove the bar from the drill and secure the parallel uncut portion vertically in the vice. Tighten well.
8. Begin cutting the thread. Use oil to lubricate the cutting. Start slowly, bear down horizontally on the job and turn slowly to get the die to bite. If it refuses to start you may have to make the lead in taper more pronounced but do not make it too long.
After the die begins to cut observe the following rule: one half turn forward, one quarter turn back to clear the cutting swarf. Failure to do this will spoil the thread. This is important. Use plenty of oil. Cut the thread until you get to the beginning of the taper. Then run the die back up and down several times to clear the thread of any remaining swarf. Try the nut on the thread to make sure you have a good fit, not too tight or too loose.
9. Screw a nut onto the thread to expose the starting taper, secure the rod horizontally in the vice and cut off the taper close against the nut. Screw the nut further down the thread and file the end so that it is smooth. Run the nut off and on the thread several times to ensure a good start.
10. Return the bar to the column drill and use the hacksaw to cut(part)the taper pin.

Good Luck!

Mick Legg

[tonyp]

Thanks very much for this very comprehensive reply, Mick.  I am relieved to know that the attachment is the usual one.  We'll get the existing bolt/taper out and see what's there.  If the hole hasn't been damaged, producing a new taper shouldn't be a problem. If the hole in the stock has been damaged, it will depend on how bad it is, as to what we do next.  If the stock is very bad there may be more postings to follow....!

Tony 

[jandane]

Hi Tony.
You can get the original pins at Madsnedø Marinecenter (mmc.dk) in Denmark. They speak and write English.
Also check the play in the attachments under the reardeck.
I am at present on winter holiday away from Denmark, so I am unable to check my own rudder to see how it looks. However,mI do have a photo of a rudder (with extended top) on which you can see the attachments, and it looks very much like yours
 
Jan

[tonyp]

Thanks very much for your response, Jan. I'm sorry I didn't reply sooner, but I've been away too.
I haven't been to the boat to see the state of our taper, but it may be of interest that there's a photo on the Yachtsnet website which shows a 27 with a pretty conventional rudder flange arrangement.  I wonder if this was someone's modification? I shall be interested in any other attachments in case we are unable to use the original taper-pin one, which may be the case if the stock has been damaged by the hole becoming too enlarged.  

Tony 

[jandane]

Tony,
here is a picture of my rudder. Still not cleaned, but it is easy to see the bolts. My blade is not original but made of 5 mm stainless steal. Why, I do not know

Attachments:

[tonyp]

It looks exactly the same as mine, Jan.  If yours has worked for as long, and over as many miles as yours, I guess I have nothing to worry about!
Very many thanks.
Tony

[oceandancer]

Hi Jan,

I would like to order some taper pins from Madsnedø Marinecenter but my Danish is a little rusty at this moment! What do I ask for please, a catalogue number and price would be helpful.

Regards

Mick Legg

[tonyp]

Mick, I've just received a rudder pin from Denmark.  The part number is 420726.  If you email them in English they will very efficiently deal with it. The downside is the cost - not to Masedno, but the bank charges.  The pin costs £20 but the bank charges are £25 to Barclays and £12 to Danskebank. - £57 for a 45mm long piece of machines stainless makes you weep!  Having now got a pin I'm looking at UK suppliers.  One pin would be probably as expensive as one Danish one, but a batch may be cheaper.

Think my rudder stock may have been damaged by the bolt that was used.  I haven't tried the taper yet, but it measures 9mm at its widest and the hole in my stock is 10mm at its widest.  
Tony

[tonyp]

Mick,
The total cost from Masnedo was 189DKK, which includes postage and VAT, but will be subject to the exchange rate and there will be bank charges on top. Masnedo will give you the bank details for tranfering the money.
Tony

[oceandancer]

Tony,

Thanks for that. I think I'll stick to making my own - or I might set up a UK based cottage industry! it sounds like it might pay!
I'll be interested to know how you get on.

Regards

Mick

[tonyp]

Mick,
I don't know how much use this is, but I've shown here the dimensions of my new LM 27 taper.  The measurements are as near as I can make them with my, not terribly accurate, vernier callipers.  I had the measurements repeated by a friend who restores classic motorbikes and they came out, not surprisingly,  in imperial, and seem to make a taper of even odder dimensions!  It certainly doesn't look as if the LM taper is to an international standard.  The DIN standard is usually 1:50, which this definitely is not.
Of course, by now due to age, many rudder tapers will be worn and the original sizes will not necessarily apply, but the "shape" should still apply. If I find someone to make some up I will get them made to the same "shape" but make them a couple of mm longer so they can be drawn in tightly to worn taper holes.

Tony