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Rudder Machine bolts / Screws

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Alan Dixon View Drop Down
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Post Options Post Options   Quote Alan Dixon Quote  Post ReplyReply Direct Link To This Post Topic: Rudder Machine bolts / Screws
    Posted: 19 Apr 2012 at 12:43pm
I am lifting Charlotte shortly for Coppercoat. I plan to remove the rudder to strip behind and replace the cutlass. When I last had the rudder off (2005)   the machine screws were eaten away a little, I don't think there condition will have improved. I tried to replace them at the time but could not find anything to fit (Metric). I have subsequently discovered that they are 5/16" Whitworth. I seem to be able to source A2 Stainless but not A 4.
Is A2 Stainless up for the job considering they are encased in filler and immersed ?
Would I be better off filling the existing holes with epoxy drilling and re tapping to Metric
Any thoughts / experences appreciated
Alan Dixon "Charlotte"
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moongirl View Drop Down
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Post Options Post Options   Quote moongirl Quote  Post ReplyReply Direct Link To This Post Posted: 19 Apr 2012 at 1:50pm
Alan
They are a long way from you but my local Tool Shop has a huge range of s/s bolts etc & seem to be able to find whatever I have needed in the past - at a fraction of marina prices too!
Their Tel No is 023 92818334 CP Fastenings
Regards 
COLIN
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moongirl View Drop Down
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Post Options Post Options   Quote moongirl Quote  Post ReplyReply Direct Link To This Post Posted: 21 Apr 2012 at 8:11am
Alan
just another thought. If you go down the route of replacing the machine screws with metric you could use s/s helicoil inserts epoxied into the skeg - in my view a more secure option than tapping epoxy.
The only problem as I see it would be one of alignment and some ingenuity would be needed perhaps using the heel plate as a jig.
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COLIN
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Alastair Pugh View Drop Down
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Post Options Post Options   Quote Alastair Pugh Quote  Post ReplyReply Direct Link To This Post Posted: 21 Apr 2012 at 10:34am
It is a while since I did this but my memory was 3/8" Whit and M10 were the sizes - if I'm wrong, I beg forgiveness.  Those 2 threads are similar ~9.5mm v 10mm dia and 16tpi v 1.5mm (~16.7tpi).  I retapped the fibreglass M10 and then loaded the holes and bolt threads with epoxy filler and used cap headed screws giving a final torque when the epoxy residue had almost gone fully off.  That was 5 years ago and the rudder hasn't fallen off, though the skeg bit did last year after it hit something (heard and felt the thump, saw nothing ??).
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St Paddy View Drop Down
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Post Options Post Options   Quote St Paddy Quote  Post ReplyReply Direct Link To This Post Posted: 23 Apr 2012 at 3:05pm
Hi
 
On st Paddy I bonded and bolted on a plate drill and tapped with a key slot and the heel plate is bolted to that. I can now drop my rudder quckly and fe fit just as fast.
 
Not a cheap option but good. If you want a drawing I have one
 
 
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Alan Dixon View Drop Down
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Post Options Post Options   Quote Alan Dixon Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2012 at 3:32pm
Thanks for the ideas. I have decided to epoxy fill drill and tap metric, Will let you know how that worked 
Alan
Alan Dixon "Charlotte"
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Post Options Post Options   Quote St Paddy Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2012 at 8:29am

You will have a job to keep the epoxy in, the hole will be wet and drity. If your heel plate is standard it will be held by 5/16 whit. counter sunk screws.

I would retap the holes if it were mine or a customers boat.
 
Your next size up from that is M10 with a tapping drill of 8.5mm (5/16 is 8mm) so you can clean out your worn hold and re-tap. You could go 3/8th UNC
 
you need the heel plate holes opened out

If you need a tap and drill I can loan you some. I would use 316 socket Cap heads. GTC fixings will post them to you google them, no mim order. The chandlery will only have 405 stainless, that will only last a few years in the heel plate. when done post the tools back.

Use acetone to clean and sikaflex when you assemble, the side load on the heel plate skids the fitting side to side and that is why the screws and threads fail. If that happens you have a blade rudder with a 1 1/4 shaft.

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Alan Dixon View Drop Down
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Post Options Post Options   Quote Alan Dixon Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2012 at 9:41am
Thanks for the great advice, I had not considered enlarging but think it is the better option, and I will go down that route. Thanks for your kind offer of Taps and drills, I have the necessary gear.
Alan

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Post Options Post Options   Quote St Paddy Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2012 at 10:58am
Pleased to be of help. 
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Alan Dixon View Drop Down
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Post Options Post Options   Quote Alan Dixon Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2012 at 10:24am

A quick report back on what I found and did on this job.

On removing the skeg cap I found the heel plate slack, The heads of the countersunk 5/16” BSW bolts has all but disappeared and it was the tape and epoxy I have fastened the cap on with, that was supporting the heel plate against sideways movement. The heel plate on Charlotte is drilled to 10mm and relies on its location on the countersunk heads of the bolts. Not in my view the best engineering solution.

I removed everything and cleaned everything. Drilled and tapped the skeg to 10mm, this worked really well cutting good clean threads into good glass. I refastened the heel plate on a bed of Sitaflex and 4 x M10 x 40mm socket button set screws. Replacing the cap in the normal way and reinforcing the job with epoxy tape.

Hope this helps members.

Alan

 

 

Alan Dixon "Charlotte"
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