30boat
N/A
If it were truly closed cell,nothing but according to what I've read recently even supposedly closed cell foam eventually absorbs water.
How do I fix a cracked rudder?
- Thread starter MacD68
- Start date
contessaman
Well-Known Member
before you try a repair can I commend this book to you:
http://www.amazon.co.uk/Fibreglass-Repair-Manual-Allan-Vaitses/dp/0229118550
everyone with a grp boat should have it even if you dont do the repair yourself you can make sure its done properly. If you are doing it yourself this book will explain to you exactly how to go about it and make a professional job of it. It really is worth every penny. saved my bacon when I had keel movement problems.
http://www.amazon.co.uk/Fibreglass-Repair-Manual-Allan-Vaitses/dp/0229118550
everyone with a grp boat should have it even if you dont do the repair yourself you can make sure its done properly. If you are doing it yourself this book will explain to you exactly how to go about it and make a professional job of it. It really is worth every penny. saved my bacon when I had keel movement problems.
nigelmercier
RIP
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Or perhaps this one which was last published twenty years later, and this century as well (2010)
Fibreglass Boats: Construction, Gel Coat, Stressing, Blistering, Repair, Maintenance
http://www.amazon.co.uk/exec/obidos/ASIN/140812274X/dolcetto-21
"This masterly work will continue to be an invaluable source of reference for anyone wanting practical advice on working with GRP, in order to make repairs and improvements correctly and thus extend the life of their boat..."
Last edited:
contessaman
Well-Known Member
oi Nige! that book is more recent than my boat........ 
nigelmercier
RIP
- Joined
- 20 Jun 2007
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- 16,234
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- Live in Kent, boat in Canary Islands
oi Nige! that book is more recent than my boat........
Only the latest edition I imagine.
MacD68
Member
30Boat,
Can you let me know which issue of PBO has the Andrew Simpson article in it? I have quite a few old issues lying somewhere around the house.
Nigelmercier,
Thanks for the book recommendation. It's probably a wise investment before I start cutting up what I already have.
Thanks to all for the useful input.
MacD
ninky
Well-Known Member
Lots of youtube vids showing how to do fibreglass layup / repairs. It's not hard to do a very serviceable repair, although getting a really good cosmetic finish does require some skill.
30boat
N/A
I wish I could remember.All I know is that it is probably dated before 2003 .There were a series of articles on the building of his boat Shindig.I did a search but it didn't come up.I know he launched around 2002/03 because I met him in the Algarve in 2004.
Tranona
Well-Known Member
Andrew surveyed my boat and advised on the new rudder I built over 20 years ago. Similar basic construction to Shindig except that his is semi spade. Still going strong. Construction method in my earlier post and ideal for the OP boat.
Foam cored GRP OK for production rudder but OTT for modest one off DIY
Foam cored GRP OK for production rudder but OTT for modest one off DIY
30boat
N/A
This article shows how to build a rudder.I didn't read the whole article but I suspect this is an Andrew Simpson design and the rudder is shown being built very much like the one in Simpson's article.http://www.sailboat-cruising.com/sailboat-rudder.html
Edit.This is an Andrew Simpson design,earlier than Shindig his own yacht.
oldsaltoz
Well-Known Member
Just a few comments to ponder.
Just can't help myself.
Avoid a 'solid' rudder it will have all it's weight in the bearing and may drag her stern down and badly effect her handling. not to mention the fact that it will be harder to move and reduce the life of any sliding bearing.
The ideal rudder would have neutral buoyancy, to this with ply and epoxy would mean an over sized rudder or a very long and deep one with associated problems.
Most boat manufacturers do not make their own rudders, this is put out to contract so don't be surprised if some makes have a bad reputation when it comes to rudders.
Adding a bit of balance to rudder is not rocket science either, you need 15% of the total area ahead of the shaft.
A stainless steel shaft is a must and it should have a bearing underwater and a top capture that prevents the stock from falling out and from lifting.
The tangs weled to the shaft MUST be properly pickled after cooling to prevent any corrosion, this is critical and the cause of many failures.
Modern closed cell foam is reliable and will not take up any moisture, even if the rudder outer skin is breached.
Foam core material is very to to shape to a fine profile and any over sanding can be easily rectified using an epoxy resin and glass spheres.
I have been adding 2 or 3 '0' rings coated in a light grease at the top of the rudder to prevent water ingress for many years now and it works very well.
Also most important and a common mistake with foam cored rudder (even some of the professional built ones) is no support between the tangs and the outer skin. All that is required is a series of 25 mm holes between the tangs and the skin filled with a mix of Micro-fibers and epoxy resin, this ensures any pressure on the tang is transferred to the outer skin, that avoiding any crushing of the foam core.
There, I feel much better now, thanks for taking the time to read this, I hope it helps.
Good luck and fair winds to you all.
Just can't help myself.
Avoid a 'solid' rudder it will have all it's weight in the bearing and may drag her stern down and badly effect her handling. not to mention the fact that it will be harder to move and reduce the life of any sliding bearing.
The ideal rudder would have neutral buoyancy, to this with ply and epoxy would mean an over sized rudder or a very long and deep one with associated problems.
Most boat manufacturers do not make their own rudders, this is put out to contract so don't be surprised if some makes have a bad reputation when it comes to rudders.
Adding a bit of balance to rudder is not rocket science either, you need 15% of the total area ahead of the shaft.
A stainless steel shaft is a must and it should have a bearing underwater and a top capture that prevents the stock from falling out and from lifting.
The tangs weled to the shaft MUST be properly pickled after cooling to prevent any corrosion, this is critical and the cause of many failures.
Modern closed cell foam is reliable and will not take up any moisture, even if the rudder outer skin is breached.
Foam core material is very to to shape to a fine profile and any over sanding can be easily rectified using an epoxy resin and glass spheres.
I have been adding 2 or 3 '0' rings coated in a light grease at the top of the rudder to prevent water ingress for many years now and it works very well.
Also most important and a common mistake with foam cored rudder (even some of the professional built ones) is no support between the tangs and the outer skin. All that is required is a series of 25 mm holes between the tangs and the skin filled with a mix of Micro-fibers and epoxy resin, this ensures any pressure on the tang is transferred to the outer skin, that avoiding any crushing of the foam core.
There, I feel much better now, thanks for taking the time to read this, I hope it helps.
Good luck and fair winds to you all.
30boat
N/A
It's a valid opinion and should be considered.Just can't help myself.
Avoid a 'solid' rudder it will have all it's weight in the bearing and may drag her stern down and badly effect her handling. not to mention the fact that it will be harder to move and reduce the life of any sliding bearing.
The ideal rudder would have neutral buoyancy, to this with ply and epoxy would mean an over sized rudder or a very long and deep one with associated problems.
Most boat manufacturers do not make their own rudders, this is put out to contract so don't be surprised if some makes have a bad reputation when it comes to rudders.
Adding a bit of balance to rudder is not rocket science either, you need 15% of the total area ahead of the shaft.
A stainless steel shaft is a must and it should have a bearing underwater and a top capture that prevents the stock from falling out and from lifting.
The tangs weled to the shaft MUST be properly pickled after cooling to prevent any corrosion, this is critical and the cause of many failures.
Modern closed cell foam is reliable and will not take up any moisture, even if the rudder outer skin is breached.
Foam core material is very to to shape to a fine profile and any over sanding can be easily rectified using an epoxy resin and glass spheres.
I have been adding 2 or 3 '0' rings coated in a light grease at the top of the rudder to prevent water ingress for many years now and it works very well.
Also most important and a common mistake with foam cored rudder (even some of the professional built ones) is no support between the tangs and the outer skin. All that is required is a series of 25 mm holes between the tangs and the skin filled with a mix of Micro-fibers and epoxy resin, this ensures any pressure on the tang is transferred to the outer skin, that avoiding any crushing of the foam core.
There, I feel much better now, thanks for taking the time to read this, I hope it helps.
Good luck and fair winds to you all.
rob2
Well-Known Member
In all innocence I am wondering...
Surely a foam cored rudder has positive bouyancy as will a wooden cored one (but less so)? I've always noticed that my rudder sits on the bottom support when ashore but rides up to the top bearing once afloat.
A solid GRP rudder would certainly add weight as it has negative buoyancy and would be difficult to construct as such a thickness of resin would generate tremendous exothermic heat during curing.
Rob.
Surely a foam cored rudder has positive bouyancy as will a wooden cored one (but less so)? I've always noticed that my rudder sits on the bottom support when ashore but rides up to the top bearing once afloat.
A solid GRP rudder would certainly add weight as it has negative buoyancy and would be difficult to construct as such a thickness of resin would generate tremendous exothermic heat during curing.
Rob.
30boat
N/A
You're correct.I don't think anybody makes solid GRP rudders these days.
Tranona
Well-Known Member
Primarily because most rudders now are spade foils and weight becomes a serious issue - not just to reduce overall weight at the aft end of the boat, but to reduce the load on the unsupported stock. Many of the old seemingly solid GRP rudders were two shells bonded together and the void filled with all sorts of rubbish. weight was less of an issue as the rudder was usually well supported by bearings top and bottom - or at least partway down by a skeg. Bottom parts were often sacrificial with no supporting framework inside.
For the OP weight and strength are not a big issue as it is a small rudder well supported by a skeg so a Ply blade on a stainless web framework would be more than adequate and simple (relatively) to make.
MacD68
Member
Info update for anybody interested
Hi,
Given all the positive input received to my original query, I thought it worthwhile to give a short update.
I finally got round to removing the rudder yesterday, and split it open today. The construction appears to have been a galvanised steel shaft with two tangs. Two half shells were used, largely foam filled, except they were padded around the tangs with what appears to be the same as body filler for cars. The same material was used to bond the two shells together.
Though damp internally the rudder was still very strong and took a lot of force to open up. The biggest issue is actually the condition of the shaft. Though some corrosion was apparent when it was fitted to the boat, when I dropped the rudder there was extensive corrosion in the area where the rudder shaft would have been at the lower end of the rudder tube. I guess this is the area which would have been at the water/air interface, so it's not unexpected that the corrosion is worst here, but it was out of sight and would never have been noticed if the rudder hadn't been dropped.
Based on the feedback given, my plan is to have a new shaft made in 316 stainless, use marine ply to make the blade, and then sheath it in glassfibre. It's going to be a learning curve, but should be do-able.
MacD
Hi,
Given all the positive input received to my original query, I thought it worthwhile to give a short update.
I finally got round to removing the rudder yesterday, and split it open today. The construction appears to have been a galvanised steel shaft with two tangs. Two half shells were used, largely foam filled, except they were padded around the tangs with what appears to be the same as body filler for cars. The same material was used to bond the two shells together.
Though damp internally the rudder was still very strong and took a lot of force to open up. The biggest issue is actually the condition of the shaft. Though some corrosion was apparent when it was fitted to the boat, when I dropped the rudder there was extensive corrosion in the area where the rudder shaft would have been at the lower end of the rudder tube. I guess this is the area which would have been at the water/air interface, so it's not unexpected that the corrosion is worst here, but it was out of sight and would never have been noticed if the rudder hadn't been dropped.
Based on the feedback given, my plan is to have a new shaft made in 316 stainless, use marine ply to make the blade, and then sheath it in glassfibre. It's going to be a learning curve, but should be do-able.
MacD
Attachments
sailorman
Well-Known Member
I would clean up the existing mouldings & reuse them
