How do I split a GRP rudder ?

[alec]

I have a rudder approx 6 feet long by 2 feet wide. It leaks in about three places and there is a slight crack at the top of the rudder near the stock.

Ideally, I would like to split it in two and fully investigate the metal innards and attend to anything else that needs doing. The boat is 35 years old.

It seems to have a seam around it that suggests it was glassed together in two halves.

Has anyone any idea how I go about slicing it in two ? If so, what tools approach etc would I need. Could I still salvage it ?

Is there any chance of doing it in situ as I have a 4' 6” bilge with diabolical access to the rudder foot stud which is only accessible from the inside of the boat under the engine.

Any suggestions would be most appreciated.

 

[boatbuilder]

use a fein cutter , wich oscilates rather than revolves. Only prob , very expensive.
On the other hand a 41/4 " grinder with a diamond wheel will do.

 

[exfinnsailor]

Dremel might do it .. Used one on a FINN rudder a few years back .. Cut all round the edge and then opened it .. Had to use a knife to cut the foam that was inside .. Might be easier to use the Dremel to cut a trap door in the side .. If you do it at an angle you should be able to pop it back in again .. /forums/images/graemlins/smile.gif

 

[ShipsWoofy]

[ QUOTE ]
Dremel might do it .. Used one on a FINN rudder a few years back .. Cut all round the edge and then opened it ..

[/ QUOTE ]

Was that a model boat? You could spent a day with a Dremel on mine and hardly make a dent.

 

[willie4646]

unless there is movement between the stock and the blade, I would advise you to leave well alone, just patch up the crack.The rudders on my catamaran became loose on the stock so I decided to split the rudders,a wrong move! The two halves of the rudder were not only glassed on the outside but the metal armature was glassed internally. The upshot was that I almost destroyed the rudder trying to split it, I ended up getting two new rudders made.
Willie

 

[Blueboatman]

Firstly you may find it helpful to detach the tiller or steering quadrant to allow 90degree rotation for attacking all edges...

As said already, cut round the edges .
If it refuses to separate (likely)
go round again with a deeper blade and then use lots of very very slim wedges-the more the better- to pursuade it to peel open.The grp will tolerate a small amount of flex without gelcoat cracks.
Reassemble with epoxy,bolts and clamps (you can always remove the bolts once set and fill the holes).
I have only done this once.
Whilst I was at it I cut a 25mm hole through near the aft edge in order to facilitate attaching a rope in the unlikely event of breaking thew tiller/bracket at some future date offshore..

 

[mandlmaunder]

Before you take a blade to your mostly ok and in 1 piece rudder take a mould so that when or if it all goes wrong you can strip the old grp off and remould to the pintles

 

[Blueboatman]

Excellent idea !

 

[boatbuilder]

Well them Oceanics were built strong. /forums/images/graemlins/smile.gif

 

[oldsaltoz]

G'day Snowgoose100,

Most rudders are mass produced under contract to major builders, there is wide range in type and construction but the basics are: Rudder stock with tangs welded to the stock extending aft, some have a flat vertical plate to join the aft end of the tangs. Most have the tangs glassed to outer case on at least one side, the other side may be supported by chocks or other fillers including rubbish foam that turns to mush if it ever gets wet.

Because a stainless Shaft and fibreglass expand and contract at different rates it can be a problem preventing water entry.

I have repaired a few rudders over the years and fit 2 '0' rings over the shaft and squeezed together with a little Vaseline under them to stop resin getting in has been very successful.

To split a rudder I use an angle grinder with a diamond wheel, this leaves a nice thin cut, you need to go all the way around the outside edge, you may need a hacksaw blade close to the rudder stock.

You also need to know the location of the tangs welded to the rudder stock, these are glassed to at least one of the two sides of the rudder case.

To locate then simply drill small holes in a grid pattern or around 100mm, when you locate a tang try to follow it and mark each hole that found contact with metal.

You should end up with a profile of the rudder frame, now you can cut windows through the side that will allow you to remove one side of the rudder case.

Hope this helps.

Avagoodweekend......