Rudder split repair.

[jonjo]

My GRP rudder has a high aspect profile and is 4' to 5' deep. Here is another example of the same design for sale.

http://www.ancasta.com/controls/thumbnail.aspx?Height=291&Width=395&MediaId=157029

When hauling out last season I noticed a little moisture weeping out of a split on the aft trailing edge of the rudder about 1/3 of the way up from the bottom. The GRP mouldings that form the rudder shell have separated over a 6" length. The split can only be seen close up and it takes some force to open the split with a screw driver.

To fix and prevent this reoccurring I think I need to stick the 2 mouldings back together with a large spot weld in GRP. Given the very narrow cross section of the rudder at the trailing edge I think the best way to achieve this "spot weld" is to grind out 100% of one of the rudder moudlings about 4" beyond the split vertically and about 6" inwards.

After giving the remaining GRP a month to dry out in the spring the intention is add solid GRP layup to bring the rudder back to its original shape. The end result will be a giant GRP spot weld in place of whatever resin potion was used to stick the rudder mouldings together when the rudder was fabricated. Obviously I would feather the new layup much further beyond the 100% grind out.

What does the resident PBO forum committee think? Would 1 month of drying be enough? Is there a danger that next time I broach the extra thick section of the rudder at the spot weld will not flex uniformly with the rest of the structure thus putting strain on the adjacent area?

 

[Jaramaz]

rudder repair

Not an unknown issue. Many rudders are prone to leak water, which in wintertime will have the usual effects.

Without seeing you rudder it is difficult to say if your repair strategy is sufficient. You seem to know your way with grinders ...
If the damages are minor, then I would try to fill with epoxy (+ filler) instead and then put some press on this. It is far more easier!

However, you ask about if one month drying out is sufficient. Impossible to say, unfortunately! For the grp you see, one month is OK. But what is behind? Is there any more water in the rudder?
You can check:
1) drill some few small holes in the lower part. If water appears ...
2) Moisture measurements. There are some rather cheap instruments available, to buy or rent.

Water inside the rudder must be removed.

Many drill a hole in the aft lower part of the rudder for drainage, put a screw in it for use in water, and take out the screw when putting the boat on dry. Possible to add some Sika or similar in the process.
This is accepting that the rudder do take some water, but limiting future damages.

One possibility is the check with the manufacturer of the rudder: design and production. They probably have some experience.

Jefa (http://www.jefa.com/) makes rudders for those in need of a new one, which indicates that rudder problems are not unusual.

/J

 

[Blueboatman]

Drain hole at bottom( as said)
Grind a slot down the offending split with the edge of a angle grinder, remove salt contamination by Painting with acetone a couple of times, then apply epoxy/colloidal silica mix and sand smooth when cured

For belt n braces repair grind off a strip of the gelcoat 30mm back down each face of the aft edge, apply epoxy and tape( epoxy friendly glass woven cloth), then epoxy filler then sand it all smooth when cured. You have effectively wrapped the weak joint and bound it as wot it should have been done by a conscientious amateur builder!

 

[jonjo]

Grind a slot down the offending split with the edge of a angle grinder, remove salt contamination by Painting with acetone a couple of times, then apply epoxy/colloidal silica mix and sand smooth when cured

That could be tricky because the aft and flat face of the rudder is probably only about 8mm wide (it is a racy design) but mine is not raced.

For belt n braces repair grind off a strip of the gelcoat 30mm back down each face of the aft edge, apply epoxy and tape( epoxy friendly glass woven cloth), then epoxy filler then sand it all smooth when cured. You have effectively wrapped the weak joint and bound it as wot it should have been done by a conscientious amateur builder!

This is an attractive idea because:

1. It is less destructive than my idea of grinding out a 10" x 6" section on one side of the rudder.
   
2. Also it would prevent something similar happening along the rest of the aft rudder moulding joint.

Could you put some numbers on the cloth weight and total layers in view of the tight 180 degree wrap the cloth will make around the narrow 8mm after face of the rudder?

 

[davidej]

You can get g/f cloth as fine as net curtain material. Three of four layers of thatwould fold over better than one thicker layer.

I suggest you cover the patch with polythene sheet, then put a thin batten on each side to hold it in position.

Clamping the battens might be difficult as they will tend to slip - you can get clamps like large clothespegs which might be better than G-cramps. Strips of gaffertape might do the job.

 

[HunterWanderer]

Mine was cracked badly in several places so I ground out the cracks with a small angle grinder and filled the cracks with normal body filler.
I then sanded it all down and covered with 2 layers of 1 1/2 oz mat. I then roughly sanded it and filled again where needed.
I then applied 2 coats of epoxy resin taking it up the stainless rudder stock about 20 mm so it didnt reach the rudder bearings.

Sounds a lot of work but doesent take that long really and less than £50 materials. I had drilled a hole in the rudder at the bottom when I hauled out so had been draining for 4 months.

Was done 6 years ago and no reoccurence.

 

[Blueboatman]

davidej got there first.!

Dont forget that you can actually lay up all 3 or 4 layers on a piece of non absorbent old worktop or painted worktop and then press them into place as one-much easier than working on a vertical surface repeatedly.

Also, wearing two pairs of disposable gloves means that if you do get the cloth all stuck to your glove and messy, simply peel off one pair and carry on pressing the cloth into place. ( by the way)

 

[SAWDOC]

If it is straightforward to remove the rudder you can dry it more effectively indoors but consider this carefully. You normally need a depth greater than distance to ground vertically under the rudder to drop the rudder plus stock if you get my meaning.

 

[HunterWanderer]

I did it with the rudder in place.

Just roller a coat of resin onto the surface, press on the dry mat and roll on more resin with a lambswool radiator roller then roll out the air with a metal disc roller. Leave till its gone off a bit then put on the second layer onto the tacky surface.

 

[SAWDOC]

I found this slideshow and commentary on rudder repair very interesting

http://www.sail.ie/quarterton/rudderjob.htm