P bracket question

[Colin_S]

P bracket on friend's yacht has been a bit loose for a while, with a gap between the bracket and the entry into the hull. When it was dismantled for repair last week the mounting bolts were found to be tight and the cause is thought to be down to a poor repair of the GRP where it passes through the hull last time it was installed.
What has been noticed and is giving a bit of cause for concern is that today, a week later there is still water dripping from the hole although the interior of the boat is dry.
Is this likely to be water that leeched into the hull materials over the year or so that the bracket has been loose now finding it's way back out? If so, and the bracket is refitted and glassed in, will any residual trapped water be a problem?
Boat is a 34' Contessa BTW.

 

[Sheff]

Don't quite follow the configuration of the P bracket.
I am currently trying to affect a repair to my loose P bracket but it is purely a "glassed-in" mount and there are no "mounting bolts".
My repair will be to drill internally to the P bracket casting at several points and inject acetone to clean and remove moisture then inject epoxy resin by means of a syringe to fill any voids around the P bracket.
This repair has been tried locally by several boatowners with a similar problem and..... so far...... have been succesful.

Paul.

 

[oldsaltoz]

G'day Colin,

Sounds like your friends 'P' bracket is the type that have the bracket glassed in and a bolt passing through the bracket, this is used more to hold it in position when glassing rather than hold it period.

The logical point of entry would be the gap, but the main concern is that it is loose.
I suspect it needs another full repair to ensure the last one has not delaminated and is holding water, simply sealing it externally will cause major problems down the track.

You can round off the corners of the bracket and pickle them to prevent corrosion then add 2 or 3 very thin '0' rings with a tiny dab of Vaseline under them to form a seal inside the fibreglass. I would also advise any repairs be done with an epoxy resin and cloth designed for epoxy, not CSM (Chopped Strand Mat).

Also check that ply has not been used as backing, if gets wet it will soften and you have a loose bracket. I like to fully glass 'P' brackets when repairing them and have never had a problem using the '0' rings and epoxy resins & cloth.

Please let us all know what you find.

Andavagoodweekend......

 

[Colin_S]

I probably asked the wrong question here as it's more about water getting into the fibreglass that is the concern.
Anyway, I'll try and dscribe the setup although a picture would be a billion times simpler.
The P Bracket is like a long blade with the prop shaft guide on the bottom. It fits through a slot in the hull and roughly half it's length is inside the hull where there are 2 vertical flat metal bars that it slides between and that have through bolts to secure the top of the bracket. This is all then enclosed in GRP. Any clearer?
The issue is where the pracket passes through the slot in the hull. The slot is slightly larger than the bracket and, whatever the gap was filled with has failed allowing some lateral movement of the bracket and so let water into the hull materials and it is this water that is now slowly finding it's way back out.
Should this water be allowed to completely dry out before the bracket is glassed back in or will it a) cause no harm or b) dry out and escape some other way?

 

[john_morris_uk]

I am suprised no-one has answered your first question. If it was me, I would be removing the bracket, and trying to dry the area as much as possible before refixing it in place. If water is dripping out, it has got into voids in the GRP or into a gap between the p backet and the hull/slot it sits in. The only option for a proper repair is to grind back the GRP until you get to good material with no voids and then allow to dry and reglass. I would be using epoxy, but there are others on the forum who are better and with more knowledge regarding GRP work than me!

 

[oldsaltoz]

G'day Colin,

Much clearer now. Just letting it dry will not fix the problem if the water is coming from between the laminates of glass; if the 'P' bracket has been removed, clean the edges inside the gap and check where the water is coming from.

It may be that the last repair job was a bit on the light side and movement has caused the failure.

If its leaking between the laminates it needs to be re glassed after grinding.

If you do not remove the voids the problem will not go away, sealing water in will result in problems later, possibly osmosis or wicking.

Before you remove the bracket take note of the clearance allowed, if too large your sealant may fail again, this area needs to able to flex but move around as this causes sealant failure. 3 mm is fine.

After cleaning the inside to look for the location of the leak, check that the edges have been coated and not left raw, if raw, it could be a part of the problem.

When glassing in the bracket retaining plates ensure you have a fillet around the base to provide a smooth transition for the glass, this will improve strength if using an epoxy, the fillets should be a mix of epoxy resin and Micro-Fibres, very strong.

make sure the 'P' bracket is aligned by fitting it between the fixing plates and having the prop shaft through it when glassing in.
The remove it after glassing and treat the edges of the slot through the bottom, you may have to widen it to get enough room to apply 4 or 5 coats of epoxy resin.

Let us know what you find when you remove the bracket.

Avagoodweekend.

 

[Colin_S]

Thanks for replies.


"Before you remove the bracket take note of the clearance allowed, if too large your sealant may fail again, this area needs to able to flex but move around as this causes sealant failure. 3 mm is fine."

What is recommended to seal the gap through the hull? IIRC plan is to pour in resin. Is this correct or are you saying a flexible sealant should be used?

 

[oldsaltoz]

G'day Colin,

Message seems to be missing a few key words, should read:

Before you remove the bracket take note of the clearance allowed, if too large your sealant may fail again, this area needs to be able to flex but not move around as this causes sealant failure. 3 mm is fine.

The 3 to 5 mm will provide enough space to insert the 'O' rings to ensure the seal lasts a long time, pouring just resin into the gap will result in weak joint; but if you add some micro-fibres to the resin and apply from the bottom up to exclude any air, you will have a very strong seal. When cured wash off any residue and apply 4 coats of resin wet on tacky.

Note: this method will make another removal more difficult as micro-fibres cure very hard and strong.

The flexing I mention above is taken up by the hull, a gap will result in movement and cause a sealant to fail.

Hope this helps.

Avagoodweekend.....

 

[Colin_S]

Cheers Brian - crystal clear now /forums/images/graemlins/smile.gif