Using Ethylene Glycol on rot damaged GRP covered stringers and bulkheads to arrest further decay

[Martin Upton]

Hi all, I have a Southwind 655 (Australian boat) that has water in the stringers and bulkheads (covered in fibreglass). I suspect the aft bulkhead / stringers is sea water and the forward section is fresh (rain) . I took some core samples from various sections and found some rot forward but it looks like lessens to nothing (despite dampness) as I went further aft. Ripping it out and replacing it is prohibitively expensive with moulded decks etc.
On the forward bulkhead there was excessive dampness and rot at the base but solid (and damp ) as I tested further up the bulkhead.
This particular boat has solid layers of fibreglass over the timber (ie quite strong and rigid).
I’ve been reading about ethylene glycol as a method to stop rot and am wondering about the practicality of attaching an evacuation pump to various locations at the base of the stringers and bulkheads (by drilling access holes into the glass) and likewise drilling holes further up to allow ethyl glycol to be drawn into the rot in the wood.
The intention here is simply to arrest further rot and damage and reduce the moisture in the wood as much as possible.
Has anyone tried anything like this?
Interested to hear what you think?

 

[bajansailor]

I wouldn't be too worried about rot in the stringers - I presume that they are a type of tophat section?
Their strength will come mainly from the shape and thickness of the fibreglass over the former in the stringer.
If you are worried, you could maybe abrade them thoroughly and add another layer of fibreglass over them, if this is possible?

I would be more worried though about your bulkheads - even if they are covered in fibreglass on both sides, they are relying on the timber core to keep the two skins apart (like an 'I' beam effect - the fibreglass skins are the flanges on the I beam, and the timber core is the web).
And if you have a rotten core, you will eventually end up with two floppy skins that are not much use.

The WEST epoxy folk have lots of free information on their website - they are keen to give you the info, as they recommend using their epoxy products. Have a look through these three booklets re fibreglass and wooden boat repair - lots of good stuff in there and some of it should be applicable / relevant to you.

Epoxy User Manual & Product Guide - WEST SYSTEM Epoxy https://www.westsystem.com/instruction-manuals/user-manual-product-guide/

https://www.westsystem.com/wp-content/uploads/Fiberglass-Manual-2015.pdf

https://www.westsystem.com/wp-content/uploads/Wooden-Boat-Restoration-and-Repair.pdf

 

[Ike]

Using ethylene glycol is just a stop gap measure. Eventually you will have to replace the wood or do some other method to replace the stringers. Using it just delays the inevitable, just as is fiberglassing over a wood hull that has serious problems with the wood. It will give you a few more years of use but you will eventually have to do it right or get a new boat.

You should read through this thread Ethylene Glycol as a wood preservative https://www.boatdesign.net/threads/ethylene-glycol-as-a-wood-preservative.17739/

 

[Martin Upton]

I wouldn't be too worried about rot in the stringers - I presume that they are a type of tophat section?
Their strength will come mainly from the shape and thickness of the fibreglass over the former in the stringer.
If you are worried, you could maybe abrade them thoroughly and add another layer of fibreglass over them, if this is possible?

I would be more worried though about your bulkheads - even if they are covered in fibreglass on both sides, they are relying on the timber core to keep the two skins apart (like an 'I' beam effect - the fibreglass skins are the flanges on the I beam, and the timber core is the web).
And if you have a rotten core, you will eventually end up with two floppy skins that are not much use.

The WEST epoxy folk have lots of free information on their website - they are keen to give you the info, as they recommend using their epoxy products. Have a look through these three booklets re fibreglass and wooden boat repair - lots of good stuff in there and some of it should be applicable / relevant to you.

Epoxy User Manual & Product Guide - WEST SYSTEM Epoxy https://www.westsystem.com/instruction-manuals/user-manual-product-guide/

https://www.westsystem.com/wp-content/uploads/Fiberglass-Manual-2015.pdf

https://www.westsystem.com/wp-content/uploads/Wooden-Boat-Restoration-and-Repair.pdf

Hey bajansailor ... thanks for the info (it is encouraging). The stringers form part of the floatation tank (that is filled with foam ). So I can only get to the outside edge. Does that make a difference. The bulkheads are pretty accessible and appear to only be rotten in the bottom third. The top parts of them are solid but damp.

 

[Martin Upton]

Using ethylene glycol is just a stop gap measure. Eventually you will have to replace the wood or do some other method to replace the stringers. Using it just delays the inevitable, just as is fiberglassing over a wood hull that has serious problems with the wood. It will give you a few more years of use but you will eventually have to do it right or get a new boat.

You should read through this thread Ethylene Glycol as a wood preservative https://www.boatdesign.net/threads/ethylene-glycol-as-a-wood-preservative.17739/

Hi Ike. Thanks for your response. Life extension is all I was aiming for. Thanks for the feedback. It does appear that ethylene glycol does make a difference from everything I’ve been reading. What was wondering is there any way to get it into wood that’s covered with fibreglass?
Cheers

 

[Ilan Voyager]

Hi Ike. Thanks for your response. Life extension is all I was aiming for. Thanks for the feedback. It does appear that ethylene glycol does make a difference from everything I’ve been reading. What was wondering is there any way to get it into wood that’s covered with fibreglass?
Cheers

Ethylene simply NO as that does not work. That fixes nothing. There is not "after rot" treatment as there is a general delamination. Your boat is in life's end and will need a rebuild if you want to keep this model for some reason. Surely you can peel easily the GRP of all plywood pieces. You'll be badly surprised.
There is no other way: rotten or rotting wood/plywood has to be replaced. There is no chemical or resin that works. I agree totally with that Bajansailor said.
Reinforce the stringers with GRP and forget the wood.
Replace all the bulkheads. I's a major job.
That's a lot of work and think over if it's interesting on a cheaply made hull, probably of some age. GRP polyester over a web of timber/plywood was a cheap method with limited life span. It's well known that with this method the wood and plywood will delaminate from the GRP and will rot in a few years. The hull becomes flimsy. More than rotting general delamination is the true problem.
I've seen number of 30 to 40 feet Cigarette style in Cancun made in the USA with this method and it was unworthy to try anything.

I've fixed only one but that was a total rebuild. In a few words I installed the boat on strong and adjusted steel ship cradle/jig and I kept only the outer skin of the hull after cutting all the bulkheads and plywood pieces. That was a very dirty job.
And I rebuilt all the structure, except the stringers simply reinforced with glass, plus the decks/floors in Nidacore and GRP. That was a lot of work, personally I think it was too much work for the obtained value.
In this case the hull was just a general shape and design that owner wanted to keep, after all the internal structural work I installed a 6L Mercruiser with a Bravo 3 with fresh water cooling in replacement of the outboards. In fact that was a new boat. The owner was happy as the old/new boat worked very well. That's the most important.

 

[fallguy]

Have you determined the source of ingress?

It sounds like multiple sources; rotting stringers, bulkheads, transom. If you have seawater aft and rainwater for'd.

You are at a diseconomy on that boat. That is, the cost to repair in time AND money is greater than the boat's value.

Glycol isn't even lipstick on the pig here.

Part it out, get some money for engines and fixtures; haul it to the dump for crushing, sell the trailer.

Survey the next boat well.

 

[bajansailor]

For reference, here are a couple of Southwind 655's for sale :

This one is from 1998, with an asking price of AUS$ 22,900 -
https://www.boatsales.com.au/boats/details/1998-southwind-sf655-cabin/OAG-AD-18241412/

And this one is from 2001, with an asking price of AUS$ 52,000 -
https://www.boatsales.com.au/boats/details/2001-southwind-sf-655-classic-series/SSE-AD-5915495/

Martin, could you post a few photos of the damaged areas on your boat please?

 

[fallguy]

For reference, here are a couple of Southwind 655's for sale :

This one is from 1998, with an asking price of AUS$ 22,900 -
https://www.boatsales.com.au/boats/details/1998-southwind-sf655-cabin/OAG-AD-18241412/

And this one is from 2001, with an asking price of AUS$ 52,000 -
https://www.boatsales.com.au/boats/details/2001-southwind-sf-655-classic-series/SSE-AD-5915495/

Martin, could you post a few photos of the damaged areas on your boat please?

I stand corrected. But that boat sounds like it needs 500 hours.

 

[bajansailor]

I was initially thinking that maybe this was a 65' long vessel until I googled the Southwind 655 - and that Martin would have an enormous project ahead of him.
I was much happier to see that his boat is 6.5 metres instead!
But as Fallguy says, it is still going to be a lot of work required, even on such a comparatively small boat.

 

[Ilan Voyager]

It's a lot of work, even on a small boat. I know by first hand experience.
Happily it's feasible on a small hull, that will take time and sweat but nothing monstrous.
First you have to make a cradle even primitive as a boat without bulkhead is a bowl of jelly. Without cradle the boat will be deformed.
Probably a lot of bad discoveries will be made, it's always the case in dampness and rot. It's like rust bubbles in a car...
Surely the bulkheads are delaminated, I mean that even if the wood looks not rotten the GRP can be easily delaminated. Very probably all the pieces of plywood have to be removed.
The ingress of water is simply by all the holes, porosities of the GRP and the fact that polyester is not waterproof in the presence of the phenol of the wood which disturbs the curing of the polyester.
It's a known fact since more than 50 years since the first trials of using GRP over wood. A loot of recipes have been proposed and tried, the lone that works relatively well is to heavily impregnate the wood with polyurethane to create a compatible interface between the wood/plywood and the GRP. That was proposed by Vosschemy at the end of the sixties...That shows that the problem is old. The final cost is similar to the use of epoxy...
The resin that permitted to have a long lasting composite wood/plywood and glass is epoxy. I counsel to make the reparations with epoxy.
Epoxy glues very well on a cured polyester (but polyester does not glue over a cured epoxy as the amines of the epoxy hardener inhibit the curing of the polyester). The reparations will be easier with less glass, and far less smelly. A lot of plywood pieces will need only three epoxy coats and a good putty to glue with some biaxial tape. Pretty simple in fact. Probably lighter. Surely nicer.

 

[Martin Upton]

I stand corrected. But that boat sounds like it needs 500 hours.

I stand corrected. But that boat sounds like it needs 500 hours.

Hey fallguy. Thanks for checking that out. You must be in Australia (as am I) I have actually checked out the 22k boat myself and it also needs work.

at the moment there doesn’t appear to be any delamination of any of the GRP with timber and I recently had three different fibreglass guys check who all told me that the boat was rock solid (that’s why I took it on myself to dig further (literally).
I realise that ultimately the boat will be worth the motor and trailer however in the meantime all I want to do is to prolong that day arriving as much as I can. Whilst I don’t mind ‘projects’ my wife has banned me from them (which is probably a good thing) so all I’m wanting to do is to delay the inevitable for a few years. Thanks for going to the trouble to check it out for me .
Cheers

 

[Mr Efficiency]

Where are you using the boat ? I think I'd install some buoyancy foam and forget your worries, if the worst happens, you won't sink, at the end of the day, that is the main thing.

 

[Martin Upton]

Where are you using the boat ? I think I'd install some buoyancy foam and forget your worries, if the worst happens, you won't sink, at the end of the day, that is the main thing.

Hey Mr efficiency, that’s pretty well what the fibreglass guys said also. They recon I have years left in it but me being me are trying to find ways of making work for myself

 

[trip the light fandango]

I'm surprised no one has suggested drilling through the bulkheads and forcing or injecting epoxy mixed with some flock ,making sure it makes its way through. Tubes could be inserted first then resin impregnated glass. as another approach. The main issue is making sure the bulkheads don't separate, collapse or fold.
The filled holes need to be placed carefully/stucturally and finishing with a layer of matt on each side if possible,.. would add peace of mind. rainage holes at low points for all saturated timber would also help I think. Disclaimer, I'm a relative novice. good luck