Jeanneau fantasia rotten engine barer.

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Paul06

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Hi everybody,
I have a 1986 fantasia which has a rotten engine barer.
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In the picture you can see the barer behind the battery. It is approx 35mm thick ply glassed over. At some time before I bought her water has got into the ply, which is now rotten.
The engine sits on two steel channels which are bolted through the ply.
Over the winter I want to repair or replace this barer.
I have come up with 3 options..

1: remove the engine, cut out all the wood/fibreglass and glass in a new piece.

2: support the engine, cut the top off the barer, scoop out all the ply and pour a resin/fibreglass mix into the space between the fibreglass cheeks.

3: support the engine, cut away the front fibreglass face then remove the ply. Then using thickened epoxy, bond a new piece of ply to the rear fibreglass face then re glass over the front of the ply.

I think no1 would be the best way, but no2 and no3 would be a lot easier to do.
I would prefer to just cut the top off remove the ply then pour a mix of resin/fibreglass in.

Thank you in advance for your ideas..
Over to you.....
 
That Yanmar is small enough and light enough to remove, then you can do No 1 - remove the rotten transverse floor and glass in a new one.
 
Whatever you do do not follow what has been installed. I would bet anything this a failure because 'someone' wanted to save money/time.

The glass over should be an epoxy based system, if not throw it away or grind the lot off and start again.

The bolt holes should be drilled out oversize and filled with an epoxy and Micro-fibres, then re drilled to size and consider installing a stainless steel sleeve after using an epoxy to secure it in place.

I would also be looking at alternatives to ply in this location.

What ever happened to boat builders with pride and good workmanship. Oh I know, they went broke...

Good luck and fair winds. :)
 
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I would have thought trying to do 2 would be hard to do well unless all the ply is completely rotten. You need to ensure a good bond to the side walls as that is where the thrust loads are going. I assume the battery box side walls are also bonded to the floor and also distributing load. If you really don't want to do 1which is the best then 3 is probably next best. Make sure the holes are protected as oldsaltoz suggests.
 
If you take the engine out you'll have the opportunity to clean it up as well as the engine bay.

I don't know much about the mechanics of how it should be mounted, but if ply and glass has lasted for 28 years then that's not bad ...
 
Thinking about this logically, the plywood is there for form support but the glassfibre is the strength in this bearer. The plywood rotting will not weaken the glassfibre. It may cause it to flex slightly more than with the plywood in place. Remember many stringers and keel rib formers are made out of foam, and this has no strength all compared to plywood.

Try and remove as much of the rotten plywood as possible. Spinning an alum key in a small hole will remove large areas. Then fill the void with an epoxy epanded with a mixture of micro spheres and chopped strands. This will give more support and strengthen the existing fibreglass. I certainly would never cut the top off the existing fibreglass. All you may need to do is drill small additional access/filler holes, but this should not reduce the strength of the existing fibreglass. There is no need to add any additional plywood backing plate.
 
Thanks for the replies so far. I think the water has got into the ply through one of the many holes that have been drilled through it by a previous owner to pass cables and pipes through. Yes the engine is removable, not easily, but it is.
The engine barer's are also bolted at the back of the engine through a 2" thick pad glassed onto the sides of the engine bay, so I think the thrust would easily pass through them.
My idea of cutting off the top, removing the rot and pouring in a resin fibreglass mix came from people using a foam core rather than wood. The strength being in the glass rather than the ply.
I know in a perfect world, the best job would be to remove the engine, cut out all the rot grind away all the old glass and start again, but if option two will produce a barer that is up to the job, why turn a days job into at least a weeks work.
 
As was said above the wood is only a former.Leave the sodden wood inside and don't open up the stringer.Break the battery box off and with a hot air gun and a carbide scraper remove the flow coat.It's easier than it seams.Then cover the stringer with a few layers of heavy rovings and epoxy .Rebuild the battery box and cover it with some lighter rovings.Paint the whole thing and it's done.You can leave the battery box intact but it'll be more difficult to do a neat job of scraping the flowcoat and relaminating.
For the stresses involved you can even use polyester resin Csm and rovings, just make it thicker than you would with epoxy.
 
I'd go with option 2 as the GRP is the strength and the ply (as already said) just the former. Scrape out all the rotten ply. Let the rest dry thoroughly and then fill with epoxy. If you want to add more strength, put some steel rods into the epoxy similar to reinforced concrete!
 
PCUK said:
I'd go with option 2 as the GRP is the strength and the ply (as already said) just the former. Scrape out all the rotten ply. Let the rest dry thoroughly and then fill with epoxy. If you want to add more strength, put some steel rods into the epoxy similar to reinforced concrete!
Click to expand...

Epoxy is expensive stuff.If you're going to fill the void then do it with wood and epoxy putty.It'll be much stronger as the resin by it self is heavy but not so strong.And unless you use special casting resin if you fill it in one go you risk setting the boat on fire.
 
Concerto said:
Thinking about this logically, the plywood is there for form support but the glassfibre is the strength in this bearer. The plywood rotting will not weaken the glassfibre. It may cause it to flex slightly more than with the plywood in place.

It's common practice at the design stage to size the ply to take the bulk of the load and then add a coating, in this case fibreglass to protect it. If the ply fails you have 'lost' most of the design strength.
The reason behind making the ply take the load is cost. Building in enough glass would add significantly to the cost of production, also worth noting is that 28 tears ago epoxy was in common use in all areas of boat building. We now know that poly based resins only last around 15 years before water penetrates the thinner layers as used in timber ribs back then. The modern stringers have a lot more fabric over them so timber is not required with the combination of epoxy resin and cloth designed for purpose.


Remember many stringers and keel rib formers are made out of foam, and this has no strength all compared to plywood.

Try and remove as much of the rotten plywood as possible. Spinning an alum key in a small hole will remove large areas. Then fill the void with an epoxy expanded with a mixture of micro spheres and chopped strands. This will give more support and strengthen the existing fibreglass. I certainly would never cut the top off the existing fibreglass. All you may need to do is drill small additional access/filler holes, but this should not reduce the strength of the existing fibreglass. There is no need to add any additional plywood backing plate.
Click to expand...

Good luck and fair winds. :)
 
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