Coach-roof beams delaminating

[pugwash]

I have a Holman 31ft ketch (a bit like a bigger Twister) built by Uphams of wood in 1969. The curved beams inside the coach-roof are laminated and coming apart. So far three beams are cracked and each crack, very thin and with tapered ends, is about two feet long. My plan is to stuff the cracks with epoxy and push the whole thing carefully upwards using a twist-jack (the kind builders use to hold ceilings up while working on them) and to pad the top end with a piece of wood cut to the required curve of the beam. The strip which is coming free is taking the shortest distance between two points, like the string of a bow, and is under great tension.
Questions:
(1) Does anybody have experience of this problem?
(2) What kind of epoxy would you recomend?
(3) Does my plan hold water? It will be a big winter job.
All thoughts will be welcomed. Thanks.

 

[Topcat47]

I'm sure there are owners about who are much more experienced wood butchers than me, but I'm not sure your idea will run.

Assuming the cracks are along the glue lines, itself quite unusual (it's more normal that the timber has failed) in order to get a good bond with anything you need to get a good key for the new adhesive. This almost certainly means removing the beam, separating it along the cracks, cleaning off the old adhesive and re-gluing....

An alternative would be to get angle-iron curved to the shape of the bottom of the beam and fix it with screws (and epoxy if you really want belt & braces). This will add stength to the beam without the need to remove and re-maufacture it. You can take the curvature from an adjacent beam if it has not begun to delaminate.

 

[Mirelle]

Why are the laminations failing?.

Since the lamination that has separated is taking the most direct route, it must be under tension, so the question is "why is it under tension?"

It was probably under tension from new, i.e. the curvature of the beams was sharper on the jig than in the boat.

I would cut out the lot and start again, beam by beam, laminating in place.

I think the repair will be fairly simple; much like cutting out a frame and laminating a new one in place, only you will be working overhand, not downhand.

(Expect glue in your hair!) /forums/images/graemlins/wink.gif

 

[Blueboatman]

Any chance of a piccy ?...
Are the ends of the laminates free to be prised down and away from the remaining strips , is it just the lowest strips,is the delamination appearing in the central part(as opposed to the ends) ?
And are the beams varnished ?......Because
The glue used originally will still be in the cracks,albeit hard and fractured and attached to either of the 2 wood faces-And you are now asking epoxy (which is wonderful stuff) to adhere to dodgy old glue and not to nicely abraded wood.....
So the open joints will need to be abraded in situ-using eg 80grit paper and or hacksaw blades....which will mess up the neatness of the original glueline visually,if the beams are varnished......
And then lastly you have got to work the new glue into and along each failed glueline from both sides using a brush,(maybe carefully opening up the joints furthar using thin wooden wedges tapped in..) sufficiently deeply to do the job,and this is overhead work so lots of newspaper and decorators plastic sheeting needed on the bunks and sole below as you start to cramp each reglued beam up into place-And it may actually be better to consider adding screws down through the coachroof,you will be securing the whole lot together mechanically,ensure even cramping,and get lots of cramping pressure without possible risk of lifting the coachroof away from the cabin sides.Those accro props are very,very powerful !
Sorry this is so wordy..

As I say ,a piccy might be helpful at this stage before contemplating what is the most appropriate course of treatment .

 

[pugwash]

More info

Appreciate your replies but they have raised some questions which I'll try to answer.

The boat's in Devon and I'm now back in London but I'll try for a pic next time I go down.

It doesn't look like a wood fracture, I'm pretty sure it's the glue that's coming away.

The beams are painted white. They measure about 2.5 inches square. The layer breaking away is the lowest and barely 0.25 ins thick so screwing from top down is not an option, but nuts and bolts with big washers could work.

The ends of the beams are dovetailed into the complex joinery forming the coach-roof sides and the deck, and I couldn't possibly explain this in words! The delaminated area is just slightly off-centre, not by much. To remove the beams would be a huge job.

I'm also pondering one thought -- if I do nothing, or just fill and paint, will it matter?

 

[Joe_Cole]

I think that it will be difficult to get enough glue into the crack to make an effective repair but, as it will be such a difficult job to do any other way it's worth a try. Is it worth trying some kind of syringe to get the glue in?

I can't help but wonder why, after 35ish years this has started to happen. It sounds as if there is more downward pressure on the coachroof to "spring" the lower laminate. Have you changed the rigging or tightened it more than usual? Surely something must have caused this? Just curious.

With regards your very last question. As you won't be doing anything for a few months it may well be worth carefully measuring/marking the split to see if it is moving. If it is stable then it may well be worth ignoring for a while.

 

[Strathglass]

Re: More info

It sounds a bit like an inverted version of using laminated floors in a wooden hull.
It will be extremely difficult to reglue the delaminated beams without removing them and cleaning the old glue out. As you have said the removal of the existing beams would be quite a long job.

This is just one pissible solution. Why not add doublers? this would be the first considered repair to floors on a wooden hull.

You could make up strips the same size as the existing strips, then, after jacking everything back into place you could epoxy new beams adjascent to each of the existing broken ones. You would obviously have to remove all the paint from the contact area but this would avoid you having to alter the existing dovetailed ends.

Ok your batons would be twice the width but so what?

I could go into it in much more detail but that is one possible solution.

Cheers

Iain

 

[clyst]

Re: More info

Remember which ever way your effect the repair get it wrong and you will greatly devalue the boat. Any self respecting surveyer will pick up on a "bodged" job in this area ie "doubled" beams etc. Dont rush into the repairs . Delaminating coach-roof beams are no great deal in the short term . Its not the end of the world to remove the coach-roof and refit new beams using the old as patterns .

 

[Forbsie]

Re: More info

[ QUOTE ]
Its not the end of the world to remove the coach-roof and refit new beams using the old as patterns .

[/ QUOTE ]

Earlier this week I watched a mate do exactly this. I found it fascinating how simply he made the curved beams by cutting the required curve in a beam and then put the bottom piece on the top piece and you have your curved beam.

Absolutely simple but ingenious.