Niander
regular
Reged: 25/06/2003
Posts: 412
Loc: Outer hebrides
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actualy the glue is doing very well
and the hull is built strong as hell
but what has gone are the ribs down in the bilge so im gunna epoxy/laminate 8mm
strips 3 times 8 mill is same as existing hieght
oak ok ?will it bend right down into the bilge?
any ideas/advice how to welcome...
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Grajan1
regular
Reged: 12/04/2008
Posts: 82
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Sister timbers,
They can be steamed, but it is far easier to make up a jig and laminate.
Depending on where they are, you might have to go to four laminations and remember to overset them slightly to allow for the spring back when you remove the clamps
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srp
regular
Reged: 10/05/2006
Posts: 1323
Loc: IoW
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There's really no need to put sisters in, and they are not a good way of repairing broken timbers as they make a localised hard spot, causing the neighbouring ribs to break (according to John Leather). Cut out the broken section of rib, and let in a section of new timber using a scarf joint. The new piece is prepared by laminating to the correct profile on a jig. Try and use the same timber as the original (usually oak or maybe elm). Glue the scarf joint with epoxy, don't glue the rib to the planking. Unless you have a friend who can help you with copper nails and roves, use silicon bronze woodscrews to re-fix the planking through the original nail holes.
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www.corribee.org
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AndrewF
regular
Reged: 24/06/2007
Posts: 51
Loc: Tollesbury
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I personally would replace like with like and use steamed ribs, but thats just me. However if there are several broken ribs in the same area, the cause should be investigated before replacement, as it could be an indication of something more sinister. Like the boat has either been stuck or pinched, or it could just be that the shape of the boat isn't fair in that area and this could just be a problem from when it was built.
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Mariposa
regular
Reged: 27/04/2003
Posts: 1674
Loc: Clyde & Tunisia
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Just fixed a few of Mariposa's broken ribs. I used American White Oak (from Robins), 6mm thin and laminated in a jig to the desired curve plus a bit more. I had to steam the oak to get into my jig.
I cut out scarfs to the nails above and below the break which gave me 8:1 or 9:1 scarf ratio. It was still a bit fiddly to get the new sections shaped to fit well but I managed.
Dry fitted and drilled undersized through the old holes in the plank I then glued them up with epoxy. Self tapping screws (thinner then my #10 copper nails) held it all together until the glue set. I then called in my dolly bird to hold one of my pieces of lead internal ballast against the nail while I riveted up. Each repair is therefore glued and secured by 6 riveted nails. 7 done, a few more to do.
Mariposa spent too long on a drying mooring before I got her. I suspect bouncing on her bilges twice a day for a couple of decades may have contributed to the problem.
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The cure for most of life's ills is salt water.
Sweat, tears and the sea.
http://myfamilyandotherthings.blogspot.com/
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Niander
regular
Reged: 25/06/2003
Posts: 412
Loc: Outer hebrides
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Do you think 8 mill will bend in the bilge or do i need 6 mill to cold bend then epoxy and hold together with screws...then is it ok to screw into the ribs from the outside of hull using s/s screws?
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Mariposa
regular
Reged: 27/04/2003
Posts: 1674
Loc: Clyde & Tunisia
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I think you'll really struggle with 8mm. I did with only 6mm!
Are you thinking of using st/st screws as permanent fixings? I wouldn't, especially below the waterline. I know there are different grades of stainless but it does tend to corrode away when deprived of oxygen; like when buried in wet wood.
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The cure for most of life's ills is salt water.
Sweat, tears and the sea.
http://myfamilyandotherthings.blogspot.com/
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oldfrank
regular
Reged: 07/12/2005
Posts: 206
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How many timbers?
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Mariposa
regular
Reged: 27/04/2003
Posts: 1674
Loc: Clyde & Tunisia
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Quote:
How many timbers?
Not sure what you're asking.
How many frames repaired: 7
How many left to do: more than I anticipated
How many 6mm laminations per repair: 3 or 6 depending on the rib.
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The cure for most of life's ills is salt water.
Sweat, tears and the sea.
http://myfamilyandotherthings.blogspot.com/
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pcazeles
new user
Reged: 14/04/2008
Posts: 3
Loc: France
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Personally in January I made sister-ribs for my 20 broken ribs and I first tried to laminate 6mm marine plywood but I found it pretty hard. Eventually I cut all sisters directly in oak and epoxied it to the ribs.
Will see how it goes and if sistering isn't good as I afterward read many times in forum posts and US reference books, I'll go with 3mm marine plywood scarf joint.
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