CRACKED FRAMES

[pirate]

HAVE STRIPPED OUT MY 7 TON HILLYARD TO BEGIN REPAIR WORK ON THE HULL.
MY MAIN PROBLEM IS OVER 70 CRACKED FRAMES WHICH EITHER NEED REPLACING OR REPAIRING.I DON'T WANT TO SISTER THE FRAMES AND HAVING
READ AS MUCH AS POSSIBLE I'M CONSIDERING LAMINATING IN A NEW SECTION
INSTEAD OF TAKING OUT THE WHOLE FRAME.THIS SEEMS TO BE A RELATIVELY
NEW FORM OF REPAIR SO COULD ANYONE ADVISE ME AS TO ITS RELIABILITY,
TYPE OF GLUE REQUIRED, TYPE OF WOOD LAMINATES TO USE ON OAK FRAMES
ETC.
A LOT OF THE CRACKS ARE UNDER THE STRINGERS IN THE BILGE WHICH CAN'T
BE A COINCIDENCE.IS THIS JUST A WEAK SPOT ON A 74 YEAR OLD BOAT?
THE WORST TIMBERS ARE IN THE STERN WHERE THE CURVES OF THE FRAMES ARE VERY TIGHT.I WILL HAVE TO REPLACE THESE SO ANY ADVICE ON FITTING
NEW FRAMES AROUND SUCH A TIGHT RADIUS
THANKS FOR ANY HELP

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[Peterduck]

The cracks under the bilge stringer suggest to me that the boat has fallen on to its side at some time, probably into deep mud. The ribs above and below the stringer were unable to prevent the planking form being pushed in, but the stringer was able, causing the local stress concentration.
Use oak again, as that is what the original frames were, and aim to end up with the same section throughout. Make your laminae about 1/3 thickness of the ribs, and arranged like a car's leaf spring, so that you have the shortest against the planking, and the longest facing the interior of the boat. Make the shortest long enough to span from a point above the stringer to a similar point below it. Trim the rib ends to match the lengths of the laminae. Remove all of the old rivets. Glue up the laminae with epoxy [but don't glue to the planking] and re-rivet using the existing rivet holes before the glue sets. You'll need help for this bit. Pre-drill the rivet holes through the laminated ribs to prevent splitting in the rib. Start at the ends of the zone of cracked ribs, and work toward the middle. This is going to be a long job, but it will do wonders for the boat.
Peter.
Peter

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[Peterduck]

The cracks under the bilge stringer suggest to me that the boat has fallen on to its side at some time, probably into deep mud. The ribs above and below the stringer were unable to prevent the planking form being pushed in, but the stringer was able, causing the local stress concentration.
Use oak again, as that is what the original frames were, and aim to end up with the same section throughout. Make your laminae about 1/3 thickness of the ribs, and arranged like a car's leaf spring, so that you have the shortest against the planking, and the longest facing the interior of the boat. Make the shortest long enough to span from a point above the stringer to a similar point below it. Trim the rib ends to match the lengths of the laminae. Remove all of the old rivets. Glue up the laminae with epoxy [but don't glue to the planking] and re-rivet using the existing rivet holes before the glue sets. You'll need help for this bit. Pre-drill the rivet holes through the laminated ribs to prevent splitting in the rib. Start at the ends of the zone of cracked ribs, and work toward the middle. This is going to be a long job, but it will do wonders for the boat.
Peter.
Peter

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[PaulS]

<A target="_blank" HREF=http://www.kettenburgboats.com/yard6pics.htm>http://www.kettenburgboats.com/yard6pics.htm</A>

A pretty well documented project similar to yours.

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[snowleopard]

TS Tenacious was built entirely with laminated frames. they used siberian larch and epoxy. the wood was chosen for good density, flexibility and consistent grain.

your biggest problem with laminating in situ will be applying the pressure to keep the joint closed while the resin cures. the existing timber you are bonding to will of course have to be thoroughly dry first of course.

good luck.

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[Peterduck]

The pressure for holding the pieces together while the glue cures is provided by the rivets, which should be replaced immediately after the pieces have been put in place.
Peter.

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[BrendanS]

Interested, but no need to do this.

>>which should be replaced immediately after the pieces have been put in place<<

Replaced by what? New rivets, or just let frames set?





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[PaulS]

Could simply use copper or Monel staples to hold in place then attach permanently afterward. Copper or Monel should be no problem if left in place.

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[Peterduck]

The old rivets, which have been removed, should be replaced by new rivets before the glue cures, so that everything is brought together tightly while the glue sets. Staples are unlikely to penetrate inch-thick carvel planking to reach the ribs.
Peter.

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[PaulS]

The staples are used on the inside to tack the laminations to the shape of the hull and each other. You can then laminate several ribs before having to go outside to attach the laminated ribs permanently to the hull.

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[pirate]

THANKS FOR ALL REPLYS.
ANY ADVICE REGARDING USING EPOXY TO BOND LAMINATE , WHICH I HAVE
HEARD SOME NEGATIVE COMMENTS ABOUT WITH REGARDS TO THE JOINTS
DELAMINATING OR A GLUE SUCH AS RESORCINAL?

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[Spuddy]

I used the Bison polyurethane glue for patching up some of an old chine boat because it was single pot and easy to use. For more critical structural use I'd go for epoxy and be scrupulous about working conditions - should be stronger and more durable than the timber.
good luck spuddy

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[Peterduck]

Obviously all faying surfaces should be clean, especially free of any oily substances. I use a plastic serrated picnic knife which I buy from my supermarket to spread the glue. I get a nice even coating at about the right thickness. The proportions of the glue you should get from the tin, although I have always had trouble getting the measurement very accurate. I just do my best. I think that you'd have trouble getting the high clamping pressures on the joint that are required by resorcinol. If you were laminating on a bench, as in original construction, then you could use lots of clamps and get it right. but I don't think that this is the case here. If you are going to do it at this time of the year [assuming that you're in Britain] you'd need to find some way of keeping the job warm so that the resin would cure.
Peter.

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[pelorus32]

I've got a personal dislike of epoxy - I love resorcinol - the glue made in heaven. However Peter is right, clamping pressure is critical for resorcinol bonding and you're not going to get that reliably with rivetted frames. Peter is also right about keeping the baby warm. Temperature is critical to a good bond.

Regards

Mike

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[mikesharp]

If you do use epoxy, remember that you must not squeeze out all of the filler between the laminates or it will fail in the future.

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