The rigging chainplates are fastened through fiberglas hat frames into backing plates in Alden Challengers, Mistrals, Zephyr's and perhaps the Caravelles. There is other information on this problem on the website. This thread will be mostly photos of a repair on CHRISTMAS, a 1961 Challenger yawl.
The problem is in the backing plates that were used. Halmatic-GB, the yard that laid up the glass hulls and decks, used mild steel backing plates instead of Stainless Steel.
The hat frames are fiberglass structural girders designed and built to anchor and spread the load of the chainplates, to the hulls.
Photo below - Typical-small mizzen hat frame 1960: Trapazoid in shape with a large end at the deck; they taper and disappear, or join a typical 'frame' that was built of fiberglass.
Alden's design office, 15 to 20 years ago, told me they were unaware the Halmatic was using mild steel instead of SS. That is conceivable: The hat frames were hand laid around an aluminum former which was pulled - from above - once the glass had cured.
Then the solid glass decks were fitted and fastened to the hulls, all the joins glassed, sealing the backing plates inside. The idea was likely that these tombs would never see water so why not mild steel? Because water always finds a way in.
I've replaced a couple on Xmas over the years. The accepted process is pretty easy: Cut into the hat frame from the side, pull the old rusted plate out. Typical cut and grind on a Mistral :
And a typical layup repair on a Challenger(unknown which):
This is the worst Challenger backing plate failure I've seen: It was behind the head furniture and ceiling (Xmas):
It's also the only hat frame on Challengers (I believe), that isn't backed up to a bulkhead. Close inspection revealed the backing plate rusted and expanded inside the bottom of the hat frame, splitting the glass structure from inside. A first cut into the hat frame:
The swollen backing plate (4x's it's original thickness) had actually bent under the rigging load. It was clear I would have to cut most of the hat frame away and grind the damaged glass hat frame layers that are adhered to the hull structure which was not damaged and very thick.
I was able to save the upper third (scarfed with a grinder 8-10 to 1) of the hat frame as a form to start a new structure. I cut a wood former to form the trapazoid shaped hat frame.
The top of this hat frame is roughly 5" across the hull, has 30 degree tapered sides. It comes out from the hull roughly 3" and ends with a 1 3/4" flat, room to spare for the new 1 1/2" backing plate, yet to come).
The form, wrapped in plastic, in place to start the lay up:
With a first layer of 10 ounce fiberglass cloth forming an open frame - with one side left open to insert the new backing plate:
The fabricator took the old chainplate and my measurements and did this: Cut the two pieces of Stainless steel to my lengths, tacked welded them together, drilled through each (at the spots on the old chainplate) with the tap sized bit (3/8" thread), split the pieces. Then he tapped the threads into the backing plate and cut a proper clearance hole in the chain plate for the new 3/8" bolts.
I pulled the temporary form, hung the old chain plate through the deck at the original location, marked the first layer of the new hat frame, and drilled the holes. Then I fit the new backing plate inside to test with the new chainplate. Satisfied, sanded the new backing plate mating surface and spot epoxied in place. I also replaced a wooden former that closes off and starts the rib below.
Then another layer of 10 oz. cloth in epoxy to close and form the base of the new hat frame that extends to the frame below.
After a full cure it was sound to begin the layup of glass. The old hat frame was a 1/4" thick at the minimum. It takes a lot of cloth to build up a thickness of 1/4" . After a good cleaning and sanding to form a good bond, I started laying cloth on a Saturday.
I'm at the photo limit so will post this and continue below.
The problem is in the backing plates that were used. Halmatic-GB, the yard that laid up the glass hulls and decks, used mild steel backing plates instead of Stainless Steel.
The hat frames are fiberglass structural girders designed and built to anchor and spread the load of the chainplates, to the hulls.
Photo below - Typical-small mizzen hat frame 1960: Trapazoid in shape with a large end at the deck; they taper and disappear, or join a typical 'frame' that was built of fiberglass.
Alden's design office, 15 to 20 years ago, told me they were unaware the Halmatic was using mild steel instead of SS. That is conceivable: The hat frames were hand laid around an aluminum former which was pulled - from above - once the glass had cured.
Then the solid glass decks were fitted and fastened to the hulls, all the joins glassed, sealing the backing plates inside. The idea was likely that these tombs would never see water so why not mild steel? Because water always finds a way in.
I've replaced a couple on Xmas over the years. The accepted process is pretty easy: Cut into the hat frame from the side, pull the old rusted plate out. Typical cut and grind on a Mistral :
And a typical layup repair on a Challenger(unknown which):
This is the worst Challenger backing plate failure I've seen: It was behind the head furniture and ceiling (Xmas):
It's also the only hat frame on Challengers (I believe), that isn't backed up to a bulkhead. Close inspection revealed the backing plate rusted and expanded inside the bottom of the hat frame, splitting the glass structure from inside. A first cut into the hat frame:
The swollen backing plate (4x's it's original thickness) had actually bent under the rigging load. It was clear I would have to cut most of the hat frame away and grind the damaged glass hat frame layers that are adhered to the hull structure which was not damaged and very thick.
I was able to save the upper third (scarfed with a grinder 8-10 to 1) of the hat frame as a form to start a new structure. I cut a wood former to form the trapazoid shaped hat frame.
The top of this hat frame is roughly 5" across the hull, has 30 degree tapered sides. It comes out from the hull roughly 3" and ends with a 1 3/4" flat, room to spare for the new 1 1/2" backing plate, yet to come).
The form, wrapped in plastic, in place to start the lay up:
With a first layer of 10 ounce fiberglass cloth forming an open frame - with one side left open to insert the new backing plate:
I pulled the temporary form, hung the old chain plate through the deck at the original location, marked the first layer of the new hat frame, and drilled the holes. Then I fit the new backing plate inside to test with the new chainplate. Satisfied, sanded the new backing plate mating surface and spot epoxied in place. I also replaced a wooden former that closes off and starts the rib below.
Then another layer of 10 oz. cloth in epoxy to close and form the base of the new hat frame that extends to the frame below.
After a full cure it was sound to begin the layup of glass. The old hat frame was a 1/4" thick at the minimum. It takes a lot of cloth to build up a thickness of 1/4" . After a good cleaning and sanding to form a good bond, I started laying cloth on a Saturday.
I'm at the photo limit so will post this and continue below.