Replacing Aft Chain Plate

[Kevin]

I am replacing the aft chain plate on my ’83 Passport 40 (#45) and have a few questions from the folks out there who have some experience with the same project.  First, some background:

 

The aft chain plate is a single, stainless steel bar with a slight bend at the top where it goes through the toe rail.  Below decks it bolts through the stern in three places.  There is a glassed in reinforcement on the inside of the stern running vertically through which the chain plate is bolted.

 

I realized that there was a problem when the rust stains started appearing on the stern from around the bolt heads.  Then on the inside of the stern.  The one of the bolts became loose enough to spin by hand.  Not pretty.

 

The nuts had to be cut off.  We cut out a piece of the glass over the reinforcement and water (black) drained out.  Inside were the remainders of wood.  See attached pic.  Yes, someone had glasses a piece of wood, about 4” x 18” x ¼” onto the inside of the stern and bolted the chain plate through it.  I can find no other supports for the chain plate in the stern.

 

So that brings me to today.  I’ll remove the rest of the glass and wood on the inside of the stern.  Then I need to decide how to put it back together.  My first though is to have a “T” of stainless made to fit onto the inside of the stern, the vertical part of the “T” running vertically in the center of the stern, and glass is in.  Bolt the chain plate through the “T”.

 

Anyone dealt with a similar problem and come up with an elegant solution?

 

Thanks,

 

Kevin Muilman

Casi Cielo

1983 P40

[psherwood]

I don't think my solution was elegant, but it seems to have worked so
far (about 10 yrs). I just left the old chainplate in place, bedded into
the transom, and used the same bolt holes (with new fasteners) to attach
the new chainplate to the exterior of the transom. It wasn't hard to
take the correct angle off the old chainplate and have the new one bent
to the same angle. Had to notch the toe rail on its aft edge for the new
chainplate, which is 3/16" (I think) 316L stainless, water-jet cut and
drilled.

I thought I had a photo or two of it but can't seem to find them right
now. Will look further.

Not totally stock, true, thus not an ideal approach for a purist. So
far, so good.

Phil
s/v Cynosure
San Carlos

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[Bill Schmidt]

You guys are missing the best part! We replaced the chain plate on Wind
Witch after it became obvious that the plate was bending forward and, in
doing so was pulling the stern caprail upward and forward. A large
horizontal crack across the stern opened about 1/2". Why would it do
that you ask. It was because beneath the caprail at the transom
extending laterally about 6" on each side is a flat bar which is welded
to the chainplate just at the bend. The chainplate, bolted through the
transom as you describe, is (or was) backed by a common steel plate
embedded in the fiberglass. When we exposed this mess, the plate was
completely rotted away (thank you Wendell Rankin for being such a
cheapskate). With no backing plate the chain plate was unsupported
except for the fiberglass.
We completely replaced the chainplate with a bent "T" bar which
passed through a similar horizontal plate, but the aft end of the plate
protrudes out beyond the transom fiberglass, then is bent down,
capturing the upper edge of the transom like a clamp. The flat plate and
the chainplate are welded together at their junction. The first transom
bolt passes first through this bent plate, then the transom, then the
chainplate and lastly through a STAINLESS steel backing plate to the
nut. This stainless backing plate extends down to each of the other
bolts. There are 4 such in total.
BTW, all the backing plates for the stern ladder were also gone.
Such great craftsmanship I do believe.
Billy Manana

[Jeff and Jane Woodward]

 

 

Hi Kevin,

We did quite a bit of work to our backstay chain plate back in 2006.  Here's the thumbnail sketch:

• The chainplate was glassed to the transom.  We ground the glass off to remove the chainplate for inspection.
• We had some water intrusion at the through bolts similar to what you have described.   To fix that we over size drilled the holes from the inside of the transom after the chainplate was removed.  We were careful not to penetrate the skin of the hull in order to not damage the gelcoat finish of the exterior hull.  We filled the cavity with thickened epoxy.  Once cured the epoxy ensured there was no compression damage when the through bolts were tightened, and any future water intrusion  would not migrate into the hull core material.  When we replaced the chainplate we bedded the bolts with 5200.
• Both our shipwright and our surveyor were critical of the way the chainplate was mounted.  The load of the backstay on the chainplate was creating a moment force.  Because of the slant of the transom, the force carried by the backstay was not in line with the chainplate.  To make matters worse, the top bolt on the chainplate was several inches down from where the wire attaches to the chain plate. This made the chainplate want to flex forward.  Our remedy was to cut away a section of the cap rail where the chainplate penetrates it.  We removed a section about 2 or 3 inches by 3 or 4 inches.  This was done in order to make room for a block of G-10 of the same dimensions.  The G-10 is stronger than wood and so is able to stabilize the end of the chainplate much better than wood.  We through bolted the G-10 in each of the four corners.  In addition to the block of G-10, we further supported the end of the backstay chainplate with a formed piece of 1/8" thick piece of stainless steel.  That is shown in the photo attached to this email.  In addition to the two 1/4" - 20 tpi machine screws shown in photo, there are two more that run from aft forward.  You will also note that we ran a bead of weld around the top of the chainplate fixing it to the formed chainplate cover.  This completed fixing the top of the chainplate from movement, additionally it closed off one more avenue of water intrusion around the chainplate.  The chainplate and chainplate cover were bedded with a Dow-Corning product developed for bedding auto windshields.

I hope this is helpful.

Jeff

Adagio, P-40 #109, 1986

San Carlos, Sonora, Mexico

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Date: Tue, 24 Nov 2015 14:06:44 -0800
From: casic...@gmail.com
To: Passpor...@googlegroups.com
Subject: [Passport] Replacing Aft Chain Plate

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[Lou mcFadden]

Kevin, i have a 1986 37'.  I had a lot of rust (or whatever) draining out of the bolt holes on the interior side of transom, especially the bottom couple of bolt holes.  A yard's bill for cutting out old plate etc. would be too expensive for me.  So I had another chainplate made, and I added a fourth bolt hole to the topside end of the plate, then used the same existing three bolt holes and refastened the new chainplate to the outside of transom...and I could do that very easily in one hour while on the hard for the cost of the plate and a few bolts.  My guesstimate for a yard job in Annapolis or Newport for replacing in original condition would be $3,000.  I can send pic of finish job if you like.

Lou McFadden

s/v Black Prince

Passport 37' hull# 14

Sent from Lou's iPad

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<Stern Reinforcement.JPG>