Transom Chain Plate

[steve62]

Hi All,

I am after a bit of feedback on a problem I have on my boat.

The boat is a Mirage 26 and I have noticed that the back stay has pulled the deck moulding away from the hull moulding where a couple of the original rivets have failed. The deck has not cracked as there is a reinforcement plate glassed into underside of the deck, but it has lifted and separated for about 3 inches.

Rather than move or repair the U bolt holding the backstay, I am contemplating installing a chain plate on the transom instead. My idea is to use a piece of 316 Stainless about 300mm x 30mm x 6mm that I have and put three bolts through the transom and then connect the back stay to this. The Mirage transom slopes away from the deck so my chain plate will almost be in line with the back stay so eliminating bending forces.

Does this seem a feasible plan or am I setting myself up for trouble later?

Thanks

 

[anoccasionalyachtsman]

Sounds exactly right to me, the only caveat being the thickness of the transom. On a modern boat that would probably need more glass if it hadn't been designed to take that load locally, but on a Mirage I think you'll be fine. I'd want to see about 6mm when I drilled the holes.

 

[Lodesman77]

Exactly the arrangement I have as standard on my Stag 28. You may find that you need to bend it slightly as it comes above the transom to get the angle to the backstay just right..

Second picture of another stag transom: Stag 28, preowned sailboat for sale in (Great Britain)

 

[Rappey]

How about getting a right angled bracket made ,bolting it under the deck and down the inside of the transom ?

 

[Tim Good]

When I was making a chainplate for a series drogue I was reliably told that to ensure the bolts are independent from one another in terms of the stresses on the GRP, they should be 120mm apart.

I think that’s OTT but since it was to take enormous forces that are possible with a JSD then I stuck with the advice and did just that.

 

[alahol2]

Exactly the arrangement I have as standard on my Stag 28. You may find that you need to bend it slightly as it comes above the transom to get the angle to the backstay just right..

Just to add, on the Stag there is a glassed in hardwood pad (which also supports the transom hung rudder) inside the hull; about 20mm thick. The strap is held with 5 bolts at about 80mm spacing.

 

[steve62]

Thanks Gents,

Yes, I will check the thickness of the transom but suspect it will be ok and I will probably add a plywood pad on the inside of the transom. The current arrangement is a 10mm U bolt with a metal plate under the deck and I am proposing a minimum of three 10 mm bolts through the transom.

 

[anoccasionalyachtsman]

I know everyone suggests ply pads, but I use a grp plate on epoxy filler. It won't rot or crush (under sensible compression) and holes are much less likely to elongate. Use lock washers or Loctite and it's belt and braces.

 

[Spirit (of Glenans)]

I had a UFO27 which had been built with just such an arrangement.