Turn Those Chain Plate Bolts!

Do you have problems with your shroud turnbuckle T bolts or toggles binding or bending when you step your mast? If so, your chain plate bolts might not be rotated at the right angle for those parts to work the way they’re supposed to.

Most trailerable sailboats have internal chain plates as opposed to external chain plates. Internal chain plates are inboard of the hull and usually visible inside the cabin. On the C-22, they bolt to the forward bulkheads and the deck, which transfer the loads from the shrouds to the hull liner that’s bonded to the hull. External chain plates bolt directly to the outside of the hull.

It’s all about the mast

A common problem with trailerable sailboats is the chain plate bolts are misaligned. They might be rotated at random angles because the owner is unaware that the angles matter. Or they might be rotated with their tabs parallel to the boat’s centerline because the owner thinks that the toggles need to rotate from aft to forward when they lower the mast. They shouldn’t look like in the picture above.

Notice how the toggles angle outward but the turnbuckles angle inward? That’s not a good thing. What do you suppose will happen as the shrouds pull harder and harder on the chain plates? The toggles will bend inward. The upper shroud turnbuckle in the middle of the picture is already bent, probably because it has no toggle at all.

This wrong thinking is reinforced by the Catalina 22 Owner’s Manual and General Handbook, which contains the following statement about the upper and aft lower shrouds:

The turnbuckles must not be completely tightened, however, because slack is needed in the shrouds to enable the mast to be fully raised

That is true if the chain plate bolts are misaligned. Assuming a mast was properly tuned when it was lowered, you won’t be able to raise the mast completely without either loosening the turnbuckles or bending the toggles or T bolts. That’s not necessary if you rotate the chain plate bolts properly. That is, with the chain plate tabs pointing at the mast like in the following picture.

Rotate chain plate bolts toward the mast for proper loading
Rotate chain plate bolts toward the mast for proper loading

This keeps the turnbuckle toggles inline with the shrouds and allows them to rotate on their clevis pins when the shrouds flex slightly with the mast under sail. At any other rotation, the shrouds cannot pivot entirely on the pins. Instead, they will pry sideways on the toggles and T bolts to a greater or lesser degree depending on their orientation and they can bend either while stepping the mast or while under sail like in the following picture.

Bent toggle and T bolt from improperly aligned chain plate bolts
Bent toggle and T bolt from improperly aligned chain plate bolts

Have your mast and step it too

This seems counter-intuitive for stepping the mast. If you rotate the chain plate tabs parallel to the boat center line, that does let the toggles rotate naturally while raising the mast but the toggles wind up misaligned for sailing. The toggles are under considerable loads while you’re sailing but not much at all while you’re raising the mast.

Plus, with the toggles aligned properly, the T bolts can rotate instead during raising until everything lines up. That’s why there are toggles on the ends of the turnbuckles to begin with. It’s also why the turnbuckles don’t attach directly to the chain plate bolts like the upper shroud in the picture above that’s missing a toggle. Together, the toggles and T bolts act like a universal joint on a car drive shaft. They’re there for a reason, use them.

Here’s a brief video that shows what I mean.

When we first got Summer Dance, the chain plate bolts were rotated at random angles and several of the toggles and T bolts were bent and I had to replace them. After rotating the chain plate bolts like I’ve described here, I haven’t bent a single toggle or T bolt after dozens of raisings.

Before you raise your mast again, consider turning those chain plate bolts. Here’s how:

  1. Have a helper loosen the nut on the inside of the cabin while you hold the bolt stationary with an adjustable wrench on deck. (Tip: If you haven’t rebedded the bolts in a very long time or never have, this is a good time to do so and avoid unseen water leakage into your deck core. If the core gets wet and rots, the chain plate bolt could pull through the deck.)
  2. Rotate the tab so that it is pointing at the mast step and then have your helper tighten the nut again.
  3. Make sure all the turnbuckles and shrouds are laying aft of the chain plate bolts.
  4. Raise the mast. For an easy way to do this, see How to Step a Mast Single-Handed With or Without Using the Boom as a Gin Pole.
  5. Check all the shrouds for proper tension with a Loos gauge and adjust as necessary until the mast is in tune for the type of sailing you enjoy. For tips on mast tuning, see Product Review: Loos Tension Gauge.

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5 Comments Add yours

  1. Howard Miller says:

    I’m in the middle of this project now on my 1978 C22. Got the old chain plates out and they had a little rust on them but nothing serious and no wood rot. I’m debating the upgrade to the larger chain plates but can’t see paying $177 for parts I don’t need. I have the backing plates and nuts/bolts. I just want the upgraded chain plate. Do you have any suggestions?

    1. Unless you plan to race seriously or go offshore, I wouldn’t make the upgrade a high priority. Those are the kinds of conditions where the 3/8″ bolts were found to be insufficient. For the average day sailor or weekend cruiser, they’re fine and not the weakest link in the rigging. But if you want to upgrade anyway, look at eBay where you can get them for about half the price of that popular online Catalina parts retailer. There’s several sets listed right now.

  2. Howard Miller says:

    Thanks for the advice. It makes sense that it’s really not worth the effort. The boat is 39 years old and the originals just needed to be re-aligned.

  3. David T says:

    I have this exact problem on my newly acquired 1985 Oday 23. The T-bolts are bent and when I compared the chain plate positioning with yours they were the other direction. My problem is I don’t think mine can be turned. I will try and attach a pic of them but note i have plastered the deck side with duct tape for the winter as I try to protect a leak that needs further investigation. Obviously, I may have to remove these plates because of this. Note I am a novice at best with boat repair. Still learning and your site is super valuable to me.

  4. Richard Denston says:

    My 1st boat was a Buffalo Knockabout 22 ft . Turnbuckles were like pretzels and nev er knew why. Thanks


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