Backstay attachment point

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Subject: Backstay attachment point

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From: pat
Date: Wed, Feb 6, 2008 at 8:39 AM
To the mailing list

On Feb 5, 2008 11:18 PM, Bill Emberley wrote:
> Sent on Wednesday, February 6, 2008 at 05:18:21
>
>
> Name: Bill Emberley
> Email: billemberley@yahoo.com
> BoatName: Pearson 424, Running Tab
> Comment: I have a problem with my backstay. The stern has bowed inward at the bracket. The fiberglass is cracked at the bracket and there is an obvious flexing from the stress. Has anyone else experienced this problem? I have some ideas on strengthening the stern but would welcome any advise. So you know, I sail her pretty hard on and around the San Francisco Bay.
>
>

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From: Robert Fine
Date: Wed, Feb 6, 2008 at 9:06 AM
To the mailing list

Hi Bill,

I assume you have a sloop? I’ve read this is a problem, but so far haven’t seen it on a ketch (that’s all I looked at and I eventually bought one).

If you’re really talking about a transom mounted one, then the fix is relatively easy, if messy.

1. Unmount the backstay and the chainplate.

2. Get some 1/2 exterior plywood or marine plywood, cut it so that it fits below the transom and extends a foot or two in all directions from the chainplate. You can make it larger, but not smaller. You want to spread the forces as far as possible. I’d even consider doing the whole transom, but that’s a matter of choice.

3. Clean up the transom on the inside. Sand it for a few inches (4-6) past the board edge. Use a sanding disk of about 80 grit. This is the messy part. Make sure the boat is closed up. Tape up plastic inside to prevent dust from going into the bilge, steering gear and lazerettes. Really. You’ll appreciate this when you’re done.

4. Coat the reinforcing board with polyester to seal it. Since your hull is probably polyester, use that. It’s also cheaper. Make sure you don’t use the finishing stuff as it will form a wax surface. It should remain tacky.

5. Mix up some polyester and filler and spread liberally on aforementioned board. Put it in place and use whatever you have to jam it up against the transom and make the transom straight and fair again. You want a good seal and you want it to be well adhesed (is that a word?). Best if it’s so tight that the filler smooshes out the edges. In any case, fillet the edges so that it’s a smooth transition from the board to the transom.

6. More fun: Put a layer of mat over the board to about 2″ past the edge. Next put a layer of cloth or woven roving over that to about 4″ past the edge, and finish up if you like with either mat or cloth to the full 6″ past the board.

7. Because you probably don’t have smooth edges at the end of the final layer, sand the edges to make them nice.

8. Re-drill the holes for the chain plate. You really should do the whole over-drilling, filling with epoxy, and drill again, but you’re forgiven if you don’t. Just be sure you coat the inside of the re-drilled hole with polyester.

9. Replace the chainplate using 3M 5200. This is one item that you typically don’t want to remove. If you feel queasy about it, use 3M 4200 UV. It is much more easily removed.

10. Reattach the backstay and adjust to taste.

11. Go beat the crap out of it on the Bay.

Bob

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From: Rich Carter
Date: Wed, Feb 6, 2008 at 9:13 AM
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Bill
Yes, I’ve experienced the same problem. IMHO, Pearson didn’t adequately reinforce the transom to handle the load from the backstay. The chainplate is also a problem. Since it is basically a flat bar with a bend in it, there is no practical way to keep the plate from bending more. I tried adding a four inch thick plywood backing plate to the transom. This helped, but didn’t eliminate the problem.

One of my winter projects is to fix the backstay chainplate. I’m planning to remove the chainplate and replace it with a pair of larger stainless plates made from ‘L’ bracket stock. The plates will be back-to-back, making the pair of ‘L’s into a ‘T’. The larger size will better distribute the load and the L shape will give it some strength. I’ll straighten and repair the transom and glass in a pair of bulkheads under the aft combing. I’ll cut some plywood pieces to fit under the combing, shaped to match the shape of the coming and attach to the transom. They will be about a foot apart. The space between them will be reinforced with more wood and glass to take the load from the backstay.

The most difficult part of this job will be to remove the reinforcement that I already put in there. It is glued in place. Cutting and machining the stainless will also be a challenge. I have an early sloop. The main mast is the same length as the ketch rig. If things get straightened out, there isn’t much clearance between the backstay and the pushpit. The new chainplate needs to be made as short as possible to allow the backstay to clear the pushpit. This will require a longer backstay. The difference will be made up with a toggle. If you have a cutter or later model sloop, your geometry might be different.

I estimate that this is a one or two weekend project. I’ll take photos and write it up.

—
Rich Carter – BlackSheep #47

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From: Silver Heels
Date: Wed, Feb 6, 2008 at 9:18 AM
To the mailing list

Alternatively, you might consider installing new chainplates in transom corners and splitting your backstay. This will divide the per-contact-point stress in half, move it to brand new (i.e., not fatigued) locations on the hull and improve boarding access at the transom. Better still, install double backstays (which is what I have done), thereby providing a substantial additional safeguard against dismasting.

I’d still do something about the bowed transom, though.

Tor

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From: Rich Carter
Date: Thu, Feb 7, 2008 at 9:15 AM
To the mailing list

Bill
The boat was really designed to make use of a split-backstay. The transom just isn’t strong enough without modifications to handle the load of a backstay. Adding a simple backing plate is better than nothing, but is not sufficient. The real problem is that the transom rake is not in line with the backstay. The load is not vertical. You need something to distribute the load.

Splitting the backstay makes it impractical to add a backstay tensioner however. There are adjustment schemes that make use of a pulley arrangement that runs down the pair of backstays, but I’ve never seen one that is big enough to handle the loads of a 14 ton boat. Without having some way to tension your backstay, you’ll never get the boat to point. Adding a backstay tensioner may aggravate the problem, but you will likely see problems in the transom even if you keep your rigging slack. Running the boat into a pounding sea places pretty high dynamic loads on the rig and particularly the backstay.

Improving the sailing qualities of he 424 is not a priority with all of us. You’ll have to weigh your needs.
—
Rich Carter

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From: Robert Fine
Date: Thu, Feb 7, 2008 at 9:27 AM
To the mailing list

Split backstay or double backstay is definitely the way to go, but as far as special tensioners go, the mast is not a bendable one. I’d really be hesitant to adjust the backstay for different loadings. The only reason for doing that is to tighten the headstay or shape the mainsail. I don’t know about newer masts, but for the ’78, after the static adjustment, there is no ‘shaping’ the mast. It’d be like shaping a telephone pole.

So, one or the other, split or dual, but you might want pictures from a ketch to see how it was done for them and mimic it as much as possible for the sloop.

Bob
—

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From: Bill Emberley
Date: Thu, Feb 7, 2008 at 9:50 AM
To the mailing list

Thanks for the advise. I agree that the split
backstay offers many advantages. Trying to reinforce
an already distressed part of the hull is not at all
wise. We sail this boat hard to weather on the San
Francisco Bay so I want to rest assured that all is
sound. I have already replaced all the standing
rigging so what’s another step in the process. I’ll
send you photos when I get her rigged.
Bill Emberley
Pearson 424, “Running Tab”

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From: Rich Carter
Date: Thu, Feb 7, 2008 at 10:59 AM
To the mailing list

Bob
To my knowledge, there is nothing special about the 424 mast. It will bend just like any other mast. The next time you have your mast down for service, sight down the length of the mast when it is sitting on sawhorses. You’d be surprised how much sag there is just from the weight of the mast. You don’t need very much bend in order to flatten the rig. If you can’t take the sag out of the headstay, you’ll never get the boat to point.

I need about 3500 lbs of tension in the backstay to flatten the main and gennoa in a moderate breeze. There is a limit to what you can do with the boat given the short rig and wide sheet angles. With decent sails and proper sail trim, the boat will point as well as most cruising boats. I have no problem tacking inside 90 degrees. You can’t get this kind of tension with the backstay turnbuckle. You’ll gall the threads.

If you have a ketch rig, I don’t think there is any practical way to tension the rig.

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From: Robert Fine
Date: Thu, Feb 7, 2008 at 11:59 AM
To the mailing list

Hi Rich,

You could do the split backstay tensioner for the ketch, but I do believe my mast is shorter than yours (48′ above the water) and it’s pretty much like a telephone pole. Sure, I could bend it. But not like my Ranger or Ericson.

I tack, with crappy sails, in about 95 degrees. Sure, I’d like less, but I’m also sailing by myself and leaping all over the cockpit because the winches are nowhere near anything.

Still, you’re very right about headstay tension. And I do tend to keep it tight.

Bob

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From: Rich Carter
Date: Thu, Feb 7, 2008 at 3:30 PM
To the mailing list

Sorry Bob
I must sound argumentative, and I don’t mean to. That’s the trouble with email.

We have the same rig. My main mast is exactly the same as yours. I even have the support beam and bulkheads glassed in for the mizzen mast. For some reason, the original owner decided to omit the mizzen mast when he purchased the boat. I’ve considered adding the mizzen a few times, but there are trade-offs with that. I’ll stick with the rig she has. If I had the option of changing anything, I’d go with the cutter rig.

I know that we all know how to sail and some of us are probably pretty good at it. I’m probably the only one who is stupid enough to race the thing. It sometimes feels like I’m racing a greyhound bus against a lot of greyhounds. In comparison to the fin-keel ultra-lights, the boat is barely maneuverable and takes forever to get back up to speed after tacking. After racing the boat for about 12 years, I’ve learned a few things. In light air, I can sail abeam of a windward mark up to the point where the mark is directly off my beam. Tack over, and clear the mark. Before working on the sailing qualities of my boat, I’d have to sail well past the 90 deg rhumb line before tacking over. An honest 110 degrees might be bragging.

There are a lot of things I like about the 424, but sailing performance isn’t one of them. It will get you from point-A to point-B in comfort and safety, but it won’t point. Not being able to point while cruising may be annoying. For some of us, it probably isn’t a big deal. When racing however, if you can’t point, you are dog-meat. The other boats will get to leward of you and luff you. As I’m sure we all know, two sailboats going in the same direction are always racing.

The 424 has a reputation for being a dog. While I’ll have to agree that the boat isn’t particularly fast, there are a lot of simple things that can be done to bring her sailing qualities up to mediocre. Here’s what I recommend in the order of importance. This is probably in the order of cost too, with the most expensive being first.

1 – Folding or feathering prop
2 – Decent suit of sails
3 – Spinnaker of some type
4 – Backstay adjuster

If you do all these things, you’ll probably get about a knot. This means getting to port in 5 hours instead of 6, or sailing instead of motorsailing.

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From: “Robert Fine”
To the mailing list
– Show quoted text –
Date: Thu, 7 Feb 2008 16:59:43 +0000
Subject: Re: [pearson424] Backstay attachment point
Hi Rich,

You could do the split backstay tensioner for the ketch, but I do believe my mast is shorter than yours (48′ above the water) and it’s pretty much like a telephone pole. Sure, I could bend it. But not like my Ranger or Ericson.

I tack, with crappy sails, in about 95 degrees. Sure, I’d like less, but I’m also sailing by myself and leaping all over the cockpit because the winches are nowhere near anything.

Still, you’re very right about headstay tension. And I do tend to keep it tight.

Bob

On Feb 7, 2008 10:59 AM, Rich Carter wrote:

Bob
To my knowledge, there is nothing special about the 424 mast. It will bend just like any other mast. The next time you have your mast down for service, sight down the length of the mast when it is sitting on sawhorses. You’d be surprised how much sag there is just from the weight of the mast. You don’t need very much bend in order to flatten the rig. If you can’t take the sag out of the headstay, you’ll never get the boat to point.

I need about 3500 lbs of tension in the backstay to flatten the main and gennoa in a moderate breeze. There is a limit to what you can do with the boat given the short rig and wide sheet angles. With decent sails and proper sail trim, the boat will point as well as most cruising boats. I have no problem tacking inside 90 degrees. You can’t get this kind of tension with the backstay turnbuckle. You’ll gall the threads.

If you have a ketch rig, I don’t think there is any practical way to tension the rig.

—
Rich Carter

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From: Robert Fine
Date: Thu, Feb 7, 2008 at 5:54 PM
To the mailing list

Hi Rich,

I defer to your knowledge – You’re not being argumentative at all – I really thought you had a sloop – they did have taller masts.

Leave the mizzen off. It won’t help your pointing. It’s great when the wind pipes up to sail with instead of the main, and off the wind with all sails (including my staysail) the boat thunders through the water.

I agree with all your suggestions, although if I were racing, (which I did for a lot of years), I’d figure a way to get the jib in closer and flatter, have loose-footed sails so I can really adjust the draft, and bring the jib clew much closer to the deck (currently somewhere near the constellation Orion).

But never worry about arguments! We all have our own opinions. It’s like fishing lures.

Bob

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From: Walter Piescik
Date: Thu, Feb 7, 2008 at 8:03 PM
To the mailing list

You guys are giving me hope. I don’t think I have ever tacked through less than 95 degrees. But I have had used sails as long as I have owned the boat. The headsail was the best so I replaced the other two.

I am buying a new headsail this year. I am looking forward to better, flatter windward ability.

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[quent]

Bill-
We had the same issue on our 1981 sloop. We had a fiberglass guy here in Annapolis repair it. After removing the backstay and chainplate, He heated the transom with a propane space heater from inside until the transom was hot to the touch on the outside, then jacked the transom back in place with a hydraulic jack. When it cooled, the transom was back in the original position without cracking the laminate or gellcoat. He then reenforced the inside of the transom with more laminate, alternating mat and roven roving totalling about 3/8″ at the chainplate location, tapering to one layer at the edges. The patch covered approximately the center upper half of the transom. The thickest part of the patch (the top) also continued around the hull inside flange wher it attached to the deck. This part provides additional rigidity to the transom at the chainplate. It is important that the repair be tapered to avoid creating a hard edge and stress riser where the repair meets the original structure. We have had no further problems. Also important, the marine surveyor who looked at the boat agreed that it was properly fixed.

A bit about the chainplate. Ours was close to failure. It had cracked through one side of the top bolt hole. In my opinion, Pearson’s use of flat head fasteners and the required beveled hole is inappropriate. It removes even more metal at the weakest point of the chainplate. We used hex head cap screws on the replacement chainplate, and did not bevel the holes. I think that it is prudent to remove and examine the chainplates and fasteners periodically. We do not bed the backstay chainplate as this would prevent oxygen from reaching the stainless steel.

Regarding stainless steel, the original chainplates were probably type 302 or 304, the most common type. This is known as Austinetic stainless, and has a high chromium content. There is a myth that type 316, also Austinitic but with some other stuff to make it more resistent to surface corrosion, is a “marine” metal. In fact, while it might stay pretty longer, it is just as subject to failure as the others, and has 10% less tensile strength. The problem in a nutshell, is stress corrosion cracking. Given the right combination of warm tenperatures, salt water, and cyclic stress, the metal will corrode along the grain structure and fail well below its rated strength. There is another stainless steel called Duplex which is basically a mixture of two different grain structures that does not have this problem.

Moving the backstay chainplates to the corners sounds like a pretty good idea. I can’t do it because we have too much stuff in that part or the hull to allow easy access. If I did, I’d add a second backstay of the same specs as the original and run one to each corner of the transom. If each part of the backstay can’t carry the entire load, then you just increase the risk of failure by adding more parts.

Best regards,
Quent Kinderman
Clairebuoyant #132

[Anonymous]

Quent,
Thanks so much for your insight into this issue. This is obviously a design flaw that I could have serious consequences on the open sea. I think that heating the stern to re-shape is genius. I have hired a rigger to install a split back stay to distribute the load to the outside and will repair the buckled transom with lots of new fiberglass. I will update you on the results.
Bill Emberley
Running Tab #86

quent <> wrote:

Bill-
We had the same issue on our 1981 sloop. We had a fiberglass guy here in Annapolis repair it. After removing the backstay and chainplate, He heated the transom with a propane space heater from inside until the transom was hot to the touch on the outside, then jacked the transom back in place with a hydraulic jack. When it cooled, the transom was back in the original position without cracking the laminate or gellcoat. He then reenforced the inside of the transom with more laminate, alternating mat and roven roving totalling about 3/8″ at the chainplate location, tapering to one layer at the edges. The patch covered approximately the center upper half of the transom. The thickest part of the patch (the top) also continued around the hull inside flange wher it attached to the deck. This part provides additional rigidity to the transom at the chainplate. It is important that the repair be tapered to avoid creating a hard edge and stress riser where the repair meets the original structure. We have had no further problems. Also important, the marine surveyor who looked at the boat agreed that it was properly fixed.

A bit about the chainplate. Ours was close to failure. It had cracked through one side of the top bolt hole. In my opinion, Pearson’s use of flat head fasteners and the required beveled hole is inappropriate. It removes even more metal at the weakest point of the chainplate. We used hex head cap screws on the replacement chainplate, and did not bevel the holes. I think that it is prudent to remove and examine the chainplates and fasteners periodically. We do not bed the backstay chainplate as this would prevent oxygen from reaching the stainless steel.

Regarding stainless steel, the original chainplates were probably type 302 or 304, the most common type. This is known as Austinetic stainless, and has a high chromium content. There is a myth that type 316, also Austinitic but with some other stuff to make it more resistent to surface corrosion, is a “marine” metal. In fact, while it might stay pretty longer, it is just as subject to failure as the others, and has 10% less tensile strength. The problem in a nutshell, is stress corrosion cracking. Given the right combination of warm tenperatures, salt water, and cyclic stress, the metal will corrode along the grain structure and fail well below its rated strength. There is another stainless steel called Duplex which is basically a mixture of two different grain structures that does not have this problem.

Moving the backstay chainplates to the corners sounds like a pretty good idea. I can’t do it because we have too much stuff in that part or the hull to allow easy access. If I did, I’d add a second backstay of the same specs as the original and run one to each corner of the transom. If each part of the backstay can’t carry the entire load, then you just increase the risk of failure by adding more parts.

Best regards,
Quent Kinderman
Clairebuoyant #132

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