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Potential boom defect: Sheave shaft dislodged

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TakeFive
Master Marine Consultant

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2272 Posts

Initially Posted - 07/18/2010 : 13:38:46

[EDIT: Judging by the deafening silence in response to this thread, I assume that nobody else has had this problem - which is a good thing. However, I think it highlights an important potential defect in the sheave shaft. So I will continue to respond to my own messages with the description of my solution to this problem.]

Today while sailing we noticed a few things amiss in our rig. The nylon line part of the outhaul was starting to dangle from the boom, topping line suddenly went looser than normal, etc. We had pretty nice breezes, so I made adjustments on the fly to get back to the marina. But afterwards I inspected things and found what I had feared: the sheave at the front of the boom is gone. I could stick my finger in the bottom of the boom and feel the sockets on each side of the boom where the ends of the shaft are supposed to be, but no shaft and no sheaves.

Before I remove the sail and boom and disassemble things, I was hoping some of you might have some advice on the work that I will have to do to repair this thing. How does the shaft get into/out of those sockets? Is the shaft a spring-loaded thing like a toilet paper holder, or do the sockets slide out of the boom and slide back in with the shaft in place? Is the shaft likely broken or bent, or did it probably just slip out somehow and I'll find it sitting in the boom somewhere? Are the sheaves likely to be inside there and reusable, or are there ball bearings or other small parts that might have gone missing? Are these generic parts that I can find at West Marine or some other supplier, or do I have to go to Catalina for them?

Any experience you can share can allow me to be prepared ahead of time so that my boat is out of commission for the shortest time possible.

Also, are there any recommendations for this upgrade?

http://www.catalinadirect.com/index.cfm?fuseaction=product.display& product_ID=1621

Rick S., Swarthmore, PA
PO of Take Five, 1998 Catalina 250WK #348 (relocated to Baltimore's Inner Harbor)
New owner of 2001 Catalina 34MkII #1535 Breakin' Away (at Rock Hall Landing Marina)

Edited by - TakeFive on 07/22/2010 20:04:09

TakeFive
Master Marine Consultant

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2272 Posts

Response Posted - 07/21/2010 : 20:45:17

I removed the sail and boom today and brought it home for inspection. The sheaves and shaft were lodged diagonally about a foot aft in the boom. I have pics to post, but no time right now. I pulled it all out, cleaned it up, and inspected it. The shaft is about 1/8" shorter than the full width of the gooseneck casting. From the wear patterns around the shaft holes, it appears that the shaft was just short enough to work its way out of the holes. I have pictures of all this that I will post later.

My solution will be to replace the shaft with one that is slightly longer. Do any of you know where I can get some 1/4" dia. stainless stock? I dropped by Home Depot tonight, and they only had mild steel, zinc coated, and aluminum - no stainless.

Also the sheaves themselves were a little worn on their sides - possibly from friction due to the shaft being s little diagonal as it was working loose. Any suggestions on replacements?

Finally, I noticed that my sheaves at the end of the boom are different sized. The one on port for the reef is appropriately sized for a 5/16" line. But the one for the topping lift seems very small for the 1/4" line that is there presently.

Pat Moseley's picture seems to show that the topping lift is narrower line - perhaps 3/16":

What size line do all of you have for your topping lifts? Is it 1/4" like mine, or something smaller. I've had problems with lines popping out of these sheaves, and this might explain why.

Edited by - on

pem
Deckhand

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USA
6 Posts

Response Posted - 07/22/2010 : 08:17:43

I ordered an owner's manual from Catalina after I purchased by 1999 WK since the boat did not come with it. In the owner's manual, it lists the topping lift line should be 1/4" low stretch line. I have not measured what the line is on mine to make sure it is 1/4", but I will try to remember to do that the next time I am out at the boat. I have had problems with the topping lift line engaging in the clam cleat on the boom. When I bought the boat, the boom had dropped to the point where the bimini would hit the topping lift line, and when I tightened it up, I ended up using the cleat that was installed for the lazy-jacks to cleat off the topping lift since the clam cleat would not hold the line.

Edited by - on

TakeFive
Master Marine Consultant

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2272 Posts

Response Posted - 07/22/2010 : 19:04:25

I did the fix today, and had time to edit and upload some pictures.

The sheaves and shaft were lodged diagonally about a foot aft in the boom:

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</center>

The spacers were bent from being diagonally oriented (but I was able to straighten them out later):

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</center>

The shaft is about 1/8" shorter than the full width of the gooseneck casting:

<center>

</center>

There was a wear pattern around one hole that caused it to be elongated like an Easter egg:

<center>

</center>

This is pretty strong evidence that the shaft had worked its way over to one side, and was barely hanging on by its very tip. This might have continued for years. Eventually, under the stresses of a hard blow and frequent jibing (which we had last Sunday), it gave way. Perhaps there was a little flexing from the sides of the boom extrusion that caused the shaft to finally come loose.

I could not find 1/4" SS stock, but I did find a 4" hex cap screw, so I cut off the head and threads leaving a rod of the appropriate length - the FULL WIDTH of the boom casting. With the new shaft cut to this length, the Easter egg shape of the hole does not matter, since the deeper part of the hole is perfectly round. I filed down the burr that had developed since it was interfering with the new sheaves. I found the ball bearing sheaves shown in the CatalinaDirect link above (Harken #160) at WM for about $8 each, so I bought them and used a $10 off coupon. Everything is back together again, and works more smoothly than it ever did before. As usual, it took longer to accumulate the needed materials than it did to actually do the work.

I am concerned that this is a potential defect that may lurk undetected in other boats. I do not want to instill any sense of panic, but I would suggest that if you have occasion to disassemble your boom for other reasons, you may want to check out your shaft to make sure you do not have this problem.

Edited by - TakeFive on 07/22/2010 20:05:35

Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Response Posted - 07/23/2010 : 06:00:01

This is the first instance of this problem that I can recall reported to the forum. It is one of those out of sight out of mind things that can't be foreseen. Glad you have it fixed.

Edited by - on

Dan Lamb
1st Mate

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USA
26 Posts

Response Posted - 07/23/2010 : 07:51:00

Rhythm Doctor you have my appreciation for taking one for the team. You have exemplified why this is such a great web site. You found a problem, found the solution and documented everything exceptionally well. Thanks for posting this so everyone else can benefit and perhaps prevent a serious problem on the water.

Edited by - on

pa-sailor
1st Mate

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USA
67 Posts

Response Posted - 07/23/2010 : 15:12:18

Sorry to hear about your sheave problems Rick, looking forward to meeting you in August

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frog0911
Master Marine Consultant

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USA
1349 Posts

Response Posted - 07/23/2010 : 17:56:18

Rick you got my attention so I went out and look at my setup. I have three sheaves in the aft end of my boom. The one forward is for the wire outhaul and the two aft are for reef and topping. My aft two sheaves are held in by a 1/4" clevis pin with a ring safety pin. I don't know when Catalina made the change from press fit to cleaves pin, but that is probably why this has not come up before. Maybe some others with older models can check theirs and report so we can get a year for the change.

Edited by - on

TakeFive
Master Marine Consultant

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2272 Posts

Response Posted - 07/23/2010 : 19:04:23

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by frog0911
 Rick you got my attention so I went out and look at my setup. I have three sheaves in the aft end of my boom. The one forward is for the wire outhaul and the two aft are for reef and topping. My aft two sheaves are held in by a 1/4" clevis pin with a ring safety pin. I don't know when Catalina made the change from press fit to cleaves pin, but that is probably why this has not come up before. Maybe some others with older models can check theirs and report so we can get a year for the change.
<hr height="1" noshade id="quote"></blockquote id="quote">
I think my "thread drift" might have confused you. The problem with the shaft dislodging happened at the front of the boom, inside the gooseneck casting. That shaft is a 1/4" rod held in place by insertion of the casting into the aluminum extrusion.

The sheaves at the aft end of my boom are exactly as you described - and the sheaves for topping and reef are held in place by a clevis pin with safety ring, as you described. So I don't think any design change was made. I did not have any failure at this end of the boom, although I did ask an unrelated question about the sizing of the topping sheave vs. the topping lift line because I do occasionally have problems with fouling of these lines.

Edited by - TakeFive on 07/23/2010 19:07:44

frog0911
Master Marine Consultant

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1349 Posts

Response Posted - 07/24/2010 : 09:23:59

I did check the goose-neck casting also and all looked good. I would have to remove the casting to really know for sure. I have three sheaves there also for the reef, topping and outhaul. I think that is what confused me since you only showed two sheaves not three and the only place I could look square at and see just two was the aft end.

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