U-bolt "upgrade" from Catalina Direct for lower shrouds or not?

PSR

.
Sep 17, 2013
117
Catalina 27 4743 MB Yacht Harbor, Richmond CA
I am replacing the standing rigging on my C27 Surprise and while the mast is down, I have pulled the chainplates to inspect. My lower shroud "chainplates" are 1/2" eyebolts, similar to those offered now by Catalina Direct. These are 1/2" bolts with large backing plates, and therefore are more robust than the original 3/8" eyebolts. Catalina Direct "highly recommends" upgrading to the u-bolts. The replacement eyebolts are appealing for two reasons: First, I've seen the u-bolts installed in my neighbor's 27, and they are not very attractive. Second, the u-bolts are 3/8", so they are small for the existing 1/2" hole. Strength may trump aesthetics, and the 1/2" hole can be filled and redrilled. Still, brand new 1/2" eyebolts seem to me to be more than adequately strong, even for summer winds in the "slot" on the SF Bay, and they leave a total of 4 fewer holes in the deck. CD intimates that dismastings may occur with eyebolts in more than light winds, but I am skeptical of this view. Whether u-bolts or eyebolts, all stress the same deck with similar sized backing plates.

So I am writing to ask for your opinions on/tales of disasters relevant to the subject: "Upgrade" to 3/8" u-bolts for the lower shrouds with 4 new holes in the deck, or stick with the new, quite robust, 1/2" eyebolts?

Thanks for your thoughts, and best wishes!

Peter
 

Joe

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Jun 1, 2004
7,999
Catalina 27 Mission Bay, San Diego
Definitely install the U bolt retrofit for the lowers. ASAP The factory setup is inadequate, it relies on the deck to anchor the lowers and the original eyebolts do not have proper backing. Not good... the deck can be distorted ... leading to more serious issues.
I think the plates are beautiful, and they solve the problem..... in fact I wouldn't consider buying an older 27 without that retrofit.
 

PSR

.
Sep 17, 2013
117
Catalina 27 4743 MB Yacht Harbor, Richmond CA
Definitely install the U bolt retrofit for the lowers. ASAP The factory setup is inadequate, it relies on the deck to anchor the lowers and the original eyebolts do not have proper backing. Not good... the deck can be distorted ... leading to more serious issues.
I think the plates are beautiful, and they solve the problem..... in fact I wouldn't consider buying an older 27 without that retrofit.
Thanks for the thought, Joe. The eye bolts I am replacing are not the originals. They are 1/2", not 3/8", and they have large backing plates, just like the new, replacement eyebolts from CD. The new replacements have large integral plates above deck that have obvious advantages, even compared with the u-bolts. It is not obvious that the backing plates for the upgrade u-bolts are larger, except that they are bent longitudinally (I guess) so they extend from under the deck, up against the cabin wall. They also are anchored by the deck, just like the eyebolts.
Thanks again!
 
Last edited:

Ward H

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Nov 7, 2011
3,645
Catalina 30 Mk II Barnegat, NJ
@PSR Without photos showing your current or replacement 1/2" eye bolts and backing plates, it is hard to compare them to CD's offerings.
Are they a kit someone makes for the C27? Are the large integral plates above the deck welded to the 1/2" bolt and then through bolted to the deck? If not I don't see there advantage.
Standing rigging isn't designed for aesthetics. I would choose the angled backing plates over flat plates of the same length and the 3/8" U bolt over a single 1/2" bolt.

As for less holes in the deck, if prepped (potted with epoxy) and sealed properly, not an issue.
 

PSR

.
Sep 17, 2013
117
Catalina 27 4743 MB Yacht Harbor, Richmond CA
Thanks for the note, Ward, and for your opinion. The replacement eyebolts are a kit that is sold by Catalina Direct, and the above-deck plates are welded to the 1/2" studs. CD recommend the U-bolts, as you and Joe do, but they supply the eyebolts also. I suspect the 1/2" eyebolts with proper backing plates already on my 1981 boat were installed by Catalina after the early years. The originals have lasted well for 37 years.... I'm leaning to the U-bolts, and, fortunately, I can drive to Catalina Direct in 1/2 hr and pick them up. Also will replace the old upper shroud chainplates with CD's much longer and better fastened alternative.
P
 

Ward H

.
Nov 7, 2011
3,645
Catalina 30 Mk II Barnegat, NJ
replacement eyebolts are a kit that is sold by Catalina Direct
I missed that. Sorry.
So, for $20 more you can have the stronger u-bolt kit.
Sounds like you have a good plan, doing the standing rigging and all the chain plates.
Good Sailing.
 

PSR

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Sep 17, 2013
117
Catalina 27 4743 MB Yacht Harbor, Richmond CA
The rest of the story: I replaced the old main bulkheads, making the new ones from okoume 1/2" marine grade plywood. I finished them with Minwax red oak penetrating stain, sealed with 4 coats of Varathane. The red oak on top of the yellowish okoume made a pretty good match to the old teak. These are the new bulkheads installed:

and "decorated":

Here's a a shot of the old port bulkhead, showing water damage along the top and around the bolt holes:

The starboard BH was worse, and both were pretty well destroyed along the bottoms.
I also installed the new main shroud chainplates from CD. These are considerably longer, with 6 bolts staggered down each plate, rather than the old plates with 4 bolts in line. Eric Cutting, recently ex-C27 owner, kindly came over to my boat and lent a hand fitting the main chainplates as well as good company and moral support.
Instead of the u-bolt upgrade from CD, I installed new single stud "chainplates" for the lower shrouds. The new ones, like the old ones, are 1/2" ss, not the older 3/8" studs of earlier Catalina days. The deck plate is welded to the stud and has 2 screws to hold it in installed rotation. These, bedded with butyl tape, are also very secure. I used the old backing plates, which are larger and heavier gauge stainless plates than the ones suppied by CD in the lower shroud chainplate kit. With all new standing rigging, a completely sound deck, new, completely sound main bulkheads, and the new chainplates all around, I'm pretty sure the rig will keep standing longer than I do....
 
Mar 6, 2008
331
Catalina 310 Scott Creek, VA
Had a '77 C27, and broke one of those OEM eyebolts for the lowers during a race. Had a rigger on my crew lash the stay back to the car on track for 95% blade and finished the race. Go for the u-bolt upgrade. I also replaced all the bulkheads on that boat. That C27 could outpoint my 310 in any conditions.
 
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Likes: TurtleLake
Dec 30, 2018
1
Catalina C27 Port of Edmonds
I'm getting ready to upgrade my chainplates and replace the standing rig on my '73 this winter. U-bolts are significantly stronger than eyebolts because they attach to the deck at 2 points. Tension on the shrouds is not along the axis of the bolt shaft so it produces a strong bending moment on the eye, the flange above the deck helps support the moment but applies a compression load on the top of the deck that is localized in a very small area at the apex of the arc on the inboard side. U-bolts on the other hand support the off-axis loading through differential tension on the two legs that is then spread out across a much larger area by the backing plates, the result being no bending moment on the studs and no point loads on the fiberglass.
 

PSR

.
Sep 17, 2013
117
Catalina 27 4743 MB Yacht Harbor, Richmond CA
Thanks for this note Katejacks, and especially for technical rationale for your decision. My “original” lower chain plates were 1/2” studs with heavy, large backing plates. They were not the ill-fated 3/8” studs installed on early 27s, probably without true backing plates. The existing SS backing plates were about 6” x 4” x 1/4”. These are larger and heavier gauge plates than are supplied with the new 1/2” studs offered by CD. I preferred not to install the 3/8” u-bolt “upgrades” because this would have required an additional 3/8” hole in the deck and filling and re-drilling the existing 1/2” hole.

The existing 1/2” studs served for 35+ years. The deck is solid. So I decided that new 1/2” studs for lower chain plates using the original, quite large and heavy backing plates would be a safe as well as efficient approach.

The engineering comparison of functional strength of 1/2” studs with 3/8” u-bolts would be instructive.

If the new chain plates fail catastrophically when I hit 25+ kn winds in The Slot on the north SF Bay next summer, I will be disappointed and will report my error.

I am sure your comments on engineering and u-bolts are correct, and over-engineering for the sake of safety is a very reasonable approach.