J/30 Class Association Forums J/30 Forum One Design Class Rules Ruling request, modified chain plates

I guess I need to make a formal request for a ruling on my modified chain plates.
The chain plates are oversized compared to the OEM. If you need to know what they look like, several months ago I submitted drawings and they are somewhere posted on this web site.

I need to know a yes or no this week as I am about to purchase a vehicle capable of towing the boat.
If the answer is no, I'll understand but too, I won't bother with the vehicle. If the answer is, we'll have to vote on it at a future BOG meeting, I'll interpret that as a no.
Thanks, I look forward to a response

The modified chainplates that Russ refers to are described in this post with links to the CAD drawings he provided.

Personally, I would do the same modification on Rhapsody after removing the chainplates this winter so I could dig out the area and seal the deck. I found when I put the port chainplate back on that the bulkhead has a small crack and compresses, even though it is dry. I plan on fixing that as part of the next off season project.

I will ask Charlie Stoddard to speak to Rod Johnstone for an opinion on the modification so a ruling can be made quickly. It appears this change has no impact on sailing performance, but does improve structural longevity.

If the enlarged chainplates are not approved, this may be where we part ways. Refer to an earlier thread:
https://j30.us/ubbthreads/ubbthread...30_bulkhead_technical_dis.html#Post11207

The orignal chainplates are of poor grade 3006 stainless. This has a very high ferrus content. Replacement with grade 3016 is the MINIMUM upgrade that should be performed. In addition, the load needs to be spread out over a much larger area of the bulkhead. This was pointed out to me when we reviewed the design with a licensed marine surveyor. As a result, both of my upgraded plates extend downwards until it meets the curve of the hull. This design is typically found in custom offshore sailboats. If it is a choice between a safe boat vs. a boat that meets the one design rules, guess which wins? I respect Rod's ability to design a fast boat, however, the chainplates that were selected for BOTH the J-24 and the J-30 have nearly resulted in disaster on MY boats due to stress cracking. For those of you who tension the rig to 1800 lbs, especially take note!!

We are working to get a quick review done on this

What is being requested makes good common sense.

Russ

The repairs and changes you have made to boat are consistant with what you felt was best for resolving the problem your specific boat had. They in no way effect Rule 1.4 which are changes which would change peformance etc. on the boat

I have Emailed Rod Johnstone on your change and he feels that in no way does it effect the "one design" performance of the boat.

The class does recommend that anyone who wants to make a "repair / Modification" which is out side of the original design consult with the class measurer prior to making the change

In speaking with other long time J30 owners no one has encountered any stress cracking of the factory supplied chain plates. Were a 304 Stainless is a lower grade of stainless from 316 for corosion the shear strenght is similar and should be fine for the application.

So Russ your out of luck and have to by a truck now Good luck in New Orleans

Thanks Charlie,
A couple of commnets. First, the truck issue is done. I'm a trailer away from NO

Regarding the 304 vs 316. Shear and tensile strengh were similar. For anyone concerned about the stength, take a look at the size of the shackle that holds the main fiddler block to the traveller and then consider the load on that small pin and shackle during a crash jibe. The stresses on the chian plate are well below the limits of the material. Regarding corrosion resistance I did speak with folks in the steel industy plus found hydraulic pumps designed for salt water environment that were made of 304. The issue isn't the chain plate it's the bulkhead.

One other note.
You are right, I should have consulted the class regarding the chainplate design, but quite honestly, when I saw the bulkhead crack and took the chainplate off I was more concerned with the best way to fix the boat rather than complying with one design. It would've served no purpose to have a broken boat that complied to OD. If I tore the bulkhead off and repaired the crack, I never would have been comfortable with putting the original chainplates back on. Bottom line something had to be done. I didn't think about this as an OD issue until the fuss about the vent came up. I would not have been happy showing up in NO and be told I couldn't sail with my chainplates.

From a design perspective, the only other scenerio considered was machining out a portion of the bulkhead and inserting a steel plate about the size of the new chainplate. To that we then could have flush mounted the old chain plate. That would have been a lot of work. This design incorporated the bulkhead strength plate and the chain plate in one.

I would like to point out this quote ... which basically relates to One Design PERFORMANCE. I have a feeling that we are confusing One Design PERFORMANCE oftentimes with One Design APPEARANCE. We have so many rules on what has to be on the boat just to "equalize" that we are forcing more and more people to abandon hope of ever racing OD. and as the existing fleet shrinks ... it only makes it harder to race strict OD as parts on the existing boats out of OD service disappear.

80% of any racing advantage is simply crew skill levels.

I agree with Russ, the problem is usually water getting into the bulkhead from above. That was our issue some years ago. The repair reused the original chainplates. The fact that Sailon found cracks doesn't necessarily mean this is a materials or design flaw. Thirty year old parts are subject to wear and tear, so inspect and maintain. Let's not start a panic, unless or until someone does the engineering analysis to show otherwise.

I'd like to ask that any further posts discussing opinions and subjective discussion be taken to the "Boat, Sails & Equipment" forum. Please limit posts in this forum to one design rules questions and interpretations.

Thanks,