Keel Bolt Inspection

[AJW]

I have a 1978 Y30 with cast iron keel and 8 stainless 16 mm (5/8 in) keel studs. I have minor rust staining around the backing plates of 3 of the 8 studs. I'm thinking of inspecting the studs at my next haul-out in April.
Has anyone ever had trouble with corroded keel studs and/or tried to remove them for inspection?
The keel to hull joint appeared solid (no cracks) at my last haul out when boat was hanging in the slings.
I assume the studs are threaded into to cast iron keel so may be very hard to remove.
Has anyone tried this before?
Thanks!

 

[jssailem]

WOW.. It has been 6 years since your last post. Welcome back. Is this boat new to you?

I found this Manual for the Yamaha 30 that may be helpful. Unfortunately, it does not provide info on the keel design or structure.

Boats of that era 70's and 80's used a pretty common design structure for the bolt-on keels.

The keel was secured to the fiberglass hull using stainless steel studs, which were embedded into the cast-iron keel during casting. In some cases, studs were threaded into tapped holes. These studs protrude upward through holes in the hull's keel stub. Inside the boat, backing plates are placed over the studs to spread the forces across the hull laminate and prevent localized stress. Nuts are then threaded onto the studs and torqued to specification, often with washers under the nuts for additional security.

This setup ensures a strong mechanical connection while allowing for periodic inspection and retightening if needed (e.g., due to hull flex or age-related settling). No sealant is typically applied around the studs inside the boat, but the keel-hull joint exterior is sealed with a compound like 3M 5200 to prevent water ingress.

Keeping the bilge dry and performing regular inspections are used to prevent rust from attacking the studs. Check the size of the stud and nut to identify a proper torque value for the nuts. I could not find any specifics on this.

Enjoy sailing here in the PNW. It can be a lifelong adventure.

 

[heritage]

I would remove the suspect nuts of the bolts that are showing rust. I did it while in the water, removing and replacing one nut at a time. If there is crevice corrosion on the upper part of the bolts, it will be very apparent.

 

[AJW]

Thank you for the specifics and for the pdf-manual, jssailem!
Really helpful; I have the hardcopy of the manual but it's good to have it digitally as well!
My sense is that the studs are threaded into the cast iron.
I'll check the nuts individually and see if there is any indication of crevice corrosion underneath. I'll try to extract a couple bolts but I'm not positive that I can remove them.

WOW.. It has been 6 years since your last post. Welcome back. Is this boat new to you?

I found this Manual for the Yamaha 30 that may be helpful. Unfortunately, it does not provide info on the keel design or structure.

Boats of that era 70's and 80's used a pretty common design structure for the bolt-on keels.

The keel was secured to the fiberglass hull using stainless steel studs, which were embedded into the cast-iron keel during casting. In some cases, studs were threaded into tapped holes. These studs protrude upward through holes in the hull's keel stub. Inside the boat, backing plates are placed over the studs to spread the forces across the hull laminate and prevent localized stress. Nuts are then threaded onto the studs and torqued to specification, often with washers under the nuts for additional security.

This setup ensures a strong mechanical connection while allowing for periodic inspection and retightening if needed (e.g., due to hull flex or age-related settling). No sealant is typically applied around the studs inside the boat, but the keel-hull joint exterior is sealed with a compound like 3M 5200 to prevent water ingress.

Keeping the bilge dry and performing regular inspections are used to prevent rust from attacking the studs. Check the size of the stud and nut to identify a proper torque value for the nuts. I could not find any specifics on this.

Enjoy sailing here in the PNW. It can be a lifelong adventure.

 

[AJW]

I would remove the suspect nuts of the bolts that are showing rust. I did it while in the water, removing and replacing one nut at a time. If there is crevice corrosion on the upper part of the bolts, it will be very apparent.

Good to know, thank you! I'll do just that and see what I find. I'll probably also try to extract a stud if it let's me and check for corrosion.

 

[jssailem]

If you get a nut off and the metal looks and feels solid, it might be a good idea to let the studs well enough alone. I’ve found if there is a problem fix it. If there is no problem then fix something else. No need to create an issue where none exists. A mature boat will provide you with plenty of problems to fix.

I tend to let sleeping dogs lie.