I have suffered corrosion damage to my compression post and am replacing it. The damage has left a 2 inch hole from the cabin into the centerboard trunk - when sailing at 15 degree heel or more it admits water, and when heavily loaded forward it drops below the water line and lets water in in a constant stream.
I contacted Bill S at the Macgregor factory who is pricing the pole and a procedure to replace it. It attaches with 4 bolts up top, and two on the bottom. I hope to be able to wiggle it out without cutting the liner, but if not I can make a cosmetic cut under the table which will be easy to fix. Im planning on making two vertical cuts and then bending the liner to let the pole slip out, the Fiberglass the inside of the liner to strengthen it again if this route is needed.
Pictures of damage
Up close
My compression post is almost half gone at the attachment to the plate
Last edited by Catigale on Sat Sep 08, 2007 4:52 am, edited 2 times in total.
That looks like a major safety issue. I sail primarily in salt water and am very concerned that this could be happening on my boat without me knowing it.
Maybe I'm missing something, but why not cut the compression post and remove it in 2 pieces. Then limit the cutting of fiberglass to installing the new one. That way you are only concerned with one way of travel and possibly doing less cutting/repair. (You may be able to "lift" the post enough to slide over the liner as these boats do flex.) Don't forget about the CB line inside. Best of Luck
Minutes after reading the original thread concerning this aweful structure failure, I checked my "X". I pulled the plexi plates, and gave a thorough look-see. I notice that the weld is secure, the silicone looks good, no fiberglass cracks, and so far Okay. The factory weld couldve been a little heavier duty in my opinion. No cracks, so far.
Thanks for posting this alert, and hope your structure repairs go easily and well
Last edited by LOUIS B HOLUB on Wed Sep 05, 2007 11:55 am, edited 1 time in total.
Much easier to cut the liner than that post, I think. If my trick of two vertical cuts works, i might have two lines on the inside of the liner under the table which will hardly be visible....
This damage is almost certainly due to stray current in the marina where I was slipped - I dont think my electrics were the source.
Stephen,
I'm still puzzled by this electrolysis, since the post is above the waterline while resting in the slip, right? In fact, I'd guess you had no metal in the water, though you might have had a 110-charger hooked up.
- Care to theorize on the potential path(s) of this low voltage?
- Could this stray current have impacted the outboard or its alternator?
- Would an isolator or AC/DC bonding have helped?
- (is that a Classic Rock fan club?)
I've often pondered that the motor is a non-issue, since I always leave it tilted up from the water. OTOH, it's not a giant stretch to imagine forgetting to lift it some Sunday evening!
EditoAdd:
Hmmm ... was just browsing w/Search -- found this comprehensive thread regarding Shore Power and AC/DC Grounding & Bonding!
Last edited by Frank C on Wed Sep 05, 2007 12:58 pm, edited 2 times in total.
In addition to all the above comments, you've also almost always had your boat in fresh water, right? I've always thought of galvanic corrosion as mainly a problem in salt water where the conductivity of the water is so much higher.
I think the Mac factory should pay to have the base of your compression post analyzed to figure out exactly what caused the problem.
Frank C wrote:Stephen,
I'm still puzzled by this electrolysis, since the post is above the waterline while resting in the slip, right? In fact, I'd guess you had no metal in the water, though you might have had a 110-charger hooked up.
- Care to theorize on the potential path(s) of this low voltage?
Could this be a possibility: ( )
When the ballast is full, and the boat is in the slip, there will be bobbin' around. Water levels in the centerboard trunk will be close to, or touching, the two bolts holding the compression post plate (and more likely if the boat is loaded with storage stuff). Im assuming the 2 bottom bolts go completely though the centerboard trunk, and are exposed to the water under the boat. That likely would be the only water and metal connection available if the engine is kept in the "Up" position.
I keep my ballast tank empty since my Marina is wind protected.
Last edited by LOUIS B HOLUB on Thu Sep 06, 2007 4:55 pm, edited 1 time in total.
I am no welder but the weld doesn't look like it was hot enough for that plate! Plus other possibilities, mismatch of SSteel grades between post and plates and or wrong grade wire used to weld with, not to mention a bad weld. I wonder, have you checked for any debris in the area? Like maybe the weld just flaked off, may have fell into the boat or out through the hole it left. I have seen some bad welding cause similar problems.
Maybe a welder out there will enlighten us!
I talked to an expert in welding I 'happen to know' (its cool having a database of 6600 people including 10 Nobel Laureates) and his analysis is classic bad weld - even told me the honeycomb effect that looks like electrolysis is the erosion of ferrite domains from a botched weld..very common in SS to SS welds if temperature is not managed correctly.
Stray current in the marina still doesnt make sense to me as there is no grounding path on this puppy, so my theory might be changing.
Ill talk to the factory today about the replacement.
Sort of reminds me of an incident actually two when during two separate ICW spring trips at the top end of the Gulf of Mexico.
We overnighted at the same marina, same slip this year and last, and on both occasions had problems getting to sleep due to a noisy crackling and snapping like burning logs. Searched high and low but never could trace the source. We had no power connections to the dock and motor was raised.
Stray electrolysis munching away at my boat. Hhmm.
Maybe we won't be stopping at that particular marina next year.
Best of Luck
)
