Bulkhead movement?

[twistedline]

Hello,

I have a Hunter 25.5 and while re-bedding my port chainplate I noticed that it had moved about 6mm to starboard. After being puzzled for a few minutes I figured that my bulkhead must have moved, which it had! At the top of the bukhead, you can now see a small gap.

So as I usually do, I dove in and started loosing my shrouds with a plan to push the bulkhead back into place. After about 10mins I stopped undoing things and decided to put everything back. I think its been like this for many years, perhaps this is a job better suited to the end of the season rather than the start.

How should I tackle this? and how do I stop it happening again? I would probably leave it be but the little stainless plate that covers the chainplate is pushing into the cabin top and the screw holes don't line up correctly anymore.

I went though my old pictures and came up with this, you can just make it out.

Thanks.

 

[Canonshooternb]

Do you see any movement anywhere else on the bulkhead? It appears that the chain plate support has not moved. Mine is on the hard and I will take a look this evening when I get home.

 

[Brian M H23]

I'd say, if it worries you, fill the gap with rigid expanding foam, trim it, and paint it to match the bulkhead. But if it's moving away, that may not be the best answer. Is that the mast support post? I'd expect to have screws from under the mast step into that bulkhead as well - is anything noticeable up top?

 

[twistedline]

I'd say, if it worries you, fill the gap with rigid expanding foam, trim it, and paint it to match the bulkhead. But if it's moving away, that may not be the best answer. Is that the mast support post? I'd expect to have screws from under the mast step into that bulkhead as well - is anything noticeable up top?

Yes that is the mast support post. I don't care about the bulkhead, its the deck I am worried about, although I think its all just cosmetic.

Here is an old picture, you can see the metal plate has moved starboard and is pushing into the cabin top. I actually ground and filled those cracks last year so it looks much better now but obviously the cause of the cracks its still present.

 

[Brian M H23]

My answer here, as an engineer, is to monitor it. Take some good measurements of the gap, chain plate to hull, etc. Fill the gap inside, have a local shop make up a new stainless cover plate with the holes offset 1/4" or grind the slot a bit longer. Worry about it if it moves again.

 

[twistedline]

My answer here, as an engineer, is to monitor it. Take some good measurements of the gap, chain plate to hull, etc. Fill the gap inside, have a local shop make up a new stainless cover plate with the holes offset 1/4" or grind the slot a bit longer. Worry about it if it moves again.

Thanks Brian. That's what I was thinking. I will keep an eye on it.

 

[twodzusfittings]

I re bedded mine with Butyl Tape, but did not have any movement. Check your compression post, did it move also? You might need to realign everything, shore up the gangway temporarily and do your re bedding, tighten your shrouds and then remove your shoring. Can you close the door to the V berth as it is now?

Here is my re bedding outcome.

 

[twistedline]

I re bedded mine with Butyl Tape, but did not have any movement. Check your compression post, did it move also? You might need to realign everything, shore up the gangway temporarily and do your re bedding, tighten your shrouds and then remove your shoring. Can you close the door to the V berth as it is now?

Here is my re bedding outcome.

Thanks, my compression post seems solid and doesn't seem to have moved. The only place the bulkhead looks to have moved is where I have drawn the arrow, all the other sides seem to be ok. I will leave it for another day.

Thanks for the pictures.

 

[Crazy Dave Condon]

I saw one photo of a crack in the deck. First, the plate that is screwed down, is it a cover plate and if so, do you rebed it once in a while? Any sponginess in the deck at that point? On the inside, do you see any water staining on the bulkhead. Best during a good drench or rain, to see if that area is wet inside. If all is no except for the first question which should be yes, do what the first respondent suggested and fill the area. There is an old saying. If it aint broke, then don't fix.

crazy dave condon

 

[twistedline]

I saw one photo of a crack in the deck. First, the plate that is screwed down, is it a cover plate and if so, do you rebed it once in a while? Any sponginess in the deck at that point? On the inside, do you see any water staining on the bulkhead. Best during a good drench or rain, to see if that area is wet inside. If all is no except for the first question which should be yes, do what the first respondent suggested and fill the area. There is an old saying. If it aint broke, then don't fix.

crazy dave condon

Hi Crazy Dave,

I have only had the boat 12 months, the cover plate was covered in butyl tape, didn't look pretty but it didn't leak, I just re-bedded it which is how I discovered that it had moved. Bulkheads around where the chain plates attach are in good shape, I jabbed them with a screwdriver and they are solid. The deck seems ok, not soft but it does creak a bit (dry delamination?) After the hot summer months I plan to drill some holes and try and get some penetrating epoxy in there.

 

[egodsey]

The trim plate that is screwed to the deck is just that, a trim plate. It has nothing to do with the structural integrity of the chain plate. In your case it does clearly show that the port chain plate has moved inboard. And this has been confirmed by your inspection of the port bulkhead ... the bulkhead has indeed moved.

A quick look at Skene's Elemenents of Yacht Design shows that for a Hunter 25.5 the compression load on the mast (and thus the tension on each chainplate) could easily approach 10,000 lbs. This is the reason the chainplates are thru-bolted to the bulkheads ... and why the attachment points are reinforced with an inch thick, teak backing plate.

The trimplate and the bedding of the chainplate are important ONLY because they help prevent water incursion ... which can damage the bulkhead (and the chainplate itself). But understand, the trimplate and the bedding of the chainplate are of NO structural value.

When faced with a similar issue on my Hynter 25.5 my solution was to replace both bulkheads ... which was a major pain. Thus I consider bulkhead replacement pretty much a court of last resort ... but the thought of a chainplate letting loose is rather unsettling.

If you are confident in the structural integrity of the bulkhead(s) then you might be able to get by with a simple re-bedding. But with the amount of movement you describe I would suggest that at the very least you REMOVE the chainplates ... and then inspect the chain plates, the bolts that attach them to the bulkheads, the bulkheads and the backing plates. And even then you will NOT be able to inspect the top of the bulkhead ... which is a key surface because it distributes the load on the chainplate to the (underside) of the deck.

Removing and re-installing the chainplates will also enable you to do a more thorough job cleaning and re-bedding them ... which should help you get a better seal. But, be aware, I had to re-bed both chain plates after the first 6 or 8 months of sailing. The difference between "no load" and "load under sail" was enough to crack my initial bedding job. It was very obvious ... after a summer of sailing the the chainplates were 2 or 3 mm higher than when I had first launched the boat. And in a heavy rain they were leaking.

Good luck. You'll enjoy your Hunter 25.5 immensely once you get everything sorted out.

Regards,

E. Godsey

 

[Crazy Dave Condon]

It would be interesting to see some photos one of the other side of the bulkhead and directly looking at the gap.. Deck is solid, no leaks, etc.. A few more photos please. AS for the bulkhead itself, it can be seen to see if has been damaged by water. It has been years since being on a 25.5 but is the bulkhead glassed into the hull or does it just sit in place. thanks.

crazy dave condon

 

[twistedline]

It would be interesting to see some photos one of the other side of the bulkhead and directly looking at the gap.. Deck is solid, no leaks, etc.. A few more photos please. AS for the bulkhead itself, it can be seen to see if has been damaged by water. It has been years since being on a 25.5 but is the bulkhead glassed into the hull or does it just sit in place. thanks.

crazy dave condon

Going sailing this weekend, I will get lots of photos.

 

[twodzusfittings]

Trying to use my crystal ball to solve the puzzle of the moving bulkhead. I believe the bulkhead is inserted into preformed fiberglass slots, or at least on the top if not top and bottom. It being a tight fit, could the inner and outer bulkheads blocks and the bulkhead itself be deterieoting to the point that the holes for the bolts which hold the chain plate itself, be elongated, therefor by loosening the the shroud, getting movement as described? Suggestion: Loosen shroud again, have someone push the bulkhead back into the slot and tighten shroud. See if that puts it back. Then you can decide how to proceed from there.

....and this is just me thinking it through, not an expert in the field like so many of you ......

 

[Crazy Dave Condon]

I will wait till I see some photos. twistedline, I believe you sent me an email thru the forum and I sent you my personal email back. Please send me the photos no more than three at a time per email. Many thanks.

crazy dave condon

 

[drumbeater]

That bulkhead looks like it is screwed to the mast post. If the bulkhead moved wouldn't the mast post had to have moved also?