Bavaria 34 Cruiser Creaking Bulkheads

[Leo]

Hi, new to this forum and new to owning a 2001 vintage Bavaria 34 Cruiser.  I have read a couple of posts about creaking bulkheads (one on this forum).  With our boat the creaking and popping mostly comes from where the bulkhead joins the hard cabin roof lining port aft cabin and also the vee berth cabin.  It is really quite loud when the boat is rolling in seas. Is this normal on a Bavaria 34?  Anyone have similar issues?  Is it anything to worry about? Any ideas on fixing the issue? Regards Leo

[Symphony]

Not unusual and nothing to worry about. The bulkheads are not bonded to the coachroof but float in recesses. The sealant is supposed to keep them apart but sometimes has gaps. It can also be the door frames that are moving slightly as they also float in the bulkheads. It is possible to take those out and see if therre are any spots where there has been rubbing.

[Leo]

Hi Symphony, I appreciate your reply and advice.  I'm definitely less worried than I was before.  Now I understand, the floating bulkhead moves slightly against the coach roof as the boat flexes over the waves.  A bit of a design fault that I will have to live with.  If you put your hand on the bulkhead you can feel the vibration that goes with the noise but you can't actually see any movement.  I read that other owners have used silicone spray, soap, talc powder, cedar oil etc.  Are any of these likely to be effective? Regards Leo

[JEN-et-ROSS]

We are in serious danger of making excuses for some pretty shoddy boat building here.
 Whether or not Symphony is correct and it's nothing to worry about, it should not happen in any yacht.
  Every boat/yacht creaks a bit under load, but this idea that your bulkheads 'float' is odd since it's these very bulkheads that take the deck loads (not the mast, the compression post takes that)  Also in most cases the tie rods to the chain plates are anchored in the bulkheads, so the shroud loads are also being absorbed by the bulkheads.
  Bavaria build great boats but it would concern me greatly if my bulkheads 'moved slightly' and made 'popping noises' ( they don't !)
I'd be interested in a surveyors opinion on this.

[IslandAlchemy]

The bulkheads don't float.  They look like they do, but they are glassed-in at the top.  Some of them site in slots at the bottom though.

The creaking is usually bits of wood moving against each other, not against the fibreglass.  Easy solutions are:- oil (olive oil or similar) which lubricates it and stops the creaking, or more permanently epoxy/microballoon fillets (which glue them together).

The door frames are just screwed in with a bead of clear silicone (to stop them creaking). These are often the cause of creaks when rolling.  The door frames are easilly removed.  A few of my doors became difficult to shut where the bulkheads had expanded slightly and were creaking, so I removed the frames, planed down the edges of the bulkheads and replaced the doors.  This has stopped almost all of the creaking I had in the boat.

[Symphony]

We are in serious danger of making excuses for some pretty shoddy boat building here.
 Whether or not Symphony is correct and it's nothing to worry about, it should not happen in any yacht.
  Every boat/yacht creaks a bit under load, but this idea that your bulkheads 'float' is odd since it's these very bulkheads that take the deck loads (not the mast, the compression post takes that)  Also in most cases the tie rods to the chain plates are anchored in the bulkheads, so the shroud loads are also being absorbed by the bulkheads.
  Bavaria build great boats but it would concern me greatly if my bulkheads 'moved slightly' and made 'popping noises' ( they don't !)
I'd be interested in a surveyors opinion on this.

That is not the case on boats of that design. No rigging loads are taken by the bulkheads. The tie bars go to substantial ring frames that are linked to the reinforcing grids in the hull. You can see them very clearly if you remove the backrests of the saloon berths. So no significant loads are taken by the deck moulding which is why they are not fully bonded in. This was quite a common method in the period, not just Bavaria.

The Farr designed boats (roughly 2009 onwards) are very different and chain plates  are on the hull rather than inboard using tie bars. The reinforcing taking rigging loads is part of the layup of the hull. No loads through bulkheads, but these and the furniture grid are bonded into the hull to become structural.

I have owned both types - a 2001 37 and now a 2015 33 and the latter is very much stiffer and no creaks. However this does not mean the earlier design is necessarily inferior. My 37 survived 7 years chartering and I owned it from new until 2015 with absolutely no structural issues at all, despite the flexibility and odd creak in rough weather.

Interesting article in this month's PBO on the deficiencies of chain plates secured to bulkheads - even on so called "quality" boats!

[JEN-et-ROSS]

Hi Symphony. I'm not familiar with the construction method using ring frames to resist rigging loads.
 I take it from your description that the 'ring' frame doesn't continue across the underside of the coach roof.
 If that's the case then it's a 'U' frame that, as you say is secured to a reinforcing grid that, in turn is I guess is resisting keel loads.
 In aircraft, all fuselage/hull framing is 'ring' frame to resist the wing loads that would distort a 'U' frame by 'squeezing' in at  the top.
 I think that the shroud loads via the chain plates are doing just that, pulling the top of the 'U' frame inboard causing the hull to distort on that side just enough to cause the creaking, slight movement and popping that has been reported.
 I'm not suggesting this could be dangerous as it's unlikely that the frame is being pushed beyond it's elastic limits, but it is inferior to the earlier design and the later Farr hulls that you describe, I'm not surprised Bavaria dropped it.
 Though it must have made construction much simpler since once they put the lid (coachroof) on it doesn't need to be structurally attached to the rest of the hull, just fill any gaps.
  You'll probably tell me now the 'ring' frame IS continuous, if that's the case ignore all of the above......
I did read the PBO article....That is very poor design. .........Bill

[Symphony]

It is not a complete ring frame, but comes up to the top of the seat backrests and the tie bars are attached to it with stainless steel bracket. You can clearly see the tie bars in any interior shot. The frame itself is about 70mm thick laminated ply on edge and glassed into the hull, or in some layouts like my 37 also to a dividing bulkhead in the galley structure as well. The important thing is that the fitting at the top of the tie bar goes straight through the deck so no loads are taken by the deck moulding but transferred straight to the hull and its reinforcing structure. Being a fractional rig, the backstay does little to support the mast and is very light with simple attachments to the transom, which itself is part of the deck moulding.

As I suggested this type of arrangement was quite common at the time and did have the advantage of shrouds being inboard which allowed narrow sheeting angles with the overlapping headsails that were also common. Fashions change and with the move to smaller headsails with tracks on the coachroof, inboard shrouds are no longer necessary. So chainplates on the hull are now back in and I would imagine much easier and cheaper to build provided you get the reinforcing in the hull right to spread the loads. No more tie bars mean more flexibility in how you fit out the saloon. However going forward on deck(at least on the 33) is a bit more tricky as the lower shroud cuts across neatly at chest height!

[patprice]

My B42 squeaks a bit. however, I am not sure it is caused by "wind or wave"

By wind of course I mean the standing rigging loads on the hull. By wave I mean the ever changing forces on the hull caused by rolling, pitching, corkscrewing and all manner of ways the sea imposes loads on the hull. And these loads will cause the hull to distort to some degree.

So the bulkhead noise will be a result of both wind and wave forces.

[Leo]

Thanks for all the comments and advice.  Symphony, I agree the bulkheads are loose within the recesses in the cabin liner.  By coincidence the photo in the recently posted ?Forward Cabin Leaks ? Stanchions? thread shows the deck and liner fabrication being lowered onto a hull with the bulkheads in place (not sure what model / year this is).  There appears to be no attachment, the bulkheads are just slotted in. Also, where the chainplates attach to the hull on my Bav 34 is well aft of the forward bulkhead indicating that the bulkhead doesn?t contribute to the strength of the mast support structure.  Jen-et-Ross, I did take your advice and have discussed with a highly reputable marine surveyor who has confirmed that the bulkheads are not bonded to the decks or cabin top and simply fit in the recesses but do stop downward deflection. No loads are carried as mentioned as the chainplates run down on to the hull.  Obviously, I will monitor the bulkheads and will try inserting some rubber strips in the very small gaps as a cushion which will hopefully reduce some of the annoying noise.  I might also remove and re-bed the door frames in case this is part of the problem.  Patprice, the noise is contributed to wave rather than wind.  Just rolling over the waves when there is a reasonable swell up.  Thanks again for all the replies. Regards Leo.

[JEN-et-ROSS]

I've learned a lot from this discussion as in any boat I've owned or sailed the bulkheads are/were of heavy construction and integral to the hull and coach-roof to form a largely rigid structure.
 Bavaria must have found this suited their assembly-line methods, though they must have aware of owners concerns regarding noise and movement.
 There is though one query, why was (as Symphony states) 'laminated ply on edge' used in a structural member that flexes (however slightly) under load? when ply on its edge is very weak in tension and doesn't like to bend. Wouldn't S/S or Galvanised M/S glassed-in have been a better choice?
           But wot the 'eck, it obviously works. 
 

[Symphony]

I did not explain that very well. The frame is made of ply, but is thicker as I suggested, so laminated up from more than one sheet to get the required thickness. Think of it like a section of a normal ply bulkhead, but I would guess 3 panels glued together face to face then laminated to the hull on edge. The fitting for the tie rod is a stainless steel saddle that fits over the top and is through bolted.

[Boatname]

Sorry for a late response but lost the link to the site. I'm neither defending nor knocking but some friends of ours bought a Beneteau Oceanis 46 and have made their way down to The Med complete with badly creaking non-bonded bulkhead. On two occasions it was so noisy in rough weather in marinas that they actually stayed in the nearest B&B. They love the boat, hate the creaking. Nothing to worry about structurally on either marque.