Structural solution for mounting a bulbous bow

I’m looking for advice on a constructive/structural solution for mounting a bulbous bow on a steel vessel of around 30 meters in length.
The key constraint is that the client does not want to open or significantly modify the existing stem structure. The bulb has already been optimized through CFD, so the design is defined — the challenge now is how to practically and structurally integrate it with the existing hull.
Since I don’t have much hands-on experience with this kind of retrofit, I’d appreciate any insights.
Any ideas, references, or practical experiences would be very helpful.

Thanks in advance!

 

Optimized by CFD but keep the heavy hammer nearby .
Hull shell plating thickness at the bow section ?

 

Can you post a photo or two of the bow, and a copy of the design of the bulb please?
Will it be welded on, or do you want it to be removable easily (if say you do not like it), and hence have it bolted on instead?

 

You would not approach a public forum for such matters. You need a qualified NA.

 

We have qualified NA;s, inspectors and marine engineers onboard this forum, fallguy. Wait for their response!

 

I remember there was an article on mating a steel bulbous bow (modification) to an existing hull on Professional BoatBuilder magazine. It is a long time ago so expect it to be a back issue and you need to search.

Unless it is a composite bulb that will be mated to an existing steel hull.

 

It will be nice to see internal mesh of stringers and bulkheads outside . Using some device it will be probably easy task .

 

I have extensive experience with metal hull structures and on several occasions, although years ago, I've had to develop construction drawings for bow bulbs and their integration into the ship's existing structure (plans and details, CNC cutting templates, etc.). I'm also accustomed to working with various Classification Societies.
Send me a message if you'd like to discuss this in more detail.

 

Indeed...

 

Hi @Robinfly, I'm going to give you some advice that I think will be useful. If you want to solve your problem correctly, don't resort to a naval architect simply because they are a naval architect. From now on, in your case, a naval architect doesn't necessarily know how to proceed or how to do it correctly. Once the volume, shapes, and position of the bulb have been defined, the naval architect has no further role to play. You should consult a good loftman with knowledge of naval structures or a naval engineer, knowledgeable about ship structures and with in-depth knowledge of hull smoothing. They will solve the problem efficiently, quickly, and cheaply. Take my advice, and you won't regret it.

 

You said it has been CFD analyzed and you are looking for a way to integrate it with the hull. That means it has not been designed yet.

That it has not been structurally defined yet. It also probable that you have a proper "bulb" shape instead of some simple "torpedo" shaped extension.

If you do not want a major modification to the hull, treat it as an "add on", "a sacrificial nose" that will be added to the original structure design.

In any case you need a Draftsman/Loftsman (with ACAD experience) to fully integrate the design to the existing hull and a Structural Designer/Naval Architect to define the load/load path and strength of the new design following the existing scantlings of the old structure from the stem to the collision bulkhead.

Otherwise it is an all out design where everything will have to be stripped from the stem to the collision bulkhead where new keel/stem, frames/longitudinal will have to be designed following the scantling of the old vessel.

 

Depends whether you want to do the work yourself...and be pointed in the right direction,
or
whether you need someone to look at what you have and tell you what you need to do.

Either way, without pictures, drawings etc....you wont get any meaningful replies.
Just lots of suggestions, based on....very little.

 

We must assume that a CFD analysis has been performed, not of the isolated bulb, but of the bulb perfectly defined, positioned, and integrated into the existing ship's form. Otherwise, the analysis, however sophisticated, will be useless. Therefore, in my opinion, what is needed now is, firstly, to define the bulb's internal structure and, once this is done, to study how to integrate it into the existing structure without having to modify it too much.

 

or an experienced builder and sometimes your N.A consults us

 

@Robinfly I see that you logged in to the Forum yesterday - but you have not bothered to reply to any of the many comments above regarding your project.
It would be very useful for all concerned if you could simply tell us a bit more the bulbous bow which you want to add to your 30 metre steel vessel (and tell us a bit more about the vessel as well please).