Hull structural integrity

[wyoboater]

Ok, all you smart boat builder types:
I have a Luhrs Mainship 40DC. I want to basically gut the forward cabin, removing the platform the bed is made on...here's the question. Does that platform also perform double duty by strengthening and adding rigidity to the bow, or is it just a bed? Plan is to basically turn the forward cabin into a storage area for foodstuffs, etc when we do the Loop.
Thanks in response for your help.

 

[fgarriso]

Why no leave the platform in place and use as a storage platform.

 

[Comodave]

Why no leave the platform in place and use as a storage platform.

+1. Then if you go to sell the boat you haven’t killed the resale value of the boat.

 

[wyoboater]

Because that's not my plan. I'm looking for an answer to a specific question.

 

[fgarriso]

Because that's not my plan. I'm looking for an answer to a specific question.

Do you have all of the original engineering specs.

 

[psneeld]

While most boat structures usually add to some structural stiffness...really hard to say without pics or familiarity with the boat.


My guess .......removal might be OK but keep the boat out of an Atlantic hurricane....but if you need original boat integrity, only someone with specs or a great backyard engineering eye with pics can help.

 

[DDW]

Is the platform tabbed to the hull, or just set on the deck? If I was cutting things out tabbed to the hull, I would leave enough in place to act as stringers, or replace what I ground off with stringers. The usual concern is slamming loads, you want to break up the flat panels with something stiffer. The bed is not going to do much for torsion or bending in that area, but it may be substituting for stringers to resist slamming.

 

[Chrisjs]

Removing the bed completely will certainly lower the vessel value, regardless of whether it impairs hull integrity.
Not your plan but here is another idea!!
Leave the bed in place and cut access panels through the bed platform into the hull bilge area below. You might even be able to add a "floor" over that bilge section below the bed platform.

 

[fgarriso]

I have no idea how much "stuff" you are planning on storing in the bow or what the gross weight is, but their is a couple of things you should consider.

The center of Gravity of the vessel.
The center of Bouncy of the vessel.
The stability curve of the vessel.

If not done you could wind up with a boat that no longer has enough bow lift for its displacement.
You may think everything is fine until you hit a big roller and find it on deck with you.

That is just my humble opinion, and means less than nothing as far as your boat goes.

 

[psneeld]

That could be true if he left the bed and added all the foodstuff as planned.
Removing the bed may help stability, but certainly structure is a definite concern as opposed to user operation.

 

[wyoboater]

PS Sneed. I appreciate your answer, it seems the only one even attempting to address the question I asked. As far as hatch openings in the bed platform, they're already there, just a pia to get in and out of all the time..that's what I'm trying to fix. As far as weight distribution, I don't think that will be an issue. As far as the resale value, this boat was never purchased as an investment. We bought it to use and we want to make it as comfortable for US as possible..I wasn't asking for a critique of the idea, just if it was possible without sacrificing the seaworthiness of the vessel.

 

[psneeld]

Thanks.. .it's just hard to give a better idea"old salt" opinion without seeing it.


Even resale is debatable as I know more than a few full time cruisers that convert now staterooms into storage, workshops, laundries, etc. And those boats get snapped up by other crusiers.

 

[Boat]

The difference between a partition and a bulkhead may be what you are looking for.

This link may not go to the best site but it gives you enough to get started.

https://www.yachtsurvey.com/HullFailPart1.htm


http://www.marinesurvey.com/yacht/Top25.htm

 

[SoWhat]

I wasn't asking for a critique of the idea, just if it was possible without sacrificing the seaworthiness of the vessel.

And there is your answer. If you don't know if it's possible or not, then hire a marine architect who does know.

 

[BruceK]

Anything fixed to the inside of both sides of the hull is doing something,at the very least helping keep the two sides apart. Strength and stiffness too I expect. Don`t know how you determine how important or not it is, but tread carefully. Can you replace it with something less obtrusive or restrictive? An alloy tube laminated on?
As an analogy,we used to weld a steel tube between the McPherson Strut(?Slut) towers on rally cars.

 

[O C Diver]

Will you be putting anything back that could act as structural reinforcement? Wondering if you're plan might include cabinets or shelving that could be tabbed in for rigidity.

To your original question, I would look at the construction of the bed to see how strong the material is. When redoing my 35 Bruno and Stillman V berth area, it was quite clear that the material used and fabrication wasn't structural for the hull, but then most of those boats were built for commercial fishing, not charter boats.

Ted

 

[wyoboater]

Thanks Ted
That's what made me think of the question. The structure of the bed platform seems pretty solidly built, as if it might be designed for dual purpose. Yes, I plan on cabinets, shelves, but nothing stretching across the entire space.

 

[wyoboater]

The Marine engineer idea has merit. I am just getting a general idea of the feasibility before I commit or not commit to the next step. Thanks.

 

[O C Diver]

Thanks Ted
That's what made me think of the question. The structure of the bed platform seems pretty solidly built, as if it might be designed for dual purpose. Yes, I plan on cabinets, shelves, but nothing stretching across the entire space.

Can you confirm that the hull where the bed attaches, is shaped with compound curves? Also is there a floor under the bed and a substantial bulkhead that separates the chain locker from the cabin?

Ted

 

[wyoboater]

Ted.
Yes to both.

 

[psneeld]

Not to contradict ideas as I have said I am just shooting in the dark.....


But just because the bed is tabbed to the hull, not sure that automatically suggests the bed adds anything, could just be the way to help secure the bed in place.


Also ....said before... that almost anything touching the hull add rigidity, but all it might be is increasing a factor of safety a few precent that may well be high enough without it.... Or not..

 

[O C Diver]

Ted.
Yes to both.

Based on the age of your boat, I would guess that the hull is over built. In the last 20 to 30 years, technology has dramatically improved to engineer adequate strength with reduced fiberglass. Is the hull solid or cored?

Ted

 

[wyoboater]

Pretty sure it's cored.........BUT
On further inspection, after removing everything, opening all the hatches in the bed platform, I've found that all of the support for the bed is actually fiberglassed into the inner hull. This tells me that the engineers, architects of the time of the build felt that this was a necessary part of the hull structure....No way I'm gonna mess with it, lol. Time to move on to plan "B" as soon as I think of it.
I do want to thank those of you that took the time to answer the posted question. Your input was instrumental in my final decision....
Kevin
M/V In Disguise

 

[Exctyengr]

OK, I am weighing in late here, I realize. but....if the supports only are tabbed in as you suggest, but the bed platform is not, and the bed platform is simply laying on the supports, you are probably OK removing the bed. Look to see how the platform is affixed to the supports, look to see if there is clearance between the edge of the platform and the hull side. If the connections are non-existent and there is space, the platform is probably non-structural. (Full disclosure, I am a structural engineer but only on bridges) Also, since you are doing the loop and not doing extensive off shore work, you will largely be in protected waters (Great Lakes and some sections as exceptions). You will probably opt not to venture forth in bad weather. Probably worth the risk. Good luck.