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Old 12-12-2015, 05:37   #1
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Would like an open plan, though will I undermine hull Integrity?

Hi, I'm after some structural advice here,...will, by cutting back say the starboard aft plywood/glass bulkhead to make the interior layout alittle more open & to accomodate a larger galley leading into saloon undermine integral strength?
Hull is built of 17mm C-Flex GRP.
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Old 12-12-2015, 05:42   #2
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Re: Would like an open plan, though will I undermine hull Integrity?

Talk to the NA who designed her.
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Old 12-12-2015, 05:48   #3
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Re: Would like an open plan, though will I undermine hull Integrity?

Short answer, it depends. For the main bulkhead which carries the chain plates you probably don't want to do more than this.
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Old 12-12-2015, 05:52   #4
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Re: Would like an open plan, though will I undermine hull Integrity?

Elsewhere can get rid of more since bulkheads are often used mainly to support furniture. Depends. Looks like there are a series of laminated beams supporting the cabin top which helps. If the aft bulkheads are very thin (<12mm) than more likely they are not structural.

Agreed, first move is to talk to designer.
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Old 12-12-2015, 06:23   #5
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Re: Would like an open plan, though will I undermine hull Integrity?

Cool, thanks for that mate, will do..
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Old 12-12-2015, 09:44   #6
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Re: Would like an open plan, though will I undermine hull Integrity?

Can't see the overhead but that interior looks like a disaster in the making. Can't see any handholds, posts or other aids to allow movement fore and aft in a seaway. Open is nice but you might actually want to move it out of the slip sometimes and go sailing on that big and lumpy ocean. Only way I can see moving about in rough conditions is to crawl through the salon.

As far as the bulkhead, cut a reasonable opening in it but leave its periphery intact. That way you'll still have most all of the reinforcing effect and still allow light and visual contact.
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Old 12-12-2015, 09:58   #7
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Re: Would like an open plan, though will I undermine hull Integrity?

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Can't see any handholds, posts or other aids to allow movement fore and aft in a seaway.
My thoughts exactly when I saw the pics. Great plans for a boat tucked away safely in a slip, not so much for a boat that'll be under sail at some point.

Having said that ... many of the larger, modern sailboats are "go inside at your own risk while under sail" so maybe I'm just old fashioned and is crawling through the cabin the new, hip thing

Other than that, talk to the designer, as others have already stated.
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Old 12-12-2015, 10:40   #8
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Re: Would like an open plan, though will I undermine hull Integrity?

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Talk to the NA who designed her.
best possible answer. most likely, it will but, we could set around pondering a month and not know or sure without consulting the guy who designed it.
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Old 12-12-2015, 11:51   #9
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Re: Would like an open plan, though will I undermine hull Integrity?

Quote:
Originally Posted by Boxertwinjeff View Post
Hi, I'm after some structural advice here,...will, by cutting back say the starboard aft plywood/glass bulkhead to make the interior layout alittle more open & to accomodate a larger galley leading into saloon undermine integral strength?
Hull is built of 17mm C-Flex GRP.
webs at chainplates would be a worthwhile idea as I dont know where they are, but when scandalising a bulkhead also consider the depth of the framing and the amount of it

2015 Beneteau Oceanis
note above remaining bulkhead in white



note doubled bulkhead frame and floor riser and the other side of that deck framing in white fibreglass, which seems to be appropriately solid



images copyright to Beneteau under Article L 716-9 of the French Intellectual Property Code

I imagine theyve put diagonal rovings in the area of the bulkhead around the floor and deck on the inside of the hull, and a suitable pad for the bulkhead framing to land on. And these are something you could do too.

Beneteau have done this for a more spacious feel in a 35ft boat and it works. Notice too the lack of cupboards behind saloon seating to enhance that spaciousness at eye level.

Beneteau know more or less exactly the loads they are dealing with. Using this as a model, you would have to overbuild on that. But your own images suggest not one bulkhead but two. I think for simplicity I would open both bulkheads up in a similar fashion, and bolster the framing in the deck above, and the saloon deck and floor between the two. It would be ideal if the chainplates were in the same area.
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Old 12-12-2015, 12:09   #10
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Re: Would like an open plan, though will I undermine hull Integrity?

Quote:
Originally Posted by Boxertwinjeff View Post
Hi, I'm after some structural advice here,...will, by cutting back say the starboard aft plywood/glass bulkhead to make the interior layout alittle more open & to accomodate a larger galley leading into saloon undermine integral strength?
Hull is built of 17mm C-Flex GRP.
A little more info may help. I don't think you will have a problem. Keep the upper part of the bulkhead in tact. C- flex is some durable stuff if laminated on both sides.
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Old 12-12-2015, 12:29   #11
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Re: Would like an open plan, though will I undermine hull Integrity?

Keep in mind though that Beneteau designed the boat that way. They are relying on ring frames instead of bulkheads to carry the loads. Just curing away bulkhead material is risky. It may be fine, but only the NA can tell you for sure.
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Old 12-12-2015, 12:32   #12
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Re: Would like an open plan, though will I undermine hull Integrity?

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Originally Posted by ZULU40 View Post

2015 Beneteau Oceanis
note above remaining bulkhead in white
Beneteau have done this for a more spacious feel in a 35ft boat and it works. Notice too the lack of cupboards behind saloon seating to enhance that spaciousness at eye level.
IIRC, some others have noticed a distinct lack of handholds on those boats, too.
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Old 12-12-2015, 13:01   #13
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Re: Would like an open plan, though will I undermine hull Integrity?

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IIRC, some others have noticed a distinct lack of handholds on those boats, too.
just be aware there are removable square ottomans which make the seat seem U shaped which you might want to remove to the forward area of the cabin where they are meant to stow.

central table fiddles
deep cabinet fiddles on the starboard side
deep plotting table fiddles on the port side
companionway stair vertical handrails arent apparent perhaps need to be fitted, but they exist on other examples of the same boat as chrome tube with red leather covers

the bulkhead as the infill fitted on this boat but its the same layout (there are 3 layouts)

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Old 12-12-2015, 13:27   #14
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Re: Would like an open plan, though will I undermine hull Integrity?

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central table fiddles
deep cabinet fiddles on the starboard side
deep plotting table fiddles on the port side
IMHO, in my humble OPINION, get it, opinion:

table fiddles are a ridiculous excuse for proper handholds.
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Old 12-12-2015, 13:35   #15
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Re: Would like an open plan, though will I undermine hull Integrity?

I'm with those who caution against lack of handholds. Being thrown is no joke and has the potential to be fatal. Vide my post a few days ago about narrow wheelhouses in fishing boats in the North Sea.

As luck would have it, the day this discussion first came up, the first thing my eye fell on, when I sat down by the telly to watch the news, was an old Bruce Roberts catalogue — so old that the sticker price is a whole, entire "loonie" [about six bits US at the moment :-)]. And in it is an arrangement plan for the Roberts 36 raised deck job under discussion here. I will attempt to attach my scans of the relevant pages.

C-Flex was the new miracle material back then (early '70s?) that would save us all from Satan's Power and the need to make female moulds for frozen snot boats. The technique is discussed on one of these pages. Bruce Roberts rode to success on that mighty tsunami of desire to go sailing that characterized the early '70s and he pitched his stuff to the dreamers that thought that boats could be built for cheap "fonly I could do it myself!" Little thought was given to the fact that in the end the naked hull as it comes out of the mould represents only about 10% of the "ready for sea" cost.

The handhold issue aside, and referring to the comment about "ring frames": Yes, if you analyse the stress lines in a plate bulkhead, you will see that they do in fact form a "ring" at the outer edges of the bulkhead. That is the rationale behind "ring frames". You just cut out then "unstressed" central bits where the stress lines are less dense.

If the appointments don't get in your way there should be no reason that you cannot cut out the central bits of your existing main bulkheads, and then "sister" them along the periphery to make what amounts to ring frames. The calculations required to determine moulding and siding of these "sister frames" are not something anyone can do on the fly, but AFAIK Bruce Roberts is still active, and I'm sure he'd do it for you for a fee.

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