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Old 01-11-2011, 19:23   #16
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Re: Drilling Holes in Structural Bulkhead

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Originally Posted by SVNeko View Post
Thanks for all the replies. Very thoughtful. The boat is a Switch 51. I don't know how to post pictures but there are many on the net. The bulkhead in question is just forward of the engine room. It is just aft of the helm. It is not a cross beam, nor connected to a cross beam. It is a watertight bulkhead, but I don't think that matters so much. The existing hole and this hole will be high enough such that if the hull is sunk that low, there is water forward of the engine room anyway. I think I will cut a round hole and glass in a piece of pipe, building up the layup around it for strength. Maybe overkill, but why not.
Ah, then no problem. Your only concern is with water-tightness, and you have considered that.

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Old 02-11-2011, 01:45   #17
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Re: Drilling Holes in Structural Bulkhead

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How about if he cuts a 3 inch hole through the structural beams or uni's ?

Don't you think the strength would be considerably weakened then?
I do not propose cutting thru anything but a panel. A panel is defined as an area of equal thickness. I don't know what you mean by a "uni," but if it is a reinforcing buildup (what we in aviation call a "stringer") then do not cut thru it.

In your photo, I see 6 square areas each of which have a diagonal reinforcing member. This reinforcing member divides the square into 2 triangular panels. In this example, make the hole in the middle of the triangle.
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Old 02-11-2011, 05:40   #18
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Re: Drilling Holes in Structural Bulkhead

"I want to do it - then must be OK"

It's stuff like this where a Surveyor really earns his money for a prospective buyer..........
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Old 02-11-2011, 07:07   #19
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Re: Drilling Holes in Structural Bulkhead

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Originally Posted by colemj View Post
Ah, then no problem. Your only concern is with water-tightness, and you have considered that.
Mark
Good point, but maybe the OP's description of the bulkhead is not accurate as to being "water-tight." The forward bulkhead of an engine space is normally full of holes for electrical cables, fuel lines, and a dozen other items. A true "water-tight" bulkhead would have to have all those items passing through conduit/cable connectors and hose/pipe fittings along with the sides and top of the bulkhead being sealed to the hull.
- - Quite a few catamarans I have worked on had the engine compartment located underneath an aft bunk/bed with large panels/doors that open upwards to access the space. So this area is a long way away from being "watertight."
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Old 02-11-2011, 07:41   #20
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Re: Drilling Holes in Structural Bulkhead

Doesn't this amount to drilling where the stresses are the least and in maintaining the watertight integrity of the watertight bulkhead?
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Old 02-11-2011, 10:36   #21
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Re: Drilling Holes in Structural Bulkhead

Or buy a piece of 3" diameter fiberglass pipe from Centek and laminate it through/with/to the bulkhead. I believe you even restore the panel to 100% of it's original strength that way.

ciao!
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