Where to put holes in this bulkhead?

I need to create some holes in small sub deck bulkheads for engine intake. In the diagram basically I'm showing the bulkhead between two stringers, where the deck sits atop and is adhered both the to stringers and the bulkhead.

The bulkheads are not normally there in these boats, probably aren't going to be loaded, just put them in because it seemed right, mostly I think their job is just positively assuring the stringers do not deflect (ie remain perfectly upright) without depending on the adhesion of deck to stringers. And they create deck support too of course.

I haven't been able to dig up any guidelines that deal with this sort of thing but am striving to put the holes in the least impacting places. I feel like the two holes labeled 1 & 2 are the way to go because if anything stresses are compressing on center, and trying to push/pull the tops of the stringers together and apart.

What do you think?

 

Hole, wherever, with rounded corners and a reinforcing fringe.

 

Typically, avoid structural tapes.

 

What does that mean?

 

I'm thinking he means not to cut the tabbing out in the process?

I think I'm basically just going to take a 6 inch hole saw and bore straight on center. That's a touch over the area I need, the bulkhead is about 17 inches tall, and I'll run so many layers of glass around and around inside, really to seal the core, a few sessions at it, sand the edges flush, makes a solid glass sleeve. End up with a hole pretty close to the middle 1/3 the height as far as the hole goes.

 

Not too close to the edges, or each other.
Also, stagger the pattern, and leave a holes’ diameter between holes.
One big hole in the center might suffice.

 

1) Are there enclosed sleeping compartments on board?

2) After you drill the holes for ventilation, where does the combustion air come from. Ie from within the bilge, or from other compartments of the boat?

3) Confirm if the engine compartment is enclosed, with the exception of the air intake and compartment air exhaust of course.

4) What horspower is the engine (engines)? The size of the intake opening is predicated from the manufacturer and if that is not available, there is a table that shows the EFFECTIVE cross sectional area required for given horsepower.

5) Ultimately, you need to have the combustion engine air come from a vent attached to the outside of the hull. ( not from other compartments in the boat though if the attached compartment is deemed to be an
"open to the atmosphere" compartment, PERHAPS this would satisfy ABYC guidelines. ( a side note- why would you want to satisfy ABYC guidelines- a) to keep the boat as safe as you can so that no one dies and b) enable a survey to satisfy insurance requirements)

5b) You will need a duct and vent overboard as well. This is to permit dilution of fuel vapors, co2, co.

6) You will require a blower exhausted to the outside of the boat

 

For other holes, like a stringer where I can find some applicable guidelines I'm using the 1/3 and 2D rules, holes in the center 1/3, holes 2x the diameter spacing minimum (ie so 3 inch holes must be 6+ inches apart).

 

if it is a non-structural bh, there is no reason to reinforce, but you can't leave glass edges for chafing wires or hoses

you can bond in pvc pipe as a chafe guard or make edge protectors with inner tubng to keep things protected from glass

 

I raised the stringers to deck level, adding about 7 inches to the height including the flange you see in the pictures. This took stringers that were 5 to 15 inches tall or so (short aft, tall forward due to both deck pitch and banana bottom of hull combined together) and made them 12 to 22 inches. Bulkheads added here and there, and the deck adheres down to the flange.

Some weight involved but eliminates framing and makes it seriously one structure. But the engine needs to breath somehow. Pilot house and cabin also has AC/heat and is of course enclosed, so engine air intake must be 100% isolated - ie no vents allowed in living space.

Going with 1/2 square inch per HP, has 380 HP gas now but allowing for up to 550 HP diesel. Passages for air are being created where the engine will draw from under gunnels, using various objects that will exist as places to add vents where basically rain won't come in since the opening is a few inches under the gunnel but the engine can intake.

 

Thanks! Because I sand the edges flush after glassing inside its literally a perfect ring in there, nothing sharp, then I gelcoat to match the rest. I think even you guys who are very talented would give it the nod.