Weight bearing on overly large hatch?

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clemmy

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Hello,

I’m planning a build, no deck as it’s a 1236 but want a subfloor as plans are for night fishing. So I want a clean floor with minimal clutter. With what I‘ve come up with I’m going to have have a large hatch in the sub floor, 21”x23”.

The entire subfloor needs to be the same height, but I will have a bit of room on backside of hatch to stiffen. The hatch will have very solid framing all around the edge, just worried about the large span and standing on it.

Obviously if you used thick enough material you could do it. Was hoping to use epoxy covered 1/2” multi ply plywood for subfloor, but am concerned about deflection/failure across such a large span.

Two ideas I’ve had would be to double up the plywood on the inside of the hatch, giving an extra inch or so along the hatch edges. So a 21x 23” hatch with a 19x21 second piece glued/screw to bottom as a stiffener (so 1” thick with 1/2” thick edges hanging off framing). Or else drop down in thickness of plywood to say 3/8”, and bite the bullet ($ and weight) and do the hatch itself out of equivalent thickness aluminum plate.

The size I’m stuck with, even though I know it’s too broad, so trying to come up with best compensation.


Thanks,

Craig
 
Thank you guys, MrGiggles that was the problem, span will be 23” at max, 21” the other way.
 
clemmy said:
... span will be 23” at max, 21” the other way.
For full strength to the 'support ribs', if they could lie fully across the cut-out and sit on a 'lip' on each side, it would be stronger. Yeah, you'd lose a little of the opening, but 1/2" on each side shouldn't hurt you much. Clearly you'd need to design it to the thickness of your deck and then the hatch material itself.

You'd cut a 'notch' in the L-angle or U-channel rib where it needed to sit somewhat flush onto the 'lip' of the hatch edge. See if you can visualize the concept from the sketch attached.

Hatch.jpg
 
Wow Dale!

Thanks for the effort You put in! I do understand thanks to your illustration. Not sure how’d I’d work the lip of the deck, I’ll have to think on it.
 
clemmy said:
Not sure how’d I’d work the lip of the deck, I’ll have to think on it.
1" wide aluminum strip screwed to the underside of the deck to leave a 'lip' would do it ... but through-bolting using countersunk flathead bolts would be strongest.
 

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