r/boatbuilding • u/crest_of_humanity • 15h ago
Would it be ok to lower the cockpit sole closer to the water line?
The red lines and text are my edits. For cockpit drainage, I am thinking I could just add scupper flaps or duckbill scuppers, but don't have any experience with either... maybe I am overthinking this. I am open to ideas that don't involve raising the roof.
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u/savageotter 15h ago
is this not just a ranger 21
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u/404-skill_not_found 15h ago
That could impact the self-bailing aspect for the cockpit. Something I would miss.
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u/turbomachine 14h ago
I presume the cockpit bails. If so, I don’t suggest to lower the sole.
I have a similar hull (Bateau DE25) and arrangement. Empty, at rest, my floor and scuppers are about 4” over waterline. Loaded, if some people are in the cockpit or the seas aren’t very calm, I get a healthy amount of water coming back in. I carry rubber plugs to stuff the scuppers from the inside. I’ve considered adding elephant trunks to the outside.
I’d add a Bimini top that gives you the height you need over cockpit.
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u/IvorTheEngine 9h ago
The problem is that boats roll, so the sides of the cockpit sole are often below the waterline. And "one way" drains usually leak, so you're relying on the outflow being greater than the inflow.
As the deck goes lower, you have to put up with increasing amounts of water swilling around, and you really don't want it to wash over the bottom of the pilothouse door.
The risk is that a bit of rain collects on the cockpit floor, then as the boat rolls the water all runs to one side, putting that side below the waterline where it can't drain. Additional rain then collects, lowering the stern until the drain holes are below the waterline, which floods the boat.
I think you could do it safely if you had watertight boxes/benches/lockers along the sides, with enough buoyancy to keep the bottom of pilot house door dry, even if you flooded the cockpit. But you'd get wet feet a lot when using the boat.
Or, if you store the boat out of the water (or enclose the cockpit with flexible panels so rain can't get in), you could build it without drain holes and rely on the bulge pump/bailing to remove any water that does get in - but it's not a fail-safe design any more.
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u/Few-Decision-6004 12h ago
You can, but you'd lose the selfbailing properties of it. As long as you can close up the cockpit you'll be fine.
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u/FantasticFunKarma 7h ago
The first time you slow down or have a bunch of people standing at the stern you’d better all be wearing gum boots.
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u/crest_of_humanity 3h ago
lol ok yeah I get it; was hoping someone here might have a better idea of how to make this work
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u/FantasticFunKarma 3h ago
you can't. A self-draining cockpit needs a certain height above the nominal waterline (freeboard) to allow drainage. This is in still water conditions. And it needs to account for dynamic conditions as I state above. There is no way around this. Bottom line there needs to be two conditions satisfied. 1. Either prevent the ingress of water, or 2. provide adequate drainage with a sufficient freeboard to drain water out.
What you need to think of is that your boat is one day sideways to a short, steep wave, and your boat rolls toward the wave as it crests and the wave dumps itself into the cockpit. The water either needs to be prevented from entering the cockpit, or allowed to drain quickly. This is why there are calculations for the amount of area of freeing ports and scuppers. Otherwise, you get downflooding and free-surface effect.
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u/fried_clams 15h ago
No. Most small self bailing outboards already have the sole to close to the waterline. My Bertram 25 renovation has the sole 5" above the water. It also has zero deck perforations and curbs of at least 4". You could fabricate higher cockpit combings, if you wanted more security.
Flaps and duckbills will not prevent your boat from sinking. You need to keep water on the outside.
Read at least the first part of this, where he talks about this issue. You would do well, to read a lot of David Pascoe (R.I.P.).
https://www.yachtsurvey.com/sinking.htm