Hatches for buoyancy compartments in sail & oar boats

[pez_leon]

I originally published this question on my build thread but got few responses. I'd like to hear from more people before pulling the trigger.

I'm considering creating sealed buoyancy compartments instead of the specified foam-filled spaces on my Seil. These need access for ventilation and inspection and the possible stowage of bulky light dunnage. The spaces I'm most keen to access are the largest tanks, one of which is hilighted in this image:



I'd like to install this hatch on the vertical face of each tank (facing the centerboard case)
https://www.dpimarineinc.com/dph1119

Does anyone have experience with how well those specific hatches seal? It is hard to believe that anything short of a gasketed screw-in will actually be watertight in the event of a prolonged capsize. I have a suspicion that I should go with something like this:
https://www.dpimarineinc.com/DPCAM8

I'd also welcome any suggestions for truly watertight hatches that look less... hatchy.

- James

[Todd Bradshaw]

Point of clarification: You are not looking for watertight hatches, you are looking for airtight hatches. I think I'd stick with the gasketed screw-in style, or some of the hatches used on sea kayaks.

[rgthom]

I put DPI rectangular hatches on my seat tanks, purchased through Duckworks. They did not seal, at all. Generally poor construction, with screws the wrong size and gasket foam not making contact with the seal ridge. I have since replaced screws and replaced the foam with a thicker type. Now they only leak a moderate amount.

I also have some circular hatches, on each of the separate compartments. They seal better, but hand access is tight and only small items fit. The gaskets can fall out if open, and the loose caps are easy to misplace. I consider these only useful on compartments as air circulation caps when the boat is stored.

There are decent rectangular hatches, others have referenced some brands at times, but I have not used any. I think they are much more expensive.

-Rick

Edit - the big twist lock round hatches can be heck of hard to turn. I had one of those, replaced with a push to seal and lever open type. It does not seem very secure.

[Canoeyawl]

I have done that many times, but I use the large round hatches
and for wooden boats I always use black because white looks like Tupperware...
(black seems to disappear)
I use Bomar, they are air tight, more money but mine have never leaked
(Amazon has them)

AA425BD3-5D0F-4FF2-98C4-52FC975E5A88.jpeg

[Todd Bradshaw]

Also be aware that it is very common for airtight sealed compartments to have a very tiny vent hole drilled into the tank wall somewhere. It might be considered a potential leak, but it is there to keep the air inside from heating up in the sun, expanding and blowing out the seams, which is more of a potential danger than a pinhole water leak is.

[Spot]

Also be aware that it is very common for airtight sealed compartments to have a very tiny vent hole drilled into the tank wall somewhere. It might be considered a potential leak, but it is there to keep the air inside from heating up in the sun, expanding and blowing out the seams, which is more of a potential danger than a pinhole water leak is.

Good point. On the small boat with screw in 6" deck plates on the airboxes, I keep them loose until in the water. On my EPS paddleboards I install purpose made Gore vents.

[The Jeff]

I've got DPI 6" round hatches on my boat that have the same 1/2 turn toggling lock and they are not watertight. Probably ok in a capsize, but I found rainwater that collected in the boat worked its way into the storage compartment. I don't have much experience with the screw in types other than an unknown brand on my Sunfish. That one always seemed to be hard to turn and any sort of grit in the threads jammed it up.

One of the only complaints with my First Mate was the recommendation to put a hatch down where water collects which I eventually removed.

[rgthom]

Good hatches can be made, but it does not look simple to get a good seal. PT Watercraft was selling hatches for SCAMPs, are they still in business? There is a link: http://www.ptwatercraft.com/ptwaterc..._Hardware.html

[AJZimm]

I put a bunch of these, in various sizes, in the new boat I just built.
https://tempress.com/store/Access-Ca...izes-p97937196

Haven't leaked so far.

They are very similar in design and construction to the Bomar hatches referenced above, which I had on my last sail and oar boat, and which saw 6 years of hard use without leaking. They were installed on the horizontal deck of the watertight compartments, by the way.

[jpatrick]

PT Watercraft no longer sells the Scamp hatches but they make the plans available for download on their webpage. I made a pair of these for my Somes Sound. They are on a vertical compartment that will likely never become submerged since this boat is not likely to be capsized. Nevertheless, when I built them I wanted to test the concept. So I put together a smaller version on the bottom of a watertight plywood box (about two feet tall) that I made for the purpose. Once the "hatch" was in place, I filled the box with water and left it to sit for a few days. There was a bit of leakage in the seams of the box but nothing past the hatch that was, essentially, the bottom of the box. This was good enough for me so I went ahead and built the type into my boat.

Jeff

[Rob Hazard]

I built a Scamp and used a number of PT Watercraft hatches in the seats, and even copied their gasket system for my custom hatches in the #3 bulkhead. They are dependent on careful installation of the gaskets to make them watertight. In an intentional capsize drill I found that they do weep when they are underwater, but only slowly.
That's fine with me, since I don't expect them to ever be immersed for more than a few minutes. Anything stored in the compartments goes in dry bags if I want it to stay dry.
For the compartments under the cockpit sole I used screw-in Beckson plastic deckplates, and made myself a wooden spanner to unscrew them when they get stuck, which happens frequently enough.

[dalekidd]

Somebody here recommended these: https://stores.armstrongnauticalstor...8-round-white/

I'm about finished my boat. I made my own. I'm using closed cell foam backed with adhesive on my plates. I doubt they will be perfectly watertight, but I figure in a capsize, you'll not be inverted forever and I mostly sail on inland lakes. If I ever take her to the coast or big water, I may be more particular.

[pez_leon]

Thanks all for the great ideas. Plenty of differing opinions! Todd, I appreciate your points on the language (airtight vs watertight) and the wisdom of a pinhole for equalization.
The suggestion of the black color is counterintuitive, but I can believe that just about anything is better than white plastic.
I'm leaning toward the largest quality screw-in type I can get, with the understanding that I'll need to make a large custom wrench for unsticking them.

- James

[Yeadon]

I've used white Bomar hatches for my Hvalsoe 18. No pinhole. Not really needed with the Bomar. Maybe with the screw type. If you're going to use them for storage along with flotation then I'd avoid the screw type - too tough to get in there in a hurry while underway. Too many motions to get it open and closed while you're busy sailing the boat. If it's just an air tank, sure, then screws would work fine.

Bomars actually seem to seal up even tighter when under the press of water. I do capsize drills every year and have noticed this.

I like your boat.

[Ben Fuller]

The round and oval kayak hatches are pretty bullet proof, air tight ( a tiny bleeder hole is common) but not real pretty. Totally functional.

[MT Rower]

DSC08183.jpg

I have had good luck with the Whale TCL-4 hatches not leaking. They work so well I have to be careful to remember to open them whenever I beach on a hot, sunny day. Suffice it to say, I learned the hard way the flotation tank will fail before the seal on the hatch...

[Powerwagon]

Somebody here recommended these: https://stores.armstrongnauticalstor...8-round-white/

I'm about finished my boat. I made my own. I'm using closed cell foam backed with adhesive on my plates. I doubt they will be perfectly watertight, but I figure in a capsize, you'll not be inverted forever and I mostly sail on inland lakes. If I ever take her to the coast or big water, I may be more particular.

I used one of these Armstrong hatches and it is great - you don’t have to mount anything on the boat which makes the hole larger for access as a storage area.

[pez_leon]

An update and a request for some critical eyes. I bought the Bomar hatches and they seem great. They will be mounted on the vertical surfaces of these compartments. You can see their large cutouts on the vertical pieces here:



Were I building the boat according to the kit, the compartments would remain effectively open topped. They'd be filled with foam sheets, then covered over by 18 mm timber seats running from the rear transom up to the forward end of this compartment. The seats would have a large gap between them and the compartment would drain through a limber hole. I'm going to deviate from the plans to make the compartment airtight.

That picture is taken facing forward. To port you see the open compartment; to starboard you see the compartment covered by a dry fit of a panel I made up. My plan is to first install the vertical piece, then install an interior perimeter of thin square stock that will form a cleat for the top to rest on. I'll form nice fillets on all the inside corners and seal the whole space with epoxy, then drop the top onto a large bead of thickened epoxy on the cleats. The timber seats will then rest on the plywood top. Now that it's all mocked up I have a few concerns.

First, that large expanse of flat horizontal surface looks a bit odd to my eye. I guess I'm concerned that it will hold water and promote rot. Is that a concern? Should I make sure the seats slant toward the centerline?

Second, if the top of the compartment remains flat, I wonder if I should somehow relieve or groove the underside of the seat timbers that will rest atop it. They don't need support structurally. They shouldn't be sealed down because I want them removable for refinishing. I guess I probably want airflow under them so that they can dry out.

Any thoughts would be much appreciated.

James

[WI-Tom]

James,

I think your plan is fine. No need to slant the seats--just make sure the boat is not parked level on the trailer and water will run off. Underway I don't see a problem, as nothing on a boat stays too level and you can always sponge it dry while sailing.

My own boat has airtight compartments bow and stern. No need for timber on top of them--just sit on the plywood. If the interior is painted, it won't look bad.

stern.jpg

Alternatively, if you want more brightwork showing, you could make the lids out of real wood (I used radiata pine for my thwarts, which are also sealed compartments), and screw them down bedded in Dolfinite (actually, I used butyl tape, much cheaper). I thought it might be nice to have an adequately waterproof seal that way, but still be able to open the compartment for maintenance if needed. The amount of brightwork adds a nice visual touch without being too much--just 3 thwart tops, gunwales, seat rest, tiller, and coaming--all the rest is painted.

thwarts.jpg

I don't expect the thwart lids to be absolutely watertight, but even in a capsize they will not take in much. Once recovered, the seals will be well above the interior water level.

I used small round pop-out hatches in the vertical faces. Again not absolutely water-tight, but leak only very slowly. I leave them out when the boat is on the trailer for ventilation. They are much easier to open and use than the screw-type hatches, and are watertight enough to keep things dry.

Tom

[rgthom]

The seats on my Walkabout are flat, water can pool up on one side if the boat is leaning. I saw that Drascombes are made with seats that are angled out, and have scuppers to drain. It sounds like a good idea, water would not pool up and less stays in the boat to be pumped or sponged out.

- Rick

[Yeadon]

My experience … during a capsize, the water pressure on a Bomar hatch actually helps it seal even better. Rain, otoh, can slowly soak in if the hatch isn’t mounted flat on a flat surface. (If necessary, you can build up a small landing with thickened epoxy if you’re mounting on a curved deck.)

[stromborg]

Maybe with the screw type. If you're going to use them for storage along with flotation then I'd avoid the screw type - too tough to get in there in a hurry while underway.

I made a little wooden "wrench" at one point to open them up after they inevitably jam up. Not much grip when wet.

[Breakaway]

I agree with Tom, re using screws and bedding rather than permanently gluing the tops down.

Aesthetically, your top panels might be improved by a slight reveal/ overhang and rounded corners and/ or a slight radius corner-to-corner along the long edge. YMMV.

Beckson sells a key to help twist those open if you dont want to build one like Steve did.



Kevin


Sent from my iPhone using Tapatalk Pro

[David Satter]

This is a great company with a nice selection of weatherstrip and trim. Steele Rubber Products - Marine

[AJZimm]

Painting the inside of the compartment white makes it a lot easier to find stuff when the only opening to let in light is a small hatch

[John Meachen]

An update and a request for some critical eyes. I bought the Bomar hatches and they seem great. They will be mounted on the vertical surfaces of these compartments. You can see their large cutouts on the vertical pieces here:



Were I building the boat according to the kit, the compartments would remain effectively open topped. They'd be filled with foam sheets, then covered over by 18 mm timber seats running from the rear transom up to the forward end of this compartment. The seats would have a large gap between them and the compartment would drain through a limber hole. I'm going to deviate from the plans to make the compartment airtight.

That picture is taken facing forward. To port you see the open compartment; to starboard you see the compartment covered by a dry fit of a panel I made up. My plan is to first install the vertical piece, then install an interior perimeter of thin square stock that will form a cleat for the top to rest on. I'll form nice fillets on all the inside corners and seal the whole space with epoxy, then drop the top onto a large bead of thickened epoxy on the cleats. The timber seats will then rest on the plywood top. Now that it's all mocked up I have a few concerns.

First, that large expanse of flat horizontal surface looks a bit odd to my eye. I guess I'm concerned that it will hold water and promote rot. Is that a concern? Should I make sure the seats slant toward the centerline?

Second, if the top of the compartment remains flat, I wonder if I should somehow relieve or groove the underside of the seat timbers that will rest atop it. They don't need support structurally. They shouldn't be sealed down because I want them removable for refinishing. I guess I probably want airflow under them so that they can dry out.

Any thoughts would be much appreciated.

James

The sealed compartments should be fine with a decent hatch in place while sailing.I'd leave them out when the boat is in storage.As for draining the flat surfaces,I would have recommended a 1/2 inch hole at the outboard edges as the chances of the boat being chocked dead horizontal are pretty slim.With the presence of a hole a little higher as it is,I'm not so sure about adding another.

[stromborg]

Thinking a bit more about your hatches.

I'd think about putting two more in, one on each side, maybe even on the bulkhead face. That is going to be some prime secure dry storage space but getting to anything inside them is going to be tough with only one 6" port. Also, having two openings will allow for a bit of air circulation to help dry out any condensation or water that gets in there when you go out and do some capsize testing and forget to tighten the ports down really well...not that I'd ever do something so silly...

[pez_leon]

... you could make the lids out of real wood (I used radiata pine for my thwarts, which are also sealed compartments), and screw them down bedded in Dolfinite (actually, I used butyl tape, much cheaper).

Tom

Good food for thought. Come to think of it, I could also bed and screw the plywood tops I've made. That might be a good middle ground, easily reversed should I realize the error of my ways. My desire to keep the long continuous seat boards has less to do with aesthetics and more with their role in the overall boat. The design is intended to create a very large thwart-level flat surface for sleeping:


I think the easiest way to achieve airtight compartments without re-engineering the whole interior layout is probably just to cover the space with plywood let in flush with the tops of the existing bulkheads. The seatboards will then sit atop that ply.

[pez_leon]

The seats on my Walkabout are flat, water can pool up on one side if the boat is leaning. I saw that Drascombes are made with seats that are angled out, and have scuppers to drain. It sounds like a good idea, water would not pool up and less stays in the boat to be pumped or sponged out.

- Rick

Interesting! Thanks Rick! I'm absolutely not making any holes in the hull at this stage, but I'll bear this in mind for future designs.

[pez_leon]

Painting the inside of the compartment white makes it a lot easier to find stuff when the only opening to let in light is a small hatch

Perfectly timed - I had just been telling myself that there was no need to paint these. No shortcut there, apparently. Thanks Alex!

[pez_leon]

With the presence of a hole a little higher as it is,I'm not so sure about adding another.

That hole was used to bolt the bulkhead to the building jig. I'm planning on filling it with epoxy. I hadn't thought about draining that inside corner with a hole through the bulkhead, but I think you make a good case for it!

Edit to add: Whoops I'm dead wrong. That hole is pre-drilled in the kit and intended for fenders. No reason it couldn't be filled and moved lower to serve as a drain as well.

[pez_leon]

That is going to be some prime secure dry storage space but getting to anything inside them is going to be tough with only one 6" port.

Would that I could! There is precious little real estate on this boat. The horizontal top face of the compartment will be covered by the timber seat. The obvious space to aft on that same vertical face will be occupied in part by a longitudinal beam with cutouts for foot stretchers.
The good news is that it's an 8" plate (not 6") and that I can contort myself into reaching every part of the compartment. I'll just have to stay this limber forever.

Thought come to think of it, I might be able to retrofit a 6" port on that space further aft if I need it...

Thanks Steve!

- James

[stromborg]

Sealed buoyancy chambers



"Decorative" wood bench tops glued down to chambers

This was on my KDI, I miss that boat

[pez_leon]

The vertical pieces are tacked in and will hopefully get their fillets tomorrow. Thanks again, all.

[Aryoch]

Hi -- Long time lurker - here. I recently completed a Seil - still tweaking various things and watching your build with interest.

I did a similar thing - skipped the foam and sealed the flotation chambers. I was worried the 9mm ply might flex so I put support pieces across.

2021_Seil_Build__IMGP1498.jpg2022_Seil_Build_IMG_0289 copy.jpg


I put drain holes in the gunwales supports.

Didn't put seating across the top at all - rather jiggled heights of things so the wooden seats were flush with the top of the plywood chambers. Not sure I'd do it that way again though - it caused complications and probably doesn't look as smart.

2022_Seil_IMG_0486 copy.jpg