Foam bulkheads without glue

I am wondering if it would work to have foam bulkheads that acted like "corks" on a wine bottle.

For example, form fitted (cross-section)and about a foot deep. It would be stiff foam in the middle, and a "squishy" foam on the surface to form a seal.

It would be slid into place until it sealed and then removed for loading gear. (It might also need some sort of mechanism to make sure it stayed "locked" in place (like a strap).

Does this explanation make sense?

I forgot to mention this is for a kayak

Hehe...the fact that's it's for a kayak makes way more sense than what I was picturing.

In theory I don't see why it wouldn't work, personally.
In practice, I think you're right that you would need a cleat or something to lock it in place when installed. I'm picturing a rigid bulkhead with some sort of stiff-but-flexible gasket around its perimeter - maybe strips of conveyor belting or tire sidewall ?

My question would be whether or not something like that would be better than say a 12" or 16" deckplate inside a permanently fastened bulkhead. When I load my kayak, almost everything is in a few dry bags, so the shape would fit through a big enough plate and still be easily retrieved.

In your opinion, what is the advantage of a removable bulkhead ?

CrankyBadger wrote:

Hehe...the fact that's it's for a kayak makes way more sense than what I was picturing.

In theory I don't see why it wouldn't work, personally.
In practice, I think you're right that you would need a cleat or something to lock it in place when installed. I'm picturing a rigid bulkhead with some sort of stiff-but-flexible gasket around its perimeter - maybe strips of conveyor belting or tire sidewall ?

My question would be whether or not something like that would be better than say a 12" or 16" deckplate inside a permanently fastened bulkhead. When I load my kayak, almost everything is in a few dry bags, so the shape would fit through a big enough plate and still be easily retrieved.

In your opinion, what is the advantage of a removable bulkhead ?

Thanks you for the post. Hi guys, Im a newbie. Nice to join this forum.

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Welcome!

No sweat - we love kicking ideas like this around

Yes, Thanks Badger,

"My question would be whether or not something like that would be better than say a 12" or 16" deckplate inside a permanently fastened bulkhead. When I load my kayak, almost everything is in a few dry bags, so the shape would fit through a big enough plate and still be easily retrieved."


I'd like to hear a little more about a "deckplate inside a permanently fastened bulkhead".

Here are my goals:

1) Water tight

2)Doesn't put stress on the boat. The boat might be stressed by a cork-like bulkhead that was to tight. It might also be stressed by a fixed bulkhead that was stiff and thus caused a stress riser.

3) Easy to open/close

4) Light

5) As big an opening as possible (unless a small reduction in size made for superior function overall.)

Thanks.

Deck plates (here's a 12"


In small boats they're often installed vertically in bulkheads specifically to give access to otherwise-sealed compartments.

If a bulkhead is causing a hard point on the hull (I assume this is the stress riser you are concerned about) indicates improper installation/fabrication more than a design flaw.
Happy to help there if your boat is wood or glass. I don't know much about working with plastic boats though.

carbon/kevlar

How would you do it so as not to make a hard spot? What materials,method etc?

Thanks

I'd start by making a pattern for the shape of the bulkhead from cardboard or heavy paper.

Now, once the paper pattern is a perfect fit all the way around the hull, trim off 1/2" so that the pattern is now slightly undersize.

Cut two layers of 6oz E-glass or S-glass cloth and a piece of 12mm DiVinycell foam to this shape.
Now is also the time to cut the opening for whatever hatch you decide to use, even though you won't be installing the hatch flange until the b/h is in place.

You'll also need about some epoxy laminating resin like West's 105/205 to wet out the cloth. You can check out the West System (Gougeon Bros) website for a great epoxy user's manual. http://www.westsystem.com/ss/use-guides/

When you are actually installing the b/h, you use a few strips of foam tape btween the b/h and the hull - that's why you cut the pattern slightly undersize. It then gets glassed into hull with glass tabs that wrap from the b/h to the inside of the hull. This is also done on the hidden side of the b/h through the opening you made for the hatch.

What creates the hardpoints is the edge of the bulkhead being tight the the inside of the hull and not allowing the glass on the outside to flex at the same rate as the rest of the hull. Using this method of tabbing a b/h, you don't have that contact because there's a space all the way around the edge of the b/h.

The tabs holding the b/h in lace are much stronger than any glue you might otherwise glue in the b/h with, although your particular application didn't ask about a fixed edge-glued bulkhead.

EDIT: Just an afterthought here, but the brand names and products I've listed are just to help you source materials locally. Whether you use epoxy from West, System 3, Mas, etc doesn't matter but it needs to be laminating resin and not 5-minute epoxy, casting resin, etc. Same for the foam, but it needs to be PVC-based foam coring and not styrene-based "Styrofoam"

Thank you!

A few questions,

1)What type of foam tape are you referring to? (between the bulk head and hull/deck). Is the idea to have soft foam that fills the entire 1/2 inch space cut earlier?

2)Do you know of any kits/mechanisms/method for making a custom shape hatch? (I would want to maximize the size of the hatch.

Thanks,

Z

The foam tape just goes in as strips to hold the b/h in the center of the opening and ensure that the gap is the same all the way around. You actually want to have air around most of it, not foam tape.

The tape itself is the same adhesive tape that's used for weatherstripping on windows and doors. You can get it at any hardware store, just be sure to get closed-cell and not open-cell so it won't hold water.
You'll need the thickness to be whatever you trimmed off the perimeter of the panel and the width doesn't really matter: an inch would be about the max you'd want. Cut the length to suit whatever thickness of foam core you use - in this case 1/2" (12mm)

Making the pattern -
About the quickest and easiest way I've ever found to make b/h patterns is to use strips of 1/8" doorskin an inch or so wide and a hot glue gun. In your case I don't see why you couldn't cut a corrugated box into wide strips. Lay the strips in place (on edge) as though you are using the to frame the actual b/h. Longer strips are great for flat areas but in your boat I'm guessing you'll need short strips to allow for the shape of the hull and the camber of the deck's underside.

Now, when you've all the way around the circle, you can gently remove the "ring" that you've made and you now have an accurate size and shape for your bulkhead. For smaller parts, it's often easiest to transfer this shape by tracing it onto kraft paper or butcher's paper so you can trim off the margin for the air gap. This will be your cutting pattern for the glass cloth and foam.

The hatch -
If you want to maximize the hatch space, the easiest way might be to cut your foam even more undersize (let's say an inch all around) and make that your hatch. Glass strips of foam core into the hull (like making the stick pattern) around the plane (station) where the bulkhead will go. This will become the flange that the b/h-cum-hatch seals against.
That would give you the maximum possible opening with the hatch remove and still be watertight when it's closed.

There are a few methods of securing the hatch in place, mostly depending on what your access to it is like. If it's going to be a bow locker where you have to reach in past the footpegs to pop the hatch off, you'll want different latches than if it's right behind the cockpit (or between the cockpits in the case of a double)

Great!

Could you point me to a site, information on different hatch securing mechanisms for this type of custom hatch?

Thanks,

Z

You could start by googling the West Marine catalog.

A couple of the big manufacturers for this kind of stuff are Perko and Seadog.

Duckworks has stuff that's specifically geared for amateur builders and DIYers: http://www.duckworksbbs.com/

It might be tough to find an off-shelf-solution that will work as well as something built just for your particular application. One possibility would be to bed a threaded stud in the foam core and drill a corresponding hole in the hatch.

When the hatch is in place, the stud protrudes through the hole and you can tighten it with a wing nut and a fender washer. Several of those spaced around the hatch perimeter will give a gentle but even clamping pressure to seal the gasket and keep water out.

But once again, if you have to reach up into the bow to do it, it'll become a real pain in the arse.

EDIT...Here's a stud from the duckworks site that looks like it should work. It'll go between the foam core and the layer of glass:

Wouldn't the foam core around the edge cause a hard spot if it was flush with the kayak wall? (this could be fixed by making a small space between the foam and the wall right?

Also, what are the dimensions of the fiberglass tabs that cennect the bulkhead/or flange to the hull?

Thanks

No...that's why the foam core is cut undersized - there should be no contact at all between the foam and the hull. The bulkhead is secured by the glass tabbing. I wasn't sure if the explanation was clear when I wrote it, so I'll try and grab some pics in the next couple days.

As for the flange width, that's up to you. You need enough of a bearing surface to accommodate whatever latching mechanism you decide to go with and also enough room for a seal. You also want to have as big an opening as possible, so you'll need to figure out where that line lays once you get to that point. I'd certainly wait until the b/h is made up before making that decision.

If I get a chance in the next couple days, I'll try and sketch a quick isometric drawing and paste it here.