A bulkhead is a vertical wall located inside your kayak that runs from the hull up to the deck. This wall creates spaces of air that give you a place to store your gear as well as help keep your boat afloat. When you take your new kayak home from the store, these bulkheads are sealed to the hull and deck. Sometimes the manufacturer seals them well. Other times, not so much. After many hours of paddling on the water, the seal on your bulkheads inevitably begins to wear away and require re-sealing. This article describes how to re-seal a kayak bulkhead in 10 actually-easy steps.
To re-seal a kayak bulkhead: 1. Mark the location of the bulkhead, 2. Remove and clean the bulkhead, 3. Clean the kayak interior, 4. Apply acetone, 5. Etch with sandpaper, 6. Vacuum grit, 7. Apply acetone, 8. Apply sealant to hull (contested), 8. Insert bulkhead, 9. Apply fillet of sealant to both sides of bulkhead, 10. Let cure.
This article provides instructions to remove and then replace a bulkhead. When a bulkhead joint springs a leak, some paddlers choose to simply apply sealant over top of whatever other dirt, debris, resin, silicon or other sealant is already there. I don’t.
If a bulkhead leaks, my preference is to fix it properly.
Secure your kayak and let’s begin.
Table of Contents
Mark the location of the bulkhead
I’ve found it useful to mark where the bulkheads are positioned before you move them. Take a construction light and insert it in the cockpit or storage cavity of the boat. The boat should emit a warm glow that allows you to identify the exact location of the bulkheads. Take a non-permanent marking tool and mark the edges of the bulkhead on the **outside** of the kayak deck. Now you’ll know where to return the bulkhead, when the time comes.
Remove and clean the bulkhead
The next step to re-seal a kayak bulkhead is to remove it from its current location. If your kayak has many miles on it, then you might be able to pop the bulkhead out with only a slight push. If much of the old adhesive remains in place, then you require a super-technical kayak repair tool – a foot long piece of 2×4 that you probably have kicking around your garage or workshop. Use this sophisticated tool to repeatedly tap the bulkhead until it dislodges. (It will probably be easiest to reach the bulkhead from the bow or stern cavity, rather than going in through the cockpit.)
Let the bulkhead dry. Once the bulkhead is dislodged, it will likely be wet and require time to dry. Give it the time that it needs.
Remove the brittle sealant from the bulkhead. When dry, note the brittle gunk that remains attached to the bulkhead exterior. All of this cruddy yuckiness must go. Remove what you can with your fingers. Use a razor knife to remove whatever remains. In doing this, you necessarily cut into and expose virgin foam. That’s ok. The goal is to make sure the microcell foam is clean, free from debris and able to accept sealant.
Clean the kayak interior.
With a headlamp on your noggin, place your face in the cockpit of the boat and look down its length in the direction of the removed bulkhead. What do you see? Most likely sand, dirt, small pebbles and perhaps a couple of leaves or twigs. Hopefully that’s all there is. Whatever you see needs to go.
Vacuum and wash the kayak interior. Using the hand-held attachment of your vacuum cleaner, proceed to suck up all the debris between the cockpit and the end of the kayak. Then, use water and a mild detergent to clean the hull and underside of the deck – focusing particularly on the area that will later receive the bulkhead. When repairing a fiberglass boat, it’s best to avoid dish soap which, despite what the commercials say, is not actually great for ducklings covered in tar, or kayak finishes.
If you are pressed for time, then towel dry the now-clean kayak. If your pace is more leisurely, put the kayak in front of a fan and go watch an episode or two of Community.
Use acetone to further clean the site
If you leave an acetone-drenched rag on the deck of a polyethylene boat, you’ll find a nasty stain upon your return. Don’t do that. That said, acetone is very effective at cleaning lingering oils or petroleum residue that reduced the adhesion of sealants. If applied with care, acetone is a worthy tool in the process of re-sealing kayak bulkheads. (I wrote an entire article on protecting your kayak hull here.)
Apply acetone to bulkhead area. Put on polyethylene gloves for this job. Then, apply acetone to a rag. Using the rag, clean the areas of the hull and deck that come in contact with the bulkhead. This shouldn’t take too long. Still, be sure your space is well-ventilated and that you don’t keep your head jammed into the cockpit for an extended period of time. If your work area has a fan, keep it pointed at your boat.
Etch the bulkhead area with sandpaper
For one reason or another, many kayak manufacturers don’t etch their boats before installing the bulkheads. Perhaps the reason is aesthetics. Perhaps something more. Nevertheless, etching is an important step in re-sealing a kayak bulkhead. It prepares the surface of the boat to accept and hold sealant.
Roughen area with sandpaper. Using 60-80 grit sandpaper, roughen the area of the hull and deck that will receive the bulkhead.
Be sure to etch the hull after cleaning with acetone. Doing so before the acetone risks driving any lingering oil or petroleum residue into the hull, which would negatively impact adherence of the sealant.
Vacuum the grit
Following the etching process, vacuum the residual grit that has collected on the hull.
Clean with acetone (again)
You really want that bulkhead to be properly sealed, right? Then clean the etched area one more time with acetone. Do it along the entire hull and deck bottom. Make sure the surface is super-clean and ready to receive the bulkhead.
Apply sealant to the hull (some don’t agree)
First, choose a super-flexible sealant. To properly re-seal a kayak bulkhead, you must select an appropriate sealant. What does one use to re-seal a bulkhead? If you paddle a polyethylene kayak, then your boat will experience a lot of flex. The sealant you choose must be up to the task of withstanding significant flex while still maintaining adhesion to the bulkhead, hull and deck.
Use Lexel by Sashco. Read about it here. It’s super-clear, tough, water-resistant (obviously) and can handle up to 400% joint movement (according to the interwebs marketing). In my experience, Lexel is very flexible and an effective bulkhead sealant.
Some paddlers use plain silicon. Others use Marine Goop. Others still, use 3M 5200/4200. Try them if you want. For me, I haven’t found anything that adheres to kayaks (polyethylene in particular) better and is more flexible, than Lexel.
Technically, polyethylene can only really develop a reliable bond with the application of heat and another polyethylene surface/patch (thermo-welding). Some of the best characteristics of polyethylene are derived from its completely inert character. It resists chemicals and does not leech plastic. This is the reason the tips of caulking guns are polyethylene. So in reality, you can’t ever expect immaculate adherence by your sealant of choice.
With all of this said, the combination of Lexel and the force of a bulkhead wedged between the hull and lower deck is, in my experience, the best combination to keep water from flowing between kayak compartments.
Apply the sealant to the hull and lower deck. Many don’t agree. This is a hotly contested step among those that discuss how to re-seal a kayak bulkhead. Some paddlers believe that the bead of sealant gets pushed out of the way and does not provide an effective seal. I party agree. Some of the sealant does get pushed out of the way. However, I believe a sufficient amount of sealant remains and that it creates additional adherence and stability.
Apply Lexel to the kayak slowly. If you have selected Lexel as your sealant-of choice, you need to move slowly. Lexel does not flow at silicon speed. It flows at Lexel speed. Which. Is. slow. If you move too fast, bubbles form.
Apply sealant to the cleaned and etched area of the hull and lower deck. If you choose to apply sealant directly to the hull and lower deck, then do it. Apply a bead slowly in the middle of the area that has been etched and chemically cleaned. It won’t be a perfect bead because Lexel can be a little difficult to work with. That’s ok.
Insert the bulkhead.
It’s time to re-insert the bulkhead. Place the construction light back into the kayak through the cockpit.
Make sure the bulkhead faces the same direction that it did before you removed it.
Force the bulkhead onto the bead of Lexel. It will likely be easier to perform this step from the bow or stern hatch opening than from the cockpit (especially with that hot construction light kicking around).
You’ll know when the bulkhead is properly positioned because it will line up with the lines that you drew on the outside of the kayak deck at the beginning of the process.
Apply a fillet of sealant to both sides of the bulkhead.
If you elected to apply a bead of sealant to the hull before re-placing the bulkhead, then the sealant fillets will serve to further solidify the bulkhead.
If you chose to not apply sealant to the hull, then this step is particularly crucial in making sure that you create an air-tight seal.
A fillet is a layer of sealant that covers the outside of the joint between the bulkhead and the hull/deck. It simultaneously connects with the bulkhead and the kayak with the purpose of keeping water from flowing under the bulkhead.
It is necessary to apply a fillet of sealant to each side of the bulkhead. It’s easy to reach the bow/stern side of the bulkhead. If the repair is at the bow, then you’re in for some heartache – especially of you have short arms. Reaching the bow-end bulkhead through the cockpit is hard. If you can’t reach, you may need to create a homemade extender tool to help.
Apply the Sealant to the easiest-to-reach end first. If you are using Lexel, apply it with a caulking gun. Again, remember that it flows slowly and is fussy. Move slowly to prevent bubbles.
You won’t be able to apply a perfect bead. Rather, apply a stretch of Lexel to the joint, making sure that it touches both the bulkhead and the kayak. Using a polyethylene glove, smooth the bead of sealant to ensure an effective joint. (Try dipping your gloved finger in mineral spirits to make the seal look professional.) Continue this process until you have applied sealant all the way around the bulkhead – connecting both the hull and deck joints to the bulkhead.
Apply the sealant to the hard-to-reach end. Next, perform the same process on the other side of the bulkhead, approaching it through the cockpit. You will end up lying on your front and back and side and reaching as far as you can, to complete the task. The finished product on this side of the bulkhead likely won’t look quite as good as the other side. That’s ok. Do your best to create an effective seal between the bulkhead and kayak.
On a side note, this can be a messy process – particularly on the cockpit side. Clean up any rogue drops of sealant with mineral spirits or acetone and a rag. (Don’t leave the rag resting on top of your polyethylene kayak!)
Let the sealant cure
The sealant begins to develop a skin in the first hour following its application. However, the longer you let your kayak sit untouched, the better. Ideally, leave the kayak in place for 24-48 hours.
If your kayak is constructed from rigid fiberglass, then two days is about the right curing time to ensure a sufficient seal.
If your kayak is a flexible polyethylene model, then give the sealant as much time as you can to cure. Because plastic boats are so flexible, you really do want the sealant to be absolutely, perfectly cured before subjecting both boat and seal to the structural movement and stresses of a day on the water.
There you have it. You have re-sealed a kayak bulkhead.
Other thoughts on how to re-seal a kayak bulkhead
Suspend your kayak. Some paddlers that perform their own bulkhead re-sealing hang their kayak on end before starting the task. Their argument is that gravity pulls the sealant between the bulkhead and kayak to create a better seal. The counterargument (of mine) is that this process also pulls the downhill sealant away from the joint. To do this effectively, you need to seal the uphill joints, wait until cured, flip the boat around and then seal the other side of the joints (which are now uphill).
Handling pressure differentials with airholes. Significant differences in pressure occur between the bulkhead cavity and cockpit. This pressure differential puts stress on the bulkhead and can weaken the seal that you spent so much time repairing. To avoid this pressure problem, many paddlers drill a small hole or two at the upper end of their bulkhead, creating an air conduit between the cavity and the cockpit. This allows hot air to escape from the cavity, reducing the pressure differential and ultimately, the stress on the bulkhead.
The problem with drilling a hole in your bulkhead is that water can then flow into the cockpit (or into the cavity, for that matter). In reality, the drilled holes are so small that a kayak would almost need to be submerged before water could flow between cavities. Nevertheless, there are a couple of solutions to this problem.
A small GORETEX patch covering the drilled holes is sufficient to keep water contained and air flowing.
If you really want to engineer your kayak into a next-level machine, Gore also manufactures protective vents that keep air flowing and water at bay. Check out what Gore is doing here.
Warm Lexel in the sun. It can be difficult to dislodge bulkheads that were sealed with Lexel. If you need to re-seal such a bulkhead, let the entire kayak sit in the sun. The heat from the sun warms up the Lexel. This makes it easier to dislodge the bulkhead from the interior of the kayak.
Parting Thoughts
Now you know how to re-seal a kayak bulkhead. This is a task that doesn’t require a professional kayak bulkhead re-sealer, at all. Rather, it simply takes a little bit of time, very little material and a modestly-steady hand. You can do this! In the process you’ll make your kayak safer and keep your bottom drier.