Installing End Caps and Fixing End Cap Leaks

One of the great features of our inflatable hulls is the molded high-impact end caps. These protect the hulls from damage from things like rocks or branches in the water. They also have other benefits. One is that if you ever need to patch your hull you can remove one end cap and apply the patch internally. The result is an almost invisible repair.

This page is to show you how to check for and eliminate any slow leaks that may occur around the end cap and also to show you the easiest way to remove and / or replace an end cap should that ever be necessary.
 

Slow Leaks Around the End Cap

The end caps are installed with a bead of silicone rubber (like GE Bathtub Seal) as a gasket. This material shrinks a small amount over a period of several days after the caps are installed. Sometimes that small amount of shrinkage will cause a slow leak to occur around the end cap.

If your hulls are experiencing a slow leak the first step is to determine where the leak is coming from. To do this squeeze 2 or 3 tablespoons of dish washing liquid soap into a cup. Fill the cup up to half with warm water and gently stir and dissolve the soap into the water. With the hull inflated to tight pressure take a small paint-brush or a small rag and gently apply the soap solution around the edge of the end cap. Also apply some soap solution around the bolt in the end of the end cap.

Any leaks will show up as a continuous stream of many small tiny bubbles coming from the leak. Sometimes you may see just one larger bubble that appears to be growing. But the leak is indicated by the appearance of new bubbles or a visibly growing bubble - not by any bubbles that just sit there. These are created by the brushing action. That's why you should apply the soap solution gently - to avoid creating too many of those static bubbles. Again, if there's a leak the bubbles will continue to emerge or grow - don't confuse these with static bubbles that just slide down the side of the hull.

Fixing a Slow Leak

Once you've located the leak fixing it is very simple. Just insert a 5/16" hex (Allen) wrench into the stainless steel bolt at the end of the end cap and give it a 1/4 to 1/2 turn clockwise. That should be enough to stop the leak. If that does not stop the leak completely you can try to tighten the bolt a bit further but don't tighten too much because you can crack the end cap if you crank it too tight.

This almost always takes care of the problem but if the leak is still there after tightening the bolt as described above, simply remove the end cap by removing the hex head bolt and pulling off the outside piece. Then, using your fingers you can peel off the hardened silicone seal gasket. Now, you're ready to re-attach the end cap as described below.
 

Installing the End Cap

The end cap consists of 3 items, the two plastic cones (one captured inside and a loose outside piece) and a stainless steel hex bolt.

Aside from the 3 pieces of the end cap assembly you'll need two more things for this task: an opened tube of silicone seal (GE Bathtub Seal or something similar) and a 5/16" hex (Allen) wrench.

Also, place the stainless steel hex bolt into the end of the outside piece of the end cap. Tap it with a hammer fully down into the hole.

Now, you're ready to proceed.
 

Step 1: Get the inside piece into position.

Each hull has 2 end caps. Each end cap comes in 2 pieces - an inside truncated cone with a brass threaded insert and an outside cone. The 2 inside pieces are placed inside the hull before the last seam is welded. Once they're in there they can't get out because the holes in the ends of the hull are too small.

Locate one of the inside pieces by feeling around until you find the hard lump. Then pick up the hull and shake it so the inside piece falls to the end where you want to install it. Once it gets close to the end you can reach inside and grab it if you need to.

Grab the piece and pull it into position with the brass threaded insert centered in the hole at the end of the hull.
 

Step 2: Grab the hull with your left (off) hand just behind the end piece.

This holds the inside piece in position while you proceed with the following steps. Grip it tightly so it can't move.
 

Step 3: Apply a 1/4 to 1/2 inch bead of silicone rubber.

Place this bead about an inch from the edge of the end hole in the fabric. Go all the way around. Keep holding the end assembly in your left (off) hand tightly while you do this.
 

Step 4: Extra bead at 2 seams.

Now go back and place an extra bead (perpendicular to the circumferential bead) along the seam edges where the gray and blue fabric pieces are joined.
 

Step 5: Attach the outside cone:

Place the outside cone piece (with the hex head bolt already tapped into the cone) over the assembly centering the bolt over the threaded insert. This is a little tricky to get it lined up correctly - but don't let go with your left (off) hand while you do this.

Once the threads are started go ahead and spin the outside piece onto the threaded insert as far as you can by hand.

Just to be sure the silicone seal is well spread around inside there I then back up a half turn and then go forward again to work it around really well. You especially want to be sure to get the silicone seal spread along the seam edges.

Note: Avoid touching any silicone seal that may be oozing out around the edges. Once it's on your fingers you'll get it on everything you touch. If you do get some on the hull let it dry completely (perhaps a day or more) and then just pull the excess off with your fingers. It peels off easily.
 

Step 6: Tighten the Stainless Steel Hex Head Bolt

Using the hex wrench finish tightening the stainless bolt.

At this point I like to inflate the hull and make sure the angle and position of the cone assembly looks good. If not, just loosen the bolt a little and adjust the angle - then retighten.

It will take several hours for the silicone seal to solidify completely so you have plenty of time to adjust things. Silicone seal hardens when wet (or even under water) so you can use your hull right away if necessary. The silicone seal is sticky enough before it hardens that it can't easily be pushed out by the air pressure in the hull.

Step 7: Final Tighten

After a day or so it's a good idea to take another quarter to half turn on the stainless steel bolt to eliminate any small leaks that might appear from shrinkage of the silicone seal as it hardens.