I noticed that the buckhead between the cockpit and the rear compartment was leaking. Further inspection it looks like someone patched it in the past and slopped silicone everywhere.

Searching the board I didn't really find any info that helped me look for the correct silione. Should I be looking for a certain type of silicone ? Or will any premium brand from the hardware store work ?

My prep was going to be scrap all the old silicone off and use acetone or something to clean the area before reapply new silicone. Again my boat is a fiberglass solstice gt and the bulkhead is abs plastic it looks like.

Am I missing anything ?
Beyond don't stick my head in the hatch while using the silicone

Camshaft,

Hull flex likely overtaxed the adhesive and it failed. You need a better adhesive/sealant.

If the existing sealant/adhesive is really silicone, you're screwed, because it contaminates the surface so that nothing will stick to the residual sealant. Acetone won't clean it off. Neither will solvents like windsheild adhesive remover (pretty much the death star of removal solvents -- and toxic to breathe). The only good way to seal the bulkhead is to first abrade the hull (and the bulkhead surface where you want bonding to occur) past the silicone layer and expose fresh material. We're talking 60 grit, worked hard on each surface, followed by a thorough vacuuming and soapy water scrubbing, with a clean water rinse, and thorough drying.

Then get a non-silicone caulking compound from the hardware store such as Lexel or Flexx which is reputed to retain flexibility and remain rubbery. A good building goods outlet (not likely Home Depot) should have a paint/caulking geek who will know what to recommend if neither of those two is there. Details on surface prep, from the Flexx people: http://www.sashcosealants.com/home_impr ... flexx.aspx

You could also use 3M's 4200, but it will be totally nasty to remove later and is way overkill for this application.

thanks Dave.

Looks like I'm going to have to use silicone again because the bulkhead has a flat section that I can't reach. Unless I removed the whole bulkhead and sanded the areas etc.
Give it a whirl and see how long it lasts

Just infiltrate the sandpaper between the surfaces and drag it back and forth, then flip it over and repeat. Surface prep is everything on gluing. YMMV.

Well the last person went hog wild on the silicone not sure why you need to go 3-4 inches away on the bottom of the hull.

Here is a trick to use when working with silicone:
Clean up and work silicone into joint with paint thinner on a rag. In most cases you will be able to wipe away almost all of the silicone and still achieve a good seal. It takes only enough silicone to fill the gap to make a seal.
If your bulkhead is moving, then apply a structural bead of sealer only after the seal is water tight. Water test with a slow running hose.
I think the first sealing attempt just missed the leak.
Good Luck,

Roy

I've heard horror stories about kayaks being sunk because of siliconed-in bulkheads being torn out completely from the pressure of having water on one side (ie cockpit) and nothing on the other. I haven't seen it first-hand, but from my point of view, a bulkhead's primary purpose is to create a water-tight seal between one compartment and the other. I would not want to use anything that may jeopardize that seal. The fact that you have to re-seal them every so often is proof enough for me that this is not a reliable way to create that watertight seal.

Since you have a fibreglass boat, and assuming you're planning to keep it, I'd suggest investing a bit more time and effort into removing any silicone (or other sealant) residue, make a new fibreglass bulkhead and glass it in. You really only need to glass in one side, but if you're really serious about it, it's not much more difficult to do both sides. I have a few photos around from doing just that myself recently (I now use the bulkhead as a foot rest as well, instead of adjustable foot pegs, and gained valuable storage space at the same time in the front hatch while reducing the floodable area of the cockpit). Eventually I'll compile them into a little 'how to' article to be posted on this site. But if you'd like a bit more info, I'd be happy to help in the meantime.

thanks mark

very good point
Which is why I posted the thread was it seemeodors or cheap to silicone in the bulkheads. As silicone really is a great water sealer but not something I would use for structure. So it seemed out of place to see both my bulkheads silicones in

You are right it's not that hard to glass in the bulkheads and have a proper structured bulkhead. As I wanted to do something with the front one. As I have way to much wasted space in the cockpit. I will have to get that info from you. As the bulkheads are abs plastic and glass should have no problem sticking to it. My only concern is moving the bulkhead the bulkhead will no longer be the right size

camshaft,

Several builders who have summarized their builds here have moved bulkheads from a standard location towards the center of their boats. I suspect that if you search in this part of the site for "bulkhead" those threads will come up. Not hard to determine the outline for a new, larger size; several ways to do it.

Mark's concern about a blown bulkhead is valid, although that will require a pretty good hit. Minicell foam or ABS are good choices for bulkheads in glass boats, because you want them to flex a little as the hull changes shape slightly in use. Many stitch and glue plywood boats have rigid bulkheads (Pygmy boats, for example), but the greater stiffness of sng ply boats dictates much lesser hull flex in use.

In a glass boat, I'd stick to ABS or similar.

If you move that bulkhead off the silicone treated area, life will get a lot simpler.