Best Sealant for wind vane self steering install.

[ErBrown]

Howdy folks,

I'm prepping to install a new Hydrovane in the next couple weeks. I'm on the fence with respect to the best sealant option. Since the two brackets will be thru-bolted to large stainless backing plates, I don't believe there is much need for an adhesive. Though I'm not sure I see much downside to having some as long as it's removable.

The folks at Hydrovane dont recommend any single product and essentially say that anything like Sikaflex, 4200, or 5200 is fine. I definitely wont be using 5200 since I've had to remove a few items that where bedded with it, and while doable...it sucks.

So I'd been leaning towards either lifecaulk or 3M 4000UV, since the heads of the bolts will see plenty of UV. My concern here is I've read a couple threads about failures with 4000, so I'm leaning towards lifecaulk.

Any reasons why I shouldn't use lifecaulk or why something like sikaflex or 4200 would be a better option?

Thanks,
EB

[thinwater]

Sika makes dozens of Sikaflex products. Kinna like sayin' "I'm going to use 3M."

Sika 295 is common.

Actually, 3M 5200 does not bond that well to metals (compared to GRP/GRP), so the differences in that regard may not be so great.

PS did this a few months ago:
Marine Sealant Adhesion Tests - Practical Sailor Print Edition Article

When you read of a "failure" it can be very difficult to ascertain what that means:

* Improper surface prep. Folks prep for paint but most don't even de-grease the bolts for caulk. Have you ever seen anyone solvent wash bolts to remove the cutting oil?
* Too much movement.
* Not all caulks adhere to all surfaces. Check the above table.
* Improper curing conditions. Too cold or too dry.
* Actual material breakdown. Very rare.

My guess is that anything that is rated for continuous immersion will work fine. The fit and backing plates are more important. Keep it from moving and chamfer the holes.

[roverhi]

Have been using LifeCaulk for more years than I care to count. If you counter sink the pukas as Thinwater says probably any sealant will work, however. Don't even think about using sillycone.

[ErBrown]

Thanks Thinwater. Unfortunately, I don't have a subscription to PS, looks like an interesting article.

[Dartanyon]

Any reason not to use butyl tape?
(mostly curious because that's how I attached my monitor)

[thinwater]

^^ I would love to see long-term studies of butyl. It's been used for sewer pipes for 50 years, and I started specing it for piping 35 years ago. I seriously doubt the issue is durability.

The down side is that underwater it is mission-critical, and if the fasteners let go, it's worthwhile to have an adhesive holding the seacock or whatever in place. That may be the determining factor.

[Dartanyon]

Oh, certainly, underwater, I don't think I'd have used butyl. My apologies, I didn't realize that the Hydrovane had any connection points below the waterline.

Originally Posted by thinwater

^^ I would love to see long-term studies of butyl. It's been used for sewer pipes for 50 years, and I started specing it for piping 35 years ago. I seriously doubt the issue is durability.

The down side is that underwater it is mission-critical, and if the fasteners let go, it's worthwhile to have an adhesive holding the seacock or whatever in place. That may be the determining factor.

[ErBrown]

Yeah, I've been considering Butyl as well. Have a couple rolls on the boat and you're correct no part of this install will be below the waterline. Since the brackets will be thru-bolted this seems like a good place for it.

Just seems odd to me that it's not on anyone's recommended list.

I know I'm over analyzing this but figured this install is something I want to get absolutely right from the start.

[thinwater]

I misunderstood.

If it is all above the WL, yeah, butyl is a valid choice. I've used it for through hull drains (above the WL), winches, and hatches. My only question (not knowing the specifics) is whether the sealant needs to carry any sheer load. I bet it does not and that this is a good application.