Plastic thruhull and Sika-291i

[Wideocean7]

Originally Posted by vladkri

If I use Sika-291i to install Tru-design thruhull + ball valve on FG below water do I need to pre-treat surface with one of their aktivators? If yes, which one? They don't really say anywhere. Neither Tru-design, even though sika-291i is on their recommended sealant list. Thanks.

Back to the original post. I installed 3 TruDesign skin fittings a couple of years ago. Spoke a number of times to TruDesign about sealants to use and ended up with this process:
1. Sealed the skin fitting with 3M 5200 and let cure.
2. Installed and sealed an 18mm high density/impermeable backing plates inside. (Mine is a 6mm hull and benefits from a thicker base plate)
3. Installed TruDesign load bearing collars and ball valves using 291i as the thread sealant.

As much as I recall, TruDesign recommends 5200 or similar for bonding/sealing the skin fitting. Then 291i for thread sealing - not for bonding the skin fitting.

Hope this helps.

[Franziska]

Originally Posted by Wideocean7

Back to the original post. I installed 3 TruDesign skin fittings a couple of years ago. Spoke a number of times to TruDesign about sealants to use and ended up with this process:

1. Sealed the skin fitting with 3M 5200 and let cure.

2. Installed and sealed an 18mm high density/impermeable backing plates inside. (Mine is a 6mm hull and benefits from a thicker base plate)

3. Installed TruDesign load bearing collars and ball valves using 291i as the thread sealant.



As much as I recall, TruDesign recommends 5200 or similar for bonding/sealing the skin fitting. Then 291i for thread sealing - not for bonding the skin fitting.



Hope this helps.

I don't get this bonding the skin fitting business.

You have a thruhull with two flanges.
Sealant on both flange inner faces and, if you want on the last cm of thread closest to the flange, screw together whole holding the outside fitting firmly.

Where would the fitting ever go, where would the sealant ever go? The sealant just keeps the water out, it will not get washed out.

In Europe many many thruhulls are installed with Sika. Zero problems.

[vladkri]

Ok, just to keep this going. How about common notion "hand tighten, come back tomorrow and make another 1/2, 1/4 whatever turns"?
Also, what is to be used on hose barb thread to be screwed into the ball valve? How about Permatex blue pipe thread sealant ?

[Fuss]

Originally Posted by Franziska

In Europe many many thruhulls are installed with Sika. Zero problems.

3m 4200 is a superior product.

Actually there are often much more than zero problems….put your boat back on the water between 4 days and the sika never sets

[team karst]

Forespar type 93 seacock decent?

[s/v Jedi]

Originally Posted by team karst

Forespar type 93 seacock decent?

Yes and passes ABYC tests.

[team karst]

Originally Posted by s/v Jedi

Yes and passes ABYC tests.

My genset will be happy to hear that!