Sealing a cored hull

US1 Fountain · 12-22-2006, 11:26 PM

I'm installing a thru hull for a A/C water pickup and not sure if the hull is cored or not at the location I'm considering. I'm assuming the whole bottom is????

Fountain has not returned my call with this info.

Is there a way to tell if it is cored or not just by looking w/o drillling a test hole? If it is cored, do I dig out as much of the coring as possible and fill with epoxy? What determines the use of a backer block? I'm not planing on the flanged seacock style that gets screwed thru the hull, but a normal thru hull with a inline valve that screws on top of the thru hull.

And finally, I have to make the thru hull fitting do to a special application, I know bronze seems to be the normal, is there any reason I can't use SS? Fresh water use only.

Any help would be appreciated.
Thanks

US1 Fountain · 12-23-2006, 12:19 PM

Doing some research on the net with the West System. From what I've gathered on working with cored hulls, after drilling the hole, the coring must be dug out (how much additional?) around the hole between the inner and outer layers, then that void is filled with the West System epoxy. Do I need to use any type of filler such as the 404 high density filler, or just the epoxy mixture itself? I'm assuming the epoxy also gives the hull some strenght to prevent the thru hull from squashing the hull when tightened.

Just needing to know if I'm on the right path.

phragle · 12-23-2006, 03:42 PM

yep, you need to clean out a bit of core..not much, just enought to get some epoxy in there to seal it (the coring) and yep you want to use some filler and the epoxy/filler will resist compression squishing better than a balsa or foam core, though you dont really want to put massive amounts of torque on a thru hull..

FX10 · 12-27-2006, 11:58 AM

US! Fountain,
Your hull is layed up with Vinylester resin. IMO, I wouldn't bother with the expence of using West system epoxy. Instead go with Vinylester resin. There really isn't a delamination or strength issue here. It's very basic.
In all reality, there is no need for anything other then 3M 4200 5200 Marine adhesive/sealant. If prepared correctly.
But if you want to go the extra mile. Do what the others said about carving out a little ( 1/4" ) into the perimeter of the hole. Catalizing some vinylester resin and mixing some cab o sil or other filler untill you get a creamy consistancy. Fill the void and wait for it to cure. Sand area, and install Thru hull fitting using either 3m 4200 or 5200. And as Phragle said, you dont want to over tighten the fitting and squeeze out all the sealant. That is a mistake too many people make.Use sealant sparingly. Wipe off excess with Acetone and your done.

Rick

US1 Fountain · 12-27-2006, 04:29 PM

Thanks guys!

FX10 · 12-28-2006, 01:31 AM

I take it.... you got it!! God luck with it.

Rick

US1 Fountain · 12-29-2006, 05:53 PM

Quote:

Originally Posted by FX10

US! Fountain,
Your hull is layed up with Vinylester resin. IMO, I wouldn't bother with the expence of using West system epoxy. Instead go with Vinylester resin. There really isn't a delamination or strength issue here. It's very basic.

Rick

Are you saying the West System is over kill, or not compatible with the vinylester hull? I have a gal. of the West stuff at work and was just going to use that instead of buying new for just a 1/8 cup of material.
I'm waiting on some ordered parts so I can do my layout, then drill the hole in the right spot.

Thanks.

phragle · 12-29-2006, 06:29 PM

you can put west system over standard resin, but not resin over epoxy..im other words epoxy will stick to resing, but resin dont stick to epoxy

US1 Fountain · 12-29-2006, 06:36 PM

So the West system epoxy will stick to my Vinylester resin hull.

Is epoxy and resin just 2 different types of material?

FX10 · 01-01-2007, 03:17 PM

Since you have the West Epoxy, you might as well use it. And yes, it's compatable.

Rick