Straight Thread Thru Hull to NPT Valve

[Q Xopa]

Originally Posted by a64pilot

I guess I’m arguing again, but you can’t screw a nut down an NPT thread all the way with no resistance.
An NPT thread is tapered for lack of a better word, I’ve cut too many of them on pipe myself.
Embedding bronze studs into a G10 plate is fine, but assumes of course that you have not mounted the plate and can access the backside to counter sink it for the screw heads.
Unless your talking actually tapping the G10 and using actual studs, which I guess would be OK, but I’d want the plate to be at least .500” thick myself.

Yes exactly using 'Studs' ie no heads, tapped directly into the G10 backing plates.

But yes, agreed that as you correctly say you need some thickness in the Backing plates to have 'enough meat' to tap into.

But the Backing plates should be 'substaintial' being that their intended purpose in life is to support and distribute the Seacock loads to the hull much more. Ie so they dont get broken off when they are kicked or something falls on them leave a big hole in the hull sinking our boat.

Many just buy bronze bolts and cut the heads off with a hacksaw.

As usual Mainsail has a write up of this https://marinehowto.com/seacock-backing-plates/

Thanks again Mainsail.

[a64pilot]

Why not counter sink screws from the backside of the G10 plate?
It would have to be stronger, you have the head of the screw to prevent it from being pulled out.

Actually I think I would epoxy in a threaded insert, the greater diameter of the threaded insert is way stronger, yet the stud is still easily removable.

Just read Maine Sails article, he is using 5/8” which has way more “meat” to hold a stud than 1/4” does.

[Q Xopa]

Originally Posted by a64pilot

Why not counter sink screws from the backside of the G10 plate?
It would have to be stronger, you have the head of the screw to prevent it from being pulled out.

Actually I think I would epoxy in a threaded insert, the greater diameter of the threaded insert is way stronger, yet the stud is still easily removable.

Just read Maine Sails article, he is using 5/8” which has way more “meat” to hold a stud than 1/4” does.

Yes sure, that would fine. The only disadantages I could see are that once the backing plate is glued to the hull there is no getting the screws back out if you needed to replace them in the future.
Also I havent looked but can you get countersunk head silicone bronze screws?
To me the best way to do this would be the aircraft way, using a composite potted threaded insert instead of threading directly into the backing plate fibre glass.
But this is probably overkill. Where does it stop?
Peraonally Im just going to thread it into the backing plate fibre glass.
Keeping this all in perspective this is way better than 98% of the boats out there. Most of which dont have issues.

[s/v Jedi]

Originally Posted by a64pilot

Why not counter sink screws from the backside of the G10 plate?
It would have to be stronger, you have the head of the screw to prevent it from being pulled out.

Actually I think I would epoxy in a threaded insert, the greater diameter of the threaded insert is way stronger, yet the stud is still easily removable.

Just read Maine Sails article, he is using 5/8” which has way more “meat” to hold a stud than 1/4” does.

It’s always possible to make something stronger, but for a 3/4” seacock, I feel that tapping 1/4” G10 for a 1/4” machine screw is plenty strong. G10 is much tougher than people think. I don’t think that countersinking from the other side makes it stronger as the removal of material eliminates any gain from having the head of the screw behind the plate.

For seacocks 1-1/4” diameter and up I would go to 1/2” G10, which is probably twice the tensile strength of the hull

[HopCar]

My gut feeling on this is that 1/4” is too thin unless you bolt through the hull as well.

My choice would be to use the Groco Backing Block. It is 1/2” thick and uses threaded inserts pressed into the back before it is glued down.
https://www.groco.net/products/valve...backing-blocks

[a64pilot]

The Groco BB seems good, especially as its ready to go.
However, I wonder what PVC foam is?

[Q Xopa]

Originally Posted by a64pilot

The Groco BB seems good, especially as its ready to go.
However, I wonder what PVC foam is?

Im sure the Groco ones are good as they make quality stuff.
But for half the cost, $30, and twice the thickness of solid fibre glass these might be ok https://dreamgreen.org/order-here/vi...category_id/18 ?