Scupper flap material, rubber durometer ratings etc.

[theFunsmith]

I received my scuppers today. I went with gemlux 845 units, because I will be hosing seaweed, and debris out of the boat regularly, and need plenty of room. To top it off, I scored them on ebay for about half the going rate. I have some plans to optimize their use, including mounting them on angled blocks so they sit at (or just past) vertical to remain closed at rest, instead of parallel to the transom. The deck will be also raised about 3", which should go a long way toward keeping it dry.

My question lies with the flap material. The rubber flaps I received with these scuppers are a very hard material, and I cannot see them either sealing well, or allowing easy flow of water out of the cockpit. I will be making new flaps, out of 1/8" silicone or something else more easily manipulated. I was wondering if anybody has had any experience making flappers, and might share some knowledge. It seems that silicone sheets are readily available in durometer ratings from A10 to A60 and logically, I'm thinking there has to be a sweet-spot. Assuming of course nobody has anything bad to say about silicone as a material.

[mshugg]

I'm going with the Gemlux 845s on my CCP too.  They're beasts.  Will your scuppers be oval too?  I thin k it's a good idea to shim out the flap to plum; may as well let gravity work with you.  You may want to try using the silicone and the stock flap together.  That way, the softer silicone will help with the seal, and the stiffer rubber will keep things flat. 

[RickK]

That's weird - I went to the Gem site and can't find any scuppers.  Google brings me a page that when I click on it, it's blank on their site.

[CTsalt12]

Wow this is some nice stuff, never heard of Gemlux before.  I'll be ordering a new flush fuel vent for sure.  Interested to see these scuppers too.

[Capt. Bob]

That's weird - I went to the Gem site and can't find any scuppers.  Google brings me a page that when I click on it, it's blank on their site.

http://www.gemlux.com/catalog/Forged-Thru-Hulls

http://www.gemlux.com/catalog/Thru-Hull-Adapters

[theFunsmith]

These are the ones

http://www.carolinaboatoutfitters.com/catalog/transom-rectangular-scupper-stainless-steel-p-82168.html

They appear to be factory discontinued, but are available if you look hard enough. They are are super heavy duty, The flapper itself seems to be the only part needing a little improvement. I should be able to handle that part.

[theFunsmith]

I'm going with the Gemlux 845s on my CCP too.  They're beasts.  Will your scuppers be oval too?  I thin k it's a good idea to shim out the flap to plum; may as well let gravity work with you.  You may want to try using the silicone and the stock flap together.  That way, the softer silicone will help with the seal, and the stiffer rubber will keep things flat.

My scuppers will be oval, but after hearing a couple horror stories of scupper plumbing failures on other sites, I have decided to run my deck to the transom outside the knees. My scuppers will literally only consist of transom ports and the (modified) 845 valves. I will have a central cabinet between the knees, but I plan to keep the self bailing feature as simple as physically possible.  My issue with using the stock flapper, it is is so rigid, that I don't have faith in flapping at all. I am also mulling over the idea of a transom-side silicone gasket, the size of the whole scupper bezel and all, caulked to the hull when the scupper is installed. my thinking is, that way when closed, the valve seal will be rubber on rubber.

[mshugg]

Just a thought, you may be overthinking this.  If the flap is too flexible, it could buckle.  Why not try the stock scupper flap, and solve the problems as they come up.  Bottom line, your boat your rules, so ether way, please tell us your results.

[theFunsmith]

If the flap is too flexible, it could buckle.  Why not try the stock scupper flap, and solve the problems as they come up.  Bottom line, your boat your rules, so ether way, please tell us your results.

I got some 1/8" A50 neoprene rubber today to try as scupper flaps. I think it will work much better as a flapper. I will let you know when I get the blocks mounted how it performs for me. I suppose how well they resist buckling has a lot to do with the size of the hole it is covering. I was thinking of making mine with an opening of ~4-3/4"x1.5" which should give me about 3/8" of flap seal on the sides and bottom. I bought a pretty good sized sheet, so if they do work as well as I hoped, I'll have enough to fire you off a set if you come to the same conclusion I did.