Duckbills in da aquamaster

[larry]

What causes the DuclBill to be sucked into the hose when inhaling into the mouth piece of a da aquamaster? Anybody hepl me with this as I am new to vintage double hoses. thanks. larry

[Nemrod]

I had never ever seen this until the Florida Sand Dog dive where one of our divers had this happen with his Mistral. Then at the Wazee dive another diver had the same thing happen. There are several ways this can happen. The main one is that the exhaust cage valve in the mouthpiece is damaged or stiff and not sealing all the way allowing a negative prressure to be applied. Another is that some debris may have entered the cage valve again preventing it from sealing. Another is that yanking on the exhaust hose--stretching it might could reverse the duckbill. If your duckbill reverses you may be able to blow it out but do not waste a lot of time with this--that is if actually diving when it happens. You can still breath, just exhaust from your nose or mouth around the mouthpiece, abort the dive and normally surface. Stiff, tired, warped cage valves will leak and prevent proper clearing and functioning of your double hose. Make sure they are clean and soft and that the cage valve--the wagon wheel--is in good shape, not cracked or broken or missing a spoke. You can, if you wish, use a touch of AquaSeal (not silicone or bubble gum or anything else) on the back side of the duckbill and then adhere it to the top case inner surface. Just a small dab will do. You do not want to glue the entire valve to the case, just a little dab about midways. This done there is virtually no way for the duckbill to reverse.
James

[luis]

To create enough suction to reverse the duckbill, I would think that in addition to a faulty mouthpiece valve you would need either an empty tank, a closed tank valve, or a regulator that sucks really…really hard. The early two hose regulators didn’t have mouthpiece valves at all.
I remember it happening at Wazee, but I think it is a very strange occurrence.

[dhaas]

Guys,

I was the diver with the Mistral that had this happen while we were at Alexander Springs. Mounted reg on a full tank, checked it and headed to the water. Tested prior to entry and it was hard to exhale. Then ZERO exhale, and also very hard to even inhale (???)

Walked back up and slapped a single hose on to dive while Bryan took a look at it. (Thanks man...)

He noticed the inverted duckbill right away, popped the can apart and had it working by the time I came back up from diving. Didn't do it since then (reg sold now) but it did have an authentic, very thin duckbill. Chuck Tenge had this puppy tuned to perfection, too!

Could the thin original style duckbill have anything to do with this?

David Haas

[larry]

Thanks Nemrod , Luis and Dave for your help. When I purchased the DA Aquamaster I noticed the Duckbill was very, very thin. So I ordered a couple spares from Bryan and what a difference!!!! Bryan has really nice ones on his web. I changed the Duckbill and it cured the problem. Larry.

[duckbill]

Interesting dilemma.
I guess the Alexander Springs regulator is gone now and it is too late to really analyze the CAUSE, but it seems to me that the hard inhaling should have been given the most serious scrutiny. I know you said that it was "tuned to perfection", but hard inhaling and one-ways in poor condition could have very well caused the duckbill problem as described. Let's hope that it was not due to an intermittent regulator seating problem which may manifest itself on the new owner.
It is also possible that on descending quickly, or with little breathing, that the ambient water pressure increase in relation to the now lower (relatively speaking) pressure in the exhaust hose would also aid in inverting a duckbill. Once inverted, a duckbill would seemingly be nearly impossible to exhale through, or to right by lung power alone.
Any other ideas?

[Nemrod]

I had not thought about increasing depth/pressure causing the duckbill to invert. I suppose if one descended rapidly without exhaling or breathing at all to some depth then the duckbill might be forced inward. I may experiment with that to see what happens. I know I have dived more than 10 feet without a breath and without having the duckbill invert. Hmmm. Whatever, it is fairly rare and Luis did manage to blow it back out with lung power alone at the Wazee dive. James