Source for Fly High in-sac female fittings?

[IDBoating]

I've read of people adding fittings to existing fat sacs, which implies they have found somewhere to purchase the in-sac female fittings. I can't find them listed on Fly High's website. Where are those available?

(No, I'm not adding fittings to fat sacs. I need the female side of this connection for a project we're working on. The threads are NPStraight rather than the normal NPT style and I need to make certain they match.)

Thanks!

[chpthril]

They are not technically a retail part. I've never asked if they are available.

[IDBoating]

Yet I've seen threads (maybe even here on TO) and videos describing doing exactly that. Discussions about how to glue them in while making sure you don't glue to the opposite side of the bag by accident, etc. That means the fittings are available somewhere. Maybe not from Fly High... do they buy those off the shelf from someone? Maybe we can identify the OEM.

[chpthril]

The fittings ive demonstrated putting into a sac, have been a thru-hull fitting with an internal flange and external threaded on flange, and mate to the female quick connect. So im not much help beyond that.

[IDBoating]

Hmm... I presume the internal threads on the ones you use are NPS, to match those on the screw-in fittings? That's the real challenge, finding matching female fittings with NPS threads. Most things are NPT. We need female threads that are NPS to match the ones on the Fly High fittings. Maybe the fittings you're using will work for our purposes.

[gumby]

I am not Sure what you are working on. Electrical rigid is (what you cal)l NPS. Females don't have the taper. The males do. Thinking back to a project I did over the summer. ( stacking bags) If I remember right fly high wasn't NPT exactly.(national pipe thread)

[IDBoating]

Hey, you're right! I forgot that EMT is NPS. Are there female fittings for EMT? Off the top of my head most EMT fittings are male and used with those nuts that you tighten with a screwdriver and hammer. I can't think of anything in EMT that has actual female threads.

EDIT: Looks like there are female-female couplers in EMT. I just need to take a Fly High male fitting (like a Wally plug) to the hardware store and see if Fly High was smart enough to use standard 1inch NPS threads. Thank you for the reminder on the EMT conduit!

[gumby]

3473784C-1F5D-4598-9CAC-FF937EF21A52-1000.jpg
I can save you a trip to the store give Me a min watch for the edit. My memory was good they don't thread together. The thread pitch seams to be right the size is like mm.

[gumby]

He gone. couldn't wait. While we are here and I got the crap out This is a stacking bag fitting.

[chpthril]

My fittings do not have internal threads, just a male quick connect. The fly high threads are .75" straight, not pipe and not garden hose.

[gumby]

so this is what i remember you can thread a 3/4 NPT into the bag but if you feel it the treads pitch is good. BUT it doesn't really fit. it is to loose If it had an o ring it might seal but it is not right. I determined that the tread pitch is the same as NPT but it is MM size.

[IDBoating]

The fly high threads are .75" straight, not pipe and not garden hose.

I wasn't sure if they were 0.75 or 1.0, but they're definitely NPS.

For the benefit of others who read this thread years from now: There are two (really, three but let's not get into the really obscure "fuel" threading) styles of pipe threading. NPT is National Pipe Tapered, the pipe threads most people are familiar with that get more snug as you tighten them together. That's what you see on plumbing pipe in metal and plastic, black gas pipe, etc. NPS is National Pipe Straight, which many people have never encountered, but if you've ever installed a thruhull on a boat they are what the OD of the thruhull uses because the thruhull has to accommodate a wide variety of unknown hull thicknesses. NPS threads do not get more snug as you "tighten" them; they just spin and spin being the same over the whole length of the threading. Note this also means they don't ever make a liquid or gas tight fit, so if that is necessary you have to accomplish it with (for example) 3M 4200 or 5200 marine sealant as mentioned repeated here on TO.

The fittings on Fly High fat sacs use straight threads because they spin freely until the hose fitting seats against the sac fitting, using an o-ring to become watertight. I presumed they would be a standardized American pipe standard, but based on gumby's tests above that's apparently not the case. "The nice thing about standards is there are so many different ones to choose from."

(WRT chpthril's comment, garden hose is - for some unfathomable reason - different yet again from both NPT and NPS. Once again, "The nice thing about standards is there are so many different ones to choose from." So there's four thread "standards". How convenient, eh? Reminds me of the freakin' oddball weirdo 1-1/8th bilge hose size, a size found nowhere else in the world of hoses. I've asked Engineers at hose companies and they too are utterly baffled why anyone ever did such a thing. 1.0in and 1-1/4in are standard hose sizes in every kind of industry you can think of... why this weird intermediate size that is compatible with nothing else?!? Grrrr. But I digress.)

you can thread a 3/4 NPT into the bag but if you feel it the treads pitch is good. BUT it doesn't really fit. it is to loose If it had an o ring it might seal but it is not right. I determined that the tread pitch is the same as NPT but it is MM size.

Gumby, I'm confused. You say the thread pitch is good, and NPS always feels a little "sloppy" because they don't cinch down as you spin them. Why do you think the "thread pitch is the same" but "it is MM size"? Is it just because they don't snug down?

[IDBoating]

OK, I've run some tests here with real parts (all PVC). Here's where things stand:

* Fly High sac fittings are NPS (straight) female.

* As chpthril said, the Fly High fittings are 0.75in.

* An NPT male threads into the Fly High fitting and never stops - it never snugs down. This makes sense because the "top" of the NPT threads should be the maximum diameter for that size of National Pipe thread, and taper toward the "end", so the end should fit easily into an NPS fitting and the top of the NPT threads, despite being wider than their starting end, simply properly fit the NPS threads. This is exactly what happens.

* An NPS male thread (in this case, a Fly High Wally Plug) will not even properly start in an NPT female thread. You can sort of engage the first few degrees of the threads but the fittings are forced out of coaxial alignment almost immediately. Force-twisting them further will damage the threads on one or both pieces. This makes sense because the NPT female is expecting a tapered starting end, which the NPS does not have.

From the above, I conclude that Fly High's female fat sac fittings are 0.75in NPS threads. You could use NPT males in them but you'd be relying on just a few threads for all of the strength, since the tapered end of the NPT male would not really be engaging the NPS female threads. And like the Wally Plug's own NPS threads, you'd need an o-ring to achieve any sort of watertight seal.

Also, if you mesh the Wally Plug's NPS threads with the "base" of an NPT thread, they mesh perfectly. Naturally, near the tapered end of the NPT threads, they don't mesh very well. But toward the top of the NPT threads they mesh tightly - just as you'd expect.

So after all this, I believe we've basically proven what gumby suggested earlier: That standard NPS fittings should work with Fly High threads. It sounds like he had some issues with the metal EMT (conduit) threads, but I wonder if that's because he was mixing metal and plastic. I've run into trouble doing that, even with NPT threads, because if anything is out of alignment or the threads are imperfect in any way, the metal side starts acting like a tap-and-die set and cuts (damages) the softer plastic side. What do you think, gumby... could that explain why your metal-to-plastic experiment had trouble while my plastic-to-plastic experiment threads perfectly smoothly?

[IDBoating]

Here's a question: Is there ANY fitting available from Fly High that has their female threads? I can't find one but every listing I look at is missing at least one fitting I know is available from them, which makes me wonder if there are others missing too.

Put a different way: Does Fly High sell any fitting that would ACCEPT their own Wally Plug?

[chpthril]

let me look through my bins in the AM. I have some fittings that I think are not listed on their site.