Exhaust Flex Coupling to Threaded Pipe

[Trés 30]

I'd like to put a flex coupling below the standpipe exhaust but want to be sure it is 100% leak free (to avoid becoming the S/V Asphyxiation). Most flex exhaust is w/o pipe thread so a complete seal seems to be the challenge.

I'm thinking sections of black iron threaded on one end & smooth on the other to clamp flex pipe over (something like the pic); maybe a sealant also (?)

If anyone has some experience w/ this please let me know.

Thanks much,
Leon

[Dave Neptune]

Iffy

Leon, the flex will rust out in very little time unless it is stainless. Frankly you'd be better off using "hose" if the "water" is already in the exhaust at the spot you want the flex.

Dave Neptune

[Al Schober]

I've never seen the need for flex at that point. On my Tartan 30, that's where I put a 3 pc union fitting - more for assembly of the new exhaust than anything else.

[67c&ccorv]

In Dave Gerr's "Boat Mechanical Systems Handbook" he recommends flexible metal bellows made of Iconel or Hastelloy and lastly 316L stainless steel to connect from the exhaust manifold to the exhaust system. (P106-107)

This to avoid the inevitable cracking of the joint from engine vibration.

Such bellows joints are available with threaded ends to fit the A4 but be advised the cost is pretty stiff!

[Mo]

...all valid points above and very true...just go with what is tried and true.

[Trés 30]

Exhaust installed w/ flex

Finally got the exhaust all together (pics to follow). The solution was not quite as clean as I'd have liked, but if it turns out to be a leaky mess I've got a buddy who offered to tig weld it.

If I had to do it again I might order this for $46 + shipping.

This one is nice too but it's $127 + shipping.

[Trés 30]

Here's what I came up with

not real purdy but it's wrapped (and hidden), so what the hey? I used some unions, so maybe removal will be easier (but hopefully unnecessary). A CO alarm WILL be installed, especially since it's my first exhaust job.

67, thanks for the reference to Dave Gerr's book (and some exotic metals), sounds like a great read!
Minimize vibration & flexion stress on the system, yes! Of course I do have B(oat)OCD

[romantic comedy]

Looks good. I am jealous.

Is that paint high heat?

On my tartan 34, I wanted to do something similar, but just did not pursue it. It looks like you are using the same insulation as I used. I used 3 layers and it is still to hot for the cabinetry.

[ndutton]

Is there a vibration issue you're trying to address?

[67c&ccorv]

Well - I guess if it was a diesel!

[Trés 30]

No vibration issue to speak of, just a compulsive overbuilder.

Romcom, that is high heat paint a la MMI. Didn't use 3 layers of (1/8") wrap, so maybe it won't be enough, but will find out soon!!

[Al Schober]

Wow - ceramic tile countertop in the head! First I've seen that in a Tartan 30.
Helped build a 39' 'fast cruiser' about 12 years ago - owner had a granite countertop next to the stove for hot stuff. He got it from the Lear jet people - the granite was about 3/16" bonded to an aluminum honeycomb!

[ArtJ]

Looks good. I am jealous.

Is that paint high heat?

On my tartan 34, I wanted to do something similar, but just did not pursue it. It looks like you are using the same insulation as I used. I used 3 layers and it is still to hot for the cabinetry.

In another post 1 gave a source for solid calcium silicate pipe covering which
would totally solve these worries.

[romantic comedy]

Art, is that what you are using on yours? Do you have the link?

[ArtJ]

I have some of it, as I explained a while back, I only briefly installed it 10 years
ago. I got the information from Tom Stevens who used it for many years
on his Tartan 34 regardless of whether he used a water lift or a standpipe.
the stuff was good. It needed a tape applied over it to keep from shedding
powder. Both the tape and a version of the calcium silicate is in another
post. I located a source which was bigger than 1 1/2 id but I am sure
a little more searching will come up with the 1/ 1/2 inch it. I will find the
earlier post and provide the link again here. All it took was a saw to
easily cut the right angles, some stainless wire and some stainless clamps also
must cover with the tape to prevent shedding powder.
I will repost the links in a few minutes

art