Puffin - work in progress

[Subculture]

Would it not be better to make any parts that are subject to torque and shear from something a bit tougher like solid plastic or composite sheet. Or use something like SLS or MJF printed nylon?

[Occupant]

Started with ABS-GF print first with printed TPU seal - leaked, commercial o-ring - leaked. so thought it was the print leaking? Came across CPSdrone on Youtube. they used Dichtol to seal printed parts. contacted the company and at the time they didn't sell to the general public and it was pricey. Pivoted to a resin print - ABS like resin. tightening down on the gasket cracked the flange off the part. it hadn't dawned on me that the increased strength comes with increased brittleness - like a piece of glass. Frustrated thought about the Dichtol again and on a whim searched it on Amazon - what, its available??? still kinda pricey but works.
Another idea would be to use a washer plate and nut plate (both shaped like the gasket) sandwiching the two WTC halves against the gasket and spreading out the load vs point load at each screw, wish i would have thought of that earlier.

So to further troubleshoot the two possible leak paths are the ballast inlet tube and the gasket seal. For the ballast inlet connect to the ballast syringe vs plug hose end. As for the gasket two things to do here measure the gap around the gasket to try and ensure a uniform squeeze on the gasket. if that still seems to be the issue may have to sand and reseal the surfaces that interface the gasket (hoping the gasket is soft enough to conform and seal) it could be enough of a peak or vallet that could create a leak path past the gasket. .


FYI
Nylon is a highly hygroscopic material that absorbs water (up to 8%+ at saturation), causing significant changes in its properties. While it remains durable and, in textile form, quick-drying, water absorption leads to increased flexibility, toughness, and part size, but reduced strength and stiffness. It is not recommended for high-precision, submerged applications without consideration for dimensional shifts.

[Subculture]

I wouldn’t worry about hygroscopic properties of Nylon for a part like that in a model sub. For one they're not submerged for very long, and secondly the tolerances are fairly modest. Something dunked in the drink 24/7 is another matter, although these materials have been successfully used for the latter without any ill effects.

I’m sure a plate to distribute the bending load will help a lot.

[RCSubGuy]

Also recall that ABS parts can be vapor smoothed
with acetone, creating a perfectly sealed surface. I, personally, have not had an issue with leaking filament parts. Leaks are usually caused by part interfaces, not the parts themselves.