Forward Compartment Leak

[DMTNT]

Gentlemen of the Jury, I'd like to get some community advice if you'd all be so kind. Last night I was doing some function testing / ballasting of my boat with a newly configured 2" SD. There were a few instances where I got it to submerge and then surface, but also a few where (for various reasons) it ended up at about a 45-50 degree up angle in the water, hanging by its nose in about 3ft of water. After a half dozen or so tests, I noticed there was some water accumulation in the forward and aft compartments. Enough to cause a batt-link monitor to stop blinking. C'est la vie on that one, I suppose.

I had the seals greased with a petroleum jelly, which I've now read may not have been the best thing to use - although that was based on a comment in an earlier thread about lubricating servo pushrods. I also noticed there was a nick out of my front end-cap, that could very well be the cause of a pinhole leak. See the attached photo. No idea how it got there, honestly.



After drying everything out, I buttoned-up the aft end, plugged the necessary induction/pump lines, and blew into the open front end of the WTC with it's ass submerged in a bowl of water. Not so much as a bubble. So I'm guessing the leak is coming from up front? I spoke to Bob, who was gracious enough to send a replacement end cap with some other components I've ordered. Of course, my plan is to halt all wet testing until then and use that once it arrives.

My question then, is about leak checking the forward compartment, and how to proceed with testing without getting the insides wet again. Any advice is appreciated. Thanks!


-Brady

[He Who Shall Not Be Named]

That 'nick' is a casting void/flaw. If it does not extend to the o-ring grove, it is of no consequence.

David

[type7]

Yes, the void is on the dry side so shouldn't cause any problems. fill it with epoxy or thick superglue if it bothers you.

[DMTNT]

The casting flaw actually does continue through to the o-ring channel. In fact it’s almost as deep as the o-ring itself. I closed everything up last night and attempted a leak check. The only thing that seemed to happen was the front cap began to dislodge from the change in pressure inside the dry space.

What I don’t understand is how it got water ingress the other night when it was in the pool. Perhaps the cap doesn’t fit snugly enough and the repeated suction/equalization from the SAS system caused it to wiggle forward enough to let in a bit of water?

[RCSubGuy]

SAS is either in a state of vaccum or ambient pressure, not pressure increase. If anything, the ballast system would suck the caps tighter against the tube body.

[Subculture]

You can get a small pressure increase when pushing the cap home, then with the motors running and heating the air, that can further pressurize the internal space. Admittedly the pressure rise will be very small, and water temperature will have an impact on this too, but it could be enough to move the cap a bit. Equalize the pressure inside the wtc with the schrader valve once sealed.

[DMTNT]

You can get a small pressure increase when pushing the cap home, then with the motors running and heating the air, that can further pressurize the internal space. Admittedly the pressure rise will be very small, and water temperature will have an impact on this too, but it could be enough to move the cap a bit. Equalize the pressure inside the wtc with the schrader valve once sealed.

That's a really good point. Whoever thought of that must be pretty damn smart *cough*

You guys are an invaluable resource. Thank you all for the continued advice!

[DMTNT]

Well, I spent the evening trying to trim JC in the tub and came away from it very encouraged, but still scratching my head. The good news is it sinks and rises level, and it will do it over and over. The part that mildly concerns me is I'm still getting water in the WTC. Not a lot, and everything seems to be okay, but after about 45min, I ended up with maybe 10ml of water, distributed pretty evenly between the front and after dry spaces.

The seals all seem to be okay, but I'm a bit lost as to how it's still getting in. Could it be a case of it sucking in water when I blow the ballast tank?

[He Who Shall Not Be Named]

Take a close look at the transparent portion of the LPB pump -- the dry side, between the face of the pump motor and pump diaphragms. Is there water within the pump housing?

David

[DMTNT]

Take a close look at the transparent portion of the LPB pump -- the dry side, between the face of the pump motor and pump diaphragms. Is there water within the pump housing?

David

I’ll have to wait until I get home this evening to do a couple of flood/blow evolutions and see, as it’s all dried out now. I have a fuzzy memory from a few weeks ago seeing some water in that section of the pump. What is that indicating if it’s wet?

I’ve always been a bit nervous that my foam float / rubber seal inside the sail might not be perfect, since I had to do a lot of trimming and reshaping to fit it into the sail. However, every time I’ve dry tested it (by flipping the sail & upper hull and sucking through the induction hose) it consistently makes a solid, strong seal every time. And reshaped as it is, I know that little float still bobs up like a cork when it goes under.

[RCSubGuy]

Not sure if the pump leaking would cause water in both of the two compartments. That doesn't really compute as the only passage between is the wire conduit, and that's raised up high enough that you'd need a lot of flooding to seep over the lip and down it to the other end.

I'm having a hard time thinking of any one thing that would put water in both ends...

[trout]

Unless the bulkheads on each side of the ballast tank are not fully sealed.
Check also when you strap you WTC in if that is flexing your tube and causing a loss of seal from the o-rings.
I found on my Skipjack that I did get a small amount of water spray from the SAS system, but not 10ml more like 10 drops.

[DMTNT]

I'm having a hard time thinking of any one thing that would put water in both ends...

Same. I’m using that new end cap that you sent me too.

Unless the bulkheads on each side of the ballast tank are not fully sealed.
Check also when you strap you WTC in if that is flexing your tube and causing a loss of seal from the o-rings.
I found on my Skipjack that I did get a small amount of water spray from the SAS system, but not 10ml more like 10 drops.

I don't think that it's flexing the tube, as it's still not physically connected to the hull (save for the rubber bands holding it onto the saddles). And maybe 10ml was a bit of an overestimation... but I would put the total amount at at least 5ml.

One thing I wonder if it could be is when I originally constructed the foam float to put in the sail, for the SAS system, the brass sleeve inside of it was of a slightly larger diameter than it needed to be. There is a chance that occasionally the conditions might've been just right so that it allowed the system to ingest a minuscule amount of water when a blow was commanded. How that would migrate back into the dry space, I'm not sure. I would think if anything it would get pulled into the ballast tank, but I could be wrong about that. Regardless, I've now re-built the float using a new piece of foam and a more appropriately sized sleeve that still allows easy movement, but has none of the last one's play. I'll give it a try today and see if that's made any difference.


Appreciate the help, as always, guys. Thank you!

-Brady