A Moebius Skipjack from the land of OZ...

[alad61]

Alec,
interested to know the source of the leak you had?
Was it SAS related or some other seal issue?

Also if you had water in the SAS induction line did the boat still surface using SD air ok?

Thanks

John

John in the beginning I believe I had seal issues from the induction tube in the sail to the induction elbow on the inside beneath the sail. I also know for certain that the switch leaked like a dripping tap when the SAS was drawing air from just the SD. The initial set up of the elbow block was without a stress relief point on the line out of it. A small piece of styrene tube and gluing the elbow block with thick ca an backing soda quickly sanded off before it fully cured solved a big water ingress issue. I must stress that it may well have been my initial assembly though.

Also running the boat at out of scale speeds causing excessive porpoising, pitching and rolling would have been the cause of some water making its way into the induction line.

Today was a different story!!! I spent the better part of almost two hours with the sub in the water running it with a full ballast. Once I worked out the best speed to drive it at all I had to do was thumb the rudder stick most of the time with only a little movement on the planes to drive it below periscope depth. I used the SAS at least twice to raise it and check the trim when opening the vent valve and the only signs of water in the SD were some fogging near the safety float valve... Apologies for the look of the video and the glare flashes. Between our morning winter sun and an incorrect exposure setting on the camera the video isn't the best. This was towards the end of the mission where I was feeling very comfortable with how it ran submerged after a good deal of time with it operating near the dock just in case something went against the plan.

[trout]

That ran great! You have really good control of it. When I first saw the posting, I was staring at the "picture" trying to see your sub - then started to chuckle when I thought of someone's tag "why are you staring at the empty pond" (something close to that).

[Slats]

Alec,
I can understand your other leaks, but the induction line if it has water inside it should not be leaking into the SD at all as the safety valve should be catching that.

David,
I take it the condensation that Alec is talking about would be normal - if the there is water in the induction line and the safety valve is working? Should we expect any condensation with SAS?

Thanks

John

[Scott T]

What if you make a bend in the induction line that is higher than the inlet valve opening to limit any water ingestion like on these
narco-semesubmersibles exhaust.

[He Who Shall Not Be Named]

Yes, with the SAS ballast sub-system you'll see condensation forming on the inside of the cylinder, over where the safety float-valve discharges/take on air within the cylinder. There is always water droplets sucked into the induction line once the snorkel head-valve opens upon broaching the sail. That moist air enters the interior of the SD through the safety float-valve, if there is a slight vacuum within the SD -- and that moist air hits the cold inside of the cylinder and condenses into 'fog' or even water droplets. No biggie. The safety float-valve is there to catch and stop an in-rush of water -- a broken or not made up snorkel induction hose -- not moist air.

David

[alad61]

What if you make a bend in the induction line that is higher than the inlet valve opening to limit any water ingestion like on these
narco-semesubmersibles exhaust.

[ATTACH=CONFIG]20969[/ATTACH]

I don't think a bend would make all that much difference as the LPB pump has a pretty good suction so you'd still get water droplets drawn in.

[alad61]

Alec,
I can understand your other leaks, but the induction line if it has water inside it should not be leaking into the SD at all as the safety valve should be catching that.

Thanks

John

John as my boat was bobbing around like a dolphin/kangaroo mutation with an unbalanced trim as well as the excessive torque rolls when trying to run it at 100% motor power Scuba Divingthe float in the sail wasn't getting time to do its thing The Titanicresulting in more water than normal getting in the induction lines. Yet even so the system still brought the boat back to a surface stance that let me control it back to the dock. Due to my own inadequacies or simple errors the system still worked And Sunday proved that when you get it all right the SAS system is better than good. I have another Gato model in transit from over seas so it will be going the SAS too :wink:

[alad61]

That ran great! You have really good control of it. When I first saw the posting, I was staring at the "picture" trying to see your sub - then started to chuckle when I thought of someone's tag "why are you staring at the empty pond" (something close to that).

Thanks Tom. Once I established the best revs for the motor it practicaly drove itself. All I pretty much had to do was attend the rudder and follow the wake from the masts.:biggrin:

[He Who Shall Not Be Named]

THAT'S the way it should be. Congratualtions, Alec. May it give you pleasure for decades.

M

[alad61]

Thanks David and I'm pretty sure it will.Since my previous post I had it out a couple of times with some quirks happening on the first run. It started the whole porpoising thing... Back on the bench I went through the gamet of tests starting with a good check of the planes for free movement then the the receiver and battery follwed by the adf and its functions and zero bubble recalabration. There was always some clutching on the servo for the rear planes but adjusting the sensitivity usually fixed that... But not this time. It turned out the servo for the rear planes went bad!! It was erratic and then wouldn't throw left and with each attempt it had a fit. So out it came and it was rather hot to touch to boot. Replaced it, retested everything then turned it off. Came back later turned it on and tested it all again readying it and recharging the batteries for last Sundays run. which except for the rain was beaut!http://static.photobucket.com/player...ps4e1998c0.mp4I took this with my mobile so apologies for the picture.

[He Who Shall Not Be Named]

Best weathering job on this beast yet. Well done, sir!

I bet you had to dial down your throttle end-points a bit? This thing will scoot!

M

[alad61]

Thanks David. And scoot it does!! I have the forward epa set to 60 otherwise it goes way too fast for the adf to do its job. I left the reverse higher as I often share water with yaughties and they have a nasty habit of changing tack and those long weighted keels don't flex much.

Onething I am finding is that air is still seems to get trapped aft of the sd. Sadly I added some out of scale vent holes to the rear as well as filing a groove out of the top rib/brace before the rudder. My next outing will confirm my fix...

[He Who Shall Not Be Named]

You're a bolder driver than me, Alec. I have ahead at 40% and astern at 75%. I'm with you: better to get out of trouble faster than you get into it.

M

[alad61]

40% might be something to try. What I found with to much speed on the surface was all the water flowing over the bow and forward top hull tended to push or nose down a bit and if you weren't paying attention whoosh she was under heading for the mud.

[HardRock]

Hey John,

I came across this entry earlier today (Sunday here) and suddenly it made the whole trim thing understandable. So I spent the rest of today - simply - trimming the boat. I've decided that I need a bigger bath tub incidentally. It now sits happily with the top of the sail just underwater (in fresh water) and just out in the swimming pool. Also found that I kept loosing the sail planes linkage so I made a small modification to more easily locate the control rod.

Thanks for the information. Its made a great deal of difference!