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RE: [PSUBS-MAILIST] psub convention in Raystown
Rob,
Please don't take offense, I can only imagine how keen you are to get
the sub in the water. However, the questions below are a real concern. I
would emphatically recommend you try to hook up with someone in your
area who operates a sub, to have them look it over and give you some
pointers, rather than give this a try unassisted. If there's nobody
local, give Mark Ragan a call and take the lessons he offers. I'm not
sure his rates, but I think it's super reasonable. Please don't take
this lightly, your life literally depends on it even if you are in a few
feet.
I'll respond to your questions below, but be aware the things that can
also ruin your day are ones you might not have even thought to ask. What
is the condition of the viewports? These have only a 10 year life span,
regardless of whether they have been used or not. Sure, they degrade
faster if left out in the sun or in a hot place, but they still degrade
slowly even if stored in ideal conditions. They can fail without looking
precarious first, and if they do it'll be so sudden you'll never see it
coming. Have you replaced the O rings on mechanical through-hulls? The
sub has been sitting around, and they could have perished. And speaking
of perishing rubber, how about those air hoses? Have the SCUBA regs been
serviced? You don't want a reg to stick in a sub any more than you would
diving. Is there internal corrosion in the VBT? You don't want the thing
to blow up under your seat when you pressurize it. Have you tested the
drop weight mechanism? And on and on, I think you probably get the idea!
Please see below...
Thanks,
Alec
-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Rob And
Kathy
Sent: Thursday, June 29, 2006 11:24 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] psub convention in Raystown
Hi out there,
I have some questions on my new k-250
I have been reading all your emails and am now looking forward
to
putting my k-250 in the lake for a trial spin in a couple of weeks, but
a
couple of things are bothering me.
first issue is the props, the sun has done its damage to the
plastic and I need new ones. They look like old minnkota trolling motor
props. is that a possibility? Do I worry about prop pitch ?
AS: The original design has custom made thrusters, and the ones I've
seen had brass props, but a lot of K boats out there do use trolling
motors. Chances are you probably do have trolling motor props if they
are made of plastic. If I were you I'd just take one off and take it to
the closest boat store to see if they have something that matches it.
But in general whether your prop pitch is right or not is a minor
concern, in the sense it's not one of the life-threatening items.
second. how much air pressure do I put in the aqualung for the
fore, aft, and main ballast tanks? Can I use a regular air compressor to
fill it? Is one aqua lung enough (only have one) for a test dive to
about 25
feet down?
AS: Uh-oh, unless I'm reading too much into this, it sounds like you're
unfamiliar with filling a SCUBA tank, which would indicate you're
unfamiliar with SCUBA. I think it's no coincidence virtually all psub
operators I've met are certified divers. It's a good idea to get
certified before you go to subs, because both the physics and the
hardware have a lot of overlap. You will need a SCUBA certification to
have the tanks refilled, and given the time the sub has been sitting
around, it's a safe bet they will need to be hydrostatically tested
before anyone will fill them. You can most certainly NOT fill the tanks
with a regular compressor, for two reasons. First, although I cannot
tell the fill pressure without looking at the tank markings, you can be
sure it exceeds the pressure that a regular compressor puts out. At the
pressures a shop compressor puts out, a SCUBA tank would be considered
all but empty. Second, the air out of a regular compressor has too much
oil and too much humidity in it. If it is properly filled to capacity,
one tank should be enough, although it's a good idea to have a spare
inside for the pilot to use in an emergency. BUT then again, for that
you would want to get SCUBA certified first or your emergency safety
device might kill you. One semantic point, the fore and aft tanks ARE
the MBTs. The one in the middle is the VBT.
third. do I fill the main ballast tank (my seat is this tank)
for
neutral bouyency?
AS: Sorry, please don't take offence but the nature of these questions
is setting off alarm bells. That's the VBT under your seat, and its used
to fine tune your buoyancy. However, it's impossible to know in advance
whether you will need it to be full, empty, or partway, because the
answer depends on how buoyant the sub is with all weights on board
(including the pilot). It's a function of things like whether the water
you will dive in is fresh or salt, your own weight, and how much other
stuff happens to be inside the sub at the time. If you are not aware of
the way the MBT and VBTs are used, please seek out formal training prior
to this dive. Do NOT go in the water without a through understanding of
this.
fourth. Is RTV used for the port glass gaskets? (it looks like
red
rtv) and is rtv a problem?
AS: As I just discovered at the convention, there are better sealants.
But RTV can be used.
fifth, an air line has come apart at a fitting, is stainless
fittings
and tubing a problem instead of using copper for the air lines? Copper
was
used in the sub but the stainless I have is for higher pressures.(
dissimiler metel issues?)
AS: Either will work, but stainless is actually better. Try not to mix
both materials, though, since that will promote corrosion. But that's a
longer term issue.
and last but not least , the batteries. What kind? will marine
batteries be alright and do I have to use the hydrogen caps ( batteries
are
sealed and dont usually accept the screw in caps) by the way there is a
battery box is a extremly well built and is sealed.
AS: It will work with any deep cycle batteries. However, because the
batteries are inside the cabin in the K250, there is always a slight
risk of explosion. I would recommend advanced glass mat batteries, known
as AGM, in order to minimize that risk. A represenative brand of AGMs is
"Lifeline." Even if the batteries are sealed, they do in my experience
off-gas during charging, so you want to open that box and ventilate
everything during charging. Your charger should be matched to the
battery technology.
One more question, is there really going to be a convention in
michagan?
Upper ? lower? but no matter it would be close enough coming from
minnesota
towing my lil sub for me to want to be there.
Thank you for your time and the wonderful stories that I have been
reading
on the psub site, without you guys guys like me would be making terrible
dangerous mistakes.
Rob
Lepak
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