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Alec,
Three months for
one......hmmm.....that must have tested your patience a little
:) 31" x 3/8" sounds like a pretty tough hull. What depth are you
planning on getting to ?
I have been looking over the archives
to find information on the ribs / installation but couldn't find anything.
I was quite surprised as I figured this was a very important, and likely very
difficult step, as you have pointed out. If somebody has it "figured out"
how to do it the best, that would be valuable information.
I wonder if installing the first rib
closest to the end cap, or in the middle would be best. I am going to
guess that the middle one would be the better approach and work out to both ends
from there.
Myles.
----- Original Message -----
Sent: Thursday, November 10, 2005 12:02
PM
Subject: RE: [PSUBS-MAILIST] Inner /
Outer support ribs.
Myles I should tell you getting those stiffeners in was far and away
the hardest part of building Solo. It took me three months of work to get the
first ring in. But it certainly worked as a method for stretching the hull
into roundness. This is a 3/8 thick hull of only 31" outside diameter, so not
very stretchy. If I remember correctly, the out of roundness prior to
inserting the stiffeners was about half an inch difference between maximum and
minimum diameters. With stiffeners in, I can't detect any out of
roundness.
My method was as follows: Roll the ring in along the greater
diameter, then try to straighten it until normal to the hull. I tried
hydraulics and failed. I tried icing the rings and heating the hull, but that
failed too. The latter is what Phil Nuytten does, but I presume his hull
cylinders are much higher quality (rounder) than mine. What worked for me
in the end was a very long lever built to hook onto the end of the hull
cylinder, chained to 1/2" holes drilled in the stiffener web. I built a
motorized table for my mill-drill machine, with which I could gradually
reduce the diameter of the stiffener by a few thousandths after each
unsuccessful attempt. I did this lots of times, on each iteration getting
closer to straightening the stiffener all the way. Of course, the hard one is
the first stiffener, and after that they go fast.
rgds,
Alec
Dan,
The point I never considered was
using the rings to force the hull into roundness. I can definately see
where this would be easier when putting them on the inside as they could be
pounded / hammered / tapped into place, spot welded, and then secured when
all was well. That answers another question in that the rings are to
be pre made and not welded onto the pressure hull when building them.
In that way, the roundness of the rings could be made true before
installing. As for attaching things to the rings inside the hull, is
it safe to drill 1/4" holes for bolts or is that comprimising the
integretity of the ring too much ? ...or would welding mounting
brackets to the rings and then drilling the holes be preferable
?
On the K350, does the design just
eliminate the ring where the tower is, the tower collar providing the
strength in that area ?
Thanks for making my mind up for
me Dan.
Myles.
----- Original Message -----
Sent: Wednesday, November 09, 2005
9:10 PM
Subject: Re: [PSUBS-MAILIST] Inner /
Outer support ribs.
Myles,
A K-350 has ribs spaced 12 inches apart, and
at the ends where the hull tube meets the end caps, they are 10 inches
apart leaving two inches of hull tube sticking past the last frames
to weld the end caps to.
True, the frame would be easier to apply
to the outside of the hull, for convenience of working, but it's easier to
spring the hull into better roundness when working from the inside.
No rolled tube is perfect round. You have to work it
as your installing the framing.
Ribs on the outside give you more places for
corrosion to attack, but do increase the inside room. Ribs on the
inside cramp the space in the sub, but are a convenient place to clamp
things that you want to add later on, without welding on the finished sub
hull.
Dan H.
----- Original Message -----
Sent: Wednesday, November 09, 2005
6:11 PM
Subject: [PSUBS-MAILIST] Inner /
Outer support ribs.
I understand that support ribs offer the
same strength increase whether they are on the inside or outside of the
pressure hull. As I am planning on adding fairing, I am also
considering puting the ribs on the outside to free up interior
space. Is this a good idea ? In other words, is it easier to
install the ribs when they are on the outside ? Are the ribs
pre-made and then welded on or built right onto the pressure
hull ? I can't seem to figure out the ribs, how they are made, and
the best way to install them. My pressure hull is of a similar
design as the K350 36" x 1/4 " x 8'. I am considering a rib
spacing of 18".
Myles.
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