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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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