I am looking for any suggestions for a material that can be used to
fill the void in a PVC or ABS tubing, if and when used as tubing for a
bimini or the like. What size would you recommend?

Some thoughts include: epoxy, liquid foam, (cement -concrete???).....

Also what about using braided cable as a sort of rebar in the tubing
before filling tubing void?

Also what about using 3/4 or 1 inch copper tubing for a bimini or
dodger (plumbing supplies) with same tech. as above.


Thanks in advance.

I am not sure you exactly grasp the forces that act on boats at sea. About
the only thing that would make ABS pipe strong enough to stand up as a
Bimini frame would be a stainless tube on the outside. :-) Same is true
for that copper tube support on your windvane. One good quartering wave and
it will collapse against the transom. Most of the failures of commercial
stering vanes are in the stainless support structure. 316 Stainless has a
tensile strength of about 580 Mpa while hard drawn copper tube is under 200
Mpa. Heating to assemble it will soften it even further so soldered copper
tube doesn't stand a chance.

Same with the Bimini. The bending forces in tubing is all in the outer
fiber. Nothing you put inside (other than a steel tube) that will help
much. One good blow or an accidental steadying grab and it will be headed
for the recycling yard.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Mic" wrote in message
...
I am looking for any suggestions for a material that can be used to
fill the void in a PVC or ABS tubing, if and when used as tubing for a
bimini or the like. What size would you recommend?

Some thoughts include: epoxy, liquid foam, (cement -concrete???).....

Also what about using braided cable as a sort of rebar in the tubing
before filling tubing void?

Also what about using 3/4 or 1 inch copper tubing for a bimini or
dodger (plumbing supplies) with same tech. as above.


Thanks in advance.

Glenn Ashmore wrote:
I am not sure you exactly grasp the forces that act on boats at sea. About
the only thing that would make ABS pipe strong enough to stand up as a
Bimini frame would be a stainless tube on the outside. :-) Same is true
for that copper tube support on your windvane. One good quartering wave and
it will collapse against the transom. Most of the failures of commercial
stering vanes are in the stainless support structure. 316 Stainless has a
tensile strength of about 580 Mpa while hard drawn copper tube is under 200
Mpa. Heating to assemble it will soften it even further so soldered copper
tube doesn't stand a chance.

Same with the Bimini. The bending forces in tubing is all in the outer
fiber. Nothing you put inside (other than a steel tube) that will help
much. One good blow or an accidental steadying grab and it will be headed
for the recycling yard.

Idle curiosity acting here. Suppose...............you filled the PVC
(or copper or whatever) with urethane foam. You know, the foam they
sell for filling voids around windos at Lowes and Home Depot. I think
that they now actually sell it in a couple of different formulations.
Anyway, the stuff is a closed cell foam. I think it is pretty tough in
compression and does not add much weight.

Just wondering.

"Howard Peer" wrote
Idle curiosity acting here. Suppose...............you filled the PVC (or
copper or whatever) with urethane foam. You know, the foam they sell for
filling voids around windos at Lowes and Home Depot. I think that they
now actually sell it in a couple of different formulations. Anyway, the
stuff is a closed cell foam. I think it is pretty tough in compression
and does not add much weight.

Just wondering.

Not to get to far into the physics of materials but bending stress is the
primary force acting on a Bimini frame. As a tube is put under stress the
top will go under compression and the bottom tension. The sides and
anything inside will be under varying amount of tension and compression that
reduces to zero at the center or "neutral axis".

The ability of a beam to resist bending is determined by the strength of the
material, the shape and the distance of the furthest fiber to the "neutral
Axis". The strength is expressed as the "Modulus of Elasticity" or how much
a material will deform (strain) for a given amount of force (stress). The
shape is expressed as the "Moment of Inertia" which is more or less the
amount of material and its average distance from the neutral axis. (Greatly
over simplified)

Some examples of Modulus of elasticity a
Stainless Steel 30,000,000
Hard copper 16,000,000
ABS 331,000 (about 1/100 of stainless)

Examples of Moment of Inertia:
1/16" wall 1" tube .(stainless) .0203133
1/8" wall 1" tube (ABS) .0335558
Solid rod .0490874

Given that all are 1" in diameter the maximum distance to the neutral axis
is the same .5" so an ABS pipe will be about 1/50 as stiff as a stainless
tube. Notice that the Moment of a solid rod is only 45% greater than a 1/8"
wall pipe. Filling a tube with a material with good compressive strength
will prevent the tube from crimping but will do very little to keep it from
bending.

Also the corners must be considered. The large radius corners of a
stainless frame spread the bending load over the whole arc while a typical
ABS plumbing sweep Ell will concentrate the stress at the ends of the tube.
This is especially bad for copper as the ends will be annealed from the heat
of soldering.

Considering the number of mangled Bimini frames you will find in any marine
salage yard, an ABS frame would never survive even the slightest accidental
knock.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

On Mon, 13 Jun 2005 08:34:20 -0400, "Glenn Ashmore"
wrote:


"Howard Peer" wrote
Idle curiosity acting here. Suppose...............you filled the PVC (or
copper or whatever) with urethane foam. You know, the foam they sell for
filling voids around windos at Lowes and Home Depot. I think that they
now actually sell it in a couple of different formulations. Anyway, the
stuff is a closed cell foam. I think it is pretty tough in compression
and does not add much weight.

Just wondering.

Not to get to far into the physics of materials but bending stress is the
primary force acting on a Bimini frame. As a tube is put under stress the
top will go under compression and the bottom tension. The sides and
anything inside will be under varying amount of tension and compression that
reduces to zero at the center or "neutral axis".

The ability of a beam to resist bending is determined by the strength of the
material, the shape and the distance of the furthest fiber to the "neutral
Axis". The strength is expressed as the "Modulus of Elasticity" or how much
a material will deform (strain) for a given amount of force (stress). The
shape is expressed as the "Moment of Inertia" which is more or less the
amount of material and its average distance from the neutral axis. (Greatly
over simplified)

Some examples of Modulus of elasticity a
Stainless Steel 30,000,000
Hard copper 16,000,000
ABS 331,000 (about 1/100 of stainless)

Examples of Moment of Inertia:
1/16" wall 1" tube .(stainless) .0203133
1/8" wall 1" tube (ABS) .0335558
Solid rod .0490874

Given that all are 1" in diameter the maximum distance to the neutral axis
is the same .5" so an ABS pipe will be about 1/50 as stiff as a stainless
tube. Notice that the Moment of a solid rod is only 45% greater than a 1/8"
wall pipe. Filling a tube with a material with good compressive strength
will prevent the tube from crimping but will do very little to keep it from
bending.

Also the corners must be considered. The large radius corners of a
stainless frame spread the bending load over the whole arc while a typical
ABS plumbing sweep Ell will concentrate the stress at the ends of the tube.
This is especially bad for copper as the ends will be annealed from the heat
of soldering.

Considering the number of mangled Bimini frames you will find in any marine
salage yard, an ABS frame would never survive even the slightest accidental
knock.

--
Glenn Ashmore

Glenn I checked out you boatbuilding page, and I do remember reading
it a while ago, I liked it, it had personality.

I have done some futher consideration. You know all the cloth dodgers
I have seen, once they are setup they are never taken down (winter
storage may be an exception), which I also know from my own
experience.

The cruising logs I have read many have opted for a "hard dodger" or
commented that they might have prefered one. I have seen a few web
pages about building one...and well they can look OK or not visually
pleasing.

Glenn are you planning on a hard dodger or a dog house on your
construction or??????

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

If you want to avoid working with stainless tube a hard dodger or bimini
might be a good alternative. You can make the form with masonite over some
shaped 2x6s. Just paint and wax the masonite and lay the glass over it.
You would need to provide for additional thickness at the edges and possibly
a ridge across the center to add some stiffness.

As I get older a nice warm hard dodger extending back over the cockpit
sounds more and more attractive but Rutu was not designed for that. We will
have a split Bimini hung fore and aft of the traveler arch and possibly a
soft dodger if the boat stays here on the Georgia so I can extend my sailing
season. In the Leewards where we hope to be when we reach the
"post-tuition" stage of life we will just use the Bimini.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Glenn I checked out you boatbuilding page, and I do remember reading
it a while ago, I liked it, it had personality.

I have done some futher consideration. You know all the cloth dodgers
I have seen, once they are setup they are never taken down (winter
storage may be an exception), which I also know from my own
experience.

The cruising logs I have read many have opted for a "hard dodger" or
commented that they might have prefered one. I have seen a few web
pages about building one...and well they can look OK or not visually
pleasing.

Glenn are you planning on a hard dodger or a dog house on your
construction or??????

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Mic wrote:
....

The cruising logs I have read many have opted for a "hard dodger" or
commented that they might have prefered one. I have seen a few web
pages about building one...and well they can look OK or not visually
pleasing.


My boat has a "hardtop" which is really a 'glass platform supported by
heavy steel tubes. Its strong enough to walk on, large enough for
three solar panels, and ridged enough for the main traveler. Its
surrounded by canvas, with large windows and flys screens.

The way our cockpit is laid out, this has become an extra room. With
the full canvas surround, its possible to sail in freezing weather;
when the Sun hits the windows, it becomes a greenhouse.

The downside is that we tend to leave too much canvas up. Those who
sail these boats down south often remove all of the canvas for full
ventilation.

Its construction is far beyond my capabilities, especially since
windows and gutters are molded in, and carbon fibre is used to stiffen
it. If I had to do something like this myself, I would have someone
fabricate a strong frame in stainless, and then sew my own canvas
around it.

Here's a picture taken late in October, when the average gust in 18 knots:

http://www.sv-loki.com/Along_the_Way/surround.jpg

On Sun, 12 Jun 2005 15:10:40 -0400, "Glenn Ashmore"
wrote:

I am not sure you exactly grasp the forces that act on boats at sea.

I am aware of "the forces that (can) act on boats at sea". I readily
can not give you the ref. for the following, but am willing to accept
them as reasonable:

It was stated that about 93% of the time the winds are between 13-17
knots and for the remaining 7% of the time - 97% of that time they are
between 17-21 knots.

Its not the wind (for the most part) that does damage it the waves, as
you suggest.

I can not reasonably recall the force of a breaking wave on the deck
of a boat but I do recall I was amazed at figure of that force.

I do like the "cork" theory of a boat though...

About
the only thing that would make ABS pipe strong enough to stand up as a
Bimini frame would be a stainless tube on the outside. :-) Same is true
for that copper tube support on your windvane.

The copper tube support that "Walt" designed is interesting, but when
compared to the commercial vanes it is rather "light". I do believe
he said it survived 20 knot situations.

I have researched virtually all the sailing homebrew material
available:
- a PVC furling rig
-homemade furling
-homemade gennys, wind, water, fuel
-wind vanes
-polytarp sails
-stitch and glue techniques
-seahoods
-bimini's and dodgers
-PVC wisker poll
- all sorts of ingenius ideas and techniques, I read once that someone
called sailing a "thinking mans sport"...

I define intelligents as someone who see's something other than what
it is...ie a round disk is a dish, is a wheel, is a pully, is a
gear....a rather simple example but thats the idea.

Being smart I figure means that you dont have to work hard at learning
things. Me I am a limited person....."stupidity is unlimited, genius
is limited" :}

One good quartering wave and
it will collapse against the transom. Most of the failures of commercial
stering vanes are in the stainless support structure.

Personally I dont have any experience of the failure of wind vanes.
But from the numerous crusing logs I have read most of the failures
have been the vane "sail" and the associated rudder, as well as
various fasteners. Failure of the support structure has been less
common from my readings. YMMV.

I have seen the origin designs of wind vanes, I think one version was
of a friend of the Pardeys...actually earlier...

Here is the URL link:
http://www.freehandsteering.com/Windvane%20Story.htm
http://www.freehandsteering.com/Image.htm

http://www.geocities.com/Yosemite/Fo...ist/fhist.html
"World War II hero and wind-vane self-steering innovator Blondie
Hasler participated in a highly modified Folkboat named Jester. "

"Jester incorporated many innovations. Blondie Hasler was a pioneer in
the development of pendulum servo windvane self-steering gear. Jester
was steered from below decks via a whipstaff. All sail handling could
be performed from a central hatch without going on deck."

Other links:
http://www.freehandsteering.com/
http://www.hydrovane.com/


316 Stainless has a
tensile strength of about 580 Mpa while hard drawn copper tube is under 200
Mpa. Heating to assemble it will soften it even further so soldered copper
tube doesn't stand a chance.

Thanks for the specs......

Actually I think the weakest points in an ABS material would be where
there are fittings like 90's etc. and the point at which the rig is
fastened to the boat. (1 1/4" abs)

This is just an "idea" with the thought of getting opinions. Yes,
stainless tubing would be the way to go...$$$ and less workable as a
homebrew project. I like the ideas of these sort of boat
projects...not always the best answer but possibly a starting point.

I am certain that by building your own boat you know what I mean.


Same with the Bimini. The bending forces in tubing is all in the outer
fiber. Nothing you put inside (other than a steel tube) that will help
much. One good blow or an accidental steadying grab and it will be headed
for the recycling yard.

Humm...I am not so certain...but anything is possible although less
probable....

Fairwinds and calm seas.....

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Mic" wrote in message
...
I am looking for any suggestions for a material that can be used to
fill the void in a PVC or ABS tubing, if and when used as tubing for a
bimini or the like. What size would you recommend?

Some thoughts include: epoxy, liquid foam, (cement -concrete???).....

Also what about using braided cable as a sort of rebar in the tubing
before filling tubing void?

Also what about using 3/4 or 1 inch copper tubing for a bimini or
dodger (plumbing supplies) with same tech. as above.


Thanks in advance.

Mic wrote:

On Sun, 12 Jun 2005 15:10:40 -0400, "Glenn Ashmore"
wrote:

I am not sure you exactly grasp the forces that act on boats at sea.

I am aware of "the forces that (can) act on boats at sea". I readily
can not give you the ref. for the following, but am willing to accept
them as reasonable:

It was stated that about 93% of the time the winds are between 13-17
knots and for the remaining 7% of the time - 97% of that time they are
between 17-21 knots.

Its not the wind (for the most part) that does damage it the waves, as
you suggest.

I can not reasonably recall the force of a breaking wave on the deck
of a boat but I do recall I was amazed at figure of that force.

I do like the "cork" theory of a boat though...

Forget the wind and the waves. The problem with biminis and like structures is
they're inevitably used as handholds, to support 200 LB people being tossed
about in a seaway. This takes a toll even on the sturdy stainless steel ones.

Matt O.

Mic wrote:
I am aware of "the forces that (can) act on boats at sea". I readily
can not give you the ref. for the following, but am willing to accept
them as reasonable:

It would seem that you aren't really aware ...


It was stated that about 93% of the time the winds are between 13-17
knots and for the remaining 7% of the time - 97% of that time they are
between 17-21 knots.


It may have been "stated" but that doesn't make it true or meaningful.

First of all, the "average" wind varies a fair amount by location and
season, so any statistical claim such as that is just nonsense. In
Boston, for example, these numbers hold for July, the calmest month.
But in May and September there are numerous "average wind"
observations over 25 knots. Boston is somewhat windier than most
cities, but it is fairly representative of the New England coast. The
trades can be even windier.

And the "average wind" is meaningless when evaluating stresses on a
dodger or other accessories; it is the gusts that are significant.
Here the "93% point" in May and Sept is up around 23 knots, and 2% of
the gusts are over 30 knots.

In fact, if you just look at the record gusts, you'll find that most
cities in the US have had high gusts (over 40 knots) in almost every
month of the year. Thus, any permanently rigged dodger has to be able
handle that. My standard is 50 knots - that is, when I leave the boat
unattended, I assume that it can withstand gusts up to about 50 knots.
Above that point, I might consider adding docklines or removing
canvas. Designing something to "average winds" is silly.



Its not the wind (for the most part) that does damage it the waves, as
you suggest.

Actually, for the case of a dodger, its probably your brother-in-law
falling into it that you have to worry about. The frame should be at
least strong enough to hold a person; ideally it should be able to
withstand a person falling heavily against it.



I can not reasonably recall the force of a breaking wave on the deck
of a boat but I do recall I was amazed at figure of that force.

If you are on the wrong side of a "plunging breaker" your dodger is
the least of your worries ...

....


The copper tube support that "Walt" designed is interesting, but when
compared to the commercial vanes it is rather "light". I do believe
he said it survived 20 knot situations.

20 knots? What's the point? Self steering should be bulletproof,
not good enough for a daysail.



I have researched virtually all the sailing homebrew material
available:

....

The common aspect of of most of the "home brew" techniques is that
they have been proven worthless. For example, how many home built
ferro-cement boats are still sailing? Home many blue poly sails do
you see?

There are a few notable exceptions, but most of the home brew building
materials are junk. Why don't you see blue poly dodgers? Because
most people understand that the materials are only about 20% of the
value of the project. Most of the value is in the craft of assembly
and finish. Why would anyone use third rate materials for something
that takes a lot of manual labor?

My oldest sailing friends have cruised aboard for many years on a low
budget. Their current boat has probably tripled in value under their
careful restoration. They've done all their own canvas (and much of
mine), much of their rigging, replaced the engine and most
mechanicals, added wind and solar power, many, many, coats of varnish.
And one thing that stands out is that most of their work looks like
it was done by a professional shipyard, or better. All of the
materials are exactly what they should be, whether its stainless,
teak, or Sunbrella. I think they did use pvc for one project -
supports for solar panels that are only deployed at anchor - but I'm
guessing that was just a prototype that will soon be replaced by
stainless.