Tubing for bimini or dodger
 

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.

If you're in fresh water (you can) use aluminum tubing, if you're in salt
use stainless steel.

"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.

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:
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.

Quoted from www.capehorn.com. Yves Gelinas is the designer of the
CapeHorn self-steering system and this is the solution he came up with
for the dodger frame for his Alberg30 that he circumnavigated with.


"I wanted my dodger to whitstand a knockdown or a heavy sea falling
aboard. The solution I came up with was to replace the stainless steel
tubes of the frame with 2 inch dia. Dacron fire hose blown with air,
much like a bicycle tire : hit by a sea, it collapses and pops up again.
The ends of the tubes are capped with round PVC inserted into the tube
and held with 3 hose clips at each end. I purchased screw-on tire
valves, punched a hole near the end of the tube and screwed the valve in
place. I need to blow it up only once a season, and after 20 years, it
is still airtight."

"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

1088 wrote:

I saw something different at a fiberglass store. Kind of a composite
of rolled up mat and resin that was sold in 8 foot pieces. It looks
like dark red pvc pipe except solid. about 1inch diameter round rod.
They tell me fiberglass is 5 times stronger than steel but who knows.
The problem was they didn't sell any elbows or angles, so there wasn't
any equally strong way to connect the runs together.
I thought about pouring ortho resin with some mat scraps into a pvc
pipe and making something that your life wouldn't have to depend on.
Post what you find out, I think it's a great idea.

On Sun, 12 Jun 2005 15:38:01 GMT, (Mic) wrote:


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 used chimney rods to construct my "conestoga" style dodger frame.
The wife sewed up the canopy, and a bug screen for the after end.
a topper and side curtains are still in the clouds. I made end
brackets out of 1/2" copper pipe squeezed in a vice.

Cheap, flexible, indestructible. Still solid enought to grab when
going foreward, flexible enough to avoid being crushed, should you
be standing up going under a low bridge;-)

Terry K

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.