fibreglass on PVC, making the mast tapered
In a message dated 02/07/2001 12:<BR14:<BR55 PM
Eastern Standard,djost@...writes:
Make a trough the length of the part you want to taper plus a foot. Make it
of anything, lying on the ground with the long axis normal to the rays of the
noon sun. The material can be dirt. Make it three times as wide as the mast's
largest diameter. Make it about 2" deeper than that diameter. Lay the trough
with foam sheet and then cover the sheet with aluminum (add vowels to taste)
foil. Get enough glass or clear plastic film to cover the box and some scrap
foam to plug the ends. Fit the foam around the full mast section to exclude
air exchange. You now have a solar oven.
Make your mast blank a couple feet longer than your finished mast is to be.
Make a wooden plug for the upper end and drill through the plug and the pipe
for a good strong double handle. Something like a mop handle makes a good
one. At the bottom, you don't need the plug, as that end won't be
soft...AAMAF, you can do without the upper plug if you make the balnk enough
longer to deep the upper end out of the oven.
Near enough to noon on a sunny day, lay the blank in the oven, with the
handles in the holes and the foam blocking the ends. If you have an oven
thermostat, put that down near the center of the oven so that you can read
it. Lay the glass or film over the trough.
Now, this dude will have to be turned every 15 minutes or so to keep from
sagging. Watch the thermostat or deep feeling the plastic...at about 190 deg
F, it will start to get soft. At about 230 (geez, it's been 4 years since I
did this, I hope my temps. are correct...maybe you should do a test of a
short section of the identical pipe in you home oven) it will be soft enough
to "pull". Grab both sets of handles (a helper is a big advantage here) and
pull gently and smoothly, while keeping the "new" flat edge down on the floor
of the oven. Helps to have wooden extensions out either side so the whole
thing can lie flat.
Watch how it cools...if the butt isn't kept off the floor a bit, the blank
will have a kink in it; you can figure this bit out.
Now, the taper isn't ideal, as it is rather hyperbolic following the
transition from the butt into the part that you stretched. the taper after
than is nearly linear until it gets up toward the tip, then it goes into a
reverse hyper up to the remaining full dia. bit. However, it is a dang sight
better than straight. You will probably want to have the diameter at the top
a bit larger than a wooden mast would require, so that the strength in the
lower mid portion is up to spec.
I've never done anything as large as a mast, but the technique works fine at
shorter lengths and up to 6" diameter. BTW, thick walled PVC, sched 80 or
better if you can find it, is more controllable in the stretch. I wouldn't
even try it with thin-walled drain pipe. I was able to find extra heavy
sewage pipe (municipal, not home) in a funny blue-green color with very thick
walls.
You are on your own now.
Cheers/Carron
Eastern Standard,djost@...writes:
> What diameter pvc pipe would you use for a 23' mast? Will this mast beYou can taper PVC pipe if you wish. Here's how.
> as strong as a laminated wooden spar?
Make a trough the length of the part you want to taper plus a foot. Make it
of anything, lying on the ground with the long axis normal to the rays of the
noon sun. The material can be dirt. Make it three times as wide as the mast's
largest diameter. Make it about 2" deeper than that diameter. Lay the trough
with foam sheet and then cover the sheet with aluminum (add vowels to taste)
foil. Get enough glass or clear plastic film to cover the box and some scrap
foam to plug the ends. Fit the foam around the full mast section to exclude
air exchange. You now have a solar oven.
Make your mast blank a couple feet longer than your finished mast is to be.
Make a wooden plug for the upper end and drill through the plug and the pipe
for a good strong double handle. Something like a mop handle makes a good
one. At the bottom, you don't need the plug, as that end won't be
soft...AAMAF, you can do without the upper plug if you make the balnk enough
longer to deep the upper end out of the oven.
Near enough to noon on a sunny day, lay the blank in the oven, with the
handles in the holes and the foam blocking the ends. If you have an oven
thermostat, put that down near the center of the oven so that you can read
it. Lay the glass or film over the trough.
Now, this dude will have to be turned every 15 minutes or so to keep from
sagging. Watch the thermostat or deep feeling the plastic...at about 190 deg
F, it will start to get soft. At about 230 (geez, it's been 4 years since I
did this, I hope my temps. are correct...maybe you should do a test of a
short section of the identical pipe in you home oven) it will be soft enough
to "pull". Grab both sets of handles (a helper is a big advantage here) and
pull gently and smoothly, while keeping the "new" flat edge down on the floor
of the oven. Helps to have wooden extensions out either side so the whole
thing can lie flat.
Watch how it cools...if the butt isn't kept off the floor a bit, the blank
will have a kink in it; you can figure this bit out.
Now, the taper isn't ideal, as it is rather hyperbolic following the
transition from the butt into the part that you stretched. the taper after
than is nearly linear until it gets up toward the tip, then it goes into a
reverse hyper up to the remaining full dia. bit. However, it is a dang sight
better than straight. You will probably want to have the diameter at the top
a bit larger than a wooden mast would require, so that the strength in the
lower mid portion is up to spec.
I've never done anything as large as a mast, but the technique works fine at
shorter lengths and up to 6" diameter. BTW, thick walled PVC, sched 80 or
better if you can find it, is more controllable in the stretch. I wouldn't
even try it with thin-walled drain pipe. I was able to find extra heavy
sewage pipe (municipal, not home) in a funny blue-green color with very thick
walls.
You are on your own now.
Cheers/Carron