Re: (Poly)Acetal
From Classic Polymers....
"Polyacetal is a thermoplastic polymer manufactured by the
polymerization of formaldehyde. Polyacetal is a highly crystalline
thermoplastic. The chemical composition and the regular structure of
the material gives parts made of Polyacetal a combination of physical
properties not available with metal or other plastics. "
http://www.machinist-materials.com/comparison_table_for_plastics.htm
might be interesting.
Cheers
Derek
"Polyacetal is a thermoplastic polymer manufactured by the
polymerization of formaldehyde. Polyacetal is a highly crystalline
thermoplastic. The chemical composition and the regular structure of
the material gives parts made of Polyacetal a combination of physical
properties not available with metal or other plastics. "
http://www.machinist-materials.com/comparison_table_for_plastics.htm
might be interesting.
Cheers
Derek
It sounds like it could be derlin or UHMW. There is also silicon
impregnated sheets they use in packing houses for produce they call a
slip pallet. That materiel is very thin but indestructible as far as
sliding and makes a great tabogan for smaller children. I use the
stuff on my catamaran after using tin snips to cut it to size for
rudder and mast rotation bearings. It never wears out. In all
probability it is UHMW since you stated it is a white color. UHMW is
Ultra High Molecular Weight plastic. I use it on the bottoms of my
drift boats I have built and the go up and over rock like they were
made of butter
Here is an earlier post about some free samples of UHMW but you have
to give them a business name.
http://groups.yahoo.com/group/bolger/message/22360
You could compare the two and see if you already have UHMW. I will
coat any bottom of a wooden boat I build with this stuff. It will
make a boat slide over things instead of eating through the plywood.
John
impregnated sheets they use in packing houses for produce they call a
slip pallet. That materiel is very thin but indestructible as far as
sliding and makes a great tabogan for smaller children. I use the
stuff on my catamaran after using tin snips to cut it to size for
rudder and mast rotation bearings. It never wears out. In all
probability it is UHMW since you stated it is a white color. UHMW is
Ultra High Molecular Weight plastic. I use it on the bottoms of my
drift boats I have built and the go up and over rock like they were
made of butter
Here is an earlier post about some free samples of UHMW but you have
to give them a business name.
http://groups.yahoo.com/group/bolger/message/22360
You could compare the two and see if you already have UHMW. I will
coat any bottom of a wooden boat I build with this stuff. It will
make a boat slide over things instead of eating through the plywood.
John
--- In bolger@y..., "Hannes" <h.kuehtreiber@t...> wrote:
> There's one for the plastic experts out there:
>
> for my ingenious slide-boat-onto-roofrack contraption I bought some
> scrap from a sheet of white, smooth, relatively flexible plastic.
> Plywood really slides over it really well.
> The guy at the shop told me its called (Poly?)Acetal, but couldnt
> tell me anything about it except that it would stay smooth just
> about forever.
> I seem to recall this material is also available in rods to be made
> into bearings.
>
> Questions:
> same material ?
> what is it made of ? nylon?
> why would it stay so smooth ?
>
> anybody knows?
>
> hannes
There's one for the plastic experts out there:
for my ingenious slide-boat-onto-roofrack contraption I bought some
scrap from a sheet of white, smooth, relatively flexible plastic.
Plywood really slides over it really well.
The guy at the shop told me its called (Poly?)Acetal, but couldnt
tell me anything about it except that it would stay smooth just
about forever.
I seem to recall this material is also available in rods to be made
into bearings.
Questions:
same material ?
what is it made of ? nylon?
why would it stay so smooth ?
anybody knows?
hannes
for my ingenious slide-boat-onto-roofrack contraption I bought some
scrap from a sheet of white, smooth, relatively flexible plastic.
Plywood really slides over it really well.
The guy at the shop told me its called (Poly?)Acetal, but couldnt
tell me anything about it except that it would stay smooth just
about forever.
I seem to recall this material is also available in rods to be made
into bearings.
Questions:
same material ?
what is it made of ? nylon?
why would it stay so smooth ?
anybody knows?
hannes
--- In bolger@y..., "brucehector" <bruce_hector@h...> wrote:
concrete beams. Pure [unreinforced] concrete is relatively weak in
tension, but quite strong in compression. Similar case for a
segmented boat. The pieces easily pull apart, but push together
snuggly.
They solve the problem economically in concrete design by using
tension cables in tubes, which, after assembly, are then
prestressed "IE pulled tight".
A tube could be fastened along each chine [probably steel pipe], and
after assembly, a cable could be strung inside the tube.
Conventional prestressing tools and hardware available from
prestressing concrete wholesalers [and not all that expensive either]
could be used to fasten the far end of the cable, and a hydraulic
jack could tighten the cable from the other end and lock the boat
segments together.
The engineering is pretty simple, first year structural class at the
University kind of stuff. You probably could enlist some university
engineering class to help out with the engineering [and construction]
instead of their perennial "concrete canoe" contest.
Bruce Hallman
> I envision only temporary fastenings though. Screws, overlappingThis is a classic engineering issue, similar to the designing of
> chine logs and epoxy will make for a strong permanent melding. But
concrete beams. Pure [unreinforced] concrete is relatively weak in
tension, but quite strong in compression. Similar case for a
segmented boat. The pieces easily pull apart, but push together
snuggly.
They solve the problem economically in concrete design by using
tension cables in tubes, which, after assembly, are then
prestressed "IE pulled tight".
A tube could be fastened along each chine [probably steel pipe], and
after assembly, a cable could be strung inside the tube.
Conventional prestressing tools and hardware available from
prestressing concrete wholesalers [and not all that expensive either]
could be used to fasten the far end of the cable, and a hydraulic
jack could tighten the cable from the other end and lock the boat
segments together.
The engineering is pretty simple, first year structural class at the
University kind of stuff. You probably could enlist some university
engineering class to help out with the engineering [and construction]
instead of their perennial "concrete canoe" contest.
Bruce Hallman
> How do the separate sections of the Breakdown Schooner attach? HowThe ballast tank at the bottom of the amidships section sticks
> you line them up afloat? I can't make out enough detail in BWAOM.
under the bottom of the back of the bow and the forward end of
the stern. There are little skegs on the bow and stern sections
that stick out over the gap that the ballast tank fits in, to
hold the bottom part in place, and long U-shaped metal brackets
up at the sheer where the sections come together that hold a
set of bolts for bolting the sections together, sort of like this:
SSSSSSSSSSSSSAAAAAAAAAABBBBBBBBBBBB
===SA=== ===AB===
<- to stern SA AB to bow ->
SA AB
SSSSSSSSSSA ABBBBBBBB
SSSSAAAAAAAAAAAAAAAAAAAAAAAAAABBBBB
SSS BBB
And that's it. Just one pair of bolts per joint, and one little
skeg that overlaps just a few inches. It's intended for protected
waters only; I have no confidence in the skegs not getting ripped
off and the bolts bent under the stress of a heavy storm. Neither
does PCB, from the comments in the construction key.
--
Susan Davis <futabachan@...>
Peter,
I figured the head and shower to be in the stern power unit so I
couldn't put to sea without them. They'd be on either side of the
passageway under the "dash" to reduce the length of the dash required.
Bruce
I figured the head and shower to be in the stern power unit so I
couldn't put to sea without them. They'd be on either side of the
passageway under the "dash" to reduce the length of the dash required.
Bruce
Lots of great suggestions. Thanks.
I envision only temporary fastenings though. Screws, overlapping
chine logs and epoxy will make for a strong permanent melding. But I
don't want permanent.
I imagine the various units bobbing at anchor in the bay when not
needed. The guest unit, the galley unit, and the stateroom unit may
be needed on the weekend. But perhaps just the BBQ unit and dance
unit on Tuesday for a short evening party cruise. Then they're
detatched the next morning and the stateroom and and bar unit are
required for the next cruise. Of course for a short day trip just the
bow and atern unit could operate as a 16 foot day boat.
Each module would be a separate, water-tight unit that can spend
extended time at anchor to save marina fees and the length and
capabilities of the Modular Cruiser are modified as needed. Perhaps
to defeat the marina fee problem, the stern power unit could drop
off, leaving the whole mess at anchor, and motor in independently for
more beer,...er, I mean supplies.
How do the separate sections of the Breakdown Schooner attach? How
you line them up afloat? I can't make out enough detail in BWAOM.
I've been looking at the tie-downs on conatiner ship pods and the
like, but don't know how to do it in wood, turnbuckles, bungee cords
or bolts.
Bruce Hector
www.brucesboats.com
I envision only temporary fastenings though. Screws, overlapping
chine logs and epoxy will make for a strong permanent melding. But I
don't want permanent.
I imagine the various units bobbing at anchor in the bay when not
needed. The guest unit, the galley unit, and the stateroom unit may
be needed on the weekend. But perhaps just the BBQ unit and dance
unit on Tuesday for a short evening party cruise. Then they're
detatched the next morning and the stateroom and and bar unit are
required for the next cruise. Of course for a short day trip just the
bow and atern unit could operate as a 16 foot day boat.
Each module would be a separate, water-tight unit that can spend
extended time at anchor to save marina fees and the length and
capabilities of the Modular Cruiser are modified as needed. Perhaps
to defeat the marina fee problem, the stern power unit could drop
off, leaving the whole mess at anchor, and motor in independently for
more beer,...er, I mean supplies.
How do the separate sections of the Breakdown Schooner attach? How
you line them up afloat? I can't make out enough detail in BWAOM.
I've been looking at the tie-downs on conatiner ship pods and the
like, but don't know how to do it in wood, turnbuckles, bungee cords
or bolts.
Bruce Hector
www.brucesboats.com