On 02 May 2004 13:01:20 GMT, ospam (Stephen Baker)
vaguely proposed a theory
.......and in reply I say!:
remove ns from my header address to reply via email

Old Nick says:

before you get past your ankle there ;-)

Sorry. Don't get ya.

Reference to how far your foot may have travelled into your mouth....
Nothing personal. ;-)


hmmmm...I would be careful on the Web. "nothing personal" is easy for
_you_ to decide when you say it, smiley or not. G

But I take your point. And thanks for correcting me. Nobody else
seemed to think my misguided efforts worth guiding.
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The Met Bureau is LOVE!

My only concern would be keeping constant the frame material.
Especially if you are laying this stuff up by hand. If you want to use
Kevlar for a Kayak, use it for the skin, laid over fiberglass etc, not
for the frame, only my opinion. Scotty from Sm... oh, I just can't do
it, not for a nothing answer...

On 30 Apr 2004 04:22:27 -0700, (Snowman)
vaguely proposed a theory
.......and in reply I say!:
remove ns from my header address to reply via email

OK. I am now on track as to how these things are built. Sorry about my
misguided attempts.

My feelings:

As has been saidKevlar would be a difficult material to use to make
ribs as you suggest. Try epoxy/glass.

I cannot see any troubles. Although the foam is softer than wood, the
glass (kevlar) skin is what makes a foam/glass frame stiff, and stiff
it would be. Make the "walls" heavier than the "roof (inner) and
"floor" (outer) skins. make the floor heavoer than the roof.

Having said that, if the bending is the problem, I still reckon that
you could use kerfed wood, to make it easier to bend, over an
armature. My trial methos would be kerf and bend with the kerfs inside
the cirve, so that the outer side, at first was fair and not blocky.
You would have to make enough kerfs, each kerf wide enough, to allow
the bend.

This would then be covered with the glass skin, as much as possible,
and then turned and glassed on the remaining side once dry. Careful
work and a fair bit of it. The advantage of using wood as a core over
foam is that the skins can be thinner without fear of have
easily-punctured walls.

In the end you would have to try a few of these and test the
strength/weight ratio of these vs straight (bent!G) wood. Strength
in this case to my mind would include some sort of stanadard crushing
test.

I still wonder if all this weight saving is worth the trouble....I can
see it being useful in extreme situations of portability, and careful
usage.

I'm looking at building a Geodesic Airolite Boat, (see www.gaboats.com
by Platt Monfort) but I'm considering an interesting idea and I'm
wondering what you all might think. Instead of using wood strips to
form the geodesic structure I am thinking about using foam strips
wrapped in Kevlar tape and epoxy.

I have been reading about the construction of these boats and found
that some people have trouble with bending the ribs to shape without
breaking, (and this is with better quality wood that I am able to
source). I'm thinking I can bend foam cores easily to shape and then
once assembled in a frame start wrapping it all in Kevlar tape,
forming a makeshift Kevlar tube frame.

I'm still considering using wood for the stringers and gunwales as I
can form those with little or no problem. Having the stringers and
gunwales constructed out of wood would also make forming the foam ribs
much easier as it would give me something solid to work the foam
inside.

-Does anyone foresee a problem with pursuing this type of
construction?
-How will Kevlar wrapped foam compare to the equivalent
cross-sectional wood piece in strength?

Thanks
Jordan Richardson

************************************************** **
The Met Bureau is LOVE!

"Old Nick" wrote in message
...

My feelings:

As has been saidKevlar would be a difficult material to use to make
ribs as you suggest. Try epoxy/glass.

I cannot see any troubles. Although the foam is softer than wood, the
glass (kevlar) skin is what makes a foam/glass frame stiff, and stiff
it would be. Make the "walls" heavier than the "roof (inner) and
"floor" (outer) skins. make the floor heavoer than the roof.

I think this is where people often mistake stiffness versus strength.
Plain vanilla fiberglass is about the same stiffness as wood. In
other words, make a 1 inch by one inch by 12 inch stick of wood,
clamp it onto your workbench, and put a five pound weight on the
end. It bends about what, a half inch? Make a 1 inch by one
inch by 12 inch stick of fiberglass, put the same five pound weight
on the end, and it will bend about a half inch as well.

Now the fiberglass will support more weight before it breaks, but
it's also about three times heavier. Give me three times more
wood to use, and if I can make the beam a one by three, then I can
approach the load strength of the glass. Wood is good stuff for
resisting bending. I call it a naturally occuring unidirectional
carbon fiber reinforcement ;=)

I could go further into the engineering analysis and try to come
up with some numbers for equivalent stiffness of glass or
kevlar cored stringers. They'll either need to be larger in section
or solid glass. But in the end it sure seems like it's going
to be a lot of extra labor to build it that way, when the time could
be used to find some decent regional straight grained boatbuilding
lumber.

Just MHO.

Assuming that decent boatbuilding wood really is too difficult to
find, then I do like your idear of cutting kerfs on the wood stringers,
framing and skinning the boat, then filling the kerfs with epoxy/wood
dust and covering the kerfed face with glass.

Matt

Snowman,

Having built 4 or 5 of Platt Monforts ultra light canoes, I have a few
observations:

The concept of Kevlar wrapped foam ribs would probably be do-able, but
I guess I'm wondering what you hope to gain. Are you trying to make it
stronger? lighter? I'm wondering, how much weight can you expect to
save on a 14 pound boat? If the only reason is to avoid the heartbreak
of broken ribs during construction, it hardly seems worth the bother.

As for bending the ribs, I'll share my secret recipie. First, you must
realize that every wood bending method will likely result in some
breakage - the question is - can the number of ribs broken during the
bending process be kept to an acceptable limit? I always make 3 or 4
extra ribs for a 12 ft canoe which requires 16 ribs, total. Sometimes
I'll need one or two of my extras, but I've never needed more than
that.

Whatever wood you use, it will have to be selected for straight grain
- very little or no run out. I have had very good success with
SASSAFRASS (that's the secret ingredient). I know this is not a
standard item at Home Depot, but there are two lumber dealers in my
hometown of Springfield, Missouri where I can buy decent sassafrass
boards. Find out where your local cabinet makers buy their lumber -
sometimes it's sold as a substitute for ash (you can make a positive
ID by the smell). If you live in the southeastern US, inquire at small
local lumber mills.

Sassafrass is lighter than most hard woods, though a tad heavier than
the soft woods suggested by Montfort. It's an excellent wood for boats
- weather resistent, glues and finishes well, easily worked with hand
tools, and bends beautifully. At first I steamed my ribs in a PVC pipe
rigged up to a metal gas can (NEW - NOT USED!) on a Colman stove, but
I discovered this is unnecessary. Now I just run a few inches of hot
water in the bath tub and submerge them for a few hours before
bending. If it's a really tight bend, I might put a presoaked rib in
my PVC pipe, now capped on one end, and pour a teakettle of boiling
water over it for a few minutes just before bending.

Good luck,
GW

(Snowman) wrote in message . com...
I'm looking at building a Geodesic Airolite Boat, (see www.gaboats.com
by Platt Monfort) but I'm considering an interesting idea and I'm
wondering what you all might think. Instead of using wood strips to
form the geodesic structure I am thinking about using foam strips
wrapped in Kevlar tape and epoxy.

I have been reading about the construction of these boats and found
that some people have trouble with bending the ribs to shape without
breaking, (and this is with better quality wood that I am able to
source). I'm thinking I can bend foam cores easily to shape and then
once assembled in a frame start wrapping it all in Kevlar tape,
forming a makeshift Kevlar tube frame.

I'm still considering using wood for the stringers and gunwales as I
can form those with little or no problem. Having the stringers and
gunwales constructed out of wood would also make forming the foam ribs
much easier as it would give me something solid to work the foam
inside.

-Does anyone foresee a problem with pursuing this type of
construction?
-How will Kevlar wrapped foam compare to the equivalent
cross-sectional wood piece in strength?

Thanks
Jordan Richardson

G D Wright ) writes:

... I have had very good success with
SASSAFRASS

TF Jones also writes about preferring sassaras for steam bending
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On 13 May 2004 21:30:34 -0700, (G D Wright)
vaguely proposed a theory
.......and in reply I say!:
uncap my header address to reply via email

Ok. If you accept the building method of a skin over a frame, why not
build "gluelam" ribs and avoid the bending woes? AFAIK, gluelam is
actually stiffer than bent wood anyway. And no breakage. No troubles.

Snowman,

Having built 4 or 5 of Platt Monforts ultra light canoes, I have a few
observations:

The concept of Kevlar wrapped foam ribs would probably be do-able, but
I guess I'm wondering what you hope to gain. Are you trying to make it
stronger? lighter? I'm wondering, how much weight can you expect to
save on a 14 pound boat? If the only reason is to avoid the heartbreak
of broken ribs during construction, it hardly seems worth the bother.

As for bending the ribs, I'll share my secret recipie. First, you must

************************************************** *****

Sometimes in a workplace you find snot on the wall of
the toilet cubicles. You feel "What sort of twisted
child would do this?"....the internet seems full of
them. It's very sad