Re: Joint tests completed... advice?
> I'm needing help from you guys to make sense of this data. Asusual, all ideas, opinions and theories are welcome.... Here's the
link to the test write up.
>Not to oversimplify, but the data is telling you that some are weak,
>http://members.tripod.com/simplicityboats/jointtest.html
>
> David Beede
> www.simplicityboats.com
some are flexible, and some are stiff. I am not sure what the case
for the weak bond would be, cost or something. But the flexible
might be ok in a situation where that was called for. And hard where
hardness is called for.
Three things to keep in mind about the polynesian experience are that
they did brilliant boatbuilding with a limited number of materials,
we don't know what their tradition would have made of more options.
Generally I don't see the point to stetchy lashings, but they
certainly work. Another point is that the Wharram lashings are
designed for a certain service, and then they need to be switched
out. I wouldn't want to have to switch out an energy absorbing keel
(or other joint) unless there was a real reason for it. I have never
observed these lashings from up close, but not all plant fibers are
springy, nylon rope is. Often the connective is a series of
triangulated sticks, not evidence of a desire for flexibility I would
have thought (but they aren't any one design). Possibly the real
analogue would be a low stretch rope like spectra.
I think another thing that has to be kept in mind is that joints have
more roles than connecting two pieces of ply. They can be part of
the structure themselves. So a poured glass and epoxy keel is not
only a connection between two panels, but becomes the keel "timber".
It may also have to receive the daggerboard trunk, so secondary
bonding and a variety of other issues come into play.
David-
It appears that the data would have the best non-epoxy
joint be the PL Premium to bond the ply to the chine
with an epoxy/glass tape on the outside.
I am currently building a Junebug with the powdered
glue and will try the PL premium for all of the
internal finishing work.
I would guess that the PL premium fillet is weak
because the bond is the glue to itself. The fillet may
allow more "foaming" of the PL than a tight chine-ply
joint making the PL weaker.
This is just a guess, based upon all of the discussion
on glues. Other thoughts?
YIBB
Eric McCollum
http://members.tripod.com/simplicityboats/jointtest.html
--- David Beede <david@...> wrote:
http://members.tripod.com/simplicityboats/jointtest.htm
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It appears that the data would have the best non-epoxy
joint be the PL Premium to bond the ply to the chine
with an epoxy/glass tape on the outside.
I am currently building a Junebug with the powdered
glue and will try the PL premium for all of the
internal finishing work.
I would guess that the PL premium fillet is weak
because the bond is the glue to itself. The fillet may
allow more "foaming" of the PL than a tight chine-ply
joint making the PL weaker.
This is just a guess, based upon all of the discussion
on glues. Other thoughts?
YIBB
Eric McCollum
http://members.tripod.com/simplicityboats/jointtest.html
--- David Beede <david@...> wrote:
>http://members.tripod.com/simplicityboats/jointtest.html
> Please forgive the cross posts, but I really need<snip>
> help interpreting these results.
>
> Well I just completed the stress tests on the
> first 6 ply joints including Epoxy & Glass tape,
> chine log & PL Premium, and also PL Masonry and mesh
> tape, after allowing a week of curing. The results
> are mostly what you might expect with some
> interesting elements that make interpretation kind
> of tricky. Perhaps you guys can help.
http://members.tripod.com/simplicityboats/jointtest.htm
>__________________________________________________
> David Beede
> www.simplicityboats.com
> ~~~/^\
> / \
> / /
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>
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9-11: A tribute to the more than 3,000 lives lost
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--- In bolger@y..., "David Beede" <juliejj@n...> wrote:
Very interesting experiments, thanks,
and nice job html'ing the results!
I conclude that there is *lots* of
spare tolerance in boat building.
Notice that (only rarely) does PCB
specify exact construction method
or materials in his designs. Instead
he leaves the exact choices up to
the whims of the individual builders.
I believe this is because, the exact
choice is rarely that important and
usually is over-kill.
In short, when in doubt, barge ahead.
You could have built a Teal in the
time it took to perform those
experiments! <big grin>
> I'm needing help from you guys to make sense of this data.[sorry if this is a double post, the Y*gremlins ate my first post]
Very interesting experiments, thanks,
and nice job html'ing the results!
I conclude that there is *lots* of
spare tolerance in boat building.
Notice that (only rarely) does PCB
specify exact construction method
or materials in his designs. Instead
he leaves the exact choices up to
the whims of the individual builders.
I believe this is because, the exact
choice is rarely that important and
usually is over-kill.
In short, when in doubt, barge ahead.
You could have built a Teal in the
time it took to perform those
experiments! <big grin>
I think it means that you should not build a boat with the PL and
glass fillet technique! At least not a boat in which you are going
venture very far from shore. I'd be concerned that hitting a wave
could rupture the joint and leave you in a world of hurt.
While you did not test it, I would also guess the PL and glass would
not hold up well in test of shearing the glue joint either. How you'd
perform such a test on your set-up is beyond me though.
Have you considered soaking the joints in water and testing their wet
strength? There could be some real differences with some of the glues
depending on whether the wooden substrate is wet.
Thanks for the good work though. I've seen enough to know what I
won't try in the future!
JB
glass fillet technique! At least not a boat in which you are going
venture very far from shore. I'd be concerned that hitting a wave
could rupture the joint and leave you in a world of hurt.
While you did not test it, I would also guess the PL and glass would
not hold up well in test of shearing the glue joint either. How you'd
perform such a test on your set-up is beyond me though.
Have you considered soaking the joints in water and testing their wet
strength? There could be some real differences with some of the glues
depending on whether the wooden substrate is wet.
Thanks for the good work though. I've seen enough to know what I
won't try in the future!
JB
--- In bolger@y..., "David Beede" <juliejj@n...> wrote:
>http://members.tripod.com/simplicityboats/jointtest.html
> Please forgive the cross posts, but I really need help interpreting
these results.
>
> Well I just completed the stress tests on the first 6 ply
joints including Epoxy & Glass tape, chine log & PL Premium, and also
PL Masonry and mesh tape, after allowing a week of curing. The
results are mostly what you might expect with some interesting
http://members.tripod.com/simplicityboats/jointtest.html
Please forgive the cross posts, but I really need help interpreting these results.
Well I just completed the stress tests on the first 6 ply joints including Epoxy & Glass tape, chine log & PL Premium, and also PL Masonry and mesh tape, after allowing a week of curing. The results are mostly what you might expect with some interesting elements that make interpretation kind of tricky. Perhaps you guys can help.
If you only consider how much force is required to first distort and then rupture a joint, epoxy is the clear winner with the PL Premium and chine log the runner up. The worst performer was the PL Premium fillet inside and PL Premium and mesh tape outside. It failed with very little effort. (Oddly this is similar to the build method David Colpitts used on a kayak that has lasted 6 years...?? go figure?)
The PL Masonry joints are harder to interpret because they were so flexible they were near impossible to get to rupture, requiring repeated extreme flexing, as in {"fully closing a book" or "opening a book past flat." The tricky part is that the forces necessary to flex these joints was low - in the 10 lb range, as opposed to the epoxy which required 180 lbs, and chine logs 80 lbs. However both epoxy and chine log joints held so well that the plywood fibers ruptured. This reflects all modern glue advertisements of "the glue joint is stronger than the wood!" Which seems like a good thing.
However, the PL Masonry flexed so much it absorbed all the force and didn't pass it on to the wood, and for the longest time, neither the glue joint nor the wood failed, returning repeatedly to its pre stressed state. After repeated extreme flexing I was able to get the glue to fail, but only by asking it to bend in ways that it could never bend while incorporated into a boat hull.
I imagine there are up sides and down sides to this. These joints could potentially withstand great stress and stay water tight, and not pass the stress on to the wood that is joined. Someone mentioned they might be candidates for creating hinges on a folding boat. Anyone who has ridden in one of those polymer folding "port a boats" knows how strange it feels to have a hull flex under you. It takes a little getting used to. Yet it doesn't necessarily mean its not strong. On the Portaboat web site they show photos of loading 600 lbs of concrete in their folding boat and dropping it from 21 ft.http://www.porta-bote.com/James Wharram imitates the Polynesians by lashing his hulls to the amas to allow flexing at sea.
I'm needing help from you guys to make sense of this data. As usual, all ideas, opinions and theories are welcome.... Here's the link to the test write up.
http://members.tripod.com/simplicityboats/jointtest.html
David Beede
www.simplicityboats.com
~~~/^\
/ \
/ /
/_____/
_______ /___/
\__________/
\/
[Non-text portions of this message have been removed]
Please forgive the cross posts, but I really need help interpreting these results.
Well I just completed the stress tests on the first 6 ply joints including Epoxy & Glass tape, chine log & PL Premium, and also PL Masonry and mesh tape, after allowing a week of curing. The results are mostly what you might expect with some interesting elements that make interpretation kind of tricky. Perhaps you guys can help.
If you only consider how much force is required to first distort and then rupture a joint, epoxy is the clear winner with the PL Premium and chine log the runner up. The worst performer was the PL Premium fillet inside and PL Premium and mesh tape outside. It failed with very little effort. (Oddly this is similar to the build method David Colpitts used on a kayak that has lasted 6 years...?? go figure?)
The PL Masonry joints are harder to interpret because they were so flexible they were near impossible to get to rupture, requiring repeated extreme flexing, as in {"fully closing a book" or "opening a book past flat." The tricky part is that the forces necessary to flex these joints was low - in the 10 lb range, as opposed to the epoxy which required 180 lbs, and chine logs 80 lbs. However both epoxy and chine log joints held so well that the plywood fibers ruptured. This reflects all modern glue advertisements of "the glue joint is stronger than the wood!" Which seems like a good thing.
However, the PL Masonry flexed so much it absorbed all the force and didn't pass it on to the wood, and for the longest time, neither the glue joint nor the wood failed, returning repeatedly to its pre stressed state. After repeated extreme flexing I was able to get the glue to fail, but only by asking it to bend in ways that it could never bend while incorporated into a boat hull.
I imagine there are up sides and down sides to this. These joints could potentially withstand great stress and stay water tight, and not pass the stress on to the wood that is joined. Someone mentioned they might be candidates for creating hinges on a folding boat. Anyone who has ridden in one of those polymer folding "port a boats" knows how strange it feels to have a hull flex under you. It takes a little getting used to. Yet it doesn't necessarily mean its not strong. On the Portaboat web site they show photos of loading 600 lbs of concrete in their folding boat and dropping it from 21 ft.http://www.porta-bote.com/James Wharram imitates the Polynesians by lashing his hulls to the amas to allow flexing at sea.
I'm needing help from you guys to make sense of this data. As usual, all ideas, opinions and theories are welcome.... Here's the link to the test write up.
http://members.tripod.com/simplicityboats/jointtest.html
David Beede
www.simplicityboats.com
~~~/^\
/ \
/ /
/_____/
_______ /___/
\__________/
\/
[Non-text portions of this message have been removed]