I was just going through some old emails, and saw a few comments on this
bench I posted a few years ago, so I thought i'd follow up. I built this as
an experiment in June of '04 out of the Borg's finest tubafour stock using
pinned and wedged M&T joints with no glue or finish. After 3 years of full
exposure, it split apart this summer. The pinned joints held up just fine,
and the wedged tenons in the vertical faces are still good. The wedged
tenons in the horizontal seat rotted out, and the end mortices obviously
failed. A better outdoor wood and a few minor design changes should last a
bit longer.

-MJ

"Mark Johnson" wrote in message
. ..
I was just going through some old emails, and saw a few comments on this
bench I posted a few years ago, so I thought i'd follow up. I built this
as an experiment in June of '04 out of the Borg's finest tubafour stock
using pinned and wedged M&T joints with no glue or finish. After 3 years
of full exposure, it split apart this summer. The pinned joints held up
just fine, and the wedged tenons in the vertical faces are still good. The
wedged tenons in the horizontal seat rotted out, and the end mortices
obviously failed. A better outdoor wood and a few minor design changes
should last a bit longer.

-MJ

Uuuuhhh......Mark.

How to say this.

Trying to be polite.

Have you been pushing away from the table when you should?

RonB

Mark Johnson wrote:

snip

| tubafour stock using pinned and wedged M&T joints with no glue or
| finish.

snip

| A better outdoor wood and a few minor design changes should last a
| bit longer.

Agreed. I still admire the design - and I'd (still) be pleased to have
a set of drawings for the original design. :-)

(I thought you were going to keep this on a covered porch for
smokers.)

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

On Sat, 18 Aug 2007 14:17:01 -0500, "Mark Johnson"
wrote:

I was just going through some old emails, and saw a few comments on this
bench I posted a few years ago, so I thought i'd follow up. I built this as
an experiment in June of '04 out of the Borg's finest tubafour stock using
pinned and wedged M&T joints with no glue or finish. After 3 years of full
exposure, it split apart this summer. The pinned joints held up just fine,
and the wedged tenons in the vertical faces are still good. The wedged
tenons in the horizontal seat rotted out, and the end mortices obviously
failed. A better outdoor wood and a few minor design changes should last a
bit longer.

-MJ

Geez, Mark..... a little fixup and that bench would be able to see a
lot more ass before it's time to send it to the woodstove.....

ROY!

It's a darn good looking bench though Mark...
Did you put any waterproofing on it?

--
Kate
______
/l ,[____],
l-L -OlllllllO-
()_)-()_)--)_)

The shortest distance between two points,
can be a lot more fun in a Jeep!

"Mark Johnson" wrote in message
. ..
I was just going through some old emails, and saw a few comments on this
bench I posted a few years ago, so I thought i'd follow up. I built this as
an experiment in June of '04 out of the Borg's finest tubafour stock using
pinned and wedged M&T joints with no glue or finish. After 3 years of full
exposure, it split apart this summer. The pinned joints held up just fine,
and the wedged tenons in the vertical faces are still good. The wedged
tenons in the horizontal seat rotted out, and the end mortices obviously
failed. A better outdoor wood and a few minor design changes should last a
bit longer.

-MJ

Hmm... The end mortises failed... I have no idea if this is a valid
point, but it seems to me that there's a strip only 3/8 or so thick holding
the outer frame to the inner slats of the seat - that is, all the stress is
concentrated on the upper face of the mortises when you sit on the edge of
the bench. Would it make sense to have asymmetric mortises, so that there
is a thicker bit on the top side? After all, the stresses are all gonna be
downward, so a mortise in the center of the endpieces seems like it might
be wasting some of the strength of the endpiece. And, of course, there is
the matter of stress concentration at sharp corners - possibly a rounded
tenon would help keep the wood from splitting like that - in general, it
seems to me that if the principal stresses on a M&T joint are gonna be
perpendicular to the thin side of the mortise (as in this case), a rounded
tenon (e.g. oval) would inhibit the formation of cracks starting at the
corner of the mortise. I'm no experienced woodworker, but I do know a
little bit about how holes concentrate stresses in materials (though this
could also be a matter of a little knowledge being a dangerous thing).

Hmm... The end mortises failed... I have no idea if this is a valid
point, but it seems to me that there's a strip only 3/8 or so thick
holding
the outer frame to the inner slats of the seat - that is, all the stress
is
concentrated on the upper face of the mortises when you sit on the edge of
the bench.

SNIP

I will second this. These were my thoughts when I saw the picture as well.
Although weather contributed to the bench's demise, it was most likely a
design flaw that resulted in the failure.

Switching the direction the tenons run (vertical instead of horizontal)
might help.

Actually, I've been working out and bulking up. I'm almost back up to my
college weight. 150 lbs, here I come.

-MJ

"RonB" wrote in message
...
"Mark Johnson" wrote in message
. ..
I was just going through some old emails, and saw a few comments on this
bench I posted a few years ago, so I thought i'd follow up. I built this
as an experiment in June of '04 out of the Borg's finest tubafour stock
using pinned and wedged M&T joints with no glue or finish. After 3 years
of full exposure, it split apart this summer. The pinned joints held up
just fine, and the wedged tenons in the vertical faces are still good.
The wedged tenons in the horizontal seat rotted out, and the end mortices
obviously failed. A better outdoor wood and a few minor design changes
should last a bit longer.

-MJ

Uuuuhhh......Mark.

How to say this.

Trying to be polite.

Have you been pushing away from the table when you should?

RonB

Attached is what passes for plans here. As for the smokers, the kids got
more use out of it in the back yard.

-MJ

"Morris Dovey" wrote in message
...
Mark Johnson wrote:

snip

| tubafour stock using pinned and wedged M&T joints with no glue or
| finish.

snip

| A better outdoor wood and a few minor design changes should last a
| bit longer.

Agreed. I still admire the design - and I'd (still) be pleased to have
a set of drawings for the original design. :-)

(I thought you were going to keep this on a covered porch for
smokers.)

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

No glue, no finish. I wanted to see which parts of the traditional joints
failed first.

-MJ

"Kate" wrote in message
...
It's a darn good looking bench though Mark...
Did you put any waterproofing on it?

--
Kate
______
/l ,[____],
l-L -OlllllllO-
()_)-()_)--)_)

The shortest distance between two points,
can be a lot more fun in a Jeep!

"Mark Johnson" wrote in message
. ..
I was just going through some old emails, and saw a few comments on this
bench I posted a few years ago, so I thought i'd follow up. I built this
as
an experiment in June of '04 out of the Borg's finest tubafour stock using
pinned and wedged M&T joints with no glue or finish. After 3 years of
full
exposure, it split apart this summer. The pinned joints held up just
fine,
and the wedged tenons in the vertical faces are still good. The wedged
tenons in the horizontal seat rotted out, and the end mortices obviously
failed. A better outdoor wood and a few minor design changes should last
a
bit longer.

-MJ

Mark Johnson wrote:
| Attached is what passes for plans here. As for the smokers, the
| kids got more use out of it in the back yard.

Thanks - I've been looking at the original photos ever since you
posted them thinking that I'd like to build a pair of similarly-styled
benches for indoor use.

Now that you've identified the vulnerable points, I may give it a try.

I'm pretty sure I can't improve on the style - but perhaps I can help
the durability a bit.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

"Mark Johnson" wrote in message
...
Actually, I've been working out and bulking up. I'm almost back up to my
college weight. 150 lbs, here I come.

-MJ

Oh.

OK.... Must be the wood.

RonB

Mark Johnson wrote:
The wedged
tenons in the horizontal seat rotted out, and the end mortices obviously
failed. A better outdoor wood and a few minor design changes should last a
bit longer.

If you have people sitting on the edge of the bench, all that weight
will be transferred (with a twisting moment) to the M+T joints nearest
to that edge.

It seems like this is asking for trouble without some further form of
reinforcement.

What about some dowels or loose tenons between each outer board and the
next board in? In keeping with the "no glue" nature of the piece they
could be just left loose, but if they went a couple inches into each
board they could add a lot of strength.

Chris