Boat trestle (sling) design
Henry Law
were lots of opinions - very helpful, thank you - but nobody knew of a
trestle design available on the web. So I've put mine up.
If you're interested, it's here:
http://www.lawshouse.org/rowing/trestle.pdf
If you use it - and particularly if you have suggestions to offer -
then please mail me directly. The reply-to address in this article is
valid, but I look more frequently at hjl@<the same domain>
Henry Law <>< Manchester, England
Neil Wallace
"Henry Law" <lawshous...@btinternet.com> wrote in message
news:om59mvsne08ghnoq8...@4ax.com...
> A while back I asked for information and opinions on trestles. There
> were lots of opinions - very helpful, thank you - but nobody knew of a
> trestle design available on the web. So I've put mine up.
>
> If you're interested, it's here:
>
> http://www.lawshouse.org/rowing/trestle.pdf
>
Henry,
they are trestles of great beauty - what a craftsman.
Neil
John Mulholland
Brilliant, with excellent instructions! But I do have one possible
improvement! If you add a diagonal strut across the inner frame the trestle
will resist longitudinal movement better (using geometry rather than joint
strength). We have a couple with this enhancement and, if I remember my
camera, I'll try to get a picture tomorrow evening.
John Mulholland
Hexham Rowing Club
"Henry Law" <lawshous...@btinternet.com> wrote in message
news:om59mvsne08ghnoq8...@4ax.com...
mick allen
comments from a lurker:
1/i have noticed that trestles are often used outside on uneven
ground. that means only 3 of the 4 legs will be under stress, and that
flats on the leg bottoms will increase the likelihood of only 3
touching.
so diag bracing is imperative to reduce racking over time(both frames)
and minimizing leg bottom flats(try none and hope the boathse floor
will stand up) so that some varied leg depth is possible(often in
grass or dirt) with full contact. (sandwich thin ply gussets betw rail
and leg, or x strapping on opp side outsides, or inline wire or say
spectra x brace)
2/ with a better(just a loop or tied or better fasteners, or epoxy
glued/wrapped) web attachment, the 2 extra top rails can be
eliminated. wt saving.
3/viewed from the side, the trestle is 3 members thick. outside rail +
leg + offside rail. there are several ways of reducing this
thickness. (Assuming space is an issue in the boathse or the
trailer/truck/car)
a/ stagger the opposite side top and bottom rails so that one trestle
interlocks with another giving an average of 2 members wide. for
example, if the bottom rails are 2 ½ in wide, one should be say 3 in
off the floor and the other should be 3in + 2 ½ in, say 6" clear off
the floor. the webbing should go over the top of the inside frame's
legs and its top rail should be dropped at least 2 ½ in to miss and
engage the next trestles outside frame high rail.
b/ simply make the inside frame with all flush members. use thin ply
diag gussets on the corners for the bracing and to keep wt down. paint
ply for longevity.
c/ have light min construction ‘travelling trestles' made out of 1"x2"
legs on the flat with the hinge located on one side so legs are not
weakened. good hinge attachmt req'd. flush inside frame option or
staggers. use a strong wood.
d/ to make just one member wide: make both inside and outside frames
flush framed. inside frame is fairly straight forward but includes
horiz strut inline with hinge to brace itself but more importantly the
outside frame as well. outside frame: top rail is say 2x2 and is 2"
higher than inside frame( sling is webbing so ht difference doesn't
matter) to overlap, X – brace to the hinge strut height w/ thin galv
strapping on one outside, and X-brace down from the hinge to the near
the leg bottoms on the opposite of its(the outside frame still) legs.
e/other thought - make i/s frame at least 1/4in clear(use spacers on
legs) on ea side smaller than o/s frame so that webbing can easily get
wrapped in the space and you still just slam them together.
some ideas,
-mick allen
ps question - how important is the double sling? would it be alright
to make one frame w/ no top rail but web sling instead and 2legs
joined at bottom from the hinge location to swing out - like a 'V'
from the hinge local. would make a single sling tripod one or 2
members thick.
i guess one could actually make either side the V. if the sling side
was the V, would stack better, whereas the other would be best stacked
on sides.
Henry Law
wrote:
>comments from a lurker:
>
>1/i have noticed that trestles are often used outside on uneven
>ground. that means only 3 of the 4 legs will be under stress, and that
>flats on the leg bottoms will increase the likelihood of only 3
>touching.
>so diag bracing is imperative to reduce racking over time(both frames)
OK, so you're the second person to suggest this. I can see what mark
3 is going to look like (the drawing is of mark 2).
>d/ to make just one member wide: make both inside and outside frames
>flush framed. inside frame is fairly straight forward but includes
>horiz strut inline with hinge to brace itself but more importantly the
>outside frame as well. outside frame: top rail is say 2x2 and is 2"
>higher than inside frame( sling is webbing so ht difference doesn't
>matter) to overlap, X – brace to the hinge strut height w/ thin galv
>strapping on one outside, and X-brace down from the hinge to the near
>the leg bottoms on the opposite of its(the outside frame still) legs.
My spacial imagination is pretty good but it's not good enough to
envisage this. Any chance of a sketch somewhere? I have a version
that is exactly 41mm thick; the inside frame fits entirely inside the
outside one, and the result seen from the side is a parallelogram
rather than a rectangle. I showed the prototype to my club mates and
they reckoned it wasn't as stable. Heavier too.
>e/other thought - make i/s frame at least 1/4in clear(use spacers on
>legs) on ea side smaller than o/s frame so that webbing can easily get
>wrapped in the space and you still just slam them together.
These get slammed as they are .. believe me.
>ps question - how important is the double sling? would it be alright
>to make one frame w/ no top rail but web sling instead and 2legs
>joined at bottom from the hinge location to swing out - like a 'V'
>from the hinge local. would make a single sling tripod one or 2
>members thick.
I think what you're describing is "type A" in
http://www.lawshouse.org/rowing/trestletypes.gif ; have a look and
see. We have some of that kind, but they're much lower and the
general feeling was to have type "B".
Thanks for the suggestions. One of the concerns in evolving the
design is that it should be possible for less skilled woodworkers to
make.
Henry Law <>< Manchester, England
Hamilton Richards
ne...@lawshouse.org wrote:
It looks very nice, but there's one hazard that would never have occurred
to me had it not happened to a boat of mine. Note that, in the picture of
the trestle, the webs on which the boat rests are flat, and now imagine a
boat resting on flat webs as it is hit by a gust of wind crosswise. The
boat can roll right off the trestle onto the ground!
Usually, of course, the webs are not flat, so they cradle the boat and
keep it secure. But a series of crosswise gusts can repeatedly lift one
side of the trestle, enabling its feet to gradually spread apart,
gradually flattening the webs until the boat rolls off. As I say, I had
never thought of this until it happened to my boat.
So I would add pair of straps at the bottom of the trestle, short enough
to prevent the legs from spreading far enough to flatten the webs.
--Ham Richards
Austin Rowing Club
Austin, Texas
PS Carl Douglas, if you're reading this, the boat in question was the
predecessor of my CDRS 1X. Had it been a CDRS boat, it would no doubt have
survived the fall with no damage!