I have been an AutoCAD LT user for 12 or so years. I have been using
CAD programs since 1986. Never have I run across and learned so quickly to
draw on a CAD type program as with Sketchup. 3D is SIMPLE with Sketchup. I
down loaded it years ago and removed it, down loaded it again and forgot
about it, uninstalled it once again and finally down loaded version 6 and
after putzing with it 2 or 3 more times discovered that it was OK.
Version 7 was released a few months or so ago and it is even better.
It seems that there are fewer errors and problems and designing on it now
seems very intuitive once I learned to assemble my drawings with components,
Anyway, you can now print drawings to scale in version 7. For
woodworking IMHO this was a major missing feature in the earlier versions .
It seems that I always needed to transfer a curve or something complicated
in full size scale to the actual wood. Now that is possible. So if you
have not upgraded to version 7, what are you waiting for?
I have version 7, but it still won't handle the simple shape I was
working on (with a different package) when your post popped up.
I'll put what I have so far on abpw, and perhaps you can tell me how I
can make it in SU7.
Draw the 3 straight line segments at the corners on each side. Draw
the arcs between them. Push/Pull on the surface to drag it out into
3d. Unless there's something I'm missing about the drawing, that's
an easy one.
You /are/ missing something. The (surface and matching plywood rib)
curve is a parabola with a curve length of exactly eight feet with the
focus at the point midway between the edges. There aren't any circular
arcs other than the ends of the small tubes, which haven't been
I tried making a cone and sectioning to produce a parabolic curve, but
still had the problem of making the length of the curve come out right.
'Taint as easy as it looks. :-p
powered pool company many years ago. We used metal coated mylar and set the
panels into a frame to support them. We thermoformed them in a vacuum
forming machine. The machine was home built.
We would cut the shape we wanted in metal and use that to form the plaster
mold. Mount that mold on the thermoforming bed and heat the plastic. Turn
on the vacuum and the panels were instantly formed. Trim them and collect
eight of them to make on parabolic reflector.
Ahhhh....., the wild visionary days of a mispent youth. Dreaming of riches
in the solar heating biz. But I got it out of my system a long time ago. I
am much better now. :-)
'Tis. You can see photos of a half-width prototype at
These are being used to heat the hot head of a fluidyne engine. You can
see a photo of a low temperature (and low-efficiency) prototype at the
and concept drawings of the next generation at
Converting the solar radiation to heat is easy - using the heat from a
concentrator with only 32 ft^2 of mirror to produce more than 1 hp is
I've considered it - and think it's a great idea for some applications
larger than the one I'm working on.
My goal is something simple enough that anyone, anywhere can assemble
with a screwdriver and have running in ten or fifteen minutes using a
single graphics-only instruction sheet.
Okay. I googled "google sketchup parabola" and got all kinds of
Normally I use sketchup to visualize, not necessarily get an exact
drawing. So something like that a simple arc would probably be fine
to get what I need from it. Now that I know I can actually generate
scale drawings I may use it a bit more for creating templates that
need to be exact. But my models are never complete. This is what I'm
working on now:
Not remotely complete as far as construction details. The edges of
the top are natural but a simple angle is good enough for modeling.
On the top those circles are dished out with the 'disher' I talked
about elsewhere, I could have spent time trying to figure out how to
model that but I don't care because I already know what it looks
like. The side panels are actually curved, wasn't sure how I was
going to actually do that so I modeled it flat to be sure that would
look good too. When I first headed to the shop a single column of
drawers spanned the whole width. After I decided to split it after
seeing how wide those drawers were going to be I went back and modeled
my concept for curving things to make sure that was going to look
right. I got what I needed out of it. I'm going to have a whole lot
of fun trying to fit those drawer fronts in a couple days though :)
The main thing that annoys me is the dimensioning tool that doesn't
move the dimension outside when there isn't enough room which then
I'd really like to see some photos of the finished top in place. That'll
be quite a feature.
Just the sort of intuitive thing that doesn't need any documentation!
There's a setting in there that will *hide* the dimension if it
doesn't fit... yeah that's useful.
It just downloaded an update and there's nada about what it updated.
Actually there's a better way of doing it so you don't have to type
that in. Go to Window -> Model Info -> Dimensions. Under Dimension
set to "Align to dimension line" to either above or outside.
'Outside' appears to just be below.
The hide function I was talking about is under "expert dimension
I don't know if it is a better way but as you point out it is possible to do
default them that way. Most often, the lettering between the arrows is the
best location. Personally I think a leader with the lettering to the out
side of one of the extension lines would be better.
Well thank you for that Tom!. Not quite what I was looking for but
certainly addresses my preference of location for the lettering. Being from
the old school way of training, to-square and triangles, I would prefer to
see the leader between the lettering and the extension/dimension line, but
this certainly addresses where I wanted to see the lettering.
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