by mezmo » Wed Aug 24, 2011 9:47 pm
Hi GPW,
Just some more thoughts on the Foamstream Construction.
I vote for the original rounded shape. Much nicer looking,
and the angular/flat sided version telegraphs "space constriction".
I'd lobby for going with the laminated 3/4in 4inch wide ribs. On
second thought about them they could be fast and less hassle
and not necessarily need a lot of clamps. [I know this is easy to
say/suggest since I'm not the one doing the work, but this is the way
I'd approach it.]
***The forum won't open up for me tonite as I'm
writing this, [08/23/11] so I'll go from memory on what you're going for.***
FIRST
I think a "space frame" [skeleton?] of the laminated ribs& 'boards' would be very
beneficial. It'd make it easier to mount interior amenities and any
electrical needs and eliminate the tediousness of locating and installing
hard points within the foam for any mounts or attachments.
I'd use a center top flat "ridge board" - a 4in wide
laminated board of three 1/4in plywood strips. Its length being,
from the rear end of the roof to where it joins the front quarter upper half-
hemispheric section in the front. In the center lamination of that, before
lamination, cut 1in deep by 4in wide cutouts centered and spaced where
you want the ribs to be, this will act as a mortise - and in fact becomes a
mortise when laminated between the top and bottom 1/4in plywood
lamination strips.
SECOND:
For the ribs: Laminate these as identical half ribs. Make at least four
additional half ribs to act as bottom plates/base and mid height
horizontal rails for the front curved lower section of the Foamie body.
[Don't forget some straight boards for a center upright between
them and as many intermediate uprights you want there.]
Make a jig for the correct arc - estimated as a 1/4 circle arc.
Use a sheet of 1/2 - 3/4in ply as a jig base with several @ 6in long 2x6 pieces
screwed to the base from underneath it to define the "radial end points"of/
from the center point from which you are drawing the arc. This is
assuming a radius of ~ 3-4ft representing 1/2 the body width.
- The exact radius depends on the final decided width, minus 2in for
1/2 the width of the 4" wide centered "flat ridge board". On the top end of
the half ribs, extend the center 1/4in plywood piece lamination
7/8in beyond the top and bottom lamination strips. This will act as a
"wide" tenon to fit into the "flat ridge board's"corresponding 4in wide
'mortises' on final assembly of the rib skeleton. [You also
could do the same on the bottom end of the rib with a longer tenon
[4 - 6in] if you wanted to use a full width tenon to attatch the bottom
of the rib to the lower wall section uprights/mid-rail with a corresponding full width
'mortise' in it, or to possibly attach the sides to the floor.] 'Need to
mention that you also need to make as many lower wall flat/straight
side wall uprights as you have curved ribs, and horizontal base and mid-rails for
between the uprights&ribs pieces.
FEWER CLAMPS:
To not need to use a bunch of clamps: First,
put 1-2 layers of Glad Press-n-Seal plastic wrap on the base, tight into the
'radial end point's' and base juncture angle and tight against
the 'radial end points" with a 2-3in overlap at their end, before putting the first layer/layers of
glued plywood strips on the jig. Have the strips rest on edge
against the jig base and their 4in width resting and bent against the "radial
end points" on the jig. Then use small brass or aluminum
brads/nails or screws to hold the 1/4in plywood strip laminations
together while the glue you've applied dries and sets the curve. These can
just remain in place once the glues dries/sets. REMEMBER: These fasteners
MUST NOT PIERCE the total thickness [or interior face ply] of the 3 ply lamination made
up by the 1/4in plywood strips - or - i.e. either use 3/8in long fasteners if you
use them for laminating the 1st two plys/layers together, and the last ply/layer
layer to the resultingtwo ply/layer piece or 5/8in long fasteners if you just fasten
all 3 layers together at once for the total 3/4in thickness of the lamination.
ALSO:
The heads of the fasteners should be flush with the top of the
ply they are applied through. Once the three 1/4in plys are glued, bent and
fastened together to make the 3/4in laminated board/rib,
then cover that resulting laminated board/rib
with 1-2 two layers of Glad Press-n-Seal plastic wrap, have @ A 2-3in overlap
on the 3/4in side of the newly laminated rib with the rest of the Press-n-Seal
smoothed against the 4in width of the newly laminated rib and then snugged
into the angle where the laminated piece rests on the jig base and earlier
laid down Press-n-Seal layer on the jig base and then the
remainder of this new Press-n-Seal layer smoothed tight onto/against the jig base.
The Press-n-Sesal will stick to the wood [and itself] and prevent you from gluing
all the boards/ribs together into one big piece, AS LONG as you DO NOT PIERCE the
plastic wrap 'layer' between each laminated board/rib that you are
making. Then, repeat the process. Just form the next board/rib on top
of the one you just completed as it will have the same curve. Just keep
aware of the working times of the glue you use and be sure to
locate and wipe up stray glue spills and such. You'd only need
3 - 5 clamps max with this method, one on each end and one
in the middle as a minimum. The small fasteners are taking
the place of multiple clamps. Use as many of the fasteners
that will just do the job for you. Since they are brass or aluminum
they can remain w/o rust problems and the heads will be external and
covered by the foam panels once they are attached and are thus out of sight
ALSO:
When you are doing assembly of the skeletin frame, if they don't fit
easily when you dry fit them, just sand the tenons a little and perhaps
slightly bevel the tenon at the sides ever so slightly, then it should
fit ok. Once the fit is to your satisfaction, you can then glue it up. You
can clamp the joints if you want, but drilling a pilot hole and using a
couple 5/8in brass screws from the top will hold the joints in position.
And I'd reinforce the outside of the joints with fiberglass tape and
glue/epoxy also - trying to tie all the pieces together into "one" space frame.
THIRD:
For the front quarterspheric shaped piece, here
are a couple of approaches:
APPROACH A: Make a space frame of galvanized metal
electrical conduit. Using appropriate lengths of galvinized metal electric
conduit, bend them to the appropriate 1/4 circle radius for
the 'longitudal'/vertical positions - 5 -7 in total. These will be
mounted upright on the interior side of the space frame. Then
bend 5 semicircles of the condit using the same radius plus
2-3in on each end to flatten for use in attachment. These
semicircles will provide a top and bottom and center half
hemisphere locations with intermediate supports between the
bottom and center and top and center. The 1/4 circle radius
arcs used for the vertical/longitudal pieces are spaced out similarly
as the semicircles. Wire tie these together in a criss-cross pattern
or drill holes and wire or bolt together with lock washers/nuts using
the just drilled holes. This results in a rigid 1/4 sphere space frame
based on radial arrangment of the bent conduit ribs set at 90degrees
to each other. but with irregular spaces between the ribs.
AN ALTERNATE way to fasten the bent conduit ribs would be to
do the longitudinal/vertical ribs as described, but bend decreasing
length semicircular latitudinal/horizontal ribs at a set spacing from
the bottom to the top. Fasten together as described. This would
result in a space frame looking like a conventional 1/4sphere piece
of a globe with latitude and longitude lines. The voids between the
ribs would be more regular in shape but decrease in size as you go up.
NOTE:
An additional consideration is how you would attatch the conduit
space frame to the rest of the body. One way would be to
extend the end lengths of each conduit bent piece 2-3in and
then flatten those ends of each of that 2-3in in the same plane as the
wall/roof area they would teminate/attatch at.They could be fastened
together by drilling a hole in the flattened ends and then bolt them
all together at one point [for the radial arrangement] on both ends of
the semi circular pieces, and at the top end for the vertical/longitudinal
1/4 circle radius pieces. How the edges of the conduit space frame attatch
to the mating wall/roof area depends on how those are configured. The piece
abutting the first laminated vertical rib(s) could be fastened with appropriate
"U" shaped long legged brackets ~ 5in long~ with a couple screws on each
leg, one bracket leg on each face of the laminated rib. The curved lower front wall
could be made with a continuation of the verticle/longitudinal front
conduit curved conduit ribs [with a couple more corresponding semicircle cross
pieces] to the floor and their flattened ends bolted to the floor perimeter. Or, to a
semicircular front base made of curved laminated plywood ribs mounted
sideways as bottom and mid level horizontals connected by vertical laminated
uprights. The vertical bent/curved conduit ribs could have their flattened 2-3in
ends act as tenons into the curved laminated horizontals at mid-level or you
could attach the bottom/first semiicircular horizontal conduit rib with the afore
mentioned brackets to the midheight curved front wall top.
To finally form the front top half of the Foamstream body, infill the voids
in the space frame with appropriately shaped pieces of foam board
wired/glued in place. Fill in cracks with a spray foam and trim to as smooth a
surface you can.
A WILD IDEA: [AKA:" USING OUR NOODLE"]
Instead of piecing together various sized flat foamboard pieces cut
for infill why not use a sufficient quantity of those foam "noodles"
that they sell as a child's pool toy or swimming aid, and wrap them
around the conduit space frame 'log cabin, log style' from bottom to
top, Each course length decreases to fit the 1/4 sphere space frame
as you go up. These can be wired to the frame with aluminum
or brass wire and glued together. These foam 'noodles' bend easily and
have a center hole their whole length. They could be cut in half
lengthwise to reduce the quantity needed. Then infil any gaps
with some form of spray foam and fair out from there. You may
even be able to cut a couple of them radially into strips to use as "chinking"
between the "courses". Of course you may need to adjust the space
frame dimensions a bit so that the exterior of the 'noodle' foam covered
conduit space frame merges/blends with the rest of the body walls
correctly.[You could leave the 'corrugated' look of the stacked foam
noodles and just canvas/glue etc. over them for a beehive look -
<Here's a stretch: Scientist have found that such parallel rounded
ridge forms on whale flippers are much more hydrodynamically efficient
that smooth flippers - so would that translate to more 'aero' for the
Foamstream? Ha!>
APPROACH B:
For the front 1/4 sphere shape and semicirclular front bottom wall:
You could also laminate up 3-5 additional 3/4in ribs and bottom wall
pieces and miter them at the top where they'd meet the center "flat
ridge board". Use mortise and tenon joints here too to join the sections
together. - or - use a semicircular 1/4 in plywood "D" shaped 'joining' plate
to join the front radially placed ribs together and to the "flat ridge board".
The tenons probably should be longer and the mortises correspondingly
'deeper' when joining the top curved ribs to the bottom wall sections and
also for the afore mentioned joining plate for the front radially placed ribs
and the front of the "flat ridge board". Fill in the angle areas between
the ribs joining at the top with triangular 1/4in plywood pieces that fit exactly
over and under the 1/4in plywood "D" shaped 'joining plate, and thus make
the ribs and the "D" shaped 'joining plate' essentially all one piece .
And, of course, all the outsides of these joints should be also be reinforced
with fiberglass tape and glue/epoxy.
Sorry this has been so long and 'wordy' - I'm having computer
problems and can't scan or upload/download scans or pics at the
moment so I had to go the descriptive route - hard to be concise
when trying to be precise it seems!
Cheers,
Norm/mezmo
If you have a house - you have a hobby.
More contact between the ribs and foam shell ... more gluing surface!!! 
So came up with a simple guide for the router .. Just some scraps to make the job a little easier ... 
