Foam Domes

[WoodSmith]

Let me start by apologizing if this has been covered in another place & I didn't find it. I am working my way through the (several) monster threads involving Foamie construction and have not seen this covered.

It seems that a lot of folks are looking for more complex shapes than simple curves. While reading through the FoamStream thread last night I came across GPW's need to bend or build a 1/4 sphere. The thought of a geodesic dome struck me as a way to approximate this. I watched a boring but instructional YouTube video https://www.youtube.com/watch?v=vv01yWHo_1o on domes a while ago and drew up in AutoCAD some triangles of the appropriate size. I printed them and together with my 8 year old daughter cut them out and taped them together into a surprisingly strong (for paper) structure.

I know GPW is searching for the Holy Grail of Foamies in heat bending, I'm not sure how much curve that will get.

A little more searching shows that more, smaller, triangles more closely approximates a sphere - so, as with most things, a trade off is made. How many pieces do you want to cut and assemble -vs- how "perfect" do you want your shape to be.

Skining the outside shouldn't be too difficult, careful thought prior to final assembly would allow you to use the skin to assist with the assembly. Unless the canvas has a LOT of stretch, I don't see it being possible to do it with no seems. Canvasing the interior - not sure how that would work. On the other hand, inside you are less worried about seems, and really, this would not be a large portion of the design, usually I would think just a 1/4 sphere in front, (and maybe a second in the back).

Any thoughts?

Glen

[GPW]

Glen , wish I’d talked to you earlier .. That’s a Great idea !!!  ... would have been easy to assemble a half dome for the FS nose... Would have been easy to blend into the rounded top.
Please continue with this if you like , It sure would be interesting to hear and think about making in foam . Just guessing you could make just one design triangular piece with the proper edge angles , and just pop em’ together eh ...??? Just assuming ( ) the angles would change with the radius of the dome..

Great idea for streamlining too .. So many possibilities !!!

CU, Glen

[WoodSmith]

Glen,

I had a hard time getting to sleep last night as I wanted to post this and hope to help your FoamStream. When I got online this morning, I went to your profile and got a bit deflated when I saw the picture of it in your profile. (It looks great BTW.) I often lose track of the fact that what I'm reading NOW may have been posted 3 years ago.

Just for the record, the triangles are NOT all the same size. The dome my Daughter & I constructed had 2 different shapes. One is Isosceles and one is an Equilateral. To get a quarter sphere, I think there would be even more. I'm not sure what the number of shapes is for higher order (more, smaller triangles) domes.

Glen.

[mezmo]

This type of dome construction might be much simpler
to do I think:
http://www.geo-dome.co.uk/trap_tool.asp

[GPW]

Well then, that seems a bit More complicated that I was expecting ... Being a much better carver than a mathematician ... ( by a long ways )

[WoodSmith]

I think the geodesic construction is fairly straightforward. For a "2v" dome, there are TWO different shaped triangles for the whole thing. I came across a nice calculator while looking for more info: http://www.desertdomes.com/domecalc.html

Since I am a lazy so and so, I looked into a way to make it easier to construct. Especially since I was trying to keep the attention of two kids with widely varying attention spans (SQUIRREL!). I think that what I came up with would translate very well to the construction of Foam Domes. By "pre-assembling" seven of the triangles and NOT cutting them out, you can print or draw if necessary, then folding on the cut lines you cut the assembly time drastically.

I am attempting to attach a PDF of what I came up with, the file exists here: https://dl.dropboxusercontent.com/u/11255798/GEODESIC%20Layout1%20%281%29.pdf

Print six of these and carefully cut them out, then fold on the lines. Glue or tape FIVE of them where the little dart is.

ANNnnnnd I'm confusing myself. I'll stop now and post some pictures.

[WoodSmith]

To make a one half sphere:

Print out SIX:


Cut fold and glue or tape FIVE:

[GPW]

That’s pretty Cool !!! Thanks Glen !!!

[WoodSmith]

Glue up 5 like this:


I used some small aluminum squares and paper clamps to get a good bond.

Then assemble those 5:


Be careful to keep the perpendicular lines lined up and keep track of where they all glue together. I've already fixed my miss-spelling of Isosceles, I'll try to add a guide to keep them oriented.

I'll post the other pics tonight, this "work" thing is interrupting my messing about.

The Sixth part gets trimmed. It only needs to be the 5 Isosceles to make a pentagon. When you trim it off, be sure to leave glue tabs.

Once I get my manilla folder version made, I'll add my thoughts on construction in foam.

[WoodSmith]

The assembly gets a little more floppy each time you add a section. Here I am gluing side number 5 in:


The sixth piece gets cut down a little from the pattern, but not much:


While it was flat, I added a red line for cutting to get to the quarter sphere that will be more likely to be used on a trailer:


I did not glue this pentagon, rather I cut through the glue tab on the perpendicular line, then slid the cuts into each other and taped it down. The glue tabs are there, just folded under.

Then started gluing it in:


I think it is easier to do it in this order rather than glue #5 to #1, then hope that #6 fits in place. Especially since this is a floppy model and I'm not that good at folding on the lines.

[WoodSmith]

The assembled dome:

(Edited to add image.)

Now that I have fully assembled the dome, I see that cutting the dome on the obvious joints will produce a ... less than pleasing asymmetry in the quarter sphere. A minor setback, but if you intend to ONLY build one quarter sphere, you will have substantially more unique shapes to create. On the other hand, If you want to have a rounded front and a rounded back, build the dome (half sphere) and cut it in half. I suppose that you could build up the flat sections and knock down the peaks to fair out something closer to a sphere also.

[aggie79]

Here's another approach - no math needed: http://www.i-domehouse.com/parts.html The shipping costs might be a little expensive though.

[lthomas987]

Here's another approach - no math needed: http://www.i-domehouse.com/parts.html The shipping costs might be a little expensive though.

The shipping is expensive, but I think it would be possible to kerf and curve foam in segments like that to make a rounded dome. Maybe not on the breadloaf corner scale but on a whole trailer front scale.

[Glenn Butcher]

We lived in this thing for a couple of years:



Same concept as i-domehouse.com, but fabricated by a company in Mississippi, segments shipped out to Kwajalein. They were a test of low-maintenance housing alternatives; the previous project was condemnable, as the steel studs were rusting into piles in the aluminum-clad walls.

Quite livable, but a few challenges. I woke up one weekend morning to a horrendous banging; I ran outside to find the neighbor kid beating on the side with a golf club. I vectored him back next door to continue...

[WoodSmith]

So the thing that I think makes this exciting for foam construction to me is that the same kind of pre-assembled panel could be used full size. Depending on the width of the trailer, a set of triangles could be laid out on a single sheet of 4x8 foam. Cut out the outline, and then using the kerf method you folks have been perfecting, kerf the fold lines with the proper angles. (Which I still need to calculate or measure on the model.) Once a preliminary test shows the panel is good, the canvas could be applied to the outside, non kerf side, flat on the floor, bench, sawhorses -whatever.

The place I refer to as the dart in my model would hold a small amount of extra canvas. From reading the vast amount of information available, it appears that glue over glue is not recommended, so leaving an appropriate area for the dart might be a good idea. Once the glue cures, a razor knife cut along one side of the foam would allow the spare canvas to overlap when the foam is bent on the kerfs. Some Gorilla Glue in the kerf lines and a little more canvas fastening to attach the flap to the other side and wait for it to finish curing.

Canvasing the inside would be harder. I don't see a way to do it without a bunch of seams.