Weight estimates

[iconicflux]

I've been working on a spreadsheet for calculating estimated weights and figured I'd work up a comparison on techniques based on a 3' x 3' section.

The "foamie" assumes a 2x3 top and bottom plate with 1/4" bb stringers. I *think* it's pretty much how the XPStream was built except he used 6oz cloth which would mean more resin required.

Studded assumes 2x3's on top and bottom with 1x3' studs (could use 2x3 studs for a little more weight).

CDX sandwich is Tony's technique here with inner 1.5" cdx cutouts and otherwise filled with foamular then 1/8 bb on either side. Tony generally uses a 3" outer rim I think but it seemed more fair to gauge using the internal sections.

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Let me know if I got something wrong. Tony's technique seems like it should be lighter so I'm wondering if I went wrong somewhere.

("quantity" is square feet)

[tony.latham]

Here's what I suggest for sandwiched wall construction:



So you may be missing an exterior skin. I like 1/4" over 1/8" for the exterior because of the added meat for holding screw heads.



Tony

[iconicflux]

Ahh I see where I went wrong there. You have 2" spars/foam for the roof and the walls are 1/4" external and 1/8" internal. Thanks!

Let me redo this and if it looks good I'll modify the original.

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Here's what I suggest for sandwiched wall construction:



So you may be missing an exterior skin. I like 1/4" over 1/8" for the exterior because of the added meat for holding screw heads.



Tony

[tony.latham]

with inner 1.5" cdx cutouts

What do you mean by this?

Here's what my last skeleton looks like:



Tony

[iconicflux]

On either side of your cutout you seem to have a minimum 1.5”. Like, if you drew a line it would be at least 1.5” or 3” total.

Do I used 1.5” of cdx showing around all borders of the hypothetical 3x3’ piece. It’s hard to figure out for yours given the curves. If you have an actual wall weight and dimensions then I could probably make it more accurate.

with inner 1.5" cdx cutouts

What do you mean by this?

Here's what my last skeleton looks like:



Tony

[noseoil]

This is 17#, see my build thread for more information...



I use 1/8" Baltic birch both inside & outside for skins on these panels. Didn't help much, rolling weight as built was 1660# for a 5x9x4. With brakes & a 3500# axle, it's closer to 1700# now. What I learned from running a spreadsheet, it's better to weigh components as you go than try to calculate all of it in advance...

[tony.latham]

If you have an actual wall weight and dimensions then I could probably make it more accurate.

I don't have a weight for this last set of walls.

With my first build, I used 1x4's for the skeleton.



That method takes a lot more labor and lacks the design element potential that plywood has.

I have always thought that Tim Curry's (aka noseoil's) skeleton shows the potential for weight reduction with sandwiched walls.

Tony

[S. Heisley]

A 1x2" skeleton frame with 1/8" plywood inside and out will work just fine and save you both weight and money. (I think I used 1x3" around door openings.) The key is using Titebond glue as well as screws and possibly a good epoxy for strength. You can also use PMF (Poor Man's Fiberglass) instead of epoxy to strengthen and provide some waterproofing. Take a look at what our dearly departed "angib" charted for us about weight: http://tnttt.com/viewtopic.php?f=21&t=60392