ultralight plywood?

[Colorado Hick]

Im trying to figure out how to do a really light weight titan39.

What do you all think about ultra light plywood? https://ultralightply.com/ ? Its only costs 10% more then baltic birch in my neck of the woods.

[Tom Smit]

It appears to be okay. However, it is difficult to see how thick the outer veneer is. If it is only film-thick, the it would be a no-go, unless one removes that veneer where a panel is to be glue to. Perhaps you could order the $15 sample pack so that you can check to make absolutely sure that the outer veneers are the same thickness as the core veneers.

[Seth]

Love the idea. I used Douglas Fir for similar reasons, but ultimately wanted Poplar which was way too expensive. I've seen threads over the years where people built a T39 out of 3/8 ply with good results. Lot's of options to reduce weight. Give it a go and please keep us posted. Thanks for taking one for the team!

[Bruce Weldy]

If you blow up the picture of the 1/2", it looks to have a thin veneer on top and bottom.....and boy, that's expensive!

[Seth]

Looks the same as the BB in my neighborhood with the outer layers slightly thinner than the inner, but not a paper thin cosmetic veneer. However, my eye's aren't the best.

[Bruce Weldy]

Looks the same as the BB in my neighborhood with the outer layers slightly thinner than the inner, but not a paper thin cosmetic veneer. However, my eye's aren't the best.

Screenshot (392).png

The veneer on the 1/2 inch looks really thin compared to the 3/4.

[Colorado Hick]

The other thought that occurred to me is using 1/4 for internal baffles, and instead of gluing them on the end grain I could route in 1/4 " deep channels for everything. It seems with that style of construction having a thin outer layer would not be as much of a liability? THe baffle - to baffle edge joints would be tricky but could be strengthened with a small piece of ripped pine at along the inside corners. would that negatively impact the sound volume or quality?

[Bill Fitzmaurice]

That will work, but you double the build time, and if the panel placements aren't precise you won't be able to get the second side on. If you end up with a thin veneer use screws when assembling so you're not relying purely on the adhesive.

[Rich4349]

Strictly in the interest of science (lol) and not necessarily real world results, you could pursue laying up some sheets of 1/2" foam with a nice consistent layer of Titebond glue and bedsheets, also known as poor man's fiberglass. "A lot of people are" making camping trailers and other items from this. Each sheet provides (some!) tension to limit how much the foam can bend away from it. Is this amount of tension enough to mimic plywood's rigidity? Probably not, but is it close enough to work as a well braced folded horn enclosure? This is where YOU come into play! lol Give it a whirl and report back!

This guy conducted VERY scientific experiments to test the rigidity, such as placing old car parts and rocks onto a small supported piece.

https://www.youtube.com/watch?v=ZJK2131vHak

Obviously (or IS it?), one would lay up sheets or at least full size pieces first, then glue it up into the enclosure. (As opposed to making the horn from foam then gluing up afterward. That would be a really bad idea.)

THESE folks used an iron to get a really smooth and level finish while the glue was wet / curing.

https://www.youtube.com/watch?v=S3JIyhbdi-Q

I'm not saying this will work; rather, it's just a more Seth-y thinking out of the box approach.

And if you wanted to beef it up you could try two 1/4" layers of foam with an extra layer of sheet between the two.
Sheet/glue/foam/glue/sheet/glue/foam/glue/sheet.
A plywood version of poor man's fiberglass.