Thread: how to build a curved wall - not post. but a wall

Something like this

Bending Plywood (Long Way) 2400x1200x4mm | Trademaster

Originally Posted by China

Something like this

Bending Plywood (Long Way) 2400x1200x4mm | Trademaster

Thanks for that, that is bending in in XY axis only, I have no problem in producing something similar to the link but I need to make a ball, 1.9m in diameter

Originally Posted by Albert

I am in the middle of my next project, am trying to build a pumpkin cart bed for my daughter.

I have completed so far, and now I am stuck.

HOW DO YOU BUILD A CURVED WALL??? .....

Boat builders routinely build with compound curves, Albert. It might be worth reposting this in the boatbuilding subforum.

For gentle 3D curves you can try something like this with plywood


Otherwise you might need to go down the fibreglass road.

This is quite a challenge but nothing’s impossible if you’re shear bloody minded enough.
First thoughts are a pumpkin has sort of raised flutes.
Possibly more stringers like you already have at the base of each flute.
Then others at the top of the flute and an infill of strips as in a boat hull, then carved and faired.

Im thinking as I’m typing so bear with me.

How about an internal mould of each section, to help with replicating?
Then lay up strips like for a cedar strip canoe and shape externally.
Internal may have to be faired with bog or similar.
If it’s too much work after doing the first one it can be the buck to make a mould and go to Elan’s suggestion of sticky smelly goo.
H.

I am trying to stick with wood, fibreglass will work but it would be the last resort. I only need 3 of these walls so unless I go production otherwise cant see the value of investing in a good mold...

I have some ideas now, I will try something by utilising my existing mold and methodology I developed, I am already happy enough with the progress to date. the main structure worked out better than I expected, this is my first time making something curved. I played around with the pumpkin structure today by standing in the middle of it and rolled it around, if an adult can play in it, its strong enough to be a kid's bed.

Giant compound curves is a hell of a thing to pick for a first project...
I'll be interested to see what you come up with

Albert

Boat building jargon for what you want are:

• Cold molding, and
• Strip planking.

Good boatbuilders routinely get a "piano finish" on both inside and outside surfaces. It is not as hard as Elan infers.

Please note: one big difference between shipwrights and cabinet makers:

• one works with straight lines,
• one works with curves.

Elan, have you experimented with kerf-sprung seats like this?

Kerf Stool.jpg





















I made one for an insert seat panel on a stool; it looked great and the springiness felt great under hand pressure. When bum-tested, it creaked and groaned and quickly failed.

The X and Y-axis kerfs and 30 mm centres basically give you 27 mm "posts" on the top and bottom thirds of the seat thickness. This is what you can see and it looks good. But in the middle third of the thickness there are twice as many kerfs and those "posts" are now only 12 mm square, allowing for the kerf width. But within those "posts" the grain runs crosswise. There is not a lot of strength in 12 mm cross-grain. This is a fundamental design flaw.

Fill the kerfs with epoxy and you regain the strength but lose the springiness.

I haven't tried it, but the example in the pic appears to be made like an endgrain chopping board, so the "posts" are long grain, not short grain.

Use fabric? Probably need a few more curved vertical supports.

Originally Posted by elanjacobs

I haven't tried it, but the example in the pic appears to be made like an endgrain chopping board, so the "posts" are long grain, not short grain.

Yeah, I couldn't pick the grain from the pics.

But wouldn't that make it worse? Still got short grain from the bottom of the kerfs to the opposite surface. And all flexing action will be twisting against the side grain.

Albert, don't wooden barrels sort of resemble what you want to do.

Funny how you forget things as you get older.
A mate in Brisbane sent me a photo of what you’re making.
It was for a merry go round and was in fibre glass.
He’s a patternmaker like myself and was between jobs so with basically only hand tools had taken on to make all the rides for this fairground ride.
He never did tell me how he made the buck.
I guess in those daze we just made stuff and didn’t post lots of picks for feedback on faecebox how clever we were.
H.