Thread: Helix table help needed

After playing with a strip of paper , it looks like what Alex is saying is the way to go , its going to have to be built up in strips and grow horizontally out off the form. I think that suits vacuum , you would have to test it. maybe it would work doing it 50mm at a time .
Other ways, either clamps , or a metal band possibly. I like pulling lamination's with metal bands around a convex form. a clamp at each end with the right set up gives a lot of presure, its got to be a strong form though.

I saw this link that may help

Reinforcing Stair Stringers with Epoxy

The DVD that I have that does the staircase stringer with vacuum is here. It's by Darryl Keil and covers a lot of important info and is good, well worth the $ spent on it, if your interested in vacuum.

Darryl Keil - Working in a Vacuum Preview - YouTube

here is a picture from it. the lamination's are in the bag being pressed while the lot is clamped to the form.




Rob

Why don't you get a big fat stump and get to it with a rotary carver? There would be plenty of mulch left over.

Originally Posted by Sebastiaan56

Why don't you get a big fat stump and get to it with a rotary carver? There would be plenty of mulch left over.

Would that work, Seb? With all the short grain aligned the wrong way, it seems that it could be quite fragile. Or am I missing something?


Scally, please keep us posted as you go about identifying and solving the problems of this challenge. It is absolutely fascinating me. I hope it does not finish up in the too hard basket. But, it sure ain't easy.



Fair Winds

Graeme

I'd look at using female forms for the stringers - perhaps a length of PVC pipe and an old heavy cardboard drum as I've seen at Reverse Garbage. It may be possible to bag them, otherwise, you may be able to hold the laminations to the forms using some sort of stretch material, such as strips of old inner tube. You don't need a lot of tension to hold them in place.

I like the idea of building up from a female form.
Certainly lots of clamps especially trying to keep them aligned.
I don't have a vacuum press yet and hadn't planned on getting one just yet. How would you get the whole assembly into a vacuum bag?

A drum might work as a starting point. The final form will probably need to be built using plywood and timber so I could get the right dimensions and strength for clamping..
The Helix table has a wider diameter at the top so making a conical form seems the way to go.

A friend suggested carving it from a tree trunk. It was a scarey thought with so much wood to remove. There would probably be a strength challenge too.

No rush just yet so I'll keep scratching my head and tinkering around. If I make a form it would be tempting to make a few more helix bases??

I would build it like they build wooden propellers and propeller moulds.
This is done by stacking horizontal slices and offsetting them.
Here is a sample video. Not the best but will give the idea.
How it's Made: Marine Propeller Pattern - YouTube
I'll see if I can track down a better video.

It's simple process that you could tweak as you go.
Basically, cut out a bunch of wooden donuts.
Slice the donuts into segments. Stack and offset the segments.
The good thing about this method is that you can easily trial different slopes to see what looks best.
You can alter the size of the segments at the top and bottom to smooth into the base and top.
Once complete, you could veneer it or use it as a mould.
Or use solid wood and leave the slices as a feature.

Great solution hiroller , amazing video.
It would sacrifice some strength but it looks
like it makes it a lot more easier to build.
Why is he knocking in that dowel at the 3 .00 minute point ?
Rob

I'm guessing that dowel is one of many used to lock multiple layers together for strength.

I don't reckon it is the same diam top and bottom. Top is wider. Bum! Now I will be mucking around with paper cut outs to.

The scaling is a bit off, but it sort of works. Supports itself. Bit of mucking about with sizes of course. And thickness of material.

draw spiral on double sheet.
helixtable 005s.jpg

Cut out like this
helixtable 006s.jpg

spin one around so half way around making circle in middle.
helixtable 007s.jpg

Move top most arms out to edge.
helixtable 008s.jpg

Bob's your uncle.
helixtable 009s.jpg

There is also this thread, https://www.woodworkforums.com/f12/sp...erator-180390/

Now I have a lot more to think about.

What an amazing amount of work in making that propeller. I understand the concept and I think I could use it. After a bit more thought.

Yes tea Lady I think you are correct. It looks wider at the top. Neat work with the paper. I am tempted to try it with a sheet of 3mm ply.

I am away for a few days and wont have any shed time but please keep your suggestions coming.
Slowly my brain should decide which way to go.

cheers

It difficult to determine from the picture but the helix looks like:
- Each arm traverse through 360 from base to top.
- The inner diameter at the base looks similar to the radial width of each arm
- The outer diameter at the base looks similar to the inner diameter at the top.
This means the total diameter at the top will be 2.5 times the inner diameter.
We can draw this accurately using the spiral generator app mentioned above ( Spiral Template Generator Tool - Print to Scale - Metric ) setting Rotations = 2.5.
This generates a spiral like this:Spiral2.5.png

A little tweaking in MS Paint gives us: Spiral2.5a.png

You can then use this as a pattern to cut out horizontal segments.
If the arms rise at 45 degrees from the base then each segment needs to slide around the circumference from the previous piece by the thickness of the wood.
The wider the angle of the segment, the thicker the helix arm will be.
SprialSlices.png
This can be glued, screwed, doweled, smoothed, veneered and made beautiful or used as a mould.
My 2c worth, I hope it comes across as I imagined.

This is a comment just so I'm in the loop to see what might eventuate