Thread: Yr 12 project - need help please....

Quite a project there mate. For my year 12 project I just made a knife

I'd make a series of circular frames - one for the opening, one for the widest point of the bubble, and a flat one to clamp to at the rear. More in between these ones also. Working out the taper that with have to be on the timber - both longitudinally and laterally - will be a fun task. I would use over thickness wood so that if your joints aren't perfect you can smooth the whole thing down with a handplane or sander and then fill any gaps with some sort of filler. If you plan to paint it then these fillers can be hidden well away.
Use the sort of glue you would use to stick your in-laws to a rocket with... I mean, err... Two part epoxy - holds incredibly well, and I'd want to use it to be sure that it wont spring apart.

On the school side of things, buy yourself a digital camera and take pictures and notes of absolutely everything you do, no matter how insignificant - whether it's a glue test or just working out how to sharpen a hand plane or tune the biscuit joint cutter - it does wonders for the marks on your book work. The moderators in SA seem more interested in the stuff in your R+D folder than the piece itself - almost ironic for a practical based subject.

This looks to be a good WIP for the forums a bit later All the best with it and hope you do well.

Cheers, Tom.

all i'd like to say is good luck! on my coffee table with the curved solid timber ends it took a hell of a long time to get them near perfectly smooth. i would suggest mdf and veneer!!!!!!!!!!! i cant wait to see the wip though it will be fantastic. if you're getting it lacqured or something of the sort using bog and sanding it flat will still show slight join marks so be careful. good luck my friend. spencer.

It's a big job, would be interesting, and poses a few problems just because of the size. There are probably more ways than one to skin a cat, but here's how I'd start.
First, I'd forget about making it a perfect sphere. If you make it a perfect sphere you'll have to make lots of lunes and they'll need to be thick enough to round the 'corners'.
First you'll have to make up a set of 'lunes'. Think of these as shapes like the surfaces between meridians on a globe of the world. The more you make and the narrower they are, the closer it will be to a true sphere. They don't have to be a full semi-circle, because of the hole you sit in, but they need to be bigger than the finished size. Laminate them using epoxy as Durge says, and don't forget to allow for spring-back. Then you have to trim the sides to final size. I'd make up a jig to do this using a bandsaw with a tilting table. Trim them just over size, then plane to finished size. This should help you get the bevel angle correct.
Gluing up will be fun, as epoxy is a great lubricant when it's wet. You could either do a couple at a time first, then finally glue the lot together. You'll probably need a clamping jig to do a few at a time. Tape them together with masking tape as you glue them, then finally put them in the jig. When you finally glue the lot together, again use masking tape, then hold them together using an inner tube cut into long strips. Wrap it around, stretching it a little as you go.
Before you glue the lot together, do at least one dry run, both to make sure they fit, and to make sure you have the routine down pat and have all the equipment. You don't want to have to mix up another batch of glue or run to Bunnings for more tape while your glue goes off.

There may be other ways to do it, you'll need lots of clamps, and lots of planning. Good luck - one thing's for sure, it will take longer to make than this took to write.

wow, well i did think about making an ornamental set of knives for mine out of solid peices of spotted gum to get the nice patterns. but then i figured i could actually use this chair (and its way cooler, partly because my teacher tried to make one and failed, and they dont think i can make one).
and i like that idea of having a couple of frames in between the peices sloping toward the back. the epoxy is also good idea, but i dont plan to paint it, i want a clear finish or light stain on the outside so the grain of the timber and joins arent hidden.
and i will makes sure that i take pics of everything i do...seems kinda strange they have more interest in your folio than the actual project :P

thanx durdge

haha thanx
i do have a year and a bit on this project, i hope it will be enough.
ill make sure to post the pictures when its done too.....but they wont be up till the end of 2012, when i finish yr 12

cheers spencer

well i hoped to make it a perfect sphere, but ill take your advice that i wont be able to (it'll be very close tho).
and i was going to get all the lengths of timber for the 'lunes' and steam bend them to the correct curve, then cut the sides to the right bevel.
and thanks for the gluing ideas....i had to do a similar thing on a previous project by gluing parts together then all of them for the finished peice.
haha it sure will take a long time but im hoping it will be worth it.

any more advice would be greatly appreciated if thought of thanx alex ill keep you posted over the next few years :P

I strongly suspect that the original chair is made from a plastic or fibreglass for a very good reason. It seems to me that not only are you having to cut the pieces into the segments of an orange to use an analogy, but also curve the pieces along both axis.

I may well be wrong as well but I think that in wood there will be serious strength issues with this design as the profile does not appear to be truly round or egg shaped. It seems hard to escape the probability that there will be a need for some amount of reinforcing material inside the seat. If not a perfect sphere, there will be points within the circumference that are inherently weaker than the others.

Another word of caution. If you spend months on this project only to find that it is unworkable in wood, what then? Surely the idea is to submit a finished, functional item rather than just document the process you went through to discover the task you set yourself was impossible?

It might well be wise to have a back up project running in tandem so that you can actually submit something at the end of the assessment period. If it is not needed, then you have gained a second piece to use, display, sell whatever the case may be.

I wish you all the luck in the world with this, a little risk assessment is all I am suggesting. This is an extremely ambitious project to pin all your Year 12 progress upon. If the teacher has tried making this item and failed, think through the reasons why that might be and can I realistically overcome these issues? What are the costs financially and in time to resolve these issues. Can I afford the cost? If someone else is underwriting the cost, what is the outcome of the balancing act between their expense against chance of success?

If I was your assessor or teacher, I think I would be advising very strongly against this, if not outright telling you no, you cannot make this for your Y12 assessment.

I strongly suspect that the original chair is made from a plastic or fibreglass for a very good reason.

Because if you make it out of epoxied/laminated timber it will be very, very heavy?

Definitely a project that needs a very thorough plan.

Not a bad post for a rainy afternoon....got me thinking, that's for sure. I'd like to see a timber ball chair....don't let us put you off making one.


And as an after-thought, your future use of the piece, good idea.....umm...how wide is it?
I Googled "ball chair dimensions", 32" wide...800mm "fits through most doors" so they say.
When I were a lad, I moved about a fair bit.....my chairs were stackable, both my bed and table broke down flat....worth considering.

I'm thinking along the lines of Alex's thoughts too. A while ago I had to look into making parachute-like structures and assembled all the maths to calculate the gore shape (what Alex calls lunes). You just need to make one template and you can produce all the gores from that. You would truncate the gores so that rather than meeting at a point, it leaves a circular hole which is filled with a circular section. The maths is very easy, making one template is very easy and making the gores is very easy. Putting it together is the challenging part. Knowing nothing about it apart from the name, I would think that the boat building method of 'stitch and glue' would be very useful. I would use bendy ply and make the gores small so it approached a sphere. This way, if you think it's not strong enough, you could calculate another set of gores slightly larger and glue them over the other shell with the joints offset. I reckon it's quite doable and a friendly boat builder may be able to assist with those boaty elements of construction.

Had another thought, since the inside will be upholstered I'm guessing, you could fibreglass the inside to add strength

Cheers
Michael

Originally Posted by superstudent

I am a student in year 10 and i need help on my major project in year 12 that i plan to make.

this project will be an "eero-aarnio ball chair" made out of wood....im not sure how i should bend the wood, whether by steaming then clamping, or by a completely different method.

i plan to orientate the wood so that the grain is running from the opening of the chair towards the back of the chair so that it will be easier to bend the wood unless there are any other suggestions?

this chair will have all the angled peices of wood biscuited together.

if there are any other things i didnt cover or make clear please tell me.

thanx superstudent

well that's not how I'd approach this project

First I'd make a solid (hollow) mold of the shape using MDF (if you have adequate dust extraction for the shaping tools) or timber if you don't. The mold will need to be in a few pieces so you can take it apart through the seat hole
shape the mold using something like an arbortech cutter and RAS sander

once the mold is complete, cover it with packaging tape or other glue resistant material.
use many layers of veneer strips to make the shell -- my guess is you will need more than 30 layers of veneer
only the first and last 2 or 3 layers need to have perfect joints, the inner ones can have small (1 to 2mm) gaps between the strips

As I said, there are probably many ways to skin a cat.
Also, as Mic-d says, gores and lunes are the same thing. Both are correct, but choose one or the other in your project documentation and stick to it. If you use bendy ply to laminate them, bending will probably be easier, but IIRC, it bends easiest across the outside grain. This may or may not be what you want.
When you laminate them, you may be able to do a lamination wide enough to cut several lunes from. To cut them to size and shape, you will probably need to make up a jig. The way I'd approach it is to cut them on a large bandsaw - the diameter of your chair will be governed by the height of the bandsaw. I'd look at a jig that can hold the lune at the correct angle.
I'll try to knock up a sketch of what I mean.

What Mic-d said about the boat builder. They are working with bends all the time.

I'd reckon boatbuilding methods too. Thin multiple laminations will give the strength without too much weight.
It's been done before - look at the mosquito fighter/bomber in WWII.
Good luck at beating the teacher. Great attitude.
Cheers,
Jim

Just for the record, in these sort of Technology and Design subjects, the process of designing the object and the documentation IS worth as much as the finished item. If the course is being delivered properly there is a huge amount of design consideration information that is imparted onto the students. (And before anyone asks I am a T&D teacher)

As for the chair - I wish you all the best of luck! If you can get it done it will be well worth it.

Have a think about why you want to make this out of wood. This is an easy and (relatively) inexpensive thing to make out of fibreglass and you are pretty much guaranteed a strong lightweight product with a good finish. However its an extremely difficult to make out of wood. In fact I'd say near-impossible to do and still get a quality look. And then there are issues of strength and weight and practicality which further call into question your logic in choosing the materials.

I really dont know what criteria T&D is marked on but if I had a student who bypassed the obvious way to make something and turned in a less successful example made in a difficult and expensive manner then I wouldnt be giving them a high mark. Isnt selection of the best method and materials for the job a criteria in this subject -especially when it is an already well established design.

Also, look at the cost of the wood/plywood you'll need as I expect you're on a limited budget. If you go the veneer route as suggested, ring and get a price on that but make sure you're sitting down first.

sorry to be a grinch, but someone needs to say it.
Arron