Plywood Woes!

[Darkplague]

Hi,

I am currently building a 16" truss dob, but am struggling to find a source for good quality hardwood plywood. It seems almost impossible to get unless you import it from the states.

The best I can get is a Hoop plywood, which supposedly is the strongest of the "softwood" plywoods.

Does anyone know of a good source to buy hard plywood from, preferably in Adelaide?

Thanks,

Mark

[[1ponders]]

What thickness ply Mark? Would marine or formwork ply be suitable?

[Darkplague]

Formwork ply is no good as it has a plastic coating on 1 side.

Marine ply is made from the same soft ply as normal plywood. The only difference is that it uses a special waterproof glue that is expensive.

The size I need is 5/8" ,16mm or even 19mm, doesnt really matter.

My David Kreige book says to steer clear of these types of plywoods and go for the hardwood plywood, like apple ply or maple/birch plywood.

[rochler]

already tried? Have you rung around, or just gone to the local hardware etc. I would try the 'specialist' timber places like Footersville - if they haven't got it stock they can probably order it in... :confuse3:

[Orion]

I went to Mister Ply&Wood and made mine out of furniture ply I think they called it Ivorywood. It has some viods not many but if you come across them just fill them up with putty.

The telescope is rock solid and as long as the plywood is reasonable quality the outcome will all depend on the design of the telescope.

[Darkplague]

No mr.plywood in Adelaide. :(
Ive rang just about eryone in the yellow pages in Adelaide.

I guess I will have to make do with ordinary plywood.
The hardwood comes up looking beautiful as well as being stronger.
This is why I want the hardwood kind. The normal plywood kinda looks cheap and nasty when built imo.

[Orion]

Mark that's alright just get the best ply you can and stain it that is what I did.

It also comes down to design as I said before if need be laminate two or three pieces of ply together for strength.

Good luck.

[ausastronomer]

Mark,

Although they are softwood plys, Hoop Ply and Marine Ply both do an excellent job, what do you intend to do, build a telescope or drive the car on it ? I know Andrew Murrell's 20" Hector is built from Hoop Ply and he is 15 years old and still going strong. When Gary Kopff set up the Argo Navis Pointing Analysis software on it a few months back, the summed pointing errors were less than 20', which aint bad for a 15 year old telescope built from softwood plywood :)

The main thing is to stay away from home improvement stores/centres and go to a specialist supplier of sheet timbers. Any high grade plywood suitable for exterior use will be good. As Ed says we have Mr Ply & Wood and Plywood Express in NSW which are both specialist suppliers. Any store like this will have a material thats suitable.

CS-John B

[Darkplague]

You wouldnt happen to have some photos of your scope you built, Im interested to see how yours turned out?

[Orion]

No problem here is one...

[acropolite]

FWIW Hoop pine is used in homebuilt aircraft due to it's good structural properties.

[Satchmo]

I've always used Hoop pine for my Dobs. Its the most expensive ply available from Mister Plywood. They only charge $20 to cut it up too, with no maximum cuts so long as they can run a peice straight through the saw.

Mark

[rmcpb]

I would imagine that the softwood plys we get here are plenty strong enough for a dob. They may not look as nice as the apple ply, etc, available in the States but if that is a concern then a veneer job would be really easy.

[Astroman]

Also using the hoop ply etc..you can always use a clear enamel or stain to make it look more expensive :)

I had a look a while ago at plywood, for a new dob, but financial constraints prevented me from going further.

Look forward to hearing more about your progress.

[ausastronomer]

Mark,

Here are a couple of places to try for starters. I did a search on the yellow pages in Adelaide under "Plywoods and Veneers" :-

Brown Wood Panels Pty Ltd
107 Mooringe Ave Camden Park SA 5038
ph: (08) 8294 3877 Plywoods & Veneers

Designer Veneers Ltd
Unit 3-4/ 7 Ween Rd Pooraka SA 5095
ph: (08) 8359 1088 Plywoods & Veneers

Le Messurier Timber Co Pty Ltd
346 Port Rd Port Adelaide SA 5015
ph: (08) 8447 0440 Plywoods & Veneers

Opal Wood Corporation Pty Ltd
19 Wilson St Royal Park SA 5014
ph: (08) 8241 0313 Plywoods & Veneers

Otto & Co Pty Ltd
5 Ann St Stepney SA 5069
ph: (08) 8362 3522 Plywoods & Veneers

I am not sure how these are situated geographically for you or what they carry but give them a call.

FWIW, the Ivorywood Plywood that ED (Orion) used, is in fact a South American hardwood plywood, with a marine grade glue. It would be perfect for the job. Its also reasonably cheap at about $90 for an 8' x 4' sheet of 15mm. Here is some info on it:-

http://www.argentinefinehardwoods.com/gallery_medium.htm

and here is a grain picture:-

http://www.argentinefinehardwoods.com/productDetails/prod_ivory_wood.htm

Plywood Express advised me they could supply all the "fancy" hardwood plywoods with the exotic finishes (whatever hardwood you like actually), except it was extremely expensive, in excess of $350 per 8' x 4' sheet as a base price and it went up from there.

CS-John B

[davidpretorius]

i have seen this before in photos, but i never stopped getting excited when i see it again,

that is the nicest looking telescope I have seen

[Orion]

Thanks,;)
It took me 2 years to build (on and off) and actually I'm still going with it the latest is a anti dew system that Warren (Wazza) built for me.

[davidpretorius]

i plan to get to one of the northern camps and have a look in the flesh!

[Orion]

Thanks for the info John I forgot to mention the ply was South American hardwood.

[Orion]

Thanks Dave I'll look forward to seeing you.

[Darkplague]

Thanks for all the advice everyone,its been very helpful! Ive decided to go with the hoop pine for my dob.

Orion, that is one beauty of a scope! I hope mine turns out even half as good.

One other thing I cant find is a suitable plastic for the secondary cage. The Kreig book says you need to find "kydex" plastic, but I have yet to find anything even close here in Oz. Actually , I have found a plastic that can be wrapped a round the secondary, but it only comes in clear. :(

The usual places like Bunnings, mitre10 and such dont have anything like this.
Time to look in the yellow pages.............................. .

[Orion]

Mark instead of Kydex use Formica.
Kydex shrinks and expands dew to temperature changes Formica doesn't.
I've heard some horror stories about Kydex pulling away from the rings.

The latest is that people are having to use brass brads every couple of inches to secure it back on.

[Darkplague]

What is formica exactly? Sounds like a kind of wood!

Apparrantely you are supposed to put the kydex in the feezer before you install it, that way when it heats up and expands, it forms a tight bond inside the 2 cage rings. If you install the kydex on a hot day, you will get these shrinkage problems where it will pull apart from the rings.

I like your light shroud too, it looks very neat, is it a homemade job or bought one?

[ausastronomer]

Formica is a large multinational company who developed the product "laminex". Which is now a commonplace product used in most domestic kitchen refits. The term formica has become a generic name for all benchtop laminate materials. Several companies make these laminates including Formica, Wilson Arts, Duropal and several others. They are all good and of similar quality.

http://www.formica.com/publish/site/na.html

http://www.wilsonart.com/

http://www.duropal.com.au/

The best way to buy these products is from a kitchen refit company. You probably need to buy some "Ebony Star" laminate which is a Wilson Art laminate for the bottom of the rocker box for smooth azimuth motion and it is a decorative product also suitable for using on the upper cage assembly (UCA). Hence there would be some economies in using ebony star for both the rocker box and UCA.

CS-John B

[Darkplague]

Omg!

I didnt even think to use that.
I have just recently bought a big roll of Ebony star, and should have heaps left over to use for the secondary cage. Just need to paint the inside flat black.
The Formica rolls up nicely too!

I owe you one Ausastronomer!!!!!!!! :prey2:


One last question: For the side bearings , I have found a pair of metal rings at work, about 23" diameter. Do you think the formica will stick to the curved steel surface well, or does the steel need to be "roughed up" first?

Where did you (Orion) source your bearings from?

[RAJAH235]

A 'keyed' surface is always better than a smooth one..... Just give it a 'good going over' with a 'B--t-rd' file, on edge if nec. :D L.
ps. Wow, the ref called time on that word too....
pps. Was legit too. Smooth, 2nd cut n bas---d. Coarseness of files.???

[Darkplague]

Heh, I know what you mean, I have a few of them in my toolbox.
Damn those Basterd files..............

[Darkplague]

I'm really looking forward to this project now. To build the scope is more exciting than using it!!!!! Will post progress pictures very soon. Unfortunately I have to move house in 2 weeks so everything is postponed till then. But after it's all systems go!!!

One thing about staining+ sealing the plywood. I spoke to a salesperson at a timber yard and he said put the sealer on first, and then stain the wood last. This to me seems backward. I thought you would stain the wood first, and then seal it?????

Any takers?

[greeps]

1. The plywood you want is called Baltic Birch, here in the states, anyway. I get it from suppliers that supply cabinet makers. It has many thin plies. It comes in 5X5 foot sheets, not the classic 4X8' sheets.
2. The sealer is really a presealer. It penetrates the wood and limits the depth to which the stain penetrates. You've stained softwood in the past and seen that the end grain stains much much darker. Sealer will prevent that. Sealing the wood also makes the softwood stain much more evenly. The stuff is very thin, it's like painting with mineral spirits. If you use it once, you'll be hooked. It really is worth the trouble, especially with the darker stains.
3. After the stain you'll need to protect the wood with a finish, polyurethane is probably the best. I use oil based polyurethane (not the water based) and I thin it 50/50 with mineral spirits. This I rub on with a cloth. It'll take more coats but you don't need to worry about runs or uneven coating and it makes application much easier. I drop the cloth into the can between coats. It'll give you a nicer job.

Good luck.

[Vermin]

Sealer can be made by mixing varnish 50/50 with thinners.

[ausastronomer]

For anyone thats interested I have found a source for Baltic Birch Plywood in Sydney. I haven't seen it, only spoken to the guy on the phone. From what he describes it is the stuff we need, multiple thin even laminations and each layer is birch. He advised my that it is an A-Bond glue which is waterproof and that which is used for marine ply. He also advised me that both faces were "B" grade finish which gives a good finished product with minimal sanding. The finishes are graded from A to D and cheaper plywoods have a lower quality finish on 1 side compared to the other.

The only thing that has me a little sceptical as to whether or not it is the right stuff is the price:-

$63 for a 2400 x 1200 sheet of 9mm and $72 for a sheet of 2400 x 1200 sheet of 12mm. If it is good quality stuff thats an absolute bargain.

The place is at Brookvale in Sydney and I hope to get down and have a look at it within the next couple of weeks, as I am in the planning stages of building a 10"/F5 truss scope for myself and a 14"/f6 truss scope for Andrew Murrell.

When I ascertain 1st hand that it's good quality stuff and suitable for scope building, I will let you all know where it is.

CS-John B

[cristian abarca]

You will need 19mm as well. I got 19mm marine ply about 6 monts ago from a friend who is a stair manufacturer an the marine ply 19mm at his trade price cost about $90 a sheet. The prices you got seem very reasonable. I'm building my truss scope from ordinary plywood, but I'm painting mine. From using the marine ply and the cheap stuff I can tell you there is a big difference in quality, specially if you are staining and varnishing it. The cheap stuff is full of holes and sometimes pieces come of the edge as you cut it.

Regards Cristian

[ausastronomer]

Thanks Christian.

With a sheet of 9mm and 12mm I can also get to 18mm, 21mm and 24mm thicknesses by laminating the pieces together in various combinations as per Kriege and Berry's book. Saves buying the extra sheet and works just as well. The important thing is to make sure you use the right glue and clamp it properly when you laminate.

CS-John B

[cristian abarca]

I did that to make the side bearings but because I found the plywood at work I only had 19mm and 9 mm so my options were limited. I did end up using more of the 19mm because of the weight needed to balace the scope. I'm converting a 10 inch F7.3 so I had to play around a bit with the box to get the torque equations close. As in Berrys book. My mirror, mirror cell and box were not enough to balance the telescope so I had to use two layers of 19mm plywood. Berrys examples only start at 15 or 16 inch mirrors. The weight of the secondary cage also made my job a little more challenging. I managed to get it down to 2.5 kilos which is not bad considering I didn't ose Kydex plastic. I'll post some pictures of the project soon. It's nearly finished just the the secondary pole connectors to go, align the primary box pole holders, put it together and cross my fingers that I did the maths correctly and the thing balances.

Regards Cristian

[Roger Davis]

For those in Melbourne the company is called PLYCO they are situated in Alphington. They do laser cutting as well, but not curves!

[Darkplague]

I bought hoop pine plywood. Its an A-B grade and looks wonderful on both sides. A 19mm sheet and 15mm sheet cost me $235!

A good tip on laminating I learned from the Kriege book is to glue the 2 sheets together and stick them under your car wheel overnight using a jack. Should give you more than enough clamping force me thinks!!!

[greycat]

Hi there!

ausastronomer - I was wondering about the source you found for Baltic Birch Plywood in Brookvale. I'm need to find 1mm "aircraft ply" urgently, and I believe it is birch ply. I've found a few suppliers interstate, but no luck in Sydney so far. I'll call Bruynzeel and Caporns first thing tomorrow... If it was a different place you found, please let me know!

Many thanks, Carolyn.

[Wavytone]

The baltic birch plys are made in several grades as well and the real "aircraft grade" stuff is made to stringent standards such as no knots, and it bears certification stamps on each sheet so that builders of homebrew light planes have some assurance the stuff isn't going the break up in the air.

The grades that are just sold as Baltic birch ply without the "aircraft" moniker (and no certification) are far cheaper, which possibly explains the prices previously.

On an aside, I've also found another interesting material - laminated bamboo sheets that come 5.5mm thick. This stuff is quite light and incredibly strong along the grain. There is a crowd at www.ponoko.com (http://www.ponoko.com) that can supply modestly size pieces and laser-cut it fairly reasonably. The laser cutting is very accurate, having seen an example first-hand. For screws or nails you'll have to have laser-cut holes made or drill it as it will split easily without a hole.

And yes I'm interested in a source of the 1mm birch ply too, I have several things I need to make with it.

[ngcles]

Hi Mark & All,

Like many others who have commented, my 18" is also hoop pine with five coats of carefully applied poly and over 6 years I haven't had a problem at all. There were some voids in it which putty-up well and it sanded down fine. One of the sheets was a bit ordinary finish-wise on one side. It went on the inside -- what's the problem if it's painted black or coated with black velvet?

I guess it comes down to whether you want to look "at" the telescope, or look "through" the telescope. I'm from the latter philosophy, though I can see why some people get carried away by the way it can look too. Mine isn't "rough" by any standard though -- just not furniture grade. In the dark, do one can tell what sort of plywood you used.

Try some of the small kitchen businesses for the laminate as some have already suggested. Ebony star is a bit on the dear side (okay, it is quite expensive) but does work very, very well. If you get in with the kitchen guys, they might even help out with some of the routing, cutting laminating and even nailing (fixing) together (mine is nailed) after you have marked it out. A good strong finish achieved very quickly.

Many of them are also well set-up to do spray poly and can do it reasonably cheaply. A few cartons of beer at the right time might be a good investment, if you can find the right kitchen people ...


Best,


Les D

[Doomsayer]

I (& firends of mine) have also used hoop ply to build a number of scopes over the years. However, I used gaboon mahogony marine ply from Mr Ply & Wood to build my 20" dob a few years ago, following the Kriege methods. This gaboon ply is hardwood veneer and cored, and is less dense and seems far stiffer than hoop. It comes up a lot better than hoop with a tan or tobacco hue with just coats of varnish or estapol and no stain. As of early last year, gaboon was still available but on back order. The other variety of marine ply at Mr P&W then was the more standard coachwood variety.

The only other sources of hardwood core/hardwood veneer ply at that time were the birch suggested elsewhere here, and a local manufacturer of exotic ply based on Australian hardwoods - I think it might have been Big River Timber.

guy

[tnott]

I used Pacific Birch Ply for the 16" TriDob and Gaboon for the 10" and the current 22". Both good, but the Gaboon is more attractive to finish and about 20% lighter. Both from Duck Flat Wooden Boats in Mt. Barker SA.

[stephenb]

For what it's worth, I used A-A Grade Hoop Pine from Construction Plywoods in Airport West, Victoria. It was approximately $200 for a 2400x1200 sheet. The outer ply layers are perfect and it does the job as far as I'm concerned.

[tnott]

Forgot to say - both Pacific Birch and Gaboon are hardwood core, hardwood veneer. This is more important the larger the scope, when you need to overcome the exponentially increasing weight and flexure problems. If you double the aperture you have the potential for 32X the flexure, so careful design and selection of materials is more important.