plywood tube

[skeltz (Rob)]

Well if anyone is interested i have just completed my plywood tube and i am very happy with the outcome for pictures and commentary follow this link... http://www.pbase.com/skelty/elvista_observatory

CHEERS ALL

[Orion]

I certainly am interested, nice job.

Is the tube thickness 4.5 mm?

[little col]

looks lo=ike your well on the way to getting your scope assembled , looks very impressive

[gbeal]

Looks nice Rob. While I like the asthetics of ply, why not now think about a carbon fiber tube? Same sort of construction, but instead of 7 plus kilos, I would guess at about 3 max.

[skeltz (Rob)]

Thanks for the comments guys ,the tube is 5 mill thick and as for carbon fibre well there is a huge price difference huge!
And the titan will handle the weight anyway besides i love making things myself

[ballaratdragons (Ken)]

The clear coating should bring out the woodgrain beautifully.

Very nice job.

[skeltz (Rob)]

Okay i have gone to dream scopes site .and for a 13.25 OD and 12.375 ID and their tube is 78 millimeters shorter than mine.
theirs costs $1400.00.
And the weight is 5.11 kilo..bear in mind this is still not quite as large as mine so i am only 2.5 kilo or probally a bit less ,above a carbon fibre tube and nearly as strong .
and YES IT ONLY COST ME $200.00 to make
FOOD FOR THOUGHT

[avandonk]

Beautifully built! How does it compare to an equivalent Al tube for weight.

Bert

[skeltz (Rob)]

Originally Posted by avandonk

Beautifully built! How does it compare to an equivalent Al tube for weight.

Bert

Not sure bert out in my neck of the woods its hard to find anything and i dont know even where to get a Aluminium tube from.
cheers

[CoombellKid]

What an excellent result. Was the ply dry when you wrapped it over the mold?

or did you soak it? I have just brought some 3mm ply to do a simiar thing
except only using a single layer. for a secondary cage.

regards,CS

[gbeal]

Originally Posted by CoombellKid

What an excellent result. Was the ply dry when you wrapped it over the mold?

or did you soak it? I have just brought some 3mm to do a simiar thing
except only using a single layer. for a secondary cage.

regards,CS

Not sure what his answer will be, but if it helps, steam the ply that will make it less stiff. I often roll stuff up for ages prior to using it, and it already has a bend as a result.

[skeltz (Rob)]

I got my plywood from brims ply.
Being as each sheet is only 1.5 mm thick it bends easy as and there is no need at all to wet it.Its comes in interior or marine grade,i went for the marine grade.
It did however cost me about $57.00 a sheet.
YOU could make a 4 inch tube out of it easy as!!!
A great product what more can i say
ps i will restate that the sheets are 1.5 mm thick comprising of 3 x .5mm thick plys hence a sheet of ply that is 1.5 mm thick.
Once you laminate 3 ply sheets the strenght and rigidity is unbeliavably
cheers all ..rob

[avandonk]

Rob I did a quick calculation and a tube made out of Al 2mm thick and 378mm dia and 1500mm long would weigh 9.6kg. Al has a density of 2.70 g/cm3.
I dont know how thick Al has to be to get the rigidity of laminated plywood but I suspect it would have to be thicker than 2mm.

Bert

[CoombellKid]

Thanks guy's

I hadn't thought about using Al.

Rob, how are you going to cut the focuser hole in the plywood tube?
I intend to mark the required circle out and use a drill to drill a series
of holes...etc...etc... but I would like a clean edge so was thinking
of using one of those circular drill bits used for cutting holes in
whiteboard placed in a drill press and slowly worked through.

regards,CS

[ausastronomer (John Bambury)]

Cut it with a holesaw which has a 1/4" centering drill bit. Put several layers of masking tape on the back side of the plywood which will prevent "chipout". Use slow speed and very light pressure and a lot of patience and you will end up with two perfectly clean edges.

Nice looking tube BTW. You could have easily gone one step further and ripped your plywood tube down the middle and used it as a mould for a fibreglass or carbon fibre tube, but they just ain't as pretty as wood IMO.

CS-John B

[CoombellKid]

John,

Thats exactly what I had in mind, and I think will do a better job or at least
a cleaner job.

I'm still to build the shed/workarea yet lol, although all the wood arrived
today. So I'll be busy this week building that and a decent work bench.
It's a handy thing having a few mates that work or run sawmills. I got all
the timber to build the shed and work bench cut to size and delivered for
$60.

Yes that ply tube of Rob's above is very sexy.

regards,CS

[skeltz (Rob)]

Hi rob well im glad you asked how am i going to cut out the focuser hole?..well since its going to be a 3 inch jmi ngxtn focuser i was thinking ..... yes you guessed it ,,the.jigsaw will do nicely.
I mean even if the hole is perfectey round for whatever stuff ups its not really gonna matter as the plate of the jmi is large enought.
One more thing im just guessing but i suspect my tube is stronger and lighter than a aluminium of the same size.
As for the inside of the tube i will use flocking material in it so any mistakes... did i say that??? will be hidden i mean hey we all make mistakes!!

Originally Posted by CoombellKid

Thanks guy's

I hadn't thought about using Al.

Rob, how are you going to cut the focuser hole in the plywood tube?
I intend to mark the required circle out and use a drill to drill a series
of holes...etc...etc... but I would like a clean edge so was thinking
of using one of those circular drill bits used for cutting holes in
whiteboard placed in a drill press and slowly worked through.

regards,CS

[CoombellKid]

Rob,

Sounds great!, I am looking forward to seeing your scope finished.

I'm making a secondary cage that will be painted flat black inside. Haven't thought
about the possibility of using flocking paper as I'm looking at ways of keeping
the weight to a minumim. Since my first project is turning my 8" newt into
a truss Dob for my boy's to use. Secondary cage weight is a major problem
with a scope so small. The weight of the focuser and finder and an XW or
nagler...etc...etc makes a big component of the weight.

regards,CS

[CoombellKid]

btw, can anyone remind me how to work out the circumference of a circle
when you know the radius or diameter? I have seeed to have forgotten
how the formula goes.

Just thought I would ask in here, since the thread is about tubes

regards,CS

[Jupiter]

Circ = Pi x Diameter, where Pi = 3.14