Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
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I've had the following mandrel materials suggested :
- a rolled aluminium tube (made from a thin (0.7mm) sheet) ... needs a releasing agent to get the tube off when finished.
- a smooth surface formica tube .... needs a releasing agent ?
- a fornatube / sonotube or cellulose tube .... needs a releasing agent
- polycarbonate 1.5mm thick sheet formed into a tube ... needs a releasing agent
- polypropylene sheet formed into a tube ....I've discovered by googling that acrylic will not bond to polypropylene.
What's the recommendation on mandrel material and releasing agent ?
I've had it suggested that GladWrap wrapped around the mandrel is OK as releasing agent .... anyone tried it ?
p
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scopemankit
super member
Reged: 01/27/09
Posts: 137
Loc: south africa
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Non-stick baking paper laid and taped on your mandrel is an excellent release medium.
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Chris
Cape Town
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jasonharris
sage
Reged: 09/16/06
Posts: 248
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I dont think peel ply,m the stuff they normall use is too expensive. I do know that glad wrap has been used before with success.
I wonder how well sonotube would work as a form given it's not a smooth surface where the joins are around the winding. I think it would be hard to take the CF off as it would fill in those areas.
If it is a big tube and it's your first time I would suggest something that you can collapse if you find it wont come off, eg formica wrapped around discs, or aluminium.
Jason
Edited by jasonharris (10/10/09 04:50 AM)
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
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Quote:
I dont think peel ply,m the stuff they normall use is too expensive. I do know that glad wrap has been used before with success.
I wonder how well sonotube would work as a form given it's not a smooth surface where the joins are around the winding. I think it would be hard to take the CF off as it would fill in those areas.
If it is a big tube and it's your first time I would suggest something that you can collapse if you find it wont come off, eg formica wrapped around discs, or aluminium.
Jason
That's my thoughts too, ie a collapseable mandrel, just a matter of deciding what to used (the cheapest material that will bend but be strong enough to build up the tube by hand.
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Gene Hunter
sage
Reged: 12/29/07
Posts: 288
Loc: SC
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I believe parchment paper is the material the gentleman above was referring too and it is the best material I have come across anywhere. CF and expoxy do not stick to it at all, however you need some amount of stickyness (technical term) in order for the CF and epoxy to stay put.
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Clear Skies
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
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Looking at costing me 150AUD to buy a 316mm OD x 3m formatube (Australian equiv to sonotube) if I have get it shipped from Melbourne or Brisbane (no warehouse in Sydney or Newcastle as far as I know).
And 316mm OD for my mandrel is bigger than I wanted , was hoping for 305-310mm OD on the mandrel , so my secondary and secondary-focusor distances remain close to optimal.
Formatube would have been easier, I'd simply cut it to my desired length, wrap some thin polypropylene sheet around it (to eliminate bumps and provide easy release). But if I go make my CF tube bigger than the existing 316mm OD , I will need to get new tube clamp bolts (longer).
Not a big issue
I called around by phone this afternoon and can get a 2.4m x 1.2m x 0.8mm sheet of 5005 grade aluminium for 69 AUD , and a local sheet place quoted 1 hour or work and 60 AUD to cut the sheet and roll it to produce 310mm OD x 1.5m long tube.
This is cheaper than getting a 316mm OD formatube unless I can get one locally (avoiding shipping costs).
Task for next week , source Formatube locally and if available locally buy a tube and have it cut to length to go into the pajero , and then order my carbon fibre cloth from China (too expensive buying locally, from Ebay or from UK or USA hobbyist suppliers).
If I decide to scrub the carbon fibre tube for now, and do a aluminium tube , it'll cost me the same to produce a 1.27m long tube of 310-312mm OD.
If I can't get a formatube locally , I'll get a aluminium tube rolled from a sheet either as my mandrel , or perhaps to use as my OTA tube.
Decisions .... decisions ....
Edited by Ian Robinson (10/16/09 08:46 AM)
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
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Quote:
Non-stick baking paper laid and taped on your mandrel is an excellent release medium.
Dirt cheap too .
Anyone used it in the carbon fibre fabrications ?
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scopemankit
super member
Reged: 01/27/09
Posts: 137
Loc: south africa
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Yes, For the tube abd the baffle/secondary holder of my superstrut scope.
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Chris
Cape Town
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sailor70623
scholastic sledgehammer
Reged: 01/12/08
Posts: 944
Loc: Ok.
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I haven't made a scope tube, but have made masts. I use styrofoam for my mandrel, then just disolve it out with solvent.
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Corornado PST
LB 16" & 12"
Z 10"
LX50 8"
8" CPC
ETX127
102&90mm MAKs
80mm Richfield APO
70mm refractor
ETX60
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
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Quote:
I haven't made a scope tube, but have made masts. I use styrofoam for my mandrel, then just disolve it out with solvent.
Interesting idea.
Do you form the mandrel by making some kind of mould first and then adding the styrofoam as a foamy liquid , and then allow the foam to harden , or do buy the styrofoam already hardened and then shape it with powertools to suit ?
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sailor70623
scholastic sledgehammer
Reged: 01/12/08
Posts: 944
Loc: Ok.
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I use 3/4" sheets of styrofoam, cut it in strips and glue it into a rough shape just a touch larger than I want the finished mandrel. This also allows me to thin the mandrel where I want the material to be thicker. On a mast this is at he goose neck and spreaders, on a scope this may be where the scope will be mounted and where your cell will attach, etc. Sand it down to size, actually just a tad under size, and coat with spackle, sand again for a smooth surface. Then just wrap the mandrel with the fiberglas and epoxy. I use shrink wrap around the project when I'm done wrapping with glass. I don't have a vacume pump, but the shrink wrap works fine. It's like a heavy duty seran wrap. Do use the slowest epoxy you can find. The epoxy I got for mast making takes 12 hours to kick.
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Corornado PST
LB 16" & 12"
Z 10"
LX50 8"
8" CPC
ETX127
102&90mm MAKs
80mm Richfield APO
70mm refractor
ETX60
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
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Quote:
I use 3/4" sheets of styrofoam, cut it in strips and glue it into a rough shape just a touch larger than I want the finished mandrel. This also allows me to thin the mandrel where I want the material to be thicker. On a mast this is at he goose neck and spreaders, on a scope this may be where the scope will be mounted and where your cell will attach, etc. Sand it down to size, actually just a tad under size, and coat with spackle, sand again for a smooth surface. Then just wrap the mandrel with the fiberglas and epoxy. I use shrink wrap around the project when I'm done wrapping with glass. I don't have a vacume pump, but the shrink wrap works fine. It's like a heavy duty seran wrap. Do use the slowest epoxy you can find. The epoxy I got for mast making takes 12 hours to kick.
This the kind of spackle you use http://www.selleys.com.au/Selleys-Spakfilla-Rapid/default.aspx , or do you buy in powder form and mix with water and then apply like a plasteror does gapfilling ?
What do you use to glue the styrofoam sheets together ?
What solvent do use to get rid of the styofoam mandrel form ?
Shrinkwrapping the first layer of fibre cloth and epoxy will conpress the styrofoam mandrel , make the cylinder take on a hyperbolic or parabolic tube shape (I think), 3/4" styrofoam board is not very strong,so unless the mandrel styrofoam mandrel form is reinforced somehow.
How ofter do you place reinforcings (in my case disks) inside the styrofoam mandrel form ?
Edited by Ian Robinson (10/18/09 01:23 AM)
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sailor70623
scholastic sledgehammer
Reged: 01/12/08
Posts: 944
Loc: Ok.
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I use what ever glue is around, usually Elmers. Same with the spackle, mostly left over from when I re-walled a few rooms in the house. Comes in a 5 gallon bucket, premixed. For small spars, I use pb rust buster, styrofoam melts real fast with this stuff. You don't need to melt it all, just around the edges. I guess if you pull the shrink wrap tight enough you could deform the plug, but this isn't the shrink wrap like you use on wires, it's like the plastic wrap you wrap left overs with. I don't know where you buy it, but it's always available at most shipping docks. I lay up at least 3 layers, and some times 4 before I wrap it. Like I said, get the slowest curring epoxy you can find. Lots of good information can be found on the boat building sites about both working with fiberglass, and making masts and spars. As well as using Kevlar and or carbon fiber instead of, or with fiber glass.
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Corornado PST
LB 16" & 12"
Z 10"
LX50 8"
8" CPC
ETX127
102&90mm MAKs
80mm Richfield APO
70mm refractor
ETX60
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