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Registered Member #952
Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388
Any opinions or experience on using round cardboard containers as secondary formers? I know that it's slightly conductive and there would be heating problems but... Has anybody ever tried?
Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
I remember from hobby rocketry that there are different "cardboard" tubes. Some are spiral wound, others are parallel wound (a simple role of material continually glued together). The Parallel wound tube being much stronger and denser. That density may play a role.
I've been thinking about this also. I've heard that PVC is very "lossy" as opposed to other polymer material. However there are alternatives at low cost at hardware stores but the spiral wound cardboard tubes exist in such abundance in the sizes I would want to use.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Cardboard is fine. Just be careful about any cardboard with "writing" on it as this may be conductive, as well as "black" cardboard as it may be conductive. But regular brown cardboard is fine. Just coat prior with shellac or similar and wind.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Actually, cardboard is more temperature stable than common plastics like PVC, PE or acrylic, and if you dip it in epoxy resin it can also be very mechanically rigid.
What I think of as biggest problem is that you can never get as smooth surface with it like with plastics, which can be troubling if you are attempting to wind really thin (<0.15mm) wire.
Registered Member #1180
Joined: Mon Dec 17 2007, 12:26AM
Location: Nope
Posts: 28
yeah, why not? I've used nothing but carboard for my secondaries, granted the first one died (but that was due to racing arcs, not card board. Also I've never had any issues with my secondaries heating up. I also never bothered varnishing it before I wound my coil onto it. The only real draw back hat iI've found is that the tubes will warp if you do a real tight wind on it.
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Cardboard secondary former?
