On Tuesday, January 22, 2019 at 12:54:08 PM UTC-5, wrote:
Gary, be specific on which AS design and serial number you need to fit. The US bottle diameter normally used for sailplane O2 systems increased a few years back and this created a SNAFU with some Schleicher designs. Research Yahoo's ASW-27 owners group as it has specifics. I'm probably wrong but perhaps Schleicher enlarged the cylinder well somewhere along in productions..

On Tuesday, January 22, 2019 at 11:48:01 AM UTC-5, OHM Ω http://aviation.derosaweb.net wrote:
Gary,

I assume by largest you mean diameter, not length. I am also assuming that you want to find/buy an O2 bottle to fit an ASW-27. You know what they say about assuming.

After I bought my ASW-27 I had to do some major league searching to find a bottle that would fit my ship. Took more than a year to find one. Luckily a friend that owns an ASW-24 lent me his bottle for a western trip. Thanks, Geoff.

Bottom line is that the critical dimension is the diameter (no duh) which, to me, is rather difficult to measure accurately unless you have a particularly large caliper hanging around. Accurate measuring is especially dicey when you are asking a seller of unknown resources/capabilities to measure their bottle.

So, using my friend's bottle, I came up with the following CIRCUMFERENCE which is much easier to measure accurately. This I could then give to prospective bottle providers for them to measure what they have in stock before purchasing.

Here is what I came up with;

Circumference = 13-5/32" = 13.15625" = 334.2mm
QED Diameter = 4-3/16" = 4.1875 = 106.4mm

So, how to have someone else easily accurately measure circumference? A carpenter's steel measuring tape will NOT wrap around a cylinder. A tailor's cloth tape is great but is much less likely have be available. The easiest way I found is to have the seller wrap a (long narrow) piece of paper around the bottle, mark where the edges meet, lay the paper out flat on a table, and then accurately measure between the marks with a simple flat ruler (preferably in metric as +/- 1mm is ok but counting 16ths of a inch is more prone to error - ask me how I know).

Be prepared to suffer multiple disappointments in your search.

My overblown $0.02,
John OHM Ω

PS - Asking the ASW-27 Yahoo group may dredge up something for you. https://groups.yahoo.com/neo/groups/ASW27owners
Or post to http://glidersource.com which is where I ultimately found my bottle.

My ASW27 is 27-148

Once I get the 3D printed bottle completed, I will reveal what the actual dimensions are for future owners, i.e perfect fit or room to grow... At least we will know the largest you are going to get in the hole...