[markkyle]

Hello,

I just purchased two 15 gallon US Plastics induction tanks and intend to make a pair of conical fermenters out of them.  I've found some great ideas on line for sealing the lid and building the dump valve at the bottom.  I am looking for some advice as to how far from the bottom of the tank do I drill for a racking arm and how far should I drill for a thermowell?  If anybody out there has built their own I would love to hear any advice you may have.  Thanks!

[Stevie]

I have not done this, but I would recommend placing the thermowell in the lid as it will eliminate one potential leak point.

Good luck on your build, I'm sure a handful of the folks here have built or seen one in operation.

Edit - Brewers hardware make very nice thermowells in many lengths.
http://www.brewershardware.com/Straight-Wall-Thermowells/

[Thirsty_Monk]

Your temp probe could be just taped to the side wall and then insulated. If you insist on thermowell put it on straight part of the cylinder. Lower is better.

Racking port. Pour about 2 quarts into the fermenter and mark the water level. This is your low spot of opening for your racking port.

You should have NPT thread on the bottom of the fermenter.

I never had a problem with lid not sealing air tight but some people were putting manway gaskets on the top cover.

Good luck.

[JT]

I have a thermowell inserted through the top.  Unsurprisingly, it read the same as a fermometer taped to the side.  You're going to get accurate temps either way, as long as the thermowell is submersed in the beer. 
Taping to the side is just as effective.  When I do this I use a can koozie to cover the outside to insulate the probe.