Placement of Spark Gap

[frocksie]

I am thinking about making a hybrid in the near future, and I have a question on the safest place to put the spark gap.

The chamber will likely be 2"x12", and I am wondering whether I should put a hole in the chamber wall, tap it, and then put in a homemade sparkplug, or whether I should put a tee in front of the chamber, and put the sparkplug in that.

Thanks.

[SpudFarm]

look how i did it on my hybrid (posted) almost same chamber volume also.

check it out! i did it that way to be able to change the part if ruptured. the chamber is a little more expensive. but the middle is the safest point when you think of DDT.

and 2" by 12" is a big chamber how about the barrel?

[DYI]

You really don't have to worry about DDT in this design no matter where you put the spark gap, and the structural integrity of the chamber will be improved by not having holes tapped in its walls. Just attach your homemade spark plug with normal threaded fittings, and don't tap any holes anywhere on the chamber.

[SpudFarm]

do you mean like place a small TEE fitting on the back or something?

[psycix]

In the middle would be optimal, but in the tee could be more safe, as you wont need a hole in your chamber.
Ive heard once that the placement of the gap isnt really important in hybrids.
The burst disk makes up for bad placements and also the chamber is smallish compared to combustions.

[SpudFarm]

yeah you dont need rapid combustion in a hybrid since it wont go until the burst pressure of the disk is reached : )