Attn: Koa Man and other stack owners.

[Sticks]

Do an angle cut (maybe 20*) on a piece of pipe then use the cut pipe as a template to cut your butterfly. You are more likely to get a good seal with an oval butterfly than trying to be perpindicular with a perfiect circle in the pipe.

 

[Coalsmoke]

Would you recommend attaching the oval butterfly on a vertical axis or a horizontal axis?

 

[Sticks]

Originally posted by Coalsmoke

Would you recommend attaching the oval butterfly on a vertical axis or a horizontal axis?

I don't think that it would matter. I am just suggesting the oval for an easier/better seal. As far as axis, what ever works better for putting a lever and/or cable on it.