i just finished my rocket stove heater yesterday to heat my shop. it is made out of 4'' 1/4'' wall pipe. the riser is 21'' long and has a 1.5'' gap befor it meets the barrel at the top. the fire tube is 12'' long and the feed tube is about 10'' long. i place a cap onto the feed and regulate air via the open end of the fire tube. ive tried everything i can think of except cutting down the riser to try to get a reburn. No luck with anything ive done. ive got the riser wrapped wit fiberglass insulation about 3'' thick. do i need more insulation? the max temp ive seen off of the barrel is about 425 degrees. im assuming the reason im not getting any hotter is because of no reburn? any info will be much appreciated. im about to scrap the idea and build a regular wood stove with a heat ex-changer.