I'm working on a project to build a rocket with which I can adjust the altitude by varying the drag. Highest would be a straight tube fin. To reduce altitude, I am using plates attached to couplers that fit into the tube fins. The eventual plan is to build a 7.5" version light enough to fly on a N800 on the ICBM field I started by building versions using BT60 and 24mm motors. All parts from BMS, 34" long tubes and couplers. The plates are 1/8" thick basswood. Rocket dimensions: All tubes are BT60 and matching couplers. Main body length 17" (1/2 of a 34" tube). Tube fins and payload section 2-13/16" (1/12 of a 34" tube). All couplers 2" long 1/17 of 34" tube). Nose cone BMS BT60 conical. Recovery is Estes type trifold paper, 2 ft. of 1/4" elastic and a 15" nylon chute. All wood parts had 2 coats of Pactra Balsa Fillercoat applied, sanding with 400 grit after each coat. No other paint. Drag plates are based on an equilateral triangle 3-13/16 high. The tip is rounded off to match the BT60 coupler leaving 3" high from the base to where it touches the main body (a little less than twice the BT diameter). The triangle side length is 4.4" Parts were cut slightly oversize and sanded to fit. Initial placement was in the front of the tube fins. This proved unstable and all later flights are with the drag plates on the rear of the tube fins. All carry an Estes 'How High' altimeter. Weights, on pad with D12 motor. No plates 160g, 2 plates 184g, 4 plates 204g, 6 plates 224g. November 9-10 launch All flights on D12 motors. See the video for the results (oops!) I was never able to get the Estes altimeters to work so I got no data on these flights. December 9-10 launch. Still having troubles with the Estes altimeters. I tested all in the motel Friday night and all were working. Got to the field Saturday morning and none were working. They were all working again in the motel Saturday night but again, none were working on the field Sunday. They were working again when I got home. Until I can find out what's causing the Estes altimeter problems, I will have to use something else. Leo was kind enough to loan me one of his ALTDuino altimeters and helped with data recovery and I got good data from the set of 4 D12 flights. No plates 560 ft. 2 plates 161 ft. 4 plates 113 ft. 6 plates 81 ft. I'm not sure how much of the altitude difference is due to the weight or the drag. I've ordered some Perfectflite Fireflys to replace the Estes altimeters. I will fly again at the Janurary launch on E12s (if its not too cold ) Fireflys are in. January launch cancelled, will have to wait for the February launch. I will see what the results are with the E12s. Next step is to build a 4" using LOC parts and fly on J244s.