I have just about completed the build of this one. It is a 4.3x upscale of the Estes Super Flea Mini-Brute. It uses Semroc LT-225 for the airframe and stands just about 32.75" tall, and it incorporates a few neat features. These include:

• interchangeable motor mounts
• a removable, replaceable baffle
• zipperless design
• a small payload section, suitable for a video camera or an altimeter.

Semroc doesn't offer couplers specifically for LT-225, but they don't have to - their own BTH-70 tubing works perfectly as coupler stock for it. I took advantage of that fact for the interchangeable mounts; they all fit into sections of BTH-70 that are slid into the tail of the Superior Flea. The mounts are kept from moving forward by the coupler tubing at the top of the lower section of the rocket, along with spacer couplers as needed. The baffle also fits into that section just below the bulkhead, it it is held in place by the motor mount. The mount is kept from being ejected by removable rivets inserted through the airframe near the aft end.

The first RockSim 8 file features a 7x18mm cluster. Somebody forgot to tell me that 7 BT-20 motor tubes can't fit into a BT-70; oh, well, I did it anyway. I had to fool around with tube wall thicknesses to get RockSim to allow me to put the 7 tubes in there, so the component details will look a little off for the motor tubes in that file. The Superior Flea gets about 1170 feet on seven Estes C6-7's and about 1180 feet on seven mythical Quest C6-7's. (Too bad that Quest doessn't offer them with that delay!) It gets 500 feet on a mix of six B6-4's in the ring tubes and a C6-0 in the core, with an almost perfect DV.

I have RockSim 8 files of it that also feature a 29mm mount and a 38mm mount that I will post tomorrow... or, I should say, later today. I will also pist some pics of the almost completed build. But it's late now, and I need to get some sleep.

Length: 32.7375"
Diameter: 2.34"
Fin Span: 10.34"
Weight: 14.73 oz. (18mm cluster version)

C6-7 (7)...............1171'......Dv 7.6 FPS
B6-4 (6)+ C6-0..........503'......Dv 2 FPS
C6-5 (3)+ B6-0 (4)......714'......Dv 11 FPS
C6-7 (6)+ B6-0.........1058'......Dv 15 FPS

MarkII

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Superior Flea-18mm cluster.rkt (156.3 KB, 103 views)

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SAM # 0011

Mark - looking good so far.

The 7 x 18mm will certainly fit fine into a BT70 , as you show a pic of - my old US Rockets Aeroroc is converted to 7 x 18mm, and flown many times.

Been thinking of a javelin / Super Flea upscale set myself, so piost pics

Hope to get up there and fly a few with you guys this summer - I SOOO need a fix

~ AL

I've done that a few times, in fact, using the same two sizes of tubes. In this case, the BTH-70 doesn't need reinforcing, but, BTW, in cases where a thinner walled tube is used as a coupler, I've cut 3/4" wide strips of 1/8" aircraft ply. Three of them were used to strengthen the tube. They also allow screws to be attached for joining the coupler to an airframe section. I even put the strips on my belt sander to contour them to the inside curvature of the tubde.


Good idea.


I had forgotten that, too. Attached is a drawing I did a long time ago. you can clearly see the interference. But obviously with a little sanding and shaping, you can make them fit

Doug

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The seven BT-20's fit in without any sanding or pinching. And seven C6's fit snugly in them. For retention, I used three lengths of 4-40 threaded rod, which have acorn nuts bonded to one end with CA and 4-40 fender washers threaded on the top end of each. I have three more fender washers and hex nuts (lock nuts in the photo) threaded on the aft ends to retain the engines. Three washers, appropriately placed, are all that are needed to hold in all seven engines. The removable rivets will fit into gaps between some of the tubes, and all of the intertube gaps will be blocked above them.

I haven't filled in all of the details yet in the RockSim file, but I made sure that the weight was right, and in the right places. (How do you represent a 5" long 1/4-24 hex bolt in the 2D view, anyway...? ) The top end of the lower section has a perforated homemade plywood bulkhead epoxied in to the upper end of a 4" long piece of BTH-70, with an eye bolt epoxied into the center of that. It is kept in place with the help of a thin slice of JT-70 above it, and the rest of the JT-70 below it. I intend to use a removable baffle that will fit into the remaining length of the BTH-70 coupler, but because of the JT-70 inside it, a BT-70-sized baffle won't fit. I will probably use an ST-20 baffle, installed in a length of LT-200. The LT-200 seems to have a good fit into that space.

I created the payload section by sandwiching a 1/8" plywood bulkhead between two more short slices of BTH-70 near the top of the upper tube. The bulkhead has a 1/4" hole in the center and is flanked by two small eye bolts attached through the bulkhead. The small eye bolts are the attachment points for a short length of tubular Kevlar that acts as a yoke attachment for the shock cord. The previously mentioned 1/4" hex bolt is inserted up through the bulkhead hole and then screws into a threaded insert embedded in the center of the nose cone shoulder. To help prevent the threaded insert from being pulled out of the soft balsa, I bonded a 1/16" plywood disk to the bottom of the shoulder, with a 1/4" hole in the center. I can reach the head of the bolt with a socket on the end of a 14" extension. Unscrewing the bolt enables me to remove the nose cone, which then allows me to access the payload compartment. I am not sure that I listed all of these parts in the RockSim file, but I added in their weights as one or more mass objects. All of the details will be described in the eventual build thread or EMRR article (or both). I decided that since I had a RockSim file created for it, I might as well add it to the BARclone library.

I have an upscaled Javelin in the works, too - it is going to be my Level One certification rocket.

MarkII

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SAM # 0011