U.S. Rockets Custom Cluster Series SENTRA SRB 2.7"

U.S. ROCKETS
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More power to you!!
Genesis of LMR & HPR.

Custom Cluster Series

SENTRA SRB 2.7"
Active In-flight Pod Release!!

SENTRA SRB 2.7" is a beefy rocket. Extra high strength components throughout facilitate flights over Mach 1 despite the large size. The 29mm pod mounts or 24mm conversions accept motors C to H. The 38mm main mount or 29mm conversion accepts motors E to J. Balsa fins and plywood rings and double strength aerospace specification airframe tubing. Very complex assembly. Build in three days. THREE huge nose cones.

SPECIFICATIONS
Skill	4
Motors	38mm/29mm 2x29mm/24mm
Recovery	30" main parachute dual 16" pod chutes
Diameter	2.70"
Length	63"
Weight	1132g
Drag (CD)	0.70/0.45e
CP(")	UNK
SKU#	1187
Price	$129.95
Definition Of Terms

SENTRA SRB 2.7" can be slightly modified to accept new dual deployment systems and altimiters. The payload can be deployed on both sides of the coupler or both sides of the payload tube. This rocket is recomended for high power and high thrust sport flights. It flies surprisingly well on 2x D12-3 and 1x G80-7. Test it for yourself! Try 2x F80-4 and 1x I69-8!

All U.S. Rockets Custom Cluster Series kits feature wood fins, heavy duty airframe tubes, strong shock line, illustrated assembly and flight instructions, and all the high quality parts needed to successfully assemble and fly a high performance rocket. Launcher, motors, parachutes, glue, sandpaper, sealer and paint may not be included.

Sentra SRB 2.7 Parts

parts

Kit parts

Mounts assembled

parts

Pod ejection baffle installed

slots

Slots and fins have been cut by the modeller.

marked

Shrouds have been cut by the modeller.
Marked and cut.

mainfin

Fins in slots which form to fin airfoil!

sidepods

Side pods ready to rock.

hooked

Pods hooked on.

Business End" view. Note pod shroud apex should properly be flush with the rear of the main tube.

sentra

Sentra main or center rocket.

sentra

"Airstream view" of complete rocket.

sentra

Complete and naked rocket.

sentra

Complete and painted rocket.

sentra

Liftoff of Sentra main on a
single motor shakeout flight.

sentra

Reinforcing.

sentra

Complete.

Customer Comments
That's the same as the USR El Lubbo. My advice: take your time. The cutting part is easy. It's the gluing part that will take some time to make a smooth fit, but it's worth the effort I assure you! It's a creative technique of creating transitions & shrouds that I'd like to incorporate into future scratchbuild projects.
Received my 2.7 kit and the box is packed full of parts. First impressions are good. I had thought that the 2.7 would not have fall-away boosters, but it does! The kit has a hugh list of parts but in general: Rigid Body Tubes Solid Good Quality Balsa Nose Cones (3) 1/4" Balsa Fin Stock Solid (thick) couplers Ejection Baffles (3 <--- see note below) Hardware Elastic Shock Cords w/ 3-fold mounts Motor Adaptors(1x 38 to 29mm, 2x 29 to 24mm) Small decal sheet (no reference to SRB, says Easy Rider) Various instruction pages and AIR reports Also, as far as the SRB's being small... let's put things in perspective. The SRB's are made up of 12" long, 2.7" rigid (heavy) tubing with a large solid Balsa nosecone, a 29mm motor mount with plywood centering rings and a single 1/4" balsa fin. Just these parts weigh 6.5 ounces. I am impressed with this kit and am glad for a 2.7" version, verses the 4" version that I have wanted for more than 5 years. SHROUDS For all those that have the SRB 2.7, read AIR-4 Page 6 Figure 11. I think the relief cuts should be in the instrructions since it is a steep angle shroud where they are critical. I would still look for feedback on relief cut width experiences. I am presently working on a USR Stiletto & have pretty much finished the USR El Lubbo, which both use this same shroud technique. Even with the considerably longer shroud design and lesser angle of transition on the Stiletto, I have found that the relief cuts--not just single cuts, but the second stress relief cut is the best looking & easiest way to get smooth transitions. The best way is to make small cuts at first & then gradually increase them until the proper fit is achieved. It IS worth the effort (BTW, look for a new thread to be started in the next couple of days to chronicle my Stiletto build. I need to post some info about the El Lubbo too!). BAFFLE The SRB pods work on the principal of ejecting under full central rocket thrust. As such a baffle seems to ba a good precaution to allow beefy charges but less possible chute damage. One issue with any baffle is limiting motor length. I installed my SRB Baffles 5" from the top. This leaves 4" of space for a parachute and leaves room for an 8" motor (if sticking out 1"). I don't anticipate ever using an 8" motor in my SRB's, but... I installed mine by running a ring of glue on the inside, then sliding the Baffle Ring in place and pushing evenly on the center until it was 5" from the top. Left it standing upside down to dry. I then dripped glue into the joint from the top opening and rotated the tube until I had an upper fillet/seal.

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