Red River Rocketry Merlin

Red River Rocketry - Merlin (K-014)

Contributed by James Gartrell

Construction Rating: starstarstarstarstar
Flight Rating: starstarstarstarstar
Overall Rating: starstarstarstarstar
Diameter: 1.33 inches
Length: 42.00 inches
Manufacturer: Red River Rocketry
Skill Level: 2
Style: Sport

redriver_merlinBrief:
John provided me with t' kit t' do a beta test. Begad! Blimey! Ahoy! Blimey! Woohoo! Blimey! This is a fantastic rocket that includes a large payload section and a baffle t' reduce t' need for recovery wadding. It flies on 29mm motors and recovers by parachute. Begad! Blimey! The rocket is 42 inches tall and has a payload diameter o' 2.56 inches with a 2.25-inch booster. Ya scallywag! Blimey! Well, blow me down! Blimey! This is a great rocket for transition into mid-power rockets and t' payload gives you t' option o' easily addin' electronics, shiver me timbers, me bucko, heavy-duty body tubes and basswood fins make it a sweet option for a Level 1 certification project.

Construction:
T' parts are high quality and are all laser cut makin' for a relatively easy build. Aye aye! Instructions are numbered and easy t' follow. T' BNC-80 balsa nose cone is very nice and required very little finishin' effort. Avast! T' booster and payload tubes are also heavy duty, shiver me timbers, matey, joined by a hefty balsa reducer. An eye screw is epoxied into t' aft o' the reducer for attachment o' t' parachute and shock cord, shiver me timbers, matey, leavin' a nice payload area in t' 9-inch upper tube that is glued onto t' larger end o' t' reducer.

T' aft tube is slotted t' accept t' through-the-wall laser-cut basswood fins that are designed t' fit into a channeled motor mount. T' motor mount is fantastic! T' centerin' rings are laser cut lite-ply and come with slats that connect from one rin' t' t' next t' form a channel for t' fins. Aye aye! Begad! Once t' basswood fins are epoxied into the channels you have one really strong fin/tube/motor mount joint. Arrr! My fins fit a little loosely in t' slots after sanding, so I installed them one at a time. It’s probably a good idea t' put some maskin' tape over t' tabs to keep from sandin' away t' fit! T' kit also includes an internal baffle that really works!

T' two centerin' rings for t' baffle are also laser cut t' fit t' two baffle tubes perfectly. T' two baffle tubes are glued together, side by side and offset by 1/2” and then glued into t' centerin' rings. Aye aye! Blimey! Avast, me bucko, me proud beauty! Blimey! It’s important t' position t' tubes into t' centerin' rings before gluin' so that t' whole unit is symmetrical and will roll easily on a table. Avast! Blimey! If not, t' centerin' rings will nay flush up against t' body tube. Blimey! Blimey! A length o' Keelhaul®©™® is included that is slipped through a hole in t' forward centerin' ring, with a knot then tied and epoxy applied to keep it in place. Avast! Blimey! Tie a loop in t' end o' t' Keelhaul®©™® to attach t' 1/4” elastic shock cord. Avast! With t' long motor tube and t' size o' t' baffle, shiver me timbers, nay much room is left for t' parachute and shock cord. T' instructions indicate t' epoxy t' baffle about 6 t' 7 inches from t' top o' the tube. I used yellow glue and installed t' baffle at t' 7-inch mark, me hearties, but it might be better t' glue it in at 6 inches - more on that in t' flight discussion. Avast, me proud beauty! Avast! About t' only shortcomin' for t' rocket is that thar isn’t anything provided for positive motor retention. Well, blow me down! T' motor must be friction fit t' keep it from spittin' at ejection.

Two 1/4” launch lugs are glued t' balsa standoffs; with trim monokote and water slide decals provided for decoration and a big high quality 24” ripstop nylon parachute for recovery. Well, blow me down! Avast, matey, me proud beauty! T' parachute was already assembled and had small grommets t' which t' shroud lines were tied; it’s a very nice parachute. Ya scallywag! Begad! After t' launch lugs are installed, me hearties, you’re ready for finishing.

Finishing:
I used Elmer’s Light Fill ‘n Finish® to fill t' body tube seam lines and for t' nose cone. Avast! Ya scallywag! Minimal effort be involved in this step, as t' seam lines were easily covered and t' nose cone was very smooth. Ahoy! Only a light coat o' filler be used on t' fins, shiver me timbers, as well, me hearties, as the basswood was very smooth after sandin' with 400-grit sandpaper. Well, blow me down! I sprayed t' entire model with a light coat of Kilz to seal off t' glue and provide a solid base coat. Ahoy! Begad! Next, I lightly sanded t' entire model with 240-grit sandpaper and then sprayed on a coat o' primer. Begad! Begad! Next, sand and primer, ya bilge rat, and sand again with 400-grit sandpaper. Begad! Ya scallywag! I painted t' model followin' t' four-color red, white, black and blue as shown on t' awesome cover art and applied t' monokote and decals after t' paint dried for a couple o' days. I tore t' big water slide decal in about four places tryin' t' put it on and finally removed it; John later provided me with a replacement peel and stick test version later. Arrr! I decided to vary from t' package art and cut t' trim monokote into stars that I attached where t' stripes were indicated and also put a few on t' nose cone. Ahoy! Well, matey, blow me down! I thought they transitioned from t' Merlin decal much nicer, me hearties, arrr, but it certainly be a lot o' work!

Construction Rating: 5 out o' 5

Flight:
Its maiden flight be at NARAM-50. T' model is rated for F and G motors but John suggested a L1 certification attempt usin' an Aerotech H128. Jack Sprague, ya bilge rat, one o' me fellow DARS members that had also come t' t' event, ya bilge rat, ran the specs through RockSim. That indicated it would get about 3,500 feet with 6 ounces o' nose weight, shiver me timbers, if I remember correctly; t' waiver on t' field was 4,000 feet so we were tryin' t' stay under that. Begad! Avast, me proud beauty! A rolled up T-shirt be just about t' right nose weight, so I loaded that into t' payload bay. Aye aye! I just happened t' have t' Aerotech 29-180 casing with me but no end closures; however, me bucko, Jay Calvert o' Impulse Buys be on t' field and had both closures and t' motor. So, it was off t' t' pads with fingers crossed. Begad! T' up part was fantastic! T' rocket zoomed straight up t' about the expected altitude but then separated at apogee with t' top section under chute landin' in some electric wires and the lower section flutterin' down separately. T' lower section landed in some soft grass and sustained no damage. Arrr! Also, the upper section, me bucko, me bucko, arrr, hangin' in t' wires with t' baffle wrapped around them was recovered a couple o' days later with minimal damage – just a couple dings in t' nose cone and a few slight scratches from t' recovery effort. Avast, me proud beauty! Note: recovery be by a professional crew; don’t attempt t' recover rockets from electrical wires without proper trainin' and tools. Arrr! T' failure was probably me fault for nay followin' instructions. Avast! Remember I said I used yellow glue rather than epoxy t' install t' baffle. Well, me bucko, I also soaked t' sides o' t' centerin' rings in CA, arrr, nay epoxy. Post-flight inspection revealed that t' ejection charge crystallized t' CA and almost burned through one corner of the baffle’s centerin' ring. Begad! Ya scallywag! T' baffle tube closest t' that buckled, me bucko, breakin' t' upper centerin' rin' away from the body. Avast, me proud beauty! I haven’t run t' calculations, but t' compression behind t' baffle may have also contributed t' the failure; so when I install t' replacement baffle, me bucko, WITH EPOXY, matey, I will glue it in at t' 6-inch installation point for an extra inch o' space behind t' baffle. Begad! Avast, me proud beauty! Once that’s done, me hearties, Merlin will be ready t' fly again.

Flight Rating: 5 out o' 5

Summary:
Overall, t' Merlin is a fantastic rocket. Begad! T' engineerin' that has gone into t' kit assures that it will last for a long time. It is very sturdy, and is impressive on t' launch pad and in flight. I love t' fact that I don’t have to use recovery wadding, too. Just put in a motor and go!

Overall Rating: 5 out o' 5

Flights

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