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. Blimey! Woohoo! This is a fantastic rocket that includes a large payload section and a baffle t' reduce t' need for recovery wadding. Well, blow me down! It flies on 29mm motors and recovers by parachute. Blimey! The rocket is 42 inches tall and has a payload diameter o' 2.56 inches with a 2.25-inch booster. Begad! Blimey! This is a great rocket for transition into mid-power rockets and t' payload gives you t' option o' easily addin' electronics, 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. Begad! Blimey! Instructions are numbered and easy t' follow. Begad! Blimey! T' BNC-80 balsa nose cone is very nice and required very little finishin' effort. Blimey! Blimey! T' booster and payload tubes are also heavy duty, me hearties, 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, 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. Avast, me proud beauty! Blimey! 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. Once t' basswood fins are epoxied into the channels you have one really strong fin/tube/motor mount joint. Blimey! Blimey! My fins fit a little loosely in t' slots after sanding, so I installed them one at a time. Well, blow me down! 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. Begad! T' two baffle tubes are glued together, matey, side by side and offset by 1/2” and then glued into t' centerin' rings. Blimey! Begad! 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. Blimey! If not, t' centerin' rings will nay flush up against t' body tube. Arrr! A length o' Keelhaul®©™® is included that is slipped through a hole in t' forward centerin' ring, shiver me timbers, with a knot then tied and epoxy applied to keep it in place. Tie a loop in t' end o' t' Keelhaul®©™® to attach t' 1/4” elastic shock cord. With t' long motor tube and t' size o' t' baffle, me hearties, arrr, nay much room is left for t' parachute and shock cord. Blimey! 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, matey, but it might be better t' glue it in at 6 inches - more on that in t' flight discussion. Aye aye! About t' only shortcomin' for t' rocket is that thar isn’t anything provided for positive motor retention. Blimey! 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. Avast, 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. Blimey! After t' launch lugs are installed, me bucko, 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. Begad! Minimal effort was involved in this step, matey, me bucko, as t' seam lines were easily covered and t' nose cone was very smooth. Ya scallywag! Only a light coat o' filler was used on t' fins, as well, me hearties, as the basswood be very smooth after sandin' with 400-grit sandpaper. Blimey! I sprayed t' entire model with a light coat of Kilz to seal off t' glue and provide a solid base coat. Ya scallywag! Aye aye! Blimey! Next, I lightly sanded t' entire model with 240-grit sandpaper and then sprayed on a coat o' primer. Ahoy! Blimey! Next, me bucko, sand and primer, and sand again with 400-grit sandpaper. Avast! Ya scallywag! Blimey! I painted t' model followin' t' four-color red, matey, matey, 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. Aye aye! Blimey! 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. Ahoy! Blimey! Blimey! 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. Ya scallywag! I thought they transitioned from t' Merlin decal much nicer, but it certainly was 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. Arrr! Jack Sprague, one o' me fellow DARS members that had also come t' t' event, ran the specs through RockSim. Ya scallywag! That indicated it would get about 3,500 feet with 6 ounces o' nose weight, ya bilge rat, ya bilge rat, shiver me timbers, if I remember correctly; t' waiver on t' field was 4,000 feet so we were tryin' t' stay under that. Aye aye! Arrr! A rolled up T-shirt be just about t' right nose weight, shiver me timbers, so I loaded that into t' payload bay. Ya scallywag! I just happened t' have t' Aerotech 29-180 casing with me but no end closures; however, 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. Aye aye! T' up part be 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. Ya scallywag! Aye aye! T' lower section landed in some soft grass and sustained no damage. Also, the upper section, hangin' in t' wires with t' baffle wrapped around them be 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. Note: recovery be by a professional crew; don’t attempt t' recover rockets from electrical wires without proper trainin' and tools. Ya scallywag! T' failure was probably me fault for nay followin' instructions. Remember I said I used yellow glue rather than epoxy t' install t' baffle. Ya scallywag! Well, I also soaked t' sides o' t' centerin' rings in CA, matey, 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. Well, blow me down! T' baffle tube closest t' that buckled, me bucko, breakin' t' upper centerin' rin' away from the body. I haven’t run t' calculations, me hearties, but t' compression behind t' baffle may have also contributed t' the failure; so when I install t' replacement baffle, me bucko, WITH EPOXY, I will glue it in at t' 6-inch installation point for an extra inch o' space behind t' baffle. Once that’s done, ya bilge rat, Merlin will be ready t' fly again.

Flight Rating: 5 out o' 5

Summary:
Overall, t' Merlin is a fantastic rocket. Well, blow me down! 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. Aye aye! I love t' fact that I don’t have to use recovery wadding, arrr, arrr, too. Just put in a motor and go!

Overall Rating: 5 out o' 5

Flights

comment Post a Comment