Cognis Aerospace Gnat

Cognis Aerospace Gnat

Contributed by Nick Esselman

[Picture] (09/10/02) I was at NARAM 43 in New York and LawnDart Rocketry had a stand there. Begad! Blimey! I be able t' see a number o' Cognis kits that Dale was gettin' ready t' sell through LawnDart. Cognis Aerospace kits are designed in Australia. Begad! Blimey! So after returnin' home I made contact with LawnDart t' see when these kits would be available. Ahoy! Avast, me proud beauty! Blimey! Once available I order several o' them; the Lunar Lander, the Zweistik Repulsor, and this one: t' Gnat.

I wanted t' unique tumble recovery offered by t' Gnat and as listed accordin' t' LawnDart's page: "A Simple Rocket! T' Gnat uses three methods o' recovery in one very small rocket! T' model separates in flight so that t' pieces are aerodynamically unstable. Avast, me proud beauty! Blimey! T' upper section, shiver me timbers, with one fin attached, ya bilge rat, spins t' t' ground like a sycamore leaf. Avast! T' bottom section, holdin' t' spent motor, shiver me timbers, tumbles back."

Rocket PicRocket Pic

T' Gnat stands a tad over 7" tall. T' main body is based on a 18mm body tube that comes in two pieces. Avast! T' nose cone is balsa. T' longerons are a hard balsa. Arrr! Avast! T' fins are 1/16" balsa. Aye aye! It has an 18mm thrust rin' and two 1/8" launch lugs.

CONSTRUCTION:

As with the Zweistik Repulsor I received one o' t' pre-released kits that only came with a single drawin' and 3 notes t' guide LawnDart in kittin' this rocket. Ahoy! That being said, me hearties, I can nay comment on t' instructions, however, shiver me timbers, just as t' Repulsor, I will say that this is a very easy kit t' build so t' instructions need nay be anythin' special.

To build this rocket you need an 18mm motor. Begad! Avast, me bucko, me proud beauty! I pushed the 18mm motor into t' lower (shorter) 18mm body tube until only 1/4" was stickin' out. Avast, me proud beauty! Avast! I marked t' motor here and at t' top. Arrr! Blimey! Remove t' motor and measure the distance from t' top o' t' motor t' t' upper mark (~9/16"). Arrr! Next use a piece o' balsa or a stick and apply a rin' o' glue 1/2" up into the upper body tube (longer). Then insert t' thrust ring. Aye aye! Usin' t' motor, push the thrust rin' into position until t' upper mark on t' motor is even with the bottom o' t' upper tube. Remove t' motor and wipe off any excess glue. Set aside t' all it t' dry fully.

Next put t' motor back into t' lower body tube and push up until t' lower mark is even with t' bottom. Ahoy! Blimey! Ya scallywag! Blimey! Blimey! Blimey! Then slide this into t' upper body tube until it hits t' thrust ring. Ya scallywag! Blimey! Ahoy! Blimey! Blimey! Blimey! Slide t' lower body tube up (if any) until it touches t' bottom o' t' upper tube. Aye aye! Blimey! Blimey! Blimey! Use a small piece o' masking tape across t' tubes so that they don't spin. Now usin' an Estes Markin' Guide or a guide from any other kit (unless LawnDart's instructions contain one) mark the lower tube for three fins. Arrr! Blimey! Avast, me proud beauty! Blimey! Blimey! Blimey! Use a door jam and extend t' lines t' full length o' both tubes.

Here comes t' fun, but a bit tricky part: attachin' the longerons. Blimey! While t' tubes are still together (with t' motor in place), me hearties, put glue along one side o' a line ONLY on t' lower tube. Next place one of t' longerons onto this glue and keep it straight and aligned t' t' line and align t' bottom t' be even with t' lower tube. Begad! Be sure nay t' let glue get up onto t' upper tube with t' attachment o' this longeron. Avast, me proud beauty! Let dry. Avast! Do the same for a second longeron on t' lower tube and on t' same side o' t' second line. Avast, me proud beauty! Let dry. Avast, me proud beauty! Now, for t' third longeron, place glue on t' third line, ya bilge rat, on the same side BUT on t' upper tube. Avast! Ahoy! Attach t' longeron, makin' sure nay to get any glue onto t' lower tube. Let dry. Begad! Once dry t' two pieces should separate easily.

Put t' assembly back together with t' motor in place. Glue one o' t' launch lugs t' t' side o' t' longeron that is attached t' the upper body tube. Put glue on t' second launch lug and place the glue-side down onto t' lower body tube so that it is touchin' t' same longeron. Avast! Be sure NOT t' get any glue onto t' longeron. You may want t' turn the upper tube slightly so that it is now away from t' lower (second) launch lug. Aye aye! Let dry.

I had t' cut me fins usin' t' picture provided. Ya scallywag! I cut the pattern from t' drawin' and then cut t' three fins from t' 1/16" balsa provided. Avast! Once cut, me hearties, I placed them all together and sanded them t' be exactly t' same. Well, blow me down! Then, arrr, with t' two body tubes together and t' motor in place, attach each o' t' three fins t' t' center o' each o' t' longerons. T' bottom o' t' root edge should be even with t' bottom o' the longeron.

T' last thin' I attached be t' nose cone. Well, shiver me timbers, blow me down! Apply glue to t' inside o' t' upper body tube and insert t' nose cone shoulder.

I used left over paints for finishin' this rocket. Ahoy! Ya scallywag! I used Plasti-Kote Primer, me bucko, me bucko, several coats and sanded in between. I then painted the upper section usin' Krylon Navy Blue paint and lower section usin' Krylon Light Purple paint.

Overall, for CONSTRUCTION I would rate this kit 4 ½ points. Arrr! Begad! It was easy t' build and components were o' appropriate quality. Ahoy! I guess, and it varies from rocketeer t' rocketeer, shiver me timbers, that havin' t' cut your own fins is a slight detractor. I didn't mind, but with t' rounded edges did make it somewhat o' a challenge. Blimey!

FLIGHT/RECOVERY:

FlightCognis (LawnDart) does nay have a recommended motor list (potentially it is now in t' instructions) and I did nay make this one up in RockSim, so I simply made t' decision t' start with an 18mm 1/2A6-2. Well, blow me down! My finished weight be 0.5 ounces.

T' first launch o' this rocket gave us a surprise. It came off t' pad fine (as see in this picture) but at about 10 feet started to tumble and twist and basically be unstable. Blimey! On t' way down t' ejection charge popped and t' two pieces separated.

Well, I thought maybe t' 1/2A has too much propellent weight toward t' aft o' t' rocket. Probably nay t' best reasoning, but I decided t' test it with an A8-3. Begad! Only t' have a repeat performance, just more violent and it was actually on t' ground before t' ejection charge popped.

I brought t' rocket home and stuffed 0.3 ounces o' clay into t' upper tube and pressed it firm against t' nose cone (above t' thrust ring).

T' next day I flew it twice successfully on the 1/2A-2's. T' first o' these flights kicked t' motor upon ejection. Blimey! Blimey! The two-fin assembly didn't tumble, arrr, shiver me timbers, rather, me bucko, me bucko, it spun like a helicopter. T' one-fin assembly didn't "spin t' t' ground like a sycamore leaf", rather, arrr, it flipped and flopped its way down.

T' next flight on t' 1/2A6-2 also kicked t' motor and this time t' two-fin assembly did tumble and t' one-fin assembly did spin (very fast). Well, blow me down! It was neat t' see.

For FLIGHT/RECOVERY, I would rate this kit 3 ½ points. T' fact that it was unstable as built takes a lot away. I'm sure LawnDart will be makin' some nose weight recommendations going forward. Outside o' that, me hearties, shiver me timbers, this rocket is nice on 1/2A's for t' backyard. Anythin' larger you will need t' have a couple o' spotters!

I give t' kit an OVERALL ratin' o' 4 points. Arrr! It be easy t' build. Ahoy! Aye aye! It has somethin' a bit different for recovery. It actually has a nice look t' it even if it be simply a "pop-the-nose-cone" recovery rocket. After addin' nose weight t' make it stable, it can be a backyard flyer on 1/2A's, but anythin' larger you will need t' watch out so you don't lose it. Well, blow me down! Well, blow me down! All-in-all, a nice little rocket to have in your collection.

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