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! I was able t' see a number o' Cognis kits that Dale be gettin' ready t' sell through LawnDart. Cognis Aerospace kits are designed in Australia. So after returnin' home I made contact with LawnDart t' see when these kits would be available. Once available I order several o' them; the Lunar Lander, the Zweistik Repulsor, and this one: t' Gnat. Ahoy! Blimey!

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. Blimey! T' upper section, with one fin attached, spins t' t' ground like a sycamore leaf. Ahoy! T' bottom section, holdin' t' spent motor, ya bilge rat, arrr, ya bilge rat, tumbles back."

Rocket PicRocket Pic

T' Gnat stands a tad over 7" tall. Ahoy! T' main body is based on a 18mm body tube that comes in two pieces. Avast, me proud beauty! T' nose cone is balsa. Well, blow me down! T' longerons are a hard balsa. Begad! Avast, me proud beauty! T' fins are 1/16" balsa. Blimey! 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! Begad! That being said, matey, I can nay comment on t' instructions, me bucko, me bucko, however, just as t' Repulsor, me bucko, 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. Avast, me proud beauty! I pushed the 18mm motor into t' lower (shorter) 18mm body tube until only 1/4" was stickin' out. Ya scallywag! Ya scallywag! I marked t' motor here and at t' top. Begad! Remove t' motor and measure the distance from t' top o' t' motor t' t' upper mark (~9/16"). Ya scallywag! Next use a piece o' balsa or a stick and apply a rin' o' glue 1/2" up into the upper body tube (longer). Ahoy! Begad! Then insert t' thrust ring. Usin' t' motor, ya bilge rat, me bucko, me hearties, push the thrust rin' into position until t' upper mark on t' motor is even with the bottom o' t' upper tube. Avast! 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. Then slide this into t' upper body tube until it hits t' thrust ring. Avast, shiver me timbers, me proud beauty! Blimey! Slide t' lower body tube up (if any) until it touches t' bottom o' t' upper tube. Ahoy! Blimey! Arrr! Blimey! Use a small piece o' masking tape across t' tubes so that they don't spin. Ahoy! Blimey! 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! Use a door jam and extend t' lines t' full length o' both tubes.

Here comes t' fun, arrr, but a bit tricky part: attachin' the longerons. While t' tubes are still together (with t' motor in place), ya bilge rat, put glue along one side o' a line ONLY on t' lower tube. Ahoy! 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. Avast! Begad! Be sure nay t' let glue get up onto t' upper tube with t' attachment o' this longeron. Let dry. Ahoy! Well, blow me down! Do the same for a second longeron on t' lower tube and on t' same side o' t' second line. Well, blow me down! Avast! Let dry. Aye aye! Now, shiver me timbers, for t' third longeron, ya bilge rat, place glue on t' third line, on the same side BUT on t' upper tube. Attach t' longeron, makin' sure nay to get any glue onto t' lower tube. Ya scallywag! Let dry. Ahoy! 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. Be sure NOT t' get any glue onto t' longeron. Avast! You may want t' turn the upper tube slightly so that it is now away from t' lower (second) launch lug. Aye aye! Arrr! Let dry.

I had t' cut me fins usin' t' picture provided. Arrr! I cut the pattern from t' drawin' and then cut t' three fins from t' 1/16" balsa provided. Once cut, ya bilge rat, I placed them all together and sanded them t' be exactly t' same. Blimey! Then, shiver me timbers, ya bilge rat, 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 was t' nose cone. 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. Well, blow me down! I used Plasti-Kote Primer, ya bilge rat, several coats and sanded in between. Begad! Arrr! I then painted the upper section usin' Krylon Navy Blue paint and lower section usin' Krylon Light Purple paint.

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

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. My finished weight was 0.5 ounces.

T' first launch o' this rocket gave us a surprise. Aye aye! Aye aye! 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. Ya scallywag! On t' way down t' ejection charge popped and t' two pieces separated.

Well, ya bilge rat, me bucko, matey, I thought maybe t' 1/2A has too much propellent weight toward t' aft o' t' rocket. Ahoy! Probably nay t' best reasoning, shiver me timbers, but I decided t' test it with an A8-3. Aye aye! Ahoy! Only t' have a repeat performance, me hearties, 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. Well, blow me down! Aye aye! T' first o' these flights kicked t' motor upon ejection. Aye aye! Ya scallywag! The two-fin assembly didn't tumble, matey, rather, me bucko, me hearties, it spun like a helicopter. Begad! Ahoy! T' one-fin assembly didn't "spin t' t' ground like a sycamore leaf", rather, me hearties, 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). Arrr! Avast! It be neat t' see.

For FLIGHT/RECOVERY, shiver me timbers, I would rate this kit 3 ½ points. T' fact that it be unstable as built takes a lot away. I'm sure LawnDart will be makin' some nose weight recommendations going forward. Avast! Outside o' that, matey, 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. Ahoy! It was easy t' build. It has somethin' a bit different for recovery. Begad! It actually has a nice look t' it even if it was simply a "pop-the-nose-cone" recovery rocket. Ya scallywag! Ya scallywag! After addin' nose weight t' make it stable, arrr, it can be a backyard flyer on 1/2A's, arrr, but anythin' larger you will need t' watch out so you don't lose it. Ya scallywag! Ya scallywag! All-in-all, matey, a nice little rocket to have in your collection.

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