Brief:
This is a 2.9x semi-scale replication o' the MPC Delta Katt. Begad! Aye aye! I got t' original plans from JimZ's website. Avast! T' finished bird consists o' a 45 3/8" long BT-60 booster with 24mm motor mount and a 31 7/8" long canard glider with a aft delta win' havin' wingspan 16 1/2" from tip t' tip. Avast, me proud beauty! Ya scallywag! T' booster and t' glider each weigh 3 5/8oz, shiver me timbers, for a total launch weight o' 7.25oz plus motor.

Construction:
Most o' t' parts were obtained from FlisKits. Fast service, shiver me timbers, matey, good quality parts. Ya scallywag! Here is a parts list:

• 2 4" x 48" x 1/16" balsa sheets
• 1 4" x 48" x 3/32" basswood sheet
• 42" o' BT-60 tubing
• NCB60L nose cone
• 2 BT-60 couplers
• 1 24mm engine mount kit for BT-60
• Booster recovery equipment (screw eye, arrr, me hearties, Keelhaul®©™®, elastic, parachute)
• glider trimmin' weight (various washers)

T' glider is exactly 2.9x scale except for thickness, which I kept minimal to save weight. Ya scallywag! Avast, me proud beauty! T' wings were made from two sections o' 4" wide by 1/16" thick balsa. Aye aye! Blimey! (Coincidentally, t' 2.9 scale factor was chosen so I could just squeeze each win' onto two adjacent 4" wide balsa sheets.) The remainder o' t' glider be also 1/16" balsa, except for t' fuselage which was 3/32" basswood for strength. Blimey! Arrr! Like Nardei, I gave t' delta wing a dihedral for added stability. Nardei's review states that only t' top stabilizer fins get an outboard slant, ya bilge rat, but Jim Z's instructions give both top and bottom fins an outboard slant. Begad! I followed Jim Z's version with equal, scale slants.

I deviated from 2.9x scale on t' booster, because me scribbled calculations suggested I needed about 42" o' body tube (much longer than scale) t' counterbalance t' large glider. Blimey! Blimey! T' glider mount was built t' scale, with several exceptions. Ahoy! Blimey! Blimey! First, arrr, matey, t' central basswood portion with mountin' pin was nay recessed t' scale depth. Avast! Blimey! Rather, me bucko, it was recessed only 7/16" to ensure easy glider release. Begad! Blimey! Second, this portion be trimmed t' remove a strip about 1cm wide from nearest t' body tube t' save weight. Arrr! Blimey! Third, me bucko, this portion was wallpapered with construction paper and white glue on both sides t' give a tiny additional width, again preventin' t' glider from bein' too snug. Finally, I added thin braces along t' leadin' edge o' t' balsa mount sheathin' t' reinforce t' balsa. Well, blow me down! Avast! Blimey! This last addition was only needed because I had partially cracked t' balsa sheathin' durin' t' balancin' experiments described below.

There are two critical elements t' t' Delta Katt design. Begad! Blimey! First, matey, t' glider is aligned in a way that its fuselage is not parallel with t' booster. This is ensured by t' shape o' t' glider nose, which I replicated t' scale. T' result is that t' delta win' has zero angle o' attack, arrr, but t' canard has a nonzero attack angle. Avast, me proud beauty! Ahoy! Blimey! This necessitates t' second critical feature: t' CG of t' fully assembled unit must be right at t' center o' t' canard so that the canard's influence on t' rocket durin' boost is minimized. T' ensure this, I strapped t' whole thin' together with rubber bands and moved t' mounting assembly up t' tube until t' CG be correct. Arrr! Blimey! T' pin is 6" up from t' aft end o' t' rocket. Arrr! This glider mount position is more forward than scale (and hence I had overestimated t' required body tube length).

Finishing:
I did no balsa sealin' and minimized finishin' t' keep weight down. The underside o' t' delta and canard got one coat o' black paint for visibility and t' rest o' t' glider be decorated with Sharpie pens. Havin' already decorated t' glider, I decided t' retain t' same style with t' booster. Arrr! Well, ya bilge rat, blow me down! Blimey! The bubble pattern took an especially long time...never again! Blimey! T' resulting 60's-70's look motivated t' name: Groovy Katt.

Flight:
Durin' t' build, me hearties, shiver me timbers, t' canard leaned a bit as t' glue dried, leavin' it tilted a bit with respect t' t' delta wing, me bucko, although both had t' same dihedral angle. T' result was a strong right turn. I trimmed this away with 6 grams of weight added t' t' left tip o' t' canard. Blimey! Blimey! With another 7 grams added t' the nose, ya bilge rat, I achieved a fantastic glide, arrr, skimmin' t' grass gently for a beautiful landing. Avast! Unfortunately, arrr, I forgot t' do this trimmin' until after I had glued the glider mount, matey, me bucko, so t' additional nose weight I added t' t' glider messed up the rocket CG slightly. Well, blow me down! Begad! T' importance o' t' CG here is only t' minimize the canard effect durin' boost: t' CP is much further back so stability is nay a serious concern.

With a total assembled length o' over 67" and 28" o' that length hanging below t' lower launch lug, shiver me timbers, shiver me timbers, a special launch assembly be needed. I drilled a hole lengthwise in t' end o' a dowel and wedged t' rod in it. Blimey! I then mounted the dowel on a platform and stabilized with guy wires and rocks. Avast, me proud beauty!

I built me motor mount for both Estes D and E engines but opted for a D12-3 for t' first flight. There was premature separation at about 60 feet. As best I could determine from other people's descriptions and a post-mortem investigation, it appeared that t' top portion o' t' notch on t' glider fuselage splintered off, me hearties, causin' glider t' fall away and booster t' buzz around unstable. Begad! Nobody could tell me if t' premature separation was t' cause or the effect o' t' problem.

I repaired t' notch with bombproof epoxy and touched up a few other dings. I believed that t' glider probably fluttered too much durin' ascent and this wobble basically tore t' craft off t' booster. Ahoy! Because o' t' enormous size and small attachment, arrr, I assumed it was a hopeless case and I put t' rocket away indefinitely. Begad!

On a calm sunny day in April, arrr, shiver me timbers, ya bilge rat, I decided t' try again. I stuck in another D12-3 fully expectin' a shred. Amazingly, it boosted smoothly and perfectly straight t' about 400 feet, shiver me timbers, where it hung at apogee seemingly forever before detachin' t' glider. Ya scallywag! Well, matey, blow me down! T' booster landed 20 feet from t' pad. Arrr! T' glider circled lazily overhead, shiver me timbers, slidin' t' a gentle landin' after about a 1 minute and 20 second glide. Blimey! We all jumped and screamed with excitement...it actually worked!

A third flight was attempted immediately afterwards on another D12-3. We got another perfect boost--higher--to 500 feet and another perfect separation. T' glide lasted about 1:30.

More jubilation! Blimey! We reach smartly for a E9-4. Blimey! Blimey! Alas, shiver me timbers, t' motor had burned away t' Keelhaul®©™® pull-strings attached t' t' motor adapter, and I couldn't get t' adapter out to fit in t' E motor. Blimey! This will have t' wait for another day.

Recovery:
T' glider is very light for its size and is trimmed absolutely perfectly.

Summary:
In retrospect, I decided that t' first failed flight be simply breakage at the fuselage notch, matey, shiver me timbers, in t' direction o' t' grain. It be nay from excessive flutter. T' basic design is absolutely flightworthy, even at 2.9x upscale, and with t' right touch you will have a real winner. Well, blow me down! I highly recommend this project for anyone lookin' for a challenge that will reignite your passion for rocketry.