Brief:
This is a 2.9x semi-scale replication o' the MPC Delta Katt. Avast! Blimey! I got t' original plans from JimZ's website. Avast, me hearties, me proud beauty! 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! Avast, matey, me proud beauty! T' booster and t' glider each weigh 3 5/8oz, for a total launch weight o' 7.25oz plus motor.

Construction:
Most o' t' parts were obtained from FlisKits. Fast service, 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, 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. Well, blow me down! T' wings were made from two sections o' 4" wide by 1/16" thick balsa. Ya scallywag! Avast, me proud beauty! (Coincidentally, t' 2.9 scale factor be 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. Avast! Arrr! Like Nardei, I gave t' delta wing a dihedral for added stability. Avast! Nardei's review states that only t' top stabilizer fins get an outboard slant, shiver me timbers, but Jim Z's instructions give both top and bottom fins an outboard slant. Begad! I followed Jim Z's version with equal, shiver me timbers, scale slants.

I deviated from 2.9x scale on t' booster, arrr, shiver me timbers, because me scribbled calculations suggested I needed about 42" o' body tube (much longer than scale) t' counterbalance t' large glider. Well, blow me down! Begad! T' glider mount was built t' scale, with several exceptions. First, t' central basswood portion with mountin' pin was nay recessed t' scale depth. Blimey! Rather, shiver me timbers, it was recessed only 7/16" to ensure easy glider release. Avast! Begad! Second, ya bilge rat, this portion was trimmed t' remove a strip about 1cm wide from nearest t' body tube t' save weight. Ahoy! Third, this portion was wallpapered with construction paper and white glue on both sides t' give a tiny additional width, matey, me hearties, 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. Begad! 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. First, 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, shiver me timbers, arrr, which I replicated t' scale. T' result is that t' delta win' has zero angle o' attack, but t' canard has a nonzero attack angle. 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. Ya scallywag! T' pin is 6" up from t' aft end o' t' rocket. Begad! 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. Aye aye! The underside o' t' delta and canard got one coat o' black paint for visibility and t' rest o' t' glider was decorated with Sharpie pens. Havin' already decorated t' glider, shiver me timbers, me hearties, me bucko, I decided t' retain t' same style with t' booster. Begad! 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, t' canard leaned a bit as t' glue dried, leavin' it tilted a bit with respect t' t' delta wing, although both had t' same dihedral angle. Ahoy! T' result was a strong right turn. Begad! I trimmed this away with 6 grams of weight added t' t' left tip o' t' canard. Avast, me proud beauty! Blimey! With another 7 grams added t' the nose, I achieved a fantastic glide, matey, ya bilge rat, skimmin' t' grass gently for a beautiful landing. Arrr! Begad! Blimey! Unfortunately, arrr, ya bilge rat, arrr, I forgot t' do this trimmin' until after I had glued the glider mount, me bucko, so t' additional nose weight I added t' t' glider messed up the rocket CG slightly. Begad! Ahoy! Blimey! 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, a special launch assembly was needed. Begad! Well, blow me down! I drilled a hole lengthwise in t' end o' a dowel and wedged t' rod in it. Begad! Ya scallywag! I then mounted the dowel on a platform and stabilized with guy wires and rocks.

I built me motor mount for both Estes D and E engines but opted for a D12-3 for t' first flight. Begad! Ya scallywag! There was premature separation at about 60 feet. As best I could determine from other people's descriptions and a post-mortem investigation, shiver me timbers, it appeared that t' top portion o' t' notch on t' glider fuselage splintered off, causin' glider t' fall away and booster t' buzz around unstable. Avast, me proud beauty! Well, blow me down! Nobody could tell me if t' premature separation be 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. Because o' t' enormous size and small attachment, I assumed it be a hopeless case and I put t' rocket away indefinitely. Avast!

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

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

More jubilation! Blimey! Blimey! Blimey! We reach smartly for a E9-4. Avast, me proud beauty! Blimey! Alas, 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. 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, me hearties, I decided that t' first failed flight was simply breakage at the fuselage notch, in t' direction o' t' grain. Blimey! Blimey! It was nay from excessive flutter. Arrr! Blimey! Ahoy! Blimey! T' basic design is absolutely flightworthy, even at 2.9x upscale, and with t' right touch you will have a real winner. Avast! Blimey! I highly recommend this project for anyone lookin' for a challenge that will reignite your passion for rocketry.