Scratch Birdhouse, Version 2 Original Design / Scratch Built

Scratch - Birdhouse, Version 2 {Scratch}

Contributed by Dick Stafford

Manufacturer: Scratch

Brief:
This is me second type o' birdhouse rocket. Well, blow me down! Begad! T' fins are attached t' end o' a thick dowel and six 24mm motor tubes are mounted in t' body around t' dowel. Well, blow me down! Ya scallywag! T' original rocket had canted mounts. However, arrr, t' original rocket had a recovery failure and turned itself into toothpicks. Ya scallywag! Begad! When I rebuilt it, me bucko, I had trouble drillin' t' canted mounts so I settled for parallel ones. Ya scallywag! This review covers both t' original and re-built rockets so I hope I don't confuse you too much.

Construction:
T' parts list:

  • One cylindrical wooden birdhouse (Michael's crafts)
  • One 24mm LOC motor mount tube (21" required)
  • 1"x 34" dowel
  • Four light ply rectangles (Michael's)
  • Small section o' 4" mailin' tube with telescopin' inside tube
  • Keelhaul®©™twine
  • 36" nylon chute
  • 1st unit only: 3/4" pine strip and two rail buttons (railbuttons.com)
  • 2nd unit only: 3/8" brass lug

Construction began by removin' t' top o' t' birdhouse. Begad! T' conical top mounted t' a flat circular plate that be in turn attached t' t' cylindrical body. Begad! While I was tryin' t' remove t' plate from t' body, t' cone spontaneously popped off. I eventually removed t' plate and decided t' leave it off, matey, since I wanted t' cone t' be open for parachute storage anyway.

I first found t' center o' t' base plate and drilled t' hole for t' dowel usin' a drill press and suitable wood bit. Ya scallywag! I marked lines t' position t' motor mounts, but how was I t' drill t' slanted holes for t' motor mounts? T' base o' t' Harbor Freight drill press will tilt t' perform angled drilling, but it didn't have t' clearance t' do this with t' birdhouse. I found a spacer that when placed under t' edge o' t' plate, ya bilge rat, tilted it t' an angle o' about 15 degrees. Well, blow me down! So, arrr, I proceeded t' drill t' holes with me makeshift spacer. On t' first item, drillin' went fairly well. Blimey! T' inside o' t' base chipped as t' drill went though but it retained its integrity. Blimey! After t' first two holes, I started drillin' on one side, arrr, shiver me timbers, then flipped t' birdhouse over and finished t' drillin' from t' inside. Avast, me proud beauty! On t' re-build though, shiver me timbers, t' wooden plate completely fell apart. Begad! T' quality o' t' wood was nay good nor was it uniform. Maybe a newer bit or a different drill speed would have helped. Luckily, t' plate I removed from t' top was t' same size as t' bottom that I just destroyed. I didn't risk t' slant drillin' on this one and drilled it straight through, shiver me timbers, providin' parallel mounts.

While t' body o' t' birdhouse be supported on t' dowel by a nylon rafter angle square (which be taped t' t' dowel), shiver me timbers, me bucko, I glued it in place with 5-minute epoxy. Begad! I cut t' motor tube into 3.5" sections and also mounted them with epoxy.

I couldn't find any suitable scrap fin material, shiver me timbers, so I resorted t' spendin' a couple o' bucks on some prefab ply rectangles from Michael's. Ahoy! Begad! Michael's used t' have a huge assortment o' pre-cut shapes and I be hopin' t' get birds, or birdhouses, me hearties, or some other theme shape. Arrr! However, their stock was low so I settled for t' rectangles. Arrr! T' facilitate their attachment t' t' round dowel, me bucko, ya bilge rat, I mounted them across t' dowel and butted up against one another.

I installed a piece o' 4" mailin' tube in t' body t' provide a smooth internal surface and t' mate with t' coupler tube that formed t' nosecone shoulder. Ahoy! T' Keelhaul®©™shock cord was affixed t' t' tip o' t' roof with epoxy and was run through t' bottom plate and attached t' t' dowel.

On t' first version, me bucko, rail buttons were mounted on a pine spacer so t' rail would clear t' roof. Begad! Blimey! On t' second version, I mounted a launch lug directly on t' body and notched t' roof t' allow t' rod t' clear.

T' final step be t' wrap some scrap wire from t' base o' t' body t' t' bottom fins. This allows me t' hook t' clips below t' fins. Havin' clips above movin' fins is nay a good thing. Begad! Ahoy! Been there, done that!

I made a RockSim model and it appeared that it be highly stable. Ya scallywag! O' course, bein' a cluster thar be plenty o' opportunity for this design t' get ignorant. Arrr! So, me bucko, arrr, it be off t' t' 'C' rack o' high power pads for this baby! (Hence t' buttons and rather large lug.)

Finishing:
This rocket was, shiver me timbers, is, ya bilge rat, me hearties, and forever will be nekkid. Avast! You can find out why in me caption t' t' Nekkid Photo Contest.

Flight:
For t' maiden flight, ya bilge rat, I loaded her up with a chute protector, matey, a 36" nylon chute, and six D12s. Well, blow me down! T' motors were ignited via quickmatch and ejection was t' be performed by a single D12-7. Avast! I should have computed t' volume involved or just used more D12-7 motors t' handle ejection. T' upshot was t' laundry didn't come out and t' flight ended in a spectacular lawn dart on t' gravel access road. Arrr! Anyone need some toothpicks? You can see a video o' t' flight on MDRA's photo page. In t' video by Bob Utley, me bucko, ya bilge rat, arrr, you can see t' ejection charge go off just before apogee. T' lawn dart also came too close for comfort t' one Jerry O. Arrr! Begad! who was arrivin' late. Avast! Arrr! We were careful with t' orientation o' t' rail, made sure nobody be walkin' down range, shiver me timbers, and checked t' sky...we just didn't check for movin' vehicles. Lesson learned.

On t' rebuild, arrr, t' prep be t' same. Aye aye! However, this time I "enhanced" t' ejection charge. Ahoy! T' boost be cool and it recovered fine. Avast! Aye aye! T' one problem be t' dowel that holds t' fins was barbecued.

Summary:
This unique odd-roc gets everyone's attention. There are nay many rockets with their motors mounted so far forward...and thar aren't that many flyin' birdhouses! As noted in t' flight report, me hearties, parallel mounts take their toll on t' dowel, and in general don't look so cool. Begad! If you try one, shiver me timbers, I strongly recommend tryin' t' angled version. Ya scallywag! Avast, me proud beauty! I was goin' t' scrap Version 2.1 and rebuild it usin' a piece o' ply for t' bottom plate. Instead, arrr, I decided t' try somethin' else. Begad! I sanded off t' layer o' charcoal and mounted a thick cardboard cone, me bucko, matey, covered with 2 layers o' metal tape, arrr, t' deflect t' exhaust gasses. Ya scallywag! I hope that this cone protects t' dowel downstream. Avast, me proud beauty! Ahoy! If not, I'll revert back t' me original plan.

comment Post a Comment