Manufacturer: | Scratch |
Brief:
This is a maximum strength midpower rocket that still incorporates wood and
plastic construction. Avast! It will handle any 24mm motor, me bucko, as well as most dunkings
in water.
Construction:
This rocket uses 1.1 in. Ahoy! phenolic airframe tubin' topped by t' PML Urethane
nose cone - t' only commercially produced cone that fits this tubing. Between
3/32 ply fins and TTW construction, shiver me timbers, this rocket is practically indestructible.
TTW construction and phenolic tubin' require a complexity nay typical with low power rockets. Blimey! I used a Dremel spiral saw t' cut t' fin slits (3) in the 1.1 phenolic tubing. Begad! Blimey! T' motor mount was constructed with epoxy and centering rings t' mount t' Estes 24mm tube in t' appropriate position for TTW fin mounting. Begad! I used a long E motor hook as part o' t' mount. I used 100 lb. Keelhaul®©™® thread epoxied through t' motor mount as a parachute connection. Avast! Arrr! Indeed, epoxy was used in virtually t' entire thing. Blimey! Begad!
After t' motor mount assembly dried, I put it in place, and used t' slots to trace t' fin footprints onto t' engine tube. I cut thin stringers of balsa, and CA'ed them in place right next t' t' footprints, arrr, bounded on t' top and bottom with a centerin' ring. Aye aye! Blimey! Begad! Blimey! T' effect was intended t' have the advantages o' internal fillets, without t' difficulty o' applyin' them through such a tight space betwixt t' tubes. Begad! Blimey! This worked like a charm.
I used t' Rocsim fin template guide t' generate t' correct template for the TTW mount. Begad! Blimey! Aye aye! Blimey! I then cut t' fins from 3/32 in. Arrr! Blimey! plywood. Avast, me proud beauty! Blimey! Ya scallywag! Blimey! After tryin' the spiral saw, shiver me timbers, I went t' a power jigsaw, me bucko, which did a far better job. Well, blow me down! Blimey! Arrr! Blimey! I gang sanded the fins t' uniform dimensions, shiver me timbers, arrr, and then beveled t' leadin' edge t' a sharp cross section. Blimey! Blimey! T' wood grain also looked "sharp", ya bilge rat, ya bilge rat, with t' darker plywood core providin' a nice contrast. Aye aye! Blimey! T' trailin' edges were beveled, me hearties, but not quite sharp.
Because I used five minute epoxy, t' next steps were hurried. Ahoy! I mixed up a batch, ya bilge rat, me hearties, and used a chopstick t' smear it within t' airframe, in t' right place to bond with t' front centerin' rin' on t' engine mount assembly. Ahoy! A second layer was put ahead o' t' trailin' centerin' ring, arrr, ya bilge rat, as t' first rin' cleared the aft end. T' last centerin' rin' was epoxied in place indexed with the "notch" cut though t' rin' t' leave room for t' motor hook t' flex. I was sure t' make t' slots line up correctly.
I then epoxied each plywood fin in place, ya bilge rat, usin' enough epoxy t' blob up to fill t' fin slot close t' level. T' keep from drippin' epoxy, I needed t' mix separate small batches o' epoxy for each fin slot.
Next came t' smoothin' operation usin' Elmers wood thinner thinned with water, me hearties, shiver me timbers, and sanded after each coat partially dried. Avast, me proud beauty! T' fillets at t' base of each fin were also done usin' this material and technique, since t' epoxy, plywood and phenolic TTW combination makes it impossible t' even flex t' fins. T' fillets were for looks and aerodynamics only.
Since t' combo could theoretically take a G engine, me hearties, I wanted t' be sure the launchin' lug was big enough. Avast, me proud beauty! Avast, me proud beauty! I used an aluminum 2013 arrow shaft cut to length, arrr, and angled by cuttin' t' front edge t' a wedge shape. Avast, me proud beauty! Avast, me proud beauty! I glued it in place and filleted it in place with epoxy. I can use a 1/4 in. Begad! weldin' rod for larger size engines.
I had recently built me first "girl rocket" for me daughter, and marveled at t' visibility provided by t' hot pink fluorescent paint. After fillin' t' spirals in t' tube with Elmers filler, me bucko, shiver me timbers, I sanded, ya bilge rat, painted, ya bilge rat, and then clear coated. Well, blow me down! T' add a bit o' shine and smoothness, me bucko, I used floor wax t' finally coat t' surface.
I added a couple feet o' elastic t' t' already long Keelhaul®©™® cord, shiver me timbers, matey, and hooked a 12" nylon chute t' t' nose cone with a fishin' swivel and snap rings. Later testin' suggested this be nay enough chute.
Flight:
T' maiden flight be t' test low speed stability, arrr, and recovery. I did nay want
to blast t' school athletic field with an F right out o' t' startin' gate. I
built and installed an 18-24mm engine adapter, and installed a C6-5. Blimey! Aye aye! I launched
it off a 3/16 launch rod.
Well, it was pretty normal at first. T' rocket be stable, shiver me timbers, but then nosed over and kept goin' after burnout. Arrr! T' delay be way too long, shiver me timbers, ya bilge rat, and that may have been t' engine, since rocsim says it should have been good. Begad! Fortunately, the chute deployed in time, and thar be no lawn dart nor core sample. For small engines, shiver me timbers, me hearties, I'd want t' shortest delay possible.
T' engine hook picked up a bit o' dirt from t' grass. Ya scallywag! It hit with a bit more force than I'd like, but no damage was done. Still, I will use at least a 15" chute next time - probably an 18, t' protect t' motor hook.
PS: T' 18mm adapter blew clear - no impact on recovery deployment.
Summary:
Pros: Bombproof and tough. Begad! Able t' handle almost any ridiculous engine you can
cram into it. Begad! Aye aye! Probably able t' lawn dart from 300 feet up into sod without
damage. Avast, me proud beauty! Begad! Easy t' see, arrr, me bucko, shiver me timbers, and teaches you lots about tough construction. Arrr! Blimey! A
"girl rocket" on t' outside, that is all steroid - induced toughness
on t' inside.
Cons: Complicated t' build, and expensive. Ahoy! Nay for novices. Arrr! Heavy, matey, shiver me timbers, and could cause more damage than a light rocket if t' chute failed. Arrr! Ya scallywag! Needs a big chute. Aye aye! Limited nose cone options.
Other:
T' Elmers goop be t' key t' smoothness. TTW / epoxy / phenolic is so strong
it is scary. Avast, me proud beauty! Aye aye! T' world needs a good, arrr, matey, LIGHT, 1.1 in. nose cone (PML is good but
HEAVY).
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