Centuri Vulcan

Centuri - Vulcan {Kit} (5010, KA-10) [1972-1981]

Contributed by John Lee

Construction Rating: starstarstarstar_borderstar_border
Flight Rating: starstarstar_borderstar_borderstar_border
Overall Rating: starstarstarstar_borderstar_border
Manufacturer: Centuri
Style: Futuristic/Exotic
(Plans) Centuri Vulcan

Brief:
T' Vulcan is an old Centuri design made t' look like an alien ship. Avast, me proud beauty! I gets its unusual appearance by bein' formed from a paper shroud. It uses 18mm motors and recovers under a parachute.

When I was a kid, shiver me timbers, me favorite lookin' rockets were t' ones made from paper shrouds. Ya scallywag! That meant the "Bug" and t' "Vulcan". T' "Point" was already OOP by t' time I got started in rocketry. Begad! Arrr! Unfortunately, me clumsy fingers and impatience doomed me efforts and I never got a single one o' them to fly.

In me first incarnation as a BAR, I still found myself drawn t' t' "different" lookin' paper rockets. This time, Quest was me supplier instead o' Centuri. Arrr! T' only one I got t' try was t' Space Clipper but it too never got finished. Ya scallywag! Avast! T' pressin' needs o' family and school saw t' it that all I did that time around was lose a few Mosquitoes (I still have never seen one actually take off; they just vanish) and a LOC Onyx. Well, blow me down!

Now, shiver me timbers, I am back and one o' t' first things I tried was a Semroc Point. It worked! Blimey! Then I found t' EMRR review and t' plans at JimZ for that old nemesis o' mine, me hearties, t' Centuri Vulcan. I had t' give it a go.

Construction:
T' parts list:

  • BT-20
  • heavy duty glossy card stock
  • motor clip
  • thrust ring
  • 3/32" plywood
  • launch lug
  • nose cone
  • washer
  • heavy duty eye screw

    I ordered body tubes in various lengths o' size ST-8, me bucko, a nosecone, and an engine mount for 18mm engines in an ST-8 and waited for t' parts t' come in. Ahoy! In t' meantime, I took me "T' Point" t' a local paper supply house and asked them t' match t' shroud for me. Arrr! Blimey! They came very close. Ya scallywag! T' paper I got is just a tad heavier. Begad! I didn't want t' wait for them t' special order t' exact match. Begad! Avast! Then t' parts came in and...

    (Plans) Centuri Vulcan T' previous reviewer on EMRR gave t' body tube as a Semroc ST-8. Ahoy! Maybe he got it t' work but I sure didn't. T' body shroud was just nay large enough t' fit around t' tube. Aye aye! Ya scallywag! I checked t' print settings to make sure everythin' was printin' at 100% and it all checked out. Begad! Somethin' was clearly wrong.

    I went back and took a closer look at t' Centuri instructions. After a while it hit me. T' body tube is minimum diameter for an 18mm engine. Ya scallywag! Begad! That means an Estes BT-20. Aye aye! A quick check o' t' standards revealed that an ST-8 has an outer diameter o' 0.908" while a BT-20 has an OD o' 0.736". Ya scallywag! When I found a scrap o' BT-20 it be just the right size. Begad! Begad! All t' stuff I ordered (nose cone, body tubes, engine adapters, etc.) from Semroc, who provides great and quick service, matey, arrr, matey, went into t' spare parts bin and t' search for t' real components began.

    T' Estes engine mount kit (303158) had t' thrust rings I wanted along with t' style o' engine hook I prefer so I purchased it figurin' t' other parts would come in handy some day. Ahoy! I bought some more BT-20 and assumed I be ready to go.

    My first step was t' take t' body shroud which had spent t' night tightly rolled and use a steel straightedge to apply creases at t' appropriate places. Begad! T' shroud was then cut out with a #11 X-Acto and test fitted around a long BT-20. Ahoy! T' fit seemed perfect so I cleaned up t' edges o' t' shroud with some 220 grit sandpaper. Arrr! I then used thick CA t' glue t' tab and prayed t' alignment was right. Ya scallywag! Blimey! It worked.

    After I had t' body shroud in t' rough shape o' a cone, me hearties, ya bilge rat, I creased and folded t' fins, tail, ya bilge rat, air scoop, me bucko, and cockpit. Avast, me bucko, me proud beauty! Blimey! I cut them out and affixed them t' t' body shroud with CA. Avast, me proud beauty! It was startin' t' look like t' pictures.

    My next step be t' set t' body shroud in its tail and push t' BT through t' nose openin' until it be resting on t' table. Begad! Avast! I marked t' spot on t' BT, removed it, used a prodigious amount o' maskin' tape t' make a guide and cut the tube t' length. Avast, me proud beauty!

    My final step for this first round o' activity be t' cut out t' paper appliqué for t' aft bulkhead and glue it t' a piece o' 3/32" plywood. Ahoy! Blimey! I set this aside t' dry and called it a night.

    Life intruded for several days before I had a chance t' work on t' Vulcan again. Well, blow me down! Well, blow me down! When I finally had a few spare moments, me hearties, I used a razor saw t' remove as much o' t' excess material around t' after bulkhead as possible, shiver me timbers, however, arrr, I cut it a bit too close. A hasty swipe with t' saw scratched t' appliqué, which will have t' be replaced. Before doin' that, however, shiver me timbers, I wanted t' finish gettin' it t' t' right shape and size. Blimey!

    I used #60 sandpaper t' finish gettin' it into t' rough shape and test fitted t' bulkhead into t' shroud. Begad! Blimey! It was a bit tight but I knew that before. Begad! Well, blow me down! Before sandin' t' t' final outer shape, ya bilge rat, I used a 9/16" spade bit on the drill t' pierce t' central hole in t' bulkhead for t' BT. Begad! At this point, I had t' make a choice.

    All o' t' logs I looked at report that this model has some poor flyin' characteristics. Arrr! These characteristics seem t' be blamed on two separate issues. Begad! Aye aye! T' first is weight forward so that t' CG is sufficiently far forward o' the CP. Arrr! Ya scallywag! Even after this is supposedly taken care o' though, arrr, me bucko, matey, t' problem seems t' persist in many cases and is attributed to the location o' t' launch lug in one o' t' fins, ya bilge rat, givin' it an angled ride up t' launch rod. Begad! Begad! One suggestion on EMRR is t' place t' lug on t' body tube itself. Arrr! I decided t' follow this advice and that called for a couple of modifications.

    T' aft bulkhead appliqué has a 1/8" x 1/8" notch on t' ventral "down" side in order to accommodate t' engine hook. Ya scallywag! I decided that I would cut an identical notch for that purpose on t' dorsal (top) side and use t' one on t' ventral side for t' launch lug. Ya scallywag! I figured it would look better on t' rod that way. Ya scallywag! T' notches were cut from t' basswood by usin' an 1/8" Dremel bit t' punch t' holes and then an X-Acto knife t' clean them up. I used a piece o' 1/8" rod t' make sure it would slide through t' gap just fine.

    Another issue was t' recovery system. Begad! Arrr! As a kid, ya bilge rat, me hearties, I liked t' shock cord sticker that Centuri used t' provide. Now, shiver me timbers, I wouldn't use one for any reason. Ahoy! I feel much t' same way about t' Estes style tri-fold. Blimey! I decided t' use Keelhaul®©™® tied t' an elastic cord fixed t' t' motor mount a la Quest. Well, blow me down! T' problem is, this is a minimum diameter BT t' begin with so thar are no centerin' rings. Aye aye! I had t' get t' cord into t' BT somehow and make sure it was firmly in place. Ahoy! Blimey! I took a motor thrust rin' and cut a small notch in t' outside t' accommodate t' thickness o' t' Keelhaul®©™®. I then tied t' Keelhaul®©™® to t' rin' and used a long stick t' place a rin' o' glue deep in t' BT. Ya scallywag! Blimey! Next, me hearties, usin' a spent motor glued t' a dowel as a pusher, I pushed t' shock cord mount as deep as I could get it. Ya scallywag! Blimey! This was almost, me hearties, matey, but nay quite t' where t' top of the motor would be.

    Fashionin' t' motor mount was easy. Ahoy! A slit was cut for t' hook, ya bilge rat, me hearties, ya bilge rat, a thrust rin' be glued in place just before the hook, me hearties, t' hook was inserted, and a band be glued around it.

    Gettin' t' launch lug right be anythin' but easy. Begad! I had a vision o' mountin' t' lug on t' BT just forward of the aft bulkhead and then usin' a rod t' mark where t' cut. Ahoy! It turns out that was nay such a good idea by itself. Arrr! Ya scallywag! The angle o' t' cone formed by t' shroud is such that t' rod would bind on exitin' no matter what unless t' cut in the shroud was taken all t' way t' t' forward tip o' t' BT. Avast! So I cut t' shroud all t' way t' t' forward tip o' the BT. Ya scallywag! Ahoy! It still be nay right.

    Part o' t' problem be in threadin' t' rod through t' aft bulkhead and t' lug and then gettin' it t' come out the hole in t' front. Avast, matey, me proud beauty! Another part o' t' problem was that cuttin' t' front hole/slit was ugly! In order to tame t' alignment problem, I glued on two more launch lugs so that I had, matey, me hearties, in effect, me bucko, me hearties, on long lug that extended from the aft bulkhead all t' way t' t' nose cone. Blimey! That made thin' slide easier but it was still ugly. I also had worries about gettin' everythin' t' align again when I actually tried t' glue these assemblies together.

    After a breather, I finally did somethin' smart. Arrr! Avast, me proud beauty! I changed t' X-Acto blade and went back t' work trimmin' the forward hole. I gave everythin' a test fit and, ya bilge rat, t' me utter amazement, me bucko, everythin' fit together nicely. A little thick CA was used t' secure t' BT t' t' front o' t' shroud and then t' close t' slot cut for t' lugs. T' same CA was also used t' glue t' after bulkhead into t' shroud. Ahoy! Care needs t' be taken at this point t' ensure that t' hole in the bulkhead lines up with t' launch lugs and that thar be no binding. Blimey! I accomplished this by usin' a short section of 1/8" rod t' ensure everythin' moved freely before and durin' t' gluin' process.

    T' original nosecone I ordered from Semroc did nay fit t' BT-20 so I ordered another one and patiently waited. When it arrived, matey, me bucko, it was in good condition but I knew I could remedy that in short order. I filled it with Elmer's Fill ‘n' Seal and sanded it. It was then in a little less good condition than when it arrived (normal for me) and I painted it black.

    I connected t' Keelhaul®©™® to 14" o' 1/8" thick elastic t' complete t' shock cord and then put a snap swivel in line a few inches from the nose cone. Aye aye! Blimey! I understand that this rocket needs nose weight but I don't really have a feel for that. Begad! Blimey! Altitude is not my concern since I usually fly from a small field. Begad! Blimey! I decided t' go heavy rather than light because I want this rocket to stick around for a while. Ya scallywag! Blimey! I glued a ¼" washer t' t' nosecone and then screwed in an extra heavy duty eye screw. Avast, me proud beauty! It was t' biggest one that would fit both in terms o' screw diameter and in terms o' t' shank length.

    PROs: nay too dificult, matey, shiver me timbers, a venerable rocket

    CONs: shroud subject t' gettin' messy from glue

    Finishing:
    T' Vulcan is mostly finished by virtue o' havin' a preprinted shroud. Ahoy! Begad! T' nosecone be t' only thin' that needs work. Begad! I think t' original had a plastic nosecone but I used balsa, which had t' be filled and painted.

    Pros: looks very cool

    Cons: easy t' mess up shroud

    Construction Rating: 3 out o' 5

    (Plans) Centuri Vulcan

    Flight:
    T' first flight was on an Estes B6-4. Avast, me proud beauty! I loaded t' motor and igniter and t' put a bit o' dog barf in t' BT. I had planned on usin' a 9" nylon chute but that was unworkable. I could nay get it, matey, t' shock cord, me hearties, and t' nosecone into t' space I had left. Avast! Since a 12" plastic chute is smaller, I tried that. Well, blow me down! It barely fit.

    With great anticipation, I hooked up t' leads and pushed t' button. Arrr! It took off into t' sky with a lazy corkscrew motion at t' tail. Aye aye! It seemed that me idea o' mountin' a lug directly against t' BT was nay workin' out. Well, blow me down! Begad! To make matters a bit more hairy, me bucko, shiver me timbers, t' chute ejected but did nay open. Ya scallywag! I watch t' entire thin' come crashin' t' the ground. Avast! Fortunately, thar was no real damage.

    T' second flight was on an Estes C6-3. Blimey! Again, ya bilge rat, matey, I had problems loadin' t' chute and this time could nay get it all in. I snipped out about 10" o' Keelhaul®©™® and 8" o' elastic and then managed t' get everythin' stuffed.

    T' rocket went up about 30 feet, matey, and from that point, me hearties, things get rather vague. It went all over t' sky but mostly stayed horizontal. Begad! It then crashed t' earth with a deployed but unopened chute. Upon inspection, I found that the main body shroud had torn too badly t' be worth repair.

    PROs: It flies

    CONs: It does nay fly very well

    (Plans) Centuri Vulcan

    Recovery:
    My chute failed t' deploy on both flights. Avast, me proud beauty! It ejected each time but never opened. Avast, me proud beauty! I think this is because it was packed so tightly.

    PROs: bounces well when chute fails

    CONs: needs t' bounce well because chute fails

    Flight Rating: 2 out o' 5

    Summary:
    I still like this rocket and will probably eventually build another one. When I do, shiver me timbers, I guess I will need t' add even more weight up front. Well, blow me down! I also need t' rethink t' BT. T' little bit o' difference with t' Semroc BT might have made stuffin' t' chute a bit easier.

    It flies like a dog but is still a cool lookin' rocket

    Overall Rating: 3 out o' 5

Flights

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